99/11/12 PHENIX November Core 1

ΔGΔG 　　 Measurement with the Measurement with the Heavy Quark ProductionHeavy Quark Production

• ΔG Status and probes for it

• Prediction of ALL in the PHENIX

• ALL uncertainties and ΔG sensitivity– J/– e pair

– single electron

• Reduction of electron background

• Summary

Hiroki Sato Kyoto Univ./RIKENPHENIX November Core

99/11/12 PHENIX November Core 2

Status of Status of ΔGΔG MeasurementMeasurement

1/2 = (1/2)+G+L+LG

～ 0.3

ΔG

Polarized Deep Inelastic Scattering

Direct measurement with polarized p-p collisions（ RHIC）

-1

0

1

2

3

4

Large uncertainty for indirect measurement

quark spin gluon spin

orbital angular moment

proton spin

Altarelli. et.al (1997)Q2=

E155(1999)Q2=5GeV2

SMC(1997)Q2=10GeV2

99/11/12 PHENIX November Core 3

Probes for Probes for ΔG ΔG MeasurementMeasurement

　

Gluon Compton

Charmonium Production

Open Heavy QuarkProduction

High-pT prompt

e+e-, +-

e+e-, +- ,ehigh-pT single e,eD, D

G(x)ALL

simulation

?Experiment

99/11/12 PHENIX November Core 4

SimulationsSimulations

• Purposes

– ALL expectation with PHENIX using some models of G(GS-A,B,and C)

– Yield and background study → estimation of statistical and systematic errors.

• PYTHIA 5.7 with GRV94-LO and JETSET 7.3 for event generation.

s=200GeV

• Simple acceptance cut (||<0.35 for Central Arms and 1.1<||<2.3 for Muon Arms)

• normalization to 32 or 320pb-1

99/11/12 PHENIX November Core 5

AALLLL Prediction at PHENIX Prediction at PHENIX

1.12

ˆ

M

s

1.5

2

5

a

AQQgg

LL

XQQpp

LL

xG

xG

xG

xG

xx

)(

)(

)(

)(

),(

2

2

1

1

21

cos*

ΔG

（ｘ

）

M.Karliner and R.W.Robinett(1993)T.Gehmann and W.J.Stirling(1995)

aLL

x

Me(GeV)

1.711.631.02

AL

L

ALLpp→bb Ｘ

μeGS-A

GS-B

GS-C

GRV-94 LOfor unpol.PDF

99/11/12 PHENIX November Core 6

AALLLL Experimental Errors Experimental Errors

　　 PB1,2　 Beam Polarization 　～　 0.7(RHIC)　　 N++（ N+ －） Number of events 　

　　 L++（ L+ －） Luminosity

• Statistical Error

• Systematic Errors PB １ ,2 　→ ALL/ALL ~20%

(L+ － /L++) → ALL~10 ｰ 4

– Nbg/Nsig ,ALLbg

LNLN

LNLN

PPA

BBLL

21

1exp

)(1

.)(21

NNNNPP

statA tot

totBB

LL

) (if sigbgbg

LLsig

bgLL NNA

N

NA

+‐: Beam Helicity

99/11/12 PHENIX November Core 7

DimuonsDimuons

M (GeV/c2)NJ/(pT>2GeV)~120k events

→ALLJ/ (stat.)~ 0.006

N/K /NJ/~ 0.15

ALL/K ~0.007

→ ALL J/ (syst.)~0.001

ALLJ/

G

production mechanism of the charmonium

　

Yie

ld p

er B

in(0

.2G

eV/c

2 )

pT()>2GeV/c

bottom

J/ （ color singlet model ）

/K

320pb-1 s=200GeV

99/11/12 PHENIX November Core 8

ee pairs pairs

• background of electrons (0Dalitz decay and conversion) can be reduced

• b/c separation is under studying → important because ALL is different

Meμ

Nbb→eμ~120k events→ ALL(stat.)~ 0.006Ncc→eμ ~100k events ALL(syst.)~0.006N/K→eμ ~60k events

320pb-1

Sensitive enough to distinguish GS-A,B and C

pTe,pT

>1GeV/c

_bb→e

/K→e_cc→e

total

Me (GeV/c2)

Yie

ld p

er 1

GeV

/c2

Me (GeV/c2)

s=200GeV

99/11/12 PHENIX November Core 9

e pairspairs x region

protonx1P

CentralArm

Muon Arm

x2P

ｂ→ e

ｂ→

X2

P(GeV/c)

Correlation is small becauseof decay kinematics

bbe (pTe,pT

>1GeV/c)

X1 X2

99/11/12 PHENIX November Core 10

ee pairs sensitivity pairs sensitivity

Background reduction

• Smaller systematic error

• Larger statistics with low pT events

Meμ

bbe (pTe,pT

>1GeV/c)

ALL Stat. Error0.0310.014

0.0120.014

0.017GS-A

GS-C

GS-B

Systematic error is comparable to statistical error

320pb-1 s=200GeV

99/11/12 PHENIX November Core 11

00 Dalitz reduction with the Dalitz reduction with the isolation cut with MVD isolation cut with MVD

• Another charged particle (pT>10MeV) in the cone of an electron → regard it as a 0

85% reduction can be achieved by the 10 degree cone cut for pT

e>1GeV/c

Assuming MVD efficiency is 90%

0->eX

pTe>1GeV/c

cc->eX

e+ or e-

Detector simulation is needed for more realistic study

99/11/12 PHENIX November Core 12

conversion reductionconversion reduction

• Comparable to Dalitz decay contribution

• Origin– beam pipe (26%) - can be reduced by the

isolation cut with MVD

– MVD (53%) • inner barrel - reject 2-MIP events

• outer barrel - require hits in the inner shell

– MVD shell (21%) - require hits in MVD

Akiba 19972229

1214

601

487

Akiba, 1997

cm

99/11/12 PHENIX November Core 13

SingleSingle 　　 ElectronsElectrons

With 32pb-1 luminosity (10% of full) and pTe>1GeV/c,

• Charm 3.1M, min.bias 12M →1.8M(0 reduction) events

ALL(stat.)~0.001, ALL(syst.)~0.001 (ALL(GS-A)~ -0.04) →excell

ent measurement!

Akiba,1996

charm

0 Dalitz

pT in GeV/c

Arb

itra

ry u

nit

99/11/12 PHENIX November Core 14

Other probesOther probes

• Di-electrons

– Small Dalitz decay background

– ~100k J/’s (pTe>0.4GeV/c) at 320pb-1 with the

color-singlet model

– open c/b is possible?

• eD (D) pairs

– identified with eK coincidence (peak in K invariant mass)

– 31k events with 320pb-1 (pTe>0.4GeV/c)

– strong charm ID → confirmation of open charm yield

• Single muons

– large statistics, but it’s crucial to reject decay hadrons before the nosecone.

99/11/12 PHENIX November Core 15

Summary and Summary and ConclusionConclusion

• We can get many inputs on the gluon polarization from the asymmetry for heavy quarks using their (semi)leptonic decay channels.

• Future Work

– Separation of bottom/charm → important for e pairs (pT

e, >1GeV/c).

– Full simulation is needed for more realistic estimation of the Dalitz/conversion background reduction.

– Electron trigger is needed → Ken Barish (UCR) and Matthias G.-Perdekamp(RBRC) work on this from spin side

ALL(stat.) ALL(syst.) ALL(GS-A)

J /→ ( pT

>2GeV) 0.006 0.001 0.01*

bb→ eX(pT

e,>1GeV) 0.006 0.006 0.06

cc→ eX(pT

e>1GeV) 0.001 0.001 -0.04

*with color octet model

99/11/12 PHENIX November Core 16

...Backup slides......Backup slides...

99/11/12 PHENIX November Core 17

Muon Arm PerformanceMuon Arm Performance

• 1.1<||<2.4, absorber~10λint (pz cut~2GeV/c)

• Detector acceptance~0.7

• Muon Tracking Chambers in Muon Magnet

– 3 stations x~100m →Δp/p~3% (@3~10GeV/c)

• Muon Identifier

– hadron rejection with 5 layers of Iarocci tubes and Steel

Iarocci tube

99/11/12 PHENIX November Core 18

MuID Performance MuID Performance Test@KEKTest@KEK

• Hadron rejection

= Central Magnet MuID

For 5GeV/c pions,

0.0050.04(South)= 210-4

< 210-3 (Decay before

Central Magnet)

Fraction of remaining

99/11/12 PHENIX November Core 19

PHENIX Muon PHENIX Muon SimulationSimulation

• Purpose

– Estimation of signal and background

– Evaluation of the detector response and 　 reconstruction　 performance

• Procedure

•Event generation(PYTHIA)

s = 200GeV

•Detector simulation

Full GEANT

pp

•Reconstruction

•Normalized to RHIC Luminosity 32pb-1(year2000) 320pb-1（ year2001）

99/11/12 PHENIX November Core 20

Single Single

• Contribution of decay and b-quark is comparable for pT>6 GeV/c.

• Uncertainty of the cross section of heavy quarks → measurement may be possible.

b→

320pb-1

c→

→

pTmin 2GeV/c 4GeV/c 6GeV/c

charmALL

4106

10-36104

0.012103

0.05bottomALL

4106

10-32105

410-32104

0.015

99/11/12 PHENIX November Core 21

DielectronsDielectronsAkiba 1996

99/11/12 PHENIX November Core 22

Open Heavy Quark Open Heavy Quark ProductionProduction

• PYTHIA(GRV-94LO) agrees with experimental data at lower energies (s < 50GeV)

• Large theoretical uncertainties (30b<(cc)<3mb and 0.7b<(bb)<5b at s=200GeV)

s=200GeV

。E789

PYTHIA charm

PYTHIA bottom

200b

0.7b

99/11/12 PHENIX November Core 23

Open heavy cross Open heavy cross section II( higher section II( higher

s)s)• For b-quark production, PYTHIA agrees w

ith D0 data within factor 2 ( at s=1.8TeV) (pp→bbX),s=630GeV

UA1 10.23.3b

PYTHIA(GRV94-LO) 7.3b

99/11/12 PHENIX November Core 24

Charged Hadron Charged Hadron ProductionProduction

• PYTHIA(GRV94-LO) and UA1 data are consistent within factor two.

Invariant cross section of charged hadrons in pp collisions at s=200GeV

99/11/12 PHENIX November Core 25

PYTHIA PYTHIA // ratio ratio

• ~104 at pT=2GeV/c

hadrons

c→

b→