some aspects of heavy flavor physics in alice: the “other” hard probe
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Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Some Aspects of Heavy Flavor Physics in ALICE:
the “Other” Hard Probe
V. Ghazikhanian
UCLA
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Heavy Quark Production Mechanism
• Sensitive to initial gluon density and gluon distribution
0D
D0
J/
K+
l
l
K-
e-/-
e+/+
e-/-
e+/+
• Energy loss when propagating through dense medium
• Different scaling properties in central and forward region indicate shadowing, which can be due to CGC.
• Suppression/enhancement of charmonium in the medium is
a critical signal for QGP.
• Sensitive to initial gluon density and gluon distribution
to these one needs to add photoproduction mechanism
(see Spencer’s presentation)
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Parton Distribution Function
Bx
Ax
2 1 21 2 1 2
1 2
1 21 2
1 2
ˆ
1ln
2
exp ; exp
ppQQ
zQQ
z
QQ QQ
QQ QQpp pp
Z ZM s x x s x x s
A A
E py
E p
M MA Ax y x y
Z Zs s
A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
2ˆ s RE C q L
Parton Energy Loss
Casimir coupling factor:4/3 for quarks3 for gluons
Medium transport coefficient gluon density and momenta
R.Baier, Yu.L.Dokshitzer, A.H.Mueller, S.Peigne' and D.Schiff, (BDMPS), Nucl. Phys. B483 (1997) 291.
hardparton
path length L
• Due to medium-induced gluon radiation
• Average energy loss (BDMPS model):
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
ALICE Heavy Flavor Acceptance
arXive:hep-ph/0311048 v1 4 Nov. 2003
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Some Heavy flavor quenching observables
• Inclusive:– Suppression of dilepton invariant mass spectrum
– Suppression of lepton spectra– Non-photonic electrons
• Exclusive jet tagging:– High- pT lepton ( ) & displaced vertex– Hadronic decay (ex. D0 K-p+ ) & displaced vertex
B D
+ - + - + -DD , ,BB B
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Open Charm Production At LHC/ALICE
A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Detecting D-Mesons via Hadronic Decays
• Hadronic Channels:– D0 K (B.R.: 3.8%) – D0 K (B.R.: 6.2% 100% () = 6.2%)– D K p (B.R.: 9.1%)– D*± D0π (B.R.: 68% 3.8% (D0 K ) = 2.6%) c p K (B.R.: 5%)
pc
xMxxP
0
0 exp)(
Huan Huang
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
•Weak decay with mean proper length ct = 124 μm•Impact Parameter (distance of closest approach of a track to the primary vertex) of the decay products d0 ~ 100 μm
•STRATEGY: invariant mass analysis of fully-reconstructed topologies originating from (displaced) secondary vertices
–Measurement of Impact Parameters–Measurement of Momenta–Particle identification to tag the two decay products
Detection strategy for D0 K- p+
A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Hadronic charmCombine ALICE tracking + secondary vertex finding capabilities (sd0~60mm@1GeV/c pT) + large acceptance PID to detect processes as D0K-+ ~1 in acceptance / central event ~0.001/central event accepted after rec. and all cuts
S/B+S ~ 37 S/B+S ~ 8
for 1<pT<2 GeV/c(~12 if K ID required)
significance vs pT
Results for 107 PbPb ev. (~ 1/2 a run)
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Initial Signal Significance
A. Dainese, PhD. Thesis [arXive:nucl-ex/0311004
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
D0 Cross section measurement
pp, 14 TeV
mc
scalesPDFs
down ~ 0!down to 1 GeV/c!
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
A.Dainese nucl-ex/0311004
/1
/AA t
AAcoll pp t
dN dpR
N dN dp
q …medium transport coefficient depends on gluon density, momenta
D quenching (D0 K-p+ )
Ratio D/hadrons (or D/π0) enhanced and sensitive to medium properties
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
V2 of J/psi
V2 of J/psi can differentiate scenarios !
pQCD direct J/psi should have no v2 !
Recombination J/psi can lead to non-zero v2 !
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Detecting Charm/Beauty via Semileptonic D/B Decays
• Semileptonic Channels:– D0 e+ + anything (B.R.: 6.87%) – D e + anything (B.R.: 17.2%)– B e + anything (B.R.: 10.2%)
single “non-photonic” electron continuum
• “Photonic” Single Electron Background: conversions (0 ) 0, Dalitz decays , , … decays (small)– Ke3 decays (small)
mBc
MmD
c
Mpc
xMxxP
/ MeV11)( ; / MeV15)(
exp)(
00
00
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Even
ts/1
00 M
eV
103
J/Y
5 10 15
102
dN/d=8000
0
• 1 month statistics of PbPb √sNN=5.5 TeV
c/b Quarkonia
arXive:hep-ph/0311048 v1 4 Nov. 2003
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Hadron and Lepton Identification
ALICE PPR CERN/LHCC 2003-049
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Summary/Outlook • ALICE Heavy flavor Physics is complementary to that of RHIC and will extend x reach where Gluon structure function dominates.
• just as in RHIC (and perhaps even more) one needs to follow a program of complete set of measurements (RAA, RCP, dN/dY, v2, …) for AA systems, and also need yields from pp and pA for open charm (beauty) and quarkonium states. [pp and pA will provide information on basic production rates and nuclear shadowing effects (and nuclear absorption/energy loss), respectively].
• Need to have good control over photonic vs. non-photonic electrons in semileptonic open charm/beauty decay (TRD needed in front of EMC, TOF and EMC to extend pT ~ 3-10 GeV/c in order to extend PID in the region where b contribution dominates that of c quarks)!
• Trigerring on heavy flavor mesons: high pt electrons (high tower trigger in EMC, TRD), also triggering on muons in the muon spectrometer + electrons in EMC (to look for b decay chain proceeding via b -> mu + c -> e (EMC)).
• more studies are needed both on theory front and experimental side [e.g., better energy loss estimates for partons in deconfined nuclear matter/QGP and for quarkonia; need further simulation on detector/trigger performance for TRD+EMC+TOF+ITS].
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Nuclear Modification Factors
ddp
Nd
collddpNd
TAA
T
pp
T
AA NpR 2
2
/)(
Use number of binary nucleon-nucleon collisions to scale the colliding parton flux:
N-binary Scaling RAA or RCP = 1 simple superposition of independent nucleon-nucleon collisions !
Peripheralcoll
T
Centralcoll
TTCP
NddpNd
NddpNd
pR
]/[
]/[
)( 2
2
/
( )( )
( )
DAA T
D h T hAA T
R pR p
R p
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
D mesons quenching reducedRatio D/hadrons (or D/0) enhanced and sensitive to medium properties
Heavy Quarks and Quarkonia
Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett. B519 (2001) 199 [arXiv:hep-ph/0106202].
For Heavy Quarks with momenta < 20–30 GeV/c v << c
Gluon radiation is suppressed at angles “dead-cone” effect
Contributes to the harder fragmentation of heavy quarks and implies lower energy loss for heavy quarks relative to light quarks
0Qm
E
k
E
M
dP
k
dkkdCdP Fs
,
)/1()(
0
2220
022
022
22
Y. Dokshitzer et al, J Phys G 17, 1602 (1991)
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Heavy Flavor Production Yields (II)
arXive:hep-ph/0311048 v1 4 Nov. 2003
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Heavy Flavor Production Yields (III)
arXive:hep-ph/0311048 v1 4 Nov. 2003
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Charm pT Spectra
Power-law function with parameters dN/dy, <pT> and n to describe the D0 spectrum
D0 and e combined fit
Generate D0e decay kinematics according to the above parameters
Vary (dN/dy, <pT>, n) to get the min. 2 by comparing power-law to D0 data and the decayed e shape to e data
<pT>=1.20 0.05(stat.) GeV/c in minbias Au+Au
<pT>=1.32 0.08(stat.) GeV/c in d+Au
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Charm Total Cross Section
1.13 0.09(stat.) 0.42(sys.) mb in 200GeV minbias Au+Au collsions
1.4 0.2(stat.) 0.4(sys.) mb in 200GeV minbias d+Au collisions
Charm total cross section per NN interaction
Charm total cross section follows roughly Nbin scaling from d+Au to Au+Au considering errors
Indication of charm production in initial collisions
Systematic error too large !
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Charm and Non-photonic Electron Spectra
1.13 0.09(stat.) 0.42(sys.) mb in 200GeV minbias Au+Au collsions
Total charm Binary Scalingsuppression at high pT
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Charm Nuclear Modification Factor
STAR: Phys. Rev. Lett. 91 (2003) 172302
Suppressions!!
RAA suppression for single electron incentral Au+Au similar to charged hadrons at 1.5<pT<3.5 GeV/c
Heavy flavor production IS alsomodified by the hot and dense mediumin central Au+Au collisions at RHIC
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
electrons
K p d
electrons
hadrons
High pT Electron ID
dE/dx from TPC
SMD from EMC
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
hadrons electrons
High pT Electron ID
p/E from EMC
After all the cuts
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Does Charm Quark Flow Too ?
Reduce Experimental Uncertainties !!Suppression in RAA Non-zero azimuthal anisotropy v2 !
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
• J/ – Small: r ~ 0.2 fm
– Tightly bound: Eb ~ 640 MeV
HG
QGP Observed in
dileptons invariant mass spectrum
Other charmonia• ’ ~ 8%• ~ 32%
Color Screening
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
J/psi Suppression and Color Screening
cdissJ
cdissdiss
TT
TTT
)25.1(
1.1
/
'
QCD Color Screening: (T. Matsui and H. Satz, Phys. Lett. B178, 416 (1986))
A color charge in a color medium is screened similar to Debye screening in QED the melting of J/.
c c Charm quarks c-c may not bindInto J/ in high T QCD medium
The J/ yield may be increased due to charm quark coalescence at the final stage of hadronization (e.g., R.L. Thews, hep-ph/0302050)
Recent LQCD Calculation:
dirdirdirJJ SSSS '// 1.03.06.0
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
J/psi is suppressed in central Au+Au Collisions !
Factor ~ 3 the same as that at SPS
Satz: Only states are screened both at RHIC and SPS.
Alternative: Larger suppression in J/psi at RHIC due to higher gluon density, but recombination boosts the yield up !
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
J/ Suppression or NotNuclear Absorption of J/ important at low energy important (SPS) !
Both QCD color screening and charm quarkcoalescence are interesting, which oneis more important at RHIC?
At RHIC the J/ measurement requires highluminosity running!
Centrality and pT dependence important !
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
Collisions at high pCollisions at high pT T (pQCD)(pQCD)
)ˆˆˆ(),(
ˆˆˆ
),(),( 22
2/
2/3
3
utszDz
s
td
dxfxfdxdx
pd
dE hhc
h
cdab
bpbapaabcd
bah
h
At sufficiently large transverse momentum, let us consider the process:
p + p hadron + x
1) f(x,2) – parton structure function
2) ab->cd – pQCD calculable at large 2
3) D(zh,2) – Fragmentation functionTo produce heavy quark pairs, the CM energy must>2m
Oct. 15, 2005 ALICE-USA Collaboration Meeting, LBNL
~7.6M AuAu 200GeV Run IV P05ia production 0~80% Min. Bias. |Vz| < 30cm
Electrons can be separated from pions. But the dEdx resolution is worse than d+Au
Log10(dEdx/dEdxBichsel) distribution is Gaussian.
2 Gauss can not describe the shoulder shape well. Exponential + Gaussian fit is used at lower pT region. 3 Gaussian fit is used at higher pT region.
2/ndf = 65/46
0.3<pT<4.0 GeV/c
TOF electron measurements
|1/-1|<0.03
2/ndf = 67/70
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