Heavy Ion Physics at the LHC Frontier David

Heavy Ion Physics at the LHC Frontier David Hofman UIC Physics Fest 07

1. QCD: Answers why there are no free quarks Confinement (& asymptotic freedom) Experimental data and perturbative QCD (p. QCD) calculation Visualization of QCD by Derek Leinweber Centre for the Subatomic Structure of Matter (CSSM) and Department of Physics, University of Adelaide, 5005 Australia relative strength M. Schmelling hep-ex/9701002 asymptotic freedom distance energy density, temperature Separation of quarks varies from 0. 125 fm to 2. 25 fm (~1. 3 x diameter of proton) Energy Density, Temperature Distance http: //www. physics. adelaide. edu. au/theory/staff/leinweber/Visual. QCD/Improved. Operators/index. html UIC Physics Fest 07

2. QCD: The Properties of Vacuum QCD Fields Fluctuating in Empty Space Visualization of QCD: by Derek Leinweber (same references as earlier slide) Action Density (~Energy Density) Topological Charge Density (measure of winding of gluon field lines) Volume 2. 4 x 3. 6 fm 3 (Can hold a couple of protons) “Contrary to the concept of an empty vacuum, QCD induces chromoelectric and chromo-magnetic fields throughout space-time in its lowest energy state. ” - D. Leinweber UIC Physics Fest 07

QCD Vacuum & the Mass of Light Quarks Figure and quote From B. Muller; nucl-th/0404015 Current (or ‘naked’) Quarks Mass u, d = 5 -10 Me. V generated by Higgs condensate (weak interaction). Constituent Quarks Mass u, d ~ 300 Me. V generated by QCD condensate (strong interaction). “Because of the energy scales involved, only the QCD Vacuum is amenable to modification at energies accessible with present technologies. ” UIC Physics Fest 07

2. QCD and Einstein Idea From: F. Wilczek’s Nobel Prize Lecture “Does the Inertia of a Body Depend Upon its Energy Content? ” By A. Einstein September 27, 1905 (Annalen der Physik, 18, p 639 -641 ) Einstein and QCD say YES! Einstein also wrote in the same paper: “The mass of a body is a measure of its energy-content; … It is not impossible that with bodies whose energy-content is variable to a high degree … theory may be successfully put to the test. “ QCD says it is POSSIBLE at a very deep level. Change the energy property of vacuum such that the mass of fundamental particles is changed to the UICvalue Physicsgiven Fest 07 by the Higgs Condensate.

Condensate Melting the QCD Vacuum The condensate “melts” (Chiral Symmetry is ≈ restored) Energy Density Temperature quark-gluon plasma Deconfinement pion gas Temperature Critical “melting” Point UIC Physics Fest 07 (From Theory) Critical Temp, TC ~ 170 Me. V Critical Energy Density, e. C ~ 0. 7 Ge. V/fm 3

Putting Tc ~ 170 Me. V in Context… 1 e. V corresponds to an energy k. BT (where T~11, 600 K). Using Tc ~ 170 Me. V: (1. 7 x 108)(1. 16 x 104) ~ 2 x 1012 K To Melt the QCD Vacuum (and perhaps create a Quark-Gluon plasma) Need ~2 trillion degrees K 2 x 1012 K (or o. C) Too much heat to think about creating in a traditional sense. UIC Physics Fest 07

Reaching 2 trillion K in the laboratory… collide heavy nuclei near the speed of light (e. g. , v ~ 0. 99996 c) We believe these conditions will reach the necessary temperature and pressure (energy-density) to melt the QCD vacuum. UIC Physics Fest 07

History of Experiments BNL AGS (1986) s. NN 5 Ge. V (v~0. 98249 c) O+O, Si+Si, Au+Au CERN SPS (1986) s. NN 20 Ge. V (v~0. 99891 c) O+A, Pb+Pb BNL RHIC (2000) s. NN 200 Ge. V (v~0. 99996 c) Au+Au, d+Au, Cu+Cu UIC Physics Fest 07

A Heavy-Ion Au+Au Collision Note: Animation is not relativistic – i. e no Lorentz contraction Animation by Jeffrey Mitchell. UIC (Brookhaven National Laboratory) Physics Fest 07

One Central Au+Au collision at RHIC Beamline Total # of charged particles (central collision): 5060± 250 @ 200 Ge. V 4170± 210 @ 130 Ge. V 1680± 100 @ 19. 6 Ge. V Energy density at 200 Ge. V reached e 0 > 4 Ge. V/fm 3 UIC Physics Fest 07

What State of Matter are we Producing? 1. Almost baryon-free with thermalization and expansion 2. A “Liquid” with Quark Do. Fs 3. Strongly Interacting Matter UIC Physics Fest 07

Suppression of High Momentum Particles RAA(p. T) Peripheral Mid-Central (h++h-)/2 p 0 Phenix: Phys. Rev. C 69 (2004) 034910 See a strong suppression of. UIC high p yields in Au. Au Central Collisions Physics. T Fest 07

Suppression holds to high momentum… as far as we can measure at RHIC. V. Greene – PHENIX – QM 2005 RAA(p. T) PHENIX preliminary p 0 0 -10% Central Collisions p. T(Ge. V/c) UIC Physics Fest 07

Where have all the fast particles gone? They are only “missing” for central heavy-ion collisions. Could it be direct evidence we have created some type of quark-gluon-plasma that somehow “slows” fast moving particles down? Is there some type of strong energy-loss effect? Can do an even more detailed check → use direct signature of back-to-back JETS (or dijets)! UIC Physics Fest 07

“Fast” Probes of Dense Matter dijets in proton + proton collisions a jet Fig From: G. Roland a jet UIC Physics Fest 07

Back-to-back “jets” (dijets) at RHIC …in this Find this… STAR p+p jet+jet (STAR@RHIC) jet parton Au+Au ? ? ? (STAR@RHIC) nucleon UIC Physics Fest 07

Azimuthal dijet distributions in Au+Au STAR, PRL 91 (2003) 072304 STAR p+p Au+Au Peripheral Trigger “jet” 4 < p. T(trig) < 6 Ge. V/c p. T(assoc) > 2 Ge. V/c Opposite (away-side) “jet” UIC Physics Fest 07

Azimuthal dijet distributions in Au+Au STAR, PRL 91 (2003) 072304 p+p STAR Au+Au central Trigger “jet” 4 < p. T(trig) < 6 Ge. V/c p. T(assoc) > 2 Ge. V/c UIC Physics Fest 07 Away-side “jet” is MISSING in central Au+Au

Jet Quenching in our QCD matter There are many questions we can ask! • How to quantify and calculate this “energy loss”? • How does it depend on particle species? • Does it affect quarks differently from gluons? • How does it vary with energy density? • What happens for very, very high momentum particles? Animation by Jeffrey Mitchell (Brookhaven UIC Physics Fest 07 National Laboratory)

Towards the new Frontier… Study behavior at very high momentum Need More Energy! UIC Physics Fest 07

The LHC Frontier The Large Hadron Collider in CERN LHC √s. NN= 5. 5 Te. V (for Pb+Pb) (v ~ 0. 99999994 c) Energy is 28 x higher than RHIC. Geneva, Switzerland UIC Physics Fest 07

Three Major Detectors (all underground) ATLAS ALICE CMS UIC Physics Fest 07

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 m Tracker 2. 4 ECAL 3 HCAL UIC Physics Fest 07 5. 2 Beams

UIC Physics Fest 07

Extreme Engineering Lift up each “slice”… Lower ~50 m down… Then put it all together! UIC Physics Fest 07

Particle Detection in CMS Tracking + Ecal + Hcal + Muons for | |<2. 4 Si TRACKER Silicon Microstrips and Pixels CALORIMETERS ECAL Scintillating Pb. WO 4 crystals HCAL Plastic scintillator/brass UIC Physics Fest 07 sandwich MUON BARREL Drift Tube Resistive Plate Chambers (DT) Chambers (RPC)

Study: Heavy-Ion Tracking Performance at High p. T Momentum Resolution Track-Pointing Resolution 4. 0 o Fake Rate 250 3. 5 o 2. 0 < |h| < 2. 5 3. 0 st (mm) • Efficiency Resolution (%) Percentage (%) Efficiency/Fake-rate 2. 5 2. 0 1. 5 1. 0 • 0. 0< |h| < 0. 5 200 o 150 • 0. 0 < |h| < 0. 5 2. 0 < |h| < 2. 5 100 50 0 0 p. T [Ge. V/c] 0 -10% central Measure the high momentum “suppression” (if it exists at LHC energies) out past 250 Ge. V/c! [Compare to 20 Ge. V/c at RHIC] UIC Physics Fest 07 Statistical Reach (using HLT)

Study: Jet Reconstruction in Heavy Ion Collisions CALORIMETRY JET FINDING ALGORITHM FOR HI Subtract “background” Find jets with iterative cone algorithm Recalculate background outside cone + recalculate jet energy Efficiency, Purity Jet Energy Resolution ~18% 9% + TRACKING Pb+Pb d. Nch/d | =0~5000 + 100 Ge. V jets p. T with respect to jet axis: 1/Njetsd. Nch/dp. Tjet 1/Njetsd. Nch/dz Fragmentation functions: UIC Physics Fest 07 p. Tjet (Ge. V/c)

Novel Probes: Quarkonia (heavy quark states: cc & bb) SPS RHIC Kodolova, Bedjidian J/y LHC? s = 35 Me. V/c 2 Charm spectral suppression vs. T UIC Physics Fest 07 CMS - The best experiment for mass spectra measurements of the upsilon family

Final Thoughts • In the brief moment of a relativistic heavy-ion collision, we have created a new state of matter with extremely interesting properties. – One (of many) properties of this “Quark Gluon Plasma” found so far at RHIC Very strongly interacting – “A perfect liquid? ”. • Factor 5 reduction in high momentum particles • Quenching of one side of a dijet event – The Frontier: What happens at the LHC? • LHC “turns on” (with protons) at the end of this year. • First heavy-ions expected next summer. UIC Physics Fest 07