GPDs @ JLab12 & EIC
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Transcript of GPDs @ JLab12 & EIC
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1/ 1/ GPDsGPDs are a are a beautiful/richbeautiful/rich theoretical tool theoretical tool but are very but are very difficultdifficult to access/extract experimentally to access/extract experimentally
2/ Very encouraging first experimental results coming out2/ Very encouraging first experimental results coming outfrom from JLab 6 GeVJLab 6 GeV (and (and HERMESHERMES) where we develop/test ) where we develop/test the analysis techniques the analysis techniques
3/3/ JLab@12 GeV JLab@12 GeV and and EICEIC are the ultimate facilities are the ultimate facilities for a full study/definite extraction of GPDsfor a full study/definite extraction of GPDs
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Cross sections and charge asymmetries measurements (ReT)
Integral of GPDs over x
Beam or target spin asymmetriescontain only ImT,
i.e. GPDs at x = and
1
1
1
1
),,(),,(
~),,(
~ tHidxx
txHPdx
ix
txHT DVCS
p p’
H,E,H,E~ ~x
tx
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= xB/(2-xB)
k = -t/4M2 A =
=ep ep
LU~ sin{F1H + (F1+F2)H +kF2E}d~
Polarized beam, unpolarized target:
H(,t), H(,,t), E(,,t)
Kinematical suppression
~
(BSA)
Unpolarized beam, long. pol. target:
UL~ sin{F1H+(F1+F2)(H + … }d~ H, H
~
(l)TSA
Unpolarized beam, trans. pol. target:
UT~ sin{k(F2H – F1E) + …. }d H, E
(t)TSA
Global (polarized and unpolarized) data analysis,Global (polarized and unpolarized) data analysis,X-sec, asym., (p,n), (X-sec, asym., (p,n), (,M), to extract the GPDs,M), to extract the GPDs
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1/ 1/ GPDsGPDs are a are a beautiful/richbeautiful/rich theoretical tool theoretical tool but are very but are very difficultdifficult to access/extract experimentally to access/extract experimentally
2/ Very encouraging first experimental results coming out2/ Very encouraging first experimental results coming outfrom from JLab 6 GeVJLab 6 GeV (and (and HERMESHERMES) where we develop/test ) where we develop/test the analysis techniques the analysis techniques
3/3/ JLab@12 GeV JLab@12 GeV and and EICEIC are the ultimate facilities are the ultimate facilities for a full study/definite extractionfor a full study/definite extraction
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Difference of polarized cross sections
Unpolarized cross sectionsUnpolarized cross sections
Thesis C. Muñoz-Camacho (Saclay), A. Camsonne (Clermont) : arXiv:nucl-ex/0607029
Hall A 6 GeV DVCS Bethe-Heitler
ep ep GPDs
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Twist-2 terms dominate the cross section and are independent of Q2 in the explored kinematical domain The contribution to the cross section of twist-3 terms is small and is independent of Q2 in the limit of error bars
Strong indication in favor of factorization already from Q2=2 GeV2
in the valence region
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0.09<-t<0.2 0.2<-t<0.4 0.4<-t<0.6
0.6<-t<1 1<-t<1.5 1.5<-t<2
PRELIMINARY
Thesis H.S. Jo (Orsay)
DVCS + BH cross sections andDVCS + BH cross sections andcomparison to theoritical BHcomparison to theoritical BH
Hall B 6 GeV
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E03-106 n-DVCSP.Y. Bertin, C.E. Hyde-Wright, F. Sabatié, E. Voutier
et al.
Thesis M. Mazouz (Grenoble)
PRELIMINARY
en en
Strong sensitivity to E
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1/ 1/ GPDsGPDs are a are a beautiful/richbeautiful/rich theoretical tool theoretical tool but are very but are very difficultdifficult to access/extract experimentally to access/extract experimentally
2/ Very encouraging first experimental results coming out2/ Very encouraging first experimental results coming outfrom from JLab 6 GeVJLab 6 GeV (and (and HERMESHERMES) where we develop/test ) where we develop/test the analysis techniques the analysis techniques
3/3/ JLab@12 GeV JLab@12 GeV and and EICEIC are the ultimate facilities are the ultimate facilities for a full study/definite extractionfor a full study/definite extraction
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JLab 12 GeV : valence quarks region
EIC : gluons and sea quarksregion
Large phase space Large phase space ((,t,Q,t,Q22))
High luminosityHigh luminosity
Valence regionValence region
Sea/gluon regionSea/gluon region
JLab12JLab12
EICEIC
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IC in standard position – 80 days – 10^35 Lum – VGG model
Beam asymmetry@12 GeVBeam asymmetry@12 GeV
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ALU
<xB> =0.2<Q2> = 3.3 GeV2
<-t> = 0.45 GeV2
<xB> =0.2<Q2> = 3.3 GeV2
<Q2> =3.3 GeV2
<-t> = 0.45 GeV2
<xB> =0.36<Q2> = 4.1 GeV2
<-t> = 0.52 GeV2
<xB> =0.36<Q2> = 4.1 GeV2
<Q2> =4.1 GeV2
<-t> = 0.52 GeV2
BSA
TSA
Sensitivity to GPD modelsSensitivity to GPD models
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2 (Im(AB*))/ T
t/4m2) - ReUT
Asymmetry depends linearly on the GPD E, which enters Ji’s sum rule.
A ~ (2Hu +Hd)
B ~ (2Eu + Ed)0
Goeke, Polyakov,Vdh, (2001)
0
Q2=5 GeV2
L=1035cm-2s-1
2000hrs
Exclusive Exclusive 00 prod. with transversely polarized target prod. with transversely polarized target
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GPDs depend on3 variables GPDs depend on3 variables (x,(x,,t),t) and only and only 22 are are experimentally accessible experimentally accessible ((,t),t) : convolution issue and: convolution issue andinevitable model dependenceinevitable model dependence
Very encouraging first experimental results coming outVery encouraging first experimental results coming outfrom JLab 6 GeV (from JLab 6 GeV (twist-2twist-2 dominance, first constraints dominance, first constraints on GPD models, first on GPD models, first –very preliminary-–very preliminary- extractions of extractions ofJJuu, , JJdd,…),…)
Need to measure over a large phase space several Need to measure over a large phase space several channelschannelsand and observablesobservables which mutually constrain the GPDs which mutually constrain the GPDs parametrizationsparametrizations
SummarySummary
Ultimate facilities : Ultimate facilities : JLab@12 GeVJLab@12 GeV ( (valence quarkvalence quark region) region)and and EICEIC ( (gluonsgluons and and sea quarkssea quarks region) region)