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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