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

Prompt identified particle spectra at RHIC-STAR

Sanshiro Mizuno for the STAR collaboration

University of Tsukubasmizuno@rcf.rhic.bnl.gov

Sanshiro Mizuno, CiRfSE workshop

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

• STAR - inclusive proton spectra not corrected for weak decay feed down contributionPHENIX - prompt proton spectra proton coming from Λ is estimated based on model simulations

• This result will be first direct measurement of prompt proton pT spectra with new HFT detector at RHIC. - Uncertainty will decrease significantly due to smaller simulation correction.

1

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

Sanshiro Mizuno, CiRfSE workshop

STAR detector

Vertex Position DetectorMinimum bias trigger Time Projection Chamber Centrality definition Particle trajectoryMomentum PID (dE/dx)Time Of FlightPID (flight time : 1/β) Heavy Flavor Tracker

2

TOF

TPC

VPD

HFT

Sanshiro Mizuno, CiRfSE workshop

Heavy Flavor Tracker detector

Silicon Strip Detector : r~22cm Intermediate Silicon Tracker : r~14cm

PIXEL : r~2.8, 8cm

3

PIXEL detectorAcceptance -1 < η < 1 0 < φ < 2πGood resolution of DCA(Distance of Closest Approach)Particle track - collision point

Sanshiro Mizuno, CiRfSE workshop

(cm)XYDCA0.05− 0 0.050

20000

40000

60000

80000 Au+Au 200GeV0-10%

distributionXYDCA<0.3GeV/c

T0.2<p

mµWidth=115

(cm)ZDCA0.05− 0 0.050

20000

40000

60000

80000 distributionZDCA<0.3GeV/c

T0.2<p

mµWidth=123

(cm)XYDCA0.05− 0 0.050

50

100

310×

DCA distributionGaussian fit

distributionXYDCA<1.1GeV/c

T1.0<p

mµWidth=27.9

(cm)ZDCA0.05− 0 0.050

20000400006000080000

distributionZDCA<1.1GeV/c

T1.0<p

mµWidth=31.1

HFT performance

DCA in XY plane and Z directionWidth : <50μm at pT=1GeV/c

DCA Resolution

4

DCA distribution from data in AuAu 200GeV

0-10% centrality

inclusive charged particles

Run14 Au+Au @200GeV

Sanshiro Mizuno, CiRfSE workshop

(k)β-1/β1/0.05− 0 0.05 0.1

Cou

nt500

1000

1500

2000 Au+Au 200GeV, 0-10%<1.7 (GeV/c)

T1.6<p|y|<0.1

|<2Kσ|nmµ<40.4XYDCA

mµ<45.8ZDCA

Kσn5− 0 5

Cou

nt

1

10

210

310

410

510

610

Combined fitpionkaonproton

Au+Au 200GeV, 0-10%<0.6 (GeV/c)

T0.5<p|y|<0.1

mµ<99.2XYDCAmµ<109.6ZDCA

Particle IdentificationTrack selectionAt least one hit for each HFT layerDCA selection is determined with resolution.

dE/dx in TPC dE/dx in TPC and β in TOF

5

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3 4

MC

-pro

mpt

/ N

RC

-pro

mpt

= N

acc.

×ef

f.ε

0

0.2

0.4

0.6 +πAu+Au 200GeV0-10%

(GeV/c)T

p0 1 2 3 4

MC

-pro

mpt

/ N

RC

-pro

mpt

= N

acc.

×ef

f.ε

0

0.2

0.4

0.6 +Kthreshold :

=3)/2T

(pacc.×eff.ε

(GeV/c)T

p0 1 2 3 4

MC

-pro

mpt

/ N

RC

-pro

mpt

= N

acc.

×ef

f.ε

0

0.2

0.4

0.6

acc.×eff.εthreshold<<thresholdacc.×eff.ε

proton

Detector inefficiency & acceptanceExtracted from HIJING and GEANT simulation The combination of TPC and HFT efficiency and acceptance

NMC-prompt particle : The number of created prompt particles NRC-prompt particle : The number of reconstructed real prompt particles

6

"e↵.⇥acc. =

NRC�prompt particle

NMC�prompt particle

F = A exp

(�✓

a

pT

◆b)

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 0.5 1 1.5 2

RC

-all

/ N

RC

-pro

mpt

= N

purit

yε

0.8

0.85

0.9

0.95

1

protonAu+Au 200GeV0-10%

=3)/2T

(pacc.×eff.εthreshold :

weak decay + knockout background>1GeV/c

T <1% at p

(GeV/c)T

p0 0.5 1 1.5 2

RC

-all

/ N

RC

-pro

mpt

= N

purit

yε

0.8

0.85

0.9

0.95

1

anti-protonacc.×eff.εthreshold<

<thresholdacc.×eff.ε

acc.×eff.εthreshold<<thresholdacc.×eff.ε

weak decay contribution>1GeV/c

T <1% at p

The purity of prompt particlesExtracted from HIJING and GEANT simulation.NRC-all particle : The number of reconstructed all of particles NRC-prompt particle : The number of reconstructed real prompt particles

7

"purity

=N

RC�prompt particle

NRC�all particle

F = A exp

(�✓

a

pT

◆b)

Sanshiro Mizuno, CiRfSE workshop

pT spectra correction

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

8

1

2⇡pT

d2N

dpT dy=

1

2⇡pT

1

Nevt

"purity"e↵.⇥acc.

N

�pT�y

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

2−10

1−10

1

10

210

positive+π+K

proton

Au+Au 200GeV, 0-10%STAR preliminary

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

2−10

1−10

1

10

210

negative-π-K

anti-proton

π, K, p pT spectra

9

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

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

3−10

2−10

1−10

1

10

210

310

STAR preliminaryFit to STAR preliminary

STAR (2004)PHENIX (2004)

Au+Au 200GeV, 0-10%+π

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

3−10

2−10

1−10

1

10

210

310

STAR (2006)

+K

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

3−10

2−10

1−10

1

10

210

310Inclusive protonInclusive protonPrompt proton

proton

(GeV/c)T

p0 1 2 3

Dat

a/Fi

t

0.5

1

1.5

2 +π

(GeV/c)T

p0 1 2 3

Dat

a/Fi

t

0.5

1

1.5

2 +K

(GeV/c)T

p0 1 2 3

Dat

a/Fi

t

0.5

1

1.5

2 proton

π, K, p pT spectra

Modify Hagedorn equationSTAR results (orange, cyan) : inclusive proton PHENIX results (magenta) : corrected for weak decay from Λ 10

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

A

{exp (�apT � bp2T ) + pT /p0}n

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

3−10

2−10

1−10

1

10

210

310

STAR preliminaryFit to STAR preliminary

STAR (2004)PHENIX (2004)

Au+Au 200GeV, 0-10%-π

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

3−10

2−10

1−10

1

10

210

310

STAR (2006)

-K

(GeV/c)T

p0 1 2 3

dy)

TN

/(dp

2)d Tp

π1/

(2

3−10

2−10

1−10

1

10

210

310Inclusive protonInclusive protonPrompt proton

anti-proton

(GeV/c)T

p0 1 2 3

Dat

a/Fi

t

0.5

1

1.5

2 -π

(GeV/c)T

p0 1 2 3

Dat

a/Fi

t

0.5

1

1.5

2 -K

(GeV/c)T

p0 1 2 3

Dat

a/Fi

t

0.5

1

1.5

2 anti-proton

11

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

π, K, p pT spectra

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

F =

A

{exp (�apT � bp2T ) + pT /p0}n

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3

Rat

io

0.4

0.6

0.8

1

1.2

STAR preliminary

+π/-πAu+Au 200GeV, 0-10%

(GeV/c)T

p0 1 2 3

Rat

io0.4

0.6

0.8

1

1.2+/K-K

(GeV/c)T

p0 1 2 3

Rat

io

0.4

0.6

0.8

1

1.2/pp

Anti-particle to particle ratio

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

12

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3

Rat

io

0.4

0.6

0.8

1

1.2

STAR preliminarySTAR (2004)PHENIX (2004)STAR (2006)

+π/-πAu+Au 200GeV, 0-10%

(GeV/c)T

p0 1 2 3

Rat

io0.4

0.6

0.8

1

1.2+/K-K

(GeV/c)T

p0 1 2 3

Rat

io

0.4

0.6

0.8

1

1.2

Inclusive protonInclusive protonPrompt proton

/pp

Anti-particle to particle ratio

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

13

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

Sanshiro Mizuno, CiRfSE workshop

)2(GeV/c0 - mTm0 0.5 1 1.5 2

dy)

TN

/(dm

2 d

0

10

20

T0-mTm

- expTF = A m

proton Au+Au 200GeV0-10%|y|<0.1

Estimating dN/dy distribution

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

measured dN/dy extrapolated dN/dylow pT

extrapolated dN/dyhigh pT

π+ 168.7 (53.5%) 146.7 (46.4%) 0.14 (0.1%)

K+ 26.8 (50%) 26.7 (49%) 0.1 (1%)

proton 11.1 (51%) 10.4(48%) 0.11 (1%)

Fraction of dN/dy

14

Out of range of measured spectraExtrapolating with equations The difference of equations are defined as systematic uncertainty.

Sanshiro Mizuno, CiRfSE workshop

partN0 100 200 300

dN/d

y

0

100

200

300 STAR preliminarySTAR (2004)PHENIX (2004)

+π

partN0 100 200 300

dN/d

y

0

20

40

60

+K

partN0 100 200 300

dN/d

y

0

10

20

30

40Inclusive protonPrompt proton

proton

partN0 100 200 300

dN/d

y

0

100

200

300-π

Au+Au 200GeV|y|<0.1

partN0 100 200 300

dN/d

y

0

20

40

60

-K

partN0 100 200 300

dN/d

y

0

10

20

30

40 anti-proton

dN/dy distribution

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

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

Sanshiro Mizuno, CiRfSE workshop

Summary

16

• 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

Sanshiro Mizuno, CiRfSE workshop

(GeV/c)T

p0 1 2 3 4

acc.

×ef

f.ε

1/

0

10

20

30

40 +πAu+Au 200GeV0-10%

(GeV/c)T

p0 1 2 3 4

acc.

×ef

f.ε

1/

0

10

20

30

40 +Kthreshold :

=3)/2T

(pacc.×eff.ε

acc.×eff.εthreshold<<thresholdacc.×eff.ε

(GeV/c)T

p0 1 2 3 4

acc.

×ef

f.ε

1/

0

10

20

30

40proton

Efficiency correction

"e↵.⇥acc. =

NRC�prompt particle

NMC�prompt particle

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