gang wang, wwnd 20091 non-photonic electron-hadron correlations at rhic gang wang (university of...
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Gang Wang, WWND 2009 1
Non-Photonic Electron-Hadron Correlations at RHIC
Gang Wang(University of California, Los Angeles)
Gang Wang, WWND 2009 2
Outline
Motivation
Analysis procedure
Near-side contribution in p+p collisions
Away-side broadness in A+A collisions
Outlook
Gang Wang, WWND 2009 3
Conical Pattern in Conical Pattern in 2-Particle Correlations in Au+Au Collisions
pTtrig = 2.5-4.0 GeV/c;
pTasso = 1.0-2.5 GeV/c
Motivations
Mark Horner (for STAR Collaboration): J. Phys. G: Nucl. Part. Phys. 34 (2007) S995
The away-side correlation structure in Au+Au is different than p+p or d+Au.
PHENIX, PRC 78 (2008) 014901
Gang Wang, WWND 2009 4
Conical Pattern in Conical Pattern in 2-Particle Correlations in Au+Au Collisions
pTtrig = 2.5-4.0 GeV/c;
pTasso = 1.0-2.5 GeV/c
Motivations
Mark Horner (for STAR Collaboration): J. Phys. G: Nucl. Part. Phys. 34 (2007) S995
Further support by 3-particle correlations
See STAR paper on 3-particle correlations at arXiv:0805.0622v2 (accepted by PRL)
Conical PatternConical Pattern
Gang Wang, WWND 2009 5
Away Side in medium: How does B/D lose energy? Via conical emission?
Conical Pattern in Conical Pattern in 2-Particle Correlations in Au+Au Collisions
pTtrig = 2.5-4.0 GeV/c;
pTasso = 1.0-2.5 GeV/c
Motivations
Mark Horner (for STAR Collaboration): J. Phys. G: Nucl. Part. Phys. 34 (2007) S995
Near Side:what’s the contribution of B/D decay to the non-photonic electrons?
trigger
What if we trigger on non-photonic electrons?
Gang Wang, WWND 2009 6
Study of heavy flavor via non-photonic electrons
• D mesons have their directions well represented by the daughter electrons, above 1.5 GeV/c.
• Electrons from B decays can represent the B meson momentum direction well if pT > 3 GeV/c.
PYTHIA
Gang Wang, WWND 2009 7
Time Projection Chamber (TPC) Barrel Electro-Magnetic Calorimeter (BEMC) Barrel Shower Maximum Detector (BSMD)
Data Sample:
At sNN = 200 GeV,
p+p collisions in run5/6 (2006), d+Au collisions in run8 (2008), Cu+Cu collisions in run5 (2005), Au+Au collisions in run7 (2007).
Electron ID in STARPurity
dAu, CuCu, AuAu: above 98% for 3 < pT < 6 GeV/c
p+p collisions: above 98% for 3 < pT < 6 GeV/c; 80% for 9 GeV/c.
Gang Wang, WWND 2009 8
Decay photon conversions→ → e+ e- in materialMain background
Dalitz decays→ e+ e-
Direct photon conversionsSmall but could be significant at high pT
Heavy flavor electronsD/B → e± + X
Weak Kaon decays
Ke3: K± → e± e
< 3% contribution in pT > 1 GeV/c
Vector Meson DecaysJ→ e+e-< 2-3% contribution in all pT
Photonic electronNon-photonic electron
Electron signal and background
Gang Wang, WWND 2009 9
Photonic Background
• The invariant masses of the OS and SS e-pairs have different distributions.• Reconstructed photonic electron is the subtraction.• Photonic electron is the reconstructed-photonic/ ε• ε is the background reconstruction efficiency calculated from simulations.
e-
e+
e-
(assigned as primary track)
(global track)
(primary track)dca
Gang Wang, WWND 2009 10
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
Δφnon-pho = Δφsemi-incl + ΔφSameSign – (1/eff -1)*(ΔφOppSign – ΔφSameSign)Each item has its own corresponding Δφ histogram.
In case of low purity…
– Δφhadron
Gang Wang, WWND 2009 11
Near-Side contribution in p+p
Gang Wang, WWND 2009 12
Clear azim. correlation is observed around near and away side.
Fitting measured dn/dφ distribution from B and D decays, we can estimate B decay contribution to non-photonic electron.
)/(
)1(
BDB
Dhe
Bhehe
eeer
rr
Non-photonic e-h correlations in p+p 200GeV
B
D
Gang Wang, WWND 2009 13
Almost half-half B and D contributions to non-photonic e’s at 5.5 < pT < 9 GeV/c, and FONLL prediction is consistent with our data within errors.
B contribution to non-photonic e in p+p 200GeV
Gang Wang, WWND 2009 14
RAA for non-photonic electron is consistent with hadron’s.This Indicate large energy loss not only charm quark but also bottom quark.
Large bottom energy loss?
)/(
)1(
)(
)(
)(
ppC
ppB
ppB
ecAA
ebAA
ppC
ppB
ppC
ppCbin
AAC
ppC
ppB
ppB
ppBbin
AAB
ppC
ppBbin
AAC
AAB
AA
eeer
RrrR
ee
e
eN
e
ee
e
eN
e
eeN
eeR
With the measurements of r @ pp and RAA, we can derive a relationship between RAA
ec and RAAeb.
non-γ ehadron
Gang Wang, WWND 2009 15
o RAAec & RAA
eb correlation together with models
o Dominant uncertainty is normalization in RAA analysis
o RAAeb < 1; B meson is also
suppressed
o prefer Dissociate and resonance model (large b energy loss)I: Djordjevic, Gyulassy, Vogt and Wicks, Phys. Lett. B 632 (2006) 81; dNg/dy = 1000
II: Adil and Vitev, Phys. Lett. B 649 (2007) 139III: Hees, Mannarelli, Greco and Rapp, Phys. Rev. Lett. 100 (2008) 192301
STAR preliminary
pT > 5 GeV/c
RRAAAAecec & R & RAAAA
ebeb correlation correlation
Gang Wang, WWND 2009 16
Summary I Non-photonic e-h correlations have been measured in p+p collisions to retrieve B and D contributions to non-photonic electrons up to pT~9 GeV/c.
Comparable B and D contributions for electron pT 5.5~9 GeV/c.
FONLL prediction and the eB/(eB+eD) results are consistent with each other within errors.
The measured B/D ratio would imply considerable b quark energy loss in medium based on RAA measurement from central Au+Au collisions. One more measurement is needed: RAA
eb, RAAec or r@A+A.
Gang Wang, WWND 2009 17
Away-side broadness in A+A
d+Au collisions serve as a reference of the cold nuclear matter…
Gang Wang, WWND 2009 18
Non-photonic e-h correlations in d+Au 200 GeV
Non-photonic e-h azimuthal correlation is measured in one π range,and open markers are reflections. The away-side correlation can be well described by PYTHIA calculations for p+p. No medium effects seen here.
3 < pTtrig < 6 GeV/c & 0.15 < pT
asso < 0.5 GeV/c
STAR Preliminary
Gang Wang, WWND 2009 19
about 40% non-flow or fluctuation(Gang Wang, Nucl. Phys. A 774 (2006) 515.)
Non-photonic e-h correlations in Cu+Cu 200 GeV
Upper limits of v2 used are 60% of hadron v2 values measured with the v2{EP} method (equivalent to v2{2}).
0 – 20%: 3 < pTtrig < 6 GeV/c & 0.15 < pT
asso < 0.5 GeV/c
On the away side, there’s a broad structure or a possible double-hump feature, even before v2 subtraction. PYTHIA fit has a big χ2.
Gang Wang, WWND 2009 20
Possible interpretations
The away side in e-h is similar to what has been observed in h-h correlations, and consistent with Mach Cone calculations etc. The charm jet deflection provides an alternative interpretation.
3 < pTtrig < 6 GeV/c & 0.15 < pT
asso < 0.5 GeV/c
Gang Wang, WWND 2009 21
Non-photonic e-h correlations in Au+Au 200 GeV
Upper limits of v2 used are 80% of hadron v2 values measured with the v2{EP} method. Non-photonic e-h correlation is broadened on the away side. PYTHIA fit has a big χ2.
0 – 20%: 3 < pTtrig < 6 GeV/c & 0.15 < pT
asso < 0.5 GeV/c
STAR Preliminary
Gang Wang, WWND 2009 22
Non-photonic e-h correlations in PHENIX
More statistics needed …
Anne Sickles, DNP08 talk. Also see the talk after mine ...
Gang Wang, WWND 2009 23
Using the d+Au collision as a reference, the shape of non-photonic e-h azimuthal correlation function is found to be modified in central Cu+Cu and Au+Au collisions due to the presence of the dense medium created in these collisions.
Away-side: Hint of a broad structure, similar shape to that from h-h correlations.
Induced by heavy quark interaction with the dense medium?
Quantitative measure and investigation of the nature of the possible conical emission pattern will require more statistics! DAQ1000 will help us there! Should try 3-particle correlations!
Here demonstrated is the feasibility of the analysis on
the jet-medium interaction tagged by a heavy quark.
Summary II
Gang Wang, WWND 2009 24
OutlookLarge associated particle yields on the near side leave open questions: collective medium excitation by heavy quarks?
Momentum kick model, Cheuk-Yin Wong
Gang Wang, WWND 2009 25
Back up slides
Gang Wang, WWND 2009 26
HQ Production Mechanism Due to large mass, HQ
productions are considered as point-like pQCD processes
HQ is produced at the initial via leading gluon fusion, and sensitive to the gluon PDF
NLO pQCD diagrams show that Q-Qbar could be not back-to-back in transverse plane
We need to study this smearing effect with models
0
flavor creation
gluon splitting
Gang Wang, WWND 2009 27
PYTHIA simulations
B
DFor each pt bin, the non-photonic e-h correlations B_corr and D_corr are combined according to B’s and D’s relative contributions to the non-photonic electrons:(eB*B_corr + eD*D_corr) / (eB+eD)
Each pt bin is weighted with their relative yields, and then they are summed up.
Gang Wang, WWND 2009 28
Electron ID in STAR
With BEMC and BSMD, the electron peak is enhanced in the energy loss distribution, and we obtain a very pure electron sample.
Purity
dAu, CuCu, AuAu: above 98% for 3 < pT < 6 GeV/c
p+p collisions: above 98% for 3 < pT < 6 GeV/c; 80% for 9 GeV/c.
calibrated Log(dE/dx)
Gang Wang, WWND 2009 29
PYTHIA simulations weighted with CuCu yields3 < pT
trig < 6 GeV/c & 0.15 < pTasso < 0.5 GeV/c
Here we assume the B/D contribution in CuCu is similar to that in p+p. Even if they are not similar, we don’t expect the double-hump without a medium.
B D
Gang Wang, WWND 2009 30
Electron ID in PHENIX
Also see the talk after mine ...
• PHENIX central arm coverage:– || < 0.35– = 2 x π/2– p > 0.2 GeV/c
– typical vertex selection: |zvtx| < 20 cm
• charged particle tracking analysis using DC and PC1
• electron identification based on– Ring Imaging Cherenkov detector
(RICH) – Electro-Magnetic Calorimeter (EMC)