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(longitudinal) Spin Program at RHIC-PHENIX. K.Aoki for the PHENIX Collaboration Kyoto Univ. / RIKEN Nishina center INPC2007 Tokyo, Japan. Introduction. Proton has spin ½ Its decomposition still not yet understood well.

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longitudinal spin program at rhic phenix
(longitudinal) Spin Program atRHIC-PHENIX

K.Aoki for the PHENIX Collaboration

Kyoto Univ. / RIKEN Nishina center

INPC2007 Tokyo, Japan

introduction
Introduction
  • Proton has spin ½
    • Its decomposition still not yet understood well.
      • Quark spin carries only ~30% of proton spin. – “proton spin puzzle”
      • The rest should come from gluon spin, and orbital angular momentum of quarks and gluons.
  • PHENIX longitudinal spin program
    • Reveal the spin structure of proton, especially Dg (gluon spin contribution to the proton) which still has large uncertaninty.
    • Through “Double Helicity Asymmetry(ALL)” of particle production (such as p0) in polpp collisions
      • gluons participate in leading order. suitable to probe gluon spin!
  • RHIC -- the world’s first polarized pp collider

K.Aoki (Kyoto Univ. / RIKEN)

a ll of p 0 in pol pp collisions
ALL (of p0) in pol. pp collisions
  • Theoretically
  • N: particle yield
  • P: polarization of beams
  • R: Relative Luminosity

s++=

proton

Proton’s helicity

s+-=

jet

proton

p0

  • Experimentally

These two processes dominates

In our sensitive pT region.

strategy

  • X-section measurement to confirm pQCD applicability
  • ALL measurement to extract Dg

K.Aoki (Kyoto Univ. / RIKEN)

rhic the world s first pol pp collider1
RHIC – the world’s first pol pp collider

Longitudinal spin program

Transverse spin program

  • Talk by M.Chiu (next speaker)

(plan)

FOM: Figure of Merit

K.Aoki (Kyoto Univ. / RIKEN)

rhic beam at phenix ip
RHIC beam at PHENIX IP
  • Two independent beams(Blue / Yellow)
  • Bunch structure (120 bunchs in ~106ns interval )
  • TransverseLongitudinal at IP (when we need it)
  • Spin pattern
    • Syst. uncertainty from time-dep. of the det. eff. avoided.

BLUE : + + - - ….

Yellow: + - + - ….

We can get all possible

Collision patterns.

K.Aoki (Kyoto Univ. / RIKEN)

phenix global detector

BBC

ZDC+SMD ( Local Polarimeter )

PHENIX global detector

Luminosity Measure

  • BBC3.0<|h|<3.9
    • Quartz Cherenkov det.
  • ZDC |h|>6.6 (+/- 2.8mrad.)
    • Hadron Calorimeter

These two independent lumi. measure

are compared to find out uncertainty

on Relative Lumi.

Local Polarimetry

  • SMD (+ ZDC).
    • Scintillator hodoscopes.
    • Measures transverse component of beam through AN of neutron.

K.Aoki (Kyoto Univ. / RIKEN)

phenix detector
PHENIX Detector
  • PHENIX has ability to detect various final state particles such as p0,p+-,g,e+- and m+-. Here I concentrate on p0(or g) detection.
  • |h|<0.35, Df ~ 2 x 90deg
  • EMCal(PbSc,PbGl) for g measurement. p0 detected via gg decay.
  • High energy photon trigger available

Central Arm

beam

K.Aoki (Kyoto Univ. / RIKEN)

slide9

cross section – pQCD applicability

RUN5 200GeV -- p0

arXiv:0704.3599 [hep-ex]

RUN5 200GeV – direct g

pQCD

works

K.Aoki (Kyoto Univ. / RIKEN)

cross section pqcd applicability
cross section – pQCD applicability

RUN5 200GeV -- p0

arXiv:0704.3599 [hep-ex]

RUN6 62.4GeV -- p0

pQCD

works

K.Aoki (Kyoto Univ. / RIKEN)

p 0 a ll at 200gev
p0 ALL at 200GeV

RUN5 200GeV – p0

Submitted to PRL

arXiv:0704.3599 [hep-ex]

  • GRSV theory curves
    • Std: best fit to DIS data.
    • DG=G(x),0,-G(x) are also shown

DG=G(x),-G(x) are excluded.

Dashed / dotted lines

corresponds to +-9.4%

scale uncertainty.

9.4% Scale uncertainty is not included

DG [x=0.020.3] (Q2=1GeV2)

K.Aoki (Kyoto Univ. / RIKEN)

p 0 a ll at 200gev run6
p0 ALL at 200GeV RUN6

Run5 prelm. 1.8pb-1 (pol:47%)

Run6 prelim. (high pT) 7.5pb-1 (pol:60%)

  • High pT photon extracted from data virtually online (Lvl.2 filtering) for fast track analysis

Significant statistical imrpovement in high pT

K.Aoki (Kyoto Univ. / RIKEN)

access higher x with lower energy
Access higher x with lower energy

pol

  • Probed xscales with xT
  • At fixed xT, X-sec is 2 orders of magnitude higher at 62.4GeV than at 200GeV

200GeV prelm. 1.8pb-1 (47%)

62.4GeV prelm. 0.04 pb-1 (48%)

Scaling variable

Significant statistical improvement in high xT even with small int. lumi can be seen.

K.Aoki (Kyoto Univ. / RIKEN)

various channels available at phenix to explore gluon pol
Various channels available at PHENIX to explore gluon pol.
  • Jet ( or a component of jet )
  • Direct photon
  • Heavy Flavor

g

  • p0 ,h (gg)
  • p+-
  • jet-like cluster

g

proton

proton

g

q

jet

proton

p0

jet

proton

p0

g

g

  • g

proton

q

proton

  • e+-
  • m+-
  • J/y (e+e-, m+m-)

eor m

g

D

`c

proton

g

c

or `cc J/y

proton

K.Aoki (Kyoto Univ. / RIKEN)

summary
summary
  • PHENIX longitudinal spin program is to reveal the spin structure of proton, especially Dg which has a large uncertainty.
  • PHENIX cross-section measurements are shown. The results confirm pQCD applicability which Dg extraction framework relies on.
  • PHENIX - ALLp0 excludes large |Dg| scenarios.
    • Statisical improvement expected in the next run.
  • complementary measurements will be obtained from other channels.
  • We’ll accumulate 70pb-1(70% pol.) at 200GeV in 2008(RUN8)

K.Aoki (Kyoto Univ. / RIKEN)

back up slides
Back up slides

K.Aoki (Kyoto Univ. / RIKEN)

information on the session
Information on the session
  • Nucleon Structure II
    • Session Name:D3, Hall Name:G409

K.Aoki (Kyoto Univ. / RIKEN)

slide18

何故 √s = 62.4GeVがうれしいか?

62.4 GeV

200 GeV

スケーリング

変数

500 GeV

[pb/GeV]

測定領域

62.4GeV

200GeV

(注)下限は、pT>1GeVの要請から

  • 同じ xTで比較して、200GeVと比べて2桁大きい。
  •  衝突エネルギーを、

 全て横に持って行った場合。

  • 少ない積分輝度で、有意な結果が得られる。
  • 高い xTは、高い xをプローブする。

K.Aoki (Kyoto Univ. / RIKEN)

phenix detector central arm
PHENIX Detector – Central Arm

K.Aoki (Kyoto Univ. / RIKEN)

slide20

PHENIX: g detection.(62GeV)

EMCal

Trigger

  • Acceptance - |h|<0.35 , Df=90 x 2
  • Energy resolution
  • Position resolution

high energy cluster at EMCal. (~800MeV) w/o BBC

  • BBC efficiency for p0 event(hard scattering) is low (~40%)

p0 reconstruction

  • Minimal photon energy cut
    • 0.1 GeV for PbSc
    • 0.2 GeV for PbGl
  • Shower profile cut
  • Energy asymmetry cut
  • Trigger tile matching. (for higher energy cluster)

K.Aoki (Kyoto Univ. / RIKEN)

slide21

Longitudinality (62.4GeV)

Longitudinal 100% (-2.2%)

Transverse 21% (1s uncertainty)

ZDC detector

neutron

What we measure.

What we want.

Blue beam

Forward

Blue Beam

Backward

Horiz-position(cm)

Horiz-position(cm)

Yellow Beam

Forward

Yellow Beam

Backward

Red : Rotator OFF

Blue : Rotator ON

Horiz-position(cm)

Horiz-position(cm)

K.Aoki (Kyoto Univ. / RIKEN)

slide22

Theory curve by W. Vogelsang

K.Aoki (Kyoto Univ. / RIKEN)

slide23

Cross section measurements

(charm) PRL97 252002: Run5

Electron

(from Charm, Beauty)

K.Aoki (Kyoto Univ. / RIKEN)

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