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 neutrons.

    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 A neutrons.LL

    • 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 A neutrons.LL

    Kieran Boyle

    PANIC—October 24,2005


    Bunch shuffle
    Bunch shuffle neutrons.

    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
    A neutrons.L consistent with zero

    Kieran Boyle

    PANIC—October 24,2005


    P 0 a ll
    p neutrons.0 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 neutrons.

    ¨

    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 A neutrons.LL and AL

    * At input scale: Q2 = .4 GeV

    Kieran Boyle

    PANIC—October 24,2005


    Conclusions
    Conclusions neutrons.

    • 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 neutrons.

    Kieran Boyle

    PANIC—October 24,2005


    Photon trigger efficiency
    Photon Trigger Efficiency neutrons.

    Kieran Boyle

    PANIC—October 24,2005


    Distinct and merged photons
    Distinct and Merged Photons neutrons.

    Kieran Boyle

    PANIC—October 24,2005


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

    Kieran Boyle

    PANIC—October 24,2005


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

    Kieran Boyle

    PANIC—October 24,2005


    Yellow beam
    Yellow Beam neutrons.

    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


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

    BRAHMS & PP2PP (p) neutrons.

    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
    p neutrons.0 Production

    Kieran Boyle

    PANIC—October 24,2005