Heavy-Ion Physics with Compact Muon Solenoid at Large Hadron Collider Bolek Wyslouch Massachusetts Institute of Technology Los Alamos 25 October 2007 CMS

October 25, 2007Los Alamos Bolek Wyslouch2 Quark Gluon Plasma n Data from SPS & RHIC show new and unexpected properties of hot nuclear matter n Jet quenching, strong elliptical flow, d+Au- control data indicate that we have produced strongly interacting color liquid n LHC will significantly increase energy density l New properties of the plasma u Continuation of strong coupling regime? u Weakly interacting Plasma? l New tools to study to hot and dense state u Hard probes u Access to very low-x

October 25, 2007Los Alamos Bolek Wyslouch3 Summary of physics opportunities n LHC will accelerate and collide heavy ions at energies far exceeding the range of existing accelerators l The increase of beam energy will result in: u Extended kinematic reach for pp, pA, AA u New properties of initial state, saturation at mid-rapidity u A hotter and longer lived partonic phase u Increased cross sections and availability of new hard probes n New energy regime will open a new window on hot and dense matter physics: another large energy jump! AGSSPSRHICLHC  s NN [GeV] E increasex4x10x28 y range  1.6  3.0  5.3  8.6

October 25, 2007Los Alamos Bolek Wyslouch4 Large Hadron Collider n LHC is about to start operations: l 2008: u proton-proton collisions at ~14 TeV l 2008: u p+p at 14 TeV u Pb+Pb at 5.5 TeV per nucleon pair n Heavy Ions l Expect ~1 month of heavy ion collisions each year Beam Energy

October 25, 2007Los Alamos Bolek Wyslouch5 Rapidity Density PHOBOS Central Au+Au (200 GeV) Compilation by K. Eskola Color Glass Kharzeev & Levin, Phys. Lett. B523 (2001) 79 Data: PHOBOS, Phys. Rev. Lett. 87, (2001) From Eskola, QM 2000 First RHIC Surprise: Multiplicities Are “Low” n Low, that is, compared to pre-data predictions of “cascading partons” n Consistent with predictions based on gluon saturation :

October 25, 2007Los Alamos Bolek Wyslouch6 LHC? Extrapolated to LHC: dN/d  ~ LHC 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?

October 25, 2007Los Alamos Bolek Wyslouch7 RHIC’s Two Major Discoveries n Discovery of strong “elliptic” flow: l Elliptic flow in Au + Au collisions at √s NN = 130 GeV, STAR Collaboration, (K.H. Ackermann et al.). Phys.Rev.Lett.86: ,2001K.H. Ackermann et al.Phys.Rev.Lett.86: ,2001 l 307 citations n Discovery of “jet quenching” l Suppression of hadrons with large transverse momentum in central Au+Au collisions at √s NN = 130 GeV, PHENIX Collaboration (K. Adcox et al.), Phys.Rev.Lett.88:022301,2002K. Adcox et al.Phys.Rev.Lett.88:022301,2002 l 357 citations Flow strength Suppresion Factor Strongly interacting liquid with very low viscosity

October 25, 2007Los Alamos Bolek Wyslouch8 Elliptic Flow at RHIC Flow (asymmetry in p T ) is near to hydrodynamic limit, LHC: can it grow even more ? STAR HYDRODYNAMICS Flow

October 25, 2007Los Alamos Bolek Wyslouch9 “Jet Quenching” at high p T : will it continue at LHC ? p+p Au+Au n n Energy loss of partons in hot and dense matter n n E.g. charged particle R AA for multi-100 GeV/c p T Parton Energy loss

October 25, 2007Los Alamos Bolek Wyslouch10 Quarkonia 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 ? RHIC LHC Energy Density

October 25, 2007Los Alamos Bolek Wyslouch11 Post-RHIC Dream heavy-ion detector n Large acceptance for charged and neutral hadrons, muons, photons, electrons covering wide p T range hermeticity n Good resolution for high p T probes (jets, J/ ,  family) resolution n Good trigger to allow selection of rare events speed Good particle identification  0, b-, c-quarks, muons, electrons, photons, , K s, , K, p particle ID n Most likely it does NOT have to handle extreme multiplicities n Relatively low luminosity of LHC as a heavy-ion accelerator  CMS

October 25, 2007Los Alamos Bolek Wyslouch12 “High density QCD with heavy-ions” D.d'E (ed.) CERN-LHCC ; J.Phys.G. to appear. 170 pages 10 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

October 25, 2007Los Alamos Bolek Wyslouch13   Calorimeters: high resolution and segmentation Hermetic coverage up to |  |<5 (|  |<6.6 with the proposed CASTOR) Zero Degree Calorimeter   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 ~>0.3 GeV Pixel occupancy: <2% at dN ch /d   3500  p/p  1-2% for 1<p T <100 GeV Good low p T reach using pixels Functional at the highest expected multiplicities: studied in detail at dN ch /d   and cross-checked at DAQ and Trigger – – High rate capability for A+A, p+A, p+p – – High Level Trigger: real time HI event reconstructionCASTOR (5.2 < |η| < 6.6) ZDC (z =  140 m, |η| > 8.2 neutrals) CMS, as a heavy ion experiment

October 25, 2007Los Alamos Bolek Wyslouch14 CMS coverage HCAL (Barrel+Endcap+Forward) |  | < 3.0 ECAL + HCAL 3.0< |  | < 5.2 Forward HCAL 8.2 < |  | ZDC (neutrals) 5.2 < |  | < 6.6 CASTOR |  | < 2.4 Tracker, muons CoverageSub detector Q2Q2

October 25, 2007Los Alamos Bolek Wyslouch15 Silicon Tracker CMS under construction Hadron Calorimeter Electromagnetic Calorimeter Si tracker & Pixels Muon Absorber DAQ

October 25, 2007Los Alamos Bolek Wyslouch16 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 (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

October 25, 2007Los Alamos Bolek Wyslouch17 Zero Degree Calorimeter

October 25, 2007Los Alamos Bolek Wyslouch18 CASTOR: Tungsten-Quartz 5.2 < η < 6.6 T2 Tracker TOTEM 5.2 < η < 6.6 CASTOR

October 25, 2007Los Alamos Bolek Wyslouch19 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 or larger than dN ch /d  =5000 n n high granularity pixel detectors n n pulse height measurement in each pixel reduces background n n Very low p T reach, p T >26 MeV (counting hits) W. Busza, CMS Workshop, June 2004 Simple extrapolation from RHIC data

October 25, 2007Los Alamos Bolek Wyslouch20 Elliptic Flow measurements in CMS Use calorimeters and tracker Event plane reconstruction v 2 measurements Very large acceptance v 2 (  ) tracker

October 25, 2007Los Alamos Bolek Wyslouch21 Jets at RHIC nucleon parton jet Find this……….in this

October 25, 2007Los Alamos Bolek Wyslouch22 Production of QCD jets c d a b c d a b Proton-protonIon-ion “Clean” JetQuenched, absorbed, modified jet 2008->2009-> “Hard QCD” “Soft QCD”

October 25, 2007Los Alamos Bolek Wyslouch23 nhit > 12 pchi2 > 0.01 dca <3 Efficiency o o Fake Rate High-p T (leading) charged hadrons Excellent tracking performances (PbPb, dN ch /d  = 3500): Momentum resolution Impact parameter resolution Expected dN/dp T reach p T ~300 GeV/c (high E T HLT) C.Roland, CMS-AN Displaced vertexes from heavy-Q decays measurable

October 25, 2007Los Alamos Bolek Wyslouch24 Pixel Tracking, low p T reach of CMS Pixel trackingAll tracker fitting 800 MeV

October 25, 2007Los Alamos Bolek Wyslouch25 Pixel tracking Track finding efficiency vs p T and  for p+p and central Pb+Pb Fakes are controlled using pixel hit shape F. Sikler

October 25, 2007Los Alamos Bolek Wyslouch26 High-p T (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: dN g /dy~O(2-4 · 10 3 ) - Medium transport coefficient: ~O(10-100) GeV 2 /fm extended reach ~300 GeV/c w/ high-E T (jet)trigger PbPb (PYQUEN) 0.5 nb -1 C.Roland et al., CMS-AN06-110

October 25, 2007Los Alamos Bolek Wyslouch27 Pb-Pb full jet reconstruction Iterative-cone + backgd subtraction. [New developments (fast-K T ) 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

October 25, 2007Los Alamos Bolek Wyslouch28 Pb-Pb full jet reconstruction Jet spectra up to E T ~ 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-AN I. Lokhtin et al., PLB567 (03)39 Gluon radiation: large-angle (out-of-cone) vs. small-angle emission N jets ~6 · 10 6

October 25, 2007Los Alamos Bolek Wyslouch29  -,  *-, 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 Z 0 /  * Away side C.Mironov et al. N Z-jet ~10 3 p T >25 GeV/c  r =50  m   =20  m 3  vtx. cut

October 25, 2007Los Alamos Bolek Wyslouch30 E T  o - E T Jet (GeV) Events/ 5 GeV E Tjet,  > 120GeV in Barrel, 1 month at cm -2 s -1 Pb+Pb , Z 0 Jet Balancing  or Z 0 /  * vs Jets n Jet quenching with calibrated energy On average Z/  E T and jet E T should balance (unquenched jets) Z ->  and  can be reconstructed with very good E T resolution l Dominated by quark jets q + g -> q + Z 0 /   -Jet: Need to control the background from leading  0 in QCD dijets Reject  0 by cluster isolation cuts in the calorimeters l Quenching will help u Lower Thresholds n Z 0 - Jet l Cleaner but lower rates dN/dy ~7000, unquenched Jets new studies to appear shortly

October 25, 2007Los Alamos Bolek Wyslouch31 Quarkonia: probe of high-density QCD media n Dissociation (color screening) = hot QCD matter thermometer n Probe of low-x gluon structure/evolution: Lattice QQ free energy vs T: Spectral function vs T: Suppression pattern vs    [H.Satz, hep-ph/ ] production via gg fusion: x~10 -3 (10 -5 ) Q 2 ~10 GeV 2 gluon saturation, non-linear QCD _

October 25, 2007Los Alamos Bolek Wyslouch32 Heavy 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  ->    -

October 25, 2007Los Alamos Bolek Wyslouch33 J/ψ suppression J/  acceptance Best mass LHC p T reach (0.5 nb -1 ) SPS suppression ? regeneration ? RHIC LHC Energy Density  = 35 MeV/c 2 J/   ' S/B O.Kodolova, M. Bedjidian, CMS-AN N J/  ~1.8 · 10 5 |y|<1

October 25, 2007Los Alamos Bolek Wyslouch34  suppression  suppression  acceptance  ’/  stat. reach (HLT)  = 54 MeV/c 2  ’’  ’’  family S/B Best mass LHC p T reach (0.5 nb -1 )  spectroscopy (seq. suppr.) O.Kodolova, M. Bedjidian, CMS-AN Strong models constraint N  ~2.5 · 10 4 Gunion&R.Vogt

October 25, 2007Los Alamos Bolek Wyslouch35 Bolek Wyslouch Ultra-Peripheral collisions  Pb n Quarkonia photoproduction n Probes nuclear PDF in unexplored (x,M 2 ) range n Uses ZDC to trigger on forward emitted neutrons Measurement  -->  +  -, e + e - in the central detector

October 25, 2007Los Alamos Bolek Wyslouch36 CMS Trigger and DAQ in p+p Level-1 p+p Collision rate1GHz Event rate32MHz Output bandwidth100 GByte/sec Rejection99.7% Level 1 trigger - Uses custom hardware - Muon tracks + calorimeter information - Decision after ~ 3 μsec High Level Trigger p+p Input event rate100kHz Output bandwidth225 MByte/sec Output rate150Hz Rejection99.85% High level Trigger - ~1500 Linux servers (~10k CPU cores) - Full event information available - Runs “offline” algorithms

October 25, 2007Los Alamos Bolek Wyslouch37 High Level Trigger Pb+Pbp+p Input event rate3kHz (8kHz peak)100kHz Output bandwidth225 MByte/sec Output rate10-100Hz150Hz Rejection %99.85% Level-1 Pb+Pbp+p Collision rate3kHz (8kHz peak)1GHz Event rate3kHz (8kHz peak)32MHz Output bandwidth100 GByte/sec Rejectionnone99.7% CMS Trigger+DAQ in Pb+Pb vs p+p Level 1 trigger - Uses custom hardware - Muon tracks + calorimeter information - Decision after ~ 3 μsec High level Trigger - ~1500 Linux servers (~10k CPU cores) - Full event information available - Runs “offline” algorithms

October 25, 2007Los Alamos Bolek Wyslouch38 Trigger/DAQ Architecture Standard rack servers Dual CPU - dual core 2008/09: quad/8 core ~1500 “Filter Unit” servers ~ GHz Opteron equivalent 8 “DAQ slices” modular

October 25, 2007Los Alamos Bolek Wyslouch39 High Level Trigger Simulations Production X-sections LuminosityN coll Acc(y,p T )Eff(y,p T ) Acceptance, BREfficiency 1 + Bkg/Sig(y,p T ) Trigger Table x DAQ rate Signal rate d 2  /dydp T Trigger rate (signal + bkg) Rate to tape Production rate Acceptance, efficiency, backgrounds measured and parametrized from full offline simulation + algorithms Output Rates to tape Timing of offline algorithms and event size bias measured on full simulations

October 25, 2007Los Alamos Bolek Wyslouch40 Minimum bias vs HLT Rates to tape Significance (10 6 design lumi) HLT CPU time Budget ~ 8 CPUsec per event (1.8GHz Opteron) Strawman trigger table for design lumi with HLT Min bias with HLT Min bias

October 25, 2007Los Alamos Bolek Wyslouch41 Activities of HI physicists n Exploration of the capabilities of CMS as a heavy ion detector and preparations for data taking l Development of analysis tools and reconstruction algorithms u Development of generators u Reconstruction algorithms l Development of trigger algorithms u HLT Farm operations u Trigger algorithms l Simulation studies u Studies of detector behavior in HI collisions n Design and construction of “HI motivated” detectors l Zero Degree Calorimeter l CASTOR

October 25, 2007Los Alamos Bolek Wyslouch42 Heavy Ion Physicists within CMS Collaboration n Overall CMS Collaboration l 38 Countries, 181 Institutions, ~2500 Scientists n Heavy Ion Institutions l 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 l Total of about 65 PhDs, 35 Students, 50% from the US

October 25, 2007Los Alamos Bolek Wyslouch43 Physics Plan n Comprehensive heavy ion physics program with emphasis on hard probes n Program follows increasing luminosity l Continuously extend p T range l New probes l Increase level of precision and detail l Tighten and optimize trigger n 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 E T <200 GeV, charged particle spectra, first dimuon events, Preparations: HLT, Reconstruction, first p+p physics at low energy Physics (known physics) 55k k k k k Total  on tape Calendar Year

October 25, 2007Los Alamos Bolek Wyslouch44 Conclusions n LHC will extend energy range and in particular high p T reach of heavy-ion physics n CMS is preparing to take advantage of its capabilities l Excellent rapidity and azimuthal coverage and high resolution u Quarkonia u Jets l Centrality, Multiplicity, Energy Flow reaching very low p T l Essentially no modification to the detector hardware l New High Level Trigger algorithms specific for A+A l Zero Degree Calorimeter, CASTOR and TOTEM will be important additions extending forward coverage l Heavy-Ion program is well integrated into the overall CMS Physics Program n The knowledge gained at RHIC will be extended to the new energy domain