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Misura della produzione di heavy flavour nel barrel di ALICE. Andrea Dainese INFN – LNL per la Collaborazione ALICE. Layout. Motivation for heavy-flavour measurements in pp at LHC & theoretical predictions for c and b production Why ALICE is well-suited for these measurements

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Misura della produzione di heavy flavour nel barrel di ALICE


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misura della produzione di heavy flavour nel barrel di alice

Misura della produzione di heavy flavour nel barrel di ALICE

Andrea Dainese

INFN – LNL

per la Collaborazione ALICE

MCWS, Frascati, 24.10.2006 Andrea Dainese

layout
Layout
  • Motivation 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-p+
    • B  e + X
  • Summary

MCWS, Frascati, 24.10.2006 Andrea Dainese

c and b production at the lhc testing pqcd at s 14 tev
c and b production at the LHC:testing pQCD at s = 14 TeV
  • Important test of pQCD in a new energy domain (7sTEVATRON)
    • remember the “15-years saga of b production at the Tevatron”*…
    • …and D production not yet fully reconciled 

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

CDF, PRL91 (2003) 241804

FONLL: Cacciari, Nason

* M.Mangano

MCWS, Frascati, 24.10.2006 Andrea Dainese

pqcd predictions for the lhc
pQCD predictions for the LHC

Compare predictions by several different models (HERA-LHC Worksohp)

CERN/LHCC 2005-014

hep-ph/0601164

charm

beauty

Good agreement between collinear fact.-based calculations:

FO NLO (Mangano, Nason, Risolfi) and FONLL (Cacciari, Nason)

kt fact. CASCADE (Jung) higher at large pt

MCWS, Frascati, 24.10.2006 Andrea Dainese

theoretical uncertainties
Theoretical Uncertainties

Evaluation of theoretical uncertainties (HERA-LHC Workshop)

CERN/LHCC 2005-014

hep-ph/0601164

charm

beauty

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

MCWS, Frascati, 24.10.2006 Andrea Dainese

alice baseline yields
ALICE baseline yields
  • Cross sections: NLO (MNR code)
    • mc=1.2 GeV, mF=mR=2mc; mb=4.75 GeV, mF=mR=mb
  • Yields: assuming sppinel = 70 mb at 14 TeV

MCWS, Frascati, 24.10.2006 Andrea Dainese

c and b production at the lhc a probe of small x gluons

increasing s

charm

beauty

Cartoon

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
  • 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

Eskola, Kolhinen, Vogt, PLB582 (2004) 157

Gotsmann, Levin, Maor, Naftali, hep-ph/0504040

MCWS, Frascati, 24.10.2006 Andrea Dainese

the alice detector
The ALICE Detector
  • M.Monteno
  • D.Stocco

|h| < 0.9, B = 0.5 T

TPC + silicon tracker

g,e, p, K, p identification

-4 < h < -2.5

muons

MCWS, Frascati, 24.10.2006 Andrea Dainese

alice heavy flavour potential
ALICE heavy-flavour potential

HERA-LHC Workshop

CERN/LHCC 2005-014

hep-ph/0601164

  • ALICE combines electronic (|h|<0.9), muonic (-4<h<-2.5), hadronic (|h|<0.9) channels
  • ALICE covers low-pt region
  • ALICE covers central and forward regions
  • Precise vertexing in the central region to identify D (ct ~ 100-300 mm) and B (ct ~ 500 mm) decays

A.Dainese (ALICE)

M.Smizanska (ATLAS)

C.Weiser (CMS)

U.Uwer (LHCb)

MCWS, Frascati, 24.10.2006 Andrea Dainese

heavy flavour analyses
Heavy-flavour analyses
  • Hadronic decays:
    • D0K-p+, D*+D0p+, D+K-p+p+, Ds+K+K0*/fp+…
  • Leptonic decays:
    • B e/m + X
    • Invariant mass analysis of lepton pairs: BB, DD, BDsame, J/y, y’,  family, B J/Y + X
    • BB m m m (J/ym)
    • e-m correlations

In red, channels studied in the

PPR Volume 2

CERN/LHCC 2005-030

MCWS, Frascati, 24.10.2006 Andrea Dainese

vertexing track d 0 resolution

rf: 50 mm

rec. track

e

z: 425 mm

Primary

Vertex

PIXEL CELL

B

< 60 mm (rf)

for pt > 1 GeV/c

d0

X

Two layers:

r = 4 cm

r = 7 cm

INFN Padova/Legnaro

Vertexing: track d0 resolution

Resolution mainly provided by the 2 layers of silicon pixels

 9.8 M

MCWS, Frascati, 24.10.2006 Andrea Dainese

slide12

Effect of primary vertex uncertainty

  • Vertex position reconstructed event-by-event using tracks
  • More precise vertex pos. in (x,y) from mean over many events
    • Beam spread at ALICE I.P. may be as large as 50-100 mm

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

effect on d0 resolution

vertex resolution

MCWS, Frascati, 24.10.2006 Andrea Dainese

slide13

Hadron ID: Time-of-flight

TOF

Pb-Pb, dNch/dy=6000

Optimization for hadronic charm

decays was studied:

minimize probability to tag K as p

K id. required for D0pt < 2 GeV/c

MCWS, Frascati, 24.10.2006 Andrea Dainese

electron id

fraction of misidentified pions

Electron ID
  • Combined info from TRD (trans. rad.) and TPC (dE/dx)
    • TRD rejects 99% of the p and ALL heavier hadrons (pt > 1 GeV/c)
    • TPC further rejects residual pions (up to 99% at low p)
    • About 20% of electrons rejected

MCWS, Frascati, 24.10.2006 Andrea Dainese

slide15

increase S/B

by factor ~103!

D0 K-p+ reconstruction

  • Main selection: displaced-vertex selection
    • pair of opposite-charge tracks with large impact parameters
    • good pointing of reconstructed D0 momentum to the primary vertex

MCWS, Frascati, 24.10.2006 Andrea Dainese

invariant mass analysis
Invariant mass analysis
  • Example (extrapolated to expectation for 109 pp events):

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

MCWS, Frascati, 24.10.2006 Andrea Dainese

slide17

inner bars: stat. errors

outer bars: stat.  pt-dep. syst.

not shown: 9% (Pb-Pb), 5% (pp, p-Pb)

normalization errors

D0 K-p+: Results

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)

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

MCWS, Frascati, 24.10.2006 Andrea Dainese

b e x detection strategy

rec. track

e

Primary

Vertex

B

d0

X

B  e + X: Detection strategy
  • Electron PID: reject most of the hadrons
  • d0 cut: reduce charm and bkg electrons (Dalitz, g conv.)
  • Subtract (small) residual background (ALICE data + MC)

MCWS, Frascati, 24.10.2006 Andrea Dainese

effect of electron identification
Effect of electron identification

residual charm contribution subtracted using D0 measurement

 3-5% syst. error

MCWS, Frascati, 24.10.2006 Andrea Dainese

b e x results

inner bars: stat. errors

outer bars: stat.  pt-dep. syst. errors

not shown: 5% normalization error

Using electrons in

2 < pt < 20 GeV/c

obtain B meson

2 < ptmin < 30 GeV/c

MC-based

procedure

à la UA1

B  e + X: Results

1 year at nominal luminosity

(107 central Pb-Pb events, 109 pp events)

MCWS, Frascati, 24.10.2006 Andrea Dainese

comparison to pqcd predictions
Comparison to pQCD predictions

pp, s = 14 TeV

charm (D0  Kp)

beauty (B  e+X)

1 year at nominal luminosity

(109 pp events)

MCWS, Frascati, 24.10.2006 Andrea Dainese

perspectives for the 1 st month at 14 tev

1 year at nominal luminosity

~1 month

Perspectives for the “1st month at 14 TeV”
  • Expected statistical errors for a low-stats sample:
    • Scaling of statistical errors according to Nevts
    • No dedicated cuts study yet

D0 Kp

B  e + X

Detector configuration:

ITS + TPC + TOF

Detector configuration:

ITS + TPC + TRD

MCWS, Frascati, 24.10.2006 Andrea Dainese

summary
Summary
  • Charm 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

MCWS, Frascati, 24.10.2006 Andrea Dainese

extra slides
EXTRA SLIDES

MCWS, Frascati, 24.10.2006 Andrea Dainese

lhc running conditions
LHC running conditions

pp nominal run

Pb-PB nominal run

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

Ldt = 5.1026 cm-2 s-1 x 106 s

5.1032 cm-2 PbPb run, 5.5 TeV

NPbPb collisions = 2 .109 collisions





Muon triggers:

~ 100% efficiency, < 1kHz

Muon triggers:

~ 100% efficiency, ~ 1kHz

Electron triggers:

~ 50% efficiency of TRD L1

20 physics events per event

Electron triggers:

Bandwidth limitation

NPbPb central = 2 .108 collisions

Hadron triggers:

Npp minb = 2 .109 collisions

Hadron triggers:

NPbPb central = 2 .107 collisions





MCWS, Frascati, 24.10.2006 Andrea Dainese

beauty via single and di muons in central pb pb collisions

bb

bb dy ~ 1

 both muons

in the acceptance

Beauty via single and di- muons 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

 single muons in the spectrometer:

beauty dominates for pt > 2-3 GeV/c

MCWS, Frascati, 24.10.2006 Andrea Dainese

di muons invariant mass
Di-muons invariant mass
  • Single muon cut: pt > 2 GeV/c
  • Di-muon combinatorial bkgd subtracted with evt-mixing

MCWS, Frascati, 24.10.2006 Andrea Dainese

open beauty with muons results
Open Beauty with Muons: Results
  • Combined 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!

systematic error

analysis in progress

1 year at nominal luminosity

(107 central Pb-Pb events)

MCWS, Frascati, 24.10.2006 Andrea Dainese