The Physics of eRHIC Introduction Scientific highlights Detectors Summary R. Milner

1. The Physics of eRHIC • Introduction • Scientific highlights • Detectors • Summary R. Milner 8th Conference on Intersections of Particle and Nuclear Physics New York May 23rd, 2003

2. The Electron-Ion Collider (EIC) • Substantial international interest in high luminosity (~1033cm-2s-1) polarized electron-ion collider over last several years • Workshops Seeheim, Germany 1997 IUCF, USA 1999 BNL, USA 1999 Yale, USA 2000 MIT, USA 2000 • Electron Ion collider (EIC) received very favorable review of science case in US Nuclear Physics Long Range Plan, with strong endorsement for R&D • At BNL Workshop in March 2002, EIC Collaboration has formulated a plan to produce a conceptual design within three years using RHIC : eRHIC • NSAC in March 2003, declared eRHIC science `absolutely central’ to Nuclear Physics

3. The Electron Ion Colliderhttp://www.bnl.gov/eic • Slide-report of the Joint DESY/GSI/NuPecc Workshop on Electron-Nucleon/Nucleus Collisions, March 3-4, 1997, Lufthansa-Zentrum Seeheim, Germany, GSI Report 97-04. • Proceedings of the Workshop on Physics with a High Luminosity Polarized Electron Ion Collider (EPIC99), April 8-11, 1999, Bloomington, Indiana, USA, Editors L.C. Bland, J.T. Londergan, and A.P. Szczepaniak, World Scientific. • Proceedings of the eRHIC Workshop, December 3-4, 1999, Brookhaven National Laboratory. • Proceedings of the Second eRHIC Workshop, April 6-8, 2000, Yale University, New Haven, Connecticut, USA, BNL Report 52592. • Proceedings of the Second Workshop on Physics with an Electron Polarized Light Ion Collider (EPIC 2000), September 14-16, 2000, MIT, Cambridge, MA, USA, Editor R.G. Milner, AIP Conference Proceedings No. 588. • Proceedings of the Electron Ion Collider Workshops, February 26-March 2, 2002, Brookhaven National Laboratory, Editors M.S. Davis, A. Deshpande, S. Ozaki, R. Venugopalan BNL-52663-V.1 and V.2.

4. eRHIC is a powerful new tool required for the study of the fundamental structure of matter • 99.9% of observable matter in the physical universe is in the form of atomic nuclei • To a good approximation, nuclei are systems of bound nucleons • QCD tells us that the nucleon is made of pointlike constituents bound by powerful gluon fields x is the momentum of the quark or gluon where  is the spatial distance scale probed • A new facility which directly probes the quarks and gluons is demanded Lepton probe High center of mass energy High luminosity  precision Polarized lepton, nucleon Optimized detectors

5. Why a Collider ? • High Ecm  large range of x, Q2 x range: valence, sea quarks, glue Q2 range: utilize evolution equations of QCD • High polarization of lepton, nucleon achievable • Complete range of nuclear targets • Collider geometry allows complete reconstruction of final state

6. Q2 and x Range of eRHIC

8. Scientific Highlights • nucleon structure sea quarks and gluespin and flavor structure new parton distributions • Meson structure , K are Goldstone Bosons of QCD essential to nuclear binding • hadronization evolution of parton into hadron process in nuclei of fundamental interest • nuclei role of partons initial conditions for relativistic heavy ion collisions • matter under extreme conditionssaturation of parton distributions new phenomena, e.g. colored glass condensate

9. Spin structure function g1 of proton low x x = 10-3 0.7 Q2 = 0  103 GeV Fixed target experiments 1989 – 1999 Data x = 10-4 0.7 Q2 = 0  104 GeV eRHIC 250 x 10 GeV Lumi=85 inv. pb/day 10 days of eRHIC run Assume: 70% Machine Eff. 70% Detector Eff.

10. Structure of the Goldstone Bosons Light mesons: pions and kaons • important role in nuclear physics • important component of nucleon structure • approximate chiral symmetry • Goldstone bosons of chiral models • nuclear medium effects - In collider kinematics the pion can be probed essentially on shell. - with light nuclear projectiles, pions and kaons in medium can be studied. • Partonic origin of nuclear binding

11. Pion Structure Function with eRHIC Expected Errors for 1 day of eRHIC running Quark momentum distribution of pion

12. Using Nuclei to Increase the Gluon Density • Parton density at low x rises as • Unitarity  saturation at some • In a nucleus, there is a large enhancement of the parton densities / unit area compared to a nucleon Example Q2=4 (GeV/c)2 < 0.3 A = 200 Xep=10-7 for XeA = 10-4

13. Gluon Momentum Distribution from DIS

14. RHIC Data consistent with Gluon Saturation

15. eRHIC Detectors • central detector 30° <  < 160 ° tracking calorimetry particle i.d. jet reconstruction luminosity measurement e.g. ZEUS detector at HERA • suite of dedicated detectors at small angles • Forward, rear detectors to increase acceptance • Complete event detector in eA (M.W. Krasny) • Low t measurements e.g. DVCS, Sullivan process • Detailed simulations underway

17. The Hadron Side of the Krasny Detector

18. Summary • eRHIC covers a CM energy range from 30 to 100 GeV and is essential to a systematic study of QCD phenomena • eRHIC will address key questions - spin and flavor structure of nucleon - new parton distributions - structure of Goldstone bosons - role of partons in nuclei - search for new phenomena • Conceptual design of eRHIC machine and scientific equipment under development

19. Authors of Electron Ion Collider White Paper Argonne National Laboratory R. Holt, P. Reimer Brookhaven National Laboratory I. Ben Zvi, J. Kewischm, T. Ludlam, L. McLerran, J. Murphy, S. Peggs, P. Paul, T. Roser, B Surrow, R. Venugopalan Budker Institute of Nuclear Physics, Russia I.A. Koop, M.S. Korostelev, I.N. Nesterenko, A.V. Otboev, V.V. Parkhomchuk, E.A. Perevedentsev, V.B. Reva, V.G. Shamovsky, D.N. Shatilov, P. Yu. Shatunov, Yu. M. Shantunov, A.N. Skrinsky CERN, Switzerland A. De Roeck University of Colorado at Boulder E.R. Kinney, U. Stoesslein Fermi National Laboratory V.A. Lebedev, S. Nagaitsev University of Illinois at Urbana-Campaign N. Makins Indiana University Cyclotron Facility and Indiana Univserity J. Cameron, T. Londergan, P. Schwandt Thomas Jefferson Laboratory Y. Derbenev, G.A. Drafft, R. Ent, L. Merminga, C. Sinclair Lawrence Berkley National Laboratory X. Wang Los Alamos National Laboratory G. Garvey Massachusetts Institute of Technology A. Bruell, W. Graves, D. Hasell, K. Jacobs, R. Milner, K. Takase, C. Tschalaer, F. Wang, A. Zolfaghari Institute of Nuclear Physics, Poland J. Chwastowski University of Paris VI, France E. Barrelet, M.W. Krasny Pennsylvania State University M. Strikman University of Regensburg, Germany A. Freund, A. Schaefer, M. Stratmann RIKEN-BNL Research Center A. Deshpande, M. G. Perdekamp, N. Saito Saclay, France G. Radel TRIUMF, Canada A. Miller Yale University V.W. Hughes Core Group: • Accelerator & IR Design V. Ptitsyn (BNL) + team BNL/Bates • Physics Coordination A. Deshpande(RBRC)  Theory principle contacts: W. Vogelsang (BNL)& R. Venugopalan (BNL)  Monte Carlo Generators N. Makins (UIUC) + team  Detector Simulation Tool B. Surrow (BNL)  DAQ and Trigger Issues (BNL+Colorado+Others)  Detector Technology (BNL+LBNL+MIT+Kyoto+RBRC+Others) • eRHIC Accelerator & IR Design Group • J.Kewisch, B.Parker, S.Peggs, V.Ptitsyn, D.Trbojevic (BNL) • D.E.Berkaev, I.A.Koop, A.V.Otboev, Yu.M.Shatunov (BINP) • C.Tschalaer, J.B. van der Laan, F.Wang (MIT-Bates) • D.P.Barber (DESY)