Effect of heavy-quark E loss on the single m pt distribution

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Effect of heavy-quark E loss on the single m pt
distribution

• Heavy-quark energy loss, from RHIC to LHC
• Energy loss at forward rapidity (ALICE MUON arm)
• RAA of single muons (cbW/Z), without and with
  E loss

• Andrea Dainese
• with Z.Conesa del Valle, H.Ding, G.Martinez,
  D.Zhou

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The Key Pointms from W as a medium-blind
reference

• pQCD predicts b/W crossing at ptmuon 30 GeV/c
• In Pb-Pb, b-quark in-medium energy loss would
  shift crossing to lower pt
• How would the muon RAA look like?

Z.Conesa del Valle, G.Martinez, L. Aphecetche and
Ch. Finck, ALICE-INT-2006-021
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Heavy Quark Radiative Energy Loss
? N.Armesto
(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 lt 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.
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Reference for density p0 RAA at RHIC
QM06 (PHENIX highlights)
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RAA of c and b electrons at RHIC
? F.Antinori
b
cb
c
Radiative E loss calculations tend to
underpredict suppression
Armesto, Cacciari, Dainese, Salgado, Wiedemann,
PLB637 (06) 326,
Djordjevic, Gyulassy, Wicks, nucl-th/0512076
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Heavy Flavour RAA at LHC (y 0)

• y0 (in-medium path and E loss in transverse
  plane)
• 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.
MNR Mangano, Nason, Ridolfi, NPB 373 (1992) 295.
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Beauty in ALICE via forward muons

• Muons identified in the ALICE forward
  spectrometer
• (MUON acceptance -4 lt?lt -2.5, p gt 4 GeV/c,
  pt gt 1 GeV/c)

? single muons in the spectrometer beauty
dominates for pt gt 2-3 GeV/c
inner bars stat. errors outer bars syst. errors
Pb-Pb 0-5
R.Guernane et al. in PPR2
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E loss simulation Baseline spectra

• Modified procedure for Q?MQ?m kinematics (for
  faster calculations)
• Quark-level baseline c and b quark
  single-inclusive d2s/dptdy from MNR code (NLO
  pQCD)
• same parameters as for the PPR mc1.2 GeV,
  mFmR2mt,c, mb4.75 GeV, mFmRmt,b, CTEQ4M PDFs
  (with EKS98 for Pb-Pb)
• Peterson fragmentation function (with ymeson
  yQ)
• e parameter from HERA-LHC Workshop proceedings
  (M.Corradi)
• ec0.02, eb0.001 (from to LEP data)
• Decay of meson to muon using spectator model
• e.g. m kinematics for B?m from b?cmnm

MNR code Mangano, Nason, Ridolfi, NPB373 (1992)
295
Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61
HERA-LHC Proceedings, CERN/LHCC 2005-014,
hep-ph/0601164
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Baseline m from c and b, no E loss
MNRPetersonspectator model decay VS PYTHIA
(ALICE tune)
(from Z.Conesa) (from Z.Conesa)
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Total single-muon spectrum in Pb-Pb
Z.Conesa del Valle, G.Martinez, L. Aphecetche and
Ch. Finck, ALICE-INT-2006-021
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Effect of shadowing (EKS98) in Pb-Pb
(from Z.Conesa)
(from Z.Conesa)
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Effect of shadowing (EKS98) in Pb-Pb
W beauty charm total
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Effect of shadowing (EKS98) in Pb-Pb
just an indication (PYTHIA LO)
W beauty charm total
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Effect of shadowing (EKS98) in Pb-Pb
val. q sea q gluon gluon
W beauty charm total
W
1.00.850.85
EKS98 val. q
EKS98 sea q
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Effect of shadowing (EKS98) in Pb-Pb
val. q sea q gluon gluon
W beauty charm total
b
0.951.051
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E loss for c and b VS rapidity

• Calculation of radiated energy compute DE 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 h lt 4)

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m from b with E losseffect of mass
Effect of b-quark mass for ptmuon lt 20-30 GeV/c
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m from b with E losseffect of dN/dh scaling for
qhat
In this model, the effect of density decrease at
forward y is negligible within the MUON
spectrometer acceptance
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Effect of E loss in Pb-Pb
Crossing point shifts down by 5-7 GeV/c
RAA increases from 0.3 to 0.8
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Effect of E loss in Pb-PbMUON acceptance
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Effect of E loss in Pb-Pb
thin no mass effect thick mass effect
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Conclusions

• First estimation of energy loss effect on high pt
  muons
• 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)
• RCP (0-10)/(40-70)
• Expected ALICE sensitivity to RAA and RCP (pt
  coverage)

Outlook
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Guten Appetit!
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EXTRA SLIDES
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