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Open-charm and J/ψ production at the ALICE experiment
Pietro CorteseUniversità del Piemonte Orientale and INFN Alessandria, Italy
b h lf f th ALICE C ll b tion behalf of the ALICE Collaboration
11Purdue University, Jan. 6, 2011 Pietro Cortese
Outline
Open-charm in p-p collisions D meson reconstruction in ALICE central barrel D0 and D+ production measurement Single muons and single electrons
J/ψ in p-p Fi t lt J/ + d J/ + i lli i t 7 T V First results: J/+- and J/e+e- in p-p collisions at 7 TeV
Perspectives for Pb-PbPerspectives for Pb-Pb
2Purdue University, Jan. 6, 2011 Pietro Cortese
The ALICE experimentALICE i th d di t d h i i t t th LHC• ALICE is the dedicated heavy-ion experiment at the LHC
lli i
Pb-Pb collisions: main focus of the experimentQGP studies
p-p collisions: important aspect of the physics programreference for heavy-ion collision studiesp-p physics
Central barrel (||<0.9)
Muon spectrometer (-4<<-2.5)
Tracking: ITS,TPC,TRD Tracking: 10 CPC planesTrigger: 4 RPC planesg , ,
PID: ITS,TPC,TRD,TOF,EMCAL,PHOS
Trigger: ITS, TOF, TRD…
Trigger: 4 RPC planes
Event characterization:V0 T0 FMD ZDC
3
V0, T0, FMD, ZDC
Charm in pp at LHC Important test of pQCD in a new energy domain (3 5 s ) Important test of pQCD in a new energy domain (3.5 sTEVATRON)
c production on the upper edge of prediction, at Tevatron and RHIC Ultimately, ALICE aims at measuring charm production below pT~1 GeV/c
P b l PDF d t Bj k 10 4 Probe gluon PDF down to xBjorken ~ 10-4
Does the factorization approach still hold? Gluon saturation?
Reference for heavy quark quenching studies in Pb-Pb
PHENIX, STAR, 0.2 TeV, c,b e+XCDF, 1.96 TeV, D*
CDF, PRL91 (2003) 241804FONLL: Cacciari, NasonGM-VFNS: Knihel et al.
, ,
4Purdue University, Jan. 6, 2011 Pietro Cortese
D meson reconstruction in ALICE Main selection: displaced vertex topology Main selection: displaced-vertex topology Example: D0K-+
good pointing of reconstructed D momentum to the primary vertex pair of opposite-charge tracks with large impact parameters
K ID in TPC+TOF helps in rejecting background at low pt
TPC
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TOF
Signals: D0K-
108 events 1-12 GeV in 7 bins
6Purdue University, Jan. 6, 2011 Pietro Cortese
Signals: D+K-108 t 2 12 G V i 6 bi108 events; 2-12 GeV in 6 bins
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Corrections for D cross sections C ti 1) ffi i Corrections: 1) efficiency 1% 10% from low to
high pt
D0 D+
factor 2 larger for B feed-down D mesons
Corrections: 2) feed-down BD: ~20-25%BD: 20-25% for now, subtract using FONLL
BD predictions FONLL describes well B FONLL describes well B
production at Tev and LHC with full 2010 statistics will be
corrected based on data (D
8Purdue University, Jan. 6, 2011 Pietro Cortese
corrected based on data (D displacement to vertex, à la CDF)
D0 and D+ d/dpt, |y|<0.5, pp 7 TeV
2 < pt < 10 GeV/c, with 1.4 nb-1 (~20% of 2010 statistics) Total systematic error 20 40% p dep + 10% on normalization
9Purdue University, Jan. 6, 2011 Pietro Cortese
Total systematic error 20-40% pt-dep. + 10% on normalization pQCD predictions (FONLL and GM-VFNS) compatible with our data
Coming soon: D*+
D*+D0 +D*+D0+
2-12 GeV/c
Soft pion reconstruction down to 100 MeV/c using ITS
t d l t kas standalone tracker Evaluation of
systematics ongoing
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D*+ dN/dpt and D ratios
11Purdue University, Jan. 6, 2011 Pietro Cortese
ee, H1, ZEUS: JHEP07 (2007) 074CDF: PRL 91 (2003) 241804
Only statistical errors Shape compares well with pQCD (FONLL)
Other ongoing analyses:D0K + + D0K-+ below 1 GeV/cD0K-+-+ D0K + below 1 GeV/c
D +K-K+ + c+pK-+
Ds+K-K++ c
(c= 60 m)
/K/p ID pcrucial here!
12Purdue University, Jan. 6, 2011 Pietro Cortese
Heavy flavour in the muon spectrometer
In p-p collisions charm and beauty decays are themain source of single
ith >2
Monte-Carlo
muons with pT>2 GeV/c in -4<η<-2.5
Analysis chain:• Remove beam-gas (global event selection) • Remove punch-through hadrons and low-pT secondary µ p g pT y µ
→ muon trigger• Remove background decay µ
→ models and MC (present), exploit correlation with vertex displacement
13Purdue University, Jan. 6, 2011 Pietro Cortese
displacement• Correct for acceptance/efficiency• Estimate the cross-section
Single muons from HF decays
Conservative systematics
• pQCD calculations are in agreement with data within the systematic errorsy• the shape of the distribution is well reproduced• Analysis on the full statistics will improve the pT reach• data-driven methods will improve the background subtraction
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(expecially important at low-pT)
Coming soon: electrons from HF decays
After TOF cut
Electron ID with TOF time and TPC dE/dx cut (TRD and EMCAL will join soon)
Contamination from <1% to 15% at 4 GeV/cContamination from <1% to 15% at 4 GeV/c
Inclusive electron spectrum compared with cocktail of sources (conversion electrons from π0 decays are derived from data)
1515Purdue University, Jan. 6, 2011 Pietro Cortese
from π decays are derived from data)
HF signal above the electron cocktail
Quarkonium measurement in ALICEQ k i i ALICE b d i t• Quarkonium in ALICE can be measured in two ways:
• in the central barrel in the e+e- channel (|y|<0.9)• in the forward spectrometer in the +- channel (2.5<y<4)p ( y )
• 3 sources of J/1) Direct production1) Direct production2) Feed down from heavier
cc statesPrompt J/
b id tifi d i th t l b l
radiative decay cJ/in the central barrel
3) J/ from b-hadron decay can be identified in the central barrel, good impact parameter resolution (r < 60 m for pT>1 GeV/c)
forward detection more difficult 3-muon events B cross section from single- Semileptonic decays of B pairs
16
Preliminary ALICE results refer to inclusive J/ production
p y p
J/ +- : p+p @ √s=7 TeV sample• Data sample:
• Integrated luminosity = 13.6 nb-1, corresponding to data collected between May and July 2010 (~ 10-15% of the 2010 t t l t ti ti )total statistics)
• Trigger: muon in the forward spectrometer, in coincidence with minimum bias interaction trigger
R S l ti• Run Selection:• Runs selected according to quality checks on the stability of the muon spectrometer tracking and trigger performances
• Event Selection:• at least one vertex reconstructed in the silicon pixel detector• at least one muon reconstructed in the tracking and trigger
chambers satisfying the trigger algorithm• cut on the track position at the end of the front absorber (20<abs<90)
17
rapidity window: 2.5<y<4transverse momentum window 0<pT<8 GeV/c (statistics)
J/ +- : signal extraction• The number of J/ is extracted from a fit to the invariant mass spectrum, using
Crystal Ball shape for the signal (J/ and ’)
S f t ti lSum of two exponentialsfor the background
The available J/ statistics, used for the cross sectionused for the cross section
determination is
NJ/ = 1909 ± 78
18
J/
S/B (2.9<M<3.3) ~ 2.4 With a suitable pT cut (smaller background),also the (2S) signal is visible, but with a much lower statistical significance
J/ +- : acceptance efficiencyInputs:Inputs:• realistic y and pT J/ distributions
• detector status and efficiency
pT CDF extrapolationy CEM calculation
• Study of differential distributions: 1D acceptance correction• Main source of uncertainty: unknown J/ψ polarization
G dGood coverage down to pT =0!
Polarization in Helicityreference frame
19
J/ e+e- : p+p @ √s=7 TeV sampleand signal extractionand signal extraction
• Analysis is based, for the moment, on a smaller data sample wrt to J/+-
Track selection:| + | 0 88 d | J/ | 0 88
p L=4.0 nb-1 (~15% of 2010 stat.)
|e+,e-|<0.88 and |yJ/|<0.88 pT
e+,e- > 1 GeV/c
TPC-based PID
NJ/ = 123 15NJ/ 123 15
20
Integrated cross section(s)• The ALICE results, integrated pT, are:J/ψ(-0.88<y<0.88)=12.952.15(stat)2.32(syst)+1.26
-2.55(syst. pol) μb
J/ψ(2.5<y<4)=7.250.29(stat)0.98(syst)+0.87-1.50(syst. pol) μb
V d t ith th di LHCb lt
(polarization-related errors calculated in the helicity frame)
Very good agreement with the corresponding LHCb result obtained at forward rapidity (ICHEP2010)
Main sources of systematic errors are:• Unknown polarization• Luminosity determinationy• In the dielectron channel:
• track quality cuts and PID• In the dimuon channel:
21
• In the dimuon channel: • signal extraction and trigger efficiency
Differential cross section: dJ//dpT (2.5<y<4)
(ICHEP 2010)(ICHEP 2010)
(stat errors only)
• Very good agreement with the LHCb result in the same rapidity range
22
y g g p y g• Other sources of point to point systematic errors (signal extraction, acceptance input) vary between 3 and 10% (not yet fully evaluated)
Differential cross section: dJ//dy (pT>0)
ALICE can meas re the distrib tion of the incl si e J/ prod ction in a
23
• ALICE can measure the distribution of the inclusive J/ production in a wide rapidity range• coverage reaches zero pT at both central and forward rapidities
Preliminary comparison(s)
• Model calculations:• R.Vogt, Phys. Rev. C 81 (2010) 044903• J.P. Lansberg, arXiv:1006.2750
24
g,• CMS: pT-integrated cross section 1.6<y<2.4 from (arXiv:1011.4193)• ATLAS: d/dy 1.5<y<2.25, ATLAS-CONF-2010-062• LHCb: d/dy 2.5<y<4 from LHCb-CONF-2010-010
√s-dependence of inclusive J/
25
• NLO calculation for cc by Mangano et al., normalized to the CDF point• Same √s-dependence for the inclusive J/ cross section
November 2010:moving from p-p to Pb-Pbmoving from p-p to Pb-Pb
26
• Higher occupancy with respect to Pb-Pb• Re-tuning of reconstruction parameters
First J/ signal from Pb-Pb collisions
3
27
• Expected final statistics for Pb run O(103)• Extract RAA in (some) centrality bins
Prospects for Pb-PbDetectorDetectorperfoms
well!
~ 45 M Pb-Pb inelastic events on tape (~6 b-1)
~ 4 5 M in 0 10% most central ~ 4.5 M in 0-10% most central
28Purdue University, Jan. 6, 2011 Pietro Cortese
Summary on Open-Charm D0 and D+ meson cross section at mid-y
measured in 2-10 GeV/c pQCD predictions agree with data
Ongoing: increase statistics increase statistics
o extend to lower and higher pt
B-feed-down from data ill ll t d t ti will allow to reduce systematics
Coming soon: D*+
D*+ , other D0 channel, Ds, cs c
Single electrons
Will f f Pb Pb di
29Purdue University, Jan. 6, 2011 Pietro Cortese
Will serve as a reference for Pb-Pb studies
On QuarkoniaALICE has measured inclusive J/ production
Over a wide rapidity range (-0.88<y<0.88, 2.5<y<4)
With good coverage down to pT=0
Next steps, in the dimuon channel, with higher statistics:Extend the analysis to (2S) and to bottomonium states
Integrated and differential J/ polarization study
Pb Pb l t dPb-Pb run completedJ/ signal observed
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Next step: nuclear modification factor vs centrality
D backup slides
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“Mi i bi ” b d i t ti t i
Trigger & Data sample, pp 7 TeV “Minimum bias”, based on interaction trigger: SPD or V0-A or V0-C
o at least one charged particle in 8 units% fo ~95% of inel
read out all ALICE single-muon trigger: forward muon in coincidence with Min Bias read out MUON, SPD, V0, FMD, ZDC
Both activated in coincidence with the BPTX
beam pickups Since March 31st 2010, collected ~8.5×108 minimum bias triggers 8.5 10 minimum bias triggers ~1.3×108 muon triggers
Results presented today based on ~108
minimum bias triggers
32
minimum bias triggers
32Purdue University, Jan. 6, 2011 Pietro Cortese 32
D0 K
Charm reconstruction in the ALICE barrel, |Charm reconstruction in the ALICE barrel, ||<0.9|<0.9
TOF (PID)
D0 KD+ KD* D0
TPC (tracking, PID dE/dx)
K Ds KKD0 Kc KpTPC (tracking, PID dE/dx)
ITS (tracking & vertexing)
c Kp
33Purdue University, Jan. 6, 2011 Pietro Cortese
D meson reconstruction in ALICEM i l ti di l d t t l Main selection: displaced-vertex topology
Tracking and vertexing precision is crucial here Inner Tracking System (ITS) was aligned using Inner Tracking System (ITS) was aligned using
cosmics and collisions current resolution for pixels: 14 m (nominal: ≈11 m) r impact parameter resolution of 75 m at 1 GeV/c The inner pixel layer r impact parameter resolution of 75 m at 1 GeV/c particle-mass dependence well understood
protonkaonpion
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From signals to cross sections C ti 1) ffi i 2) f d d BD Corrections: 1) efficiency 2) feed-down BD then, normalization to cross section, using MB from VdM scan
Detector response well described in MC Detector response well described in MC
D0:
massresolution
cutvariables
D+:
35Purdue University, Jan. 6, 2011 Pietro Cortese
FONLL vs. data, beauty production 2-7 TeVCDF, B CMS, arXiv:1011.4193
FONLL, MC@NLO:C i i F i i M NCacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033
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D0 and D+ dN/dpt
Only statistical errors Shape compares well with pQCD (FONLL)
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Shape compares well with pQCD (FONLL)
D mesons: from signals to cross sections sect o s
ddpt |y|0.5
12
1y(pt )
1
B.R.
1 c
fc (pt )Nraw
D (pt ) |y|y( pt )
pt
(CINT1B /V 0AND )NCINT1B
V 0AND
Corrections: feed-down BD: ~15-20% main method (“Nb-subtraction”): FONLL input is only the DfromB cross section
fc (pt ) NrawD (pt ) | | ( )
NrawD (pt ) | | ( )
NFONLLDfromB (pt ) | | ( )
where: second method (“prompt fraction fc”): FONLL input is the ratio of prompt to
fc (pt ) raw (pt ) |y|y( pt ) raw (pt ) |y|y( pt ) FONLL (pt ) |y|y( pt )
NFONLLDfromB (pt ) |y|y( pt )
FONLLDfromB (pt) DfromB ypt 2 BRL int
total D meson cross sections use the total envelope of the
error bands (from FONLL) of two methods as a systematic error
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J/ψ backup slides
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J/ e+e- : acceptance efficiency
y
effic
ienc
ccep
tanc
e
Ac
• Also in the electron channel very good coverage down to p = 0
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• Also in the electron channel, very good coverage down to pT = 0
Systematic errorsSource of systematic error
Uncertainty on signal extraction 7.5 %
pT and y shapes in the MC 2%
Muons
pT y p
Trigger efficiency 4%
Tracking efficiency 2%
polarization =-1 =1
Helicity -21% +12%
Normalization 10 %
Total systematic error 13.5 %
Collins-Soper -31% +15%
Source of systematic error
Kinematics <1%
Track quality #clusters TPC 10%
Electrons
polarization =-1 =1Track quality,#clusters TPC 10%
PID cuts 10%
Signal extraction range 4%
polarization =-1 =1
Helicity -20% +10%
Collins-Soper -25% +12%
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Normalization 10 %
Total systematic error 18 %
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