LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 1

RRAAAA and R and RCPCP of single muons of single muons

from heavy quark and vector boson decays from heavy quark and vector boson decays at the LHCat the LHC

Z.Conesa del ValleZ.Conesa del Valle11, , A.DaineseA.Dainese22, H.-T.Ding, H.-T.Ding33, ,

G.MartinezG.Martinez11, D.Zhou, D.Zhou33

11Subatech Nantes, Subatech Nantes, 22INFN Legnaro, INFN Legnaro, 33CCNU WuhanCCNU Wuhan

Workshop on Predictions for LHC, CERN, May 29 – June 2, 2007

thanks to N.Armesto, C.Salgado, U.Wiedemann

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 2

The Key Point:

’s from W as a medium-blind referencepQCD predicts b/W crossing at pt

muon ~ 30 GeV/c

from W should be unaffected by the medium

b-quark energy loss would shift crossing to lower pt

How would the muon RAA / RCP look like?

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 3

LHC Experiments: Muon Acceptance

ALICE muon spectrometer: -4 << -2.5 and pt >1 GeV/c

CMS, ATLAS: || < 2.5 and pt > 3.5 GeV/c

High pt reach in Pb-Pb: about 70-80 GeV/c

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 4

Baseline spectraHeavy quarks:

Quark-level baseline: c and b quark single-inclusive d2/dpTdy from MNR code (NLO pQCD)

parameters: mc=1.2 GeV, F=R=2mT,c, mb=4.75 GeV, F=R=mT,b, CTEQ4M PDFs (with EKS98 for Pb-Pb)

Peterson fragmentation function (with ymeson = yQ)

parameter from HERA-LHC Workshop proceedings (M.Corradi)

c=0.02, b=0.001 (from to LEP data)

Decay of meson to muon using spectator modele.g. kinematics for B from bc++

Vector bosons:PYTHIA (reproduces W cross section at Tevatron)

Cross section normalized to NLO results (Frixione-Mangano, Vogt)more details in: Z.Conesa del Valle et al. ALICE-INT-2006-021

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

HERA-LHC Proceedings, CERN/LHCC 2005-014, hep-ph/0601164Frixione, Mangano, hep-ph/0405130; Vogt, hep-ph/0011242

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

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 5

Total single-muon spectrum in Pb-Pbwithout E loss

ALICE muon spectrometer acc.:-4 < < -2.5, pt > 1 GeV, p > 4 GeV

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 6

Effect of shadowing (EKS98) in Pb-Pb

Wbeautycharmtotal

-4 < < -2.5

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 7

Effect of shadowing (EKS98) in Pb-Pb

. :

2 :

21

21

constMQsxxWqq

pQsxxbbgg

WNN

tNN

Wbeautycharmtotal

just an indication (PYTHIA LO):

-4 < < -2.5

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

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 8

Effect of shadowing (EKS98) in Pb-Pb

val. qsea qgluongluon

EKS98 val. q EKS98 sea q

W1.0*0.85=0.85

Wbeautycharmtotal

ALICE muon spectrometer-4 < < -2.5

-4 < < -2.5

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 9

Effect of shadowing (EKS98) in Pb-Pb

val. qsea qgluongluon

bEKS98 gluonEKS98 gluon0.95*1.05=1

Wbeautycharmtotal

ALICE muon spectrometer-4 < < -2.5 -4 < < -2.5

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 10

Heavy Quark Radiative E LossMass-dependent BDMPS quenching weights

Glauber collision geometry à la PQM

Transport coefficient for a static medium: /fmGeV 10025ˆ 2q

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

EKRT Saturation modelEskola, Kajantie, Ruuskanen, Tuominen, NPB 570 (2000) 379.

C.Salgado

C.Loizides

/fmGeV 144ˆ 2RHICq

/fmGeV 10025ˆ 2LHCq

7 (corresponds todNch/dy ~ 3000)

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 11

E loss for c and b VS rapidityCalculation of radiated energy: compute E using Lt; quench pt; keep y constant.

Decrease of medium density at forward rapidity should be accounted for

Assumed , i.e.

using LHC multiplicity as predicted by D.Kharzeev, E.Levin, M.Nardi, hep-ph/0408050

(gives moderate density change for || < 4) pt

y

Lt

d

dNq ch)(ˆ

0*

)0(ˆ*)(ˆ

d

dN

d

dNqq chch

-15%

negligible effect on muon suppression for || < 4

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 12

Effect of E loss in Pb-Pb 0-10%

Crossing point shifts down by 5-7 GeV/c RAA increases from 0.3 to 0.8

RCP (0-10%)/(40-70%)increases from 0.4 to 0.9

Similar results in -4 < < -2.5

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 13

Effect of E loss in Pb-Pb 0-10%- b mass effect -

thin: no mass effectthick: mass effect

thin: no mass effectthick: mass effect

RAA RCP

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 14

Summary

At LHC, high pt muon spectrum will be one of the first measurements sensitive to b quark energy loss

Crossing point of b and W muons shifts down by 5-7 GeV/c

RAA rapidly increases from 0.3 to 0.8 between 20 (b-dominated) and 40 GeV/c (W-dominated)

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 15

EXTRA SLIDES

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 16

Baseline: from c and b, no E loss

(from Z.Conesa)

(from Z.Conesa)

BD can be neglected:

MNR+Peterson+spectator model decay VS PYTHIA (ALICE tune)

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 17

from b with E loss:effect of mass

Effect of b-quark mass for ptmuon < 20-30 GeV/c

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 18

from b with E loss:effect of dN/d scaling for qhat

In this model, the effect of density decrease at forward y is negligiblewithin the MUON spectrometer acceptance

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 19

Effect of E loss in Pb-Pb- ALICE muon spectrometer -

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 20

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 21

LHC Predictions Workshop, CERN, 01.06.2007 Andrea Dainese 22