John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

High PT Physics in ALICE

LHC

Alice

Dedicated “general purpose”Heavy Ion experiment at LHC

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE Overview

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE Set-upHMPID

Muon Arm

TRD

PHOS

PMD

ITS

TOF

TPCSize: 16 x 26 meters

Weight: 10,000 tons

EMCal

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE Detectors & Acceptance

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

(charged particles)

µ arm

EMCal

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Global tracking (ITS-TPC-TRD) + dE/dx (low pT + relativ. rise) + TOF, HMPID, PHOS, …

Invariant mass, topological reconstruction

Particle Identification in ALICE

Pb-Pb

Decay particles 10-15 GeV, K, p 0.1- 0.15 50 GeV

pT range for PID in 107 central Pb-Pb and 109 min. bias pp

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE EMCal

10+1/2+1/2=11 super-modules8 SM from US3 SM from France, Italy

Lead-scintillator sampling calorimeter = 1.4, =110o

Shashlik geometry, APD photosensor ~13K towers ( x ~ 0.014 x 0.014)

Energy resolution 15%/√E + 2%

over-takes tracking above 30 GeV

o/ discrimination to pT ~ 30 GeV

Approved by LHCC 9/28/06

Allows Jet Measurements with ALICE

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

US Involvement in ALICEALICE-USA Collaboration

12 DOE-supported research institutions:

Creighton , Houston, Kent State, LBNL, LLNL, Michigan State,

Oak Ridge, Purdue, Tennessee, Texas, Wayne State, and Yale

ALICE-USA Primary Focus

• Investigate medium modification of partonic energy loss – “jet quenching”

• Investigate response of medium to large energy depositions

• Ensure the EMCal is constructed, operational in ALICE; extract EMCal physics

ALICE-USA Equip. Proposal to DOE for Major Fraction of ALICE EMCal

• Construct 8 of 11 super-modules of EMCal for ALICE

Italy and France proposing to construct 3

• CERN LHC Committee approved EMCal for installation in ALICE

• Passed CDs-0,1 Reviews of DOE

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

LHC Heavy Ions & ALICE Physics Overview

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Heavy Ion Physics at the LHCSoft Physics at LHC –

• smooth extrapolation from SPS RHIC LHC?

• expansion will be different

spectra, Tchem & Tkin, , particle ratios, v2, HBT,

strange/charm particles, resonances

Hard Probes at LHC –

• significant increase in hard cross sections

hard /total~ 2% at SPS

50% at RHIC

98% at LHC

• “real” jets, large pT processes

• abundance of heavy flavors

• probe early times, calculable precision studies!

bb (LHC ) ~ 100 bb (RHIC)

cc (LHC) ~ 10 cc (RHIC)

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE Measurements in a Nutshell

Soft Probes – “ala RHIC” (STAR + PHENIX) • Expansion dynamics different from RHIC due to timescales, densities• All soft physics measurements as at RHIC so far (+ extended PID)• Day 1 physics +

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

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), ’ (…)

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

High PT Physics with ALICE EMCal

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Physics with the ALICE EMCal

Utilize Initial Hard Parton Scattering

• High energy jets, photons and heavy flavors requires EMCal and triggering

Exploit large kinematic range of jets at LHC

Measure jet structure & medium-induced jet modification

Investigate energy loss mechanism with

quark-tagged jets (heavy flavor decays)

gluon jets (light hadron leading)

– jet coincidences

• Low energy particles correlated with trigger or quenched jet

requires ALICE acceptance, robust tracking, & PID to low/high

pT

Investigate energy propagation in medium to determine medium properties

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Capabilities of ALICE with EMCal

EMCal improves detector capabilities:

- Fast trigger ~10 -100 enhancement of jets

- Improves jet reconstruction (plus TPC)

- Good discrimination

increases coverage

- Good electron/hadron discrimination

EMCal extends the physics of 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 – P.Jacobs

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Start of Detailed “Tomography” of the QGPFQGP (g

QGP) = finitial (√s, A1+A2, b, x1, x2, Q2)

fQGP (pT,y , ,pT

jet,y jet ,jet, flavor jet, flow)

“jetflow plane

/parton

partonne

ar-

side

Renk, hep-ph/0602045

Di-hadrons penetrate core!

Renk, hep-ph/0602045

near

-sid

e

Trigger hadrons come from near-side surface

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Di-Hadron Correlations at RHIC

“jet

Data: STAR, nucl-ex/0510002;

pQCD E-loss Model + expansion: Renk, hep-ph/0602045

No near-side sensitivity to medium Slight away-side sensitivity to medium

More extensive di-hadron measurements from PHENIX (hep-ex/0605039) and STAR (nucl-ex/0510002):

Di-hadron fragmentation functions exhibit only a weak sensitivity to medium!

- jet and better jet energy (full jet) measurements necessary

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Tagging Jets with Photons

Strategy (event by event):

R

Thanks - Gustavo Conesa Balbastre – INFN Frascati

IP

EMCal

TPC

R

Reconstruct the jet : Particles around leading with pT > 0.5 GeV/c,

inside a cone of R = 0.3.2 configurations:

charged and neutral hadrons (TPC+EMCAL) and charged only (TPC).

min max

Search for leading particle : - leading ~ 180º

Eleading > 0.1 E leading

PHOS

Search for identified prompt photon (in PHOS)

with largest pT (E > 20 GeV)

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Jet Reconstruction

coneRFragmentation:

z hadron

parton

p

p

Fragmentation:

p(hadron)p (parton)

z =

= (2 + 2 )

Large background in RHI Collisions – must limit jet cone radius R, track pT cut

only measure fraction of parton energy - calibrate

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Soft Background in Jet Cones

ET = 100 GeV, R = 0.4

(TPC+EMCal)

(TPC)

(TPC – like RHIC)

background

Ń no pT cut

Ń pT >1 GeV/c

Ń pT >2 GeV/cET

jet

100 GeV

150 GeV

50 GeV

30 GeV

R

E(R

) [G

eV]

Cone radius R=√(Δη2+ΔΦ2)

Large cone radius large background

Radius cut of .4 + pT cut lowers background > 80% of Ejet

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Medium Modification of Jet Fragmentation

Fragmentation along jet axis: z = phadron / p parton

Introduce = ln(Ejet / phadron) ~ ln (1/z):jet direction

z

Sensitivity to

Sensitivity to

pT = 2.0 0.7 GeV/c

A. Morsche (ALICE)

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Medium Modification of Jet Fragmentation

Fragmentation along jet axis: z = phadron / p parton

Introduce = ln(Ejet / phadron) ~ ln (1/z):jet direction

z

Thanks – Joern Putschke

N. Borghini, U. Wiedemannhep-ph/0506218

# particles with low z increases

# particles with

high z decreases

z/1ln

pThadron~2 GeV

/fmGeV50~ˆ7~ˆ 2RHICLHC qq

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Ideal Case for Pb + Pb and p + p

fm/GeV50ö 2q

Solid: unquenched (p+p)

Pythia-based simulation with quenching

Dashed: quenched jet (central Pb+Pb)

q^

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Jet Quenching in ALICE with EMCAL in 1 Year

ratio

S B 0.002B

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE Jet Trigger Enhancement

Jet trigger

Includes acceptance, efficiency, dead time, energy resolution

Compare central Pb+Pb to reference measurements in• Pb+Pb peripheral: vary system size and shape• p+A: cold nuclear matter effects• p+p (14 TeV): no nuclear effects, but different energy• p+p (5.5 TeV): ideal reference, but limited statistics

Systematic study involves all reference systems

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

ALICE Jet Trigger Yields in an LHC Pb + Pb Year

Jet yield in 20 GeV bin

Large gains due to jet trigger

Large variation in statistical reach for different reference systems

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Summary

ALICE - versatile, general purpose heavy ion detector at LHCwill contribute significantly to understanding of HI physics

- soft physics- high pT physics

ALICE EMCal provides significant high pT and jet physicsmeasures and triggers on jets, photons, pi-zerosheavy quark jet tagstriggered jets response of medium in lower pT sector

Work continues todevelop best jet algorithm for heavy ions

deal with background, jet-splitting & jet-mergingdevelop heavy flavor (quark) tag algorithms

Need detailed theoretical/simulation approach at parton level

John Harris (Yale) Winter Workshop on Nuclear Dynamics, Big Sky, MT, 12 – 17 Feb. 2007

Special thanks for contributors:

Joern Putschke

Gustavo Conesa Balbastre

Marco van Leeuwen

Peter Jacobs

Matt Lamont

Andreas Morsche