Δg measurement with the heavy quark production
DESCRIPTION
ΔG Measurement with the Heavy Quark Production. Hiroki Sato Kyoto Univ./RIKEN PHENIX November Core. ΔG Status and probes for it Prediction of A LL in the PHENIX A LL uncertainties and ΔG sensitivity J/ e pair single electron Reduction of electron background Summary. - PowerPoint PPT PresentationTRANSCRIPT
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→