Physics with the PHENIX Muon Trigger Upgrade

1. Physics with the PHENIX Muon Trigger Upgrade Brett Fadem, Muhlenberg College for the PHENIX Collaboration DNP Meeting, October12, 2007

2. Overview of Talk • Overview • The proton spin puzzle. • Current knowledge of sea quark polarizations. • Probing proton spin structure with W’s. • Backgrounds • Trigger rejection of hadron decays • High PT ghosts • Conclusion

3. gluon spin orbital angular mom. quark spin The Proton Spin Puzzle Spin of proton: W physics and the muon trigger upgrade

4. Current Knowledge of Quark Polarizations • Challenges: • Large errors • Uncertainties due to low Q2 • “Hadron tagging” relies on fragmentation functions Results of HERMES spin-flavor decomposition using a leading order analysis of inclusive and semi-inclusive deep-inelastic electron scattering. PRD 71:012003,2005

5. Tagging quarks with W±

6. The RHIC Spin Program Transverse single/double spin physics Flavor Decomposition Gluon Polarization Transversity: Sivers vs. Collins effects & physics of higher twists; Pion interf. Fragmentation p0,+,- Production W physics Longitudinal single spin physics Heavy Flavors Transverse single spin physics Phenix-Local Polarimetry Prompt Photon

7. For illustration: Leading order single spin asymmetries in W production • Unpolarized W production: • Polarized part: • Measure moun count rates: • Count rate difference:

8. In this LO scheme • Parity violating decay selects the quark flavor • Forward/backward region selects valence/sea quark helicity contribution

9. Advantages of W Probes • No fragmentation functions are used in the analysis • Good statistics • Q2 is set by the W mass. • Rigorous theory framework based on NLO pQCD and soft gluon resummation. • Projected luminosity: • ∫Ldt=950pb-1, P=0.7 at √s=500 GeV Projected PHENIX errors

10. Physics Backgrounds • PT cut removes heavy flavor background • Z background contributes 10-15 %. The W dominates for W Z

11. Motivation for Trigger Upgrade • Background from hadron decays from π’s, k’s into μ’s occur at 30 kHz level using the present level 1 trigger. • Build dedicated trigger muon spectrometer to reject the low momentum decay background and keep the high momentum W signal. • Use CMS RPC technology.

12. RPC2 RPC3 • Three dedicated trigger RPC stations (CMS design): • RPC1(a,b): ~180 segments inj, 2 in θ • RPC2: ~360 segments in j, 2 in θ • RPC3: ~360 segments in j, 2 inθ • (Trigger only – offline segmentation higher) RPC1(a+b) NSF (Funded) r=3.40m MuTr • MuTr front end electronics • Upgrade to allow LL1 information JSPS (Funded) PHENIX muon trigger upgrade

13. RPC Technology • HH.00012 : Design and R&D for the PHENIX Muon Trigger RPCs • Session HH: Instrumentation II • Young Jin Kim, UIUC, for the PHENIX Collaboration • 11:12 AM–11:24 AM, Saturday, October 13 • HH.00013 : Cosmic Ray Test Stand for the PHENIX Muon Trigger RPCs • Session HH: Instrumentation II • Beau Meredith, Graduate student at UIUC/PHENIX • 11:24 AM–11:32 AM, Saturday, October 13

14. Expected Performance of Trigger • The 30 kHz background from hadron decays will be reduced to about 1 kHz. • The DAQ will be able to handle about 9 kHz.

15. Issues in the Physics Analysis • Charge sign reconstruction required for AL W+ and AL W- determination • Smearing from momentum resolutions • Hadron decay ghosts • Requires two nuclear interaction lengths of absorber • With the absorber, the S/B improves from 1:3 to 3:1. • Work in progress: Study of asymmetry extraction including smearing, charge sign reconstruction and high PT ghosts.

16. W-backgrounds:Low pT Hadron Punch Through + Decay  Fake High pT Hadron decays in the MuTR can make tracks appear straighter High pT track

17. Solution to the Ghosts • Requires two nuclear interaction lengths of absorber • With the absorber, the S/B improves from 1:3 to 3:1. • Work in progress: Study of asymmetry extraction including smearing, charge sign reconstruction and high PT ghosts.

18. Conclusion • The upgrade to the front-end electronics of the muon tracker and the addition of a new subsystem based on resistive plate chamber (RPC) technology will allow the measurement of sea-quark contributions to the proton’s spin using the decay of W bosons to muons. This approach will avoid some of the complications of “hadron tagging”.

19. Unused Slides

20. Acknowledgments • PHENIX Collaboration and Forward Upgrade Group • Students: Joshua Adams, Amanda Caringi, Justine Ide, Phil Lichtenwalner • Dr. Rusty Towell, Dr. Ralf Seidl • ACU Students: Tim, Dan, Dillon, • DOE Intermediate Energy Nuclear Physics Division at BNL • UIUC, Faculty, post-docs, and graduate students • Special Thanks to Matthias Perdekamp

21. Motivation for W physics: sea polarization • Parity violating decay selects quark flavor: • Forward/backward region selects valence/sea quark helicity contribution • High luminosity and high √s=500 GeV needed • Measurement with PHENIX muon arms: • Only m± detected  control of backgrounds important • High energy muon trigger necessary • Advantages of W as probe: • Large Scale ( Q2~mW2) • no Fragmentation functions required

22. PHENIX ALW+/-Sensitivity • Machine and detector requirements: • ∫Ldt=800pb-1, P=0.7 at √s=500 GeV • Muon trigger upgrade! • Backgrounds: physics backgrounds such as Z0 pT>20 GeV, NZ/NW~0.15 • hadron punch through not signficant! (GEANT) • hadron punch through + decay (falsely reconstructed high momentum tracks) muon spectrometer + absorber S/B=3/1 (GEANT) • Unfold Δq,Δq from AL using experimental information on q(x), G(x), pQCD + resummation techniques: P.M. Nadolsky, C.P. Yuan Nucl.Phys.B666:3-30,2003 2009 to 2012 running at √s=500 GeV is projected to deliver ∫Ldt ~980pb-1 Projected PHENIX errors