1 Run 9 PHENIX Goals and Performance John Haggerty Brookhaven National Laboratory June 4, 2009

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 June 4, 20092

200 GeV p+p Physics Goals Primary goal is to elucidate the gluon contribution to proton spin Double longitudinal spin asymmetry A LL is sensitive to ΔG –PHENIX particularly well suited for high statistics π 0 –Control of systematic uncertainties vital as statistical uncertainties decrease –Other channels possible contingent on statistics (π ±, η, direct photon) June 4, 20093

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

Muon arms upgrades MUTRIG –Adds ability to trigger on muon momentum RPC –Adds excellent timing resolution Absorber –Reduces background June 4, 20095

Muon trigger upgrade June 4, 20096

MUTRIG performance June 4, Minimum Ionizing Particle 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

RPC June 4, Why Resistive Plate Chambers? –Fast response –Good spatial resolution –Low cost, CMS experience Engineering run for sectors in 2 planes on south arm

RPC prototypes June 4, From collision or out going beam From beam background Already the ~3 ns time resolution, current draw, and hit rate have helped understand background

Hadron Blind Detector June 4, CsI photocathode covering triple GEMs Windowless Cerenkov detector with CF 4 avalanche/radiator gas (2 cm pads) Designed for low mass dilepton pairs in heavy ions but commissioned in p+p

HBD performance June 4, Single electronsDouble electrons  -z matching 20 pe40 pe Electrons from Dalitz pairs in the mass region below 150 MeV. The number of photoelectrons is ~22, more than 50% increase from Run 7

PHENIX polarimeter “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 June 4, RED : yell pol. ↑ BLUE : yell pol. ↓ RED : blue pol. ↑ BLUE : blue pol. ↓ Transverse (10371)

Trigger and data acquisition June 4, Selected triggers logged to separate streams for “Fastrak” analysis DAQ and trigger evolution keep livetime ~90% while recording 7 kHz

500 GeV longitudinally polarized p+p June 4, * Preliminary luminosity numbers—cross sections and acceptances still work in progress 43 physics fills in 28 days 220 TB recorded physics 50.2 pb -1 delivered Polarization ~35%

First half of 200 GeV longitudinally polarized p+p June 4, physics fills in first 5 weeks 200 TB recorded 30.2 pb -1 delivered Polarization ~ 53%

Longitudinal polarization at PHENIX June 4, ReferenceRunL (analyzed) L 2 Phys. Rev. D 73:091102, 2006 Run 3 Run pb pb -1 35% 45% 30% 44% pb pb -1 Phys. Rev. D 76:051106,2007 Run 52.5 pb -1 50%49%0.15 pb -1 arXiv: (PRL) Run 66.5 pb -1 56%57%0.66 pb GeVRun 9>8 pb -1 ~55% >0.75 pb GeVRun 9~13 pb -1 ~35%

Muon arm J/ψ June 4, GeV200 GeV Production of muon stream allowed us to see J/ψ during the run NNSS

Central arm analyses June 4, Unsubtracted e + e - spectrum Calorimeter gain changed by factor ~2 for 500 GeV W program

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 June 4,

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…. June 4,