1. Forward Spectrometer Upgrade LOI pp, pA and AA physics Richard Seto BNL – EC/DC upgrades meeting May 5, 2005

2. General considerations We are now assessing [s?QGP or NOT?] Suppose we got it? Do we understand it? What is it? How is it made? Unexpected importance of: Particle ID is surprisingly important even at high pt Forward (backward) rapidities different than central system is not Bjorken Question : Why not a 4  detector? Old answer- HI physics is NOT like particle physics – Its more like using a thermometer to measure the temperature (sample the momentum distribution) in a beaker of water New fact – its like like having several beakers with different conditions

3. PHENIX  =0.7 [  = .35] electrons (momentum) Vector mesons charged particles PID hadrons photons High rate triggers jets (to be added) detached vertex (to be added)  =3 [  =  (1-2.5)] muons(momentum) vector mesons charged particles (to be added) ? detached vertex (to be added) NCC  0 NCC (+electrons) Muon Trigger NCC

4. 0.11 Energy Density (GeV/fm 3 ) 10 Time (fm) 10 100 I. dAu What is the Initial State of a Relativistic Heavy Ion Collision? A CGC? Property of initial state

5. x Q (GeV) 1 10 -1 10 -3 10 -2 10 -4 CGC Purely classical – tree level only CQF Quantum evolution via anomalous dimension 1 10 100 Qs  QCD Y~0 Y~4 Y~2 R dA Rises w/ N part Cronin Shadowing: Higher twist R dA ~1 (pQCD) Rises w/ N bin (N bin ) No Cronin R dA <1 Falls with N part No Cronin Shadowing: Leading twist Regions of a nucleus pQCD CGC boundary Q S 2 =Q S (y=0) 2 e y ~0.3 CQF boundary Q S 2 =Q S (y=0) 4

6. high pt suppression ! Where does the high pt suppression come form? Initial State (property of cold nucleus) Final state (QGP)  dA same effect at  >2  =0 R AA R dA conclusion: final state - QGP conclusion: initial state –cold nucleus Physics is different in the at  >2 ! (new physics to explore) R CP M. Liu QM04 PHENIX prelim

7. x Q (GeV) 1 10 -1 10 -3 10 -2 10 -4 CGCCGC CQFCQF 1 10 100  QCD Y~0 Y~4 Y~2 Regions of a nucleus pQCD CGC boundary Q S 2 =Q S (y=0) 2 e y ~0.3 CQF boundary Q S 2 =Q S (y=0) 4 PHENIX BRAHMS HARD PROBES BULK

8. e,  ** ? How do you experimentally see saturation? Look at Gluon Structure Functions at low-x Ask Dima, Al, Jamal etc to calculate pA (in order of preference?)  * , ee Direct photons Open Charm J/  production Evolution of quark structure functions with Q 2 – use Drell- Yan as a probe ? X ~ 1 to 10 -4 (evolution) Q 2 ~ 1 (saturation) to 50 (pQCD) Functions of Y= 0 to 4, p T =0 to 10 GeV Centrality Map out previous diagram

9. Measuring (gluon) structure functions in the era of NLO and NNLO LO (leading order) Factorization PDF(x,Q 2 )  pQCD_LO (x, Q 2 ) Theorists turn out stuff in x, Q 2 LO diagram – easy connection between x, Q 2 and experimental variables (p T, …) NLO (next to leading order) Factorization still OK, but use NLO pQCD Connection to x, Q 2 messed up Solution: theorists turn out stuff in terms of experimental variables

10. Steps (CTEQ) Choose experimental data sets (get the ones that give the best constraints) Select factorization scheme, consistent choice of factorization scale etc Choose the parametric form of the parton distributions and then evolve distributions to any other value of  Find experimentally measured quantities Calculate  2 ; iterate.

11. BUT Don’t we loose information in doing this? Solution– get new observables Werner – intrinsic K T Note for some things – heavy quark production –e.g. CGC does not need to put in “K T ”, but it comes out of the calculation (same with NLO) Experiments need to characterize events as completely as possible e.g. k T i.e. one needs in direct photons, a measure of the jet energy and direction note: even for direct photons in the central spectrometer – a measurement of the jet is necessary for the complete characterization of the event, Indeed a jet in the forward region will favor lower x 2 for photons in the central arm

12. Other Stuff Nuclear Structure (quark level) hadron production in nuclei Multiparton correlations in nucleons (3D-picture) Measurement of three quark component of the nucleon wave function. Color fluctuations in nucleons: global effects & x- dependent effects

13. II AA collisions – Quarkonia  C (Sean Kelly) Onium system as thermometer pT Dependence xF Dependence Study vs system size and energy Bound

14. precursorcolor singlet quarkonia pre-resonance absorbtion pre-equilibrum effects color screening, thermal production break up by co-moving hadrons c J/J/ quarkonia local time medium local time Quarkonia local time gets dilated as a function of p t. This make the ratios of directly produced quarkonia a probe of the plasma lifetime Time Zones tau=.1 fm

15. If we see suppression… Is it just the cold nucleus? dA

16.  acc and resolution  GeV Important to keep resolution of muon spectrometer!

17. Other Stuff to consider in AA triggering on upsilon for RHIC 2 Photon- high pt particle correlations with central spectrometer RAA Flow e-  for heavy flavor physics vector mesons – to ee p+K ~charged –  0 ….

18. 2 track resolution ?

19. Coverage 100x100 Q2Q2Q2Q2 Log(x 2 ) direct photon 0.5 pb -1 pAu (run 12)  log(x 2 )  Q 2 =0.1x1 GeV 2 1000event/bin 500 100 20

20. Requirements  ~1-3 Muons high rate/ triggerable keep good momentum resolution Calorimeter large acceptance (i.e. can measure jets) can handle high occupancy reasonable emc energy resolution 2 track resolution ~ 2-4 mm reasonable position resolution ability to live close to the beampipe (i.e. can kill backgrounds – timing? triggerable