International Workshop on Transverse Polarisation Phenomena in Hard Processes

Como, September 7- 10, 2005

Marco MaggioraDipartimento di Fisica ``A. Avogadro'' and INFN - Torino, Italy

SINGLE AND DOUBLE SPIN INTERACTIONS AT GSIN - N

Introduction

• SIS300 @ GSI: HESR as (asym) collider:

• A complete description of nucleonic structure requires:

@ leading twist and @ NLO ( kT dependence)

• Physics objectives: Drell-Yan di-lepton production

spin observables in hadron production

electromagnetic form factors

quark and gluon distribution functions

quark fragmentation functions

p) GeV 200 :PAC ( GeV80 22s

3110 L

f1, g1 studied for decades: h1 essentially unknown

)kx,(fkd)x(f T1T2

1

Twist-2 PDFs

κT-dependent Parton Distributions

Distribution functions

Chirality

even odd

Twist-2

U

L

T

f1

g1

, h1,

h1

h1L

h1T

f 1T

g1T

Why Drell Yan?Asymmetries depend on PD only (SIDIS→convolution with QFF)

Why ?Each valence quark can contribuite to the diagram

Kinematics

p

q2P

Mx

1

2

1

xxx 21F

q2P

Mx

2

2

2

s

Mxxτ

2

21

0QM 22

plenty of (single) spin effects3 planes: plane to polarisation vectors

plane plane

*γp

*γ

Drell-Yan Di-Lepton Production — Xμμpp

Scaling:

Full x1,x2 range .

needed

[1] Anassontzis et al., Phys. Rev. D38 (1988) 1377

Drell-Yan Di-Lepton Production Xμμpp

a 2

a1

a2

a1

a2a

212

2

F2

2

)(x)f(xf)(x)f(xfexx

1

s9M

π4α

dxdM

σd

0,1τ

s

1

dxτd

σd

F

2

2Gev 20080s 1

Xμμppnb 0.123.0σ

Phase space for Drell-Yan processes

15 GeV/c

40÷100 GeV/c

= const: hyperbolaexF = const: diagonal

PANDA

ASSIA/PAX(SIS300 or HESR)

[1]A. Bianconi and M. Radici, Phys. Rev. D71 (2005) 074014

2p

[1] GeV/c 9M4 target,p fixed aon GeV 40E with ev K04

Uncorrelated quark helicities access chirally-odd functions

TRANSVERSITY

Ideal because:

• h1 not to be unfolded with fragmentation functions

• chirally odd functionsnot suppressed (like in DIS)

Drell-Yan Asymmetries — Xμμpp

a 2

a

11

a

1

2

a

a 2

a

11

a

1

2

a

LL )()(

)()(

xfxfexgxge

A

a 2

a

11

a

1

2

a

a 2

a

11

a

1

2

a2

2

TT )()(

)()(

θcos1

θcos2φsin

xfxfexhxheA

a 2

a

11

a

1

2

a

a 2

a

11

a

L2

a

T21

a

1

2

a

22LT )()(

)()(1-)()(

Q

M

θcos1

cosφ 2sin2θ

xfxfexhxhxxgxxge

A

To be corrected for:

pp PfP

1

Collins-Soper frame: [1]Phys. Rev. D16 (1977) 2219.

Drell-Yan Asymmetries — Xμμpp

RICH energies: small x1 and/or x2

evolution much slower[1] than Δq(x,Q2) and q(x,Q2) at small x

ATT @ RICH very small, smaller would help[1]

GeV 100s 100M2 -210τ

)Q(x,h 2a1

s

[1]Barone, Colarco and Drago, Phys.Rev. D56 (1997) 527.

220 GeV 0.23Q

22 GeV 25Q

Drell-Yan Asymmetries — Xμμpp

ATT still small @ large and M2 due to slow evolution of

Large ATT expected[1] for and M2 not too large and τ not too small

)Q(x,h 2a1s

[1]M. Anselmino et al., Phys. Lett. B594 (2004) 97.

2GeV 30s

2GeV 45s

q2

p1

p2q

q2

p1q1

p1q

2q

TT x large

q2

p1

p2

p1

p2q

q2

p1q1

pq12

pq11

p1q

2q

TTTT )x(q)x(qe

)x(h)x(he

a

)x(q)x(q)x(q)x(qe

)x(h)x(h)x(h)x(he

aA

220

20

201q

[1] GeV/c 23.0Q @ )Qx,(q)Qx,(h Assuming

s

HESR:

ATT direct accessto valence quark h1

)x(h )x(h 21q11q VV

0.3 M M

GeV 4530s 2J

2

2max

Drell-Yan Asymmetries — Xμμpp

θcos2φsin

2

νθcosφμsinθλcos1

3λ

1

4π

3

dΩ

dσ

σ

1 222

NLO pQCD: λ 1, 0, υ 0Experimental data [1]: υ 30 %

[1] J.S.Conway et al., Phys. Rev. D39 (1989) 92.

υ involves transverse spin effects at leading twist [2]:

cos2φ contribution to angular distribution provide:

[2] D. Boer et al., Phys. Rev. D60 (1999) 014012.

)κ,(xh )κ(xh 211

22,1

Di-Lepton Rest Frame

Drell-Yan Asymmetries — Xμμpp

Conway et al, Phys. Rev. D39 (1989) 92

Angular distribution in CS frame

E615 @ Fermilab

-N +-X @ 252 GeV/c

-0.6 < cos < 0.6

4 < M < 8.5 GeV/c2

• cut on PT selects asymmetry• 30% asymmetry observed for -

Angular distributions for and Angular distributions for and -- —— -N, N @ 125 GeV/cp p

E537 @ FermilabAnassontzis et al., Phys. Rev. D38 (1988) 1377

•

cosd

dvs cos

• d

dvs

p

pπ

π

)φθsin(φsinSρθcos2φsin

2

νθcos1

dΩ

dσ

σ

11S

21T

22

a 2a

11a

12a

a 2a11

a122

a11

a11

2a

22

S1TT )(x)f(xfe

)(x)h(xhx)(x)f(xfxe

Q

M

θcos1

)φθsin(φ2sin2SA 1

λ 1, 0

Even unpolarised beam on polarised p, or polarised on unpolarised p

are powerful tools to investigate кT dependence of QDF

D. Boer et al., Phys. Rev. D60 (1999) 014012.

pp

Drell-Yan Asymmetries — Xμμpp

[1]A. Bianconi and M. Radici, Phys. Rev. D71 (2005) 074014

GeV/c 1q ,GeV/c 9M4 target,fixed aon GeV 40E with ev K04 T2

p[1]

GeV/c 1q ,GeV/c 9M4 GeV, 3.3Eon GeV 15E with ev K8 T2

pp[1]

s ~ 80 GeV2

small asymmetries different dependencies

cannot be resolved

s ~ 200 GeV2

bigger asymmetries different dependencies

can be partially resolved

2

21

21 2xxf

xh

2

21

21 12 xxf

xh

Drell-Yan Asymmetries — Xμμpp

[1]A. Bianconi and M. Radici, hep-ph/0504261 Phys. Rev. D in press.

GeV/c 1q ,GeV/c 9M4 GeV, 3.3Eon GeV 15E with ev K8 T2

pp[1]

s ~ 200 GeV2

different dependencies can be partially resolved

1

21

21 xf

xh

0

21

21 xf

xh

Drell-Yan Asymmetries — Xμμpp

pxxf

xh

21

21

pxxf

xh 1

21

21

[1]H. Shimizu et al., Phys. Rev. D71 (2005) 114007

2GeV 30s GeV 5.14s

At higher energy ( s ~ 200 GeV2) perturbative corrections[1] are sensibly smaller

in the safe region

Drell-Yan Asymmetries — Xμμpp

Hyperon production Spin Asymmetries

production in unpolarised pp-collision:

Several theoretical models:• Static SU(6) + spin dependence in parton fragmentation/recombination [1-3]

• pQCD spin and transverse momentum of hadrons in fragmentation [4]

[1] T.A.DeGrand et al.,Phys. Rev. D23 (1981) 1227.[2] B. Andersoon et al., Phys. Lett. B85 (1979) 417. [3] W.G.D.Dharmaratna, Phys. Rev. D41 (1990) 1731.[4] M. Anselmino et al.,Phys. Rev. D63 (2001) 054029.

φ)(Nφ)(N

φ)(N-φ)(N

θcosP

1A

BN

φcosAP1PφcosAP1Pφcos2P

1D NBNB

BNN

Analysing power

Depolarisation

Key to distinguish between these models

Data available for DNN:

3.67 GeV/c DNN < 0

13.3 -18.5 GeV/c DNN ~ 0

200 GeV/c DNN > 0

DNN @ 100 GeV/c MISSING

Hyperon production Spin Asymmetries

Polarised target: .

Transverse target polarisation

Existing data: PS185 (LEAR) [2]

[1] K.D. Paschke et al., Phys. Lett. B495 (2000) 49.

[2] PS185 Collaboration, K.D: Paschke et al., Nucl. Phys. A692 (2001) 55.

ΛΛpp

[1] complete determination of the spin structure of reaction

Models account correctly for cross sections.

Models do not account for or .

NEW DATA NEEDED

ΛNND Λ

NNK

Transverse Single Spin Asymmetries

dσdσ

dσdσAN πXpp πXpp

• Production @ large xF originate from valence quark: +: AN > 0 ; -: AN < 0 Correlated with expected u and d-quark polarisation

• AN similar for ranging from 6.6 up to 200 GeV

AN related to fundamental properties of quark distribution/fragmentation

New experiment with polarised nucleon target, and in a new kinematical region:

• new data available

• vs

• DY-SSA (AT) possible only @ RICH, p↑p-scattering:

@ smaller s >> @ large s

p

πXpp N,A

DYppσ DY

ppσ

s

πXpp N,A

E704 Tevatron FNAL 200GeV/c

Electromagnetic form-factors

FF in TL region ( ) related to nucleon structure

New information with respect to SL FF (eN-scattering)

TL - FF:

:

• low statistic• no polarisation phenomena

μμpp •

• analysing power

dΩ

dσalternative way to FF

eepp

angular distribution separation of electric and magnetic FFanalysing power transverse polarisation of p↑ leads

to non zero analysing power

Different prediction for models well reproducing SL data

Beam and Target

UNILACSIS

FRS

ESR

HESRSuperFRS

NESR

CR

RESR FLAIR

SIS 100 Tm

SIS 300 Tm

U: 35 AGeV

p: 90 GeV

Key features:Generation of intense, high-quality secondary beams of rare isotopes and antiprotons.Two rings: simultaneous beams.

Main goal: spin physics nucleon structure DY di-lepton production distribution functions Spin observables in hadron production fragmentation Electromagnetic form factors

Ideal tools: polarised , polarised p

Key issue: s (> 80 Gev2, PAC: 200 GeV2), luminosity ( > 1031 )

Summary

Slow extraction from SIS300

polarised target, both PL and PT

minimal PANDA interactions

HESR (collider)

no diluition factor

pp

MORE WORK, SIMULATIONS NEEDEDDISCUSSION WITH GSI MANAGEMENT:

• what is feasable ▪ physics iussues

KEY POINT: how much and how long can we polarise ?

p

p

Question time

vector couplings

same spinor structure

Drell-Yan Di-Lepton Production XμμΨJpp

vγuM

1uγv μ

2μvγug

MMM

1uγvg μV

lJ

2J

2μV

q

i

aa*γ

TT

J

TT

)x(u)x(u

)x(h)x(ha

)x(q)x(qg

)x(h)x(hg

21

21u11u

x, xlarge TT

q 21Vq

q 21q11qVqJ

TT21

A

Measure ATT in J/Ψ resonance

region in reactions

Cross section large enough in this region

~ 160 ev/day , <x>≈0.4

2

1u

TT

TT

2J

F u(x)

)x(h

a

A

s

M x, 0x

pp

contrib.) (cont. GeV 10 6.9dMdM

d

scm 10 1.5 GeV 45s 16

6

2-7-22

-1 -2312

L

days 240 %90P %5P

NPP

1δ 11%δ

pp

ppATT

Beam and Target

NH3 10g/cm3 : 2 x 10cm cells with opposite polarisation

GSI modifications:• extraction SIS100 → SIS300 or injection CR → SIS300 • slow extraction SIS300 → beamline adapted to • experimental area adapted to handle expected radiation from

GeV40Ep

17

3f 85.0PT

1231723 sm105.1105.11061017

3L

sp102 7

Alternative GSI solution

• Luminosity comparable to external target → KEY IUSSUE • dilution factor f~1• difficult to achieve polarisation Pp ~ 0.85• required achievable with present HESR performances (15 GeV/c)• only transverse asymmetries can be measured• p↑-beam required polarisation proton source and acceleration scheme preserving polarisation• no additional beam extraction lines needed• PHYSICS PARTIALLY FEASIBLE @ PANDA AS WELL

HESR collider polarised p and beams p

s

GeV/c15 Pp