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High-mass Dilepton Physics at RHIC-II

High-mass Dilepton Physics at RHIC-II. Jen-Chieh Peng. University of Illinois. Quark and Gluon Distributions in Nuclei Flavor Structure of Nucleon Quark Distributions Forward Tagging and Measurement of Meson Cloud. RHIC-II Workshop, April 29, 2005.

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High-mass Dilepton Physics at RHIC-II

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  1. High-mass Dilepton Physics at RHIC-II Jen-Chieh Peng University of Illinois • Quark and Gluon Distributions in Nuclei • Flavor Structure of Nucleon Quark Distributions • Forward Tagging and Measurement of Meson Cloud RHIC-II Workshop, April 29, 2005

  2. What are the quark and gluon contents of nuclei? (How do they differ from a free nucleon?) Spin and flavor decomposition of parton distributions in nuclei?

  3. PRL 83 (1999) 2304 The Drell-Yan p-A measurement can be extended to lower x at RHIC

  4. Expected kinematic coverage and sensitivites for a two-month run at designed luminosity at PHENIX EKS98 Shadowing at low x?

  5. Disappearance of shadowing at small x? Predicted nuclear dependence of Drell-Yan at small x for dilepton mass of 4.5 GeV Kopeliovich et al. (hep-ph/0501260)

  6. Prediction of nuclear modification in the Color Glass Condensate formalism Dilepton production in pA and dA at RHIC energy Jalilian-Marian (nucl-th/0402014) Rd(p)A shows strong mass dependence at y=2.2

  7. Gluon distributions in nuclei deduced from Q2 – dependences of F2Sn/F2C NMC data

  8. photon - jet direct photon dijet/dihadron open charm high-pTl+l- At RHIC, many hard-processes in p-A (d-A) collisions are sensitive to gluon distributions in nuclei (identical to the tools used to determine ΔG(x) in RHIC-Spin) Gluon distributions in nuclei could be probed down to x ~ 10-2 It would be very interesting to reach x ~ 10-3 to search for gluon saturation effect at low x

  9. J/Ψ production is dominated by gluon-gluon fusion (x ~ 10-3 could be reached)

  10. Flavor asymmetry of the nucleon sea Comparison of p+d with p+p Drell-Yan

  11. Flavor asymmetry of the nucleon sea can be measured at small x at RHIC

  12. Meson-cloud around the nucleon: Sullivan Process

  13. Can one probe the meson cloud directly? Electron DIS scattering off pomeron or meson was studied at HERA by tagging forward-going proton/neutron Pion structure functions at 10-4 < x < 10-2 were measured Can one study analogous processes at RHIC?

  14. Tagged Drell-Yan production at RHIC? One can tag on forward-going proton, neutron, Δ, Λ in coincidence with lepton-pair

  15. Can one detect Drell-Yan events tagged by forward-going nucleons at RHIC?

  16. Angular distribution of tagged neutrons Zero-Degree Calorimeter for neutron detection

  17. Tag the forward p (d) using Roman Pots

  18. Other possible tagged Drell-Yan measurements

  19. Hard diffractive J/Ψ and di-jet production in Tevatron J/Ψ production with a rapidity gap PRL 87 (2001) 241802 Comparison of the J/Ψ and dijet data shows the gluon fraction of proton’s diffractive structure function is 0.59 ± 0.15

  20. Hard diffractive production of W and Z bosons at the Tevatron Sensitive to quark contents of the diffractive structure functions hep-ex/0308032 The unique features of RHIC for hard diffractive physics are the availability of polarized protons and p-A

  21. Summary • The quark and gluon structures of protons, nuclei and mesons could be studied at RHIC-II. • Dilepton production can probe many interesting features of the partonic structure of hadrons. • Capability of forward-tagging with a Roman Pot in conjuction with di-lepton detection could significantly enhance the physics reach of p-p and p-A programs at RHIC.

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