1 RSC2006—Sept. 30, 2006 Kieran Boyle Recent Results from PHENIX Longitudinal Spin Program Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration Outline:

1RSC2006—Sept. 30, 2006Kieran Boyle

Recent Results from PHENIX Longitudinal Spin Program

Kieran Boyle (Stony Brook U.)for

the PHENIX Collaboration

Outline:• Quick Physics overview

• RHIC and PHENIX, and ALL requirements

• Run5 and Run6 new Results


Motivation

g2 gq q2

Hard Scattering Process

2P2 2x P

1P

1 1x P

with ~20%, g, L not well constrained

How to measure g:

0

0

LLA ~ agg * g2 + bgq * g + cqq


ALL Requirements

Helicity Dependent Particle Yields (Local) Polarimetry Relative Luminosity (R=L++/L+-)

ALL

++ same helicity+ opposite helicity


RHIC

BRAHMS & PP2PP (p)

STAR (p)PHENIX (p)

AGS

LINAC BOOSTER

Pol. Proton Source

Spin RotatorsPartial Siberian Snake

Siberian Snakes

200 MeV Polarimeter AGS Internal PolarimeterRf Dipoles

RHIC CNI (pC) PolarimetersAbsolute Polarimeter (H jet)

Year [GeV] Luminosity [pb-1] (recorded) Polarization [%] Figure of Merit (P4L)

2005 * 200 3.4 46 0.15

2006 * 200 7.5 62 1.11

2006 * 62.4 0.1** 48 0.0053**

* Longitudinal ** Not yet finalized


PHENIX Detectordetection• Electromagnetic Calorimeter (PbSc/PbGl):

• High pT photon trigger to collect 0's, ’s, ’s • Acceptance: x • High granularity (~10*10mrad2)

• Drift Chamber (DC)/Ring Imaging Cherenkov Counter (RICH)

• High pT charged pions (pT>4.7 GeV).J• Muon Id/Muon Tracker

• Multiple muon triggers.Relative Luminosity• Beam Beam Counter (BBC)

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

• Acceptance: ±2 mradLocal Polarimetry• ZDCLvL2 data filter• Filters “rare” events for fast analysis

• Dimuon for J/Y• pT>2.5 GeV photon for 0

BBC

ZDCZDC


Local Polarimetry at PHENIX• Use Zero Degree Calorimeter

(ZDC) to measure a L-R and U-D asymmetry in forward neutrons (Acceptance: ±2 mrad).

• When transversely polarized, we see clear asymmetry.

• When longitudinally polarized, there should be no asymmetry.

BLUE YELLOW

Raw

as

ymm

etry

Raw

as

ymm

etry

Idea: Use neutron asymmetry to study transversely polarized component.

BLUE YELLOW

Raw

as

ymm

etry

Raw

as

ymm

etry


Measured Asymmetry During Longitudinal Running

(2005)

<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(%

)

2/NDF = 88.1/97p0 = -0.00323±0.00059

2/NDF = 82.5/97p0 = -0.00423±0.00057

LR

LR

UD

UD

XF>0 XF>0

XF<0 XF<0

2/NDF = 119.3/97p0 = -0.00056±0.00063

2/NDF = 81.7/97p0 = -0.00026±0.00056

Fill NumberFill Number


ATT

• Here

• ATT

– azimuthally independent double transverse spin asymmetry.

– ALL background.– expected to be small,

but previously unmeasured.

• In Run5, PHENIX took a short transverse run specifically to measure ATT.

• Consistent with zero.


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

where

• Limited by ZDC statistics.Year [GeV] R ALL

2005 * 200 1.0e-4 2.3e-4

2006 * 200 1.1e-4 1.5e-4

2006 * 62.4 1.3e-3 2.8e-3* Longitudinal


ALL

• From Run5 and Run6, we are currently studying an array of probes:–

– Direct photon– – multiparticle “cone”– J/

g2 gq q2


2P2 2x P

1P

1 1x P

probe


Calculating 0 ALL

1. Calculate ALL(+BG) and ALL(BG) separately.

2. Get background ratio (wBG) from fit of all data.

3. Subtract ALL(BG) from ALL(+BG):

ALL(+BG) = w· ALL() + wBG · ALL(BG)

This method is also used for other probes with two particle decay mode:

• , J/


0 in Run6

• In Run6, there were two separate longitudinal running periods:– April 27-June 5 @ s=200 GeV– June 12-June 20 @ s=62.4 GeV

s=62.4 GeV– Due to the small size of the s=62 GeV data set, we

were able to finish production and measure 0 ALL. s=200 GeV

– As was mentioned earlier, PHENIX filters data for rare signals.

– In Run6, we have also used this filtered data (here, for high pT photons) to produce a high pT 0 ALL @ s=200 GeV with much improved uncertainties compared to Run5.


62 GeV

• Initial, 62 GeV p+p was needed for heavy ion comparison.

• Thanks to CAD, we were able to get longitudinally polarized beam at PHENIX.


But why?

• By definition:

• Measuring 0 ALL at s=62.4 GeV allows us to test a higher xT range with lower statistics than currently possible at s=200 GeV.

• As stated earlier, uncertainty in ALL @ 62 GeV due to relative luminosity is 2.8x10-3, which is less than our statistical uncertanty.


62 GeV: Local Polarimetry

• Forward Neutron asymmetry reduced at 62 GeV, but still measurable.

xpos

xpos

xpos

xpos

Red : transverse dataBlue : longitudinal data

Blue Forward Blue Backward

Yellow BackwardYellow Forward

<PLR/AN>

BLUE 0.065 ± 0.143

YELLOW 0.132 ± 0.100

<PUD/AN>

BLUE -0.025 ± 0.119

YELLOW -0.020 ± 0.093

PLBLUE 100% – 2.3%

PLYELLOW 100% – 2.2%


62 GeV Results

• ATT still to be measured with short transverse data set taken during rotator commisioning.– Assume remaining transverse component ~21%

– 0.212ATT ~ 0.04ATT contribution to measured ALL

• 0 unpolarized cross section at s=62 GeV is not yet finished. – Unclear how well NLO pQCD describes our data.

– Validity of comparison with expected ALL theory curves calculated from NLO pQCD is NOT clear.

– Result expected soon


0 ALL @ s=62 GeV

• As there is no cross section at s=62 GeV, we do not calculate confidence levels.

• Grey band is systematic uncertainty from relative luminosity, which is independent of pT.

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


Comparison with 200 GeV

• Converting to xT, we can get a better impression of the significance of the s=62 GeV data set, when compared with the Run5 preliminary data set.

• Awaits the unpolarized cross section for estimating 62 GeV significance.


200 GeV

• As shown earlier, the Run6 longitudinal data set had a figure of merit 7.5 times that of Run5.

• Use data filtered for high pT photon.– Due to low efficiency in our filter at medium pT 0’s data for pT<5

GeV is statistically limited.

• We only show data with pT>5 GeV.• Uncertainty from relative luminosity for the sqrt(s)=200

GeV longitudinal running period gives an uncertainty in ALL of 1.5e-4.

• For local polarimetry, we need full production. – Currents for Rotator and Main magnets for both STAR and

PHENIX are monitored during the run– Enough historical evidence exists for understanding spin

direction and magnet current correlation.– Conclude that spin orientation is fine.


Run5 0 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.


Run6 0 ALL (200 GeV)• Run6 Data set from

2.0-2.7 times improvement on statistical uncertainties from Run5.

• Variation due to LvL2 “turn on.”

• Due to unreleased absolute polarizations, which act a scale factor in ALL and which contain correlated and uncorrelated part, we have not combined the two data sets.

• For confidence levels, assume complete correlation.

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


What about g?• Confidence levels from a simple 2 test between

our data and the four curves plotted.• Theoretical uncertainties are not taken into

account.

C.L. (%)

Theory model Run5 Run6 Run5&Run6

GRSV-std 18.0-22.1 0.49-7.02 1.5-8.8

*GRSV-max (g=g) 0.0-0.0 0.0-0.0 0.0-0.0

*GRSV g=0 16.9-18.6 14.2-16.5 11.1-12.2

*GRSV g=−g 0.0-0.9 0.0-1.1 0.0-0.0

• Run 6 rules out maximal gluon scenarios.

• Expect clearer statement when lower pT data from Run6 is available.


What about g?• To remove possibility that soft physics is influencing the

result through the pT<2 data, we calculated confidence levels excluding this point.

• Theoretical uncertainties are not taken into account.

C.L. (%)

Theory model Run5 Run6 Run5&Run6 Run5&Run6 (pT>2 GeV)

GRSV-std 18.0-22.1 0.49-7.02 1.5-8.8 0.9-6.0

*GRSV-max (g=g) 0.0-0.0 0.0-0.0 0.0-0.0 0.0-0.0

*GRSV g=0 16.9-18.6 14.2-16.5 11.1-12.2 8.2-9.0

*GRSV g=−g 0.0-0.9 0.0-1.1 0.0-0.0 0.0-0.0

• No significant difference seen.

• Expect clearer statement when lower pT data from Run6 is available.

• More detailed analysis of g constraint underway.


High pT Charged Pion

g2 gq q2


2P 2 2x P

1P

1 1x P

+, -• First “Proof of concept”

measurement• Charged pions begin firing the

RICH at pT~4.7 GeV, which is used for particle ID.

• Higher pT more sensitive to gluon polarization.

• See A. Moreale’s talk


p+p + X

• Similar analysis technique as with 0, using two photon decay channel.

• Independent measure for gluon polarization.• See F. Ellinghaus’ talk later today.

g2 gq q2


2P 2 2x P

1P

1 1x P


Multiparticle ALL

• Definition of pT cone: sum of pT measured by EMCal and tracker with R = (||2+||2) < 0.3 rad.

• Relationship between pTcone

and pTjet is evaluated with

PYTHIA and GEANT.• See K. Nakano’s talk.


2P 2 2x P

1P

1 1x P

g2 gq q2


J/ (Run5 & Run6)• New Run6 result

from LvL2 filtered data– LvL2 filters data on

defined rare condition

– Here, LvL2 uses dimuon event.

• Shows clear improvement over Run5.

• Second year in which J/ has been measured using LvL2 filtered data.

• See M. Liu’s talk


Direct photon

• First step, direct photon cross section using isolation cut.

• Isolation cut:– ETot<0.1Ecandidate within 0.5

rad.

gq


2P 2 2x P

1P

1 1x P

qq

Gluon-photon compton dominant

hep-ex/

0609031

RUN5


Direct photon

• Background from merged 0 removed by shower shape (calibrated with test beam).

• Background from isolated 0 photon <15% above 10 GeV.

• Asymmetry analysis underway. Results expected soon.

• See T. Horaguchi’s talk.

isolated pi0 photon

signal


Conclusions

• PHENIX is well positioned to constrain g with a new significantly better data set from Run6. Many other complimentary analyses are on the way.

• 62 GeV data give information at higher xT, and may give powerful independent constraint on g.

Documents

1 RSC2006—Sept. 30, 2006 Kieran Boyle Recent Results from PHENIX Longitudinal Spin Program Kieran Boyle (Stony Brook U.) for the PHENIX Collaboration Outline: