# Presentation: 247764

## Andrea Dainese
INFN – Legnaro 

*INFN – Legnaro *

***Charm and Beauty ******at LHC******(open flavour and quarkonia)***

*HARD PROBES 2006*
*Asilomar, CA, June 9-16, 2006*

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## 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

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## LHC:           hard cross sectionslots 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

- * M.Mangano

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

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

**large**

| system, s | pp, 14 TeV | Pb-Pb (0-5%), 5.5 TeV |
| --- | --- | --- |
|  | 11.2 / 0.5 | 4.3 / 0.2 |
|  | 0.16 / 0.007 | 115 / 4.6 |

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

-  M.Cacciari

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Theoretical Uncertainties

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

- beauty

- charm

- CERN/LHCC 2005-014,
- hep-ph/0601164

**NLO pQCD, pp, ********s = 14 TeV**

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## 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 *R*AA
_*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

## 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

- Probe unexplored small-*x* region with HQs at low *p*t 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

***LHC: small-x***

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Heavy Quark Energy Loss

- 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.

- Energy loss depends on:

- medium transport coefficient

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

***Heavy Quark Energy Loss***

**“****Dead cone” effect for heavy quarks:**** **
- in vacuum, gluon radiation suppressed at ** < *m*Q/*E*Q

-  C.Salgado

- (BDMPS)

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## News from RHIC: heavy-flv decay electrons suppressed!

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

- Djordjevic, Gyulassy, Wicks, nucl-th/0512076

- Radiative

- Radiative + Collisional

- Energy loss calculations tend to underpredict suppression

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

-  C.Salgado

-  M.Djordjevic

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Azimuthal asymmetry (v2)

- Azimuthal asymmetry --*v*2 or *R*AA()-- of D and B mesons in *non-central* collisions tests:
- at low/moderate *p*t: recombination scenario, flow of c/b quarks (?), hence degree of thermalization of medium
- at higher *p*t: path-length dependence of E loss in almond-shaped medium

**PHENIX ********0**** v****2**

- 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

***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*

*For 10 < p*t* < 20 GeV/c, charm behaves like a m=0 quark,*
*light-flv hadrons come mainly from gluons*
_***R***__***D/h***__*** enhancement probes colour-charge dep. of E loss***_
_***R***__***B/h***__*** enhancement probes mass dep. of E loss***_

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

-  C.Salgado

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## LHC: Beauty-to-Charm ratio RB/D

***LHC: Beauty-to-Charm ratio ******R******B/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

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Tracking & Vertexing

|  |  |  |  |
| --- | --- | --- | --- |
| Tracker | TPC (100) + Silicon (6) | Silicon (11) | Silicon (16) |
| Si thickness (x/X0) | 7% | 30% | 20% |
| B field (T) | 0.5 | 2 | 4 |

***Tracking & Vertexing***

- D mesons  *c* ~ 100–300 m, B mesons  *c* ~ 500 m
- Secondary vertex capabilities! **** **Impact param. resolution!**

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Lepton and Hadron ID

- D and B: large B.R. to leptons: ~10% *e* + ~10% 
- ALICE:
- electrons: Transition Rad. + d*E*/d*x* in || < 0.9 and *p*t > 1 GeV/*c*
*                     *+ EM cal (performance under study)
- muons: -4 << -2.5 and *p*t >1 GeV/*c *(use *p*z to punch through abs.)
- CMS (ATLAS):
- muons: || < 2.4 (3) and *p*t > 3.5 (4) GeV/*c*
- electrons in EM cal? (no heavy-ion studies yet)
- With leptons, difficult to measure D(B) *p*t distr. and go to low *p*t (loose *p*t 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

## Charm reconstruction: D0 K-+

- Large combinatorial background **(d*****N*****ch****/d*****y*****=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 

- 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 pt coverage

***Expected p******t****** coverage***

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

- D0  K

- B  e + *X*

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Charm and Beauty E Loss : RAA 

***Charm and Beauty E Loss : R******AA****** ***

- D0  K

- 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

- 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

***Beauty via (forward) muons***

- inner bars: stat. errors
- outer bars: syst. errors

- Muons “identified” in the forward spectrometer (-4 << -2.5)

- Pb-Pb 0-5%

**** single muons in the spectrometer:
- beauty dominates for *p*t > 2-3 GeV/*c*

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## 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  tagging

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## QUARKONIA

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Quarkonia at LHC: (cc)

***Quarkonia at LHC: ************(cc)***

** **J/ suppression & regeneration?
-  c, ’ 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)

***Quarkonia at LHC: ************(bb)***

-   d/dy @ LHC ~20 x RHIC

** ** 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**

-  H.Satz

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Quarkonia at LHC:experimental challenges

- Important contribution to  production from B  J/(’) + *X*
- ~20% of J/
- ~40% of ’
- Normalization:
-  Drell-Yan not available for normalization (from qq, while quarkonia from gg at LHC; and small cross section at LHC)
-  W, Z?
- Different *Q*2, *x*
- Open heavy flavour, but ...
- Energy loss?
- Thermal charm production?
-  Possible alternative: *R*AA (à la PHENIX)

- Need to measure this!

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Quarkonia acceptances

***Quarkonia acceptances***

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Charmonia Performance

|  | ALICE +- | ALICE e+e- | CMS +- | ATLAS +- |
| --- | --- | --- | --- | --- |
|  |  |  |  |  |
| acc.  | -4 <  < -2.5 | || < 0.9 | || < 2.5 | || < 2 |
| M res. | 65 MeV | 35 MeV | 37 MeV | 70 MeV |
| 
J/, ’ | 150,  7 | 245, -- | 313,  -- | 60,  -- |
| perf. | , ?’ | , ??’ | , ?’ | , ’ |
| pt J/ | 0-20 GeV | 0-10 GeV | few-20 GeV | -- |

***Charmonia Performance***

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

- central

- central

- central

- min. bias

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Bottonia Performance

|  | ALICE +- | ALICE e+e- | CMS +- | ATLAS +- |
| --- | --- | --- | --- | --- |
|  |  |  |  |  |
| acc.  | -4 <  < -2.5 | || < 0.9 | || < 0.8(2.4) | || < 2 |
| M res. | 90 MeV | 90 MeV | 54(85) MeV | 145 MeV |
| 
,’,’’ | 30,  12,  8 | 21, 8, -- | 50,  17,  12 | 45,  --, -- |
| perf. | , ’, ?’’ | , ?’, no ’’ | , ’, ’’ | , ?’, no ’’ |
| pt  | 0-8 GeV | -- | few-10 GeV | -- |

***Bottonia Performance***

- ||<2.4

- ||<0.8

- central

- central

- min. bias

- central

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

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## J/ from B in CMS & ALICE

**J/********* ********* ********+********-**

**J/********* ********* e****+****e****-**

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

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Summary

- The LHC will be a heavy-quarks and quarkonia factory
- Heavy quarks as probes of QCD in extreme conditions
-  from low *p*t: probe small-*x* structure of p and nucleus
-  to high *p*t: 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

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## LHC running conditions

* ****Ldt  = 5.10**26** cm**-2** s**-1** x 10**6 **s *
*5.10**32** cm**-2** PbPb run, 5.5 TeV*
*N**PbPb collisions **= 2 .10**9** collisions  *

***Ldt dt  = 3.10**30** cm**-2** s**-1** x 10**7 **s *
*5.10**37** cm**-2**  for pp run, 14 TeV*
*N**pp collisions **= 2 .10**12** collisions  *

*Muon triggers:  *
* **~ 100% efficiency, ~ 1kHz  *

*Electron triggers:  *
*       **Bandwidth limitation*
* **N**PbPb central  **= 2 .10**8** 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:  *
* **N**PbPb central  **= 2 .10**7** collisions  *

*Hadron triggers:  *
* **N**pp minb  **= 2 .10**9** collisions  *

**

**

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## 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

## Shadowing in pA (AA)
CGC in pA (AA)
Double parton scattering in pA

- _CGC in pA (AA)_
- Double parton scattering in pA

- Saturation scale Qs*2**(x) ~ xg(x)A/R**A**2** ~ xg(x)A**1/3*
- At LHC for *x*~10-4, Qs~1.5-2 GeV > *m*c
- For *m*t,c~Qs, charm prod. CGC-dominated:
-  scales with Npart in pA (not Ncoll)
-  harder *p*t spectra, since typical *k*t~Qs~1.5 GeV, while
-    in standard factorization *k*t~QCD~0.2 GeV

***Probing nuclear PDFs with HQs***

- Kharzeev, Tuchin, NPA 735 (2004) 248

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Shadowing in pA (AA)
CGC in pA (AA)
Double parton scattering in pA

- CGC in pA (AA)
- _Double parton scattering in pA_

- probe “many-body” PDFs
- normal and anomalous: different A dep.

***Probing nuclear PDFs with HQs***

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

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Heavy Flavour RAA at LHC

- Baseline: PYTHIA, with EKS98 shadowing, tuned to reproduce c and b *p*T distributions from NLO pQCD (MNR)
- (*m/E*)-dep. *E* loss with

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

- * EKRT Saturation model:
- Eskola, Kajantie, Ruuskanen, Tuominen,
- NPB 570 (2000) 379.

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Tracking efficiency, fakes

- _CMS_

**CMS**

**ATLAS**

- (dN/dy ~ 3500)

- (dN/dy ~ 3500)

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Electron identification

- Combined info from TRD (trans. rad.) and TPC (d*E*/d*x*)
- TRD rejects 99% of the  and ALL heavier hadrons (*p*t > 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)

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

- D0  K

- B  e + *X*

*Expected sensitivity in comparison to pQCD:*

- 1 year at nominal luminosity
- (109 pp events)

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## pp: perspectives for the 1st month

***pp: perspectives for the 1******st****** month***

- Detector configuration:
- ITS + TPC + TOF

- 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 *N*evts
- No dedicated cuts study yet

**D****0**** ******** K******

- Detector configuration:
- ITS + TPC + TRD

**B ******** e *****+ X***

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## 3-body decays: D+ and Ds+

- D+: complementary to D0 measurement, important systematic check
- D+ (*c* ~ 310 m) → K with BR ~ 9.2%   compared to
- D0 (*c* ~ 124 m) → K with BR ~ 3.8%
-          *better* separation and *higher* BR, but *worse* comb. background
- preliminary studies: similar performance as for D0expected
- Ds+: probe of hadronization?
- from fragmentation (PYTHIA): Ds+(cs) / D+(cd) ~ 0.6
- from stat. hadronization: Ds+/D+ ~ s / q ~ 1 in QGP?
- Ds+ (*c* ~ 150 m) → KK with BR ~ 4.4 %
-   worse conditions than D+, but large resonant fraction in decay (through  or K0*K+) will help in comb. background rejection

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese

## Extracting quarkonia signals

- Example (bottonia to di-muon in ALICE):

** **get invariant mass cocktail for all centrality & *p*t 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-1
- Tc =270 MeV
- D/Tc=1.7 for J/
- D/Tc= 4.0 for .
- Suppression-2
- Tc=190 MeV
- D/Tc=1.21 for J/
- D/Tc= 2.9 for .

- PRC72 034906(2005)

-  Hep-ph/0507084(2005)

- Good sensitivity
- J/,  & ’

- Hard Probes 2006 - Asilomar, 15.06.06                     Andrea Dainese