gpds @ jlab12 & eic
DESCRIPTION
GPDs @ JLab12 & EIC. QCD workshop, 15/12/06. 1/ GPDs are a beautiful/rich theoretical tool but are very difficult to access/extract experimentally. 2/ Very encouraging first experimental results coming out from JLab 6 GeV (and HERMES ) where we develop/test - PowerPoint PPT PresentationTRANSCRIPT
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
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
= 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
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
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
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
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
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
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
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
IC in standard position – 80 days – 10^35 Lum – VGG model
Beam asymmetry@12 GeVBeam asymmetry@12 GeV
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
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
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)