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CMS Heavy Ion Physics

CMS Heavy Ion Physics. Pablo Yepes Rice University. Hadronic Collisions Quarkonia Production Jet Collisions Coherent Interactions. Why HI at LHC Jurgen Shukraft, Quark Matter 2001. Before. Pb. Pb. Pb+Pb, central collisions (b=0). After. J/ Y Melting. p -. J / Y. c c. Hadron

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CMS Heavy Ion Physics

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  1. CMS Heavy Ion Physics Pablo Yepes Rice University • Hadronic Collisions • Quarkonia Production • Jet Collisions • Coherent Interactions

  2. Why HI at LHCJurgen Shukraft, Quark Matter 2001 Before Pb Pb Pb+Pb, central collisions (b=0) After

  3. J/Y Melting p- J/Y c c Hadron gas K p+ u,d u,d c c d QGP d u u,d u,d NA50 Collaboration, CERN J/Y Yield L(fm): Average distance travel by the J/Y inside tNuclear Matter.

  4. Quarkonia Acceptance in CMS m-Chambers J/Y at CMS • CMS: J/Y mainly pT>5 GeV with barrel, due to m cutoff. • ALICE: h>2.5 with m • ATLAS (if they do HI) lower acceptance due to higher m pT cutoff. Full Detector 10% Acceptance Barrel Pt(GeV) Upsilon at CMS 20% Full Detector Barrel

  5. Quarkonia Reconstruction • Essential sub-detectors: • Tracking devices • Muon system • Pessimistic assumptions for background estimates: • dNch/dy=8000 (most generators < 5500) • <pt>p=0.48 GeV/c (HIJING 0.39 GeV/c) • <pt>k=0.67 GeV/c Special Heavy Ion Tracking Algorithm Significant Muon background from p and K decays

  6. J/Y Signal 1 month running at top Luminosity: J/Y’s detected and reconstructed in the Barrel: Min bias collisions - 1 month run - barrel only muons with P > 3.5 GeV/c 4 10 Pb-Pb L= 1027 cm2 s-1 Y/cont.= 1.0 # events/25 MeV/c2 3 10 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 5 Ca-Ca L= 2.5 1029 cm2 s-1 10 Y/cont.= 9.7 ALICE: ~2K events with ms # events/25 MeV/c2 4 10 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 Opposite-sign di-muon invariant mass (GeV/c2)

  7. Upsilon in Pb-Pb L= 1027 cm-2 s-1 Upsilon/cont.= 1.6 104 7000 Total Combinatorial background subtracted after reconstruction # Events/25 MeV/c2 6000 Decay-Decay Decay-b 3 103 5000 b-b 4000 Decay-c 3000 2 102 2000 c-c 1000 0 8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11 8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11 Di-muon Invariant Mass (GeV/c2) 1 month: 22000  and 7500 ’ detected in the barrel # Events/25 MeV/c2 Opposite-sign di-muon Invariant Mass (GeV/c2) Background contributions

  8. Upsilon in Ca-Ca L= 2.5 1029 cm-2s-1 Upsilon/cont.= 9.4 # Events/25 MeV/c2 105 Total 104 b-b Decay-Decay Decay-b 103 Decay-c 8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11 Opposite-sign di-muon invariant mass (GeV/c2) • 1 month: • 340000  • 115000 ’ • Only barrel used.

  9. Upsilon’/Upsilon ratio as a Thermometer(Ramona Vogt)

  10. Quarkonia Reference • At SPS, J/Y is compared to Drell-Yan. • At LHC Drell-Yan contribution is negligible. • Z0 proposed as reference to  production. • MZ>M • Different production mechanisms: • Z0: antiquark-quark, quark-gluon and antiquark-gluon. • : gluon-gluon. • Cross check di-muon reconstruction algorithm

  11. Jet Quenching • Large pT quarks affected by hot hadronic media • Jets at RHIC buried in low pT background • Look at particle pt spectrum

  12. Jets at LHC are Easy for High Multiplicity PbPb Jet quenching • monojet/dijet enhancement • jet-Z0mm or jet-g dNch/dy=8000 Jet Finding 100 GeV ET - e~100% - s(ET)/ET=11.6%. Total Calorimeter Energy f h

  13. Balancing Photons and Jets <E>=0 GeV <E>=4 GeV Background <E>=8 GeV • Etjet, g>120GeV in the barrel • 1 month: • 900 events for Pb-Pb • 104 events for Ca-Ca 2 weeks at L=1027 cm-2s-1 # Events/4 GeV ETg//p0-ETJet (GeV)

  14. Ultra Peripheral Collisions(Coherent Interactions) A g orP g orP A • Low pT pT < 1/R 50 MeV • Low Energy ECMMax < g/R • CERN SPS ECMMax =0.5 GeV • RHIC ECMMax =6 GeV  Detected • CERN LHC ECMMax =160 GeV

  15. STAR Ultra-Peripheral Event(DNP 2000) End view Side view ZDC ZDC AuAu gP (gAu) r pp Trigger: Low multiplicity and zero energy at Zero Degree Calorimeter (ZDC)

  16. gg Physics e+e- Cross Sections • Mainly studied at e+e- colliders.Typically p0<mgg<hc. stot up to 70 GeV by LEP. • Non perturbative QED, coupling Z2. • New Physics: • Standard Model H production marginal for HI • Any exotic particle coupling to gg. • Supersymmetric Higgs for some areas of parameters space.

  17. Ultra-Peripheral Collisionsgg Cross Sections A g g A A 100 102 Meson or lepton/quark pair 107 h p0 f 2 h a 10-2 10 2 h 105 f ' c 2 c A cc0 10-4 10-2 cc2 103 1 102 (barn) e+e- H' 10-6 10-4 107 h b events/sec events/year 102 - 1 m+ m- 10 AA hadrons 105 t+ t- h0b 10-8 10-6 s h2b 104 10-2 cc 103 (M) (barn/GeV) 10-1 events/year/GeV events/sec/GeV 106 10-4 10-10 10-8 10 H 108 10-6 10-3 SM AA bb 10-1 s 10-12 10-10 1010 10-8 10-3 10-5 1012 10-10 10-14 10-12 10-5 -1 0 2 10 10 10 10 1014 10-12 1 10 102 M (GeV) M (GeV)

  18. gg Physics, Hadron Spectroscopy • Light quark: Difficult at CMS because of low pT, challenge for triggering, unless a multiplicity trigger is used. • Heavy quark spectroscopy. Very large numbers expected

  19. Photon Nucleus (gA) • gp studied in HERA: Wgp<200 GeV • gA at LHC: Wgp<900 GeV • Vector meson production: gp(A) Vp(A), V=r,w,f,J/Y • Very large rates, for example >104 Hz f in Ca-Ca • Interface QCD and hadronic physics • LHC will be a meson factory. Competitive with other meson factories like f factory at Frascatti (CP, QM tests, etc). • Can CMS trigger on these events. Clean events with only a few tracks.

  20. Conclusions • CMS is provides unique tools to study Heavy Ion Collisions at LHC. • Some physics topics: • Quarkonium production:  and J/ families. • Jet quenching. • Ultra-Peripheral collisions.

  21. Addendum: Tracking 60 • Developed for dNch/dy=8000 and dN0/dy=4000. • Track only particles with tracks in m detector. • Use m-chambers tracks as seeds. • Use only tracking detector providing 3D space points. Detector Pitch mm MSGC 200 50 MSGC 240 Silicon 147 40 Occupancy (%) 30 20 10 0 60 70 80 90 100 110 120 Radius of MSGC layer (cm)

  22. Interference • Nuclei can emit or scatter pair • two indistinguishable possibilities • Amplitudes add • Vector meson has negative parity • s ~ |A1 - A2eip·b|2 • Destructive interference when pT << 1/b

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