Forward Physics at RHIC and LHC report from the Lawrence Workshop

1. Forward Physicsat RHIC and LHCreport from the Lawrence Workshop F.Videbæk BNL RHIC-II workshop, BNL

2. Program of meetinghttp://agenda.cern.ch/fullAgenda.php?ida=a044385 Color Glass Condensate A.Mueller – Review of HERA data R.Debbe -BRAHMS forward program B.Wysloch -The forward detectors of CMS L.McLerran -Color Glass Condensate. Physical Picture and simple questions P.Armesto -geometric Scaling K.Tuchin – Forward Physics at RHIC. Onset of Saturation R.Hwa – Forward Production by Parton Recombination D.Kahana - - Initial thoughts for D+A Heavy Ion systematic I.Bearden – BRAHMS Au-Au results R.Hollis – limiting fragmentation G.Stephans – fixed target at RHIC SPIN F.Videbaek – BRAHMS spin J.Qiu – RHIC spin J.Ralston – disentangling forward physics RHIC-II workshop, BNL

3. McLerran: Phase Space of Interesting Physics Small x: Potentially large region in Q Matter has universal properties at small x: Only variable is the saturation momentum! Is this true? RHIC-II workshop, BNL

4. Crucial Observations: Limiting Fragmentation Geometric Scaling in ep Renormalization Group Are these connected by universal QCD properties at large y. RHIC-II workshop, BNL

5. Developing Theoretical Story: Fluctuations are important: Evolution equations from low density to high density are fluctuation dominated. Event by event studies with wide coverage in x and/or pT? What are predictions for fluctuation spectra in observables? RHIC-II workshop, BNL

6. RHIC-II workshop, BNL

7. RHIC-II workshop, BNL

8. The “benefits” of p+A systems Deep Inelastic Scattering eA has no direct access (first order) to the gluon PDF it measures q - qbar To access gluon PDF the preferred system would be p+A thru “gluon-initiated” g+q or g +g interactions. R.Debbe RHIC-II workshop, BNL

9. At 4 degrees (y~3 for pions) and pT = 1 GeV/c one can reach to values as low of x2 ~ 10-4 But one has to remember that that low number is a lower limit, not a typical value. From Gusev, Strickman, and Vogelsang. Most of the data collected at 4 degrees would have x2~0.01 RHIC-II workshop, BNL

10. K.TuchinForward Physics at RHIC onset of saturation RHIC-II workshop, BNL

11. Scaling of charm spectra with atomic number A(Kharzeev) RHIC-II workshop, BNL

12. RHIC-II workshop, BNL

13. RHIC-II workshop, BNL

14. Forward Production by Parton Recombination • Rudolph C. Hwa -- conclusion • No change of physics from h<0 to h>0. • No multiple scattering or gluon saturation put in explicitly. • Behaviors to check • β, η dependences pT spectra (a) pions • (b) protons If p/p > 0.2, difficult for • fragmentation • RCP well reproduced with only the recombination of • soft and shower partons. • Back-to-back jets • Di-hadron correlations • No conflict between CGC and recombination, only question is where? RHIC-II workshop, BNL

15. Rapidity Dependent High-pT Measurement y~0 BRAHMS forward rapidity at fixed time Nuclear Modification Factor high-y • Different rapidities provide different densities of the medium: Sensitive to the dynamics • Largest medium effect at mid-rapidity? • Rapidity dependent high-pTsuppression factors: provide information on dynamical medium effect RHIC-II workshop, BNL Nucl-th/0108056, Polleri and Yuan

16. Rcp for h+ and h- at h~3.2 BRAHMS Preliminary Rcp at h~3.2 for charged hadrons • Strong centrality dependence: Rcp(0-10%) < Rcp(20-40%) • No significant h dependence in 0<h<3.2 • Maximum at pT~2GeV/c (rapidity independent soft-hard transition?) • Systematic Errors - 10-15% overall - 10% p-by-p Is this understood? h~3.2 h~0 h~2.2 BRAHMS PRL 91 (2003) RHIC-II workshop, BNL

17. 3D-Hydro+Jet PRC 68 (2003) 064902 Hirano and Nara 3D Hydrodynamic Simulation with Jet (pQCD/PYTHIA) • Qualitatively describe data with pseudo-rapidity dependence RHIC-II workshop, BNL

18. Strangeness with Kaons RAPIDITY DEPENDENCE Divergence at higher y : Associated K+ production No single source with unique T and B High rapidity equivalent in certain ways to lower energy data at mid-rapidity? Can be used to explore baryon high-density matter ? RHIC-II workshop, BNL

19. Limiting Fragmentation Observations at PHOBOSRichard S Hollis, UIC UA5 (200-900) → Z.Phys.C 43 (1989) 1 ISR (23.6,45.2) → Nucl.Phys B129 365 (1977) p+p, d-A d+Au data from nucl-ex/0409021 p+Em referenced therein RHIC-II workshop, BNL

20. Questions raised Several questions remainCentrality dependence for whole rangeCollision species dependenceWill Cu+Cu fit into Au+Au data systematics?Is this observation specific to η?Original hypothesis was for rapidity distributionsDoes each particle species exhibit the same features?Limiting fragmentation also seen for v2. Should these measurements be done for identified hadrons? RHIC-II workshop, BNL

21. RHIC spin – Jianwei Qiu, Iowa S.U. RHIC-II workshop, BNL

22. <e>~ -0.035 => AN= -0.08 +- 0.005 +- [0.015] in 0.17 < xF < 0.32 The SSA needs xf-pt coverage to disentangle phenomena (Collins, Sievers…) Jet-correlations studies important. RHIC-II workshop, BNL

23. Multiplicity and hermetic coverage to |η|<7 • Zero Degree Energy • Physics: • Centrality • Limiting Fragmentation • Peripheral and ultra-peripheral collisions • Low-x, Color-Glass Condensate • DCC, Centauros, Strangelets Forward Region: B.Wyslouch RHIC-II workshop, BNL

24. Emerging Themes • (Armesto)To clarify the role of saturation (scaling): more data needed, e.g. • pp, pA and AA at 0 < y < 5 (Y -scan of Qs2). • pA with several A at b = 0 (A-scan of Qs2 ). • AA at different b (centrality evolution of multiplicities). • Correlations in pA for the same and different rapidities. • (Mueller)Need to understand the early times. • measurements from initial system ( jets, photons, di-leptons) RHIC-II workshop, BNL

25. (Tuchin) At RHIC we are starting to see a novel effects due to a quasi-classical regime of QCD - the Color Glass Condensate, first signatures of which where observed at HERA. • Future tests of CGC at RHIC y À 1: • inclusive hadrons (V) • open charm ? • hidden charm ? • di-leptons ? • correlations and Fluctuations ? (McLerran)Fluctuations are important: Evolution equations from low density to high density are fluctuation dominated. Event by event studies with wide coverage in x and/or pT? What are predictions for fluctuation spectra in observables? RHIC-II workshop, BNL

26. (J.Qiu) RHIC spin • (discussion) • -Can the connection between saturation and limiting fragmentation be clarified by additional high-y measurements for identified particles. • Should the options to investigate systems with large baryon density vs. rapidity or fixed target at lower energy be explored? • How firm is the evidence for CGC at RHIC? RHIC-II workshop, BNL

27. The pitch for Forward Physics • Many of the issues brought up at the workshop are central to an enhanced forward physics program. • The RHIC program is on its way to implement this for upgrades, and possible future detector. • There are good reasons this should be a motivation and an integral part for the RHIC-II program. • Many of the points here have also been addressed in the Letter of Intent of a new detector for RHIC http://www.bnl.gov/henp/pac0904.asp • Low-x physics will be important too at LHC. The opportunities for systematic measurements at RHIC with pA, AA makes it competitive. RHIC-II workshop, BNL