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