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Overview of CMS heavy -ion results

Overview of CMS heavy -ion results. Raphaël Granier de Cassagnac for the CMS collaboration LLR – École polytechnique / IN2P3 ERC grant “ QuarkGluonPlasmaCMS ” LHC days , October 2 nd 2012, Split. A wealth of results. Affordable in a 20’ talk?.

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Overview of CMS heavy -ion results

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  1. Overview of CMS heavy-ion results Raphaël Granier de Cassagnac for the CMS collaboration LLR – École polytechnique / IN2P3 ERC grant “QuarkGluonPlasmaCMS” LHC days, October 2nd2012, Split

  2. A wealth of results Affordable in a 20’ talk? raphael@in2p3.fr - Heavy ions in CMS - Split • Multiplicity and transverse energy • dNch/dη ≈ 1600 and dET/dη ≈ 2 TeV ! • Particle correlations • Elliptic flow (incl. π0) and higher harmonics • Di-hadron correlations (the “ridge”) • Candles: Electro+weak bosons • Z and W bosons • Isolated photons • Jet quenching • Photon+Jet • Fully reconstructed jets • Jet fragmentation & shape • Quarkoniumsuppression • Five states disappearing

  3. A wealth of results All results available at https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsHIN Or google search “CMS heavy ions” 18 submitted PbPb papers (as many as ALICE) + 10 documented preliminary analysis (PAS) Affordable in a 20’ talk? raphael@in2p3.fr - Heavy ions in CMS - Split • Multiplicity and transverse energy • dNch/dη ≈ 1600 and dET/dη ≈ 2 TeV ! • Particle correlations • Elliptic flow and higher harmonics • Di-hadron correlations (the “ridge”) • Candles: Electro+weak bosons • Z and W bosons • Isolated photons • Jet quenching • Photon+Jet • Fully reconstructed jets • Jet fragmentation & shape • Quarkoniumsuppression • Five states disappearing

  4. Particule detection |η|<2.4 Muons 1-2% resolution up to 100 GeV/c Photons 10% resolution in central events at 20 GeV EMCal PbWO4 |η|<3 Muon: drift tubes + RPC |η|<2.4 Silicium: pixels (3) and strips (10) |η|<2.4 HCal: Scintillators |η|<5 + high rapidity extension raphael@in2p3.fr - Heavy ions in CMS - Split

  5. Pb-Pbcollision raphael@in2p3.fr - Heavy ions in CMS - Split

  6. From the key concept: centrality… raphael@in2p3.fr - Heavy ions in CMS - Split • Collision centrality related to energy deposit in (forward) calorimeters • Then to geometrical quantities: • Ncoll = number of elementary NN collisions • or TAA = Ncoll / σpp • Hard probes are supposed to scale with Ncoll, in the absence of medium effect, RAA = 1

  7. … to the nuclear modification factor RAA dNAA dNAA RAA= = dNPP x Ncoll dσPP x TAA raphael@in2p3.fr - Heavy ions in CMS - Split • Collision centrality related to energy deposit in (forward) calorimeters • Then to geometrical quantities: • Ncoll = number of elementary NN collisions • or TAA = Ncoll / σpp • Hard probes are supposed to scale with Ncoll, in the absence of medium effect, RAA = 1

  8. PbPb collisions @ √sNN = 2.76 TeV Dec. 2011: ≈ 150 μb–1PbPb x 20 Dec. 2010: ≈ 7 μb–1PbPb • Binary-scaled • equivalent •  as many • Z, W, photons… + Mar. 2011 ≈ 230 nb–1pp@2.76 TeV raphael@in2p3.fr - Heavy ions in CMS - Split

  9. Electro+Weak bosons should go through the colored medium without feeling it New candles raphael@in2p3.fr - Heavy ions in CMS - Split

  10. Z boson centrality independence (150 μb–1) dNAA RAA = dσPP x TAA • Very low pp statistics available at 2.76 TeV ≈ 20 times less Z than PbPb raphael@in2p3.fr - Heavy ions in CMS - Split

  11. Z boson centrality independence (150 μb–1) • (PRL 106 (2011) 212301) • CMS-PAS-HIN-12-008 • Very low pp statistics available at 2.76 TeV ≈ 20 times less Z than PbPb dNAA / TAA = dσppx RAA raphael@in2p3.fr - Heavy ions in CMS - Split

  12. Z boson centrality independence (150 μb–1) • (PRL 106 (2011) 212301) • CMS-PAS-HIN-12-008 • Very low pp statistics available at 2.76 TeV ≈ 20 times less Z than PbPb • Compare to POWHEG (NLO generator) instead • Well tested at Tevatron (2 TeV) and LHC (7 TeV) • 5% uncertainty from NNLO, pdfs, etc. dNAA / TAA = dσppx RAA raphael@in2p3.fr - Heavy ions in CMS - Split

  13. Z boson centrality independence (150 μb–1) • (PRL 106 (2011) 212301) • CMS-PAS-HIN-12-008 • Very low pp statistics available at 2.76 TeV ≈ 20 times less Z than PbPb • Compare to POWHEG (NLO generator) instead • Well tested at Tevatron (2 TeV) and LHC (7 TeV) • 5% uncertainty from NNLO, pdfs, etc. dNAA / TAA = dσppx RAA RAA = 0.95 ± 0.03 ± 0.13 raphael@in2p3.fr - Heavy ions in CMS - Split

  14. W boson centrality independence (7.2 μb–1) dNAA / TAA = dσppx RAA W W+ W– • PLB 715 (2012) 66 raphael@in2p3.fr - Heavy ions in CMS - Split

  15. W boson centrality independence (7.2 μb–1) dNAA / TAA = dσppx RAA • PLB 715 (2012) 66 raphael@in2p3.fr - Heavy ions in CMS - Split

  16. W boson centrality independence (7.2 μb–1) 2010 PbPb ≈ pp data RAA(W) = 1.04 ± 0.07 ± 0.12 RAA(W+) = 0.82 ± 0.07 ± 0.09 RAA(W–) = 1.46 ± 0.14 ± 0.16 Consistent with pure isospin dNAA / TAA = dσppx RAA More d quarks in Pb make more W+ than in pp • PLB 715 (2012) 66 raphael@in2p3.fr - Heavy ions in CMS - Split

  17. Photon centrality independence (7.2 μb–1) ( isolated photons, after large background subtraction ) • PLB 710 (2012) 256 raphael@in2p3.fr - Heavy ions in CMS - Split

  18. Unmodified electro+weak bosons • Within uncertainties, electro+weak bosons are not modified • Confirm the validity of Ncoll scaling • More precision may reveal nuclear PDF modifications • But let’s first use these calibrated probes… raphael@in2p3.fr - Heavy ions in CMS - Split

  19. Jet quenching

  20. Photon+jet(150 μb–1) Area normalized to unity Pythia+Hydjet Photon-jet momentum balance arXiv:1205.0206 raphael@in2p3.fr - Heavy ions in CMS - Split

  21. Photon+jet(150 μb–1) Area normalized to unity 0-10% PbPb Pythia+Hydjet Photon-jet momentum balance arXiv:1205.0206 raphael@in2p3.fr - Heavy ions in CMS - Split

  22. Photon+jet(150 μb–1) Pythia+Hydjet Area normalized to unity 0-10% Jet-photon pT balance 14% drop pp PbPb PbPb Pythia+Hydjet Pythia+Hydjet 20% lose jet partner Photon-jet momentum balance pp PbPb arXiv:1205.0206 raphael@in2p3.fr - Heavy ions in CMS - Split

  23. Modified jet RAA(150 μb–1) CMS-PAS-HIN-12-004 raphael@in2p3.fr - Heavy ions in CMS - Split

  24. Jet RAA Cone size R = 0.3, but does not vary a lot for R = 0.2 or 0.4 CMS-PAS-HIN-12-004 raphael@in2p3.fr - Heavy ions in CMS - Split

  25. Wheredoes the energy go? 100 GeV inclusive jet Anti-kT R=0.3 jet in PYTHIA 95% of jet energy in r < 0.2 95% of jet energy in pT > 4 GeV particles PRC 84 (2011) 024906 G. Roland at QM’12 raphael@in2p3.fr - Heavy ions in CMS - Split • To large angle & low pT • Qualitative idea in the first 2010 (di)jet paper • Quantitatively • Low pT, fragmentation functions • Large angle, jet shape

  26. Jet fragmentation arXiv:1205.5872 accepted by JHEP vsCMS-PAS-HIN-12-013 ξ = ln(1/z) & z=pT(track)/pT(jet) where pT(jet) is quenched already ( < pT(parton) ) ξ raphael@in2p3.fr - Heavy ions in CMS - Split At first sight (QM’11, run 1, pT(track) > 4 GeV & pT(jet) > 100 GeV), surviving jets are not modified Looking closer (QM’12, run 2, pT(track) > 1 GeV & more energetic jets), modifications appear

  27. Jet fragmentation and shapes PbPb/pp distributions No change at small r, high pT Narrowing/depletion at intermediate pT Broadening/excess at large r, low pT CMS-PAS-HIN-12-013 raphael@in2p3.fr - Heavy ions in CMS - Split

  28. Back to RAA of jets(and b-jet) Note: first b-jet identification in heavy-ion collisions CMS-PAS-HIN-12-003 raphael@in2p3.fr - Heavy ions in CMS - Split

  29. Back to RAA of jets, and hadrons Jets: CMS-PAS-HIN-12-004 Hadrons: EPJC 72 (2012) 1945 G. Roland at QM’12 Looking at the same partonpT range PbPb fragmentation function = pp for ξ <1 Charged particles with pT= 50-100 GeV/c z = pT(track)/pT(jet) = 0.4-0.6 x < 1 raphael@in2p3.fr - Heavy ions in CMS - Split

  30. Quarkonia

  31. Quarkonium suppression Matsui & Satz, PLB168 (1986) 415 • Old predicted signature of the QGP • Quarkonia should melt one after the other, depending on their binding energy • Recent example of melting temperatures  • @ SPS / RHIC, no / marginal access to the (yet unresolved) Upsilon family • @ SPS, J/ψ and ψ’ studied in detail • @ RHIC, J/ψ brought up surprises… • Though they are suppressed, the balance of various effects is not clear… ϒ(1S) χb J/ψ, ϒ(2S) χc, χ’b, ψ', ϒ(3S) Mocsy, EPJC61 (2009) 705 BNL workshop in June raphael@in2p3.fr - Heavy ions in CMS - Split

  32. Prompt J/ψ suppression centrality • CMS J/ψpT > 6.5 GeV/c • Material and B-field • Feed down from B  J/ψ is subtracted • More suppression than at RHIC • CMS < STAR (pT > 5 GeV/c) • More suppression than at low pT • CMS<ALICE (all pT) • Popular explanation: regeneration from uncorrelated and • Stronger at low pT > 100 pairs in a central event JHEP05 (2012) 176 & CMS-HIN-PAS-12-014 raphael@in2p3.fr - Heavy ions in CMS - Split

  33. Prompt J/ψ suppression centrality • CMS J/ψpT > 6.5 GeV/c • Material and B-field • Feed down from B  J/ψ is subtracted • More suppression than at RHIC (at high pT) • CMS < STAR (pT > 5 GeV/c) • Less suppression at low pT • CMS<ALICE (inclusive, all pT) • Popular explanation: regeneration from uncorrelated and • Stronger at low pT > 100 pairs in a central event JHEP05 (2012) 176 & CMS-HIN-PAS-12-014 raphael@in2p3.fr - Heavy ions in CMS - Split

  34. First look at ψ(2S) CMS-PAS-HIN-12-007 raphael@in2p3.fr - Heavy ions in CMS - Split • Relatively less ψ(2S) than J/ψ, as expected @ midrapidity|y|< 1.6, thus high pT > 6.5 GeV • (a hint of an opposite behaviour at lower pT, but less than 2σ)

  35. Upsilon (1S), (2S) and (3S) (PRL107 (2011) 052302) arXiv:1208.2826 raphael@in2p3.fr - Heavy ions in CMS - Split

  36. Upsilons (1S), (2S) and (3S) Upsilon(1S) and (2S) at LHC Sequential disappearance of the 3 states For minimum bias RAA (Y(1S)) = 0.56 ± 0.08 ± 0.07 RAA (Y(2S)) = 0.12 ± 0.04 ± 0.02 RAA (Y(3S)) < 0.10 @ 95% CL (Remember a large part of Y(2S) comes from higher state decays, in particular the χb) (PRL107 (2011) 052302) arXiv:1208.2826 raphael@in2p3.fr - Heavy ions in CMS - Split

  37. Five states to bind them all Forgetting low pT J/ψ (regeneration) for a while… RAA(MB) vs binding energy looks ordered… TBD with more data vs centrality and unfolding cold effects (pA) & feeddown could start acting as a thermometer? Mironov at QM’12 raphael@in2p3.fr - Heavy ions in CMS - Split

  38. To conclude 1/ Being interpreted in terms of Quark-Gluon Plasma properties… 2/ Once we have checked what happens in pPb (2013…) raphael@in2p3.fr - Heavy ions in CMS - Split Three unmodified control probes (photon, Z and W) Detailed studies of jet quenching Five quarkoniumsuppressions And more!

  39. Back up

  40. W boson production @ LO : & Less W+ and more W– in PbPb than in pp (isospin effect) • Cancels for W+ + W– • W boosted towards the valence quark (higher rapidity) • Spin conservation μ+ (μ–) boosted back to (awayfrom) midrapidity • Different muon rapidity distributions (not heavy-ion specific) between W+ and W– ud p p W+ μ+ ν raphael@in2p3.fr - Heavy ions in CMS - Split

  41. Muon charge asymmetry N+ – N– N+ + N– |ημ| • PLB 715 (2012) 66 raphael@in2p3.fr - Heavy ions in CMS - Split Less up quarks make less W+ in PbPb than in pp Isospin effect bringing down asymmetry by 0.2 to 0.4 (EPS09 modifications are 0.03 at most)

  42. How to find photons? Δϕ • Trigger on ECAL clusters • Uncorrected ET > 15 GeV, fully efficient for ET > 20 GeV • Subtract underlying event • From same pseudorapidity strip, event by event • Look for isolated cluster • Remove photons from bremsstrahlung and jet fragmentation… • Look at shower shape in the highly segmented ECAL • Further remove isolated π0, η Δη photon-like π,η 2γ raphael@in2p3.fr - Heavy ions in CMS - Split

  43. Photon spectrum (2010) • PLB 710 (2012) 256 Consistent with JETPHOX With unmodified pdf (CT10) raphael@in2p3.fr - Heavy ions in CMS - Split

  44. Unmodified photons • PLB 710 (2012) 256 • Normalised by pp! • Consistent with unity! • Uncertainties still • larger than modified • pdf uncertainties… raphael@in2p3.fr - Heavy ions in CMS - Split

  45. Jet reconstruction performances Resolution Responce raphael@in2p3.fr - Heavy ions in CMS - Split

  46. raphael@in2p3.fr - Heavy ions in CMS - Split

  47. raphael@in2p3.fr - Heavy ions in CMS - Split

  48. raphael@in2p3.fr - Heavy ions in CMS - Split

  49. Modified hadrons (150 μb–1) EPJC 72 (2012) 1945 raphael@in2p3.fr - Heavy ions in CMS - Split

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