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

PHENIX Open Heavy Flavor: eHF One of the most surprising results from RHIC • Electrons fromHeavy quarks suppressed, and they flow. • Collective behavior is apparent in eHF; but HF v2is lower than v2 of p0 for pT > 2 GeV/c. PRC 84 (2011) 044905 Au+Au • Separating charm and bottom is the key to understand the mass hierarchy of energy loss.

What the Theory Telling us Probe deeper into the medium: Energy loss of heavy quarks nucl-th/0507019 hep-ph/1101.6008 hep-ph/0611109 Nucl-th/1205.2396 Most theories predict RAA(b e) > RAA (ce) Let’s find out!

Silicon Vertex Tracker e Life time (ct) D0 : 123 mm B0 : 464 mm Layer 3 e+ DCA e- Layer 2 D Beryliumbeampipe p p Layer 1 B Layer 0 e Barrel 3 Barrel 2 Barrel 1 Barrel 0 Barrel 0 Barrel 1 Barrel 2 Barrel 3 VTX: Silicon Barrels ~ 2p Main Goal

PHENIX-VTX in Action at RHIC VTX in Run 2012:p+p at 200 GeV VTX in Run 2011:Au+Au at 200 GeV Primary Vertex: BBC vs VTX Data: AuAu at 200 GeV y (cm) Beam size s (beam) ~ 90 um x (cm)

Conversion Electron Background Subtraction Layer 3 Layer 2 Layer 1 Layer 0 • - 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 • - 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. Associated Hit • Conversions in the beam pipe and B0, and Dalitz are suppressed by rejecting electron tracks with a nearby hit : Conversion Tag and Veto. Conversion Tag  B1 B-field B0 Hit by track

Conversion Electron Background Subtraction Fraction of HF electron after conversion Veto RHF = eHF/einc = eHF/(eHF+ ePH) • - 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. • 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. 90% heavy flavor e Photonic BG is small after conversion VETO

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 to bottom ratio is obtained from the fit to the DCA distribution of measured electrons: • Charm and Bottom events generated by PYTHIA are convoluted with DCA resolution to obtained expected DCA distribution shapes.

Distance of Closest Approach (DCA) Raw DCA distributions for charged hadrons and electronsp+p and Au+Au MB at 200 GeV Note: hadron contamination for electron DCA distributions is not subtracted in these plots

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 RHIC From Fit of the DCA distribution

Results: Bottom Production in p+p 200 GeV VTX direct measurement of b/b+c using DCA confirms published results using e-h correlation From Fit of the DCA distribution PHENIX Publisheddata agree With new data FONLLagree with data

Results: Bottom Production in p+p 200 GeV 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 Au+Au 200 GeV First direct measurement of bottom production in Au+Au at RHIC From Fit of the DCA distribution

Results: Bottom Production in Au+Au and p+p be /(be+ ce) in 200 GeV Au+Au vs p+p From Fit of the DCA distribution

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

RAA of Bottom Extraction x RAA (be) =

Nuclear Modification of Charm RAA (ce) Au+Au centrality: Min-Bias

Nuclear Modification of Charm RAA (ce) Charm (ce) is less suppressed than π0

Nuclear Modification of Charm and Bottom RAA (be) < RAA (ce) No simple mass hierarchy in heavy flavor

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(be) is strongly suppressed • Most theory predictions of RAA(be) > RAA(ce) are not supported by our data PHENIX-VTX opens new era of heavy flavor physics at RHIC

Auxiliary Slides 12/20/2019 rachid.nouicer@bnl.gov

Distance of Closest Approach (DCA) Raw DCA distributions for charged hadrons and electronsp+p at 200 GeV Note: hadron contamination for electron DCA distributions is not subtracted in these plots

Results: Bottom Production in Au+Au 200 GeV First direct measurements of bottom production in Au+Au at RHIC be /(be+ ce) in 200 GeV Au+Au vs Centrality From Fit of the DCA distribution Au+Au : 0-10% Au+Au : 10-60%

Nuclear Modification of Charm RAA (ce) Charm (ce) is less suppressed than π0

Results: RAA of Bottom and Charm Separately RAA of Bottom, Charm and published eHF in Au+Au MB Au+Au centrality: Min-Bias

Distance of Closest Approach (DCA): Au+Au s(DCA) ~ 70 um

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