Heavy Ion Physics with CMS Dave Hofman UIC

Heavy Ion Physics with CMS Dave Hofman UIC for the CMS Collaboration Overall CMS Collaboration 38 Countries, 181 Institutions, ~2500 Scientists CMS Heavy-Ion Groups Athens, Auckland, Budapest, CERN, Chongbuk, Colorado, Cukurova, Iowa, Kansas, Korea, Los Alamos, Lyon, Maryland, Minnesota, MIT, Moscow, Mumbai, Rice, Seoul, Vanderbilt, UC Davis, UI Chicago, Zagreb HI Collaborators - 64 Ph. Ds, 35 Students Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 1

Brief (US-centric) History of Heavy Ions in CMS HI physics included in all CMS reports starting from first proposal. 1994 CMS HI started by Russian & French groups 2002 Entry of US groups* *Davis, LBNL, Rice already active in CMS HI – CMS Note 2000/060 2003 -2006 Greece, Hungary, India, Korea, N. Zealand, Turkey Recent Milestones 2006 - Proposal to Do. E for US HI@CMS 2006 – Successful ZDC Test Beam 2007 - CMS TDR for Heavy Ion Physics Table of Contents • Introduction • Global observables and event characterization • Low p. T hadron spectra • Elliptic Flow • Hard probes triggering capabilities • Quarkonia and heavyquarks • Jets and high-p. T hadrons • Ultraperipheral collisions Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 2

Heavy Ions in CMS Pb+Pb event (d. N/dy|y=0 = 3500) with - World-class capabilities in hard probes. Complementary (& surprising) abilities for soft physics and global observables. Unique opportunities and capabilities in forward region. + Sophisticated high-rate triggering to exploit and maximize physics output. Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 3

The Compact Muon Solenoidal Detector Forward Detectors Muons Si Tracker Ecal Forward Calorimeter (3 < | | < 5. 2) Hcal CASTOR (5. 2 < | | < 6. 5) TOTEM Collar shielding (5. 3 < | | < 6. 7) T 2 ZDC (| | > 8. 3, z = 140 m) Solenoid EM Return Yoke HAD Silicon and Tracker 2. 4 ECAL 3 Dave Hofman HCAL Phases of QCD Matter Town Meeting, 5. 2 Rutgers, Jan 12 -14 2007 Beams 4

Particle Detection in CMS Tracking + Ecal + Hcal + Muons for | |<2. 4 Si TRACKER Silicon Microstrips and Pixels Dave Hofman CALORIMETERS MUON BARREL ECAL HCAL Drift Tube Resistive Plate Scintillating Plastic scintillator/brass Chambers (DT) Chambers (RPC) Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 5 Pb. WO crystals sandwich 4

Tracking Performance at Low p. T Multiplicity (entries) Tracking at low p. T Si Tracker Pixel Detector Occupancy of < 2% Pixel Tracking All Tracker Fitting Including Pulse Height Information Low p. T Tracking Using Three Pixel Layers PID with d. E/dx and Topology (V 0) Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 6

Tracking Performance at High p. T Momentum Resolution Track-Pointing Resolution 4. 0 • Efficiency o Fake Rate 250 3. 5 o 2. 0 < |h| < 2. 5 3. 0 st ( m) Resolution (%) Percentage (%) Efficiency/Fake-rate 2. 5 2. 0 1. 5 1. 0 • 0. 0< |h| < 0. 5 o 150 • 0. 0 < |h| < 0. 5 2. 0 < |h| < 2. 5 100 50 0 0 p. T [Ge. V/c] 200 p. T [Ge. V/c] 0 -10% central Inclusive p. T Spectra vs Collision Centrality – Determine Nuclear Modification Factors RAA – Yield plus High Level Trigger will allow Measurement out to >200 Ge. V. Dave Hofman Statistical Reach (using HLT) Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 7

Jet Reconstruction CALORIMETRY JET FINDING ALGORITHM FOR HI Find jets with iterative cone algorithm Recalculate background outside cone + recalculate jet energy + TRACKING Jet Energy Resolution ~18% 9% Fragmentation functions: 1/Njetsd. Nch/dz d. N/d( ) Azimuthal correlations: Pb+Pb d. Nch/d | =0~5000 + 100 Ge. V jets Efficiency, Purity p. T with respect to jet axis: 1/Njetsd. Nch/dp. Tjet Subtract “background” Df (rad) Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 p. Tjet (Ge. V/c) 8

Quarkonia MUONS + TRACKING J/ s = 35 Me. V/c 2 family ’/ s = 54 Me. V/c 2 parton gas i ’ ’’ minijet ii parton gas ii Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 Statistical Reach (using HLT) 9

High Mass Di-Muons • • • Z 0 - reconstructed with high efficiency by design Dimuon continuum dominated by b decays High statistics g(*), Z 0 Dave Hofman 0 and Jet Balance Energies of g*/Z Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 10

Excellent Event Characterizations Forward HCal CASTOR “Spectators ” ZDC CASTOR Forward HCal ZDC “Spectators ” Event Selection and Centrality Determination ET [Ge. V] Energy in Forward HCal Dave Hofman Zero Degree Calorimeter Pb+Pb impact parameter [fm] Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 11

Forward Physics • Quarkonia photoproduction • Uses ZDC to trigger on forward emitted neutrons • Measurement -> m+m-, e+ein the central detector • Probes nuclear PDF in unexplored (x, Q 2) range Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 12

CMS Trigger Level 1 Trigger (LV 1) • Uses custom hardware • Muon chamber + calorimeter information • Decision after ~ 3 msec Level-1 Collision Rate Event Rate Output Bandwidth Rejection p+p Pb+Pb 1 GHz 3 k. Hz (8 k. Hz peak) 40 MHz 3 k. Hz (8 k. Hz peak) 100 GByte/sec 99. 7% none High Level Trigger (HLT) • ~ 1500 Linux servers (~12 k CPU cores) • Full event information available • Runs “offline” algorithms High Level Triger Dave Hofman Primary “hardware” task for CMS heavy ion running p+p Pb+Pb Input Event Rate 100 k. Hz 3 k. Hz (8 k. Hz peak) Output Bandwidth 225 MByte/sec Output Rate 150 Hz 10 -100 Hz Rejection 99. 85% 97 -99. 7% Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 13

Heavy Ion Trigger Strategy Maximize Physics Signals of Interest • Select all minimum bias Pb+Pb events at Level 1 • Send full event stream to the High Level Trigger • Run “offline” algorithms on every Pb+Pb event – Select Hard Probes embedded in highly complex events – Examples: Jet finding algorithm, dimuon reconstruction – Best selection needs full event information and complex algorithms Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 14

HLT Physics Enhancement Jet trigger and RAA Results for one full luminosity LHC heavy ion run (106 sec) 0 -10% central Minimum Bias Stream 0 -10% central Jet Trigger Stream More than 10 x Gain for Di-Muons (factors of 2 -3 for low-luminosity running) Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 15

Role of US Physicists • Leadership • RHIC experience • Physics Analysis • Triggering and Data Acquisition • Zero Degree Calorimeter • Offline Computing for Heavy Ions Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 16

Final Thoughts CMS is a Superb and Versatile Detector for Heavy Ion Physics at the LHC • Excellent performance in high p. T(ET) region and for m pairs – by design • Capability for global/soft physics • Unique forward physics capabilities & coverage • Sophisticated trigger will extend physics reach and allow us to focus on key physics issues • The detector and data acquisition are uniquely suited to the multipurpose nature of the LHC • The US Nuclear groups are providing leadership to the well established CMS HI effort • Extremely large physics return in a very short time-scale Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 17

Backups Dave Hofman Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 18

HLT Physics Enhancement Example Results for one full luminosity LHC heavy ion run (106 sec) Rates to Tape Dave Hofman Statistical Significance Phases of QCD Matter Town Meeting, Rutgers, Jan 12 -14 2007 19