John Harris (Yale U.) Winter Workshop, Big Sky MT, 1 – 8 Feb. 2009 Physics in ALICE at the LHC.

John Harris (Yale U.) Winter Workshop, Big Sky MT, 1 – 8 Feb. 2009

Physics in ALICE at the LHC

ALICE at the LHC


LHC

Alice

Dedicated “general purpose”Heavy Ion experiment at LHC

The ALICE Experiment


ALICE Detectors & Acceptance

(charged particles)

µ arm

central barrel -0.9 < < 0.9• = 2 tracking, PID (TPC/ITS/ToF)• single arm RICH (HMPID)• single arm e.m. cal (PHOS)• jet calorimeter (EMCal)

forward muon arm 2.4 < < 4• absorber, 3 T-m dipole magnet10 tracking + 4 trigger chambers

multiplicity detectors -5.4 < < 3• including photon counting in PMD

trigger & timing detectors• 6 Zero Degree Calorimeters• T0: ring of quartz window PMT's• V0: ring of scint. Paddles


The ALICE Experiment (Installation)


ALICE Detectors in 2009 at LHC

• Complete – fully installed & commissioned

– ITS, TPC, TOF, HMPID, MUONS, PMD, V0, T0, FMD, ZDC, ACORDE,

TRIGGER, DAQ

• Partially completed

– TRD (20%) completed now

– PHOS (20%) completed now

– EMCAL (20%) just completed, installation in current shutdown

• At start-up full hadron and muon capabilities

• Partial electron and photon capabilities


04/18/23

The TPC Performance


~6.5% resolution in central Pb+Pb

2 2 2 222max

2 20

21 ( )2 ln

2 2 2e em c m c EE Zz

Cx A I

Energy loss (dE/dx)

separation power

to 50 GeV

PID

Tracking(cosmic rays)

First LHC Beam in ALICE


• ALICE ready for LHC collisions.

• First LHC proton beams circulated on

September 10th , 2008.

• 450 GeV/c proton + pixel interaction

Early p + p Physics in ALICE


• “Day 1” physics with p + p: global event properties (energies - 0.9/10/14 TeV?)

• requires only several x 10K events

< pT > vs Nch

Multiplicity distributions

< dNch /d|= 0 >

ALICE Heavy Ion Physics

Overview:

Soft Probes – “same as RHIC and Beyond” • Expansion dynamics different from RHIC• Soft physics measurements similar to RHIC

+ extended PID• Day 1 physics +

Hard Probes – Heavy Quarks• Displaced vertices (Do K- +) from TPC/ITS• Electrons in Transition Radiation Detector (TRD)

Hard Probes – Quarkonia• J/, , ’ (excellent), ’’(2-3 yrs), ’ ???

Hard Probes – Jet Quenching• Jets, pi-zeros, leading particles to large pT


Soft Physics in ALICELHC Heavy Ions –

• expectations based on QCD predictions, p + p extrapolations, & RHIC results• a lesson from RHIC “expect the unexpected” versatility!! ALICE!!

Soft Physics (pT ≤ 2 GeV/c) with heavy ions at LHC – • Is there a smooth extrapolation from SPS RHIC LHC?

ALICE

Particle Multiplicities


dNch/dy = 2600

dNch/dy = 1200

ln(√s) extrapolation

saturation model

Eskola hep-ph/050649

J. Phys. G 30 (2004) 1540

Soft Physics in ALICELHC Heavy Ions –

• expectations based on QCD predictions, p + p extrapolations, & RHIC results• a lesson from RHIC “expect the unexpected” versatility!! ALICE!!

Soft Physics (pT ≤ 2 GeV/c) with heavy ions at LHC – • smooth extrapolation from SPS RHIC LHC?• expansion will be different (HBT, v2, Tchem & Tkin,

strange/charm particles & resonances)


Hirano et al, nucl-th/0701075v2

N.Borghini & U.A.Weidemann, J.Phy.G 35 (2008) 023001

Equilibrium / Non-Equilibrium in ALICE

Non-equilibriums (s = 3 - 5)oversaturated

Equilibrium s = 1

Many additional questions: Strangeness enhancement? Correlation volume? Evolution in pp & PbPb?

B. Hippolyte et al.EPJ C49 (2007)

at LHC expect : Tch = 161 ± 4 MeVB = 0.8+1.2-0.6 MeV


Andronic et al.nucl-th/0511071

Rafelskiet al.E. J. Phys.C45 (2006) 61

Resonances (, , K*, …) Hadrons

• Reconst invariant mass spectrum, background subtract (like-sign method). • Mass resolutions ~ 1.5 - 3 MeV . pT statistical limits: 8 () to 15 GeV/c (,K*)

K*(892)0 K 15000 central Pb-Pb

K+K-

Mass resolution ~ 1.2 MeV

central Pb-Pb

Mass resolution ~ 2-3 MeV

Invariant mass (GeV/c2)

Short-lived resonances:



• Time difference between chemical and kinetic freeze-out • In medium modifications of mass, width, comparison of hadronic and leptonic channels → partial chiral symmetry restoration?


Resonances (, , , J/) e+e-

Short-lived resonances:


2 x 107 Pb+Pb events

• In medium modifications of mass, width, comparison of hadronic and leptonic channels → partial chiral symmetry restoration?

2 x 107 Pb+Pb events

Short-lived resonances:• In medium modifications of mass, width, comparison of hadronic and leptonic channels → partial chiral symmetry restoration?

2 x 107 Pb+Pb events - : significance = 12 - 15J/: significance = 40 - 50


Resonances (, , , J/) e+e-

Hard Probe Rates in ALICE

ALICE hard physics capabilities:- Electron/hadron disc. (TRD, EMCal)

- measurements (forward muon arm)

- Good discrimination (EMCal, PHOS)

- Fast trigger on jets (EMCal)

Hard Probes statistics in ALICE:

104/year in minbias Pb+Pb:

inclusive jets: ET ~ 200 GeV

dijets: ET ~ 170 GeV

: pT ~ 75 GeV

inclusive : pT ~ 45 GeV

inclusive e: pT ~ 30 GeVThanks – Peter Jacobs


Hard Probes in ALICE – Heavy Quarks

Heavy Quarks (mass/color dep. of parton E-loss)

• Displaced vertices (Do K- +) from TPC/ITS• Electrons in Transition Radiation Detector (TRD)


Heavy Quark RAA at RHIC & LHC!

Uncertainties at RHIC (bands > ±0.1 ) - perturbative production of c and b jets - ratio of c to b jets is very uncertain.

Wicks & Gyulassy, Last Call for LHC Predictions

RHIC LHC

Heavy quark electrons at RHIC D & B mesons at LHC

LHC: - Different slopes of spectra


Charm & Beauty E-Loss Ratios in ALICEDisplaced vertices (Do K- +) from trackingElectrons from Transition Radiation Detectors1 nominal year: 107 central Pb-Pb events, 109 pp events

errors: statistical (bars) and systematic (bands)

Sensitive to color charge

Sensitive to mass dep.E-loss calc.: Armesto, Dainese, Salgado, Wiedemann


Charm and Beauty E-Loss : RAA

D0 K

1 year at nominal luminosity(107 central Pb-Pb events, 109 pp events))

B e + X

D+ K

mC = 1.2 GeV

mC = 0

mb = 4.8 GeV

B eE-loss calc: Armesto, Dainese, Salgado, Wiedemann


Hard Probes in ALICE – QuarkoniaHeavy Quarks (mass/color dep. of parton E-loss)


Quarkonia (Initial T, Debye screening, recombination,..)

• J/, , ’ (excellent), ’’(2-3 yrs), ’ (very difficult)


John Harris (Yale) Tamura Symposium, U. T. – Austin, 20 – 22 Nov. 2008

Quarkonia

John Harris (Yale U.) US LHC User’s Meeting, 24 October 2008

T/TC 1/r [fm-1]

(1S)

J/(1S)

c(1P)

’(2S)

b’(2P)

’’(3S)

Karsch hep-lat/0502014v2

Measure melting order of cc: ’, c, J/bb: ’’, ’,





04/18/23

Particle Charmonia +- Charmonia e+e- Bottomonia +- Bottomonia e+e-

mass plots

(- bkg)

accept. -4 < < -2.5 || < 0.9 -4 < < -2.5 || < 0.9

M 65 MeV 35 MeV 90 MeV 90 MeV

S / (S+B) J/ 150, ’ 7 J/ 245

30, ’ 12,

’’ 8 21, ’ 8

channel , ’ , ’ , ’,’’ , ’, no ’’pt J/ 0-20 GeV J/ 0-10 GeV 0-8 GeV --

Quarkonia PerformancedNch/dy = 4000 in central Pb-Pb for 1 month

Hard Probes in ALICE – Jet Quenching





Jet Quenching (in next talk by Rene Bellwied) (E-loss, parton density, fragmentation, medium response)

• Jets, pi-zeros, leading particles to large pT

• Modification of fragmentation• Medium response to E deposition - dissipation on near- and away-side


Summary & Questions to AddressALICE – is a versatile, general purpose heavy ion detector at LHC

will contribute significantly to understanding of (soft & hard) HI physics

ALICE to address general (Soft Physics) Questions:How does the system evolve and thermalize from its initial state?What are the properties of the quark-gluon plasma at LHC energies?Is QCD Phase Diagram featureless above Tc? Coupling strength vs T….?Are there new phenomena?

ALICE to address Physics Questions with Hard Probes:What is the behavior of c-cbar and b-bar states in-medium?

(Ti, screening/suppression, enhancement?)Can we understand parton energy loss at a fundamental level?

Medium modifications? e.g. jet energies in ALICE up to ~ 225 GeV possible (stats) B-jets up to 80 – 90 GeV (stats in one PbPb month)Flavor dependence? (D, B, quark- and gluon-jets?)

Can we understand the hadronization (fragmentation) process?

Theory?Range of validity of theories (hydro, non-pQCD, pQCD, strings…)?Can there be new developments in theory, and understanding across fields? (lattice, hydro, string, pQCD E-loss,…)

End


John Harris (Yale U.) Winter Workshop, Big Sky MT, 1 – 8 Feb. 2009 Physics in ALICE at the LHC.

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Transcript of John Harris (Yale U.) Winter Workshop, Big Sky MT, 1 – 8 Feb. 2009 Physics in ALICE at the LHC.