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Studies of e+A physics at an Electron-Ion Collider

Division of Nuclear Physics American Physical Society October 23-26, 2013 Newport News, VA. Studies of e+A physics at an Electron-Ion Collider. Liang Zheng On behalf of the BNL EIC Science Task Force Brookhaven National Lab

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Studies of e+A physics at an Electron-Ion Collider

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  1. Division of Nuclear Physics American Physical Society October 23-26, 2013 Newport News, VA Studies of e+A physics at an Electron-Ion Collider Liang Zheng On behalf of the BNL EIC Science Task Force Brookhaven National Lab Institute of Particle Physics, Central China Normal University

  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 DNP 2013, Liang Zheng

  3. 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 Must be tamed at some point DNP 2013, Liang Zheng

  4. 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<<Q2s(x) DNP 2013, Liang Zheng

  5. Nuclear amplification • Gluon density scales as nuclear size • Effective x much smaller in a nuclei DNP 2013, Liang Zheng

  6. EIC eA kinematics coverage • Largely extend current reach • Possible to explore the saturation regime DNP 2013, Liang Zheng

  7. Diffractive cross section • σdiff/σtot 15% at HERA, predicted 25-40% in eA • σdiff～g(x,Q2)2 Color-neutral exchange Rapidity gap: Signature of a diffractive event. t=(p-p’)2 DNP 2013, Liang Zheng

  8. Diffractive cross section • Significant difference between saturation and non-saturation • Strong discrimination power within a few months of running. DNP 2013, Liang Zheng

  9. Dihadron correlation Xiao, Dominguez, Yuan 2011/2012 • Back to back hadron pairs decorrelate • Strong suppression at away side predicted by saturation • Probe nuclei in kT space. trigger y=0.7 zh1 = zh2 = 0.3 p1T>2GeV 1GeV < p2T < p1T transverse plane Df associate DNP 2013, Liang Zheng

  10. Dihadron correlation: non-saturation ep/eAu 20x100 GeV 0.6<y<0.8 1 <Q2<2 GeV2 pt1>2 GeV, 1 GeV<pt2<pt1 0.2<z1,z2<0.4 2559 < ν < 3412 GeV <xbj>=2.59x10-4 <xg>=3.42x10-2 Charged particles • Nuclear effect: • nPDF EPS09 • Cold nuclear medium energy loss DNP 2013, Liang Zheng

  11. 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. DNP 2013, Liang Zheng

  12. 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 DNP 2013, Liang Zheng

  13. Back up

  14. Structure functions Sensitive to gluons eAu: 5x50 2 fb-1 5x75 4 fb-1 5x100 4 fb-1 Running combined 6 months total (50% eff) Systematics-error dominated DNP 2013, Liang Zheng

  15. Diffraction Exclusive Vector meson production Coherent: nuclei intact Incoherent: break up Finding the source DNP 2013, Liang Zheng

  16. Dihadron correlation at an EIC 10x100 GeV Lc = z0.35(1-z) ν y = 0.3, z = 0.3, ν= 640 GeV, Lc = 420 fm y = 0.7, z = 0.3, ν = 1492 GeV, Lc = 979fm charged pion z>0.1, ν>6 GeV, xFeynman>0, pT>0.1 GeV Where we are eic-tf-meeting

  17. Kinematics coverage in the Dihadron correlation at an EIC 10x100 20x100 Black box:0.6<y<0.8 Red box:0.25<y<0.35 Qs2 for Au Qs2 for Ca Qs2 for proton eic-tf-meeting

  18. Dihadron correlation in different kinematics bins (no sat) 10x100 GeV 1fb-1 eic-tf-meeting

  19. Dihadron correlation in different kinematics bins (sat) 10x100 GeV 1fb-1 eic-tf-meeting

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