Xiaoyan Lin 林晓燕 (for the STAR Collaboration) Central China Normal University Wuhan, P.R. China
description
Transcript of 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, 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.