Open-charm and J/ production at the ALICE...

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


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

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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.

, ,


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


TOF

Signals: D0K-

108 events 1-12 GeV in 7 bins


Signals: D+K-108 t 2 12 G V i 6 bi108 events; 2-12 GeV in 6 bins


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


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


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


D*+ dN/dpt and D ratios


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!


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


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


(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)


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

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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)

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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

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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

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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

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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:

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• 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

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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

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• 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

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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

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• Higher occupancy with respect to Pb-Pb• Re-tuning of reconstruction parameters

First J/ signal from Pb-Pb collisions

3

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• 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


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


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

31Purdue University, Jan. 6, 2011 Pietro Cortese 31

“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

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minimum bias triggers


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


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


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+:


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


D0 and D+ dN/dpt

Only statistical errors Shape compares well with pQCD (FONLL)


Shape compares well with pQCD (FONLL)

D mesons: from signals to cross sections sect o s

ddpt |y|0.5

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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


J/ψ backup slides


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 %

Open-charm and J/ production at the ALICE...

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