polarized dis with future polarized colliders

Polarized DIS with

Future Polarized Colliders

Abhay DeshpandeRIKEN BNL Research Center (RBRC)

Precision Lepton-Nucleon Scattering: HERA III WorkshopMunich, December 18th, 2002

RIKEN BNL RESEARCH CENTER

December 18, 2002 Physics Opportunities at Future Polarized Colliders

2

OverviewOverview

• Introduction to different proposals under consideration for polarized DIS

• Physics opportunities with:Physics opportunities with: -- Polarized HERA, Electron Ion Collider (EIC) at BNL

-- Tesla*HERA (THERA) + TESLA-N/ELFE@DESY

• Status of Polarized Colliders at BNL -- Status and comments on EIC

-- Status of polarized proton beam acceleration & collisions at BNL

• Summary


3

Deep Inelastic ScatteringDeep Inelastic Scattering

•Observe scattered electron/muon & hadrons in current jets•Observe spectator or remnant jet


4

Why Collider in the Future?Why Collider in the Future?

• Past polarized DIS experiments: MOSTLY FIXED TARGET• Collider has distinct advantages --- Confirmed at HERA

• Better angular separation between scattered lepton & nuclear fragments

Better resolution of electromagnetic probe Recognition of rapidity gap events (recent diffractive physics)• Better measurement of nuclear fragments• Higher center of mass (CoM) energies reachable• Tricky integration of beam pipe – interaction region -- detector


5

Projects Under ConsiderationProjects Under Consideration

• Pol. HERA needs polarized protons (Siberian Snakes, polarimeters etc.), Use existing detectors(?)

• EIC needs a polarized electron accelerator facility at RHIC & a new detector

• THERA & TESLA-N & ELFE need TESLA and polarized protons in HERA & a new detector

Machine Lumi/Year Sqrt(s)

Tesla-N (fix target)

ELFE at DESY

100+ fb-1 10-30 GeV

~10 GeV

EIC 4+ fb-1 20-100 GeV

Pol. HERA 150 pb-1 300 GeV

Pol. THERA 40-250 pb-1 1-1.5 TeV

What Physics? What Physics? Luminosity? CM Energy? Luminosity? CM Energy?


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Kinematic CoverageKinematic Coverage

20-100 GeV

ELFE: Q2max~ 102 GeV2

xmin ~ 10-2 (1 GeV2)

TESLA-N: Q2max~ 103 GeV2

xmin ~ 10-3 (1 GeV2)

EIC: Q2max~ 104 GeV2

xmin ~ 10-4 (1 GeV2)

HERA: Q2max~ 105 GeV2

xmin ~ 10-5 (1 GeV2)

THERA: Q2max~ 106 GeV2

xmin ~ 10-6 (1 GeV2) EIC overlaps with the fixed target experiments because of the changeable beam energies


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Luminosity Vs. Center of MassLuminosity Vs. Center of Mass

TESLA-N

THERA

EIC has variable:-- beam energies-- polarized light nuclear species 100 times HERA luminosity Collisions 2010(?)

HERA has:-- 3 times larger CM Collisions 2007(?)

TESLA-N/THERA-- Need the DESY LC-- Low/High CM-- High/Low Luminosity Collisions 2015(?)


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Scientific Frontiers: Future DIS Scientific Frontiers: Future DIS ExperimentsExperiments

• Nucleon Structure: polarized & unpolarized e-p/n scattering -- Role of quarks and gluons in the nucleon -- Unpolarized quark & gluon distributions -- Spin structure: polarized quark & gluon distributions -- Correlation between partons hard exclusive processes leading to

Generalized Parton Distributions (GPD’s)

• Nuclear structure: unpolarized e-A scattering -- Role of quarks and gluons in nuclei -- e-p vs. e-A physics in comparison

• Hadronization in nucleons and nuclei & effect of nuclear media

-- How do partons knocked out of nucleon in DIS evolve in to colorless hadrons?

• Partonic matter under extreme conditions -- e-A vs. e-p scattering; study as a function of A

Unpolarized Low x Issues:A. Caldwell

EIC e-A Physics


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Polarized DIS at Future FacilitiesPolarized DIS at Future Facilities• Spin structure functions g1 (p,n) at low x, high precision

-- g1(p-n): Bjorken Spin sum rule better than 1% accuracy

• Polarized gluon distribution function G(x,Q2) -- at least three different experimental methods

• Precision measurement of S(Q2) from g1 scaling violations

• Polarized structure function of the photon from photo-production

• Electroweak structure function g5 via W+/- production

• Flavor separation of PDFs through semi-inclusive DIS• Deeply Virtual Compton Scattering (DVCS) Gerneralized Parton

Distributions (GPDs)• Transversity• Drell-Hern-Gerasimov spin sum rule test at high • Target/Current fragmentation studies• … etc….

DESY-PROC-1999-03 & EIC White-Paper BNL-Report-68933 DESY-PROC-1999-03 & EIC White-Paper BNL-Report-68933 (Feb.2002)(Feb.2002)

All of them at EIC & Pol. HERA Some at TESLA-N/ELFE


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Spin structure function gSpin structure function g1 1 at low at low xx

~5-7 days of data3 years of data

A. D. & V. W. Hughes EIC WS at Yale’00

Studies included statistical error & detector smearing to confirm that asymmetries are measurable. No present or future approved experiment will be able to make this measurement

Polarized HERA Polarized EIC


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Polarized Gluon MeasurementsPolarized Gluon Measurements

• This is the hottest of the experimental measurements being pursued at various experimental facilities:

-- HERMES/DESY, COMPASS/CERN, E159/E160 at SLAC

-- Low scales poses a potential problem for interpretation -- TESLA-N? -- RHIC Spin (polarized p-p) -- Issues of non-DIS scattering

• Deep Inelastic Scattering kinematics of EIC/HERA -- Scaling violations (pQCD analysis at NLO) of g1 (TESLA-N) -- (2+1) jet production in photon-gluon-fusion process -- 2-high pT hadron production in PGF (TESLA-N)

• Photo-production (real photon) kinematics at EIC/HERA -- Single and di-jet production in PGF -- Open charm production in PGF


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G from Scaling Violations of gG from Scaling Violations of g11

• World data (today) allows a NLO pQCD fit to the scaling violations in g1 resulting in the polarized gluon distribution and its first moment.

• SM collaboration, B. Adeva et al. PRD (1998) 112002 G = 1.0 +/- 1.0 (stat) +/- 0.4 (exp. Syst.) +/- 1.5 (theory)• Theory uncertainty dominated by the lack of knowledge of

the shape of the PDFs in unmeasured low x region where EIC data will play a crucial role.

• With approx. 1 week of EIC statistical and theoretical uncertainties can be reduced by a factor of 3-5

-- coupled to better low x knowledge of spin structure function

-- less sensitivity on factorization & re-normalization scale variations in fits as new data at low x is acquired

A. D., V. W. Hughes & J. Lichtenstadt EIC WS, Yale’00

See J. Lichtenstadt’s talk in this meeting


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Photon Gluon Fusion at EICPhoton Gluon Fusion at EIC

• “Direct” determination of G -- Di-Jet events -- High pT hadrons • High Sqrt(s) at EIC & Pol. HERA -- no theoretical ambiguities in

interpretation of data• Both methods tried at HERA in

un-polarized gluon determination & both are successful!

-- NLO calculations exist -- H1 and ZEUS results -- Consistent with scaling

violation F2 results on G

Signal: PGF

BackgroundQCD Compton


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Di-Jet events Analysis at NLODi-Jet events Analysis at NLO

• Statistical accuracies shown for at 2 EIC luminosities and 1 pol. HERA luminosity• Detector smearing effects considered• Analysis performed at next to leading order• Will easily differentiate amongst different DG scenarios• Uncertainty in the first moment of DG will be improved by factors of 3

• If combined with g1 NLO analysis effective improvement is even more• EIC will give an absolute uncertainty of about 3-5% in G

G. Radel, A. De Roeck, EIC WS, Yale’00

At Electron Ion Collider: 4+ fb-1/yr At HERA: 150 pb-1/yr

J. Lichtenstadt, A.D. & V. Hughes, EIC WS, Yale’00


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Di-Jet World Data for Di-Jet World Data for G/G G/G

EIC:Good precisionConstrains shape of G(x)HERA:Lower x accessPolarization in HERA much more

difficult than RHIC(?) D. Barber’s talk tomorrow

G. Radel & A. De Roeck, EIC WS, BNL’02

EIC Di-Jet DATA 2fb-1

HERA Di-JetData 500 pb-1


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Polarized PDFs of the PhotonsPolarized PDFs of the Photons

• Photo-production studies with single and di-jet

• Photon Gluon Fusion or Gluon Gluon Fusion (Photon resolves in to its partonic contents)

• Resolved photon asymmetries result in measurements of spin structure of the photon

• Asymmetries sensitive to gluon polarization as well… but we will consider the gluon polarization “a known” quantity!

Direct Photon Resolved Photon


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PDFs of polarized photon at EICPDFs of polarized photon at EIC• Stat. Accuracy

estimated for 1 fb-1 running (1 month at EIC

including 50% inefficiencies of detector)

• Single and double jet asymmetries

• ZEUS acceptance

• Will resolve photon’s partonic spin contents

Direct Photon Resolved Photon

M. Stratmann & W. Vogelsang, EIC WS, BNL ‘01


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Photon Structure Function at Photon Structure Function at HERA/EICHERA/EIC

M. Stratmann & W. Vogelsang,EIC WS, Yale’00 & Pol. HERA WS, DESY’99

HERA 150 pb-1/yrEIC 85 pb-1/day


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Parity Violating Structure Parity Violating Structure Function gFunction g55

• This is also a test

For HERA & EIC

• Experimental signature is a huge asymmetry in detector (neutrino)• Unique measurement• Unpolarized xF3 measurements at HERA in progress• Will access heavy quark distribution in polarized DIS


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Measurement Accuracy PV gMeasurement Accuracy PV g55 at at EICEIC

Assumes: for EIC (LEFT FIGURE)1. Input GS Pol. PDfs2. xF3 measured by then3. 2 fb-1 luminosity4. Makes the case for e+/e- beam

facility

J. Contreras & A. De Roeck, Pol. HERA WS, DESY’99 & EIC WS BNL’01

Assumes for HERA (RIGHT FIGURE)1. Input GS polarized PDFs2. xF3 is measured by then3. 1 fb-1 luminosity4. Both e+/- beams


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Drell Hern Gerasimov Spin Sum Drell Hern Gerasimov Spin Sum RuleRule

• DHG Sum rule:

• At EIC range: GeV few TeV• AT HERA : 10s of GeV 10s TeV

• Although contribution from to the this

sum rule is small, the high behavior is completely unknown and hence theoretically biased in any present measurements at:

Jefferson Lab., MAMI, BNL

S. Bass, A. De Roeck & A. Deshpande, EIC WS, Yale’00

• Inclusive Photo-production measurement• Using electron tagger in EIC -- Q2 ~ 10-6 10-2 GeV2

-- Sqrt(s) ~ 25 85 GeV HERA: -- Q2 ~ 10-6 10-3 GeV2

-- Sqrt(s) ~ 40 250 GeV


22

DGH Spin Sum RuleDGH Spin Sum Rule

(1)+(2)=0.5

(1)+(2)=-0.5

(1)+(4)

(1)+(3)

Contribution from EIC/eRHIC and HERA

S. Bass & A. De Roeck


23

Strange Quark Distributions at Strange Quark Distributions at EICEIC

• After measuring u & d quark polarized distributions…. Turn to s quark (polarized & otherwise)

• Detector with good Particle ID: pion/kaon separation

• Upper Left: statistical errors for kaon related asymmetries shown with A1 inclusive

• Left: Accuracy of strange quark distribution function measurements possible with EIC and HERMES (2003-05) and some theoretical curves on expectations.

E. Kinney & U. Stoesslein, EPIC WS, MIT’01HERA, TESLA-N, ELFE


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TransversityTransversity• Measure helicity flip amplitude =

(x,Q2) quark transversity• Does not mix with gluon

distributions in its QCD evolution• Measure single spin asymmetries

(DIS + p0)• Large acceptance desired |eta|<3.5

Collins/fragmentation function being measured by:

RBRC from e+e- at B-factor at BELLE Expect preliminary results in ’03

M. G. Perdekamp, EIC WS, Yale’00

EIC with 80 pb-1~ 1 day

TESLA-N, ELFE in HERMES Kinematics


25

DVCS/Vector Meson ProductionDVCS/Vector Meson Production

• Hard Exclusive DIS process

• (default) but also vector mesons possible

• Remove a parton & put another back in!

Microsurgery of Baryons!

•Claim: Possible access to skewed or off forward PDFs? Polarized structure: Access to quark orbital angular momentum?

On going theoretical debate… experimental effort just beginning at HERA, Jlab… For ELFE this is the principle motivation

EIC ELFE


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DVCS study for EIC (preliminary)

Q2> 1 GeV2

20<W<95 GeV0.1<|t|<1.0 GeV2

Full curve: all eventsDashed curve: accepted events Q2>1 GeV2: 50K events/fb-1

A. Sandacz, EIC WS, BNL’02D. Hassel, R. Milner

10 x 250 GeV

Deeply Virtual Compton Deeply Virtual Compton ScatteringScattering

DVCS has already been seen at HERA… New Detector Techniques at EICRoman pots a la PP2PP at RHIC


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Future Fixed Target DIS at DESYFuture Fixed Target DIS at DESY• TESLA-N -- Use one (positron) arm of TESLA for polarized fixed target experiment -- Beam energy variable 30-250 GeV -- Large Q2 range compared to present fixed target experiments -- PHYSICS: Transversity distributions, Polarized Gluon Distribution

W.-D. Nowak, Int. WS on Hadron Structure, Trieste, Feb.2002

•Run in parallel with the ee collider experiments

•Will need:

1. Polarized source and injector

2. Experimental hall and short tunnel

3. Beam dump

Detector design considerations:

•Size comparable to COMPASS at CERN

•Good momentum resolution

•Good PID RICH, TRD as well as EMCalorimetry


28

ELFE at DESYELFE at DESY

•ELEF at DESY:

-- Inject electron beam at 30 GeV in modified HERA-e

-- Use HERA as stretcher ring extract high duty factor

-- Measurement goal: Exclusive reactions with high precision

-- PHYSICS: Skewed parton distributions Orbital angular momenta

W.-D. Nowak, Int. WS on Hadron Structure, Trieste, Feb.2002R. Kaiser & D. Ryckbosch, private comm., SPIN2002 at BNL


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Towards EIC at BNL….Towards EIC at BNL….• September 2001: EIC grew out of joining of two communities: 1) polarized eRHIC (ep and eA at RHIC) 10 GeV e X 250 GeV p or 100 GeV A BNL, UCLA, YALE and people from DESY & CERN 2) Electron Poliarized Ion Collider (EPIC) 3-5 GeV e X 30-50 GeV polarized light ions Colorado, IUCF, MIT/Bates, HERMES collaborators

• February 2002: White paper submitted to NSAC Long Range Planning Review Received enthusiastic support as a next R&D project (see: DoE Webpage for Nuclear Physics Long Range Planning)

• Steering Committee: 7 members, one each from BNL, IUCF, LANL, LBL, MIT, UIUC, Yale + Contact person (AD)

• ~20 (~13 US + ~7 non-US) Institutes, ~100 physicists + ~40 accelerator physicists

• See for more details: EIC Web-page at “http://www.bnl.gov/eic” • Annual Meetings: MIT Sep.’01, BNL Feb.’02, BNL(?) May/June’03• Subgroups: Accelerator WG, Physics WG, Detector WG

EPIC + eRHIC = “EIC”


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EIC Layout (present status)EIC Layout (present status)• Proposed by BINP & MIT/Bates• E-ring is ¼ of RHIC ring• Collisions in ONE interaction region• Collision energies 5-10 GeV• Injection linac 2-5 GeV• Lattice based on “superbend”

magnets• Self polarization using Sokolov

Ternov Effect: (14-16 min pol. Time)

• IP12, IP2 and IP4 are possible candidates for collision points

p

e2GeV (5GeV)

2-10 GeV

IP12

IP2

IP4

IP6

IP8

IP10

RHIC

OTHER : Ring with 6 IPS (Yale’00), Linac-Ring (Yale’00), Linac-Re-circulating ring (BNL’01)

PHENIX

BRAHMSPP2PP

PHOBOS

STAR

EMPTY

CAD/RFEMPTY


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A Detector for EICA Detector for EIC A “4 A “4” ” DetectorDetector

• Scattered electrons to measure kinematics of DIS• Scattered electrons at small (~zero degrees) to tag photo

production• Central hadronic final state for kinematics, jet measurements,

quark flavor tagging, fragmentation studies, particle ID• Central hard photon and particle/vector detection (DVCS)• ~Zero angle photon measurement to control radiative

corrections and in e-A physics to tag nuclear de-excitations• Missing ET for neutrino final states (W decays)• Forward tagging for 1) nuclear fragments, 2) diffractive

physics• DETECTOR DEVELOPMENT JUST BEGINNING: Invitation to Join! -- Some early effort (W. Krasny & J. Chwastowski, Yale 00 WS) -- New effort for modified EIC ring lattice to begin BNL/MIT/UIUC/+YOU!

• EIC will provide: 1) Variable beam energies 2) different hadronic species, some of them polarized, 3) high luminosity


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A time line for EIC…A time line for EIC…

“Predictions are very difficult to make, especially when they are about the future” --- Albert E.

• Proposal by 2004-2005• Expected formal approval 2005-6 Long Range Review• R&D money could start for hardware 2007• Construction of IR and Detector begin 2007-2008• 3-5 years for staged detector and IR construction

without interfering with the RHIC running• First collisions (2010-2011)???

If any one knows how to do this earlier… -- I am listening.


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RHIC Accelerator ComplexRHIC Accelerator Complex

BRAHMS & PP2PP (p)

STAR (p)

PHENIX (p)

AGS

LINACBOOSTER

Pol. Proton Source500 A, 300 s

GeVs

L

50050

onPolarizati%70

cms102 2132max

Spin Rotators

Partial Siberian Snake

Siberian Snakes

200 MeV Polarimeter AGS Internal PolarimeterRf Dipoles

RHIC pC Polarimeters

Absolute Polarimeter (H jet)

2 1011 Pol. Protons / Bunch = 20 mm mrad

RHIC accelerates heavy ions to 100 GeV/A and polarized protons to 250 GeV


34

RHIC PolarimetryRHIC Polarimetry

Beam’s View

Si #1

Si #2

Si #4Si #3

left right

down

up

Si #5

Si #6

Carbon filament target (5g/cm2) in the RHIC beam

Measure recoil carbon ions at q~90º

100 keV < Ecarbon< 1 MeVWave-Form Digitizer +FPGA high counting rates (~0.5

MHz) scaler measurement A ~ 310-4 in ~1 minute.

Carbon

ADC values

Arr

ival

tim

e (n

s)

E950 Experiment at AGS (1999) RHIC Polarimetry Now

BNL,Kyoto,RBRC,RIKEN,Yale


35

Siberian SnakesSiberian Snakes

STARPHENIX

AGSLINAC

RHIC

Effect of depolarizing resonances averaged out by rotating spin by large angles on each turn

4 helical dipoles S. snake2 snakes in each ring -- axes orthogonal to each other

BNL, RBRC, RIKEN


36

Successful Operation of the Successful Operation of the SnakeSnake

• Injection with Spin Flipped: Asymmetry Flipped

• Adiabatically Snake on: Horizontal polarization

• Accelerate equivalent to 180o rotation: 180o rotated

Successful SingleSnake Operation !

Blue Ring, Run 1 (2000-2001)


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Polarization in Run 2 (January 2002)Polarization in Run 2 (January 2002)

Yellow Ring Blue Ring


38

Why low polarization? Why low polarization? AGS! AGS!

10% 20% 30%

PAGS

PRHIC SourceImprovement

AGS power generator failure½ ramp up speed2x resonance effect

New AGSSNAKE2004-5

Ramp upSpead

Injection1st Year


39

Machine Performance Machine Performance ExpectationsExpectations

RUN #proton/bunch

[x109]#bunch Beta*

(m)

Emittance

(m)

Luminosity

1030 cm-2s-1

Pol.

(%)

2001-

2002

70 55 3 25 1.8 15-25

2002-2003

100 112 1 25 16 45-55

2005- ? 112 1 ? ? 70-80

Design 200 112 1 20 80 70


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A Case for Polarized Colliders: A Case for Polarized Colliders: Excellent!Excellent!

• The polarized EIC and HERA for e-N scattering will enable the polarized DIS studies of nucleons in a completely new x-Q2

-- A robust physics program exists with pros and cons w.r.t. high luminosity of EIC and higher CM energy of HERA

• If we are lucky: HERA II finds Physics Beyond SM, polarized HERA will be imperative to understand the chiral properties of the object(!)

-- Polarized THERA program will be concentrated around this…

• Physics with variable Sqrt(s) at EIC will include in addition: -- inclusive physics in DIS as well as photo-production regime -- semi-inclusive physics with good particle ID -- exclusive physics leading to DVCS, DES and further to GPDs -- study of evolution of any of the pdfs when necessary

• Proof of high energy polarized proton beam is at hand with RHIC Spin

• Primary physics program for TESLA-N/ELFE will limit itself to already explored x-Q2 coverage, but with significantly enhance statistical accuracy with huge luminosities hence allowing detailed studies of exclusive reactions, possibly leading to angular momenta in q and g


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Some spin & Low x/High QSome spin & Low x/High Q22 surprises… surprises…

• Stern & Gehrlach (1921) Space quantization associated with direction

• Goudschmidt & Ulhenbeck (1926): Atomic fine structure & electron spin magnetic moment

• Stern (1933) Proton anomalous magnetic moment 2.79 N

• Kusch(1947) Electron anomalous magnetic moment 1.001190

• Prescott & Yale-SLAC Collaboration (1978) EW interference in polarized e-d DIS, parity non-conservation

• European Muon Collaboration (1989) Spin Crisis/Puzzle

• E704, AGS pp scattering, HERMES (1990s) Transverse spin asymmetries (??)

• RHIC Spin (2001) Transverse spin asymmetries (??)

• Elastic e-p scattering SLAC (1950s) Q2 ~ 1 GeV2 Finite size of the proton

• Inelastic e-p scattering SLAC (1960s) Q2 > 1 GeV2 Parton structure of the proton

• Inelastic -p scattering off p/d/N at CERN (1980s)

Q2 > 1 GeV2 Unpolarized EMC effect, nuclear shadowing?

• Inelastic e-p scattering at HERA/DESY (1990s) Q2 > 1 GeV2

Unexpected rise of F2 at low x Diffraction in e-p

Saturation(??)


42

Thanks…..Thanks…..

• Many people were listed along with their work for various polarized HERA and Electron Ion Collider Workshops….

-- Many more participated but can not be mentioned….

• TESLA-N, ELFE : W.D.Nowak, R. Kaiser, D. Ryckbosch

• EIC Accelerator Issues: V. Ptytsin and the EIC Accelerator group (BNL/MIT-Bates)

• Initial versions of some transparencies shown in this talk were prepared with A. De Roeck(CERN) for previous workshops and presentations for polarized HERA and making the case for EIC

polarized dis with future polarized colliders

Documents

polarized hera

gev2 xmin

tevphysics opportunities

detector physics opportunities

hera thera teslanelfe

ep scattering study

highlow luminosity collisions

new detectorthera teslan