1. Transverse-sea measurements at JPARC
M. Contalbrigo, A. Drago and Paolo Lenisa
Università di Ferrara and INFN - ITALY
XIV International Workshop on Deep Inelastic Scattering (DIS 2006)
KEK – April
P. Lenisa

2. Outline Introduction Double spin asymmetries in DY at JPARC
JPARC vs PAX at GSI
Conclusions
P. Lenisa

3. Double-polarized DY production sensitive to polarized sea (u).
Introduction
Helicity distributions of valence quarks (rather) well known
Helicity distributions of polarized sea poorly known
Fits:
Models agree with , disagree on the size
Situation more confused for transversity
Models agree within a factor 2 for
Even worse for
Models disagree both on sign of and size.
JPARC: 50 GeV polarized p beam on polarized target:
Double-polarized DY production sensitive to polarized sea (u).
P. Lenisa

4. Longitudinal sea Val. scenario: Std. scenario: Models: M. Glück et al.
Phys. Rev. D 63 (2001)
P. Lenisa

5. Double-polarized longitudinal Drell-Yan
Models:
Val. scenario
Std. scenario
xF=x1-x2
D. Dutta et al.
LoI for JPARC xB
Large asymmetries expected at JPARC energy
Test of the assumptions of the fits
Not conclusive distinction between the models
P. Lenisa

6. Transverse sea CQSM CDM
V. Barone, T. Calarco and A. Drago
Phys. Lett. B 390 (1997) 287
M. Wakamatsu and T. Kubota
Phys. Rev. D 63 (1999)
The two models predict different sign for (with comparable amplitude).
P. Lenisa

7. Double-polarized transverse Drell-Yan1 2
Asymmetries evoluted with the assumptions:
CDM 1
D. Dutta et al.
LoI for JPARC xB 2
(~CQSM)
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.
P. Lenisa

8. Higher energy p-p machine
V. Barone, T. Calarco and A. Drago
Phys. Rev. D 56 (1997) 527
s 
Asymmetry 
ALL>ATT
sJPARC ideal
P. Lenisa

9. Sign of the asymmetries discriminates fits assumption and models
Summary:
Model
DY Asymmetries
Fit symm.sea +
ALL< 0
ATT< 0
CQSM
ALL> 0
CDM
ATT> 0
Sign of the asymmetries discriminates fits assumption and models
Transversity extraction problematic with only p-p scattering
Product of two unknown function.
What about extraction?
Sinergy with double polarized p-pbar experiment
P. Lenisa

10. Facilty for Antiproton and Ion Research (GSI, Darmstadt, Germany)
Proton linac (injector)
2 synchrotons (30 GeV p)
A number of storage rings
 Parallel beams operation
P. Lenisa

11. PAX@GSI Production of polarized antiprotons by spin filtering
(Tests at COSY (Jülich) and AD (CERN))
P. Lenisa

12. Hadronic Interaction: Longitudinal Case Beam 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)
0.05
0.10
0.15
0.20 P
3 beam lifetimes
Ψacc=20 mrad
2 beam lifetimes
Ψacc=10-50 mrad
P. Lenisa

13. PAX@GSI Asymmetric collider:
Production of polarized antiprotons by spin filtering
(Tests at COSY (Jülich) and AD (CERN))
Asymmetric collider:
polarized antiprotons in HESR (p=15 GeV/c)
polarized protons in CSR (p=3.5 GeV/c)
√s=14.5
P. Lenisa

14. h1 from pbar-p Drell-Yan at PAX (GSI)
Anselmino et al.
PLB 594,97 (2004)
10 % precision on the h1u (x) in the valence region
P. Lenisa

15. DY events distribution
PAX
JPARC
Extraction of h1u for x>0.05
x1=x2 ATTh1u2
Measurement of h1u for 0.15<x<0.5
M2/s=x1x2~
PAX+JPARC  complete mapping of transversity
P. Lenisa

16. Large asymmetries (> 0.10) for d. pol. DY at JPARC
Conclusions
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
Complete mapping of transv. valence + sea polarization
P. Lenisa

17. P. Lenisa

18. V. Barone et al.
hep-ph/
P. Lenisa