Future Opportunities at an Electron-Ion Collider Oleg Eyser Brookhaven National Laboratory.
Studies of e+A physics at an Electron-Ion Collider
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Transcript of Studies of e+A physics at an Electron-Ion Collider
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Studies of e+A physics at an Electron-Ion Collider
Liang ZhengOn behalf of the BNL EIC Science Task Force
Brookhaven National LabInstitute of Particle Physics, Central China Normal
University
Division of Nuclear PhysicsAmerican Physical Society October 23-26, 2013Newport News, VA
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DNP 2013, Liang Zheng 2
Overview• EIC eA physics program– Nuclear PDF• Nuclei F2/FL
– Nuclear Imaging• Coherent t distribution in diffraction
– Saturation• Inclusive diffraction• Dihadron correlation
– Parton propagation and hadronization in nuclear medium
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Explore the small x regime• Gluons dominate at small x
– 99% of proton mass accounted by QCD interaction
– Gluon PDF grows explosively at small x
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Must be tamed at some point
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Explore the small x regime• Gluons dominate at small x
– 99% of proton mass accounted by QCD interaction
– Gluon PDF grows explosively at small x
• Nonlinear evolution like BK alternative to DGLAP, BFKL due to gluon recombination.
• Saturation regime, Q2<<Q2
s(x)
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Nuclear amplification
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•Gluon density scales as nuclear size
•Effective x much smaller in a nuclei
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EIC eA kinematics coverage
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• Largely extend current reach
• Possible to explore the saturation regime
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Diffractive cross section
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• σdiff/σtot 15% at HERA, predicted 25-40% in eA
• σdiff ~ g(x,Q2)2
Rapidity gap: Signature of a diffractive event.
Color-neutral exchange
t=(p-p’)2
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Diffractive cross section
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• Significant difference between saturation and non-saturation
• Strong discrimination power within a few months of running.
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Dihadron correlation
• Back to back hadron pairs decorrelate
• Strong suppression at away side predicted by saturation
• Probe nuclei in kT space.2013/10/25
Xiao, Dominguez, Yuan 2011/2012
y=0.7zh1 = zh2 = 0.3p1T>2GeV1GeV < p2T < p1T
trigger
associateDf
transverse plane
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Dihadron correlation: non-saturation
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ep/eAu 20x100 GeV0.6<y<0.81 <Q2<2 GeV2
pt1>2 GeV, 1 GeV<pt2<pt10.2<z1,z2<0.42559 < ν < 3412 GeV<xbj>=2.59x10-4
<xg>=3.42x10-2
Charged particlesNuclear effect:• nPDF EPS09• Cold nuclear medium energy loss
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Dihadron correlation: saturation• Constrain sat/nosat models a lot with limited
statistics of 1fb-1.• Strong suppression can not be reproduced by the
nosat model.
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Summary• Key eA measurements at EIC:
– Ratio of diffractive cross section to total, “day one” measurement
– Dihadron correlation in ep/eA, mark out the saturation region with a low luminosity requirement and ep baseline
– More details :• arXiv:1212.1701 EIC White paper• wiki.bnl.gov/eic/index.php/Main_Page
• What can we learn from this– Understand the collective dynamics of
gluons– Investigate inner landscape of a nuclei– Provide initial state input to pA/AA
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Back up
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Structure functions
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eAu:5x50 2 fb-1
5x75 4 fb-1
5x100 4 fb-1
Running combined 6 months total (50% eff)
Systematics-error dominated
Sensitive to gluons
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Diffraction
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Exclusive Vector meson productionCoherent: nuclei intactIncoherent: break up
Finding the source
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eic-tf-meeting 16
10x100 GeVLc = z0.35(1-z) ν y = 0.3, z = 0.3, ν = 640 GeV, Lc = 420 fmy = 0.7, z = 0.3, ν = 1492 GeV, Lc = 979fm
charged pionz>0.1, ν>6 GeV, xFeynman>0, pT>0.1 GeV
Where we are
2013/9/19
Dihadron correlation at an EIC
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eic-tf-meeting 172013/9/19
Kinematics coverage in the Dihadron correlation at an EIC
Qs2 for Au
Qs2 for Ca
Qs2 for
proton
10x100
20x100
Black box:0.6<y<0.8Red box:0.25<y<0.35
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eic-tf-meeting 182013/9/19
Dihadron correlation in different kinematics bins (no sat)10x100 GeV
1fb-1
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eic-tf-meeting 192013/9/19
10x100 GeV 1fb-1
Dihadron correlation in different kinematics bins (sat)