Probing Hot and Dense Matter with Charm and Bottom Measurements with PHENIX VTX Tracker

Probing Hot and Dense Matter with Charm and Bottom Measurements

with PHENIX VTX Tracker

Rachid Nouicer, BNL

for the PHENIX Collaboration

Quark Matter 2012 International Conference,August 13-18, 2012, Washington, DC 20008 USA

2Rachid Nouicer Quark Matter 2012

PHENIX Open Heavy Flavor: eHF

One of the most surprising results from RHIC

Separating charm and bottom is the key to understand the mass

hierarchy of energy loss.

Au+Au

PRC 84 (2011) 044905 Electrons from Heavy quarks suppressed, and they flow.

Collective behavior is apparent in eHF; but HF v2

is lower than v2 of 0

for pT > 2 GeV/c.


What the Theory Telling usProbe deeper into the medium: Energy loss of heavy quarks

Let’s find out!

nucl-th/0507019

Most theories predict RAA(b e) > RAA (ce)

hep-ph/0611109

Nucl-th/1205.2396

hep-ph/1101.6008


Silicon Vertex Tracker

e+e

VTX: Silicon Barrels ~ 2

Layer 0

Layer 1

Layer 2

Layer 3

Life time (c) D0 : 123 m B0 : 464 m

DCA

ppD

B

e

e

Barrel 0Barrel 1Barrel 2Barrel 3

Barrel 0Barrel 1Barrel 2Barrel 3

Goal

Beryliumbeampipe

Main


PHENIX-VTX in Action at RHICVTX in Run 2011: Au+Au at 200 GeVVTX in Run 2012: p+p at 200 GeV

Beam size

Data: AuAu at 200 GeVPrimary Vertex: BBC vs VTX

(beam) ~ 90 um

x (cm)

y (

cm)


- Challenge in the DCA measurement of single electrons is the Conversion Electron Background (CEB).

- Most conversions happen in the outer layers (total radiation length = 12 % (B0: 1.3%, B1: 1.3%, B2:4.7% and B3: 4.7%). They are suppressed by requiring a hit in inner silicon layer B0.

Conversion Electron Background Subtraction

Layer 0

Layer 1

Layer 2

Layer 3





- Conversions in the beam pipe and B0, and Dalitz are suppressed by rejecting electron tracks with a nearby hit : Conversion Tag and Veto.

Hit by track

B-field

Associated Hit

Conversion Tag

B1

B0




Fraction of HF electron after conversion Veto RHF = eHF/einc = eHF/(eHF+ ePH)


90% heavy flavor e

Photonic BG is smallafter conversion VETO

- Conversions in the beam pipe and B0, and Dalitz are suppressed by rejecting electron tracks with a nearby hit : Conversion Tag and Veto.

- Yield of the remaining conversions and Dalitz are estimated using the veto efficiency.


HF Invariant Yield in Au + Au

• Using VTX to tag Dalitz and conversion electrons, we measure the heavy flavor (HF) electron spectra

Run 2011 HF spectrum consistent with previously publishedHF byPHENIX


Decomposition of the DCA Distributions

- VTX provides another new capability:

• Measure distance of closest approach to separate charm and bottom components of heavy flavor spectra

• Charm and Bottom events generated by PYTHIA are convoluted with DCA resolution to obtained expected DCA distribution shapes.

- Charm to bottom ratio is obtained from the fit to the DCA distribution of measured electrons:


Raw DCA distributions for charged hadrons and electrons

p+p and Au+Au MB at 200 GeV

Note: hadron contamination for electron DCA distributions is not subtracted in these plots

Distance of Closest Approach (DCA)


Electron Distance of Closest Approach (DCA)


Electron Distance of Closest Approach (DCA) c/(b+c) = 0.92 ± 0.02


Results: Bottom Production in p+p 200 GeV First direct measurements of bottom production in

p+p at RHICFrom Fit of the DCA distribution


From Fit of the DCA distribution

Results: Bottom Production in p+p 200 GeV

FONLLagree

with data

PHENIX Published

dataagree

With new data

VTX direct measurement of b/b+c using DCA confirms published results using e-h correlation


First direct measurement of bottom production in p+p at RHIC

From Fit of the DCA distribution

STAR indirect measurement consistent

with our data

Results: Bottom Production in p+p 200 GeV


Results: Bottom Production in Au+Au 200 GeV First direct measurement of bottom production in

Au+Au at RHICFrom Fit of the DCA distribution


be /(be+ ce) in 200 GeV Au+Au vs p+pFrom Fit of the DCA distribution

Results: Bottom Production in Au+Au and p+p


p+p: b/(b+c) Fitted by FONNL


RAA (be) =

RAA of Bottom Extraction

x


RAA (be) =


x


Nuclear Modification of Charm RAA (ce)

Au+Au centrality: Min-Bias


Charm (ce) is less suppressed than 0



No simple mass hierarchy in heavy flavor

RAA (be) < RAA (ce)

Nuclear Modification of Charm and Bottom


Summary

• First measurements of Charm and Bottom separately in heavy ion collisions at RHIC achieved

• In p+p, FONLL prediction of b/(b+c) agrees with the data

• In Au+Au, RAA(be) is strongly suppressed

• Most theory predictions of RAA(be) > RAA(ce) are not supported by our data

PHENIX-VTX opens new era of heavy flavor physics at RHIC

37Rachid Nouicer Quark Matter 201204/21/23 [email protected]

Auxiliary Slides


Raw DCA distributions for charged hadrons and electrons

p+p at 200 GeV

Note: hadron contamination for electron DCA distributions is not subtracted in these plots

Distance of Closest Approach (DCA)


Au+Au : 0-10% Au+Au : 10-60%

be /(be+ ce) in 200 GeV Au+Au vs CentralityFrom Fit of the DCA distribution

Results: Bottom Production in Au+Au 200 GeV First direct measurements of bottom production in

Au+Au at RHIC


Charm (ce) is less suppressed than 0



Results: RAA of Bottom and Charm Separately

RAA of Bottom, Charm and published eHF in Au+Au MB

Au+Au centrality: Min-Bias


(DCA) ~ 70 um

Distance of Closest Approach (DCA): Au+Au

Probing Hot and Dense Matter with Charm and Bottom Measurements with PHENIX VTX Tracker

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