1. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 1 Heavy Ion Physics with the CMS Experiment at the LHC Gábor Veres Eötvös Loránd University, Budapest, Hungary Massachusetts Institute of Technology, Cambridge, USA for the CMS Collaboration Strangeness in Quark Matter ’06 UCLA, California, March 26, 2006 CMS HI groups: Adana, Athens, Basel, Budapest, CERN, Demokritos, Dubna, Ioannina, Kiev, Krakow, Los Alamos, Lyon, MIT, Moscow, Mumbai, New Zealand, Protvino, PSI, Rice, Sofia, Strasbourg, U Kansas, Tbilisi, UC Davis, UC Riverside, UI Chicago, U Iowa, Yerevan, Warsaw, Zagreb

2. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 2 Physics opportunities at the LHC  LHC: a large increase in collision energy compared to existing accelerators: Extended kinematical reach (y, p T ) for p+p, p+A, A+A collisions New properties of initial state, saturation even at mid-rapidity A hotter and longer lived partonic phase Increased cross sections of hard probes, heavy quarks Last but not least: unknown territory/surprises?  New energy regime will open a new window on hot and dense matter physics: another large energy jump! AGSSPSRHICLHC (Pb+Pb)  s NN [GeV] 5172005500 increase in  s NN  3-4  12  28 y range  1.6  2.9  5.4  8.7

3. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 3 Heavy Ion Physics Topics at the LHC  High p T : modification by the medium Copious production of high p T particles Large jet production cross section  RHIC LHC RHIC LHC J/ψ  Different “melting” for the  family members, depending on binding energy Large production cross section for the J/ψ and  family  Correlations, scattering in medium jets clearly identifiable, for the first time in heavy ion collisions

4. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 4 CMS, as a heavy ion experiment  Calorimeters: high resolution and segmentation Hermetic coverage up to |  |<5 (|  |<7 with the proposed CASTOR) Zero Degree Calorimeter (approved)  Muon tracking:  from Z 0, J/ ,  Wide rapidity coverage: |  |<2.4 σ m  50 MeV at the  mass in the barrel  Silicon Tracker Good efficiency and purity for p T >1 GeV Pixel occupancy: <2% at dN ch /d   3500  p/p  2% for p T <70 GeV Functional at the highest expected multiplicities: studied in detail at dN ch /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 CASTOR (5.32 < η < 6.86) ZDC (z =  140 m)

5. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 5 HLT Lvl-1 Data Acquisition and Trigger  Level 1 hardware trigger Muon track segments Calorimetric towers No tracker data Output rate (Pb+Pb): 1-2 kHz comparable to collision rate  High level trigger Full event information available Every event accepted by L1 sent to an online farm of 2000 PCs Output rate (Pb+Pb):  40 Hz Trigger algorithm: similar to offline reconstruction - Every event must pass the whole chain - Selectivity depends on available CPU power switch

6. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 6 Centrality and forward detectors Energy in the forward hadronic calorimeter Zero Degree Calorimeter Tungsten-quartz fibre structure electromagnetic section: 19X 0 hadronic section 5.6λ 0 Rad. hard to  20 Grad (AA, pp low lum.) Energy resolution:  10% at 2.75 TeV Position resolution:  2 mm (EM sect.) Centrality (impact parameter) determination is needed for physics analysis impact parameter [fm] E T [GeV] Pb+Pb

7. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 7 Charged 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 to dN ch /d  5000  high granularity pixel detectors  pulse height measurement in each pixel reduces background  Very low p T reach, p T >26 MeV (counting hits) W. Busza, CMS Workshop, June 2004 Simple extrapolation from RHIC data

8. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 8 Track reconstruction Momentum Resolution [%] Transverse Impact Parameter Resolution [cm] (Event sample: dn/dy  3000 + one 100GeV jet/event) Excellent performance, even at the highest particle densities Efficiency and fake rate [%] -0.5<  <0.5 2.0<  <2.5 -0.5<  <0.5 2.0<  <2.5 -0.5<  <0.5 efficiency fake rate %

9. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 9 Quarkonia in CMS Heavy Ions J/  acceptance J/   family M  +  - spectrum,  family   Y =50 MeV in the barrel Expected:  24000 J/  and ~ 18000/5000/3000  /  ’/  ’’ After one month of Pb+Pb running at L =10 27 cm -2 s -1 with 50% efficiency Online HLT farm improves acceptance by  2.5 at high  and low p T

10. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 10 Jets – a new observable at LHC  Hard, perturbative scale: Q>>  QCD. Hard parton production unaffected by medium  Parton shower development affected by the medium  At LHC in Pb+Pb collisions: wider p T range for suppression, quenching studies jet structure will likely be modified, compared to jets produced in p+p comparison to p+p and p+A is essential  Observables: High p T particles and particle correlations (similar to RHIC analyses) Jet rates: single and multi-jets (quenching studies) Jet fragmentation and shape: Distance R to leading particle (in  -  space) forward-backward correlation:  (particle, jet axis) Fragmentation function: F(z)=1/N j  dN ch /dz where z=p t /p jet correlations with non-hadronic particles: jets+ , jets+Z Jets originating from heavy quarks (b, c) c d a b Extensive theoretical and experimental preparatory work presently in progress

11. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 11 Jet reconstruction in the calorimeters |  |<0.3 1.6<|  |<1.9 |  |<0.3 1.6<|  |<1.9 resolution efficiency

12. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 12 Jet studies using the tracking Centrality dependence of p T specra can be studied: Azimuthal correlations (as studied at RHIC): Fragmentation functions: p T with respect to jet axis: Tracking is a very important capability for jet physics dN/dp T 1/N jets dN ch /dz 1/N jets dN ch /dp T jet dN/d(  )

13. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 13 Advantages of CMS over other HI experiments CASTOR TOTEM ZDC (5.32 < η < 6.86) (z =  140 m)  Hermeticity, Resolution, Granularity Central region: tracker, electromagnetic and hadronic calorimeters and muon detector  Forward coverage calorimeters extend to  10 Proposed CASTOR calorimeter to  14  High data taking speed and trigger versatility Two-level trigger Ability to “inspect” every heavy ion event on the High Level Trigger computer farm

14. Gábor Veres Strangeness in Quark Matter ‘06, UCLA, March 26, 2006 14 CMS under construction… Hadron Calorimeter Electromagnetic Calorimeter Si tracker & Pixels Muon Absorber DAQ Solenoid superconducting, already at 4K