Spin physics with PHENIX

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Spin physics with PHENIX

• RHIC Run-2 pp Results, Run-3 Preview and Future
  Measurements

Douglas E. Fields University of New
Mexico/Riken-BNL Research Center
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(No Transcript)
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Detector Overview

• Multi-purpose experiment
• Central Spectrometer
• Electrons
• Photons
• Hadrons
• Forward Spectrometer
• Muons
• Very Forward Detectors
• Triggering
• Centrality
• Polarimetry

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Detector Overview

• West Arm
• tracking
• DC,PC1, PC2, PC3
• electron ID
• RICH,
• EMCal
• photons
• EMCal

• East Arm
• tracking
• DC, PC1, TEC, PC3
• electron hadron ID
• RICH,TEC/TRD,
• TOF, EMCal
• photons
• EMCal

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Detector Overview

• Muon Tracking
• Radial field magnets
• 3 stations of cathode strip chambers
• 100mm resolution/plane 60mm resolution/station
• J/Y mass resolution 160MeV

• Muon Identification
• 5 layers of Irocci tubes
• x-y planes between steel absorber
• p/m rejection 10-4

• Zero-Degree Calorimeters
• hadron calorimeter
• neutron sensitive

• Beam-Beam Counters
• QuartzCherenkov radiators
• 3.0 lt ? lt 3.9

• Multiplicity-Vertex Detector
• Silicon strip

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Spin Physics Overview

• Physics
• Signal
• Single transverse-spin asymmetry
• neutron
• ?0
• charged hadron
• single muon from ? decay
• Gluon polarization
• jet production
• open heavy flavor
• J/?
• Flavor decomposed quark polarization
• W
• New physics with parity violation
• parity violating W
• Transversity

• PHENIX can see
• neutrons in ZDC/SMD
• gg in EMCal
• charged hadron (BBC or Central Arms)
• single muons in Muon Arms
• leading high pt in Central Arms
• e, m, e?, ??, and D?pK
• ee, mm in Central and Muon Arms
• high pT m in Muon Arms

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Transverse Spin Asymmetries

• Neutron asymmetry observed in IP12 while testing
  a local polarimeter designed to look for p0, g
  asymmetries

• Left-Right asymmetry measured for different
  slices in phi

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Phi Asymmetry

• Successful measurement of forward neutron
  asymmetry.
• Understood (?) in terms of SMEM.
• Large asymmetry gives good FOM for local (PHENIX)
  polarimetry.

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Local Polarimeter at PHENIX
Run-03
Spin Rotators OFF
Spin Rotators ON, Current Reversed
Yellow
Blue
Blue
Yellow
Spin Rotators ON, Correct!
Spin Rotators ON, Almost
PB35.5
PB37
P30, PT0 ? PL30)
P37, PT24 ?PL28)
Yellow
Blue
Yellow
Blue
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Transverse Spin Asymmetries

• Charged hadron asymmetry
• Measured using BBC,
• Hadrons in central arms
• Decay muons in Muon Arms

80 cm
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Longitudinal Double Spin Asymmetries
proton beam
? or ?
jet
gluon

• Would like to measure prompt photon in
  coincidence with jet.
• Requires higher luminosity and larger acceptance
  (STAR).
• Instead, (for now) measure leading p0 as a
  measure of jet.

photon
? or ?
proton beam
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Longitudinal Double Spin Asymmetries

• To determine DG, look at ALL
• R is the relative luminosity, and can be measured
  (to some accuracy) at PHENIX.
• Our Goal dR/R lt 0.1 for each fill? dALL lt
  210-3(expected ALL for pions 310-3 _at_PT3
  GeV/c)

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Relative Luminosity

• In order to investigate our ability to measure
  the relative ( vs. -) luminosity
• look at ratio of 2 detector scalars
  crossing-by-crossing
• a(i) NA(i)/NB(i)
• Ratio should be the same for all crossings
  (constant) if
• NA(i) L e and NB(i) L e
• B is always BBCLL1A is one of the others
  (CH2-8).
• Fit this by the expected pattern
• a(i) C1ALLPB(i)PY(i)
• C, ALL are the fitting parameters.
• Precision of relative luminosity can be estimated
  by
• dC/C
• If c2 of the fitting is bad, look for other
  factors in N(i).

Ratio of Zero-Degree Counter scalars to Beam-Beam
Counter scalars, sorted by bunch crossing and
fit to a constant.
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Correction factors

• What other factors could play a role in the
  determination of the scalar rate besides the
  luminosity?
• Vertex width
• Vertex width also measured crossing by crossing.
• Look for a correlation of the ZDC/BBC ratio with
  the vertex width
• Good correlation
• Can correct ratio for this factor.

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Limit on Relative Luminosity Measurement

• After correction for (measured) vertex width, the
  ratio of counts in the two detectors is
  consistent with constant up to our level of
  statistics
• This means that if we apply correction for this
  the precision on R goes from0.11 ?
  0.06
• (syst. limited) (stat. limited)

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Gluon Polarization

• Next step Measure cross-section as a test for
  perturbative QCD.
• In Run-02, precise measure of p0 cross-section.
• Test against perturbative QCD.

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Gluon Polarization

• PHENIX can measure J/Y ? ee-, mm-
• Can also measure open heavy quark decay to single
  and di-leptons (e, m, em-, e-m).
• Future upgrades to detect offset vertex.

GS95
DG(x)
cc?eX
bb?e?X
J/????
x
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Current J/Y From Run-02

• Using like-sign subtraction from lepton pairs

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Open Charm

• Single muons or electrons
• e-m coincidence
• Better

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SVT Upgrade
Strawman design under investigation Pixel barrels
(50 mm x 425 mm) Strip barrels (80 mm x 3
cm) Pixel disks (50 mm x 200 mm) 1.0 X0
per layer barrel resolution lt 50 mm forward
resolution lt 150 mm
1.2lthlt2.4
hlt1.2
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Spin Physics with SVT Upgrade

• Jet-axis for photonjet-axis ? constraint on x
• c?e, m displaced vertex low-x S/B, D?Kp high-x
• b?displaced J/y low/high-x, b?e, displaced vertex
  high -x

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Flavor Decomposed Quark Polarization

• At 500GeV/c2, PHENIX can measure W decay
  to single, high pt muons.
• W-production sensitive to polarized anti-quark
  and quark distributions
• interpretation of asymmetry theoretically well
  established
• insensitive to fragmentation functions
• insensitive to higher twist
• Experimental challenge
• acceptance for W ? ? X
• 1 nb cross-section at 500 GeV
• at 21032 cm-2s-1 ? 10000 W in 10 weeks
• reduce interaction rate 12 MHz to few kHz

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Muon Cherenkov Trigger Upgrade

• Possible solutions for an enhanced muon trigger
• forward hodoscopes
• anode readout
• cherenkov detector
• nosecone calorimeter

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Other Topics

• Transversity
• New Physics from Parity Violation

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Summary

• PHENIX is uniquely suited to the study of spin
  physics with a wide variety of probes.
• Run-02 gave us a solid baseline for transverse
  spin asymmetry, and cross-sections.
• So far, in Run-03, we have commissioned with
  longitudinal polarized protons (successful spin
  rotators) and are taking AMAP data for an ALL
  measurement using p0.
• We have studied our relative luminosity
  systematics and can make an ALL measurement that
  is statistics limited.
• We have an upgrade plan that will give us the
  triggers and vertex information that we need for
  precise future measurements of DG, Dq and new
  physics at higher luminosity and energy.