Misura della produzione di heavy flavour nel barrel di ALICE

MCWS, Frascati, 24.10.2006 Andrea Dainese 1

Misura della produzione Misura della produzione di heavy flavour nel barrel di ALICEdi heavy flavour nel barrel di ALICE

Andrea DaineseAndrea DaineseINFN – LNLINFN – LNL

per la Collaborazione ALICEper la Collaborazione ALICE


LayoutMotivation for heavy-flavour measurements in pp at LHC & theoretical predictions for c and b production

Why ALICE is well-suited for these measurements

Strategies and expected performance for:

D0 K

B e + X

Summary


c and b production at the LHC:testing pQCD at s = 14 TeV

Important test of pQCD in a new energy domain (7sTEVATRON)remember the “15-years saga of b production at the Tevatron”*…

…and D production not yet fully reconciled

* M.Mangano

CDF, PRL91 (2003) 241804FONLL: Cacciari, Nason

Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033


pQCD predictions for the LHCCompare predictions by several different models (HERA-LHC Worksohp)

Good agreement between collinear fact.-based calculations: FO NLO (Mangano, Nason, Risolfi) and FONLL (Cacciari, Nason)

kt fact. CASCADE (Jung) higher at large pt

beautycharm

CERN/LHCC 2005-014hep-ph/0601164


Theoretical Uncertainties

MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.

Evaluation of theoretical uncertainties (HERA-LHC Workshop)

beautycharm

MRST2001 CTEQ6, CTEQ5, CTEQ4, :PDFs

0.0040.0002 2/5.0 GeV 0.55.4

0.110.002 2/5.0 GeV 8.13.1 ,

bRFb

cTRFc

m

mm

CERN/LHCC 2005-014hep-ph/0601164


ALICE baseline yieldsCross sections: NLO (MNR code)

mc=1.2 GeV, F=R=2mc; mb=4.75 GeV, F=R=mb

Yields: assuming ppinel = 70 mb at 14 TeV


increasing s

c and b production at the LHC:a probe of small-x gluons

Probe unexplored small-x region with HQs at low pt and/or forward y

down to x~10-4 with charm already at y=0

Eskola, Kolhinen, Vogt, PLB582 (2004) 157Gotsmann, Levin, Maor, Naftali, hep-ph/0504040

Cartoon

char

mbea

uty

Window on the rich phenomenology of high-density PDFs

gluon saturation / recombination effects

breakdown of factorization ?

Charm at low pt predicted to be sensitive:

DGLAP (coll. fact.) + GLRMQ (nonlinear terms): enhancement

BK approach (kt fact): suppression


The ALICE DetectorThe ALICE Detector

||| < 0.9, B = 0.5 T| < 0.9, B = 0.5 TTPC + silicon trackerTPC + silicon tracker,,ee, , , K, p identification, K, p identification

-4 < -4 < < -2.5 < -2.5muonsmuons

M.Monteno D.Stocco


ALICE heavy-flavour potential

ALICE combines electronic (||<0.9), muonic (-4<<-2.5), hadronic (||<0.9) channels

ALICE covers low-pt regionALICE covers central and forward regionsPrecise vertexing in the central region to identify D (c~ 100-300 m) and B (c~ 500 m) decays

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100

1 year pp 14 TeV @ nominal lumin.

pT

of

Q-h

ad

ron

[G

eV

]

of Q-hadron

ALICE(b)(c)

ALICE(c/b)

ATLAS/CMS(b) LHCb

(b)

-2 0 2 4 61

10

100

1 year pp 14 TeV @ nominal lumin.

pT

of

Q-h

ad

ron

[G

eV

]

of Q-hadron

ALICE(b)(c)

HERA-LHC WorkshopCERN/LHCC 2005-014hep-ph/0601164

A.Dainese (ALICE)M.Smizanska (ATLAS)

C.Weiser (CMS)U.Uwer (LHCb)


Heavy-flavour analyses

Hadronic decays:

D0K-+, D*+D0+, D+K-++, Ds+K+K0*/+…

Leptonic decays:

B e/ + X

Invariant mass analysis of lepton pairs: BB, DD, BDsame, J/, ’, family, B J/ + X

BB (J/ )

e- correlationsIn red, channels studied in the PPR Volume 2

CERN/LHCC 2005-030


PrimaryVertex B

e

Xd0

rec. track

Vertexing: track d0 resolution

< 60 m (r)for pt > 1 GeV/c

Resolution mainly provided by the 2 layers of silicon pixels

PIXEL CELL

z: 425 m

r: 50 m

Two layers:r = 4 cmr = 7 cm

9.8 M

INFN Padova/Legnaro


Effect of primary vertex uncertainty

Vertex position reconstructed event-by-event using tracks

More precise vertex pos. in (x,y) from mean over many eventsBeam spread at ALICE I.P. may be as large as 50-100 m

(ALICE LMAX ~ 1030 cm-2 s-1)

vertextrackrd )(0

vertex resolutioneffect on d0 resolution


Hadron ID: Time-of-flight

TOF

Pb-Pb, dNch/dy=6000

Optimization for hadronic charmdecays was studied:minimize probability to tag K as

K id. required for D0 pt < 2 GeV/c


Electron IDCombined info from TRD (trans. rad.) and TPC (dE/dx)

TRD rejects 99% of the and ALL heavier hadrons (pt > 1 GeV/c)

TPC further rejects residual pions (up to 99% at low p)

About 20% of electrons rejected

fraction of misidentified pions


D0 K-+ reconstruction

Main selection: displaced-vertex selection pair of opposite-charge tracks with large impact parameters

good pointing of reconstructed D0 momentum to the primary vertexincrease S/Bby factor ~103!


Invariant mass analysis

Example (extrapolated to expectation for 109 pp events):

0.5-1 GeV/c 3-4 GeV/c 12-14 GeV/c


D0 K-+: Results

inner bars: stat. errorsouter bars: stat. pt-dep. syst.not shown: 9% (Pb-Pb), 5% (pp, p-Pb) normalization errors

Down to pt ~ 0 in pp and p-Pb (1 GeV/c in Pb-Pb)

1 year at nominal luminosity(107 central Pb-Pb events,

109 pp events)+ 1 year with 1month of p-Pb running

(108 p-Pb events)


B e + X: Detection strategy

1) Electron PID: reject most of the hadrons

2) d0 cut: reduce charm and bkg electrons (Dalitz, conv.)

3) Subtract (small) residual background (ALICE data + MC)

PrimaryVertex B

e

Xd0

rec. track


Effect of electron identification

residual charm contribution subtracted using D0 measurement 3-5% syst. error


B e + X: Results

Using electrons in2 < pt < 20 GeV/c

obtain B meson2 < pt

min < 30 GeV/c

MC-based procedure à la UA1

inner bars: stat. errorsouter bars: stat. pt-dep. syst. errorsnot shown: 5% normalization error

1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)


pp, s = 14 TeVComparison to pQCD predictions

charm (D0 K) beauty (B e+X)

1 year at nominal luminosity(109 pp events)


Perspectives for the “1st month at 14 TeV”

Detector configuration:ITS + TPC + TOF

Expected statistical errors for a low-stats sample:Scaling of statistical errors according to Nevts

No dedicated cuts study yetD0 K

Detector configuration:ITS + TPC + TRD

B e + X

~1 month

1 year at nominal luminosity


SummaryCharm and beauty production study at the LHC:

test of QCD in a new energy domain at low pt: access to low-x gluon dynamics; saturation?

ALICE is well-equiped for heavy-flavour studies using several different channels / strategies acceptance down low pt at central and forward rapidity

small extrapolation for total cross section

With 109 events (nominal year): ~5% statistical error on total cross sections (c and b) statistical error < 20% up ~ 20-25 GeV/c


EXTRA SLIDES


LHC running conditions

Ldt = 5.1026 cm-2 s-1 x 106 s

5.1032 cm-2 PbPb run, 5.5 TeV

NPbPb collisions = 2 .109 collisions

Ldt dt = 3.1030 cm-2 s-1 x 107 s

5.1037 cm-2 for pp run, 14 TeV

Npp collisions = 2 .1012 collisions

Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: Bandwidth limitation NPbPb central = 2 .108 collisions

Muon triggers: ~ 100% efficiency, < 1kHz

Pb-PB nominal run pp nominal run

Electron triggers: ~ 50% efficiency of TRD L1 20 physics events per event

Hadron triggers: NPbPb central = 2 .107 collisions

Hadron triggers: Npp minb = 2 .109 collisions


Beauty via single and dimuons in central Pb-Pb collisions

Muons “identified” in the forward spectrometer (-4< <-2.5)15 interaction lengths, but..

muon pt threshold as low as 1-1.5 GeV/c

bb

single muons in the spectrometer:beauty dominates for pt > 2-3 GeV/c

bb y ~ 1 both muons in the acceptance


Di-muons invariant massSingle muon cut: pt > 2 GeV/c

Di-muon combinatorial bkgd subtracted with evt-mixing


Open Beauty with Muons: ResultsCombined fit of low-mass, high-mass dimuons and single muons with shapes from MC to extract muons from B

Use MC to exctract

down to ~1 GeV/c!

min tB pvs

systematic erroranalysis in progress

1 year at nominal luminosity(107 central Pb-Pb events)

Misura della produzione di heavy flavour nel barrel di ALICE

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