p 0 double longitudinal spin asymmetry in polarized pp collisions at 200 gev
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p 0 Double Longitudinal Spin Asymmetry in Polarized pp Collisions at .. = 200 GeV. Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration. D g 2. D g D q. D q 2. Motivation. with DS ~20%, D g, D L unknown. How to measure D g:. p 0. Hard Scattering Process.

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p 0 double longitudinal spin asymmetry in polarized pp collisions at 200 gev

p0 Double Longitudinal Spin Asymmetry in Polarized pp Collisions at .. = 200 GeV

Kieran Boyle (Stony Brook U.)

for

the PHENIX Collaboration

Kieran Boyle

PANIC—October 24,2005

motivation

Dg2

DgDq

Dq2

Motivation

with DS ~20%, Dg, DL unknown

How to measure Dg:

p0

Hard Scattering Process

~ agg * Dg2 + bgq * Dg + cqq

Kieran Boyle

PANIC—October 24,2005

a ll requirements
ALL Requirements
  • PHENIX
  • p0 Cross section
  • Relative Luminosity (R=L++/L+-)
    • dR=1.0e-4
  • (Local) Polarimetry
  • ALL
    • Method
    • Result

++ same helicity

+ opposite helicity

Kieran Boyle

PANIC—October 24,2005

phenix detector

BBC

ZDC

ZDC

PHENIX Detector

PbSc

p° detection

  • Electromagnetic Calorimeter:
      • High pT photon trigger to collect p0\'s
      • Acceptance: h<|0.35|, f = 2x p/2
      • High granularity (~10*10mrad2)

Relative Luminosity

  • Beam Beam Counter (BBC)
      • Acceptance: 3.0< h<3.9
  • Zero Degree Calorimeter (ZDC)
      • Acceptance: ±2 mrad

Local Polarimetry

  • ZDC

PbGl

Kieran Boyle

PANIC—October 24,2005

g g mass spectrum
g-g Mass Spectrum

Kieran Boyle

PANIC—October 24,2005

run5 p 0 cross section
Run5 p0 Cross Section
  • Consistent with previous results.
  • Extends previous results to pT of 20 GeV/c.
  • Theory is consistent with data over nine orders of magnitude.

Kieran Boyle

PANIC—October 24,2005

relative luminosity
Relative Luminosity
  • Number of BBC triggered events used to calculate Relative Luminosity.
  • For estimate of Uncertainty, fit

where

  • dR=1.0e-4
  • dALL=2.3e-4
  • ALL of BBC to ZDC consistent with zero

Kieran Boyle

PANIC—October 24,2005

local polarimetry at phenix
Use ZDC to measure a L-R and U-D asymmetry in forward neutrons.

When transversely polarized, we see clear asymmetry.

When longitudinally polarized, there should be no asymmetry.

Local Polarimetry at PHENIX

Raw asymmetry

Raw asymmetry

BLUE

YELLOW

Idea: Use neutron asymmetry to study transversely polarized component.

f

f

Kieran Boyle

PANIC—October 24,2005

measured asymmetry during longitudinal running

LR

c2/NDF = 82.5/97

p0 = -0.00423±0.00057

c2/NDF = 88.1/97

p0 = -0.00323±0.00059

UD

XF>0

XF>0

UD

c2/NDF = 119.3/97

p0 = -0.00056±0.00063

c2/NDF = 81.7/97

p0 = -0.00026±0.00056

LR

XF<0

XF<0

Measured Asymmetry During Longitudinal Running

<PT/P>=

10.25±2.05(%)

<PL/P> =

99.48±0.12±0.02(%)

<PT/P>=

14.47±2.20(%)

<PL/P> =

98.94±0.21±0.04(%)

Kieran Boyle

PANIC—October 24,2005

Fill Number

Fill Number

calculating a ll
Calculating ALL
  • Calculate ALL(p°+BG) and ALL(BG) separately.
  • Get background ratio (wBG) from fit of all data.
  • Subtract ALL(BG) from ALL(p°+BG):

ALL(p°+BG) = wp° · ALL(p°) + wBG · ALL(BG)

p°+BG region :

±25 MeV around

p° peak

BG region :

two 50 MeV regions

around peak

Kieran Boyle

PANIC—October 24,2005

fill by fill a ll
Fill by Fill ALL

Kieran Boyle

PANIC—October 24,2005

bunch shuffle
Bunch shuffle

1<pT<2 GeV/c 2<pT<3 GeV/c 3<pT<4 GeV/c 4<pT<5 GeV/c

  • Randomly reassign helicity for each fill and recalculate asymmetry.
  • Do 1000 times and look at c2 distribution.
  • Agree with expected distribution
  • Bunch to bunch systematics smaller than current statistics.

5<pT<6 GeV/c 6<pT<7 GeV/c 7<pT<8 GeV/c 8<pT<9 GeV/c

Kieran Boyle

PANIC—October 24,2005

a l consistent with zero
AL consistent with zero

Kieran Boyle

PANIC—October 24,2005

p 0 a ll
p0 ALL
  • Comparison with previous Runs
  • Confidence levels:
    • Run3 : 17.6 %
    • Run4 : 18.7 %
  • They are consistent. (Scale error is not considered.)

Kieran Boyle

PANIC—October 24,2005

comparison with theory
Comparison with theory

¨

GRSV: M. Gluck, E. Reya, M. Stratmann, and W. Vogelsang, Phys. Rev. D 53 (1996) 4775.

* At input scale: Q2 = .4 GeV

Kieran Boyle

PANIC—October 24,2005

values for a ll and a l
Values for ALL and AL

* At input scale: Q2 = .4 GeV

Kieran Boyle

PANIC—October 24,2005

conclusions
Conclusions
  • We measured cross section and double helicity asymmetry ALL in p0 production from Run5 pp collision.
  • The results of ALL are consistent with Run3/4.
  • The data are compared with theoretical models.
  • Run5 conclusively excludes GRSV maximal scenarios.
  • Data consistent with GRSV standard and GRSV DG = 0.

Kieran Boyle

PANIC—October 24,2005

backups

Backups

Kieran Boyle

PANIC—October 24,2005

photon trigger efficiency
Photon Trigger Efficiency

Kieran Boyle

PANIC—October 24,2005

distinct and merged photons
Distinct and Merged Photons

Kieran Boyle

PANIC—October 24,2005

slide21
Minimum Bias (BBC |z|<30)
  • Minimum Bias in coincidence with High Energy Photon trigger (Cluster Energy>1.4GeV)

Kieran Boyle

PANIC—October 24,2005

slide22
Cross Section consistant with Run3 result.

Kieran Boyle

PANIC—October 24,2005

yellow beam
Yellow Beam

LR

c2/NDF = 119.3/97

p0 = 0.00727±0.00060

c2/NDF = 68.1/97

p0 = -0.00226±0.00069

UD

XF>0

<PT/P>=

14.47±2.20(%)

<PL/P> =

98.94±0.21±0.04(%)

XF>0

UD

c2/NDF = 82.3/97

p0 = -0.00067±0.00064

c2/NDF = 83.0/97

p0 = -0.00089±0.00061

LR

XF<0

XF<0

Kieran Boyle

PANIC—October 24,2005

slide24

BRAHMS & PP2PP (p)

PHENIX (p)

STAR (p)

RHIC

RHIC CNI (pC) Polarimeters

Absolute Polarimeter

(H jet)

Siberian Snakes

Spin Rotators

2  1011 Pol. Protons / Bunch

e = 20 p mm mrad

Partial Siberian Snake

LINAC

BOOSTER

Pol. Proton Source

500 mA, 300 ms

AGS

AGS Internal Polarimeter

200 MeV Polarimeter

Rf Dipoles

RHIC accelerates polarized protons to (presently) 100 GeV

Kieran Boyle

PANIC—October 24,2005

p 0 production
p0 Production

Kieran Boyle

PANIC—October 24,2005

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