(di-)leptons & heavy flavors in heavy ion collisions at the lhc (di-)leptons & heavy...
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(di-)leptons & heavy flavors in heavy ion collisions at the LHC
• (di-)leptons & heavy flavors: what is different at the LHC
• The LHC heavy ion program
• Selected physics channels
• quarkonia
• open heavy flavors
• low mass dileptons
• some more exotic channels
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Recent activities in the field
ALICE col. J. Phys. G 30 (2004) 1517;
CMS col., CMS NOTE 2000-060; ATLAS col., CERN/LHCC/2004-009
• Hard probes in heavy ion collisions at the LHC• 4 working groups (PDF, shadowing and pA; Photons; Heavy quarks and quarkonia; Jet physics)
• 3 workshops
• 1 CERN Yellow Report: CERN-2004-009 (493 pages, 308 figures)
• Heavy quarkonium working group• 6 working groups (Spectroscopy; Production; Quarkonium in media; Decays; Standard Model measurements; Future opportunities)
• 3 workshops
• 1 CERN Yellow Report: hep-ph/0412158 (521 pages, 260 figures)
• HERA and the LHC• 5 working groups (Parton density functions; Multi-jet final states and energy flow; Heavy quarks (charm and beauty); Diffraction; MC tools)
• 5 workshops
• written document in preparation
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Heavy flavors: what is different @ the LHC
• large primary production
• melting of (1S) by color screening
• none of the primary J/ survives the (PbPb)QGP
• large secondary production of charmoniakinetic recombination, statistical hadronization, DD annihilation, b-hadron decay
central AA
RHICLHC
hard gluon induced quarkonium breakup
hep-ph/0311048
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dimuons in ALICE, pt > 2 GeV/c
unlike-sign totalunlike-sign from bottomunlike-sign from charm like-sign from bottom
S.Grigoryan
(di-)leptons: what is different @ the LHC
• dileptons from b decay dominate the spectrum below & J/• large yield of secondary J/ from b decay• dileptons from b decay have different origin at low & high mass• sizeable yield of like-sign correlated dileptons from b decay
charm pure NLO
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Charm(onium) production, suppression, regeneration & in-medium modification
• interplay between different processes @ different time scales
• charm(onium) carries much more physics than anticipated
systematic studies are a must
time
dropping mass, flow
hadronic comovers
kinetic recombination
nuclear absorption
color screening
momentum fluctuations
statistical hadronization
quenching
parton-(pre)resonance breakup
pt broadening
increased polarization
parton cascade
DD annihilation
hard scattering, shadowing
b decay
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How well is the heavy flavor production x-section known @ the LHC ?
N. Carrer and A. Dainese, hep-ph/0311225
• theoretical uncertainties on absolute values: a factor 2-3
• theoretical uncertainties on the (5.5 TeV)/(14 TeV) ratio: few %
measuring (ccbar, bbbar) in pp collisions @ 14 TeV is top priority
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On the relevance of measuring (b) in pp collisions in the first days
• (b) in pp is mandatory for understanding (b) in pA & AA (shadowing, quenching)
• (b) in pp is mandatory for understanding () in pp, pA & AA (production, absorption, suppression)
• (b) in pp is mandatory for understanding (J/) in pp (& pA, AA) (N(b J/)/N(direct J/) ~ 30% in 4 w/o feed-down)
• open heavy flavor statistics is much larger than quarkonium statistics
(b) = day-one physics in pp collisions @ the LHC
4700
1
%20
%4.2
570
1
)(
)(
lbbN
llN
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Heavy ion (ALICE) data taking scenario
one LHC year = 7 months pp (107s) + few weeks AA (106s), starts in 2007
• 5 first years:
• regular pp runs at 14 TeV: commissioning, reference, dedicated pp physics
• first PbPb run at low luminosity: global observables, large x-sections
• 2 PbPb runs at high luminosity (Lint = 0.5nb-1/year): small x-sections
• 1 pA run: structure functions, hadronic reference
• 1 light ion run: energy density dependence
• later (different options depending on the first results):
• pp (or pp-like) at 5.5 TeV
• other light or intermediate-mass systems
• other systems p-likeA
• PbPb at low energy
• PbPb at 5.5 TeV & high luminosity
ALICE collaboration, J. Phys. G 30 (2004) 1517
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Heavy flavor physics program @ LHC(channels investigated so far)
• charmonia & bottomonia versus
• centrality
• transverse momentum
• system-size
• reaction plane
• open bottom (inclusive)
• cross-section from 2nd J/, single leptons & dileptons
• b quark energy loss
• open charm (exclusive D’s)
• transverse momentum distribution
• c quark energy loss
• electron-muon coincidences
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ATLAS: heavy ion LOI (2004)
Heavy ions @ the LHC
CMS: strong heavy ion program
ALICE: the dedicated heavy ion experiment
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ALICE (A Large Ion Collider Experiment)
ITS
TPC
FMD
PHOSABSORBER
MUON TRACKING CHAMBERS
MUON FILTER
DIPOLE MAGNETTOFTRDHMPID
L3 MAGNET
PMD
MUON TRIGGER CHAMBERS
1000 members80 instituts30 countries
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Heavy flavors with ALICE
(di-)muons: J/, ’, , ’,’’, open charm, open bottom
(di-)electrons: J/, ’, , ’,’’, open charm, open bottom
hadrons: exclusive D0
electron-muon coincidences: open charm & bottom
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Heavy flavors with CMS
muon spectrometer & silicon tracker in central barrel & end-caps
large acceptance, excellent resolution
J/, ’, , ’,’’, open charm, open bottom
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Heavy flavors with ATLAS
muon spectrometer & silicon tracker in central barrel & end-caps
large acceptance
studies limited to reconstruction & b-jet tagging so far
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Acceptance for heavy flavor measurements
• nice complementarity between the 3 experiments
• ATLAS & CMS acceptance is large in & limited to high pt
• ALICE combines hadrons, electrons, muons & covers low pt & high • ATLAS, CMS & ALICE-electrons/hadrons have inner tracking
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Quarkonium measurements in ATLAS
• & ’ can be well separated
• ’ & ’’ separation is difficult
• J/ studies underway
barrel (||<1)
||<1 ||<2.5
accep. + efficiency 4.9 % 14.3%
resolution (MeV) 126 152
CERN/LHCC/2004-009, L. Rosselet@Vienna04
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Quarkonium measurements in CMS
• M(dimuon) ~ 60 MeV @ M = 10 GeV in central barrel
• background mainly coming from uncorrelated muon-pairs
• J/ reconstruction limited to high pt
G. Baur et al., CMS NOTE 2000-060
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Quarkonium measurements in ALICE
background level 1 = 2 HIJING evts with dNch/d = 6000 @ = 0 each
mass resolutionacceptance
dielectrons
dimuons
• J/ measurement down to pt = 0 (unique @ the LHC)
• resolution allows to separate the 3 statesnote: no need for J/ trigger (at least in central PbPb collisions)
pt > 3 GeV/c trigger
pt > 3 GeV/c trigger
pt > 1 GeV/c trigger
pt > 2 GeV/c trigger
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cross-sections from R. Vogt in hep-ph/0311048,
assumes neither suppression nor enhancement
• J/: large stat., good sign. (allows much narrower centrality bins)
• ’: small S/B
• : good stat., S/B > 1, good sign.
• ’: good stat., S/B > 1, good sign.
• ’’: low statistics
similar rates for in the dielectron channel
Centrality dependence of quarkonium yields in ALICE-muon
S. Grigoryan (updated Dec.’04)
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’/ ratio versus pt
E. Dumonteil, PhD Thesis (2004) E. Dumonteil & P. Crochet, ALICE-INT-2005-
002
• Melting depends on
• resonance formation time, dissociation temp. & pt
• QGP temp., lifetime & size
• Ratio is flat in pp (CDF)
• Any deviation from the pp (pA) value is a clear evidence for the QGP (nuclear effects cancel-out)
• The pt dependence of the ratio is sensitive to the characteristics of the QGP
J.P. Blaizot & J.Y. Ollitrault, Phys. Lett. B 199(1987)499; F. Karsch & H. Satz, Z. Phys. C 51(1991)209; J.F. Gunion & R. Vogt, Nucl. Phys. B 492(1997)301
• full & realistic simulation
• error bars = 1 month of central PbPb (10%)
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b-hadron cross-section from single muons & unlike-sign dimuons in PbPb
1) get Nb from fits with fixed shapes (PYTHIA) & b yield as the only free parameter
#R. Guernane et al., (2004) *C. Albajar et al., PLB 213 (1988) 405; PLB 256 (1991) 121
pt (GeV/c) 1.5-3 3-6 6-9 9-30
N from b 53603501439 1659150445 14344438 303688
Mass (GeV/c2) 0-5 5-20
N from bb 41461793 6983130
UA1 MC method* used by CDF & D0, applied here# to central PbPb (5%)
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b-hadron cross-section from single muons & unlike-sign dimuons in PbPb
2) for each sample, correct Nb for eff. & Nevt, then convert to hadron cross-section
MC
minttmin
tt )(
)(1
dt)(
B
BBbBB pp
L
Npp
total number of b from the fit
integrated luminosity
global detection efficiency
R. Guernane et al., (2004), C. Albajar et al., PLB 213 (1988) 405; PLB 256 (1991) 121
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b-hadron cross-section from single muons & unlike-sign dimuons in PbPb
3) the b-hadron inclusive differential cross-section distribution
R. Guernane et al., (2004)
• input distribution well reconstructed
• agreement between the 3 channels
• statistics is (very) large
• systematic uncertainties underway
“measured data points”
input distribution
“a nice illustration that one can use Tevatron-like analyzes in PbPb collisions @ the LHC”
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Bottom from single electrons with displaced vertices
PbPb central (5%)B e in ITS/TPC/TRD
pt > 2 GeV/c, 200 < d0 < 600 m
40000 e from B, S/(S+B) = 90%
• d0 < d0cut: improve S/B for resonances
• d0 > d0cut: measure electrons from D & B
CERN/LHCC 99-13,R. Turrisi, CERN HIF, 04/13/05
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b-hadron inclusive differential cross-section from single electrons
R. Turrisi CERN HIF, 04/13/05 E-loss calculations: N. Amesto, A. Dainese, C.A. Salgado, U.A. Wiedemann, Phys. Rev. D 71 (2005) 054027
same method as the one used with (di-)muons plus scenario for b-quark energy loss
• electrons with 2 < pt < 16 GeV/c b-hadrons with 2 < pt
min < 23 GeV/c
• clear sensitivity to energy loss
• will be further used to get RAAb-hadrons
• RAAh, RAA
D0 & RAAb-hadrons can be measured
simultaneously
A. Dainese, nucl-ex/0312005, nucl-ex/0405008
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From NA50’s (J/)/DY to ALICE’s /bbbar(assuming no quenching on b quarks)
w/o nuclear absorption
with nuclear absorption
• statistics: one month PbPb• statistics of the reference is in
5<M<20GeV ~5 times larger than
that of the probe• errors dominated by uncertainties
on nuclear absorption (~20%)• systematic errors underway
R. Guernane & S. Grigoryan (2004)
EPJC 39 (2005) 335
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The Z0 as a normalisation to bottomonium suppression
• most natural normalization to is b (assuming quenching is under control!)
• Z0: “clean” signal for normalisation (alternative to Drell-Yan which is out of reach)
• not an universal normalisation (different shadowing for quarks & gluons)
CMS/NOTE 2001/008
Z0 in CMS:
• b-hadron decays dominate the dimuon imass
• 2 weeks PbPb @ L = 1027 cm-2s-1: 11000 Z0 +- in || < 2.5
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Secondary J/ from B decay
ALICE: CERN/LHCC 99-13, CMS: CMS/NOTE 2001/008
• disentangle primary & secondary J/
• measure inclusive b cross-section
• probe b quark in-medium energy loss
• B J/ (1S) anything: 1.16 0.10% (PDG)
• N(direct J/) in central (5%) PbPb @ 5.5 TeV: 0.31
• N(bbbar pairs) in central (5%) PbPb @ 5.5 TeV: 4.56
N(b J/) / N(direct J/) = 34% in 4
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b-hadron cross-section from secondary J/ in ppbar @ s = 1960 GeV (CDF results)
D. Dacosta et al., Phys. Rev. D 71 (2005) 032001
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Using secondary J/ from B decayto probe b quark energy loss
energy loss is modeled in 2 extreme cases:
• collisional energy loss (minimum)
• collisional + radiative energy loss (maximum)
with energy loss:
• yield reduced by a factor ~ 4
• distribution gets significantly narrower
secondary J/ from B decay in CMS, pt
> 5 GeV/c
I.P. Lokhtin & A.M. Snigirev, Eur. Phys. J. C 21(2001)155
interest to combine this study with dimuons from b-hadrons
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Low mass dilepton measurements
CERN/LHCC 99-13, B. Rapp, PhD thesis
• feasible in pp collisions (with ptl > 0.5 GeV/c & with Dalitz rejection in e+e-)
• challenging in PbPb collisions (min ptl threshold = 1 GeV/c, trigger & bgd)
• acceptance limited to high pt
• excluded in ATLAS & CMS
ALICE dielectrons, central PbPb, pt > 1
GeV/c
ALICE dimuons, proton-proton, pt > 0.5
GeV/c
ALICE dimuons, central PbPb, pt > 1
GeV/c
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Some more exotic channels
• Secondary J/ from tri-muon events in pp w/o 2nd vertex
• b measurements from like-sign dileptons
• electron-muon coincidences
• Z measurements
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• dimuon events:
• 85% of direct J/
• 15% of J/ from b decay
• tri-muon events:
• 15% of direct J/
• 85% of J/ from b decay
Secondary J/ from tri-muon eventsin pp w/o 2nd vertex reconstruction
dimuon evts in pp, pt > 1GeV/c
b-chain S/B = 3S/√S+B = 80
tri-muon evts in pp, pt > 1GeV/c
correlated muons
correlated muons from b
uncorrelated muons
A. Morsch (2004)
doable in pp & pA, very difficult in central ArAr
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b measurements from like-sign dileptons
2 sources of like-sign correlated dileptons:
• like-sign correlated b ~ unlike-sign correlated c
• B0 oscillations ~ 30% of total like-sign correlated
• clean signal (D mesons do not oscillate)
• signal measurable via (like-sign)-(event-mixing)
P. Crochet & P. Braun-Munzinger, Nucl. Instrum. Meth. A 484(2002)564
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Electron-muon coincidences
• clean signal
• covers intermediate rapidities
• measurement done in pp @ ISR (1979!)
• challenging in heavy ion collisions
ALICE-INT-2000-01
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Z measurements with the ALICE muon spectrometer
Z. Conesa del Valle, DIMUONnet’05
• pp @ 14 TeV: accep ~ 14 % 71000 /run
• PbPb @ 5.5TeV: accep ~ 10.8 % 13000 /run
• background studies underway
asymmetries in production & decay due to valence quarks
acceptance
)( )()W(Wq' q
PbPb
PbPb
PbPb
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(di-)leptons & heavy flavors in heavy ion collisions at the LHC
new environment, large statistics, new observables, new analyzes
rich physics program
further possibilities with dileptons
• B+ J/ K+, B0 J/ K0s, B0
s J/ , b J/ à la CDF & D0
• quarkonium & open heavy flavor flow
• quarkonium polarization
• dilepton correlations
first data in April 2007 ... stay tuned
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Recent results from CDF
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B measurements à la CDF
A.Dainese, nucl-ex/0311004, 0312005
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Low mass resonances: acceptance
w/o pt cut
pt 1 GeV/c
pt 0.5 GeV/c
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ALICE PID
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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% up to 10 GeV/c < 9% up to 100 GeV/c
B = 0.5 TB = 4 T
A.Dainese, SQM04