EVENT GE!WRATOR FOR REIIC

SPIN PHYSICS

March 15-19, 1999

Organizers

Naohito Saito and Andreas Schaefer

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RIKE3VIBNl_ Research CenterBuilding 510, Brookhaven National Laboratory, Upton, NY 11973, USA

Other RIKEN BNL Research Center Proceedings Volumes:

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Voiume i 5-

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Volume 9-

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v~]l~~~ ~ -

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Hard Parton Physics in High-Energy Nuclear Collisions - BNL-

RIKEN Winter School — Structure of Hadrons —Introduction to QCD Hard~ . . . . . . ..— RNTT K9KG(IL LWtJGkJOGL3 ULIU-UJ2UUGJ .

,-, -- n,quu rnase Transitions - i3NL-52561

,

Quantum Fields In and Out of Equilibrium - BNL-52560

Physics of the 1 l’eraflop RIKEN-BNL-Columbia QCD Projectn;-.+ Amn;.rn-.omr Pnlahvo+; nm RTUT-AA900L LLCIULUUIJVGLLW,LJ UGAGUICA. ULUAJ ‘- UJ. lU-WU&dd

Quarkonium Production in Relativistic Nuciear Collisions - 13NL-ozasY..-...-

Event Generator for RHIC Spin Physics - BNL-66116

Physics of Polarimetry at RHIC - BNL-65926

High Density Matter in AGS, SPS and RHIC Collisions - BNL-65762

Fermion Frontiers in Vector Lattice Gauge Theories - BNL-65634

RHIC Spin Physics - BNL-65615

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Perturbative QCD as a Probe of Hadron Structure - BNL-64723

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,

Preface to the Series.

The RIKEN BNL Research Center was establishedthis April at Brookhaven National Labo-ratory. It is funded by the “Rikagaku Kenkysho” (Instituteof Physical and Chemical Research)of Japan. The Center is dedicated to the studyof strong interactions,including hard QCD/spinphysics, lattice QCD and RHIC physics through nurturing of a new generation of young physicists.

For the first year, the Center will have only a Theory Group, with an Experimental Group tobe structured later. The Theory Group will consist of about 12-15 Postdocs and Fellows, and plansto have an active Visiting Scientist program. A 0.6 teraflop parallel processor will be completed atthe Center by the end of this year. In additicm, the Center organizes workshops centered on specificproblems in strong interactions.

Each workshop speaker is encouraged. to select a few of the most important transparenciesfrom his or her presentation, accompanied by a page of explanation. This material is collected atthe end of the workshop by the organizer to form a proceedings, which can therefore be availablewithin a short time.

T.D. LeeJuly 4, 1997

.

.

.

CONTENTS

Preface to the Series. . . . . . . . . . . . . . . . . !.. . . . . . . .

IntroductionN. Saitoand A. Schtifer . . . . . . . . . . . . . . .

Needs of Event Generator for RHIC Spin PhysicsN. Saito . . . . . . . . . . . . . . . . . . . . . . .

Recent Progress in theoretical Studies of Spin PhysicsA. Schafer . . . . . .

New Processes and ParityJ.-M. Vzrey . . . . .

k~ Issuesill. J. Tannenbaum . .

Quarkonium ProductionsT.-A. Shibata . . . .

. . . . .

Violating. . . . .

. . . . .

. . . . .

Event Generators at Fixed Order inS. Fkixone . . . . . . . . . . .

. . . . . . . . . .

Asymmetries. . . . . . . . . . .

. . . . . . . . . . .

. . . . . . . . . . .

. .

. .

. .

. .

. .

. .

. .

QCD: Jets and Isolated. . . . . . . . . . . . .

. .

. .

. .

. .

. .

. .

. . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . .

. . . . .

Photons. . . . . . . .

Comparisons Between Sphinx, Pythia~-Asymmetries and LO/NLO QCDO. Martin . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Problems with and Alternatives to Prompt Photon ProductionL. E. Gordon . . . . . . . . . . . . . . . . . . . . . . . . . . .

Unpolarized Parton Distributions: Current Status and Open IssuesW.-K. Tang . . . . . . . . . . . . . . . . . . . . . . . . . . .

Parametrization of Polarized Parton Distributions in the NucleonM. Hiram . . . . . . . .

Semi-Exclusive Reactions inM. Maul . . . . . . . .

Higher-Order ContributionsL. Bland . . . . . . . .

List of Participants. . . . . . . . . . .

Workshop Agenda. . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .

pp Collisions. . . . . . . . . . . . . . . . . . . .

to Prompt Photon Production. . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .

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i

ii

1

7

13

19

25

31

37

44

50

55

60

67

73

76

INTRODUCTION

●

●

This volume archives the reports from the RIKEN BNL Research Centerworkshop on “Event Generator fo:r RHIC Spin Physics II” held during theweek March 15, 1999 at Brookhaven National Laboratory. It was the second

meeting on the subject following a first one in last September.This workshop has been initiated to establish a firm collaboration between

theorists and experimentalists involved in RHIC spin physics with the aim ofdeveloping a reliable, high-precision event generator for RHIC spin physics.Needless to say, adequate event generators are indispensable tools for high

energy physics programs in general, especially in the process of:

● planning the experimental programs,

● developing algorithms to extract the physics signals of interest,

● estimating the background in the extracted results, and

● connecting the final particle kinematics to the fundamental i.e. partonic

level processes.

Since RHIC is the first polarized collider. dedicated efforts are required toobtain a full-fledged event generator which describes spin dependent reactionsin great detail.

The RHIC spin project will be in the transition from R&D and construc-tion phase to operation phase in the year 2000. As soon as data will beavailable, it should be analysed, interpreted and compared with theoreticalpredictions to extract its physical significance. Without mutual understand-ing between theorists and experimentalists on the technical details, it is hardto perform detailed comparisons in a consistent framework. The importanceof this fact has been recognized especially during the analyses of hadron in-duced reactions observed at CER!X, Fern-dab and DESY. Since the use ofevent generator is indispensable for the analyses, it should be developed in away that both experimentalists and theorists can agree upon.

During the first meeting we had specified several areas of work to bedone. For most of them some actual calculations are well under way andfirst progress was reported. These areas of work include:

.

ii

● comparison of polarized event generators with results obtained by using

unpolarized event generators and suitable asymmetry weights

● comparison of event generator with next-to-leading order calculations

● implementation of new processes, e.g. parity violating processes

● implementation of new polarized parton distributions and their contin-

ued maintenance

● polarization effects in fragmentation processes

Jve believe that the records oft he discussions in these various areas, as com-

bined in these proceedings, will prove to be useful not only for the participantsbut also for other physicists involved in this field.

Naohito Saito and .4ndreas Schafer are grateful to all participants of theworkshop for their contributions on the various theoretical and experimentalissues to be clarified by our collaboration. We would like to express our sin-cere thanks to the secretary of RIKEN BNL Research Center, Pam Esposito,

for her great help in organizing and running the workshop. Our workshopwas celebrated by a big snow storm on the first day. Without the kind and

devoted help by Pam and Eva Esposito, we would therefore not have beenable to carry out the workshop as planned. We want to extend our gratitudeto Brookhaven Nations] Laboratory and to the U.S. Department of Energy

for providing the facilities to hold this workshop.

>“aohito Saito (RIKE.N / RIKEN BNL Research Center)

.$ndreas Schafer (Universitat Regensburg)

RIKEN BNL Research CenterApril, 1999

●

●

iii

Needs of Event Generator for RHIC Spin Physics

Naohito Saito

Radiation L.aborato~

RIKEN (The [nstitule-for Physical and Chemical Research)

Hirosawa, Wake, Saitama 351-0198, Japan

and

RIKEN BNL Research Center

Brookhaven National Laboratory

Upton, NY11973-5000, USA

The event generator is a irreducible part of the high energy particle and nuclear physics.

This is especially true when one tries to extract partonic level information in QCD

events. The et%ciency of the experimental cut for the signal and remaining backgrounds

are usually estimated with event generators. Since RHIC is a unique machine for both

heavy ion and polarized proton beams, special extension of the event generator is

necessary.

In this talk, we addressed the needs of more detailed analysis of previous

experiments on key reactions, especially prompt photon production, since most of

theory calculations underestimate the cross section. To obtain a reasonable agreement,

inclusion of intrinsic transverse momentum (k~) is desirable. We also addressed the

importance of direct measurement of k~. This kind of analysis have to be extended to

cover W production, Drell-Yan production of lepton pairs, open heavy flavor

productions, and finally new processes such as compositeness search and so on.

There are many things to do to come to complete understanding of the reactions in

hadron collisions. But we should hurry up, since we are going to take real data soon!

1

Needs of Event Generatorfbtn experimentali6t’5 viewpoint

● Experimentalist5 can touch only Initial and Final

5tate patiicle5– par-tanemi55ion f~,A(x) A— initial et.ate radiation

– hard 5cattering [ma,y include new phy5ic5) A7dt

– final 5tate radiation x

– fragmentation D06(2jd . .

B– decay– undedying event

● Experimen~ali5~5 often aim fa,A(x),6icI/dt, DCJZ)to———

find new phy5ic55en5iti”vi~ for new phy5ic5 / background 5tudie5

geometrical acceptance for F5P5 from physic5 of intere5ts

5y5temati”c uncertainties in interpretation of re5ult5

5ummary of the Laat Meeting

c Polarized EvGen VGUnpolarized EvGen+A~ymmet~— Qui~k 5tudie5 showed 5imilarity. What F’reci5ion?

● Event Generator v~ analytic cakulatim (NLO,— Detailed compariwn may 5how 5ome diqcrepan~y

● Libraty of PoI-PDF in addition to Unpol-PDF

Ke5ummation)

— interface needed for 1) prediction 2) quick te5t of obtained PDF5

c Intringic Tranwer~e Momentum of Patiorw— could be large at I?HIC --> 5ma11-x data become “u5ele55” if unknown

● New Proce55e5– parity violation in jet production --> parity violation in Z“%?— Quarkonium production: popular color octet model with spin dependence

● Polarization Effeck in Fragmentation– 2 pion correlation in final 5tate

● Comparison of PYI-HIA, HEKWIG and ISAJET

2

.

●

Pmtonic Kinernaticg - LO V5 NLOprompt photon example

p==x#photon

c5imple minded reconstruction of P:y;: p=xP P

quark $

partonic kinematic5r

~,:g uon

‘i! k

=~p :;>/

~~ CM5 = parton CM5 quark-jet~=q A

●/hat i5 x carried by glum?{PT=P

X=XT? No!~=x I

——

better estimation?

● What i5 Q2 ?●Q23@

●Q2+#) 2?

●Q&(z pT) z?

@

EvGen and Kewmmed XgectionW production

● 5ignal = High-~~ Iepton --> affected bypTw

3

Unpolarized parton distribution

0.05

0

-0.05

4.1

4.15

-0.2

k CDF 1992-1995 (110 pb-l e+~) I

L_...:.”]...

0 0.5 1 1.5 2Upton Rapidity

Unpolarized pa-ton distributionflavor etructure of gea-quark

c Charge 5ymmetty ig a FNAL-E866 re5ult5

good qymmetty to PRL 80 (1995) 3715

dem-ibe hadron 2.2

propertied: (u in p and d z~ -+NA51 CTEQ4.M

in n are different??: C. 1.8

Oorog, J,T. Londergan, A. 1.6 ++{~~

lq La ~ThomaWKL 51 (1995) ~ ‘Tl-

4075)~ i.2:

1

‘1

T

● It ~ not trivial to a55ume: ().8

dlz=l 0.6 ~

,1,CI.4 ‘ ‘ I 1 1 1, 1 1! 1 ,1, i, !,,,,,,,,,

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35x

Parity Violation 13eyond 5MP. Taxil, J.M. Virey PLF3364(1995)151-187

Win Jet Production due to quark Compogitenegs (gcale:A)

+ should be reflected to gingle particle production

60 80 100 :20

Fr (k_J/C)

0.1

0.05

A

0

I 1

-“”’u60 80 100 120

P, (Gev/c)

Chmmonium Production

Agymmetry Prediction

with Color Octet Model

0“’4F—’----------- ‘-7o.1, ~ ALL — MC 200 GcV 320 pb-1

I -------- FW2C 500 GCV 800 pb.10.1 ~ I I

I I0.06 I

0.04 i

r-----------------

‘7

/+---’ j ; ,,,.;

0.02 I-+.........*.---””’”””-“’””’”’””!.-.’.- ‘~....--...--.’0.0.02;

t ‘O:CT,,V,,,dATubldx IMJ156[$7:I.’3? 1.0.04 ~ ‘-”-””””””-””-”””j”

, .—.2 4 6 8 10 12 14

PT(G eV)

Yield Ee$imation with Color Octet

Model by Naoki,u5ing COM in PYTHIA (hep-ph/9706270)

k,=‘x :‘- 10.f

3,, ‘

>

G,0 ‘1’,0‘1

See D. Khaneev’5 tran5parencie5 at Spin Di5cu55ion at

http://rikweb.rhic. bnl.gov/r5c/writi-up/Khaneev/khameevl.html

5

5pin Dependent Fragmentation

to meawre AM(x)KL Jaffe, Xuemin Jin, Jian Tang hep-ph/9807560

s Asymmetry ALL= AT~ @o~ 63AT@

P~P~ + n+n-.x “’”~

,,,

‘~ 025

4~=o.o

5offer’5; 0.20 ~

E inequality%0,157A 200 GeV,~ “ “(?3 / a55umed to/

0.10 be 5aturated[ /“

0.05 - ,’/

0.00 1. L.. ,0 20 40 60 80 ]00 120

p~et(GeV)

—

5ummary

Many effort5 to be ready for RHiC Spin Phygim

– theo~, experiment, and accelerator

Event Generator for polarized pp 5hould be ready formany rea50n5

Thi~ meeting:

- progre55 report

– further 5tep5 to be di5cu55ed

6

Recent Progress in Theoretical Studies of

Spin PhysicsAndreas Schafer (Regensburg)

I review a few results from recent papers which focuss on RHIC spin

physics. However, many of the authors participate in the workshop and I

avoid overlap with their talks. Instead, I focuss on a few topics which arerelevant for RSC but are either not yet well understood or a slightly periph-

eral to the main interest of RSC.1.) The lack of a firm theoretical prediction for the small z asymptotic

behaviour of gl (x) limits strongly the relevance of DIS data because themost interesting QCD predictions address sum rules. Recently an interestingproposition was made by Kwiecinski et al., the problems and merits of whichare shortly outlined.2.) Higher-twist effects can be studied especially well in spin physics. Fur-

thermore the size of single-spin asymmetries suggest that they are large. Iargue that nuclear effects for higher twist effects can be large and cite somework by Guo et al. on this subject. If pQCD at smallish Q2 would break

down this would affect most seriously the whole field of high-energy heavy-ion physics. I argue that it in this context it is interesting to study singlespin asymmetries in p(pol.)+A.3.) I review the situation of orbital angular momentum distributions forquarks and gluons in the nucleon. I suggest that the production ratios for

different cZ-Mesons in the collision of polarized protons might provide a wayto access the gluon orbital angular momentum distribution directly.4.) I review recent developments for Off-Forward-Parton-Distributions and

pose the question whether they could be investigated at RHIC.

9

Q

-t

‘P

.

.

10

‘}

.

.

0.01_ 0.0‘q -0.01

I

L-/-......\i:..:’..:... .. .. . . . . . . . . . ..,‘\ . .

‘\\ . . . r,‘\ .-.‘.\\\\ ‘\.._/ 1

\ \ \ \ /=—.’

V-..,..............

‘\’\ /./.,‘\ ., ,./’‘\

\ ‘\ ‘ ,,\ ,“‘/;‘\

\ ..-.

1 ‘~, “’’’’’...,,’,,jf\ .-/’\

\\

/1\ //)s+

lo-~~ 5 10-12 5

x

r...,/.//’/ / ‘/ // #/ ,,./

/,;’------f-f//’

47’

/’

,

GRSV gmax

J/:

/?’.\ //,’‘.\

\

/

/[~)/tx\~\\ / i\.\ \\_ // / .1\\\ ,/ /‘\.‘\ /’ :

\d~)

,,\, /’

,..-.’

2 510-1251

x

0.0

-0.8

I

Figure 2: E\-oiution of orbital angular momentum. The GRSV LOgmax scenariois used as inpllt for the polarized parton distributions at u; = 0.23 GeV2. At thisscale <“~&W1.e&.Wf. QKL3LWS&M.lx&MllM.-amoungLQ(z. p;) and LO(Z.~2)~ which are assumed to have the same shape as UV(Z,p:)

.

and g(z. p;). respectively.

12

IYelv Processes ancl Paritlj’ Violating Asymmetries

tJean-Marc Virey’Institutfiir Physik

~Jniversitat Dortmund

D-4422!I Dortmund, Germany

\l;e have presented the apparent sensitivity of the RHIC Spin experiment to somenew phy-sic contributions, from the analysis of the Parity Violating (PV) asymmetryA~~(= da-- – do-;+ /da-- + da++) defined for jet production (da ~ dal-~.:). Since theexperiment will be,gin next year, ~ve gleatly emphasize the need of detained simulationsat the level of Monte Carlo Event Generators.

In the first part, after a brief review on the theoretical motivations for the presence ofsome new quark-quark Contact Interactions ((l) and of a light leptophobic Z’ boson, wehave presented the sensitivity of the RHIC to these models, using conventional experimen-tal parameters for polarized proton--proton collisions. It appears that the RHIC, on onehand, is able to cover some regions in the parameter space of the different models whichare unconstrained by present experiments, and also by the expectations of forthcoming’s( e.g. Tevatron RunL II). On the other hand, the RHIC is a unique facility to obtain crucialinformat.ions on the chiral structure of the nmv interaction. It is important to note thatthe integrated luminosity is a key parameter for this polarized analysis.

Tlie second part was devotecl to an “enlphasis of the neecl of simulations from event

generators. in order to take into account carefully the experimental conditions and theproperties of the cletectors. Some opened questions which have to be clarified by suchsimulations are, for instance : What are the true acceptances and efficiencies for jet recon-struct. iou needed to determine the actual effective integrated luminosity “? Is it possibleto use siuglc particle production. on one Ilaud, for an easier treatment within detectors.or OL1t he other hand, to reduce the backgrounds of the gluon’s subproct=sses “? LVhat aretllc Lnagllitudes of the systematic crro~s on A!},’ ?

‘Illc last section concerned tlic pot clltialil iw for new’ physics of tile RHIC’ wit}) polar-ized ]lclltrons+ if. if tile option of polarizc(l [1[’] is scriousl>. envisaged. In the framelvorl;

of I) — N collisions. Lhe Irlcasurenl<>nt of .l~}” COUIC1 dct,ect t hc presence of a neur charge(l1)0s011 I I“’ ullCOllSt I’ilille(l t)>”present Cxlx’rii;lt’111al data. .411cI if some new physics effects

are cl<’lecled ill p -—p (collisions. it Co[ll(l 1~(’\“(’[v interesting to rluu in thv n — J1 modetu const rain tile scalar w’ctor of tllc t l](or~. t Ilrol]gll 111(prese[]ce or absence of trili[lcarqliark Illass terllls.

13

+

cL- S t&-

R. u.

/

A -.

—--> AL = 2.Q Ta/

d—> d-

->

—>

.

o PtmwxpaA L .. pt.- ~e.ovskz-hn =>!

I

18

kT Issues

M.J .Tannenbaum

13NL/PHENIX

March 15, 1999

● kT is related to the net transverse momentum of a hard-scattering

jet-pair, or a Drell-Yan pair, or a pair of high PT photons, or the y+

Jet pair for direct photon production.

● In leading order QCD or the Quark-Parton model, all the above

pairs are coplanar with the incident beam axis: kT = O.e However, early Drell-Yan and inclusive high pT particle studies

showed that kT was measurable and non-zero. Systematic measure-

ments were made at the ISR and Fermilab.

● Some experimentalists and theorists may view the issue of kTdifferently-Experimentalists: multi-soft gluon, Gaussian;

Theorists: Hard-NLO gluons, power-law.

o The definitive work on kT, actually on the pT distribution of

Drell-Yan pairs was made by G. Altarelli, R. K. Ellis and G. Mar-

tinelli in Phys. Lett. 151B, 4ST (1985), based on the ISR measure-

ments. ~ should be incorporated into event generators.

* The effect of kT on the (]~uon Spin structure function is mainly

that it leads to an uncertainty in the value of Bjorken z of the in-

clusive direct photon measurements. This is illustrated and ways to

measure kT are discussed.

EVENT GENERATOR WORKSHOP M.ARCH 15, 1999

19

Parton kinematics

No

● Uncertainties in .xestimation– PYTHIA prompt photon. L

– PT ‘s gluOn’s“● naiive formula

– x#p@p-t(s)

● evaluation with simulation

F70.4x

0.3

0,2

0.1

0

r I I I 1’ , I 1’ , I r I , , T 11“” l’”

, l’” r l“ j,!,O Vs-200GeV

.----.,

❑ <s=500GeV .-

+

.

_.:::[:::’-[-”~::,;:”:;_”’”:

::

-<, ..---- --- .-” -

,<-,.,-------- 11 I I I Ill

0’ 5 10 15 20 25 30 35 40e 11 1 1 1 1 1 t I 1 1 I 1 1 1 I I 1 1 Ill I 1

PT (Gev\C)

%+s=500GeV photon ~ 10– 15GeV/c

o 0.2 0,4 0.6 O.a 1%

Us=200GeV photon H 10– 15GeV/c

$ ,o:=r:~m

o 0.2 0,4 0.6 0.6 1 0 0.2 0,4 0.6 0,8 1‘%

<s=500GeV phdon ~ 15-20GeV/c

~uxAs=200GeV photon ~ 15-20GeV/c

“o 0.2 0.4 0.6 0.8 I‘u

ds=200GeV photon R 25–30GeV/c

;I!cIIIlo 0.2 0,4 0.6 0.8 1

.%,

+.=500 GeVp hoton ~20–25GeV/c

o“:no 0.2 04 0.6 0.8 1

YW<s=500GeV photon ~25-30GeV/c

, . ,

Parton kinematics

● Uncertainty by kT- initial radiation– error— what

default settingk;=(l-z)Q2

z - splittingfraction of

N initial radiationw

estimation in the data interpretation

can we learn for QCD reaction itself?

aoD , , I , ! I , 0 r , 1~-9-1A•• ~

70!) UmwVmYl

60D - bm

50D

40D

30D

20D

100

D , I , 1 I 1 , , 1,, ,0 0,2 0.4 0.6 0.8 J

initial radiationoffkT&()

Js=200GeV photcm ~ 1+1 1GeV>c

600 :’ I I m Q8-* I*

U1YAE4

50D – UuuImwJILaw m

400 :

30D

20D

1m

D , 0 I k , 11 t 1 I 1 , Io 0,2 0.4 0.6 0.8 1

%-Js=200GeV photon ~ 10– 11Gal//e

0.3

0.25

00 “t’0.1 0.2 0.3 0.4 0.5

ds=200GeV photon ~ 10– t 1Ge;/c

V’o[umc 151B, number 5,6 PHYSICS LETTERS 21 Februazy 1985

LEPTONPA[RPRODUCTION,lT [SR ENER~IESAND QCD

G.ALTARELLICER,V, Geneva. S\l,i[:er/ond

and Diparrimen[o di Fisicc. Universi(d di Roma “‘h Sapienza”’ 1 and i.4’FI\:. Seziorre di Rornc, Rome, Italy

R.K.ELLISFerrm” Nafional Accelerator hborarory. PO Box 500, Batatia, IL 60S1 O, USA

and

G.kfARTINELLIINFN, Luboraron” Na:iona!i di Frascari, Frascari, Ila[.v

Received 27 November 1984

Motivated by some recent results from the ISR we have considered all available data on the production of Drell-Yanpairs by high energy proton beams. WC show that the iep!on pati cross sections and qT distributions are correctly described

by QCD using the known distributions of partons in the proton and acceptable values of the QCD scale A. No other free

pasameter is required. Vrithin the accuracy of the data nc) appreciable intrinsic transverse momentum is needed.

We have recently made [ 1] a theoretical reevalua-

tion of the QCD description of Iepton pair production

in hadron–hadron collisions. A full treatment of the

complete transverse momentum (~T) (dependence wasgiven including the large amount of theoretical infor-

mation about this process which has been accumu-lated over the last few years. The resulting ~T andy

distribution reproduces the correct perturbative be-

havior [2] at large qT and contains the soft ghson ex-ponentiation at leading [3] and next-to-leading [4,5]double logarithmic accuracy. Upon integration over

qT it reproduces the known perturbative results [6]

for the total cross section and rapidity distributiondu/d.v (including the terms of order ~, which give rise

to the ‘-K-factor”). The phenomenological implicat-ions for W/Z” production at the CER.N collider andfor the physics of the future Multi-TeV colliders hav;been discussed in detail in refs. [ 1,7]. On the experi-mental side, new data from the lSR [8] on DreU– Yan

* Work suppat ed in part by the “Ministerc dells Pub blica

[struzione”. Italy.

0370-2693/85/S 03.300 Elsevier Science Publishers B.V.(North-Holland Physics Publishing Division)

lepton pair production have recently been presented

(@= 62 GeV). The investigated rtige of lepton pairmass Q was extended up to Q ==25 GeV and the qrdistribution of the pair was measured. This set of data

completes a series of excellent experiments on Iepton

pair production [9– 11] performed over the years atthe ISR which is now being dismantled.

[n view of this theoretical and experimental prog-ress it appears timely to make a complete analysis of

alJ the available data on (continuum) lepton pair pro-duction in both p– p and p–~ collisions. We shall con-

centrate our attention on the data set at large valuesof the pair mass Q, i.e. above the T resonarrces (Q>11 GeV). These data are most appropriate for a

comparison with the asymptotic QCD predictionswhich are only valid if Q is large enough. For complete-ness we shall also extrapolate our calculations to vaJuesof Q in the range Q = 5–9 GeV between the J/W andthe T. The relevant set of data also includes Drell-Yanp– % processes at ~= 19–27 GeV [12] and p–p

processes at LSR with ~= 44, 62 GeV. If we aJso in-clude the results from the CERN collider on W/Z”

457

22

; LETTERS 21 February 1985

mental confirmation of this factor in proton-proton

scattering at the ISR

Wenow consider the qT and y distribution, which

is given by [1]

(dzb -iqTbR(b2, Q2, y)eda

=N J~e S(b2,Q2,y)

dQ2 dq+ dy,

)+W&,Q2, Y) . (1)

where N = 477a2/9Q2S, the kernel R a.rtd the regular

term (at qT = O) Y are givenbyeq.(57) and (62) of

ref. [1], and

A+

S(b2, Q2>y) = ~ ~ ‘# [Yo(bk) - 1]o

X {[1+ Da,(k2)] lrr(Q2/k2) – ;} . (~)

6.6i! GeV

TT 11+<25 Gev/c2

T

123 Ls 67

q (GeV/c)

Fig. 2. The data on qT d~tributions at JS =62 GeV and large

pair mass from ref. [8] (0) and ref. [11 ] (o) compared with

the theoretical predictions for the parton densities of ref. [15]

with A = 0.1-0.2 GeV. The data on the curves are all normal-

ized to the same area. No intrinsic qT is included.

459

Volume lSIB, number 5,6 PH’fs

Here AT is the maximum value of gT at frxed y:

AT/@= [(1 + r)2/4ch2@) – 7]1/2 , (:

and D is given [4] by

2rrD=~y7-; n2— ~nf) . (i

[n fig. 2 the data at ~~ 62 GeV for the normti-ized qT distribution du/dqT dy at y = O and Q = I I–

25 GeV are compared with the theoretical curves w-it

A = 0.1 –0.2 GeV. The relatively good precision of t]data and the accuracy of the theoretical fit can be

better appreciated if one notes that fig. 2 is a liear

plot. du/dq~ is often displayed on a logarithmic scabwhere only the gross features of the data can be re-

produced (see for example fig. 3 which refers to theextrapolated predictions at values of Q below the ~)

In figs. 4, 5 the average trartsverse momentum(q~) is plotted as a function of~at f~ed values of

G (@= 27.4,44,62 GeV) and as a function of&

1 2 3 1. 5q (GeV/c)

Fii. 3. Data on the ~T distributions at ~= 62 GeV and rel

tkly smaU dues of the pti mass [11] compared with the

theoretical curves obtained with the parton densities of ref.

[15] with A = 0.1-0.2 GeV. No intrinsic q~ is included.

460

23

2

1

1

Fig. 4. The average value of qT, (qT}, as a function of ~at freed @ = 27.4, 44, 62 GeV. The data at ~= 27.4 GeV are from

ref. [12], at ~= 44 GeV from ref. [1 1 ], and at @= 62 GeV from refs. [8-1 1 ]. The lower and upp-.n curves givers for each due

of@ Cmrrespondlo the parton densities of ref. [15] and A = 0.1-0.2 GeV respectively. No intrinsic ~T is included.

1.

3

2

1

Fig. 5. (qT) versus J3at fixed+= 0.22. Tle data at ~

= 19, 27.4 CeV are from ref. [12], at ~= 44 GeVfrom ref.

[11] andatw= 62 CeVfrom refs. [8,11]. The curves arethe theoretical predictions obtied by using the pa.rton den-

~_----l -sities of ref. [15] and A = 0.1 –0.2 CeV. No-intrinsic qT is in-

0eluded. At large values of ~, (qT) increases linearly with w.

50 100 1s0 200 At smaller values of ~ marked deviations from the linear law

6 (Gcv)are visible, which are due to soft ghron and scaling violation

24pre-asymptotic effects.

Quakonium Productions

T.-A. ShibataTokyo Institute of Technology/RIKEN

shibat aonucl.phys.titech. ac.jp

March 16, 1999

Abstract

Quarkonium productions in the polarizedproton-proton collisic)n were discussed. The emphasisis put on the charmonium productions from polarizedgluon-gllLlon collisions. The simulation was done byT. Sakuma of TITech and N. Hayashi of RIKEN. Thepresent work was done in collaboration also with Y.Goto and N. Saito of RIKEN.

It is known that the color singlet model do not re-produce the CDF data satisfactory. In the frameworkof the color octet model, the model parameters werefirst determined using the CDF data.

The simulations for PHENIX were done with PYTHIAand the polarized gluon distribution functions. It isshown that the spin asymmetry of charmonium pro-ductions, is sensitive to the choice of the polarized gluondistribution function. It is essential to further under-stand the charmonium production mechanism both ex-perimentally and theoretically.

25

●✎☛

ALL(PP + J/’4x) NAG(z,, Q2) AG(zz, Q2)a..L(gg ~ ~,+g)

G(zl, Q2) G(z2, Q2)

dAo doJb(PP + @Qx) = E(PP + @Qx)/~(PP + @Qx)

PYTHIA

~(PP+$Qx)=//

A

dzldzzGl(zl,Q2) Gz(~2,Q2)~(99 + @Q9)

CIAO#pp + @QX) =

H

z dA8dzldx2,AGl(xl, Q2)AG2(z2> Q )—d; (99+ @Qg)

26

16(+Q)‘~6(.~[2s+’L~8)])(ol~&’,(2s+1L~)10)

—

A ‘“+’ f’-’ - ‘L’””’ +’+’”-

27

M:1, J

‘i.,,......M 4,,

u.,.7..L,

➤ *

:,.

L4’”:1+’

W4 $9. .... .

➤ < *i

64 +9.+ ..;... r“L 4 *M 4,, ,!’

:L4 *=., .;. .+ ., .➤ 4 += 4

w j;

~

0.0 4S?q

.;.l

1111 1 ,, i(; II 1 1 I 1 1111 \ 1 ,( 1)1111 ! 1 1 Ill! I 1 1 I

(VAa9/qU) ‘dP/~P ( .l+l+)EI

;.. :.. l

F4 .a1,

;4 *Z,,. l.. .

1[ + m

I Y-1 >,,,, ,,, 1 1 I II ,1!, I ,, , 1 ,!, , , , !

y~o‘7 ? T

c> a ‘o

‘;VA%3N; ‘dP/9P;.1+1 +d6 =

mmov

* --● ✍✍ i>!

i

‘x

N .*. ●

.V.. ., : .,.. .. .. . . . .. . ...@... ..: .-*- ““! ● ~1-

— -!c ●_,. . . . .v ●

N......... . ..

o

II/-0

.!.-.............1----------- (’ ““”””””la●,: A!

...........

m

E-2G01+

...........<

N

0

>*

I

●

,

-f

00 1°’N ● -

?,-4--*--0

*,

ca :

0

Q

.

>f •1

●

, ,-●

●

✎✎

●

29

o

IIo ,“~:1,-:4N

‘0- :&---:o,:b

.. ..;? b

w~g~ ,;,, 4-+:g g o :f+i

-1 ‘“U-)lnln

e: .}%%2 ; Ii

00(3:k

~.. ...... ..... .. ... .......

● -).: *I

),b,>

co N o0 :

u)o ~

o~

z 2 &c5 o 0 0 0

0 +(;+A/r”+ d:d )lly q

.1~“’”””~

I“J

b

.

●

co.

,..

I > –e-- ● u. :*.......-i- 1

. q......0

...g . .. . . ..r ““”’’”’””ljj-..........

-s— +

--e— ●. . . . .“ 10- ●

+e--- b

.,. ,’6-- ●

h.0 ;

. . . . . .

9 :M ,~gs ● ,b

C)gg ““””“““ “’”””“““ ‘“” ~. . .

b

w gm % ● :(,C)COCO ‘. ”..:........ : .Uou ● ●

e,+11)1, il, ,11, 1,11, ,1, l,, l,

● ●! I I 1 1 [ r I l, !,,-*WC9q 0

Oltn Flno30

c> ~ooos~ g ~z00

0 0 0 0 Oa

o

co

u

04

0

(x+h/r+d+d)l%i

Stefano Frixione

Event Generators

at Fixed Order in QCD:

Jets and Isolated Photons

In this talk I will present phenomenological results relevant for isolated-

photon and jet production at ItHIC.I will briefly describe how to calculate partonic cross sections in pertur-

bative QCD beyond leading order, and the infrared safeness of observablewill be discussed. I will then concentrate on the problem of defining isolated-photon quantities. After reviewing the standard definitions which can befound in the literature, I will illustrate an alternative definition which hasthe virtue of being completely independent of the parton-to-photon fragmen-tation functions. and still it is well-defined order-by-order in perturbationtheory. This results in a cleaner estimate of the theoretical uncertaintiesaffecting the predictions for isolated-photon production.

I w-ill then turn to the discussion of a general method, which allows thecomputation of any infrared-safe quantity in any kind of hard collisions, atNLO accuracy in QCD. The method is based on the subtraction procedure,and therefore does not involve any approximation, neither in the matrix ele-ments nor in the phase space. Furthermore, the method is completely univer-sal, and does not require any algebraic manipulation of the matrix elements.This results in several computer codes, which work in a manner similar to

(although they are very different from) ordinary Monte Carlo parton showercodes. and ~vhich are available upon request.

Finally. I will present predictions ‘for jet and isolated-photon productionat RHIC. It will be shown that RHIC has a great potential for improvingthe know-ledge of the polarized gluon density. if the design luminosity will beachieved.

31

J))mfwlEAn4T!dJ.,“, -

,,

. . .‘“.

32

. ;.. ’.., ., ,, ... . . .. ..--.1-. ,.;..,,.’- . :..’.

._ ~: ‘j;:@.,,,,pow. tQ-clscLy. ● .* -.

34

. &7-s

1(7/ )<1 =.-

-.-SW<*V Gs-c <.-< WWJ /’l/f*-C/l ./Yi

35

Comparisons between Sphinx, Pythia+Asymmetries and LO/NLO

QCD. Oliver Martin. University of Regensburg. Germany.

.

The extracticm of polarized parton distributions is only possible with

a correct simulation of the physical processes involved. There are severaltheoretical approaches to calculate spin dependent observable respecting the

experimental cuts. A LO/NLO QCD calculation is based on the analyticalpolarized and unpolarized cross sections which are integrated using the Monte

Carlo method. The NLO (and higher order) corrections can also be modelledusing a LO cross section supplernented with parton showers. as it is done byPYTHL4 and its, polarized versic)n SPHINX. Even though PYTHIA is anunpolarized code it can be used to calculate asymmetries by calculating andbinning the asymmetry event by event. Since the comparisons between themethods have by far not been completed yet. this is only supposed to be astatus report.

All three methods obviously have to agree on the LO QCD result, whichcan be obtained in the event generators by switching off everything but thehard subprocess. Indeed the SPHIN”X and PYTHIA results for the unpolar-

ized cross sections for the production of inclusive jets. prompt photons andprompt photons plus jet agree o:n the 1 percent level. whereas agreementwithin the (5 percent) statistical error was shown for the polarized case.~w~~&~g ~~~i~~~~~]and fi~~] ~~a~~ r~~iarion ]~~~s ~~ ~~v~~”~iQn~for ]~rge

transverse jet energies. The origins still must be studied. The results ofPV’TUT A amrl +hn T n ;a+ omA mrfi.mm+ mhfi+am .~rlrw hlr C+af.m~ T7r;v;fima om,-11 A LLlrl LLILU LL,. U“ JbU -L. U ~L”lLA~. ~LL” L”Ll L“UC. L! “>7 “LLLCJL, ” L 1. A.” LJL CJ1l U

Lionel Gordon differ by about 5 percent and are therefore not satisfactory.l,r . ... --..-1. -.—._:—- .,. L- J-—- L---- .1--lVIUle WUIK l~llldill> LU Ue UUllfS 11~1~ tLlbU.

The parton showers are based on the collinear singularity and thereforeunderestimate hard ration off an inititai or final state parton. They conlpen-sate for it by allc+w-ingmultiple radiations to occur and effectively sum part

of the perturbation series to all orders. lt is therefore interesting to see inhow far NLO calculations agree with the results of an event generator. With

the standard shower parameters of PYTHIA 5.6 the inclusive one-jet ratesshow large differences of up to 40 percent and the asymmetries also differ

by as much as 2CI percent. However. tuning the parton showers leads to animproved agreement so that the rates and asymmetries differ by about 10

percent only.

37

PRELIMINARIES

0.8

0.6

0.2RQ’-1oo(%+

‘--.. \\,/asv Illaxg

*.‘.

-Dss 1 ~.\

=.

/Rsv k’.,.. ~~~2,- -..:.:. a

~.../Ds3 -..

,. ---- ------- . .. . .. .---- -- -

Csc--

0.4

PI

&-loo .%+

0.3 .— -

...

2

0.2 ,/-, . . Auv ‘

t_&l ./ ““

‘i’++00 [ , ! 1 +, ~~

0.05 0.1 0.15 02 0.05 [). 1 0.15 0,2

x x

2.0

1.5

M

x“

1.0

0.5

t

Q2=100 GeV2. . . .

/q

.,.

. ..-

V’ ~..-...”

...’,.. ._-, -’---~..- .-.-------

----- ...-./- ... -----. ..:;:-- . ~;----------- J. ..- .-

-.-5.:-” ~:_*.”2-_ — — /-1——

A- .:.... . GRV (.npol)

,..<-7=-- ,., ””” 1,,, .. :----

. . . I..-

. . . 1----

0.05 0.1 0.15 0.2x

t’vcuk+&eutvQbvVwstdw w PLO tpolf

so +kltCbqxavbt to

hep-pL/

.

#

SPHINX vs. PYTHIA - Hl+Shower

1

r ‘----

-1 —10 —

-210

-3

;b-Aa-n ~R

“.”. “

0.05

0.025

10

0.1

o

2

i

o

0.02

0

! I I t 1 I 1 I I ! I ! I I I 1 1

20 30 40

~ [Ge#

20 30 40

~ [Ge$

L

I --

I—

— I[- -1F --i11111,,,,11,,11

k*~T

T_.&.

, %+, .!-

.&1

I t I 1 lit, 1 1,,,,1,,,<-2 -1 0 1 2

11

0.1

0.05

0

-0.05

-0.1

0.2

0.1

0

-0.1

-02

0.1

0.05

0

“0.05

-0.1

0.2

0.1

0

-0.1

-0.2

,-

F---—-++++L!llllllllllltllt.

20 30 40 50

& [GeVl

p-l+ :,‘ +ttl

F,,I,,,,I,,,,I,,,I8

F,,l,l,ll,,r,l,,,l

: . t+++++

I ! I 1, I I I II 1 I I It 1

-2 -1 1 2

i!

NLO QCD vs. PYTHIA (Hl+Shower)

.-5020 ,- ...@.’... ~

..../.;. RI-n.:,...........:.,...-.... .....

.-

F.-.k“ :.-. “--.- --r----

,.-.=:*”@:@:

-3 ‘--; :--..

10 -- I..............................................=x&8A..Z:::::?’’’’::.:’”>”.>......,:..:l-l 1 1“ i I ! ! 1

. . . . . . .t ! I I I I I 1 I I

20 30 40 50ET [GeV]

g4J1

L ‘-—=”-’-

‘unpol. - —~ .1S1Om3 .2= 10

_.—

-3 —pol. ,,, ,,, ,1 --10

-2 -1 0 1

‘10-2=-2 -1 0 1 2

11

0.4

0.2I ,

0

-0.2

0.4

0.2

0

-0.2

-0.4

0.2

0

-0.2

40

L-1 I

1+ I

DLL-J20 30 40 50

ET [GeV]

.-! t I 1 I I t ! 1 L, ! I 1 I ! I

-2-1”0 1 2

~

h- ,. ----

:

-----.....--- .............,...,.

.............1 ! ! ! I ! 1 I ! ! I 1 ! II 1 1 4

-2 -1 0 1 2

n

;’

,’.:

.

.

.

.

.

—

NLO QCD vs. PYTHIA (Hl+Shower, tuned)

~lo~$1 ; —_ unpol.~ -1E*1O .—

w -2 ~_ —E 10 — —

-3Eg 10

-4:pol.

10-~

I I I I I I I I I ! I I I.-20 30 40 50

~ [GeV]

10

-1

--------..aa%.=----- - -- -

b-= s---

. - .=._-,.=+---●. :...L .- .

--_.mt%% IL L.z t--”- -

-3 - .-.. ......:-0 .: . . . . . .

. . . . . . .

,,, ,., ?. . . . ...=.. ,= =-, ,,, ,,I......+WAS.””””””...... : : :.-.., ., . . . . . . . . .. -.. . . . . . :. . . . ..-1 I 1 I t t t 1 fl 1 1 I I

20 30 40 50

~ [GeVl

--- I

-3 pol.10 I 1I!t!tIII1I

-2 -1 0 1 2

m’

-r-j swf --— —-””-- %-.

-2:=-> --- P-..-

a 10

-3.-< .-..~va-------- ~y~ . .10 +’..-.:

.- .-+.................-%%*.%.. ......-.......

ttr.t~............r....I ......,.,.-1 ! I 1 ! I ! 1 I I I I I

-2 -1 0 1 2

T

41

-0.4

0.2

0

-U

0.4

0.2

0

-w?

-0.4

20 30 40 50

ET [GeV]

nz1-

-2 -1-o 1 2

0.2

0

-0.2

-.

.....%....... 1

. . . . . -“- ... ...: ““’1

.- .. . . . . .. --. , -

I %.,..I I 1 ! I I I I I I I 1 d

-2 -1 0 1

‘L&)o 0

0 “A N

do I I I I I I I 1

.f!J‘+I I I i I’”f

st

CJo $a +o

+,

m Io

dcddpT~dqy [pb/GeV]

,.-:

!?.

4LL(PT) dc/dpTydqydqJ[pb/GeV]

d. .}, ,:!o ‘1jl[’’’’1~’l’.~’if

“./.,. ~

,.

t

,,,<

., .4;~ -; 1

,,....

0 – .;

,+

. .,.:{’ :,;

,.

“+

,,

cdo “

+

-J& +’-i5 +,& -

0

,.

?n

!?,s

... ,.. ,

. ..“, . .

LO QCD vs. Pythia (HI)0.2

0.1

0

-0.1

-0.2

b ‘A--+--+--=.“ --

8-*-I’n

F-.10 — unpol.1-1 —_—An _

j/jL10 20 .30 40 50

L,,l,,,,l,,llllL10 20 30 40 50

WY [GeVl, , ,. .7.’- *Y [GeVl

%=

“e-.. 0:1,.“u.,‘. ....,..’.,.’..

..e

- ;“’*&- ,%,.-’;..’..rd.. 8

. . ..-. .,

0.1

0

-0.1

-02

ri.05

-- =..”.”0 -.,_-n.- ------”’:-.

I 1 * 1 t a s !4 4 m ● 1,, ,4

102030 ”4050&r [Gevl

10 20 30 40 50

~r [GeVl*

-1-s-8

10I

02

0.1

0

-0.1

Ii102 —— ——

L.—— ——10

1

0.1

4202-2 2

0.2

0.1

0

4.1

42

.!“++&..&++--:t1

.

I II11Itt1IL

L.- .4- -

---0.05

0

-2 2 -2 0 2

n’

43

Problems with and Alternatives to Prompt Photon Production

L.E. Gordon

Summary:

Despite years of effort by theorists and experimentalists, prompt photon pro-

duction has still not yet lived up to its potential to tightly constrain the gluon

distributions in hadrons. Useful information on gluon distributions have certainlybeen ~~~~ne~ hut, ma nv ~nreSO]V~~ ~~eOKi,~C~ ~~d SQrn.e e~nerimental ~SSUeS are, --- .—-.-J ---r -.--— -—---

still hampering us from exploiting the full potential of this process. All this has im-mc,m+am+.-nc=m,,-~c=c far +ko RHTP cn;m m.r,rt.. m wh,ara A;r,a,-+ m~m+an =rarl,.e+;mnYWL “-”” bU’’”b’iUti’’b~” ‘w’ ‘“b ~k~~’ w OY~AzY’W6LWALAJ “ “tiAb ‘AAtiQ U YALU‘“LL YAwUU~wAUIL

is expected to be one of the main processes measured in order to constrain the spin3-—–—2-—L—I..-— J:. L—:L..L:-— .r AL- —-. –I .-—uepelluulL gluuIl uls LrluulJluIL 01 bllc Iluclcull, AG.

Recent phenomenological studies of collider and fixed target data using NLO. .-LJuu calculations have lead to difiering conclusions concerning both the compati-bility of the various data sets, and whether it is necessary ,useful or even consistentto supplement fixed order NLO QCD calculations with;k~ smearing effects in orderto better fit the data.

One recent study concluded that since no single set of scales and structure func-tions can be made to fit all the various prompt photon data sets, then it is possi-ble that the sets are simply incompatible, while another concluded that parton kT

broadening from soft glucmradiation can be consistently used to bring theory intoagreement with experiment.

Everyone adtits that there are still serious outstandjnz issues such as DOOTIV“----- ~ .–_J

known photon fragment ation functions, possible infrared sensitivity of the NLO cal-,-,tla+;mn mh-n ;cnl.+;nn ;C ;mnlswntan+tarl .nA larue rennrmaliza+inn .nrl far+n+va+innUQ-ua”ti ,. AAUu ..”. U..”.. . . .- y.uu.u... u.. . . . . . . .

b“ ----. -w.-...----- .-., ““. .--..”..

scale sensitivityy of even t;he NLO calculation in some important kinematic regions.This has lead to the suggestion that large ~T (g~ > Q/2) lepton pair productionmay be used as a surrogate for direct photon production since it completely avoidsthe problems with isolaticm and fragmentation.

Despite its problems, recent measurements of direct photon (and photon + jet)production cross sections at HERA are showing promise in shedding some lighton the gluon. distribution in the real photon. And the case of the gluon in thephoton before HERA has many parallels with the case of AG before RHIC, thusdevelopments at HERA should be at interest to us here.

44

,.

45

J,: A

4I , I i I I , I

Fp at 4s=1.8 TeV j

3 _- -0.9 s ycms 0.9

2 _

1

1-010

i

-110

1

= CDF 1992-93. 0 DO Preliminary 1994-95

statand sw uncertainties combined

*

NLO Theory (p=PT)CTEQ4M pdf

— (~)= 3.5 GeVlc ‘. . ..- (~) z o.O GeVlc

5~

$.- 0.0: i I +

F + T T’ T=A&o.5 – —- (k# = 3.5 GeV/c”

----- (1+ = 0.0 GeV./c ““4q&-l—_LL.J—_L I 1 I I 1

20 40 60 80 ‘ 100 120pT(GeV/c)

47

FIG.2. Top: The CDF and DO isolated direct-photon cross sections, comparedto NLO theory

without kT (dashed) and with k~ enhancement for (k~) = 3.5 GeV/c (solid), as a function cf pT.

Bottom: The quantity (Data–Theory) (Theory (for theory without kT adjustment),overlaid with

P Ovtctuwm

..

.

.

Unpolarized Parton Distributions:Current Status and Open Issues

~lobzd QCD Analysis of Partcm Distributions

Scope of Experimental Input

TheoreticalComickraticms/Uncertainties

Issuesfor new (1998/9) global analyses

Recent Results and Comparisons

Open Issues and Challenges

Comments cm Uncertaintiesof PartonDisUibtkms

BNL Polarized Event Generator Workshop

Wu-Ki Tung 1999

50

,

What goes into Global QCD Analysis of PartonDistributions?

Im princi FIIO

Experirnentai data On all available hard scat-teri ng procwxx5NLO QCD Hard-cross-sections (or beyond) forthese processes

Parametrized functions for the non-perturbativeinitial parton distributions+ NLO QCD-evolution of these functions

o Gfobal -fitting Of theoretical calculation(bawd on tticta-i.zation theorems of PQCD) to theexpcrimerrtal data, to determine the furldz imentalQCD constants (.Ac~~;j?,wi; i = c]uark flavors) andthe non-perturhative PDF parameters.

Many subtleties and complications . . . most dueto imperfect theory ancl/or experiment.

)-... This Workshop and This Subqroup <g.:

Physical processes and experiments -

DIS – Neutral Current (e,p on p,d)

SI..AC, E3C;/3 PMlS.: NMC, f~fi65, W], 7.E[.J5

DIS – Charged Current (v, O on nucleus)

(:(:: FJF+(./’;;, /:$)

Dreli-Yan – continuum (Iepton-pair)

E605, E.866 (d/p ratio)

Drell-Yan – W and Z

c DF (w-! <2\>t{:)?’!asy!?”!t”rlc!tr\f)

Direct Photon Production

WA70. ~..~’’.:, E706 “’::~. i ‘.:’. ‘.1 ‘“: ! “

Inclusive Jet PrOd UctiOll

CDF, DO

Lepto-production of Heavy Quark

Hl, ZEUS

Hadro-production of Heavy Quark,. ;.,: ;,, ;,,f,.;, ,,,,,,

*,.”—. —,. -. —-. —-.-”— ------- . . . . .

i2ecl color indicates “Nwu” for currertt analysis<.i,},.t;:: ,,;. :,,>. ,:,.::, ...’..’. ,“’.:!,. ,. ;>,1’; ,;.,:,,: .f, i. .:

j.:{:!,:: (j: j.”::

$4%(’--JJ’J

7-Jw!-k

‘u)

UJ

n E

C’dm

Major/Typical Issues Confronting Cut-rent GlobalAnalyses

Heavy (~~jark 5cl~ernes: 11C?vvth . tea’t;Ll1’(>

Zero- tmass-HQ-parton: “c:Ot>vciitiO/l~\l” S(:il.

No HQ parton at all : 3(4. )H(l VCX SC;].

On-mass-shell HQ partons : --- qen r)r;~1iz<:d M $

::(:I”I . CWZ(77), ACOT(87-98) ; TR(97)

Direct photons: pin the glu0r15?

Are current expts consistent?Is current theory sufficient for the task?Apanasevich, etal, 9808467; Aurenche, etal, 9811

<Juark ‘flavor’ - d/IJ large (small) JInterplay of charge asymmetry data:

E866, Wasym, NMCDeuteron target effect and Target mass correc-tiotl? BQdek&yang, 9$309480;

Kuhlmann talk & CTEQ paper in prep.

The sttclr]g cc}lupling col~s,tant CI(TN.,)Determineci by global fit, or set to best currentvalue?

Nl_Cl Cjcil) or E3cy(:?tl d’?

.

Comparison of MRS and CTEQGlobal Analyses

Previous vw”sions OTgencr’~1 MRS and CTEQ anal-Open Issues and Challenges

yses yielded very similar results – due to similar The GIUOn Distributionchoices of th. /exp. input. SM & New Physics searches

mC.L) New MRST and CTEQ5 Atlaiyw%

(Both fit input DIS and DY data well). . ... . ..-. ..—.—- .—.—.—......—..--..-...--......—--—”—.. . . . . .... . .. ................................MRST CTEQ5

conventional,HQ sch. on-shell (TR) shell (ACOT),

lxecj-flavor

Dir. Ph. WA70 + k~ ‘S

(~; fE706) (~ WA7~ E706JIncl. Jet — CDF + DO

Deut. Corr. —

(.Ys(Yn~) -fixwl: 0.1175 fixed: 0.118. . . .. . . .... ..................................................................................................................

?Ld Quark DifferentiationPrecision W-, Z- physics:

An earlier study of the range of G(;r,Q)

1.5

1.0*

Y 0.5

J

i\\/\‘ 1.51/\

1.0

0.5

Gluon Variations That Are Consistent

With DIS+Drell–Yan Data Sets /

.

Q=5GeV

MRSTMainMRSTUpper GluonMRST Lower Gluon //

. . . . . ....- .-.-..-.:,-. ---

–10%.. . . ....

Q=100GeV

I I I .-—~–– — l-- I 1

, ~-4 , @ , ~-2 0.I 0.2 0,3 0.4 0,5m-P Pat-ton x

Note the new MRST gluons relative to the range.

Clearly more definitive work is needed.

Parametrization of polarized parton distributions in the nucleon

Y. (htjo], N. Haydil VI Hira,i,. . 2,H. Horikawa3, S. Kumano2, M. Miyama2,

T: MCU-iia,N. Sa,itol , T.-A_. Shihat,aJ, E. krjmchi4eandT.Ya._rn_a,nkhi5~-----

~lkiiation La’borator_y, RIKEN. Saitama 351-01, Japan

2Department of Phvsics. Saga University. Saga 840-8502. Japan

3Faculty of Human Development, Kobe lJniversity. Kobe 657-8501, Japan

4Department of Physics, Tokvo Institute of Technology. Tokyo 152-8551, Japan.

‘Department of Llanagement Science. Fukui b-niversity of Technology.

Gakuen, Fukui 910-0028, Japan

Experimental data on the polarized structure functions have been accumulated for

the last several years. The structure function gl is measurecl with the proton, deuteron,

and 3He targets. tVe study the pararnetrizations of the polarized parton distributions in

the leading order (LO) of ~s and in the next-to-leading order (NLO) ~1]. The polarized

distributions are pro\ided with a number of pa m met m-s at Q;= 1 Gel~2. Considering the,,.

poslu~rity conciitioll an(i heiicity retention pl-op<rly. \\-e propose the foljowing cktributicm:

55

● Structure Function gl

g(x,Q2) =~f.i2{Aqi(~,Q2 )+A~i(~,Q2)i=]+fi[A~q@(A~i(x, Q2)+ATi(x,~2)) +ACg @ Ag(x,Q2)]}

Aq=qT–~LJ AC~ : coefficient functions

● Q2 evolution equation tDGLAP equation)\ /

,_nm

o Initial distributions

Afj(x, Q~)=$yxai (l+~x4)&.(x, Q~), (i=uv,dv,~, g)/. i

. ● Constraints1 ) Positivity condition/ d

lAfi(x, Q;) ‘< fi(x>Q~)

2) Counting rule for the heli~ity dependent

parton distributions

fT -(1 - X)’’z-’, fL -(1 - X)2”-’+*

fT >> fJ (x --+1)9

So, we obtain the following conditions for

the 12 parameters, v

ai >0, y, #–1, ‘i ‘–~i .

We assume the

1(x) at initial Q02,

A;(x)I

SU(3) flavor symmetry for

= AZ(X)= A;(x)7

and, the first moments qu, , q~, are fixed,

{

v v‘; d, = F+D~)q“ +~u~, ; dv

= 3F– D

F= 0.463 * 0.008, D= 0.804 * 0.008

7 = 0.9:26, qd = –0.341U ~, 1’

We determine J to satisfy the requirement

qi=~’ Af(x, A)dx, ~x min

We m ustdetermine10parametersby thex ‘-fitting!

w, y_, A., (X8, yg, A, ,,q q

2’2-fitting to the data (Proton, Neutron, and Deuteron)

X 2

‘z i

(A

data calA)

2

l,i — l,i

~ data 2i

Which is minimized by the CERN subroutine MINUIT.

mm

We analyzed with the following conditions;

The unpol PD GRV94 (by PDF-Lib)initial Q02 Q o2=1 GeV2Number of flavor N~= 3AQCD ALo= 232 MeV,

A~Lo= 248 MeV

. . .

Semi-exclusive reactions in pp collisions

M. Maul, Nordic Institute for Theoretical Physics (NORDITA)

Blegdamsvej 17, 2100 Copenhagen, Denmark

Recently in [1] the idea was proposed to study semi-exclusive events in electronproton collisions at HERA. The simplest reaction in such a case, would be e +

p + jet + m++X. Kinemakicaly this process is analogous to the correspondingelastic reaction in exclusive meson production, and the factorization theoremswhich apply for the exclusive case are also \’slid in the semi-exclusive case.The basic idea is to look fcjr events, where a large rapidity gap between the pro-duced hadron and the produced jet exists. In this case soft interactions in theproduction process of the final meson are excluded and consequently the pro-duction process can be described by a hard scattering amplitude times the wavefunction of the produced :meson. This is a much more direct access than the

tracking of leading particles in the end-particle spectrum, where the productionmechanism can only be described in terms of fragmentation functions, which areunknown objects of their cmm, and where the underlying physics is from its na-ture of a soft type and is not really understood so far.It would be of great interest to compare the semi exclusive pion production to

the corresponding process in pp collisions. In this case, to account for the colorneutrality, two jets, a quark jet and a gluon jet, have to be produced, i.e. p

+ p -+ ~++ jetl - j etz -+ X. We then have to require two rapidity gaps, one

between the gluon jet and the produced meson and a second one between thequark jet and the produced meson. If the two jet momenta and the momentumof the produced meson can be measured with good accuracy, then we are froma kinematical point of view in the same situation as in Drell Yan and can gethold of the two momentum fractions Zl ;and ZZ of the scattered quark and thescattered gluon, so that all theorems that apply for Drell Yan can be also appliedto this process.The ~ery interesting point for such a reaction to be compared with the corre-sponding ep reaction is that we might be able in this way to get hold of ‘inmedium effects’ in the pp reactions. Such effects have been studied so far for.J/V production: While in the ep case the color singlet model is successful, aconsistent description seems not to be feasible up to now in pp, however it wasindicated in [2~ that the existence of a cllmd of gluonic comovers could account

for most of the signatures in pp charmonium production. It would be of greatinterest, w-hether such an effect could be observed analogously in semi-exclusivex+ production including all the possibilities of polarization.

[1] S. ,1. Brodskj-, Jf. Diehl, P. Hoyer. S. Peigne. hep-ph/9812277,“~] P. Hover, S. Peigne (Nordita), Phys, Rev. D.59:034011,1!199..-

60

J. Jhe qemrol wept : kni-mc hive

● &scri& &c? ~rdoctiun 0$ Wfofls

+-w+

‘! ‘f9%!5WY

● similar p?xesses re~ on C2 Com@?&5’&

u62-

,422-z’

Jhe cab

~cduc tion

W’y’,y’

d m. A?o

hep-ph /$s%%Os

I

? 2q = (~ 5,-P)f“=(’P,6,P)

pp Cms

9. 3Lemc7 LIZ ,prelimZOrI&,

9 := ~+~q+pz=

9 ‘= 9.49= =“x, ~+

9- = 90”97 = xz~’

—>

,T *c+ tq

- 65 -

kl

k2

. . . .

Pq

Pa

Pq

i . . .

%

i . . .

- 66 -

Higher-order Contributions to Prompt Photon Production

L.C. Bland. Zizdianu Uni~ersizy

One of the primary goals of the RHIC spin program is to determine the contributiongluons make to the proton’s spin. The dependence of photon production on the felicities ofcolliding protons promises to be one of the most sensitive probes of the polarized gluondistribution. The STAR spin program will focus on observing photons in coincidence with‘away-side’ jets, thereby enabling an event-by-event reconstruction of the initial-state partonickinematics. This method enables the possibility of directly extracting AG(x) from the measured

longitudinal spin asymmetry A,L (Fig. 1).

The assessment of the expected value for A Lt. is based on the PYTHIA 5.7 event

generator, extended to account for polarization observable. PYTHIA is widely used to predictthe expected experimental backgrounds to photon production associated with high-p~ n“(~o )production and is extensively used for designing experimental triggers. A reasonable question toask is how well does PYTHIA describe existing data? For high-p~ hadron production. it isstraightforward to compare PYTHIA predictions to measurements made by the UA 1 detector atCERN (Fig. 2). Over the range of the measurements, PYTHIA. operated in itsdefault mode,gives a reasonable description of the data. The comparison for photon productionis lessstraightforwardto make because of the complex conditions employed in mostexperimentstoextractthe prompt photon yield from the prolific neutralmeson production background.Employing only the UA 1 isolation condition, but not the other conditions usedto analyze thedata, the PYTHIA ‘direct photon’ processes (including the gluon Compton process and qij

annihilation) significantly underpredicts the UA 1 inclusive photon data (Fig. 3a). The othermore complex cuts used by the UA 1 group, if applied to the PYTHIA predictions, would resultin even smaller values for the photon production cross section.

The question now is whether there are other mechanisms within PYTHIA that canproduce high-p, photons, and whether these mechanisms are constrained by experiment. Theanswer to both questions is yes. The CDF group has recently compared their pji + y + 2jet

datasample atw’s= 1.8 TeV to ‘bremsstrahlung’ photons arising within the initialand final-stateparton shower model in PYTHIA. The event generator adequately explains mostof the CDFdata. We can now compare thisyield to the UA 1 data (Fig. 3b). With only theisolation cut, this‘fragmentation’ photon yield overpredicts the UA 1 data. Once again, the other.more complex,cuts used by the UA 1 group would result in smalleryields, suggesting thatPYTHIA might beable to fully explain the inclusive photon cross sections at ~s = 546 and 630 GeV.

With these two mechanisms for producing photons, we can predict the photon yieldexpected at RHIC at N’S= 200 GeV (Fig. 4). From the PYTHIA simulation, the ‘direct photon’processes are seen to dominate at this low energy. ”It is expected that the ‘fragmentation photon’yield increases more rapidly with energy than does the ‘direct photon’ yield. Turning to thepolarization observable. in contrast to the ‘direct photon’ processes, processes resulting in‘fragmentation photons’ are found to have ALL = O (Fi~. 5). By combining the polarization

observable from all the subprocesses contributing to both the ‘direct’ and ‘fragmentation’photon yields, the proton longitudinal spin asymmetry, AU, is found to be only slightly reduced

relative to the ‘direct photon’ subprocesses alone (Fig. 5). This suggests that prompt photonproduction can still serve as a quantitative measure of the gluon polarization within the proton.

67

.-., n,, ——3 UUIJ(J ‘-

25000 ;

15000;d~ [dx[

10000’b

5000

/) -

_- \s = 500 GeV,:

-

-_ ‘b”800pb-J

~ 369,000events

>L.

7

lL ‘vs =200 Gel’

i 320 pb-lI ..4 183,000 eveun~

F ~. /..

;%+ y— ,.,

:,.~n –/-’, -1.

.%; +&+-— ,..”,,--- ,.,, /

%_“/, @/,. ,, -

—

,

.~o.2 *0-1

Reconstructed Xgluorl

–-

0.1-L ..—— .. —-..—— ,—

0.01 0.1 1-,10”’0.01 0.1

Reconstructed Xgluoll

. Fit uncorrected AG(x) reconstructed from 200 + 500 GeVsimulations with Gehrmann-Stirling functional form a

~: Grecon (X) dx =: 1.62k 0.23 -Z.{AGinpuf(X) dx = 1.710-—-—.——-

.. ,- ... >e,. -.”-~v~. -..--.f l.,...- ., =....,. . . .—- .2-.. ,’-= . . . .=., =.’3 . . .. . . .. . . . . ... . ..=.

.4

Fig. 1

10

1

,.-1

p ~ -+ charged particle

2.5 5 7.5 10 ?.5 5 7.5 10pT (GeV/c)

]0 =. “ —

ptl =9.941

PYTHIA 5.7 (;T22 GeV/c)

UA1 dataC. Albajar, et al.Nuc[. Phys. B335 (1 990) 261

A.

(1 + P/P#’

—-—.—+2.5 5 7,5 10

Fig. 2

69

NOTE: Only UAI isolation cut is applied. Missing ET cut and deconvolution of

summed ET distribution within isolation cone are not performed.

..J -

10 ~

~Comparison of ‘Fragmentation Photon’E. Fig. 3b

Prediction (P YTHIA) to LTA1 Data0<-< *,~+ . pj~+yx

.J - -4-

10 ~

~S = 630

-6-! I Illi : ~o-6- 11,,

10Z() 40 60 20 40 60

pT (GeV/cj

Q PI’TJYIA 5.7 no isokuion CU1

* P YTHIA 5.7 UA 1 isolation cur only

UA 1 data – C. Albajar, et al. Phys. Lett. B209 (1988J 385

A,,” (1 +pT/p, )-”

70

What are the contributicms from higher-order processes?

From calculations (Gordon & Vo,qelsang), we should

.apect important contributions to the photon yield

from izighel--order processes.

PYTHIA includes only LO pQCL) processes. Higher- orde]- effects are modeled

~’ia ‘parton showers’. The above process is contained ~vithin PYTHIA viaso-called ‘fragmentation photons’. Comparison bet~veen p + ~ + y + 2 jetdata and the PYTHIA j5-agmentation ’photon yield has been made bythe CDF group at ds = 1.8 TeV (PRD 57, 67~. Good agreement & fOU]ld.

p +p -+~ +jet +X ds = 200 GeV 75pb-1 (P YTHIA 5.7)(includes UA2 isolation condition)

z— ,, :.— ,, ,7

L

-.

\

direct photons,O?= ‘:-L+ 45, ]4] events –

<. /

,.2

-+

7 “’---

L.

~ragnzenianon ‘{: I 7,244 events

—

pT gamma (spin sum J

3500” –

3000 -

2500 –-

20Q0–

1500 –

1000 –

o-2

&;-.L

-1.5 -1 .().5

Iog(.yhm) (Spin sumJ

* a larger radius isolation cone is essential to Yedllce

the yield from ‘fragmentation p}zoloFM’

71

What is the influence of

Fragmentation photons’ on

polarization observable ?

Cuts applied to simulation:

10< PT.{< 20 GeVlc UA2 isolation condition

-0.3< qjet <1.3 (for leading jet) max[ x+jx_ ] >0.2, where

2PT ( eq-f + e~iet )-1< Ty <2 (barrel + endcap EMC) x+=—— N’s

‘Fragmentation’ photojz

—

—

().2 : —;.—E++

j-++ +

+, -0-

=—

-().2 ‘;L_. i ~

,,, ~-

0 0.1 0.3

Recomtructed x~lUo,l

* e.~pect a small dilution of ALLf~-om fragmentation photons

0.6

0.4

-0.2

100pb”l

+

=—..————. . .0 0.1 (7.2 0.3

Reconstructed x~lUo,,

‘Direct’ onl>

‘Direct’ + ‘Fragmentation -

.

Fig. 5

72

WORKSHOP ON EVENT GENERATOR FOR RHIC SPIN PHYSICSMARCH15-19,1999

ORGANIZERS: NAOHITO SAITO AND ANDREAS SCtiFER

●

ACTI.JALPARTICIPANTS

NAME AffiliationlAddres~ E-MA L A1 DDRESS

Les Bland IUCF bland@ iucf.indiana.edu

2401 Milo B. Sampson Lane

Bloomington, IN 47408 USA

Bemd Bassalleck University of New Mexico bassalleck@baryon. phys.umn.edu

800 Yale NE

Albuquerque, NM 87131 USA

Gerry Bunce Brookhaven National Laboratory bunce@bnl.gov

AGS & Physics Departments

PO. Box 5000

Upton, NY 11973-5000 USA

Abhay Deshpande Physics Department abhay.deshpande @yale. edu

Yale University

P.O. BOX 208121

New Haven, CT 06520-8121 USA—

Douglas Fields University of New Mexico fields@ phys.umn.edu

800 Yale NE

Albuquerque, NM 87131 USA

Stefano Frixione CERN frixione@itp.phys. ethz.ch

TH Division

CH-1211 Geneve 23

Switzerland.

Lionel Gordon Thomas Jefferson National gordon@hep.anl.gov

Accelerator Facility

12000 Jefferson Avenue

Newport News, VA 23606 USA

Yuji Goto RIKEN goto@bnl.gov

Brookhaven National Laboratory

Physics Department, Bldg. 902

PO. Box 5000

Upton, NY 11973-5000 USA—

.Matthias Gross-Perdekamp Brookhaven National Laboratory matthlas @bnl .gov

Physics Department, Bldg.5 10A

P.O. Box 5000

Upton, NY 11973-5000 USA

Tim Hallmarr BrookJraven National Laboratory hallman@bnl.gov

Physics Department, Bldg.5 10A

PO. Box 5000

Upton, NY 11973-5000 USA

Naoki Hayashi RIKEN hayashi t@bnl.gov~. 1, Hiro~awa, W&o. shi

Saitama, 351-0198

Japan

73

WORKSHOP ON EVENT GENERATOR FOR RHIC SPIN PHYSICSR,f. m,-.TT1C in lnnnLvA.4nt-n IU-A7, 1777

ORGANIZERS: NAOHITO SAITO AND ANDREAS SCHAFER

NAME ~ationlAdd es~r E-MAILADDRESS

Masarrori Hirai Saga University 98td25@edu.cc.saga-u. ac.jp

Hadron Structure Laboratory

Saga 840-8502

Japan

Ken’ichi Imai Kyoto University imai@ne.scphys. kyoto-u.ac.jpIGtashirakawa-Oi wakecho,

Kyoto 606-01. Japan

Bob Jaffe Centel- for Theoretical Physics & Labora- jaffe62mitlns.mit, edutory fcjr Nuclear ScienceDept. of Physics, Room 6-2,11

Massachusetts Inst. of Tech.

Cambridge, MA 02139 USA

Kazu Kunta RIKEN/RBRC kurita@bnJ.gov

Brookhaven Nauonal Laboratory

P.O. Box 5000

Upton, NY 11973-5000 USA

Berqi Lewis University of New Mexico benjiL@strange. phys.umn.edu

800 Yale NE

Albuquerque, NM 87131 USA

Oliver Martin Institute for Theoretical Physics oliver.martin @physik.uni-regensburg.de

University of Regensburg

93040 Regensburg, Germany

Martin Maul Nordisk Institute for Theoretical Physics maul @norhn 10.nordita.dk

Blegdamsvej 17

DK-2100 Copenhagen, Denmark

Frank Page Brookhaven National Laboratory parge@bnLgov

Physics Department, Bldg. 510A

P.O. Box 50007,. .– .,., ,10-0 cnnn, ,,-.up[un, LXI I IY /J-Juw UJA

Atharrasios Pewidis Physics Department petndis@iastate. edu

Iowa State University

Ames, IA 50011 USA

Naohlto Saito RIKEN/RBRC saitot@bnl. gov

Brookhaven National Laboratory.-. . . . . . ,–—--—. -—. “,. - .-, n,-rnyslcs IXPWL1llCIIL. D1ug. .J lULP.O. Box 5000

Upton, NY 11973-5000 US.4

Andreas Schafer Institme for Theoretical Physics arx!reas l.schaefer@physik. un]-regensburg. de

University of Regensburg

D-93(MO Regensburg, Germany

74

WORKSHOP ON EVENT GENERATOR FOR RHIC SPIN PHYSICSRfl.r,o, wlc10 lrmnlvM’inLn AJ-17, 1777

ORGANIZERS: NAOEIITO SAITO AND ANDREAS SCHAFER

NAME bffiliatiorsfAddessr E-MAILADDRES$

Toshl-Aki Shlbata Department of Physics shibata@nucl.phy s.titech.ac.jp

Tokyo Institute of Technology

2-12-1 Ookayama. Meguro-ku

Tokyo, Japan 152-8551

George Sterman Institute for Theoretical Physics sterman@insti.physics. sunysb.edu

SUNY, Stony Brook

Stony Brook, NY 11794-3840 USA

Mike Tarmenbaum Brookhaven National Laboratory mjt@bnl. gov

Physics Department, Bldg. 5 10Cp,~, ~~~ ~~oo

Upton, NY 11970-5000 USA

... ..-wu-rw I ung

m- —--—-— . . Cm!-.;.,-.lX~~l LIUCU1 ULruj 31L’S ...--.%,-. —-..-2..

LUil&W~cl.lll> U, C.UU

Michigan State University

E. Lansing, Ml 48824 USA

Jean-Marc Vlrey Universitaet Dortmund virey@catbert.phy sik.uni-dortmund.deInWiIIUrfider Phvsik. ... . ...

D-4422 1 Dortmund

Germany

Werner Vogelsang State University of New York wemer.vogelsang t@cem.ch

Institute for Theoretical Physics

Stony Brook, NY 11794-3800 USA

75

RIKEN BNL Research Center

Workshop on Event Genreator for RHIC Spin PhysicsPhysics DepartmentMarch 15-19, 1999

AGENDA

llonda~, March 1,5 (Room 2-160~

09:30-10:30 Introduction \Naohito Saito]

10:30-11:00 Coffee

11:00-12:00 Recent Progress in Theoretical Studies of Spin Physics (Andreas Schaefer]

13:30-14:30 N;ew Processes and Parity l“iolating Spin .\symmetries [Jean-N1arc Virey]

14:30-15:00 Coffee

15:00-16:00 ICT Issues [T13C) [Mike Tannenbaum]

Tuesdav. March 16 (Room 2-160]:

09:15-09:45 Quarkonium Production [Toshi-.Aki Shibata]09:45-10:00 Coflee.An,,. ,,-.nlU:UU–ll:UU Special Spin Discussion: Trims versity and InteifeIerIce Eragmerltation F“UrlctiOrls

~Robert Jaffe] (no proceedings package)~~:Q@~~:~~ C’. ff,,--JJ -.

11:15-12:15 Went Generators at Fixed Order in QCD: Jets and Isolated Photons [Stefano Frixione]

W’ednesdav. March 17 (Room 2-16(U:

(-Jg:~Q-lQ:3Q ~orn.narimn< Ret,wQQn Snhinx P~thia+.&syrnrn_etries and IXLC) QCD [oliver Martin)~ _-- —---- —r.----.., - ~ ..-

10:30-11:00 Coflee11:00-12:00 Potential Problems with, and -alternatives to. Prompt Photon Production at Colliders

[Lionel Gordon]

Thursdav. March 18 (Room 2-160):

09:00-10:00 CTEQ Parton Distribution Functions [W~u-Ki Tlmg]10:00-11:00 Special Spin Discussion: Spin Measurements with HER\fES [Naomi Makins]

(no proceedings package)11:00-11:30 Coffee11:30-12:30 Parametrization of Polarized Parton Distributions in the N-ucleon [hIasanori Hirai]

76

.

Forthcoming RIKEN BNL Center Workshops

Title:Organizers:Dates:

Title:Organizers:Dates:

Title:Organizers:Dates:

Title:

Organizer:Date:

Numerical Algorithms at Non-Zero Chemical PotentialT. Blum/M. CreutzApr. 27--May 1, 1999

Gauge Invariant Observable in Gauge TheoriesP. Orland/P. van BaalMay 25-29, 1999

OSCAR II: Predictions for RHICY. Pang/M. GyulassyJuly 8-16, 1999

Coulomb and Pion-Asymmetry Polarimetry and HadronicSpin Dependence at RHIC EnergiesE. LeaderAugust 18, 1999

For information please contact:

Ms. Pamela EspositoRIKEN BNL Research CenterBuilding 51OA, Brookhaven National LaboratoryUpton, NY 11973, USAPhone: (516)344-3097 Fax: (516)344-4067E-Mail: rikenbnl@bnl.govHomepage: http: //penguin. phy.bnl.gov/www/riken. html

o0 RIKEN BNL RESEARCH CENTER

EVENT GENERATOR FOR RHICSPIN PHYSICS

MARCH 15-19, 1999

. . .. ., --- ---- .u Keran

Nuclei as heavy as bullsuopyrlgnt~cwwIA ,

Through collisionGenerate new states of ~;t~; I

. .Speakers:

L. BlandM. HiraiO. MartinT.-A. ShibataJ.-M. Virey

S. Frixione L. GordonR. Jaffe N. MakinsM. Maul A. SchaeferM. Tannenbaum W.-K. Tung

Organizers: Naohito Saito and Andreas Schaefer