P. Lenisa 1

M. Contalbrigo, A. Drago and M. Contalbrigo, A. Drago and Paolo LenisaPaolo LenisaUniversità di Ferrara and INFN - ITALYUniversità di Ferrara and INFN - ITALY

XIV International Workshop on Deep Inelastic Scattering (DIS 2006)KEK – April 20-24 2006

TransverseTransverse-sea measurements at -sea measurements at JPARCJPARC

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OutlineOutline

•Introduction

•Double spin asymmetries in DY at JPARC

•JPARC vs PAX at GSI

•Conclusions

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IntroductionIntroduction

•Helicity distributions of valence quarks (rather) well known

•Helicity distributions of polarized sea poorly known

•Fits:

•Models agree with , disagree on the size

0,0 uu

0u

•Situation more confused for transversity

•Models agree within a factor 2 for

•Even worse for

•Models disagree both on sign of and size.

uh1

uh1

uh1

JPARC: 50 GeV polarized p beam on polarized target:

Double-polarized DY production sensitive to polarized sea (u).

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Longitudinal seaLongitudinal sea

M. Glück et al.Phys. Rev. D 63 (2001) 094005

Models:

ouu CDMCQSM

ux

ux

dx

dx

sx

Gx

Val. scenario: 0;

),(

),(2

2

ss

d

u

xu

xd

ssdduuQxq seasea ),( 2

Std. scenario:

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Val. scenario

Std. scenarioxF=x1-x2

q q

q q

LLDYLL

xqxqxqxqe

xqxqxqxqeaA

21212

21212

Double-polarized longitudinal Drell-Double-polarized longitudinal Drell-YanYan

•Large asymmetries expected at JPARC energy

•Test of the assumptions of the fits

•Not conclusive distinction between the models

GeVs 10Models:

oAA CDMCQSM

LLLL

D. Dutta et al.LoI for JPARC

xB

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Transverse seaTransverse sea

M. Wakamatsu and T. KubotaPhys. Rev. D 63 (1999) 034020

V. Barone, T. Calarco and A. Drago

Phys. Lett. B 390 (1997) 287

CDM CQSM

•The two models predict different sign for (with comparable amplitude).

uh1

dh1

),(1 initu

Qxh),(

1 evoluQxh

),(1 initd

Qxh),(

1 evoldQxh

uh1

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CDM

(~CQSM)

2

1

q i

q qqqqqTT

DYTT

xqxqxqxqe

xhxhxhxheaA

21212

211121112

Double-polarized transverse Drell-Double-polarized transverse Drell-YanYan

•Aymmetry is large at JPARC energy (> 0.1)

•Sign of the asymmetry will distinguish between the two models.

•It will give indications about calculation of sea distributions.

),(),( 2201 0QxqQxh

q

),(),( 2201 0QxqQxh

q

1

2Asymmetries evoluted with the

assumptions:GeVs 10

D. Dutta et al.LoI for JPARC

xB

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Higher energy p-p machineHigher energy p-p machine

GeVs 100

V. Barone, T. Calarco and A. Drago

Phys. Rev. D 56 (1997) 527

•s •Asymmetry

•ALL>ATT

•sJPARC ideal

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Model DY Asymmetries

Fit symm.sea +ALL< 0 ATT< 0

CQSM ALL> 0 ATT< 0

CDM ALL> 0 ATT> 0

),(),( 2201 0QxqQxh

q

Sign of the asymmetries discriminates fits assumption and models

•Sinergy with double polarized p-pbar experiment

•Transversity extraction problematic with only p-p scattering

•Product of two unknown function.

What about extraction?

•Summary:

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FFacilty for acilty for AAntiproton and ntiproton and IIon on RResearchesearch (GSI, Darmstadt, Germany)(GSI, Darmstadt, Germany)

-Proton linac (injector)-2 synchrotons (30 GeV p)-A number of storage rings Parallel beams operation

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PAX@GSIPAX@GSI•Production of polarized antiprotons by spin filtering

(Tests at COSY (Jülich) and AD (CERN))

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Hadronic Interaction: Longitudinal CaseHadronic Interaction: Longitudinal Case Beam PolarizationBeam Polarization

Model D: V. Mull, K. Holinde, Phys. Rev. C 51, 2360 (1995)

Model A: T. Hippchen et al., Phys. Rev. C 44, 1323

(1991)

50 100 150 200 250 T (MeV) 50 100 150 200 T (MeV)

0.05

0.10

0.15

0.20

P

0.05

0.10

0.15

0.20

P

2 beam lifetimesΨacc=10-50 mrad

3 beam lifetimesΨacc=20 mrad

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PAX@GSIPAX@GSI

Asymmetric collider:polarized antiprotons in HESR (p=15 GeV/c)polarized protons in CSR (p=3.5 GeV/c)√s=14.5

•Production of polarized antiprotons by spin filtering

(Tests at COSY (Jülich) and AD (CERN))

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h1 from pbar-p Drell-Yan at PAX (GSI)

Anselmino et al. PLB 594,97

(2004)

)()(

)()(ˆ

)()()()(

)()()()(ˆ

21

2111

21212

211121112

xuxu

xhxha

xqxqxqxqe

xhxhxhxheaA uu

TT

q q

q qqqqq

TTTT

10 % precision on the h1u (x) in the valence region

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PAXPAX

DY events distributionDY events distribution

PAX+JPARC complete mapping of transversity

JPARCJPARC

Extraction of h1u for x>0.05x1=x2 ATTh1u2

Measurement of h1u for 0.15<x<0.5

M2/s=x1x2~0.01-0.3

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ConclusionsConclusions

•Large asymmetries (> 0.10) for d. pol. DY at JPARC

•Discrimination between fits assumption and models

•Look at the signs of ALL and ATT

•Will teach how to calculate antiquark distributions

•High complementarity between JPARC and PAX@GSI

•Complete mapping of transv. valence + sea polarization

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V. Barone et al.hep-ph/0306225