heavy flavour and quarkonium measurements with alice at lhc
DESCRIPTION
Heavy flavour and Quarkonium measurements with ALICE at LHC. Javier Castillo for the ALICE Collaboration. Outline. Physics motivations ALICE experiment ALICE capabilities Open heavy flavour Quarkonia First results from 7 TeV p-p collisions Conclusions Disclaimer: - PowerPoint PPT PresentationTRANSCRIPT
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Heavy flavour and Quarkonium measurements with ALICE at LHC
Javier Castillo for the
ALICE Collaboration
Rencontres QGP-France – Étretat – 22/09/2010
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Outline• Physics motivations• ALICE experiment• ALICE capabilities
– Open heavy flavour– Quarkonia• First results from 7 TeV p-p collisions• Conclusions
• Disclaimer:– Details in
• C. Geuna, 20/9/2010• L. Bianchi, 22/9/2010• X. Zhang, 22/9/2010• S-U. Ahn, 22/9/2010• B. Boyer, 22/9/2010
Rencontres QGP-France – Étretat – 22/09/2010
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Heavy flavours
• In Pb-Pb collisions: probe the properties of the medium– created in the hard initial collisions
• experience the whole collision history– possible comparison heavy quarks/light partons
• energy loss:
• In p-p collisions: – baseline for Pb-Pb– measure charm and beauty cross section– compare to pQCD predictions
Rencontres QGP-France – Étretat – 22/09/2010
medium density and size
dead cone effect (mass)
Casimir factor (colour charge)
tHpp
tHAA
collt
HAA dpdN
dpdNN
pR//1)( B
AADAAAA RRR
bcsdug EEEE ,,
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Heavy quarks with PHENIX @ RHIC
Rencontres QGP-France – Étretat – 22/09/2010
As a test of pQCD …
… or of heavy quark energy loss.
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Quarkonia, heavy ions and the QGP?
• A long lasting story…– 1986, Matsui and Satz: J/ψ
suppression as a QGP signature– NA38, NA50, NA60 at SPS– PHENIX, STAR at RHIC• … and many open
questions– similar suppression at RHIC
and at SPS– larger suppression at larger
rapidities– cold nuclear matter effect
(still) weakly constrained– statistical hadronization,
recombination?
… and then??
Rencontres QGP-France – Étretat – 22/09/2010
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J/ψ polarization
Rencontres QGP-France – Étretat – 22/09/2010
Helicity frame
λ>0 transverseλ<0 longitudinal
L. Levy @ ICHEP 2010
• no model explains cross section and polarization simultaneously
• many models on the market‣ Color Singlet Model: LO, NLO, NNLO‣ Color Octet Mechanism: NRQCD...
many more
Should help constrain production models
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CNM Effects
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NDSG σ = 0,1,2,3,4,…15
EPS08
σ = 0 mb
σ = 4 mb
R. Vogt private communication
arXiv:0912.4498
Ask Elena about this one!
High statistics data provides a strong test of CNM models
Bottom line:CNM could explain
the mid-forward rapidity difference
L. Levy @ ICHEP 2010
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ϒ @ RHIC
Rencontres QGP-France – Étretat – 22/09/2010
RdA = 0.78 ± 0.28(stat.) ± 0.20(sys.)
L. LevyD. Kikola @ ICHEP2010
Au+Au |y|< 0.35RAA < 0.64 at 90% CL for Upsilon at RHIC (PHENIX).
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More J/ψ mess
Rencontres QGP-France – Étretat – 22/09/2010
L. LevyD. Kikola @ ICHEP2010
Disagreement at high pT
No suppression at high pT
RAA(pT > 5 GeV/c) = 1.4 ± 0.4 ±
0.2
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The LHC and its features• Large energy step (RHIC
x30)– A QGP that will be
• hotter,• bigger,• longer lived,• earlier thermalized.
– Large hard probe production cross-sections
SPSPbPbCent
RHICAuAuCent
LHCpp
LHCpPb
LHCPbPb
Centcc 0.2 10 0.2 1 115bb - 0.05 0.007 0.03 5
SPS17 GeV
RHIC200 GeV
LHC5.5 TeV
initial T ~ 200 MeV ~ 300 MeV > 600 MeV
volume 103 fm3 104 fm3 105 fm3
lifetime < 2 fm/c 2-4 fm/c > 10 fm/c
Rencontres QGP-France – Étretat – 22/09/2010 At top energies
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ALICE• Central barrel (|η|<0.9) • Muon spectrometer (-4.0<η<-2.5)
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– Open heavy flavour• hadronic channel• semi-leptonic decays (e)
– Quarkonia• e+e-
– Tracking: ITS+TPC+TRD– PID: TPC+TRD+TOF– Secondary vertexing:
ITS
– Open heavy flavour• semi-leptonic
decays (µ) – Quarkonia
• µ+µ-
– Absorber– Tracking chambers– MUON Trigger
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Heavy flavour measurement potential
Rencontres QGP-France – Étretat – 22/09/2010
Comparison with pQCD Energy loss studies
Good discriminating
power!
MC
MC
MC
MC
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Muons from charm at forward rapidity
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• Unfold single muon pt and dimuon invariant mass spectra• No dca cuts use large statistics to constrain the fits
1 month at reduced luminosity (1030 cm-2s-1, 7 x 1010 pp events)
pp, single muon pt
pp, di-muon invariant mass
pp
2.5<h<4, pt > 3 GeV/c x ~ 10-5
MC
MC
MC
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Quarkonia in dielectron channel
J/ψ
Υ
J/ψ Υ
Mass resolution ~30 MeV/c2 ~90 MeV/c2
Signal/Noise 1.2 1.0
Counts (nominal PbPb year) 10% 120k 900
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Quarkonia in dimuon channel
mμμ (GeV/c2) mμμ (GeV/c2)
J/ψ Υ
Mass resolution ~70 MeV/c2 ~100 MeV/c2
Signal/Noise 0.3 2.5
Counts (nominal PbPb year) MB 680k 6000
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Quarkonia: what will be done
• The bread and butter of J/ψ– Production yields, cross-sections
• High statistics• From pT = 0 GeV/c
– Detailed “suppression” studies • With respect to
– Beauty– pp (RAA)
• As a function of– Centrality – Transverse momentum (0-20 GeV/c)– Rapidity (two domains)
– Precise pp measurement• 3.106 J/ψ in nominal pp run• Sensitivity to low x‐Bjorken
–probing gluon distribution atxBj= 2x10‐4 – 4x10‐6 ;
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Secondary J/ψ• χc: contribution ~30%– χcJ/ψ+γ
• J/ψ in dielectron channel• γ in γ-conversion
– feasible in pp collisions• ~7k χc but requires a trigger strategy which is under
study
• ψ’: contribution ~10%– challenging
• B mesons: contribution ~20%– BJ/ψ+X
• Non photonic electrons• à la CDF: simultaneous fit
– Invariant mass distribution– Pseudo proper decay time
– In muon arm • method using 3 muon events is under study
− tot J/ψ− J/ψ from B− bkg− sum
χc1
χc2
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MCMC
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• Polarization– Angular distribution of μ+ in the quarkonium
rest frame.
•
•
– Υ polarization• 1 nominal year for integrated studies• Several years for differentials
Quarkonia: what could be achieved• Upsilon measurements– Separation of family states is possible (100
MeV resolution)
– Good sensitivity to “suppression” scenarii• Suppression 1: TC = 270 MeV; TD/TC = 4.0 (1.4) for ϒ(ϒ’);• Suppression 2: TC = 190 MeV; TD/TC = 2.9 (1.1) for ϒ(ϒ’);
− No suppression− Suppression 1− Suppression 2
€
dσdcosθH
∝1+α cos2θH
€
α σT − 2σ Lσ T + 2σ L
⇒ 1 transverse 0 no polarization−1 longitudinal
⎧ ⎨ ⎪
⎩ ⎪
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MC
MC
See L. Bianchi @ 18h10See S.-U. Ahn @ 16h45
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First results from 7 TeV p-p collisions
• CINT1B: interaction trigger– at least one charged particle in 8 η units• CMUS1B: single-muon trigger:– forward muon in coincidence with
interaction trigger
Rencontres QGP-France – Étretat – 22/09/2010
Further background-event rejection is performed offline by selecting events which:1. have the correct event type (physics);2. trigger on bunch crossings;3. fulfill at least -one- of the three following
conditions:a) 2 fired chips in the SPD*b) 1 fired chip in the SPD* and a beam-beam
flag in either V0A or V0C**c) beam-beam flags on both sides V0A and
V0C**;4. are not flagged as beam-gas by either V0A
or V0C**.
* calculated offline from reconstructed clusters ** calculated offline from the V0 signals
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Particle Identification
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Complementary momentum coverage
ITSTPC
TOF
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Open heavy flavour: D0 mesons
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Observed differentially in pT
• up to pT=12 GeV/c• down to 1 GeV/c
Expected to cover 0.5 < pT <15 GeV/c with 109 events
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Open heavy flavour: other D mesons
Expected to cover 0.5 < pT <15 GeV/c with 109 events
Rencontres QGP-France – Étretat – 22/09/2010
Observed differentially in pT
• up to pT=12 GeV/c
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Open heavy flavour in the electron channel• Compute the inclusive cross section using electrons• For high pT, the contribution from charm and beauty
becomes dominant• Essential ingredient for the analysis: electron Identification
– For the moment: TPC + TOF– Hard work to add the TRD is going on!– EMCAL will also contribute
Rencontres QGP-France – Étretat – 22/09/2010
TPC signal after a 3σ electron selection from TOF signal
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Open heavy flavour from single muons• Trigger matching– Iron wall stop hadrons produced in the
absorbers• Distance of Closest Approach– Could be used to separate c and b signal
from π and K background (using simulations)
• π and K contribution– subtracted using Pythia simulations
normalized at low pT
• c and b contribution– dominates for pT>2 GeV/c
Rencontres QGP-France – Étretat – 22/09/2010
See X. Zhang @ 17h45
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Quarkonium measurements
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J/ψ in the di-electron channel• 110M p-p events at 7 TeV
– 1/3 of available statistics• Track reconstruction
– TPC + ITS• Electron identification (and pion
rejection) – TPC – TRD could be included later• Fit with a Cristal Ball function• |η|<0.9
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J/ψ in the di-muon channel
• The alignment of the tracking chambers is a critical step for the J/ψ measurements– First alignment: straight tracks
from B=0 T data
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σJ/ψ (MeV)Without
alignment 230
First alignment 90Target 70
Saw C. Geuna @ 20/9/10 ?
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Transverse momentum dependence
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The width of the J/ψ peak is well reproduced by our Monte Carlo including residual misalignment and other realistic conditions! See B. Boyer @ 16h20
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Transverse momentum distribution
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To extract <pT2> we use the fit function first
proposed by Yoh et al., PRL 41 (1978) 684 and also used by previous experiments
• Quoted uncertainties include systematics from the fit function
• Full systematic uncertainties are being evaluated
See B. Boyer @ 16h20
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Conclusion• The LHC provides a new and promising environment for
the study of open heavy flavour and quarkonium production• ALICE is well suited for the study of heavy flavours
– Two rapidity domains
• Exciting results from first pp data at 7 TeV– J/psi transverse momentum distribution
• Coming soon– J/ψ differential cross-section– Corrected open heavy flavour measurements
• Looking forward for Pb-Pb data et the end of the year
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Back-Up
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The LHC and its other “features”• Only 1 month per year for the heavy ion program
– Including pA or lighter ions• Lead beam luminosity is limited by the magnets “quench
limit” due to EM processes induced by PbPb collisions;• Large contribution from B-hadron decays to charmonia
yields – ~20% for J/ψ• Cold nuclear matter effects are not well under control
– Could try different normalizations– Will be measured with pA runs
• Heavy Ion running plan (1 month per year)– First 5 years: 1 PbPb low luminosity, 2 PbPb runs at nominal
luminosity, 1 pPb and 1 lighter ion runs– Next 5 years (based on results): lower energies, pp at 5.5 TeV, other
AA or pA, more stat …
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D+ Invariant Mass Spectra in pT bins
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D* Invariant Mass Spectra in pT bins
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Monte Carlo comparison
• “CDF pp 7TeV” parameterization – pT extrapolated from CDF results– y obtained from CEM calculations– No polarization ( = 0)
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The acceptance and efficiency corrected distributions are compared to generated MC distribution
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ALICE performances in μ+μ-
State S[103] S/B S/(S+B)1/2
J/Y 200 0.49 250Y’ 5.5 0.03 13
(1S) 2.0 3.6 39
(2S) 0.52 1.4 18
(3S) 0.28 0.95 12
State S[103] S/B S/(S+B)1/2
J/Y 130 0.20 150Y’ 3.7 0.01 6.7
(1S) 1.3 1.7 29
(2S) 0.35 0.68 13
(3S) 0.20 0.48 8.1
State S[103] S/B S/(S+B)1/2
J/Y 22 3.14 130Y’ 0.6 0.18 9.7
(1S) 0.21 9.5 15
(2S) 0.06 3.6 6.5
(3S) 0.03 1.9 4.2
0<b<3 fm
6<b<9 fm b>12 fm
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