Some Aspects of Heavy Flavor Physics in ALICE: the

1
Some Aspects of Heavy Flavor Physics in ALICE
the Other Hard Probe

• V. Ghazikhanian
• UCLA

2
Heavy Quark Production Mechanism
K
e-/?-
e-/?-
e/?
J/y
K-
e/?
?l
D0

• Sensitive to initial gluon density and gluon
  distribution

• Sensitive to initial gluon density and gluon
  distribution

• Energy loss when propagating through dense medium

• Suppression/enhancement
• of charmonium in the medium is a critical
  signal for QGP.

• Different scaling properties in central and
  forward region indicate shadowing, which can be
  due to CGC.

to these one needs to add photoproduction
mechanism (see Spencers presentation)
3
Parton Distribution Function
A. Dainese, PhD. Thesis arXivenucl-ex/0311004
4
Parton Energy Loss

• Due to medium-induced gluon radiation
• Average energy loss (BDMPS model)

Casimir coupling factor 4/3 for quarks 3 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.
5
ALICE Heavy Flavor Acceptance
arXivehep-ph/0311048 v1 4 Nov. 2003
6
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

7
Open Charm Production At LHC/ALICE
A. Dainese, PhD. Thesis arXivenucl-ex/0311004
8
Detecting D-Mesons via Hadronic Decays

• Hadronic Channels
• D0 ? K ? (B.R. 3.8)
• D0 ? K p r (B.R. 6.2 ? 100 (r?pp-) 6.2)
• D? ? K ? p (B.R. 9.1)
• D ? D0p (B.R. 68 ? 3.8 (D0 ? K ? ) 2.6 )
• Lc ? p K p (B.R. 5)

Huan Huang
9
Detection strategy for D0 ? K- p

• 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

A. Dainese, PhD. Thesis arXivenucl-ex/0311004
10
Hadronic charm
Combine ALICE tracking secondary vertex finding
capabilities (sd060mm_at_1GeV/c pT) large
acceptance PID to detect processes as D0?K-?
1 in acceptance
/ central event 0.001/central
event accepted after rec. and all cuts
Results for 107 PbPb ev. ( 1/2 a run)
significance vs pT
S/?BS 37
S/?BS 8 for 1ltpTlt2 GeV/c (12 if K ID required)
11
Initial Signal Significance
A. Dainese, PhD. Thesis arXivenucl-ex/0311004
12
D0 Cross section measurement
13
D quenching (D0 ?K-p )
Ratio D/hadrons (or D/p0) enhanced and sensitive
to medium properties
14
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 !
15
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
• g conversions (p0 ? gg)
• p0, h Dalitz decays
• r, f, decays (small)
• Ke3 decays (small)

16
c/b Quarkonia

• 1 month statistics of PbPb vsNN5.5 TeV

arXivehep-ph/0311048 v1 4 Nov. 2003
17
Heavy Flavor Production Yields (I)
Peter J.
18
Hadron and Lepton Identification
ALICE PPR CERN/LHCC 2003-049
19
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 -gt mu c -gt 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
  TRDEMCTOFITS.

20
The End
21
Nuclear Modification Factors
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 !
22
Heavy Quarks and Quarkonia

• For Heavy Quarks with momenta lt 2030 GeV/c ?
  v ltlt 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

D mesons quenching reduced Ratio D/hadrons (or
D/p0) enhanced and sensitive to medium
properties
Yu.L.Dokshitzer and D.E.Kharzeev, Phys. Lett.
B519 (2001) 199 arXivhep-ph/0106202.
23
Heavy Flavor Production Yields (II)
arXivehep-ph/0311048 v1 4 Nov. 2003
24
Heavy Flavor Production Yields (III)
arXivehep-ph/0311048 v1 4 Nov. 2003
25
Charm pT Spectra
D0 and e? combined fit
Power-law function with parameters dN/dy, ltpTgt
and n to describe the D0 spectrum
Generate D0?e? decay kinematics according to the
above parameters
Vary (dN/dy, ltpTgt, n) to get the min. ?2 by
comparing power-law to D0 data and the decayed
e? shape to e? data
ltpTgt1.20 ? 0.05(stat.) GeV/c in minbias AuAu
ltpTgt1.32 ? 0.08(stat.) GeV/c in dAu
26
Charm Total Cross Section
Charm total cross section per NN interaction
1.13 ? 0.09(stat.) ? 0.42(sys.) mb in 200GeV
minbias AuAu collsions
1.4 ? 0.2(stat.) ? 0.4(sys.) mb in 200GeV
minbias dAu collisions
Charm total cross section follows roughly Nbin
scaling from dAu to AuAu considering errors
Indication of charm production in initial
collisions
Systematic error too large !
27
Charm and Non-photonic Electron Spectra
1.13 ? 0.09(stat.) ? 0.42(sys.) mb in 200GeV
minbias AuAu collsions Total charm ? Binary
Scaling suppression at high pT
28
Charm Nuclear Modification Factor
RAA suppression for single electron in central
AuAu similar to charged hadrons at 1.5ltpTlt3.5
GeV/c
Heavy flavor production IS also modified by the
hot and dense medium in central AuAu collisions
at RHIC
Suppressions!!
STAR Phys. Rev. Lett. 91 (2003) 172302
29
High pT Electron ID
dE/dx from TPC
SMD from EMC
30
High pT Electron ID
p/E from EMC
After all the cuts
31
STAR non-photonic electrons from EMC
32
Does Charm Quark Flow Too ?
Reduce Experimental Uncertainties
!! Suppression in RAA ? Non-zero azimuthal
anisotropy v2 !
33
Color Screening

• J/?
• Small r 0.2 fm
• Tightly bound Eb 640 MeV

QGP

• Observed in dileptons invariant mass spectrum
• Other charmonia
• ? 8
• ? 32

34
J/psi Suppression and Color Screening
Recent LQCD Calculation
35
J/y Quark Potential Model
36
Lattice QCD Calculations
37
J/psi is suppressed in central AuAu Collisions !
Factor 3 the same as that at SPS Satz Only c
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 !
38
J/y Suppression or Not
Nuclear Absorption of J/y important at low
energy important (SPS) ! Both QCD color
screening and charm quark coalescence are
interesting, which one is more important at
RHIC? At RHIC the J/y measurement requires
high luminosity running! Centrality and pT
dependence important !
39
Collisions at high pT (pQCD)
At sufficiently large transverse momentum, let us
consider the process p
p ? hadron x
1) f(x,m2) parton structure function 2)
sab-gtcd pQCD calculable at large m2 3)
D(zh,m2) Fragmentation function
To produce heavy quark pairs, the CM energy
mustgt2m
40
TOF electron measurements
7.6M AuAu 200GeV Run IV P05ia production 080 Min. Bias. Vz lt 30cm
?2/ndf 65/46
?2/ndf 67/70
Electrons can be separated from pions. But the
dEdx resolution is worse than dAu Log10(dEdx/dEdx
Bichsel) distribution is Gaussian.
0.3ltpTlt4.0 GeV/c
1/?-1lt0.03

• ? 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.