1. Pablo Yepes, Rice U 0 HI May 19, 2001May 19, 2001. CMS Heavy Ion Physics Pablo Yepes Rice University oHadronic Collisions sQuarkonia Production sJet Collisions oCoherent Interactions

2. Pablo Yepes, Rice U 1 HI May 19, 2001May 19, 2001. Why HI at LHC Jurgen Shukraft, Quark Matter 2001 Pb+Pb, central collisions (b=0) Pb Before After

3. Pablo Yepes, Rice U 2 HI May 19, 2001. J/  Melting L(fm): Average distance travel by the J/  inside tNuclear Matter. J/  Yield u,d c Hadron gas J/J/ K ++ -- u,d c QGP ud d NA50 Collaboration, CERN

4. Pablo Yepes, Rice U 3 HI May 19, 2001May 19, 2001. Quarkonia Acceptance in CMS  Chambers 10% 20% Acceptance J/  at CMS Upsilon at CMS P t (GeV) Full Detector Barrel CMS: J/  mainly p T >5 GeV with barrel, due to  cutoff. ALICE:  >2.5 with  ATLAS (if they do HI) lower acceptance due to higher  p T cutoff.

5. Pablo Yepes, Rice U 4 HI May 19, 2001May 19, 2001. Quarkonia Reconstruction oEssential sub-detectors: sTracking devices sMuon system oPessimistic assumptions for background estimates: sdN ch /dy=8000 (most generators < 5500)    GeV/c (HIJING 0.39 GeV/c)   k =0.67 GeV/c Special Heavy Ion Tracking Algorithm Significant Muon background from  and K decays

6. Pablo Yepes, Rice U 5 HI May 19, 2001May 19, 2001. J/  Signal 1 month running at top Luminosity: J/  ’s detected and reconstructed in the Barrel: 10 3 4 22.252.52.7533.253.53.7544.254.5 Min bias collisions - 1 month run - barrel only muons with P > 3.5 GeV/c Pb-Pb  /cont.= 1.0 # events/25 MeV/c 2 10 4 5 22.252.52.7533.253.53.7544.254.5 Ca-Ca  /cont.= 9.7 Opposite-sign di-muon invariant mass (GeV/c 2 ) L= 2.5 10 29 cm 2 s -1 # events/25 MeV/c 2 L= 10 27 cm 2 s -1 ALICE: ~2K events with  s

7. Pablo Yepes, Rice U 6 HI May 19, 2001May 19, 2001. 1 month: 22000  and 7500  ’ detected in the barrel Upsilon in Pb-Pb Opposite-sign di-muon Invariant Mass (GeV/c 2 ) Background contributions # Events/25 MeV/c 2

8. Pablo Yepes, Rice U 7 HI May 19, 2001May 19, 2001. Upsilon in Ca-Ca 1 month: 340000  115000  ’ Only barrel used.

9. Pablo Yepes, Rice U 8 HI May 19, 2001May 19, 2001. Upsilon’/Upsilon ratio as a Thermometer (Ramona Vogt)

10. Pablo Yepes, Rice U 9 HI May 19, 2001May 19, 2001. Quarkonia Reference  At SPS, J/  is compared to Drell-Yan. oAt LHC Drell-Yan contribution is negligible. oZ 0 proposed as reference to  production. sM Z >M  sDifferent production mechanisms: < Z 0 : antiquark-quark, quark-gluon and antiquark-gluon. <  : gluon-gluon. oCross check di-muon reconstruction algorithm

11. Pablo Yepes, Rice U 10 HI May 19, 2001May 19, 2001. Jet Quenching Large p T quarks affected by hot hadronic media Jets at RHIC buried in low p T background Look at particle pt spectrum

12. Pablo Yepes, Rice U 11 HI May 19, 2001May 19, 2001. Jets at LHC are Easy for High Multiplicity PbPb omonojet/dijet enhancement  jet-Z 0   or jet-  dN ch /dy=8000 Total Calorimeter Energy   Jet Finding 100 GeV E T -  ~100% -  (E T )/E T =11.6%. Jet quenching

13. Pablo Yepes, Rice U 12 HI May 19, 2001May 19, 2001. Balancing Photons and Jets  E t jet,   120 GeV in the barrel o1 month: s900 events for Pb-Pb s10 4 events for Ca-Ca # Events/4 GeV E T  //  0 -E T Jet (GeV) =8 GeV =4 GeV =0 GeV Background 2 weeks at L=10 27 cm -2 s -1

14. Pablo Yepes, Rice U 13 HI May 19, 2001May 19, 2001. Ultra Peripheral Collisions (Coherent Interactions) oLow p T p T < 1/R  50 MeV  Low Energy E CM Max <  /R sCERN SPS E CM Max =0.5 GeV s RHIC E CM Max =6 GeV  Detected s CERN LHC E CM Max =160 GeV A A  or  P

15. Pablo Yepes, Rice U 14 HI May 19, 2001May 19, 2001. STAR Ultra-Peripheral Event (DNP 2000) End view AuAu    P (  Au)   Trigger: Low multiplicity and zero energy at Zero Degree Calorimeter (ZDC) Side view ZDC

16. Pablo Yepes, Rice U 15 HI May 19, 2001May 19, 2001.  Physics oNew Physics: sStandard Model H production marginal for HI  Any exotic particle coupling to . sSupersymmetric Higgs for some areas of parameters space.  Mainly studied at e + e - colliders.Typically  0 <m   c.  tot up to 70 GeV by LEP. oNon perturbative QED, coupling Z 2. e + e - Cross Sections

17. Pablo Yepes, Rice U 16 HI May 19, 2001May 19, 2001. events/sec/G eV 10 -14 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 10 0 10 10 0 2 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 10 10 2  AA (barn) events/sec M (GeV)    f 2 a 2 f 2 '  c   c0  c2  b  0b bb H SM H' 10 -5 10 -3 10 -1 10 10 3 10 5 10 7 events/year 11010 2 M (GeV) 10 14 10 12 10 10 8 10 6 10 4 10 2 1 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 1 10 2  AA (M) (barn/GeV) hadrons e+e-e+e-          cc bb 10 -5 10 -3 10 -1 10 10 3 10 5 10 7 events/year/GeV Ultra-Peripheral Collisions  Cross Sections Meson or lepton/quark pair A A A A 

18. Pablo Yepes, Rice U 17 HI May 19, 2001May 19, 2001.  Physics, Hadron Spectroscopy o Heavy quark spectroscopy. Very large numbers expected oLight quark: Difficult at CMS because of low p T, challenge for triggering, unless a multiplicity trigger is used.

19. Pablo Yepes, Rice U 18 HI May 19, 2001May 19, 2001. Photon Nucleus (  A)   p studied in HERA: W  p <200 GeV   A at LHC: W  p <900 GeV  Vector meson production:  p(A)  Vp(A), V= ,J/   Very large rates, for example >10 4 Hz  in Ca-Ca sInterface QCD and hadronic physics  LHC will be a meson factory. Competitive with other meson factories like  factory at Frascatti (CP, QM tests, etc). sCan CMS trigger on these events. Clean events with only a few tracks.

20. Pablo Yepes, Rice U 19 HI May 19, 2001May 19, 2001. Conclusions oCMS is provides unique tools to study Heavy Ion Collisions at LHC. oSome physics topics: sQuarkonium production:  and J/  families. sJet quenching. s Ultra-Peripheral collisions.

21. Pablo Yepes, Rice U 20 HI May 19, 2001May 19, 2001. Addendum: Tracking oDeveloped for dN ch /dy=8000 and dN 0 /dy=4000.  Track only particles with tracks in  detector.  Use  -chambers tracks as seeds. oUse only tracking detector providing 3D space points. Occupancy (%) 0 10 20 30 40 50 60 708090100110120 Detector Pitch  m MSGC 200 MSGC 240 Silicon 147 Radius of MSGC layer (cm)

22. Pablo Yepes, Rice U 21 HI May 19, 2001May 19, 2001. Interference oNuclei can emit or scatter pair stwo indistinguishable possibilities oAmplitudes add sVector meson has negative parity   ~ |A 1 - A 2 e ip·b | 2 < Destructive interference when p T << 1/b