nuclear modification factors of d meson in au+au collisions ......(for the star collaboration) sept....

1 Guannan Xie

Nuclear Modification Factors of D0 Meson in Au+Au Collisions at √sNN = 200 GeV

University of Science and Technology of China Lawrence Berkeley National Laboratory

(for the STAR Collaboration)

Sept. 27 - Oct 3, 2015, Kobe, Japan

Guannan Xie

Outline

•  Physics Motivation

•  STAR with Heavy Flavor Tracker •  Analysis Details

–  D0 Reconstruction & Efficiency correction

•  Results & Discussion

•  Summary & Outlook

2 Quark Matter 2015, Kobe, Japan Guannan Xie

Motivation


Perturbative QCD calculations (FONLL) are consistent with experimental data.

STAR Preliminary

Charm quarks: mc >> TC, ΛQCD, mu,d,s TQGP(RHIC/LHC) •  Produced early in collision at RHIC through hard scattering •  Experience the whole evolution of the system -> good probe for medium properties

STAR Preliminary STAR: PRD 86 (2012) 072013, NPA 931 (2014) 520 CDF: PRL 91 (2003) 241804 ALICE: JHEP01 (2012) 128 FONLL: PRL 95 (2005) 122001

binnumber of binary collisions N

1 10 210 310

b)µ (

y=0

/dy|

ccNN

σd

0

50

100

150

200

250

300

350

400

FONLL in p+p

FONLL err.

NLO err.

d+Au+e)0(D

)0Au+Au (Dp+p

+D*)0(D

= 200 GeVNNS

Sys. error

run9

run12

Motivation


Charm cross section follows number of binary collisions scaling => At RHIC, charm quarks are produced via initial hard scatterings.

STAR Preliminary

Perturbative QCD calculations (FONLL) are consistent with experimental data.

Charm quarks: mc >> TC, ΛQCD, mu,d,s TQGP(RHIC/LHC) •  Produced early in collision at RHIC through hard scattering •  Experience the whole evolution of the system -> good probe for medium properties

STAR: PRL 94 (2005) 62301, PRD 86 (2012) 072013, PRL 113 (2014) 142301 FONLL: PRL 95 (2005) 122001 NLO: Eur.Phys.J.ST 155 (2008) 213

Results Before HFT


•  Precision measurement is needed to further constrain models and to quantify medium properties.

•  New run 2014 Au+Au results with HFT will be presented -- p+p and p+Au data with HFT are recorded on tape (run 2015)

•  High pT: large suppression due to

energy loss, strong charm-medium interaction.

•  Enhancement at pT ~0.7-2 GeV/c, described by models with coalescence of charm and light quarks.

0 2 4 60

0.5

1

1.5

2

)A

AF

acto

r (R 40-80% (a)

0 2 4 6 8

10-40% (b)

(GeV/c)T

p0 2 4 6 80

0.5

1

1.5

2

Nu

clea

r M

od

ific

atio + X @ 200 GeV Central 0-10%0 D→STAR Au+Au

dataTAMUSUBATECHTorinoDuke w shad.Duke w/o shad.LANL

STAR: PRL 113 (2014) 142301

STAR Detector


Time Projection Chamber: Tracking, PID (dE/dx)

Time Of Flight detector: PID (1/β)

Vertex Position Detector: minimum bias trigger

Heavy Flavor Tracker

HFT: •  Silicon Strip Detector: r ~22 cm •  Intermediate Silicon Tracker: r ~14 cm •  PIXEL detector: r ~2.8 & 8 cm, MAPS, 20x20 µm2, 0.4%X0 thick, air-cooled See talk by G. Contin (Tue. 15:00)

HFT Performance

Quark Matter 2015, Kobe, Japan Guannan Xie

DCA (Distance of Closest Approach) resolution •  ~ 30 µm at high pT

•  Kaon with p = 750 MeV/c, DCA resolution <50 µm

PIXEL detector DCA Resolution

Au+Au @ 200GeV Run2014, with Heavy Flavor Tracker ~780M minimum bias events analyzed (out of total 1.2B recorded in 2014)

7

Run14 Au+Au @ 200 GeV

D0 Meson Reconstruction


Direct topological reconstruction through hadronic channel:

With HFT: Greatly reduced combinatorial background

D0 w/o HFT with HFT

Year 2010 + 2011 2014

# Events (MB) analyzed 1.1 B 780M

Significance per billion events

13 51

D0 (D0 )→ K ∓π ±(BR 3.89%)cτ ≈120µm

TopologicL cuts optimized by TMVA (Toolkit for Multi Variate Analysis)

D0 Meson Signal


)2 (GeV/cπKM1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

]310×

) [2C

ount

s/(1

0 M

eV/c

0

5

10

15

20

25

30

unlike, same evtlike, same evtunlike, mixed evt

Au+Au 200GeV, 0-80% MB < 2.0 GeV/c

T1.0 < p

360± = 8038 0#D=22.3S+BS/

)2 (GeV/cπKM1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

)2C

ount

s/(1

0 M

eV/c

0

20

40

60

80

100

120

140

160

180

200

220

unlike, same evtlike, same evtunlike, mixed evt

Au+Au 200GeV, 0-80% MB < 8.0 GeV/c

T5.0 < p

29± = 417 0#D=14.4S+BS/

•  Clean D0 signals reconstructed with significantly enhanced signal-to-background ratios with the HFT in a broad range of transverse momentum

STAR Preliminary

STAR Preliminary

Efficiency Correction

Embedding (~3% systematic uncertainty) –  Full STAR GEANT simulation + MC embedded in real raw data + data reconstruction chain


⊗D0 efficiency = TPC tracking eff HFT tracking eff topological cuts ⊗

Data-driven simulation (5-15% pT-dependent systematics) •  HFT matching and resolution smearing using distributions extracted

from data: –  HFT eff. × geometrical acceptance: (HFT matched tracks) / TPC tracks. –  Spatial resolution: DCA distributions of HFT matched tracks (XY-Z dependence).

Luminosity, centrality, azimuth and pseudo-rapidity dependence have been considered.

Invariant yields


(GeV/c)T

p0 1 2 3 4 5 6 7 8

]-2

dy) [

(GeV

/c)

Tdp Tpπ

N/(2

2 d

8−10

7−10

6−10

5−10

4−10

3−10

2−10

1−10

Au+Au 0-10%

2014 [/20]0D

2010/11 [/20]0D

@ Au+Au 200 GeV0STAR D

+D*0p+p D

>bin

p+p Levy scaled by <N

•  [High pT] Consistent with published result, with improved statistical precision

STAR Preliminary

- Finalizing systematic uncertainties for pT< 2 GeV/c and in peripheral collisions

STAR: PRL 113 (2014) 142301

(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D

2010/110D

Nuclear Modification Factors


•  High pT: significant suppression in central Au+Au collisions. New results have improved precision.

•  p+p precision to be improved using 2015 data with HFT

STAR: PRL 113 (2014) 142301

STAR Preliminary

(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D 2010/110D

0-12% STARπ

D0 vs. π


•  RAA(D) ~ RAA(π) at pT>4 GeV/c Similar energy loss for light partons and charm quarks at high pT

STAR: PRL 113 (2014) 142301 PLB 655 (2007) 104

STAR Preliminary

(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D 2010/110D

D 0-10% ALICE

RHIC vs. LHC


•  RAA@ RHIC ~ RAA@LHC strong charm-medium interaction at RHIC and LHC

STAR: PRL 113 (2014) 142301 ALICE: arXiv: 1509.06888

STAR Preliminary

(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D 2010/110D

DUKE

Comparison to Models


STAR: PRL 113 (2014) 142301 DUKE: PRC 92 (2015) 024907 A. Andronic arXiv:1506.03981(2015)

DUKE: Langevin simulation, input parameter （2πT）D=7 (tuned to the LHC data)

STAR Preliminary

Theory curves: latest calculations from private communications

(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D 2010/110D

DUKETAMU



DUKE: Langevin simulation, input parameter （2πT）D=7 (tuned to the LHC data) TAMU: non-perturb., (2πT)D = 2-10


STAR Preliminary


(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D 2010/110D

DUKETAMUSUBATECH



DUKE: Langevin simulation, input parameter （2πT）D=7 (tuned to the LHC data) TAMU: non-perturb., (2πT)D = 2-10 SUBATECH: perturb.+resummation, (2πT)D = 2-4

STAR Preliminary


For v2, see talk by M. Lomnitz (Tue. 9:00)


)2(GeV/c�KInvariant mass, m

1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 2.1

)2C

ount

s (p

er 1

0 M

eV/c

0

100

200

300

400

500

600

700

STAR Preliminary= 200 GeVNNsAu+Au

RHIC Run 2014125M MinBias Events

= 18S+BS/

Summary & Outlook

•  First measurement of D0 RAA using STAR HFT. –  Significant suppression at high pT in 0-10% Au+Au collisions at √sNN = 200 GeV –  Improved data precision with HFT will further constrain different models

•  Near future outlook

–  D0 spectra and RAA with HFT in full pT and peripheral Au+Au collisions –  Year 2015 p+p and p+Au data to improve baseline and to address CNM effects


(GeV/c)T

p0 2 4 6 8

AAR

0

0.5

1

1.5

2

p+p uncert.

@ 200 GeV 0-10%0 D→Au+Au

20140D

2010/110D

STAR Preliminary

Thank You


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nuclear modification factors of d meson in au+au collisions ......(for the star collaboration) sept....

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