Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20061
Study B and D Contributions to Non-photonic Electrons via Azimuthal Correlations between Non-Photonic Electrons and
Charged Hadrons Xiaoyan Lin
林晓燕(for the STAR Collaboration)
Central China Normal University
Wuhan, P.R. China
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20062
Motivation Data analysis
---- Electron identification
---- Photonic electron background
---- Electron-hadron correlations
Preliminary results of B/(B+D) Summary
Outline
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20063
Heavy quark RAA has the similar magnitude as light quark RAA.
The high pT region non-photonic electron RAA is surprising !
Where is the bottom contribution?
Features in Heavy Quark Measurements at RHIC----Non-Photonic Electron RAA
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20064
The decay kinematics of D and B mesons are different!
The same D and B v2 can lead to very different non-photonic electron v2 !
Features in Heavy Quark Measurements at RHIC----Non-Photonic Electron v2
Y. Zhang, hep-ph/0611182PYTHIA
Reduction of v2 at pT > 2 GeV/c.
Bottom contribution??
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20065
Quantitative understanding of features in heavy quark measurements requires experimental measurement of B and D contributions to non-photonic electrons !
Such information should be best obtained from direct measurement of hadronic decays of charm and bottom mesons.This motivates the STAR vertex detector upgrade! See Talk by Andrew Rose (1.4)
B and D Contributions to Electrons
Poor (wo)man’s approach to measure B/D contributions to non-photonic electrons
---- e-h correlationsX.Y. Lin, hep-ph/0602067
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20066
PYTHIA Simulation of e-h Correlations
B
D
Associated pT > 0.3 GeV/c. Significant difference in the near-side correlations. Width of near-side correlations largely due to decay kinematics.
X.Y. Lin, hep-ph/0602067
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20067
Major Detectors Used
Time Projection Chamber (TPC) Electro-Magnetic Calorimeter (EMC) Shower Maximum Detector (SMD)
Data Sample:
p+p collisions at sNN = 200 GeV in year 5 run.
2.37 million EMC HT1 triggered events with threshold 2.6 GeV; 1.68 million EMC HT2 triggered events with threshold 3.5 GeV.
Signal: Non-photonic electron
Background: HadronPhotonic electron
Charm decay
Bottom decay
Photon conversionπ0 Dalitz decayη Dalitz decaykaon decayvector meson decays
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20068
Electron ID Using TPC and EMC
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 20069
The purity of electron sample is above 98% up to pT ~ 6.5 GeV/c.
Electron ID Using TPC and EMC
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200610
The combinatorial background is small in p+p collisions. Reconstructed photonic = Opposite sign – Same sign. Photonic electron = reconstructed-photonic/ ε. ε is the background reconstruction efficiency calculated from simulations.
m<100 MeV/c2
Photonic Background
Electron candidates are combined with tracks passing a loose cut on dE/dx around the electron band. The invariant mass for a pair of photonic electrons is small.
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200611
All Tracks
Inclusive electron
Pass EID cuts
Non-photonic electron Photonic electron
Reco-photonic electron=OppSign - combinatorics
Not-reco-photonic electron=(1/eff-1)*(reco-photonic)
Procedure to Extract the Signal of e-h Correlations
Semi-inclusive electron
Signal:non-photonic = semi-inclusive +combinatorics-(1/eff-1)*reco-photonic Each item has its own corresponding Δφ histogram.
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200612
e-h Azimuthal Correlations after Bkgd. Subtraction
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200613
Use PYTHIA Curves to Fit Data Points
Fit function: R*PYTHIA_B+(1-R)*PYTHIA_D R is B contribution, i.e. B/(B+D), as a parameter in fit function.
B
D
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200614
B/(B+D) consistent varying fit range.
Use PYTHIA Curves to Fit Data Points
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200615
Preliminary Results: B Contribution .VS. pT
Error bars are statistical only! Data uncertainty includes statistic errors and systematic uncertainties from:
---- photonic background reconstruction efficiency (dominant).
---- difference introduced by different fit functions. Preliminary data is within the range that FONLL calculation predicts. Non-zero B contribution is observed.
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200616
Non-photonic electron and charged hadron correlations are sensitive to D and B contributions to non-photonic electrons.
We have measured e-h correlations in 200 GeV p+p collisions.
The preliminary data indicates at pT ~ 4-6 GeV/c the measured B contribution to non-photonic electrons is comparable to D contribution based on PYTHIA model.
Our measurement of B/(B+D) provides a constraint to the FONLL prediction.
Summary
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200617
Backup slides
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200618
Δφnon-pho = Δφsemi-inc + Δφcombinatorics - Δφnot-reco-pho
= Δφsemi-inc + Δφcombinatorics - (1/eff -1) *Δφreco-pho-no-partner
Method to Extract the Signal of e-h Correlations
non-pho. e = semi-incl. e +combinatorics - not-reco-pho. = semi-incl. e +combinatorics - (1/eff-1)*reco-pho.
Note Δφnot-reco-pho = (1/eff -1) *Δφreco-pho-no-partner! Δφreco-pho-no-partner is the reco-pho after removing the conversion partner. The photonic background has two parts: reco-pho and not-reco-pho. In electron yield or v2 analysis, the not-reco-pho part can just be calculated by reco-photonic part after an efficiency correction, i.e. not-reco-photonic = (1/eff-1)*reco-pho. However, in e-h correlation analysis, that is different. The reco-pho electron means we find the conversion partner, while the not-reco-pho electron means we miss the conversion partner. The resulting e-h correlations for these two parts are different. If we use reco-pho part to calculate the not-reco-pho part, we have to remove the conversion partner of reco-pho part.
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200619
The distributions of ChiSquare .VS. ratio_B
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200620
The distributions of ChiSquare .VS. ratio_B
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200621
Preliminary Results: B Contribution .VS. pT
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200622
-3σ < z distance < 3σ and -3σ < φdistance < 3σ were set to remove lots of random associations between TPC tracks and BEMC points.
Electron Identification: Projection Distance
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200623
PYTHIA Simulation: e pT .VS. parent pT
C-quark needs to have larger momentum than b-quark to boost the decayed electron to high pT.
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200624
PYTHIA Simulation: e pT .VS. hadron pT
The efficiency of associated pT cut is different between D decay and B decay. Therefore, it is better to use lower pT cut on the associated particles in order to avoid analysis bias!
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200625
PYTHIA Simulation: e pT .VS. hadron pT
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200626
PYTHIA parameters used in this analysis
PYTHIA version: v6.22
δ fragmentation function used for both charm and bottom.
Parameters for charm: PARP(67) = 4 (factor multiplied to Q2)
<kt> = 1.5 GeV/c
mc = 1.25 GeV/c2
Kfactor = 3.5MSTP(33) =1 (inclusion of K factor)MSTP(32) = 4 (Q2 scale)CTEQ5L PDF
Parameters for bottom are the same as for charm except
mb = 4.8 GeV/c2.X.Y. Lin, hep-ph/0602067
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200627
Near-side width due to decay kinematics
All hadrons Hadrons from D
Backgroundwith δ fragmentation function
Xiaoyan Lin Quark Matter 2006, Shanghai, Nov. 14-20, 200628
Near-side width does not strongly depend on FF
2.5-3.5 GeV/c 3.5-4.5 GeV/c
4.5-5.5 GeV/c 5.5-6.5 GeV/c
Will be included in the systematic uncertainties in the future.
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