The eRHIC project at Brookhaven National Laboratory

1. Up to 10 GeV injector 5-10 GeV static e-ring RHIC e-cooling EBIS BOOSTER AGS LINAC The eRHIC project atBrookhaven National Laboratory Bernd Surrow

2. Up to 10 GeV injector 5-10 GeV static e-ring RHIC e-cooling EBIS BOOSTER AGS LINAC Outline • The RHIC physics program and recent results • Physics case - eRHIC • Machine and detector design studies - eRHIC • Introduction • Outlook - eRHIC Bernd Surrow

3. p+p (trans. polarized) p+p (long. polarized) Introduction • The RHIC collider facility at BNL (1) Au+Au (d+Au) Experiments: • PHENIX • STAR • BRAHMS • PHOBOS Experiments: • PHENIX • STAR • BRAHMS & PP2PP • RHIC facility: Unique collider facility which allows to collide different species (Au-Au and d-Au as well as polarized p-p) at variable beam energy • Explore the nature of matter under extreme conditions (RHIC relativistic-heavy ion program) • Explore the nature of the proton spin (RHIC spin physics program) Bernd Surrow

4. Absolute Polarimeter (H jet) RHIC pC polarimeter BRAHMS & PP2PP BRAHMS & PP2PP Lmax = 2 x 1032 cm-2s-1 PHOBOS Beam Energy = 100 GeV/u Lave per IR = 2  1026 cm-2 sec-1 Siberian snakes 70% Beam Polarization 50 < √s < 500 GeV PHENIX PHENIX STAR STAR Spin rotator Siberian snakes 9 GeV/u Q = +79 Partial Siberian Snake Pol. Proton Source 500 mA, 300 ms Spin rotator BOOSTER LINAC BOOSTER AGS Internal Polarimeter AGS AGS 200 MeV Polarimeter AGS pC polarimeter TANDEMS Rf Dipoles 1 MeV/u Q = +32 Introduction • The RHIC collider facility at BNL (2) • RHIC spin physics program • RHIC relativistivic-heavy ion program PHOBOS • RHIC: Two concentric superconducting magnet rings, 3.8km circumference • Start of construction: January 1991 • First collisions of Au-Au ions: June 2000 • First collision of trans. polarized protons: December 2001 • First collisions of long. polarized protons: May 2003 Achieved configuration: • Au+Au: √s = 130 and 200 GeV • d+Au: √s = 200 GeV • p+p: √s = 200 GeV Bernd Surrow

5. Exploring a new state of matter: “The Quark-Gluon Plasma” The RHIC physics program and recent results • QCD predicts the existence of a color-deconfined medium with quarks and gluons as the relevant degrees of freedom • Create this new state of matter (QGP) in relativistic heavy-ion collisions: P. Braun-Munzinger, nucl-ex/0007021 • Exploring several different signatures is crucial to establish a phase transition from a hadron gas to the quark-gluon plasma • Those signatures point to different aspects of the phase transition to be explored, e.g. partonic energy loss! • Partonic energy loss provides a sensitive probe of matter created in relativistic heavy-ion collisions: • Attenuation of leading particles from jet fragmentation (“Jet quenching”) Bernd Surrow

6. STAR The RHIC physics program and recent results • RHIC results in Au+Au and d+Au collisions d+Au Au+Au Suppression of inclusive yield in Au-Au collisions is a final-state effect! d+Au Au+Au Bernd Surrow

7. Proton Spin Gluon Spin The RHIC physics program and recent results • RHIC Spin program (e.g. ΔG) • At present: G is only poorly constrained from scaling violations in fixed target DIS experiments • Fundamental question: How is the proton spin made up? SMC, Phys. Rev. D58 (1998) 112002. • Need: New generation of experiments to explore the spin structure of the proton: polarized proton collisions at RHIC which allows to access directly G in polarized pp collisions! Orbital Motion Quark Spin  SMC result: Fraction of proton spin carried by quarks is small: RHIC spin program:  Where is the spin of the proton then? • Unique multi-year program which has just started…! • Explore various aspects of the spin structure of the proton in a new domain:  SMC QCD-fit: • Spin structure of the proton (gluon polarization, flavor decomposition, transversity) • Spin dependence of fundamental interactions • Spin dependence of fragmentation • Spin dependence in elastic polarized pp collisions Bernd Surrow

8. The RHIC physics program and recent results • RHIC results in transverse polarized pp collisions • Several approaches beyond the basic “naive QCD calculations” yield non-zero AN values at RHIC energies: • Sivers: include intrinsic transverse component, k, in initial state (before scattering takes place) • Collins: include intrinsic transverse component, k, in final state (after scattering took place) • Qiu and Sterman: more “complicated QCD calculations” (higher-twist, multi-parton correlations) • AN is found to increase with energy similar to E704 result • This behavior is also seen by several models which predict non-zero AN values Bernd Surrow

9. eRHIC Physics case - eRHIC • General comments on eRHIC • Goal of eRHIC project at BNL: Establish a high energy, high intensitypolarized electron/positron beam facility at BNL to collide with the existingRHIC heavy ion and polarized proton beam • Explore new QCD regime in eA scattering and polarized ep scattering in collider mode beyond the fixed target DIS era • Complement current physics program at RHIC (AA/pp  eA/ep) Bernd Surrow

10. Physics case - eRHIC • Current world status of F2 (unpolarized DIS) and g1 (polarized DIS) data • F2 results: • g1 results: • Good description of F2/g1 data by NLO DGLAP fits • HERA collider data extended kinematic region towards larger Q2 and low x for F2 • g1 limited by fixed target data at low Q2 and high x 4 orders of magnitude in x! 4 orders of magnitude in Q2! Limited range in x and Q2! Bernd Surrow

11. Physics case - eRHIC • eRHIC physics program eRHIC 250 x 10 GeV Luminosity: ~85 inv. pb/day • Unpolarized ep scattering: • Longitudinal structure function FL • Flavor separation • Precise direct measurement of the gluon (0.001 < x < 0.5-1) • Exclusive reactions • Transition region (Q2 0) • Polarized ep scattering: • Polarized structure function of the proton • Gluon polarization (Complementary efforts at RHIC, COMPASS and HERMES) • Exclusive reactions • Deeply-virtual Compton scattering (Orbital angular momentum of quarks) 10 days of eRHIC run Assume: 70% Machine eff. 70% Detector eff. Fixed target experiments 1989 – 1999 Data Bernd Surrow

12. Physics case - eRHIC • eRHIC physics program • Measurements on the gluon polarization at eRHIC: • Extract gluon polarization in various modes in DIS and photoproduction • Good precision • x-range: 0.01 < x < 0.3 eRHIC Di-Jet DATA 2fb-1 Bernd Surrow

13. Physics case - eRHIC • Physics program • eA scattering: • Study eA scattering for the first time in collider mode • Influence of nuclear medium within nucleus/nucleon: F2A/F2N • Gluon distribution within nucleus • Parton saturation at low-x:  Large enhancement of the parton densities / unit area compared to a nucleon, thus access effectively lower values in x then comparable ep mode! Bernd Surrow

14. IP12 up to 10 GeV injector IP2 IP10 5-10 GeV static e-ring IP8 IP4 IP6 RHIC e-cooling EBIS BOOSTER AGS LINAC Machine and detector studies - eRHIC • General comments on eRHIC • Essential features eRHIC: • High luminosity: ≈ 1 · 1033 cm-2 sec-1 (ep) / ≈ 1 · 1031 cm-2 sec-1 (eA) • High polarization (polarized e, p and light ion beams): ≈ 70% • Heavy ion beams of several elements • High (variable) energy: Ee ≈ 5 - 10 GeV, Ep ≈ 50 - 250GeV • Variable center-of-mass energy (ep): 30 – 100 GeV • Kinematic reach: x ≈ 10-4 - 0.7 (Q2 > 1 GeV2) • Optimal detector for physics to be explored at eRHIC (Lessons from HERA!) • Current electron ring design: • Proposed by BINP & MIT-Bates + BNL with input from DESY (IR design under active discussion) • e-ring is approximately ¼ of RHIC ring • So far: Collisions in one interaction region (Multiple detectors are under consideration) • Full energy injection using polarized electron source and 10 GeV energy linac • Longitudinal polarization using local spin rotators • Possible collisions points: IP12, IP2 and IP4 Bernd Surrow

15. eRHIC machine parameters Machine and detector studies - eRHIC • Beam parameter limits assumed for a realistic design • eRHIC parameters for different configurations Bernd Surrow

16. Machine and detector studies - eRHIC • eRHIC in comparison to other facilities • eRHIC features: • Variable beam energy • p and ion beams • Proton and light ion polarization • Large luminosity • Huge kinematic reach ELIC-Jlab TESLA-N eRHIC Bernd Surrow

17. Ee = 10GeV EP = 250GeV y = 1  = 3° eRHIC x-Q2 acceptance! Machine and detector studies - eRHIC • Requirements on a future eRHIC detector • Basic requirements: • Measure precisely scattered electron (Kinematics of DIS reaction) • Tag electrons under small angles (Study of transition region) • Measure hadronic final state (Kinematics, jet studies, flavor tagging, fragmentation studies, particle ID) • Zero-degree photon detector to control radiative corrections and in e-A physics to tag nuclear de-excitations • Missing ET for events with neutrinos in the final state (W decays) • Tagging of forward particles (Diffraction and nuclear fragments) Bernd Surrow

18. r z Machine and detector studies - eRHIC • eRHIC detector design studies  Very preliminary acceptance limitation studies by inner machine magnets:Better acceptance at low scattering angles down to Q2 ~ 0.5 GeV2 with changing radius r as a function of z for coil arrangements of inner magnets (B. Parker, BNL)! • GEANT simulation started of a central detector geometry • Study of synchrotron radiation background is underway (Contacts to DESY colleagues) • Crucial: Forward and rear tagging devices and acceptance limitation of inner machine elements Ep=250 GeV Ee=10 GeV Bernd Surrow

19. Outlook - eRHIC • Past: • Series of workshops • Before 2001: • Indiana/MIT: EPIC • eRHIC • Merge to EIC: EIC = eRHIC + EPIC (Sept. 2000) • White paper (March 2001) • EIC workshop (Febr. 2002) • “Absolutely Central to the field…” NSAC 2001-2 Long Range Planning document summary; high on R&D recommendation projects. • Highest possible scientific recommendation from NSAC Subcommittee February/March 2003, Readiness Index 2 ( JLAB-ELIC 3) • Present: • Potential next large-scale project at BNL beyond RHIC • Beam cooling for RHIC already within eRHIC machine budget • Strong intention to have a dedicated eRHIC group at BNL soon • WWW-page: http://www.bnl.gov/EIC • eRHIC: Zero-th Design Report (Physics + Accelerator Lattice)  Requested by BNL Management by January 2004 Bernd Surrow

20. Up to 10 GeV injector 5-10 GeV static e-ring RHIC e-cooling EBIS BOOSTER AGS LINAC Outlook - eRHIC • Future: • Series of CDR’s: • Rough institutional responsibility, interests and functionality of detector by 2005/2006 (CD0) • Detector R&D money could start for hardware by approx. 2007 (CD1) • Ring, IR, Detector design document by approx. 2008 (CD2) • Final Design ready by approx. 2010 (CD3)  Begin construction • First collisions in approx. 10 years from now...! Bernd Surrow