Prompt identiﬁed particle
spectra at RHIC-STAR
Sanshiro Mizuno for the STAR collaboration
University of Tsukuba
smizuno@rcf.rhic.bnl.gov

Motivation•Inclusive proton includes ~40% of protons from weak
decay in Au+Au 200GeV.

•PRL 92, 112301 (2004)
PRC 69, 034909 (2004)

STAR - inclusive proton spectra
not corrected for weak decay feed down contribution
PHENIX - prompt proton spectra
proton coming from Λ is estimated based onmodel simulations•

This result will be ﬁrst direct measurement of prompt
proton pT spectra with new HFT detector at RHIC.
- Uncertainty will decrease signiﬁcantly due tosmaller simulation correction.
Sanshiro Mizuno, CiRfSE workshop

1STAR detector
VPD

Vertex Position Detector
Minimum bias trigger

TOF

Time Projection Chamber
Centrality deﬁnition
Particle trajectory
MomentumPID (dE/dx)
Time Of Flight

TPC

PID (ﬂight time : 1/β)

HFT

Heavy Flavor Tracker

Sanshiro Mizuno, CiRfSE workshop

2

Heavy Flavor Tracker detector
PIXEL detector
Acceptance-1 < η < 10 < φ < 2π
Good resolution of DCA(Distance of Closest Approach)Particle track - collision pointSilicon Strip Detector : r~22cm
Intermediate Silicon Tracker : r~14cm
PIXEL : r~2.8, 8cm

Sanshiro Mizuno, CiRfSE workshop

3HFT performance
80000 DCAXY distribution
0.2<p <0.3GeV/c
T
60000
Width=115µm
40000

Au+Au 200GeV
0-10%

80000

DCAZ distribution
60000 0.2<pT<0.3GeV/c
Width=123µm
40000

DCA distribution fromdata in AuAu 200GeV

20000

20000
0− 0.05

00.05
DCAXY(cm)0− 0.05

00.05
DCAZ(cm)

inclusive charged
particles

3× 10100 DCAXY distribution
1.0<p <1.1GeV/cT
Width=27.9µm50DCA distribution
Gaussian fit

0-10% centrality

DCA distribution
80000 1.0<pZ <1.1GeV/cT
60000 Width=31.1µm
40000
20000

0− 0.0500.05
DCAXY(cm)0− 0.0500.05
DCAZ(cm)

DCA in XY plane and Z direction

DCA Resolution

Run14 Au+Au @200GeV

Width : <50μm at pT=1GeV/c

Sanshiro Mizuno, CiRfSE workshop

4Particle Identiﬁcation
Track selection
At least one hit for each HFT layer
DCA selection is determined with resolution.
dE/dx in TPC and β in TOF

6102000

Au+Au 200GeV, 0-10% DCAXY<99.2µm0.5<p <0.6 (GeV/c)

DCAZ<109.6µm

T105CountCountdE/dx in TPC|y|<0.1

Combined fitpionkaonproton

410310Au+Au 200GeV, 0-10%
1.6<p <1.7 (GeV/c)
T

1500|y|<0.1

DCAXY<40.4µm|nσK|<2

DCAZ<45.8µm

100010250010
1−505nσK−0.05

Sanshiro Mizuno, CiRfSE workshop

00.05

0.1
1/β-1/ β(k)5Detector ineﬃciency & acceptance
Extracted from HIJING and GEANT simulation
The combination of TPC and HFT eﬃciency and acceptance

NRC prompt particle"e↵.⇥acc. =NMC prompt particle

0.4

π+Au+Au 200GeV
0-10%

0.2

0012

3
4p (GeV/c)
T

0.6

0.4

K

ε eff.×acc. = NRC-prompt / NMC-prompt

0.6

ε eff.×acc. = NRC-prompt / NMC-prompt

ε eff.×acc. = NRC-prompt / NMC-prompt

NMC-prompt particle : The number of created prompt particles
NRC-prompt particle : The number of reconstructed real prompt particles+threshold :ε eff.×acc.(p =3)/2
T

0.2

001234p (GeV/c)

0.6

protonthreshold<ε eff.×acc.

0.4

0.200T

F = A exp
Sanshiro Mizuno, CiRfSE workshop

ε eff.×acc.<threshold

1( ✓2apT

34◆b ) pT(GeV/c)

6

The purity of prompt particles
Extracted from HIJING and GEANT simulation.

NRC prompt particle"purity =NRC all particle

1proton

0.95

Au+Au 200GeV
0-10%

0.9
0.85

threshold : ε eff.×acc.(p =3)/2T

weak decay + knockout background<1% at p >1GeV/c

0.8
0T

0.5

11.5
2p (GeV/c)

εpurity = NRC-prompt / NRC-all

εpurity = NRC-prompt / NRC-all

NRC-all particle : The number of reconstructed all of particles
NRC-prompt particle : The number of reconstructed real prompt particles
1
anti-proton

0.95

threshold<ε eff.×acc.
ε eff.×acc.<threshold

0.9

threshold<ε eff.×acc.
ε eff.×acc.<thresholdweak decay contribution

0.85<1% at p >1GeV/c

0.80T

0.5

T

F = A exp
Sanshiro Mizuno, CiRfSE workshop

1( ✓apT1.52◆b ) p (GeV/c)
T7

pT spectra correction
21d N
1
1 "purity=2⇡pT dpT dy2⇡pT Nevt "e↵.⇥acc.

NpT y

Systematic uncertainty
TPC eﬃciency : ~5%
HFT matching eﬃciency : <13%
The diﬀerence of HFT matching eﬃciency
between data and simulation
DCA selection : <10%
Particle species dependent

Sanshiro Mizuno, CiRfSE workshop

8STAR preliminary

10
1
10−1

10−20TT

10T

Au+Au 200GeV, 0-10%

21/(2πp )d2N/(dp dy)T

1/(2πp )d2N/(dp dy)

π, K, p pT spectra

positive
π++Kproton
1102
101
10−1

10−223p (GeV/c)

negativeπK
anti-proton

012T

3p (GeV/c)
T

PID spectra with the HFT in Au-Au 200GeV
The shape depends on particle mass.

Sanshiro Mizuno, CiRfSE workshop

910 − 1STAR preliminary
Fit to STAR preliminary

10 − 2T

1
10 − 1STAR (2006)

12

3p (GeV/c)

10110 − 112

3p (GeV/c)

10 0

K

Data/Fit

2+2

1.5

1.5

11

1

0.5

0.5

0.5

12

3p (GeV/c)

01T

2

3p (GeV/c){exp ( apT

3p (GeV/c)

0proton

12T

Modify Hagedorn equation

F =2T

1.501T

Data/Fit

Data/Fit

π+Inclusive proton
Inclusive proton
Prompt proton

10 2−310 0T2proton

310 − 2−310 010T

1010 − 2−3+10 2

T1K

31/(2πp )d2N/(dp dy)

STAR (2004)
PHENIX (2004)

1010T

π+ Au+Au 200GeV, 0-10%

310 2

T1/(2πp )d2N/(dp dy)

10T

1/(2πp )d2N/(dp dy)

π, K, p pT spectra

An2bpT ) + pT /p0 }3p (GeV/c)
TPRL 92, 112301 (2004)
PRC 69, 034909 (2004)
PRL 97, 152301 (2006)

STAR results (orange, cyan) : inclusive proton
PHENIX results (magenta) : corrected for weak decay from Λ
Sanshiro Mizuno, CiRfSE workshop1010 − 1

STAR preliminary
Fit to STAR preliminary

10 − 2110 − 1

STAR (2006)

23p (GeV/c)1
10 − 112

3p (GeV/c)

10 0

K

Data/Fit

2-2

1.5

1.5

11

1

0.5

0.5

0.5

1

2

3p (GeV/c)

01

T

2

3p (GeV/c){exp ( apT

3p (GeV/c)

0anti-proton

12T

Modify Hagedorn equation

F =2T

1.501

T

Data/Fit

Data/Fitπ-10−310 0T2

Inclusive proton
Inclusive proton
Prompt proton

10 − 2−31anti-proton

310 2T

1010 − 2−310 010T-10 2T

1K

31/(2πp )d2N/(dp dy)

STAR (2004)
PHENIX (2004)

1010T

π- Au+Au 200GeV, 0-10%

310 2

T1/(2πp )d2N/(dp dy)

10T

1/(2πp )d2N/(dp dy)

π, K, p pT spectra

An2bpT ) + pT /p0 }3p (GeV/c)T

PRL 92, 112301 (2004)
PRC 69, 034909 (2004)
PRL 97, 152301 (2006)

STAR results (orange, cyan) : inclusive proton
PHENIX results (magenta) : corrected for weak decay from Λ
Sanshiro Mizuno, CiRfSE workshop

1110.8

STAR preliminary

0.6
0.4
0123pT (GeV/c)-1.2Ratio

1.2π-/ π+Au+Au 200GeV, 0-10%

Ratio

Ratio

Anti-particle to particle ratio
+K /K

1.2

110.8

0.8

0.6

0.6

0.4
012

3pT (GeV/c)

0.4
0p/p

12

3pT (GeV/c)

The ratios are about 1, 0.95, 0.8 for π, K, p at RHIC
energy.

Sanshiro Mizuno, CiRfSE workshop1210.8
0.6
0.4
0STAR preliminary
STAR (2004)
PHENIX (2004)
STAR (2006)
123pT (GeV/c)-1.2Ratio

1.2π-/ π+Au+Au 200GeV, 0-10%Ratio

Ratio

Anti-particle to particle ratio
+K /K

1.2

1

1

0.8

0.8

0.6

0.6

0.4
012

3pT (GeV/c)

0.4
0p/p

Inclusive proton
Inclusive proton
Prompt proton
123pT (GeV/c)

PRL 92, 112301 (2004)
PRC 69, 034909 (2004)
PRL 97, 152301 (2006)

There is no signiﬁcant diﬀerence between inclusive
and prompt proton ratio.

Sanshiro Mizuno, CiRfSE workshop

13

protonTd2N/(dm dy)

Estimating dN/dy distribution
20

Au+Au 200GeV
0-10%|y|<0.1
F = A mT exp -Out of range of measured spectramT -m0T

Extrapolating with equations

10The diﬀerence of equations aredeﬁned as systematic uncertainty.
0
00.5

11.5
22mT - m0(GeV/c )Fraction of dN/dymeasured dN/dy

extrapolated dN/dy extrapolated dN/dy
low pThigh pT

π+K+

168.7 (53.5%)

146.7 (46.4%)

0.14 (0.1%)

26.8 (50%)

26.7 (49%)

0.1 (1%)

proton11.1 (51%)

10.4(48%)0.11 (1%)

For pion, Bose-Einstein equation, mT exponential (for estimating systematics)
For kaon and proton, pT exponential, mT exponential
Sanshiro Mizuno, CiRfSE workshop

14π+200

STAR preliminary
STAR (2004)
PHENIX (2004)

20100200300

Npart

Au+Au 200GeV|y|<0.1

1000dN/dydN/dy

Inclusive proton
Prompt proton

40π-60100K200300

Npart-40200

40100200300

Npartanti-proton

20201000030

10000proton

2000200

60

4030

100300+dN/dy300

KdN/dy

dN/dy

dN/dy

dN/dy distribution

300

Npart0010100200300

Npart00100200300

NpartSTAR results (orange, cyan) : inclusive proton
PHENIX results (magenta) : corrected for weak decay from Λ

Sanshiro Mizuno, CiRfSE workshop

PRL 92, 112301 (2004)
PRC 69, 034909 (2004)15

Summary•

The ﬁrst result of prompt π, K, p pT spectra with
the HFT in Au+Au 200GeV collisions at STAR
experiment•The anti-particle to particle ratio
There is no signiﬁcant diﬀerence between
inclusive and prompt proton results.

•Prompt particle azimuthal anisotropy
Important for kinetic freeze-out parameters

Sanshiro Mizuno, CiRfSE workshop

16

Sanshiro Mizuno, CiRfSE workshop

30

π+Au+Au 200GeV
0-10%

4030

K

1/ε eff.×acc.

40

1/ε eff.×acc.

1/ε eff.×acc.

Eﬃciency correction+threshold :ε eff.×acc.(p =3)/240

proton30Tthreshold<ε eff.×acc.

20201010001234p (GeV/c)00

ε eff.×acc.<threshold

20
1012T

34p (GeV/c)
T001234p (GeV/c)
T

NRC prompt particle"e↵.⇥acc. =NMC prompt particle

Correction of detector eﬃciency and acceptanceCorrection factor get large in low pT region

Sanshiro Mizuno, CiRfSE workshop