Run 9 PHENIX Goals and Performance

1. Run 9 PHENIX Goals and Performance John Haggerty Brookhaven National Laboratory

2. 500 GeV p+p Physics Goals • Detection and cross section measurement for W± →e± in central arms (|η|< 0.35, σ~20 pb) • Measure single spin asymmetry with longitudinally polarized p+p • Characterize upgraded muon arm performance at 500 GeV and understand backgrounds in forward W

3. 200 GeV p+p Physics Goals • Primary goal is to elucidate the gluon contribution to proton spin • Double longitudinal spin asymmetry ALL is sensitive to ΔG • PHENIX particularly well suited for high statistics π0 • Control of systematic uncertainties vital as statistical uncertainties decrease • Other channels possible contingent on statistics (π±, η, direct photon)

4. Neutral pion production asymmetry projection Expected uncertainty for 25 pb-1 60% polarization arXiv:0810.0694 (PRL)

5. Muon arms upgrades • MUTRIG • Adds ability to trigger on muon momentum • RPC • Adds excellent timing resolution • Absorber • Reduces background

6. Muon trigger upgrade

7. MUTRIG performance • Good efficiency with 30 mV threshold • Operational in MUTR.N for the entire run • Installed for test in MUTR.S to cover RPC • Prototype trigger logic being tested Station 1 Station 2 Station 3 Minimum Ionizing Particle

8. RPC • Why Resistive Plate Chambers? • Fast response • Good spatial resolution • Low cost, CMS experience • Engineering run for sectors in 2 planes on south arm

9. RPC prototypes Already the ~3 ns time resolution, current draw, and hit rate have helped understand background From collision or out going beam From beam background

10. Hadron Blind Detector • Windowless Cerenkov detector with CF4 avalanche/radiator gas (2 cm pads) • Designed for low mass dilepton pairs in heavy ions but commissioned in p+p CsI photocathode covering triple GEMs

11. HBD performance Electrons from Dalitz pairs in the mass region below 150 MeV. The number of photoelectrons is ~22, more than 50% increase from Run 7 Single electrons Double electrons f-z matching 20 pe 40 pe

12. PHENIX polarimeter RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓ • “Shower Max Detector” segment of the ZDC instrumented for rapid polarimetry • FEM’s reprogrammed to send discriminator data to FPGA so that 8*120 scaler channels can accumulate reasonable statistics in 5 minutes on L-R asymmetries Transverse (10371)

13. Trigger and data acquisition Selected triggers logged to separate streams for “Fastrak” analysis DAQ and trigger evolution keep livetime ~90% while recording 7 kHz

14. 500 GeV longitudinally polarized p+p • 43 physics fills in 28 days • 220 TB recorded physics • 50.2 pb-1 delivered • Polarization ~35% * Preliminary luminosity numbers—cross sections and acceptances still work in progress

15. First half of 200 GeV longitudinally polarized p+p • 74 physics fills in first 5 weeks • 200 TB recorded • 30.2 pb-1 delivered • Polarization ~ 53%

16. Longitudinal polarization at PHENIX

17. Muon arm J/ψ N S N S 500 GeV 200 GeV Production of muon stream allowed us to see J/ψ during the run

18. Central arm analyses Calorimeter gain changed by factor ~2 for 500 GeV W program Unsubtracted e+e- spectrum

19. PHENIX in Run 9 • New detectors necessary for future spin running commissioned—MUTRIG, RPC • Hadron Blind Detector brought into operation • First polarized p+p collisions at 500 GeV • Substantial amount of data accumulated • Polarization must be higher for spin physics, but polarization is preserved to 250 GeV • First half of 200 GeV run duplicated the Run 6 data set

20. Thanks It’s impossible to thank everyone who contributed to this huge 24x7 six month effort… MCR… ~300 PHENIX shift takers…everyone who contributed figures….