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HARD PROBES 2006 Asilomar, CA, June 9-16, 2006. Charm and Beauty at LHC (open flavour and quarkonia). Andrea Dainese INFN – Legnaro. Contents. Heavy flavour & Quarkonia at LHC: WHY? Heavy flavour & Quarkonia at LHC: HOW? ALICE, ATLAS, CMS

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charm and beauty at lhc open flavour and quarkonia

HARD PROBES 2006

Asilomar, CA, June 9-16, 2006

Charm and Beauty at LHC(open flavour and quarkonia)

Andrea Dainese

INFN – Legnaro

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

contents
Contents
  • Heavy flavour & Quarkonia at LHC: WHY?
  • Heavy flavour & Quarkonia at LHC: HOW?

ALICE, ATLAS, CMS

  • Selected examples of the physics potential for open heavy-flavour & quarkonia

thanks to:

A. Morsch, P. Crochet, F. Antinori, B. Wyslouch,

G. Roland, D. d’Enterria, H. Takai

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

open heavy flavour
OPEN HEAVY FLAVOUR

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

lhc hard cross sections lots of heavy quarks

factor ~2

uncertainty

(more later)

large

LHC: hard cross sectionslots of heavy quarks!
  • NLO predictions (ALICE baseline for charm & beauty)
  • In pp, important test of pQCD in a new energy domain
    • remember the “15-years saga of b production at the Tevatron”*…
    • …and c production not yet fully reconciled

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

CDF, PRL91 (2003) 241804

FONLL: Cacciari, Nason

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

 M.Cacciari

* M.Mangano

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

theoretical uncertainties
Theoretical Uncertainties

CERN/LHCC 2005-014,

hep-ph/0601164

NLO pQCD, pp, s = 14 TeV

charm

beauty

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

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

energy extrapolation via pqcd
Energy extrapolation via pQCD?
  • Different systems (pp, p-Pb, Pb-Pb) will have different s values
  • Results in pp at 14 TeV will have to extrapolated to 5.5 TeV (Pb-Pb energy) to compute, e.g., nuclear modification factors RAA
  • pQCD: ratio of cross sections at 14 TeV/5.5 TeV has small uncertainty

charm

beauty

12%

8%

FO NLO (MNR) [to be repeated with FONLL]

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

lhc small x

increasing s

LHC: small-x
  • 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 / CGC

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

slide8

path length L

Gluonsstrahlung probability

w

Q

kT

l

in medium, dead cone implies lower energy loss

Heavy Quark Energy Loss

 C.Salgado

(BDMPS)

Energy loss depends on:

colour coupling factor: 4/3 for q, 3 for g

medium transport coefficient

“Dead cone” effect for heavy quarks:

in vacuum, gluon radiation suppressed at q < mQ/EQ

Baier, Dokshitzer, Mueller, Peigne‘, Schiff, NPB 483 (1997) 291. Salgado, Wiedemann, PRD 68(2003) 014008.

Dokshitzer and Kharzeev, PLB 519 (2001) 199. Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003.

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

news from rhic heavy flv decay electrons suppressed
News from RHIC: heavy-flv decay electrons suppressed!

Indirect measurement: non-g electrons (Dalitz and conversions subtracted); c / b inclusive (large uncertainty on pp baseline!!)

 C.Salgado

 M.Djordjevic

Radiative

Radiative + Collisional

Energy loss calculations tend to underpredict suppression

Djordjevic, Gyulassy, Wicks, nucl-th/0512076

Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326.

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

azimuthal asymmetry v 2

f = p/2

f = 0

Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326.

Azimuthal asymmetry (v2)
  • Azimuthal asymmetry --v2 or RAA(f)-- of D and B mesons in non-central collisions tests:
    • at low/moderate pt: recombination scenario, flow of c/b quarks (?), hence degree of thermalization of medium
    • at higher pt: path-length dependence of E loss in almond-shaped medium

PHENIX p0 v2

Cole @ Quark Matter 05

v2 from E loss: Dainese, Loizides, Paic, EPJC 38 (2005) 461

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

lhc colour charge and mass dep of e loss with heavy to light ratios

mass effect

LHC: colour-charge and mass dep. of E loss with Heavy-to-Light ratios

Heavy-to-light ratios:

Compare g  h , c  D and b  B

 C.Salgado

For 10 < pt < 20 GeV/c, charm behaves like a m=0 quark,

light-flv hadrons come mainly from gluons

RD/h enhancement probes colour-charge dep. of E loss

RB/h enhancement probes mass dep. of E loss

Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

lhc beauty to charm ratio r b d
LHC: Beauty-to-Charm ratio RB/D
  • Compare c and b: same colour charge
  • Mass effect  Enhancement of factor ~2, independent of (for )

Adapted from Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

experimental study of heavy flavours in aa at the lhc

CMS

ATLAS

Experimental study of heavy flavours in AA at the LHC

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

tracking vertexing

acceptance: pt > 0.2 GeV/c

rf < 50 mm for pt > 1.5 GeV/c

acceptance: pt > 1 GeV/c

rf < 50 mm for pt > 2.5 GeV/c

B = 0.5 T

B = 4 T

Dpt/pt < 2% up to 100 GeV/c

Dpt/pt < 2.5% up to 20 GeV/c

< 3% up to 100 GeV/c

Tracking & Vertexing
  • D mesons ct ~ 100–300 mm, B mesons ct ~ 500 mm
  • Secondary vertex capabilities! Impact param. resolution!

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

lepton and hadron id
Lepton and Hadron ID
  • D and B: large B.R. to leptons: ~10% e + ~10% m
    • ALICE:
      • electrons: Transition Rad. + dE/dx in |h| < 0.9 and pt > 1 GeV/c

+ EM cal (performance under study)

      • muons: -4 <h< -2.5 and pt >1 GeV/c (use pz to punch through abs.)
    • CMS (ATLAS):
      • muons: |h| < 2.4 (3) and pt > 3.5 (4) GeV/c
      • electrons in EM cal? (no heavy-ion studies yet)
  • With leptons, difficult to measure D(B) pt distr. and go to low pt (loose pt correlation)

Exclusive hadronic decay channels (charm)

 Need PID (kaons!) to reject huge combin. background in AA

  • ALICE hadron ID: large TPC + high-res TOF + RICH (small acc.)

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

slide16

Invariant mass analysis

Charm reconstruction: D0 K-p+

  • Large combinatorial background (dNch/dy=6000 in central Pb-Pb!)
  • Main selection: displaced-vertex selection
    • pair of opposite-charge tracks with large impact parameters
    • good pointing of reconstructed D0 momentum to the primary vertex

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

beauty via displaced electrons

rec. track

e

Primary

Vertex

B

X

d0

Beauty via displaced electrons
  • ALICE has excellent electron identification capabilities
  • Displaced electrons from B decays can be tagged by an impact parameter cut

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

expected p t coverage

electron

CMS & ATLAS

  • should have similar performance,
  • at least with muons
  • higher ptmin because more material
  • & larger field
  • should have similar performance
  • higher ptmin because lack of K id
Expected pt coverage

1 year at nominal luminosity

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

D0 Kp

B  e + X

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

charm and beauty e loss r aa

mb = 4.8 GeV

Low pt (< 6–7 GeV/c)

Also nuclear shadowing (here EKS98), in-medium hadr…

High pt (> 6–7 GeV/c)

Only parton energy loss

Charm and Beauty E Loss : RAA

D0 Kp

B  e + X

1 year at nominal luminosity

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

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

heavy to light ratios in alice
Heavy-to-light ratios in ALICE

1 year at nominal luminosity

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

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

beauty via forward muons

W (weakly interacting)

dominates for pt > 30 GeV/c!!

Beauty via (forward) muons
  • Muons “identified” in the forward spectrometer (-4 << -2.5)

 single muons in the spectrometer:

beauty dominates for pt > 2-3 GeV/c

inner bars: stat. errors

outer bars: syst. errors

Pb-Pb 0-5%

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

atlas b tagged jets

u rejection

b efficiency

ATLAS: b-tagged Jets
  • Based only on impact parameter selection
  • Central Pb-Pb (HIJING) events
  • Rejection factor against light-quark jets vs b-tagging eff.
  • Factor 50 rejection when efficiency 40% required
  • Should improve when combined with m tagging

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

quarkonia
QUARKONIA

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

quarkonia at lhc y cc

enhanced regeneration

enhanced suppression

Statistical hadronization: huge enhancements for Xcc, Wcc, Bc, Wccc

e.g. 1000 for Wccc/Dfrom pp to Pb-Pb

30

SPS

RHIC

LHC

Becattini, PRL95 (05) 022301

Quarkonia at LHC: y (cc)

 H.Satz

  • J/ suppression & regeneration?
  • c, y’ suppression (J/ TD ~ 1.5-2 Tc)?

Satz, CERN Heavy Ion Forum, 09/06/05

  • TLHC >> J/ TD
  • Wong, PRC 72 (2005) 034906
  • Alberico, hep-ph/0507084

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

quarkonia at lhc bb

RHIC

LHC

Gunion and Vogt,

NPB 492 (1997) 301

 production

’/ vs pt sensitive to system temp. & size

Vogt, hep-ph/0205330

Quarkonia at LHC:  (bb)

 ds/dy @ LHC ~20 x RHIC

 H.Satz

  •  melts only at LHC
  • ’ TD ~ J/ TD
  • Wong, PRC 72 (2005) 034906
  • Alberico, hep-ph/0507084
  • Small  regeneration
  • Grandchamp et al., hep-ph/0507314
  • ’ can unravel J/ suppression vs. regeneration

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

quarkonia at lhc experimental challenges
Quarkonia at LHC:experimental challenges
  • Important contribution to y production from B J/y(y’) + X
    • ~20% of J/y
    • ~40% of y’
  • Normalization:

Drell-Yan not available for normalization (from qq, while quarkonia from gg at LHC; and small cross section at LHC)

 W, Z?

      • Different Q2, x

Open heavy flavour, but …

      • Energy loss?
      • Thermal charm production?

 Possible alternative: RAA (à la PHENIX)

Need to measure this!

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

quarkonia acceptances

m+m-

m+m-

m+m-

e+e-

J/y

J/y

acceptance (%)

-4<h<-2.5

-4<h<-2.5

Quarkonia acceptances

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

charmonia performance
Charmonia Performance

Bkg input: dNch/dy~2500-4000 in central Pb-Pb. for 1 month

central

central

min. bias

central

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

bottonia performance
Bottonia Performance

Bkg input: dNch/dy~2500-4000 in central Pb-Pb. for 1 month

central

central

min. bias

central

|h|<0.8

|h|<2.4

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

j y from b in cms alice

primary J/y

J/y from B

J/y from B in CMS & ALICE

J/ym+m-

J/y e+e-

CMS: CMS/NOTE 2001/008,ALICE: CERN/LHCC 99-13

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

summary

442 days to LHC startup!

Summary
  • The LHC will be a heavy-quarks and quarkonia factory
  • Heavy quarks as probes of QCD in extreme conditions
    • from low pt: probe small-x structure of p and nucleus
    • to high pt: probe the medium via energy loss
  • Charmonia and Bottonia as probes of QCD phase transition
  • Excellent “heavy-quark busters” (ALICE, ATLAS, CMS) are being installed at CERN

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

extra slides
EXTRA SLIDES

Hard Probes 2006 - Asilomar, 15.06.06 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





Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

probing nuclear pdfs with hqs
Probing nuclear PDFs with HQs
  • Shadowing in pA (AA)
  • CGC in pA (AA)
  • Double parton scattering in pA

Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

probing nuclear pdfs with hqs1
Probing nuclear PDFs with HQs
  • Shadowing in pA (AA)
  • CGC in pA (AA)
  • Double parton scattering in pA
  • Saturation scale Qs2(x) ~ xg(x)A/RA2 ~ xg(x)A1/3
  • At LHC for x~10-4, Qs~1.5-2 GeV > mc
  • For mt,c~Qs, charm prod. CGC-dominated:
  • scales with Npart in pA (not Ncoll)
  • harder pt spectra, since typical kt~Qs~1.5 GeV, while
  • in standard factorization kt~LQCD~0.2 GeV

Kharzeev, Tuchin, NPA 735 (2004) 248

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

probing nuclear pdfs with hqs2

predicted rate: cccc/cc ~ 10% (Treleani et al.)

signature: events with “tagged” DD (can use D0+e+ or e+e+) and ch. conj.

NB: there is a “background” from normal bb events, but is can be estimated from measured single inclusive b cross section

Probing nuclear PDFs with HQs
  • Shadowing in pA (AA)
  • CGC in pA (AA)
  • Double parton scattering in pA

probe “many-body” PDFs

normal and anomalous: different A dep.

Cattaruzza, Del Fabbro, Treleani, PRD 70 (2004) 034022

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

heavy flavour r aa at lhc
Heavy Flavour RAA at LHC
  • Baseline: PYTHIA, with EKS98 shadowing, tuned to reproduce c and b pT distributions from NLO pQCD (MNR)
  • (m/E)-dep. E loss with
  • * EKRT Saturation model:

Eskola, Kajantie, Ruuskanen, Tuominen,

NPB 570 (2000) 379.

Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027.

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

tracking efficiency fakes

ALICE

pT [GeV/c]

Tracking efficiency, fakes

ATLAS

CMS

CMS

(dN/dy ~ 3500)

(dN/dy ~ 3500)

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

electron identification

fraction of misidentified pions

Electron identification
  • 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

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

calibrating the probe pp s 14 tev

measured at 14 TeV, then

scaled by pQCD to 5.5 TeV

Calibrating the probe (pp, s = 14 TeV)

Expected sensitivity in comparison to pQCD:

B  e + X

D0 Kp

1 year at nominal luminosity

(109 pp events)

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

pp perspectives for the 1 st month

1 year at nominal luminosity

~1 month at end 2007

pp: perspectives for the 1st month
  • When? Latest statement from the machine (June 7): “Machine Closure: 31.8.07 Set up of machine, injection, followed by up to 10 weeks of pp collisions: Sept. to Dec. 2007”
  • 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

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

3 body decays d and d s
3-body decays: D+ and Ds+
  • D+: complementary to D0 measurement, important systematic check
    • D+ (ct ~ 310 mm) → Kpp with BR ~ 9.2% compared to
    • D0 (ct ~ 124 mm) → Kp with BR ~ 3.8%

better separation and higher BR, but worse comb. background

      • preliminary studies: similar performance as for D0expected
  • Ds+: probe of hadronization?
    • from fragmentation (PYTHIA): Ds+(cs) / D+(cd) ~ 0.6
    • from stat. hadronization: Ds+/D+ ~ gs / gq ~ 1 in QGP?
    • Ds+ (ct ~ 150 mm) → KKp with BR ~ 4.4 %

worse conditions than D+, but large resonant fraction in decay (through fp or K0*K+) will help in comb. background rejection

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

extracting quarkonia signals

0 < b < 3 fm

0 < b < 3 fm

0 < b < 3 fm

1.

2.

3.

Extracting quarkonia signals
  • Example (bottonia to di-muon in ALICE):
  • get invariant mass cocktail for all centrality & pt bins
  • subtract non-correlated dimuons (event-mixing subtraction)
  • fit invariant mass spectra with 3 modified Landau convoluted with Gaussian & exponential for background

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese

suppression scenario in alice
Suppression scenario in ALICE
  • Suppression-1
    • Tc =270 MeV
    • TD/Tc=1.7 for J/Y
    • TD/Tc= 4.0 for .
  • Suppression-2
    • Tc=190 MeV
    • TD/Tc=1.21 for J/Y
    • TD/Tc= 2.9 for .

PRC72 034906(2005)

Hep-ph/0507084(2005)

Good sensitivity

J/y,  & ’

Hard Probes 2006 - Asilomar, 15.06.06 Andrea Dainese