(di-)leptons & heavy flavors in heavy ion collisions at the lhc (di-)leptons & heavy...

(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

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

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

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

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

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

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

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

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

ATLAS: heavy ion LOI (2004)

Heavy ions @ the LHC

CMS: strong heavy ion program

ALICE: the dedicated heavy ion experiment

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

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

Heavy flavors with CMS

muon spectrometer & silicon tracker in central barrel & end-caps

large acceptance, excellent resolution

J/, ’, , ’,’’, open charm, open bottom

Heavy flavors with ATLAS

muon spectrometer & silicon tracker in central barrel & end-caps

large acceptance

studies limited to reconstruction & b-jet tagging so far

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

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

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

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




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)

’/ 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%)

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%)


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


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”

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

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

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

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

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

b-hadron cross-section from secondary J/ in ppbar @ s = 1960 GeV (CDF results)

D. Dacosta et al., Phys. Rev. D 71 (2005) 032001

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

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

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

• 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

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

Electron-muon coincidences

• clean signal

• covers intermediate rapidities

• measurement done in pp @ ISR (1979!)

• challenging in heavy ion collisions

ALICE-INT-2000-01

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

(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

(di-)leptons & heavy flavors in heavy ion collisions at the lhc (di-)leptons & heavy...

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pp collisions

heavy ion collisions

suppression b

b decay dileptons

quenching b

leptons heavy flavors

days b

months pp