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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

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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)

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Neutral pion production asymmetry projection

June 4, 2009 4

arXiv:0810.0694 (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

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Muon trigger upgrade

June 4, 2009 6

MUTRIG performance

June 4, 2009 7

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

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• 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

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From collision orout going beam

From beambackground

Already the ~3 ns time resolution, current draw, and hit rate have helped understand background

Hadron Blind Detector

June 4, 2009 10

CsI photocathode covering triple GEMs

• 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

HBD performance

June 4, 2009 11

Single electrons Double electrons

-z matching

20 pe 40 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

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RED : yell pol. ↑ BLUE : yell pol. ↓

RED : blue pol. ↑ BLUE : blue pol. ↓

Transverse (10371)

Trigger and data acquisition

June 4, 2009 13

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

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* 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

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• 74 physics fills in first 5 weeks• 200 TB recorded• 30.2 pb-1 delivered• Polarization ~ 53%

Longitudinal polarization at PHENIX

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Reference Run L (analyzed) <PB> <PY> L <PB PY>2

Phys. Rev. D 73:091102, 2006

Run 3Run 4

0.220 pb-1

0.075 pb-1

35%45%

30%44%

0.0026 pb-1

0.0029 pb-1

Phys. Rev. D 76:051106,2007

Run 5 2.5 pb-1 50% 49% 0.15 pb-1

arXiv:0810.0694 (PRL)

Run 6 6.5 pb-1 56% 57% 0.66 pb-1

200 GeV Run 9 >8 pb-1 ~55% ~55% >0.75 pb-1

500 GeV Run 9 ~13 pb-1 ~35% ~35%

Muon arm J/ψ

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500 GeV 200 GeV

Production of muon stream allowed us to see J/ψ during the run

N NS S

Central arm analyses

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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

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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….

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