Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 1

Heavy Ion Physics with CMS:Day-One Measurements

Olga Barannikovafor the

CMS Collaboration

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 2

Outline

CMS Detector Components, Acceptance, Capabilities

Heavy Ion Program in CMSTriggering

Advantages of HLT

Day-One physics expectations Low-pT tracking PID Capabilities

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 3

CASTORCASTOR

T2T2

Collar Collar shieldingshielding

Forward DetectorsForward Detectors

(5.2 < < 6.5)

TOTEMTOTEM

ZDCZDC

(5.3 < < 6.7)

(z = 140 m)

BeamsBeams

EMEM

HADHAD

The CMS Detector

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 4

4T Field

Particle Detection in CMS

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 5

Heavy Ion Events in CMS

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

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

Pixels InnerStrips

OuterStrips

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 6

From RHIC to LHC

Factor 30 increase in energy to √sNN=5.5 TeV Gluon Saturation – even at =0 High Luminosity Large Cross sections

New high pT reach Directly identifiable jets J/ψ, Z0 and -family production

Baier,hep-ph/0310274

RHIC

Vogt, hep-ph/0205330

LHC

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 7

Heavy Ion Program @ CMSHard probes Quarkonia Forward

PhysicsForward Physics

Limiting Fragmentation, Saturation, CGC Ultra-peripheral Collisions – PDF in New Regions of x and Q2

High pT and Quarkonia

Jet Quenching, Energy Loss Mechanisms, FF Modifications Calibrated probes of Energy Loss - , Z0, Jet-, Jet-Z0, Quarkonia (J/, ) and Heavy Quarks – Suppression and Recombination

Soft Sector

Centrality and good Event Selection (Npart, Ncoll)

Charged Particle Multiplicity – Initial State Gluon Densities Azimuthal Asymmetry (Flow) – EoS Spectra + Correlations – Sources, Radial Flow, dE/dx and Quenching

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 8

Background: dNch/dy ~ 5000

Jet Reconstruction

Jet resolution: 0.032 0.028 16 %

pp (pileup subtracted)

Jet in Pb + Pb after pileup subtraction

CMS NOTE 2006/050

Jet ET ~100 GeV

Iterative jet cone-finder algorithm

with -dependent Event-by-Event background subtraction

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 9

Jet Reconstruction

Vardanyan

Eff

icie

ncy,

Pu

rity

,%Je

t E

nerg

y R

esol

uti

on, %

Fragmentation functions

Di-jet correlations

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 10

QuarkoniaKodolova, BedjidianSPS

RHIC

LHC?= 35 MeV/c2

Charm spectral suppression vs. T

CMS - The best experiment for mass

spectra measurements of the upsilon family

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 11

Di-Muon Reconstruction

Kvatadze

Mironov

Z0- can be reconstructed with high efficiency

Z0 production will probe nuclear shadowing and parton energy loss

Jet quenching with “calibrated” jets Low background compared to 0-noisy -

jetsZ0 – jet: Cleaner but lower rates

dN/dy ~7000, > 120GeV in Barrel

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 12

CMS HLTPhysics Enhancement with

HLT

In HLT: Centrality, Event Plane, Vertex Position, dN/dET, Ejet, Muon Tracks…

Statistical Significance – 1 Year

Production Rates in Pb+PbC.Roland, Veres

Day-One Measurements

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 13

High pT Suppression/Tracking I. Vitev and M. Gyulassy, PRL 89 (2002)

Inclusive pT Spectra vs. Centrality Nuclear Modification Factors (RAA, Rcp) 200 GeV/c reach based on

Production Rates + HLT

C. Roland

pT [GeV/c]

Res

olu

tio

n (

%)

Momentum Resolution

• Efficiency

o Fake Rate

pT [GeV/c]Efficiency/Fake-rate

(%

)

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 14

Global Physics

Event by Event dN/d and dE/dHit Counting and Tracklets in Pixels

Energy measurements 5.2 (HF) 6.5 (CASTOR)

ch

Extrapolation from RHIC

Silicon TrackerHigh granularity pixel detectorsPulse height in individual pixelsVery low pT reach, pT ~ tens of MeV/c

dE() in adc units

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 15

Elliptical Flow

Reaction Plane

= 0.12 rad

CMS:

RHIC

Reaction plane (R)

x

z

y

xy

z

Petrushanko

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 16

Tracking Performance at Low pT

Tracker

Low pT Tracking Extension with Three Pixel Layers

Efficiency

Fake Rate

Pixel Tracking

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 17

PID Capabilities

dE/dx and Topology (V0):

Pb+Pb @ 5.5GeV ~ high-luminosity minimum bias pp @ 14TeV

CMS NOTE AN-2006/101

The truncated mean dE/dx vs. p

Ferenc Siklér

Olga BarannikovaWinter Workshop on Nuclear Dynamics, 2007 18

Summary

CMS is:…designed for excellent performance in hard sector

…has unique forward physics capabilities

…a detector with a sophisticated trigger for extended physics reach

….has surprising ability for global/soft physics

…. all of the above

Coverage

Jet Physics Quarkonia

Z0

(Nch, ET) vs. EbyE physics

RAA @ 200 GeV/cIn one year of running