Kieran Boyle 1

Kieran Boyle

(RIKEN BNL Research Center)

Current Results and Future

Prospects from

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Topics• Longitudinal Spin

– Current results– Future plans/ideas

• W physics– Plans– A first look at Run9 data

• Transverse Spin– Current Results– Future plans

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RHIC and PHENIX

A few standard slides

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RHIC

BRAHMS & PP2PP (p)

STAR (p)PHENIX (p)

AGS

LINAC BOOSTER

Pol. Proton Source

Spin RotatorsPartial Siberian Snake

Siberian Snakes

200 MeV PolarimeterAGS Internal Polarimeter

Rf Dipoles

RHIC CNI (pC) PolarimetersAbsolute Polarimeter (H jet)

++ +−+−+−−−+ +−− +−

Year s [GeV] L [pb-1] P [%] FoM (P4L)

2003 200 0.35 27 0.0019

2004 200 0.12 40 0.0031

2005 200 3.4 49 0.20

2006 200 7.5 57 0.79

2006 62.4 0.08 48 0.0042

2009 500 ~10 ~35 ~0.150

2009 200

Longitudinal

Year s [GeV] L [pb-1] P [%] FoM (P2L)

2002 200 0.15 15 0.0034

2005 200 0.16 47 0.035

2006 200 2.7 51 0.7

2006 62.4 0.02 48 0.0046

2008 200 5.2 46 1.1

Transverse

In progress

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PHENIX Detector

BBC

ZDCZDC

EMCaldetection• Electromagnetic Calorimeter (PbSc/PbGl):

• High pT photon trigger to collect trigger to collect 0's, ’s, ’s

• Acceptance: ||x • High granularity (~10*10mrad2)

• 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 determinationW± from ±

• Muon Identification (MuID)• Tracking (MuTR)• Triggering (RPC and MuTrig Upgrades)Relative Luminosity and Local polarimetry• Beam Beam Counter (BBC)

• Acceptance: 3.0< 3.9• Zero Degree Calorimeter (ZDC)

• Acceptance: ±2 mrad

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Constraining G

Current Longitudinal Spin Program

G2 Gq q2

Hard Scattering Process

2P22xP

1P

11xP

0

with ~25%, G not as well constrained, L?

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Why ALL?

• If f = q, then we have this from pDIS• So roughly, we have

+- =

+++

+=

From ep (&pp)(HERA mostly)

pQCD NLOFrom e+e-(& SIDIS,pp)

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pQCD worksarXiv:0704.3599 [hep-ex]

0 @ 200 GeV Direct @ 200 GeV

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ALL Results

Large number of independent probesAccepted in PRL: arXiv:0810.0694

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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.

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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

arXiv:0810.0694

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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.

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Systematic Uncertainty Impact• 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

Accepted in PRL: arXiv:0810.0694

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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].

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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

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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

R. Bennett’sThesis

~80%

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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.

R. Bennett’sThesis

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Future for PHENIX G

Lower x, correlations and Higher Luminosity

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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.

present (0)x-ranges = 200 GeV

Extend to lower x at s = 500 GeV

Extend to higher x at s = 62.4 GeV

• 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.

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Expectation for 0 ALL

Full spin program

• Limited at high pT due to merging of photons as opening angle decreases

• Relative luminosity systematic uncertainty must be reduced.

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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.

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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

~50m• c/b separation

by c

|jet| < 1.2jet

PHENIX Direct || < 0.35

Jet

Life time (c) D0 : 125 m B0 : 464 m

DCA

ppD

B

e

e

Simulation

Gamma Jet• Large

acceptance:||<1, ~2 for

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W-bosons at PHENIX

Accessing the flavor dependent quark sea spin distributions

l+

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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

μ μ ±

ee+/-+/-

W

Muon pT spectra in the Muon Arms(2000 [1/pb], from PYTHIA5.7)

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W

• 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-

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W

MuID- only existing trigger- no momentum selectivity..

<Muon Trigger Upgrade><Muon Trigger Upgrade>• MuTr FEE Upgrade (MuTRG)• Install RPC (Resistive Plate Chamber)• Install additional Pb absorber

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Rapidity: 1.2 < <2.2 (2.4)

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We 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)

e+

e-

pi+pi+

pions: NLO pQCD calculation from W. VogelsangW: RHICBOS (Nadolsky, Yuan)

<Charged hadron rejection>EMCal intrinsic: 50-150Shower profile: 2-4 Isolation cut: ~10Total: 1000-6000

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We Run 9 • Polarization ~35%• Luminosity ~10%

Measure cross section• alpha [rad.] ~ 0.1/

mom [GeV/c]• “energy / mom < 3” cut

appliedeta

pi0

negative charge

positive charge

Energy v.s. Inclination of the track

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

Only analyzed part of data set

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Event Display of High energy events

3. W detection @ PHENIX 29

Found W candidates.

Analysis is under way!

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Transverse Spin results

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AN from 0, h+/- (<0.35)

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

PHENIX transverse running at 2002

PHENIX transverse running in 2005

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Constrain gluon Sivers effect0 AN from PHENIX 2002 data

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

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

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Forward 0 AN

Forward asymmetries contain mixture of• Sivers• Transversity x CollinsPHENIX 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

PLB 603,173 (2004)

Process contribution to 0, =3.3, s=200 GeV

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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

Jaffe, Jin and Tang, PRL 80 (1998) 1166Bacchetta and Radici, Phys. Rev. D 74, 114007 (2006)

• Two different theoretical models gave different prediction of mass dependence

• Sign change is not observed in HERMES/COMPASS results

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IFF: Definition of Vectors and Angles

1 2

1 2

1 2

, : momenta of protons

, : momenta of hadrons

( ) / 2

: proton spin orientation

A B

h h

C h h

C h h

B

P P

P P

P P P

R P P

S

= +

= −

ur ur

ur ur

ur ur ur

ur ur ur

ur

1hPur

2hPur

APur

BPur

CPur

BSur

pp hhX↑ →

1 2hadron plane: ,

scattering plane: ,

h h

C B

P P

P P

ur ur

ur ur : from scattering plane

to hadron planeRφ : from polarization vector

to scattering plane Sφ

Bacchetta and Radici, PRD70, 094032 (2004)

2 CRur

sin sin( )R SA A φ φ φ= −

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Added statistics from 2008 running No significant asymmetries seen at mid-rapidity.

SSA from di-hadron production

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Added statistics from 2008 running No significant asymmetries seen at mid-rapidity.

SSA from di-hadron production

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Summary• 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.

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Backups

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Measuring ALL

Helicity Dependent Particle Yields , , , , , etc

(Local) Polarimetry Relative Luminosity (R=L++/L+-) ALL

+ - = Opposite helicity =

++ = Same helicity

+

+=

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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

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Estimating Average x gluonR. Bennett’sThesis