Heavy Quarks in view of the LHC
description
Transcript of Heavy Quarks in view of the LHC
Frankfurt, 07.12.2006 Andrea Dainese 1
Heavy Quarks Heavy Quarks in view of the LHCin view of the LHC
Andrea DaineseAndrea Dainese
INFNINFN(ALICE Collaboration)(ALICE Collaboration)
Frankfurt, 07.12.2006 Andrea Dainese 2
LayoutHigh-pT (heavy-flavour) particle production in hadronic collisions –from pp to AA– in factorized QCD
pp baseline: pQCD calculations
nuclear effects, in initial and final state
What have we learnt at Tevatron and RHIC?
What will be new at the LHC?
What do we expect?
What should we measure?
Experimental Perspectives at the LHC
PARTONPARTONENERGYENERGY
LOSSLOSS
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Heavy-flavour production: ppproton-proton collisions: factorized pQCD approach
)pp(zDp
xPDFxPDF cDDccT
c
/d
ˆd)()( 21
)~Q~( 2221 ccMsxx
s /2
c
c D
D
x1
x2
Q2
s /2),(d
dRFD
T
D
p
PDF:• Q2 evolution calculated in pQCD• initial condition from data (HERA)
FF: • non-perturbative • phenomenolgy + fit to data (e+e-)
calculable as perturbative series of strong coupling s(R)
22, Q~RF
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pp QQ: pQCD calculations vs data
Calculation of partonic cross section standard: Fixed Order (NLO) Massive (e.g. MNR code)
state-of-the-art: Fixed Order Next-to-Leading Log (FONLL)
Tp
more accurate at high pT
Cacciari, Frixione, Mangano, Nason and Ridolfi, JHEP0407 (2004) 033
B production at Tevatron (1.96 TeV)is well described by FONLL
CDF, PRL91 (2003) 241804FONLL: Cacciari, Nason
Charm production slightly underpredictedat Tevatron (1.96 TeV)
Cacciari, Nason, Vogt, PRL95 (2005) 122001
& at RHIC (200 GeV)Q e+X
QM06 update later
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Heavy-flavour production: AA
A
A
Binary scaling for hard yields: collDT
Dpp
DT
DAA NpNpN d/dd/d
Binary scaling is “broken” by:
c
c D
D
x
fgPb / fg
p
LHC RHIC SPSRAA <1 ~1 >1
Q2 = 5 GeV2
pT
RA
B
1
~2-4 GeV/c
kL kT
Cronin enhancement
• initial-state effects: PDF shadowing kT broadening (‘Cronin’)
medium formed in the collision
A
A c
cD
Du
• final-state effects energy loss? [next slide]
in-medium hadronization (recombination?)
recombination: pH = pq
fragmentation: pH = z pq
baryon/meson enhancement
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Calculating Parton Energy Loss
cc
ccRsC
I
for )/(
for /
d
d2
Baier, Dokshitzer, Mueller, Peigne‘, Schiff, NPB 483 (1997) 291.Zakharov, JTEPL 63 (1996) 952.Salgado, Wiedemann, PRD 68(2003) 014008.
BDMPS-Z formalismpath length L
kT
Radiated-gluon energy distrib.:
2
ˆTk
q transport coefficient
2/ˆ 2Lqc LR c
sets the scale of the radiated energyrelated to constraint kT < , controls shape at << c
Casimir coupling factor: 4/3 for q, 3 for gRC
(BDMPS case)
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Model vs RHIC “light” dataModel: pQCD + E loss probability + detailed collision geometry
Density ( ) “tuned” to match RAA in central Au-Au at 200 GeV
/fmGeV 144ˆ 2q
q
matches pT-indepence of suppression at high pT
Dainese, Loizides, Paic, EPJC 38 (2005) 461.
(Quark Matter 05)
Same theoretical calculation (SW quenching weights) and similar results in Eskola, Honkanen, Salgado, Wiedemann, NPA747 (2005) 511
Tpp
TAA
collTAA dpdN
dpdN
NpR
/
/1)(
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large RAA indep. of q q
Limited sensitivity of RAA
Strong suppression requires very large density
Surface emission scenario
RAA determined by geometry rather than by density itself
Limited sensitivity to
Need more differential observables:
massive partons
RAA vs reaction plane
study of jet shapes
…
q
Eskola, Honkanen, Salgado, Wiedemann, NPA 747 (2005) 511.
?
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Lower E loss for heavy quarks ?In vacuum, gluon radiation suppressed at < mQ/EQ
“dead cone” effect
Dead cone implies lower energy loss (Dokshitzer-Kharzeev, 2001):energy distribution d/d of radiated gluons suppressed by angle-dependent factor
suppress high- tail
Q
Dokshitzer, Khoze, Troyan, JPG 17 (1991) 1602.Dokshitzer and Kharzeev, PLB 519 (2001) 199.
1
1d
d
d
d2
2
2
Q
Q
E
mII
LIGHTHEAVY
Dokshitzer
22QQ
2 ])/([
1
Em
Gluonsstrahlung probability
R = 105
Detailed massive calculation confirms this qualitative feature
(Armesto, Salgado, Wiedemann, PRD 69 (2004) 114003)
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Charm RAA at RHIC
effect of the mass
thermalized component
/fmGeV 144ˆ 2q
Small effect of mass for charm (~50% for D, ~30% for e) at low pT [large uncertainties!]Basically no effect in “safe” pT-region
Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027.
(extracted from light-flv hadron data)
larger uncertainties
other contributions become important
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Charm + beauty + DY electrons at RHIC(pQCD baseline revised, and its uncertainties)
FONLL calculation: Cacciari, Nason, Vogt, PRL95 (2005) 122001Drell-Yan from: Gavin et al., hep-ph/9502372Comparison: Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326
FONLL: electron spectrum may be ~50% c + ~50% b for 3 < pT < 8 GeV
We investigated the DY component: < 10% up to 10 GeV
Large uncertainty on b/c crossing point in pT: from scales/masses variation it changes from 3 to 9 GeV
PHENIX electron cross section in pp now quite OK also at high pT
PHENIX hep-ex/0508034
PHENIX, hep-ex/0609010
QM06 update
?
QM06 update
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RAA of c and b electrons at RHIC
Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326,
Due to larger mass of b quark electron RAA increased to ~0.4
Mass uncertainty (in E loss) and scales uncertainty (in pQCD b/c crossing) were studied
c
b
c+b
Theory predicts e RAA (~0.4)
larger than RAA (~0.2) e spectra in principle sensitive to mass hierarchy Perturbative uncertainty on the pp baseline comparable to model-intrinsic uncertainty in determination of
Preliminary STAR data not conclusive for comparison with theory
nucl-ex/0611018
QM06 update
Theory predicts e RAA (~0.4)
larger than RAA (~0.2) e spectra in principle sensitive to mass hierarchy Perturbative uncertainty on the pp baseline comparable to model-intrinsic uncertainty in determination of
Final data (QM06): electron RAA tends to be overestimated
Djordjevic, Gyulassy, Wicks, nucl-th/0512076
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Other approaches: include elastic E loss (Djordjevic, Gyulassy, Wicks)
collisional dissociation of D/B mesons formed in the medium early after hard scattering (Adil & Vitev)
QM06 update
RAA of c and b electrons at RHIC
nucl-ex/0611018nucl-ex/0611018
(Adil & Vitev)
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LayoutHigh-pT (heavy-flavour) particle production in hadronic collisions –from pp to AA– in factorized QCD
pp baseline: pQCD calculations
nuclear effects, in initial and final state
What have we learnt at Tevatron and RHIC?
What will be new at the LHC?
What do we expect?
What should we measure?
Experimental Perspectives at the LHC
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Novelties at LHC (1): Hard ProbesLHC: large hard cross sections!
Our set of “tools” (probes) becomes richer
quantitatively: qualitatively:• heavy quarks
• + jet correlations• Z0 + jet correlations
bbRHIC
bbLHC
ccRHIC
ccLHC
100
10
LO pQCD by I. Vitev,hep-ph/0212109
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Heavy-quark production at the LHCpp: Important test of pQCD in a new energy domain
Remember the “15-years saga of b production at Tevatron”*
Baseline predictions: NLO (MNR code) in pp + binary scaling (shadowing included for PDFs in the Pb)
ALICE baseline for charm / beauty: system :
sNN :Pb-Pb (0-5% centr.)
5.5 TeV
p-Pb (min. bias)
8.8 TeV
pp
14 TeV
4.3 / 0.2 7.2 / 0.3 11.2 / 0.5
115 / 4.6 0.8 / 0.03 0.16 / 0.007
0.65 / 0.80 0.84 / 0.90 --
[mb] QQNN
QQtotN
Theoretical uncertainty of a factor 2—3 (next slide)* M.ManganoMNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.
98EKSshadowingC
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Theoretical Uncertainties(HERA-LHC Workshop)
MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.
Evaluation of theoretical uncertainties
beautycharm
MRST2001 CTEQ6, CTEQ5, CTEQ4, :PDFs
0.0040.0002 2/5.0 GeV 0.55.4
0.110.002 2/5.0 GeV 8.13.1 ,
bRFb
cTRFc
m
mm
CERN/LHCC 2005-014hep-ph/0601164
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Model Comparisons(HERA-LHC Workshop)
Compare predictions by several different models
Good agreement between collinear factorization based calculations: FO NLO and FONLLkT factorization (CASCADE) higher at large pT
beautycharm
CERN/LHCC 2005-014hep-ph/0601164
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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: “there ratio of results at 14 TeV/5.5 TeV has ‘small’ uncertainty”
charm beauty
12% 8%
MNR code: Mangano, Nason, Ridolfi, NPB373 (1992) 295.
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increasing s
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
Eskola, Kolhinen, Vogt, PLB582 (2004) 157Gotsmann, Levin, Maor, Naftali, hep-ph/0504040
Window on the rich phenomenology of high-density PDFs:
gluon saturation / recombination effects
Possible effect: enhancement of charm production at low pT w.r.t. to standard DGLAP-based predictions, even in pp!
c(DGLAP+non-linear)c(DGLAP)
Novelties at LHC (2): Small x
ccgg
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Probing nuclear initial state PDFs with HQs
Shadowing in pA (AA)
CGC in pA (AA)
Double parton scattering in pA
)/( ppNpPbR collDpPb
c
c
Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61
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Shadowing in pA (AA)
CGC in pA (AA)
Double parton scattering in pA
Saturation scale Qs2(x) ~ xg(x)A/RA
2 ~ 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~QCD~0.2 GeV
Probing nuclear initial state PDFs with HQs
c
c
Kharzeev, Tuchin, NPA 735 (2004) 248
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Shadowing in pA (AA)
CGC in pA (AA)
Double parton scattering in pA
probe “many-body” PDFs
normal and anomalous: different A dep.
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 it can be estimated from measured single inclusive b cross section
predicted rate: cccc/cc ~ 10% (Treleani et al.)
Probing nuclear initial state PDFs with HQs
c
c
Cattaruzza, Del Fabbro, Treleani, PRD 70 (2004) 034022
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Heavy Quark Energy Loss at LHC
~100 cc pairs and ~5 bb pairs per central Pb-Pb collision
Experiments will measure with good precision RAA for D and
B, and for their decay leptons (as I’ll show in 5’)
What can we learn from a comparative quenching study of
massive and massless probes at the LHC?
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Heavy Flavour RAA at LHCBaseline: PYTHIA, with EKS98 shadowing, tuned to reproduce c and b pT distributions from NLO pQCD (MNR)
(m/E)-dep. E loss with
MNR: Mangano, Nason, Ridolfi, NPB 373 (1992) 295.
/fmGeV 10025ˆ7ˆ 2* RHICLHC qq
Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027. * EKRT Saturation model:Eskola, Kajantie, Ruuskanen, Tuominen, NPB 570 (2000) 379.
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Colour-charge and mass dep. of E loss with Heavy-to-Light ratios at LHC
Heavy-to-light ratios:
Compare g h , c D and b B
)()()( )(/)( t
hAAt
BDAAthBD pRpRpR
gq EE mass effect
For 10 < pT < 20 GeV, charm behaves like a m=0 quark,light-flv hadrons come mainly from gluonsRD/h enhancement probes colour-charge dep. of E lossRB/h enhancement probes mass dep. of E loss
Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027
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LHC: Beauty-to-Charm ratio RB/D
Compare c and b: same colour charge
Mass effect Enhancement of factor ~2, independent of (for )
)()()(/ tDAAt
BAAtDB pRpRpR
q/fmGeV 20ˆ 2q
Adapted from Armesto, Dainese, Salgado, Wiedemann, PRD71 (2005) 054027
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Azimuthal asymmetry (v2)Azimuthal asymmetry --v2 or RAA()-- 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
= 0
= /2P
HEN
IX
0 v
2
Cole @ Quark Matter 05v2 from E loss: Dainese, Loizides, Paic, EPJC 38 (2005) 461
Armesto, Cacciari, Dainese, Salgado, Wiedemann, PLB637 (06) 326.
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LayoutHigh-pT (heavy-flavour) particle production in hadronic collisions –from pp to AA– in factorized QCD
pp baseline: pQCD calculations
nuclear effects, in initial and final state
What have we learnt at Tevatron and RHIC?
What will be new at the LHC?
What do we expect?
What should we measure?
Experimental Perspectives at the LHC
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Experimental study of heavy flavours in AA at the LHC
ATLASCMS
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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!
PrimaryVertex B
e
Xd0
rec. track
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Impact parameter resolution Resolution mainly provided by the layers of silicon pixels
PIXEL CELL
z: 425 m
r: 50 m
Two layers:r = 4 cmr = 7 cm
9.8 MINFN Padova-Legnaro
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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!
acceptance: pt > 1 GeV/cr < 50 m for pt > 2.5 GeV/c
pt/pt < 2% up to 100 GeV/c
acceptance: pt > 0.2 GeV/cr < 50 m for pt > 1.5 GeV/c
pt/pt < 2.5% up to 20 GeV/c < 6% up to 100 GeV/c
B = 0.5 TB = 4 T
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Lepton and Hadron IDD and B: large B.R. to leptons: ~10% e + ~10%
ALICE:electrons: Transition Rad. + dE/dx in || < 0.9 and pt > 1 GeV/c
+ EM cal (performance under study)muons: -4 << -2.5 and pt >1 GeV/c (use pz to punch through abs.)
CMS (ATLAS):muons: || < 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.)
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Charm reconstruction: D0 K-+
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
Invariant mass analysis
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Beauty via displaced electrons
PrimaryVertex B
e
Xd0
rec. track
ALICE has excellent electron identification capabilities (TRD + TPC)
Displaced electrons from B decays can be tagged by an impact parameter cut
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electron
Expected pt coverage1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)
D0 K B e + X
• should have similar performance • higher pt
min because lack of K id
• should have similar performance, at least with muons• higher pt
min because more material & larger field
CMS & ATLAS
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Calibrating the probe (pp, s = 14 TeV)
D0 K B e + X
tpp
tAA
colltAA pN
pN
NpR
d/d
d/d1)( measured at 14 TeV, then
scaled by pQCD to 5.5 TeV
Expected sensitivity in comparison to pQCD:
1 year at nominal luminosity(109 pp events)
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tDpp
tDAA
collt
DAA dpdN
dpdN
NpR
/
/1)(
tepp
teAA
collt
eAA dpdN
dpdN
NpR
/
/1)(
Charm and Beauty E Loss : RAA
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
D0 K B e + X
1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)
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Heavy-to-light ratios in ALICE
1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events)
)()()(/ thAAt
DAAthD pRpRpR
)()()( D from eB from e/ tAAtAAtDB pRpRpR
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Beauty via (forward) muons
inner bars: stat. errorsouter bars: syst. errors
Muons “identified” in the forward spectrometer (-4 << -2.5)
Pb-Pb 0-5%
single muons in the spectrometer:beauty dominates for pt > 2-3 GeV/c
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W’s 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
Ding, A.D., Zhou, QM06 poster. Conesa, A.D., Ding, Martinez, Zhou, in preparation
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J/ from B (à la CDF) in CMS & ALICE
primary J/
J/from B
energy LHCat 2.0~J/ψ all
B from J/ψ
J/ +- J/ e+e-
CMS: CMS/NOTE 2001/008, ALICE: CERN/LHCC 99-13
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ConclusionsAt LHC heavy quarks will be produced with large rates
robust tool for the study of QCD in extreme conditions
Heavy-quark phenomelogy promises to be very rich from very low pT: probe small-x structure of p and nucleus to very high pT: probe the QCD medium via energy loss
Excellent “heavy-quark busters” (ALICE, ATLAS, CMS) are being installed at CERN265 days to LHC startup!
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Appendix:QUARKONIA at LHC
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H.Satz
Quarkonia at LHC: (cc)
J/ suppression & regeneration?
c, ’ suppression (J/ TD ~ 1.5-2 Tc)?Satz, CERN Heavy Ion Forum, 09/06/05
SPSRHICLHC
30
enhanced suppression
enhanced regeneration
TLHC >> J/ TD Wong, PRC 72 (2005) 034906
Alberico, hep-ph/0507084
Becattini, PRL95 (05) 022301
Statistical hadronization: huge enhancements for cc, cc, Bc, ccc
e.g. 1000 for ccc/D from pp to Pb-Pb
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productionproduction
RHICRHIC LHCLHC
Vogt, hep-ph/0205330
Quarkonia at LHC: (bb) d/dy @ LHC ~20 x RHIC melts only at LHC
’ TD ~ J/ TDWong, PRC 72 (2005) 034906Alberico, hep-ph/0507084
Small regenerationGrandchamp et al., hep-ph/0507314
’ can unravel J/ suppression vs. regeneration
Gunion and Vogt,
NPB 492 (1997) 301
’/ vs pt sensitive to system temp. & size
H.Satz
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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 Q2, x
Open heavy flavour, but …Energy loss?Thermal charm production?
Possible alternative: RAA (à la PHENIX)
Need to measure this!
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+- +- +-
e+e-
Quarkonia acceptances
-4<<-2.5
J/
-4<<-2.5
ac
ce
pta
nc
e (
%)
J/
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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 PerformanceBkg input: dNch/dy~2500-4000 in central Pb-Pb. for 1 month
central central central
BSS /
min. bias
BSS /
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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
BSS /
Bkg input: dNch/dy~2500-4000 in central Pb-Pb. for 1 monthBSS /
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J/ from B in CMS & ALICE
primary J/
J/from B
energy LHCat 2.0~J/ψ all
B from J/ψ
J/ +- J/ e+e-
CMS: CMS/NOTE 2001/008, ALICE: CERN/LHCC 99-13
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EXTRA SLIDES
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Why RAA is flat Surface effectMost partons from inner part are totally absorbed
Energy loss is “saturated”: many partons radiate all their energy before getting outLong path lengths exploited only by high energy partons effectively, RAA doesn’t increase at high pT
Exercise: RAA increases with pT
Prod. points in (x,y) for partons giving hadrons with pT > 5 GeV:
increasing s
10.5 with , EE
LL
Loizides, PhD Thesis, nucl-ex/0501017
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Further handle on L-dependence*
First RAA vs appearing …(see talk by d’Enterria)
= 0
= /2PHENIX 0 prel. vs PQM
Data show stronger dep. than PQM model
PQMPQM
STAR Coll., PRL 93 (2004) 252301
Note: model is not E L2, rather E L * Beware: effect of collective flow on RAA vs !?!
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Open points (2): the opacity problem
Can we really probe the medium?
Need to relate extracted to an energy density QCD estimate for ideal QGP:
A recent analysis* of RHIC data, similar to that presented, extracts energy density 5 larger than that estimated from produced transverse energy dET/dy (Bjorken estimate)
Opacity problem: the interaction of the hard parton with the medium is much stronger than expected
q
)(2)(ˆ 4/3 q (Baier)
Baier, NPA 715 (2003) 209.* Eskola, Honkanen, Salgado, Wiedemann, NPA 747 (2005) 511.
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LHC running conditions
Ldt = 5.1026 cm-2 s-1 x 106 s
5.1032 cm-2 PbPb run, 5.5 TeV
NPbPb collisions = 2 .109 collisions
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
Muon triggers: ~ 100% efficiency, ~ 1kHz Electron triggers: Bandwidth limitation NPbPb central = 2 .108 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: NPbPb central = 2 .107 collisions
Hadron triggers: Npp minb = 2 .109 collisions
Frankfurt, 07.12.2006 Andrea Dainese 58
Application: Parton Quenching Model
Dainese, Loizides, Paic, EPJC 38 (2005) 461.
QW + Glauber-based medium geometry and density profile + PYTHIA for parton generation and fragmentation
The procedure in short:1) generate parton (q or g) with PYTHIA (or back-to-back pair)
2) calculate its L and average along the path
3) use quenching weights to get energy loss
4) quench parton and then hadronize it (independent fragm.)
q
qL ˆ ,
),ˆ,;( LqCEP RPYTHIA
TR pC ,
Fragm
entat ion
pT
pT – pT
dN/dpT
)]()(ˆ[ sTTsq BA
Frankfurt, 07.12.2006 Andrea Dainese 59
Charm Energy Loss at RHICCompute RAA for c, D, e (from D)
Baseline: PYTHIA, with EKS98 shadowing, tuned to match pT-shape of D cross section measured in d-Au by STAR
c-quark E loss as for light-flv hadrons, but using (mc/Ec)-dependent QW
extracted from 0,h RAA (central)
Thermalize charms that lose all energy dN/dmT mT exp(-mT/T), T = 300 MeV
Use a range in to visualize limited sensitivity of RAA to itself
Armesto, Dainese, Salgado, Wiedemann, PRD 71 (2005) 054027.EKS: Eskola, Kolhinen, Salgado, EPJC 9 (1999) 61.
q
baseline dN/dpT
baseline RAA
Frankfurt, 07.12.2006 Andrea Dainese 60
D0 K-+: Selection of D0 candidates
increase S/Bby factor ~103!
central Pb-Pb events
Frankfurt, 07.12.2006 Andrea Dainese 61
Expected Sensitivity to RAA
D0 K B e + X
15% systematic from efficiency corrections 15%
12% theory uncertainty in energy extrapolation 8%
-- charm electron subtraction ~5%
8% normalization error (<Ncoll>) 8%
Frankfurt, 07.12.2006 Andrea Dainese 62
Quarkonia Acceptances
J/
||<0.9
||<0.9
2.5<<4.0
2.5<<4.0
J/
Di-electronchannel
Di-muonchannel
Frankfurt, 07.12.2006 Andrea Dainese 63
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
b efficiency
u re
ject
ion