physics reach

Physics Reach

Christoph Blume

University of Frankfurt/Main

for the ALICE Collaboration

Christoph Blume, LHC Symposium 2003, May 1-3, Fermi National Accelerator Lab.

Physics Reach

Outline

ALICE physics

Strongly interacting matter

Observables

p+p physics

The ALICE experiment

Running conditions for Pb+Pb

and p+p running

Acceptance

Tracking performance

Particle identification

Low pt physics examples

Heavy quarks

Open charm

Open beauty

Quarkonia family

Parton energy loss

High pt particle spectra

Jets via correlations


ALICE Physics

Phases of Strongly Interacting Matter

Exploring the phase diagram of

strongly interacting matter

LHC provides access to the high

T, vanishing B QGP phase

Lattice QCD, B = 0Lattice QCD, B = 0

LHCLHC


ALICE Physics

Properties of QGP Phase @ LHC

Initial conditions

Hard processes

Probe of early state of reaction

Pertubative QCD

Significant part of cross section

High density parton distributions

Bulk of partons at x 10-3

Saturated gluon densities

Classical QCD: Qs A1/3/ x

Evolution of system will be

dominated by partons

Longer lifetime of QGP phase

Collective effects will be strongly

influenced by parton dynamics

partonic flow

Energydensity 1000 GeV/fm3

Temperature T 1 GeV


ALICE Physics

Observables

Jets

Open charm, beauty


ALICE Physics

Observables

Soft Regime

pt = 0–2 GeV/c

non-perturbative

Particle yields

chem. freeze-out

HBT interferometry

thermal freeze-out

Flow

expansion

Soft Regime

pt = 0–2 GeV/c

non-perturbative

Particle yields

chem. freeze-out

HBT interferometry

thermal freeze-out

Flow

expansion

Semi-hard Regime pt

= 2–5/10 GeV/c

Thermal photons

temp. evolution

Open charm, J/

plasma screening

pt-Spectra

mini-jets

Semi-hard Regime pt

= 2–5/10 GeV/c

Thermal photons

temp. evolution

Open charm, J/

plasma screening

pt-Spectra

mini-jets

Hard Regime pt

> 10 GeV/c

perturbative

Hard photons

Open beauty,

Jets

initial collisions

Hard Regime pt

> 10 GeV/c

perturbative

Hard photons

Open beauty,

Jets

initial collisions

ALICE will cover the transition from the soft (hadronic) to the hard (partonic) regime

Correlations between soft and hard probes only possible within ALICE

ALICE will cover the transition from the soft (hadronic) to the hard (partonic) regime

Correlations between soft and hard probes only possible within ALICE


ALICE Physics

p+p Physics

Benchmark for Pb+Pb: Multiplicities (strangeness)

J/ and Parton energy loss (jets)

Thermal photons

High energy densities @ LHC: 1.2 GeV/fm3

Comparable to N+N @ SPS/RHIC

Bulk of cross section at low pt

Investigation in a new energy regime

p+A program Nuclear structure functions

Benchmark for Pb+Pb


The ALICE Experiment

ITSLow pt trackingVertexing

ITSLow pt trackingVertexing

TPCTracking, dEdxTPCTracking, dEdx

TRDElectron IDTRDElectron ID

TOFPID, talk by C. WilliamsTOFPID, talk by C. Williams

HMPIDPID (RICH) @ high pt

HMPIDPID (RICH) @ high pt

PHOS,0 PHOS,0

MUON -pairs talk by A. Morsch

MUON -pairs talk by A. Morsch

PMD multiplicityPMD multiplicity



Running conditions for Pb+Pb

Large charged multiplicity

Estimates quite uncertain

Design for dNch/dy|max = 8000

Luminosity:

Lmax = 11027 cm-2s-1

Event rate:

8000 minimum bias coll./ s

~109 events/year

1% collected

Trigger for low cross section

observables

MUON, PIXEL, PHOS, TRD

High-Level Trigger (HLT)



Event Display Pb+Pb

TRDTRD

HMPIDHMPID

TOFTOF

TPCTPC

PHOSPHOS 60 << 6260 << 62



p+p Running Conditions

“Low“ luminosity: Lmax =

2-5 1030 cm-2 s-1

Event pile-up

TPC drift 88 s

On average 25 events

(for Lmax = 2 1030 cm-2 s-1)

Pile-up can be removed with

High-Level Trigger

Reduction in data volume:

factor 5

Short run periods with ‘‘ultra-low‘‘

luminosity no pile-up

Lmax 1029 cm-2 s-1



Acceptance Central Barrel



Tracking Performance

Reconstruction efficiency

dNch/dy = 8000, B = 0.4T

98% in TPC

Acceptance at high pt: ~90%

Momentum resolution:

dNch/dy = 8000, B = 0.4T

Combined tracking

ITS+TPC+TRD

9% (pt = 100 GeV/c)

9%

TPCprimary tracksTPCprimary tracks



Main Vertex Determination

For heavy-ion collisions

Large track statistics

Resolution in bending projection:

10–15 m (beam spot

15 m)

Resolution in non-bending

projection:

better than 10 m

For p+p collisions

Low track statistics

Effect on charm measurement

p+pp+p


Momentum

ITSITS

dE

/dx

HMPIDPrototype in STARHMPIDPrototype in STAR

TPC dE/dx resolution:6.8% for dN/dy = 80005.3% for dN/dy = 800

TPC dE/dx resolution:6.8% for dN/dy = 80005.3% for dN/dy = 800

Momentum (GeV/c)

dE/d

x (a

.u.)


Particle Identification



PID Summary


Low pt Physics Examples

Event-by-Event ++ HBT

Single event

Raw correlation function

Uncorrected for Coulomb

R = 8 fm, = 0.5

Tracking with ITS+TPC, B = 0.2T

Qinv (GeV)C

(Qin

v)


Low pt Physics Examples

Resonances: K*

Decay channel K* K+-

Invariant mass distribution

for 550 events

M(K+-) (GeV/c2)

En

trie

s


Heavy Quarks

Heavy quarks probe dynamics of whole QGP phase Perturbative in intial collisions

Thermal production in QGP

Direct measurement of heavy flavour in p+p and A+A mandatory

Quarkonia (J/ and states) Binding energy in the order of

mean energy in QGP

Sensitive to screening effects

Aim: correlation of heavy quark and quarkonia production as

function of pt

Uncertainty of factor 4 in predictions for pp @ LHCUncertainty of factor 4 in predictions for pp @ LHC

Quarkonia +-: MUON

Quarkonia e+e-: TPC+TRD

D K, ITS+TPC+TOF

Semileptonic decays of D + B:

ITS+TPC+TRD and MUON

DD (BB) via e coincidences: TRD+MUON

Quarkonia +-: MUON

Quarkonia e+e-: TPC+TRD

D K, ITS+TPC+TOF

Semileptonic decays of D + B:

ITS+TPC+TRD and MUON

DD (BB) via e coincidences: TRD+MUON


Heavy Quarks

Open Charm via Hadronic Decays

Affected by main vertexresolution in p+p caseAffected by main vertexresolution in p+p case

D0 K-

c= 123.7 0.8mBR: (3.83 0.09) %

D0 K-

c= 123.7 0.8mBR: (3.83 0.09) %

cuts depend on D0 ptcuts depend on D0 pt


Heavy Quarks


Input to simulation cc: PYTHIA, tuned to NLO

calculations, with CTEQ4L and nuclear shadowing EKS98

Background: HIJING

Reconstruction effects included

PID with TOF

System (s) Pb-Pb (5.5 TeV) pp (14 TeV)

Signal

for 107 (109) evts13000 20000

S/B 11 % 50 %

Significance

for 107 (109) evts37 84

Pb+PbPb+Pb

minv = 12 MeV (B = 0.4T)minv = 12 MeV (B = 0.4T)


Heavy Quarks


Pb+Pb:Pb+Pb:

dN/dpt Significance

pt > 1 GeV/cpt > 1 GeV/c

p+p:p+p:

pt > 0 GeV/c !pt > 0 GeV/c !

dN/dpt SignificanceSignificance =

BSS /


Heavy Quarks

Open Beauty via Semileptonic Decays

B e- + X

Electron ID in TPC + TRD

Cuts:

Impact parameter d0

Electron pt

pt > 2 GeV/c + d0 > 150 m:

5-10·104 e with S/(S+B) = 90 %

pt > 2 GeV/c + d0 > 150 m:

5-10·104 e with S/(S+B) = 90 %

d0 (m)

En

trie

s (a

.u.)


Heavy Quarks

J/ and via Dielectrons

Mass resolution for 100 MeV (B = 0.4T)Mass resolution for 100 MeV (B = 0.4T)

::

J/:J/:

Acceptance down to pt = 0!Acceptance down to pt = 0!


Heavy Quarks

Secondary J/from B Meson Decays

B J/ e+e- (BR: 1%)

Large contribution to observable J/ signal

Possibility to disentangle primary and secondary J/s

J/from B decays

Impactparameter


Parton Energy Loss


Parton Energy Loss

Medium induced gluon radiation

Depends on traversed distance

L2

Stronger in deconfined matter

Effects:

Reduction of single inclusive high

pt particles

• Parton specific (stronger for

gluons than quarks)

• Flavour specific (stronger for

light quarks)

• Measure identified hadrons (, K,

p, , etc.) + partons (charm,

beauty) at high pt

Suppression of mini-jets

• same-side / away-side

correlations

Change of fragmentation function

for hard jets (pt >> 10 GeV/c)

• Transverse and longitudinal

fragmentation function of jets

• Jet broadening reduction of jet

energy, dijets, -jet pairs

p+p and p+A measurements

crucial


High pt

RHIC Results

RAA clearly different between

mesons and baryons

Importance of PID at high pt

p+p baseline measurement!

tdpppdtdpAAd

collNtpAAR

)()(1)(


High pt

Minimum Bias Pb+Pb and p+p

Estimates for the pt limit in one

year ALICE running

107 Pb+Pb events

109 p+p events

p+p simulation PYTHIA 6.210 +

CTEQ5L (default tuning)

Scaled to 107 Pb+Pbmin. bias events Scaled to 107 Pb+Pbmin. bias events

104 rec.p+p evts.104 rec.p+p evts.

~2103 tracks pt > 50 GeV/c~2103 tracks pt > 50 GeV/c

109 p+p events: 103 tracks with pt 40 GeV/c

109 p+p events: 103 tracks with pt 40 GeV/c

pt (GeV/c)

pt (GeV/c)

dN/d

p tN

( p

t)

High pt trigger (TRD, HLT) will extend pt range to > 100 GeV/c

High pt trigger (TRD, HLT) will extend pt range to > 100 GeV/c


High pt

Identified Particles:

One year of ALICE running (107 events)

s up to pt = 12 GeV/c

Can be improved using PID for daughters

S/B 15.5 /event

S/B 15.5 /event

% of rec. s vs pt% of rec. s vs pt

Reconstructedpt spectrumReconstructedpt spectrum

M(p) (GeV/c2)

Ent

ries

%

pt (GeV/c)

pt (GeV/c)

Y

ield


High pt

Identified Particles: +

Direct Direct

Inclusive : Direct + 0Inclusive : Direct + 0Inclusive : Direct + 0Inclusive : Direct + 0

Direct Direct

with high-pt triggerwithout high-pt trigger for 107 events

Separationof/0 and detection up to 100 GeV/c Statistically for low pt (< 30-40 GeV/c) E-by-E at higher pt (> 30-40 GeV/c)

pt (GeV/c)

dN/d

p t

pt (GeV/c)

dN/d

p t


Jets in Pb+Pb

Correlations with Leading Particle

Transformation d2N/dd1/R dN/dR with: R2

= 2 + 2

1000 HIJING events (default)

pt(seed) = 5 GeV/cpt > 3 GeV/c

pt(seed) = 5 GeV/cpt > 3 GeV/c

R

1/R

dN

/dR

pt (GeV/c)

1 < R < 2 1 < R < 2

R < 0.3R < 0.3


Jets in Pb+Pb

Two Particle Correlations

Correlation

increases with pt

Effect of gluon

radiation

System size

dependence

p+p

21

21acospp

pp

)mixed(/)real(/)(

ddNddNc


Summary

ALICE physics reach extends

from:

Low pt > 0.1 GeV/c

• Identified particles

• Correlations, HBT

• Event-by-event observables

• Flow

to:

High pt ~ 100 GeV/c

• Heavy quarks

• Quarkonia

• Photons

• Jets

p+p and p+A physics

Baseline for A+A

Important physics on its own

Integral part of ALICE physics

program

Physics Performance Report

Full simulations for all projected

physics observables

physics reach

Documents

alice experimentp p

pb pblarge

ujets initial collisions

gevc thermal photons

high t

gevc nonperturbativeparticle

ultralow luminosity

new energy regimep