Heavy-Ion Physics with Compact Muon Solenoid at Large Hadron Collider Bolek Wyslouch Massachusetts...

Heavy-Ion Physics with Heavy-Ion Physics with Compact Muon SolenoidCompact Muon Solenoidat Large Hadron Colliderat Large Hadron Collider

Bolek WyslouchMassachusetts Institute of

Technology

Los Alamos25 October 2007

CMS

October 25, 2007 Los Alamos Bolek Wyslouch 2

Quark Gluon PlasmaQuark Gluon PlasmaData from SPS & RHIC show new and unexpected properties of hot nuclear matter

Jet quenching, strong elliptical flow, d+Au- control data indicate that we have produced strongly interacting color liquid

LHC will significantly increase energy density New properties of the plasma

Continuation of strong coupling regime? Weakly interacting Plasma?

New tools to study to hot and dense state Hard probes Access to very low-x


Summary of physics opportunitiesSummary of physics opportunities

LHC will accelerate and collide heavy ions at energies far exceeding the range of existing accelerators The increase of beam energy will result in:

Extended kinematic reach for pp, pA, AA New properties of initial state, saturation at mid-rapidity A hotter and longer lived partonic phase Increased cross sections and availability of new hard probes

New energy regime will open a new window on hot and dense matter physics: another large energy jump!

AGS SPS RHIC LHC

sNN[GeV] 5 20 200 5500

E increase x4 x10 x28

y range 1.6 3.0 5.3 8.6


Large Hadron ColliderLarge Hadron Collider

LHC is about to start operations:

2008: proton-proton collisions

at ~14 TeV 2008:

p+p at 14 TeV Pb+Pb at 5.5 TeV per

nucleon pair

Heavy Ions Expect ~1 month of

heavy ion collisions each year

Beam

Energ

y


Rapidity Density600 1200

PHOBOS Central Au+Au (200 GeV)

Compilation by K. EskolaColor Glass

Kharzeev & Levin, Phys. Lett. B523 (2001) 79

Data: PHOBOS,Phys. Rev. Lett. 87, 102303 (2001)

From Eskola, QM 2000

First RHIC Surprise: Multiplicities Are “Low”First RHIC Surprise: Multiplicities Are “Low”

Low, that is, compared to pre-data predictions of “cascading partons”

Consistent with predictions based on gluon saturation :


LHC?

Extrapolated to LHC:dN/d~1000-2000

LHC multiplicity is likely to be lowLHC multiplicity is likely to be low

?

Note: this is an important experimental issue!

Is it saturation that makes it so low?Will it increase at higher energies?


RHIC’s Two RHIC’s Two MajorMajor Discoveries Discoveries

Discovery of strong “elliptic” flow:

Elliptic flow in Au + Au collisions at √sNN= 130 GeV, STAR Collaboration, (K.H. Ackermann et al.). Phys.Rev.Lett.86:402-407,2001

307 citations

Discovery of “jet quenching”

Suppression of hadrons with large transverse momentum in central Au+Au collisions at √sNN = 130 GeV, PHENIX Collaboration (K. Adcox et al.), Phys.Rev.Lett.88:022301,2002

357 citationsF

low

str

en

gth

Su

pp

res

ion

Fac

tor

Strongly interacting liquid with very lowviscosity

http://www.slac.stanford.edu/spires/find/hep/wwwauthors?key=4462483


http://arxiv.org/abs/nucl-ex/0009011




http://arxiv.org/abs/nucl-ex/0109003


Elliptic Flow at RHICElliptic Flow at RHIC

Flow (asymmetry in pT) is near to hydrodynamic limit,LHC: can it grow even more ?

STAR

HYDRODYNAMICS

Flow


““Jet Quenching” at high pJet Quenching” at high pTT: will it continue at LHC ?: will it continue at LHC ?

p+p

Au+Au

Energy loss of partons in hot and dense matterE.g. charged particle RAA for multi-100 GeV/c pT

Parton Energy loss


Quarkonia in Heavy IonsQuarkonia in Heavy Ions

•J/ suppression in heavy ion collisions has been heralded as a discovery of Quark Gluon Plasma at CERN SPS circa 2000: there are fewer J/’s produced as energy density is increasing•There is a lot of detailed experimental data from SPS. RHIC is now releasing new information, it is consistent with SPS•Theoretical interpretation is difficult: we possibly need to look towards LHC: family can provide important hints, there are three states with differing binding energy

SPS

Suppression ?

Regeneration ?

RHICLHC

Energy Density


Post-RHIC Dream heavy-ion detectorPost-RHIC Dream heavy-ion detector

Large acceptance for charged and neutral hadrons, muons, photons, electrons covering wide pT range hermeticity

Good resolution for high pT probes (jets, J/, family) resolution

Good trigger to allow selection of rare events speed Good particle identification 0, b-, c-quarks, muons,

electrons, photons, , Ks, , K , p particle ID

Most likely it does NOT have to handle extreme multiplicities

Relatively low luminosity of LHC as a heavy-ion accelerator

CMS

““High density QCD with heavy-ions”High density QCD with heavy-ions”

D.d'E (ed.) CERN-LHCC-2007-009; J.Phys.G. to appear.

170 pages10 chapters~90 figures, ~20 tables

~20 CMS-AN-Notes

Athens, Auckland, Budapest, CERN,

Chongbuk, Colorado, Cukurova, Ioannina,

Iowa, Kansas, Korea, Lisbon, Los Alamos,

Lyon, Maryland, Minnesota, MIT, Moscow,

Mumbai, Seoul, Vanderbilt, UC Davis, UI

Chicago, Vilnius, Zagreb

~25 CMS-HI institutions~100 collaborators


Calorimeters: high resolution and segmentation

Hermetic coverage up to ||<5 (||<6.6 with the proposed CASTOR)Zero Degree Calorimeter

Muon tracking: from Z0, J/, Wide rapidity coverage: ||<2.4

σm 50 MeV at the mass in the barrel Silicon Tracker

Good efficiency and purity for pT~>0.3 GeV

Pixel occupancy: <2% at dNch/d 3500

p/p 1-2% for 1<pT <100 GeV

Good low pT reach using pixels

Functional at the highest expected multiplicities: studied in detail at dNch/d 3000-5000 and cross-checked at 7000-8000

• DAQ and Trigger– High rate capability for A+A, p+A, p+p– High Level Trigger: real time HI event

reconstruction

CASTORCASTOR

(5.2 < |η| < 6.6)

ZDCZDC

(z = 140 m, |η| > 8.2 neutrals)

CMS, as a heavy ion experimentCMS, as a heavy ion experiment


CMS coverageCMS coverage

HCAL (Barrel+Endcap+Forward)

| | < 3.0ECAL + HCAL

3 .0< | | < 5.2Forward HCAL

8.2 < ||ZDC (neutrals)

5.2 < | | < 6.6CASTOR

| | < 2.4Tracker, muons

CoverageSub detector

Q2


Silicon Tracker

CMS under constructionCMS under construction

Hadron Calorimeter

Electromagnetic Calorimeter

Si tracker &Pixels

Muon Absorber

DAQ


Centrality and forward detectorsCentrality and forward detectors

Energy in the forward hadronic calorimeter

Zero Degree Calorimeter

Tungsten-quartz fibre structure electromagnetic section: 19X

0

hadronic section 5.6λ0

Rad. hard to ~20 Grad (AA, pp low lum.) Energy resolution (n,): E~E·10%

Position resolution: ~2 mm (EM sect.)~140 meters from CMS IP

Centrality (impact parameter) determination is needed for most physics analyses


Zero Degree CalorimeterZero Degree Calorimeter


CASTOR: Tungsten-Quartz

5.2 < η < 6.6

T2 Tracker TOTEM

5.2 < η < 6.6

CASTORCASTOR


Charged particle multiplicityCharged particle multiplicity

Will be one of the first results, important for initial energy density, saturation, detector performance etc.

ch

Muon detection, tracking, jet finding performance checked up or larger than dNch/d=5000

high granularity pixel detectors pulse height measurement in each pixel

reduces background Very low pT reach, pT>26 MeV (counting

hits)

W. Busza, CMS Workshop, June 2004

Simple extrapolation from RHIC data


Elliptic Flow measurements in CMSElliptic Flow measurements in CMS

• Use calorimeters and tracker

•Event plane reconstruction•v2 measurements

•Very large acceptance v2() tracker


Jets at RHICJets at RHIC

nucleon nucleonparton

jet

Find this……….in this


Production of QCD jetsProduction of QCD jets

c

d

ab

c

d

ab

Proton-proton Ion-ion“Clean” Jet Quenched, absorbed, modified jet

2008-> 2009->

““Hard QCD”Hard QCD”““Soft QCD”Soft QCD”


nhit > 12pchi2 > 0.01dca <3

• Efficiencyo Fake Rate

High-pHigh-pTT (leading) charged hadrons (leading) charged hadrons

Excellent tracking performances (PbPb, dNch

/d = 3500):

Momentum resolution

Impact parameter resolution

Expected dN/dpT

reach pT~300 GeV/c

(high ET HLT)

C.Roland, CMS-AN06-001

Displaced vertexes from heavy-Q decays measurable


Pixel Tracking, low pPixel Tracking, low pT T reach of CMSreach of CMS

Pixel tracking All tracker fitting

800 MeV


Pixel trackingPixel tracking

Track finding efficiency vs pT and for p+p and central Pb+Pb

Fakes are controlled using pixel hit shapeF. Sikler


High-pHigh-pTT (leading) charged hadrons (leading) charged hadrons

Nuclear modification factor (= AA-yield / pp-yield) at the LHC:

×5 suppr.

Strong discrimination power for parton energy loss models:

- Initial parton medium density: dNg/dy~O(2-4·103)

- Medium transport coefficient: <q>~O(10-100) GeV2/fm

extended reach ~300 GeV/cw/ high-E

T (jet)trigger

PbPb (PYQUEN) 0.5 nb-1

C.Roland et al., CMS-AN06-110


Pb-Pb full jet reconstructionPb-Pb full jet reconstruction

Iterative-cone + backgd subtraction. [New developments (fast-KT)

under study] 1. Subtract average soft background 2. Find jets: iterative cone algorithm 3. Recalculate pileup outside cone 4. Recalculate jet energy

jet energy: reco vs. MC efficiency, purity energy resolution

I. Vardanyan et al. CMS-Note-2006-50


Pb-Pb full jet reconstructionPb-Pb full jet reconstruction

Jet spectra up to ET~ 0.5 TeV (PbPb, 0.5 nb-1, HLT-

triggered). Detailed studies of medium-modified (quenched) jet FF possible.

min.bias

HLT

C.Roland et al., CMS-AN06-110

I. Lokhtin et al., PLB567 (03)39

Gluon radiation:large-angle (out-of-cone) vs. small-angle emission

Njets

~6·106


- , - , *- , Z- jet tagging (CMS)*- , Z- jet tagging (CMS)

Possibility to calibrate jet-energy loss (and Fragmentation Functions) with back-to-back gauge boson (large cross-sections, good detection capabilities):

Dominant (heavy-Q) dimuon backgd. “removable” via secondary-vtx. cut

Dimuon trigger

Associated Hadrons

q/g Z0 / *

Away side

C.Mironov et al.

NZ-jet

~103

pT

>25 GeV/c

r=50 m

=20 m3 vtx. cut


ETo - ET

Jet (GeV)

Eve

nts/

5 G

eV

ETjet, > 120GeV in Barrel, 1 month at 1027 cm-2s-1 Pb+Pb

, Z0

Jet

Balancing Balancing or Z or Z00//** vs Jets vs Jets Jet quenching with calibrated

energy On average Z/ ET and jet ET

should balance (unquenched jets) Z -> and can be reconstructed

with very good ET resolution Dominated by quark jets

q + g -> q + Z0/

-Jet: Need to control the background

from leading 0 in QCD dijets Reject 0 by cluster isolation cuts

in the calorimeters Quenching will help

Lower Thresholds Z0 - Jet

Cleaner but lower rates

dN/dy ~7000, unquenched Jetsnew studies to appear shortly


Quarkonia: probe of high-density QCD mediaQuarkonia: probe of high-density QCD media

Dissociation (color screening) = hot QCD matter thermometer

Probe of low-x gluon structure/evolution:

Lattice QQ free energy vs T:Spectral function vs T:

Suppression pattern vs

[H.Satz, hep-ph/0512217]

production via gg fusion: x~10-3 (10-5)Q2~10 GeV2

gluon saturation,non-linear QCD

_


Heavy Ion MC Event in CMSHeavy Ion MC Event in CMS

Pb+Pb event display: Produced in CMS software framework (simulation, data structures, visualization)

Pb+Pb event (dN/dy = 3500) with -> -


J/J/ψψ suppression suppression

J/ acceptance Best mass resolution @ LHC

pT reach (0.5 nb-1)

SPS

suppression ?

regeneration ?

RHICLHC

Energy Density

= 35 MeV/c2

J/ ' S/BO.Kodolova, M. Bedjidian, CMS-AN06-116

NJ/~1.8·105

|y|<1


suppressionsuppression

acceptance

’/ stat. reach (HLT)

= 54 MeV/c2’

’’

family S/B Best mass resolution @ LHC

pT reach (0.5 nb-1) spectroscopy (seq. suppr.)

O.Kodolova, M. Bedjidian, CMS-AN06-116

Strong models constraint

N~2.5·104 Gunion&R.Vogt

October 25, 2007 Los Alamos Bolek Wyslouch 35Bolek Wyslouch

Ultra-Peripheral collisions Ultra-Peripheral collisions Pb Pb Quarkonia

photoproduction

Probes nuclear PDF in unexplored (x,M2) range

Uses ZDC to trigger on forward emitted neutrons

Measurement --> +-, e+e- in the central detector


CMS Trigger and DAQ in p+pCMS Trigger and DAQ in p+p

Level-1 p+p

Collision rate 1GHz

Event rate 32MHz

Output bandwidth 100 GByte/sec

Rejection 99.7%

Level 1 trigger- Uses custom hardware- Muon tracks + calorimeter information- Decision after ~ 3μsec

High Level Trigger p+p

Input event rate 100kHz

Output bandwidth 225 MByte/sec

Output rate 150Hz

Rejection 99.85%

High level Trigger- ~1500 Linux servers (~10k CPU cores) - Full event information available- Runs “offline” algorithms


High Level Trigger Pb+Pb p+p

Input event rate 3kHz (8kHz peak) 100kHz

Output bandwidth 225 MByte/sec 225 MByte/sec

Output rate 10-100Hz 150Hz

Rejection 97-99.7% 99.85%

Level-1 Pb+Pb p+p

Collision rate 3kHz (8kHz peak) 1GHz

Event rate 3kHz (8kHz peak) 32MHz

Output bandwidth 100 GByte/sec 100 GByte/sec

Rejection none 99.7%

CMS Trigger+DAQ in Pb+Pb vs p+pCMS Trigger+DAQ in Pb+Pb vs p+p

Level 1 trigger- Uses custom hardware- Muon tracks + calorimeter information- Decision after ~ 3μsec

High level Trigger- ~1500 Linux servers (~10k CPU cores) - Full event information available- Runs “offline” algorithms


Trigger/DAQ ArchitectureTrigger/DAQ Architecture

Standard rack serversDual CPU - dual core2008/09: quad/8 core

~1500 “Filter Unit” servers~12000 1.8GHz Opteron equivalent

8 “DAQ slices”modular


High Level Trigger SimulationsHigh Level Trigger Simulations

Production

X-sections

Luminosity Ncoll Acc(y,pT) Eff(y,pT)

Acceptance, BR Efficiency

1 + Bkg/Sig(y,pT)

Trigger Table x

DAQ rateSignal rate

d2/dydpT

Trigger rate(signal + bkg)Rate to tape

Productionrate

Acceptance, efficiency, backgroundsmeasured and parametrized from full offline simulation + algorithms

Output Rates to tape

Timing of offline algorithms and event sizebias measured on full simulations


Minimum bias vs HLTMinimum bias vs HLT

Rates to tape

Significance(106 sec @ design lumi)

HLT CPU time Budget ~ 8 CPUsecper event(1.8GHz Opteron)

Strawman triggertable for design lumi

with HLT

Min bias

with HLT

Min bias


Activities of HI physicistsActivities of HI physicistsExploration of the capabilities of CMS as a heavy ion detector and preparations for data taking

Development of analysis tools and reconstruction algorithms

Development of generators Reconstruction algorithms

Development of trigger algorithms HLT Farm operations Trigger algorithms

Simulation studies Studies of detector behavior in HI collisions

Design and construction of “HI motivated” detectors

Zero Degree Calorimeter CASTOR


Heavy Ion Physicists within CMS CollaborationHeavy Ion Physicists within CMS Collaboration

Overall CMS Collaboration 38 Countries, 181 Institutions, ~2500 Scientists

Heavy Ion Institutions Athens, Auckland, Budapest, CERN, Chongbuk,

Colorado, Cukurova, Ioannina, Iowa, Kansas, Korea, Lisbon, Los Alamos, Lyon, Maryland, Minnesota, MIT, Moscow, Mumbai, Seoul, Vanderbilt, UC Davis, UI Chicago, Vilnius, Zagreb

Total of about 65 PhDs, 35 Students, 50% from the US


Physics PlanPhysics Plan Comprehensive heavy ion physics program with emphasis on hard probes Program follows increasing luminosity

Continuously extend pT range New probes Increase level of precision and detail Tighten and optimize trigger

Pb+Pb for the first few years, expect other ions and p+Pb later, in close coordination with ALICE

Detailed studies of rare channels

Extensive studies of rare channels, centrality, event plane dependence of quarkonia, tagged jets, heavy quarks

Detailed jet fragmentation studies, multi-jets, quarkonia physics, first tagged jet studies, detailed open b,c studies

Centrality and event plane dependence of global obs., charged particle spectra to 200 GeV, multi-100 GeV jets, open b,c, first quarkonia

Reference p+p, global observables, jets ET<200 GeV, charged particle spectra, first dimuon events,

Preparations: HLT, Reconstruction, first p+p physics at low energy

Physics (known physics)

55k2013

35k2012

15k2011

3k2010

0.3 k2009

02008

Total on tape

Calendar Year


ConclusionsConclusions

LHC will extend energy range and in particular high pT reach of heavy-ion physics

CMS is preparing to take advantage of its capabilities Excellent rapidity and azimuthal coverage and high resolution

Quarkonia Jets

Centrality, Multiplicity, Energy Flow reaching very low pT

Essentially no modification to the detector hardware New High Level Trigger algorithms specific for A+A Zero Degree Calorimeter, CASTOR and TOTEM will be important

additions extending forward coverage Heavy-Ion program is well integrated into the overall CMS

Physics Program The knowledge gained at RHIC will be extended to the

new energy domain

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Heavy-Ion Physics with Compact Muon Solenoid at Large Hadron Collider Bolek Wyslouch Massachusetts...

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