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

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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.

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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

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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

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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)

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- 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

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- 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

- 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

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- 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.

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

Conversion Electron Background Subtraction

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.

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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

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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:

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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)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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Electron Distance of Closest Approach (DCA)

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

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Electron Distance of Closest Approach (DCA) c/(b+c) = 0.81 ± 0.05

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Electron Distance of Closest Approach (DCA) c/(b+c) = 0.78 ± 0.06

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

p+p at RHICFrom Fit of the DCA distribution

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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

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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

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

Au+Au at RHICFrom Fit of the DCA distribution

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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

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

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RAA (be) =

RAA of Bottom Extraction

x

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RAA (be) =

RAA of Bottom Extraction

x

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RAA (be) =

RAA of Bottom Extraction

x

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RAA (be) =

RAA of Bottom Extraction

x

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Nuclear Modification of Charm RAA (ce)

Au+Au centrality: Min-Bias

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Charm (ce) is less suppressed than 0

Nuclear Modification of Charm RAA (ce)

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No simple mass hierarchy in heavy flavor

RAA (be) < RAA (ce)

Nuclear Modification of Charm and Bottom

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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 rachid.nouicer@bnl.gov

Auxiliary Slides

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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)

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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

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Charm (ce) is less suppressed than 0

Nuclear Modification of Charm RAA (ce)

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Results: RAA of Bottom and Charm Separately

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

Au+Au centrality: Min-Bias

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(DCA) ~ 70 um

Distance of Closest Approach (DCA): Au+Au