W Production in Polarized p-p Collisions: A Probe for Sea Quark Spin

W Production in Polarized p-p Collisions: A Probe for Sea Quark Spin

Daniel JumperUniversity of Illinois Urbana-ChampaignFor the PHENIX CollaborationDNP Meeting - October 25th, 2012

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Outline

Proton Spin StructureW Asymmetry MeasurementPHENIX and RHICAnalysis and Initial Results2013 Run Projections

Daniel Jumper - DNP 2012

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Proton Spin StructureContributions to proton spin:

20 years of DIS/SIDIS measurements DIS: Sensitive to quark

antiquark sum SIDIS: Limited precision

Recent work: pp collisions at RHIC

Phys. Rev. D 80, 034030 (2009)


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Proton Spin StructureContributions to proton spin:

20 years of DIS/SIDIS measurements DIS: Sensitive to quark

antiquark sum SIDIS: Limited precision

Recent work: pp collisions at RHIC

Our measurement focuses on , specifically and

Phys. Rev. D 80, 034030 (2009)


5Sea Quark Spin: Using the Weak InteractionStudy single spin asymmetry in production cross section of W bosons in polarized pp collisions at =500 GeVPolarized proton beams with different possible longitudinal

polarization orientationsW produced in Quark-antiquark annihilation decays into

lepton/neutrino.Advantages:

High (lower NLO sensitivity)No dependence on fragmentation functionsMore direct flavor and antiquark sensitivity

𝑊 ±


6Single Spin Asymmetry in W Boson Production

Observe W decay at forward rapidity

Leading Order picture: flavor decomposition , , , ,

Simulations show the measurement remains sensitive even with NLO considerations


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Polarized pp at RHICPolarized pp collisions at =200-500 GeV

Longitudinal or transverse

“Siberian Snakes”Flip spin twice per

rotation Lessens depolarizing

effects of acceleratorRandomized spin

direction per bunch Alternating spin patterns

give more consistent relative luminosity


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Polarized pp at RHICPolarized pp collisions at =200-500 GeV

Longitudinal or transverse

“Siberian Snakes”Flip spin twice per

rotation Lessens depolarizing

effects of acceleratorRandomized spin

direction per bunch Alternating spin patterns

give more consistent relative luminosity


9PHENIX Forward Muon Trigger Upgrade

Experimental Challenge:Trigger dominated by background especially at low

Solution:Upgraded trigger system: Tracking detectors now included in trigger

allowing discrimination RPC detectors added

Precise timing rejects non-collision related background

Additional tracking pointNew vertex tracker


10Signal Background and Simulations

Simulations developed for 2011 analysis

Accurate estimated background levels in simulation used for correction factor in real data


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Initial Results2011 Results

~25 Luminosity~50% Polarization

2012 Run: Analysis in progress~50 Luminosity

Largest portion of data will come from upcoming 2013 run

2011 run results


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Projected Results

Projection for 500 delivered luminosity~55% polarization


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ConclusionW Asymmetry offers a cleaner

and more direct probe of sea quark spin

PHENIX’s forward upgrade is ready for W measurmentAn analysis framework is in

place

2013 statistics will make a significant contribution toward tighter constraints of ,

Courtesy of Daniel de Florian, Rodolfo Sassot, Marco Stratmann,

and Werner Vogelsang


W Production in Polarized p-p Collisions: A Probe for Sea Quark Spin

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