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Current Results and Future Prospects from. Kieran Boyle (RIKEN BNL Research Center). Topics. Longitudinal Spin Current results Future plans/ideas W physics Plans A first look at Run9 data Transverse Spin Current Results Future plans. RHIC and PHENIX. A few standard slides. RHIC.

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kieran boyle riken bnl research center

Current Results and Future Prospects from

Kieran Boyle

(RIKEN BNL Research Center)

  • Longitudinal Spin
    • Current results
    • Future plans/ideas
  • W physics
    • Plans
    • A first look at Run9 data
  • Transverse Spin
    • Current Results
    • Future plans
rhic and phenix


A few standard slides





STAR (p)

RHIC CNI (pC) Polarimeters

Absolute Polarimeter

(H jet)

Siberian Snakes

Spin Rotators

Partial Siberian Snake



Pol. Proton Source



AGS Internal Polarimeter

200 MeV Polarimeter


Rf Dipoles

In progress

phenix detector


PHENIX Detector

p0, h, g detection

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

p+/ p-

  • Drift Chamber (DC) for Charged Tracks
  • Ring Imaging Cherenkov Detector (RICH)
      • High pT charged pions (pT>4.7 GeV).

W± from e±

  • EMCal: triggering and energy determination
  • DC: Sign determination

W± from ±

  • Muon Identification (MuID)
  • Tracking (MuTR)
  • Triggering (RPC and MuTrig Upgrades)

Relative Luminosity and Local polarimetry

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




constraining g

Hard Scattering Process





Constraining G

Current Longitudinal Spin Program

with DS ~25%, DG not as well constrained, L?

why a ll
Why ALL?
  • If Df = Dq, then we have this from pDIS
  • So roughly, we have

From e+e-

(& SIDIS,pp)

From ep (&pp)

(HERA mostly)


+- =





pqcd works
pQCD works

Direct g @ 200 GeV

p0 @ 200 GeV

arXiv:0704.3599 [hep-ex]

a ll results
ALL Results

Large number of independent probes

Accepted in PRL:


focus on 0
Focus on 0
  • Why 0?
    • Nothing special about 0 physically
    • Similar to other single hadron or jet measurements
    • Pions are abundantly produced in p+p collisions
    • 0 ~99% of the time
    • PHENIX triggering on high pT photons ensures large sample
    • Fragmentation Function is also reasonably well known
      • Will get better with BELLE data
    • Marquee measurement in the age of

low luminosities.

constraining g1
Constraining G
  • Vary G in GRSV fit, and then generate ALL.
  • Calculate 2 for each expectation curve, and plot profile


Use combined Run5 and Run6 results

recent global fit dssv
PRL 101, 072001(2008)

First truly global analysis of polarized DIS, SIDIS and pp results

PHENIX s = 200 and 62 GeV data used (PRELIMINARY 2006)

RHIC data significantly constrain G in range 0.05<x<0.3

Experimental systematic uncertainties must be included taking into account correlations.

Theoretical uncertainties must be considered. See recent paper.

Recent Global Fit: DSSV
systematic uncertainty impact
Systematic Uncertainty Impact

Accepted in PRL: arXiv:0810.0694

  • Consider impact of dominant uncertainties:
    • Polarization
    • Relative luminosity
  • Polarization has negligible impact on G constraint
  • Relative luminosity though small (4.6x10-4) is not neglible
  • G(syst) = 0.1
parameterization uncertainties
Parameterization Uncertainties

Parameterization choice

  • Vary g’(x) =g(x) for best fit, and generate many ALL
  • Get 2 profile
  • At 2=9 (~3), we find consistent constraint:

-0.7 < G[0.02,0.3] < 0.5

 Our data are primarily sensitive to the size of G[0.02,0.3].

scale uncertainty
Scale Uncertainty

Theoretical Scale Uncertainty:

  • 0 cross section is described by NLO pQCD within sizable uncertainty in theoretical scale 
  • How does this affect G constraint?
  • Vary scale in ALL calc.

 0.1 uncertainty for positive constraint

 Larger uncert. for negative constraint

direct photon g constraint

R. Bennett’s


Direct Photon G Constraint


  • Dominated by quark-gluon

Compton scattering

  • Distinct process from other current RHIC probes
  • At Leading Order
  • Calculate most probable x(gluon) for given pT
    • Monte Carlo
  • Get A1p from DIS experimental result
    • PRD 60 (99) 072004
  • Partonic asymmetries calculable in pQCD
    • Phys.Rept.59:95-297,1980
g g from direct photon

R. Bennett’s


G/G from Direct Photon
  • Current data are ~10 pb-1, so very limited statistics
  • If we get expected luminosities and polarizations at 200 (and in future) 500 GeV, will offer significant constraint.
future for phenix g

Future for PHENIX G

Lower x, correlations and Higher Luminosity

s 500 gev
Higher s allows access to lower x

For W program, we need significant luminosity (~300 pb-1)

For ALL, if polarization is >60%, this will allow for a very accurate measurement of G.

We will of course repeat our measurements

ALL expected to be small

Systematic uncertainties will become significant at low pT, where lowest x is reached.

present (0)


s = 200 GeV

Extend to higher x at s = 62.4 GeV

Extend to lower x at s = 500 GeV

s=500 GeV
expectation for 0 a ll
Expectation for 0 ALL
  • Limited at high pT due to merging of photons as opening angle decreases
  • Relative luminosity systematic uncertainty must be reduced.

Full spin


particle correlations
Particle Correlations
  • Due to limited acceptance, Jet-Jet measurement is extremely difficult in PHENIX.
  • Two particle correlations can be measured, though this introduces two fragmentation functions.
  • Also will look at photon-hadron correlations.
silicon vertex detector vtx

|h| < 0.35

Direct g





|hjet| < 1.2

Silicon Vertex Detector (VTX)
  • Four layers (2 pixel, 2 stripixel)
  • Allow access to G through distinct processes
    • Heavy flavor via displaced vertices
    • Gamma-Jet (isolated trigger photon in EMCal, charged energy from VTX)

Heavy flavor

  • DCA resolution ~50m
  • c/b separation by c

Life time (ct)

D0 : 125 mm

B0 : 464 mm



Gamma Jet

  • Large acceptance:

||<1, ~2 for 






w bosons at phenix

W-bosons at PHENIX

Accessing the flavor dependent quark sea spin distributions


two ways to get w


Two ways to get W
  • Central Rapidity: ||<0.35
    • Measure electron in the central arms EMCal
    • Determine charge sign from tracking
  • Forward/Backward: 1.2<<2.4
    • Measure muon in muon arms
    • W dominates muon signal above 20 GeV
    • For measurement, we require:
      • Ability to trigger on high momentum 
      • Hadron background reduction
    • Upgrading PHENIX for this purpose

Muon pT spectra in the Muon Arms

(2000 [1/pb], from PYTHIA5.7)

μ ±


  • Expectations based on 300 pb-1, 60% pol.
  • Different rapidities select different polarized quark and anti quark distributions

Forward AL μ+

Forward AL μ-

Backward AL μ+

Backward AL μ-


Rapidity: 1.2 < h <2.2 (2.4)

  • <Muon Trigger Upgrade>
  • MuTr FEE Upgrade (MuTRG)
  • Install RPC (Resistive Plate Chamber)
  • Install additional Pb absorber
  • MuID
  • - only existing trigger
  • no momentum selectivity..


w e in central arms
We in Central Arms
  • Cross section of e+/- from W & π+/- in the PHENIX acceptance.
  • Expected asymmetry of W (assuming 70 % polarization, no background or detector resolution included)

pions: NLO pQCD calculation from W. Vogelsang

W: RHICBOS (Nadolsky, Yuan)





<Charged hadron rejection>

EMCal intrinsic: 50-150

Shower profile: 2-4

Isolation cut: ~10

Total: 1000-6000

w e run 9
We Run 9

Energy v.s. Inclination of the track

  • Polarization ~35%
  • Luminosity ~10%

 Measure cross section

  • alpha [rad.] ~ 0.1/ mom [GeV/c]
  • “energy / mom < 3” cut applied

negative charge

positive charge


Energy dist. (Black: +, Red: -)

Only analyzed part of data set


event display of high energy events
Event Display of High energy events

Found W candidates.

Analysis is under way!

3. W detection @ PHENIX


a n from p 0 h 0 35
AN from p0, h+/- (<0.35)

PHENIX transverse running in 2005

PHENIX transverse running at 2002

PRL 95, 202001 (2005)

Analysis with high statistics 2006+2008 data in progress Smaller statistical uncertainties (more than factor of 7 improvement)Higher pT data points possible

constrain gluon sivers effect
Constrain gluon Sivers effect

p0 AN from PHENIX 2002 data

Anselmino et al, Phys. Rev. D 74, 094011

Upper bound for gluon Sivers function that is consistent with PHENIX results, assuming vanishing sea contribution

forward p 0 a n
Forward p0 AN

Forward asymmetries contain mixture of

  • Sivers
  • Transversity x Collins

PHENIX 0 results available for s=62GeV

Analysis of large 2008 s=200 GeV dataset – AN of 0 and – 5.2 pb-1, 46% Polarization

– work in progress

Process contribution to 0, =3.3, s=200 GeV

PLB 603,173 (2004)

ssa from di hadron production
SSA from di-hadron production
  • SSA from Interference Fragmentation Function (IFF)
  • Measure di-hadron asymmetry with hadron pairs in central arm (0,h+) (0,h-), (h+,h-)
  • Transversity extraction will become possible with Interference Fragmentation Function measurement in progress at BELLE
  • Two different theoretical models gave different prediction of mass dependence
  • Sign change is not observed in HERMES/COMPASS results

Jaffe, Jin and Tang, PRL 80 (1998) 1166

Bacchetta and Radici, Phys. Rev. D 74, 114007 (2006)

iff definition of v ectors and a ngles
IFF: Definition of Vectors and Angles

Bacchetta and Radici, PRD70, 094032 (2004)


SSA from di-hadron production

No significant asymmetries seen at mid-rapidity.

Added statistics from 2008 running


SSA from di-hadron production

No significant asymmetries seen at mid-rapidity.

Added statistics from 2008 running

  • PHENIX has measured ALL of numerous final state particles which can constrain G
  • While neutral pions have been used by DSSV, other measurements, while statistically limited individually, will make the result more robust.
  • Future G constraint will also include particle correlation. PHENIX is well prepared to measure photon-hadron correlations, and with the VTX, can look at photon jet.
  • PHENIX is on schedule for the W physics program, and are studying results from the recent engineering 500 GeV run.
  • PHENIX has a number of transverse spin measurements, from the recent long transverse runs, and will have more to come.
measuring a ll
Measuring ALL
  • Helicity Dependent Particle Yields
    • p0, p+, p-, g, h, etc
  • (Local) Polarimetry
  • Relative Luminosity (R=L++/L+-)
  • ALL

+ - = Opposite helicity =




++ = Same helicity

fragmentation functions
Fragmentation Functions
  • Cross sections in e+e- for 0, +, -, +, -, 
  • 60 fb-1 data below b resonances
  • 600 fb-1 data at b resonances
    • Can be used for high z data if statistics are an issue
    • Not an issue for above particles
  • Data will be systematically limited