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 production in p+p and Au+Au collisions at 200 GeV in STAR

 production in p+p and Au+Au collisions at 200 GeV in STAR. Rosi Reed UC Davis. Some Relevant Terms. Standard Model – Theory that combines 3 out of the 4 fundamental forces Quantum Chromo-dynamics (QCD) – The strong force which holds the nucleus together

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 production in p+p and Au+Au collisions at 200 GeV in STAR

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  1.  production in p+p and Au+Au collisions at 200 GeV in STAR Rosi Reed UC Davis

  2. Some Relevant Terms • Standard Model – Theory that combines 3 out of the 4 fundamental forces • Quantum Chromo-dynamics (QCD) – The strong force which holds the nucleus together • Quark Gluon Plasma (QGP) – A hot, dense form of matter with free quarks • Heavy Ion – Gold ions for STAR • eV – Electron Volt = 1.6 x 10-19 Joules Rosi Reed - SJSU 9/16/2010

  3. Goals for this talk • Introduce Relativistic Heavy Ion physics • Explain the physics behind the Quark Gluon Plasma (QGP) • Show how the  meson can be used to probe the (QGP) • Measure the temperature Rosi Reed - SJSU 9/16/2010

  4. Standard Model Describes interactions due to 3 out of 4 of the fundamental forces Predicted the existence of the W, Z, gluons, top and charm before these particles were observed Fermions Higgs is the only particle predicted that has not been found Does not include gravity, dark matter, or dark energy Bosons Rosi Reed - SJSU 9/16/2010 http://bccp.lbl.gov/Academy/workshop08/08%20PDFs/chart_2006_4.jpg

  5. Electro-Magnetic Force • Quantum Electro-dynamics (QED) • 2 charges, + and – • Perturbation theory • Calculations done via Feynman diagrams • Allows QED calculations to be truncated with very few diagrams e- e- ? + e+ e+ 1st Order Contributions 2nd Order Contributions Each multiplies result by 1/137 = 1/4pe0ħc Rosi Reed - SJSU 9/16/2010

  6. Strong Force • Quantum-Chromodynamics (QCD) • 3 charges called “colors” • All known stable particles are colorless • Mesons have a quark and an anti-quark (ex. p) • Baryons have 3 quarks, 1 of each color (ex. protons) • Only quarks and gluons can feel the QCD force • Each multiplies result by ~1 • QCD is not perturbative at low energies • Mediated by gluons • Color+anti-color but not colorless! • Spin 1 • Mass 0 • Can interact with each other! g Feynman diagram Rosi Reed - SJSU 9/16/2010

  7. Confinement in QCD: a cartoon http://nobelprize.org/nobel_prizes/physics/laureates/2004/illpres/index.html • At high energy and small distances, the strength of this force decreases! • “Asymptotic freedom” • Nobel Prize 2004 Rosi Reed - SJSU 9/16/2010

  8. Heavy Ion Collisions At STAR we use Gold Ions Gold is nearly spherical 197 protons and neutrons Allows us to study the energy range E > Edeconfinement E < EAsymptotic freedom Ions look like “pancakes” due to relativistic length contraction! Rosi Reed - SJSU 9/16/2010

  9. Generating a deconfined state • Melting protons and neutrons: Hot quarks and gluons in (QCD) • heating • compression •  deconfined color matter ! Hadronic Matter (confined) Nuclear Matter (confined) Quark Gluon Plasma deconfined ! Rosi Reed - SJSU 9/16/2010

  10. QCD Phase diagram Rosi Reed - SJSU 9/16/2010

  11. Heavy ion collisions = HOT matter • Room Temperature: 300 K = 0.025 eV • Fire: 1000-2000 K: ~0.12 eV • Sun : • Surface: 5000 K: ~0.4 eV • Corona: 5 x 106 K ~ 400 eV • Core: 15 x 106 K ~ 1 keV • Heavy ion collision : • Tc ~ 173 MeV : 2 x 1012 K • Temperature of deconfinement • Initial T of QGP at STAR = ? > Tc Rosi Reed - SJSU 9/16/2010

  12. Relativistic Heavy Ion Collider (RHIC) PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS 2 km v = 0.99995c = 186,000 miles/sec Rosi Reed - SJSU 9/16/2010

  13. RHIC: Some key results • Goal: Produce matter in the hot phase of QCD. • What are its properties? • Is the system made up of quarks and gluons? • Results and interpretation. • Temperature is high. • All estimates > Tc • Observation of collective fluid-like behavior of quarks • High momentum particles are suppressed • Matter produced is nearly opaque to quarks and gluons • Sci Am May 2006. by W. Zajc. • STAR White Paper: Nuc Phys A 757 (2005) 102 Rosi Reed - SJSU 9/16/2010

  14.  : a probe of the QGP • How hot is the matter formed at RHIC? • Is there a way to quantitatively measure the temperature of the produced matter? • Yes!  (Upsilon) production • bb quark Mesons • Measure production in Heavy Ion collisions compared to proton-proton collisions Rosi Reed - SJSU 9/16/2010

  15. Heavy quark bound states • Non-relativistic Quantum Mechanics • Schrödinger equation • Two particles bound by a linearly rising potential V(r) ~ kr. • Bound state of charm-anticharm • Charmonium • J/y, y’ (ground state 1s, and excited state 2s state) • Excited states have different <r> • Bottom-antibottom • Bottomonium • (1S, 2S, 3S) Rosi Reed - SJSU 9/16/2010

  16. Suppression of (1S+2S+3S) • Quarkonia = heavy quark+anti-quark meson • b+c quarks are produced early in the collision • Makes them an excellent probe • Quantifying suppression requires: • Baseline p+p measurement • Sequential Suppression of the (1S+2S+3S) gives a model dependent temperature • Each state has a different “melting” temperature Rosi Reed - SJSU 9/16/2010

  17. Melting of Quarkonia Rosi Reed - SJSU 9/16/2010

  18. Measuring Temperature Sequential disappearance of states: QCD thermometer  QGP Properties Theoretical Expectations in 200 GeV Au+Au Collisions: (1S)does notmelt (2S)+J/yare likelyto melt (3S)+y(2S)willmelt A. Mocsy and P. Petreczky PRD 77 014501 (2008) A .Mocsy, 417th WE-Heraeus-Seminar,2008 A. Mocsy and P.Petreczky, PRL 99, 211602 (2007) Rosi Reed - SJSU 9/16/2010

  19. STAR Detectors Tracker (TPC) Tracking  momentum ionization energy loss  electron ID Calorimeter (BEMC) Measures Energy E/p  electron ID beam magnet Rosi Reed - SJSU 9/16/2010

  20. Measuring  at STAR Decay channel:  e+e− BR = Branching Ratio = How often  decays in that manner G = mass width due to finite lifetime • (1S) • m = 9.46 GeV • G = 54 keV • BR(e+e-) = 2.5% • (2S) • m = 10.02 GeV • G = 32 keV • BR(e+e-) = 2.0% • (3S) • m = 10.35 GeV • G = 20 keV • BR(e+e-) = 2.2% • Why look at di-elelectron channel? • Di-lepton channel is clean • STAR can only measure electrons out of e,m,t Mproton = 0.938 GeV Melectron = 0.511 MeV Rosi Reed - SJSU 9/16/2010 PDG  Values

  21. Measuring  at STAR • Using Einstein’s famous equation (c 1) • unlike-sign electron pairs  Signal + Background • like-sign electron pairs  Background M is the invariant mass Widths are larger than PDG values due to detector resolution Rosi Reed - SJSU 9/16/2010

  22. A STAR  Event Rosi Reed - SJSU 9/16/2010

  23. A STAR  Event Rosi Reed - SJSU 9/16/2010

  24. STAR  Trigger pp Data pp Rejection ~105 in p+p Can sample full luminosity E1 Cluster One in 109 p+p collisions will have a! Data AuAu q E2 Cluster Data Rosi Reed - SJSU 9/16/2010

  25. Electron ID Electrons from  will be here p K Contamination p e E/p and ionization energy loss (dE/dx) of tracks are used to select e+ and e- tracks Combination allows greater purity Phys. Rev. D 82 (2010) 12004 Rosi Reed - SJSU 9/16/2010

  26. Analysis Techniques Track pairs combined into: e+e- = N+- = Signal + Background Unlike-Sign e-e-,e+e+ = N--,N++ = Background Like-Sign Signal calculated as: S = N+--2√N --N++ Phys. Rev. D 82 (2010) 12004 Rosi Reed - SJSU 9/16/2010

  27.  in p+p 200 GeV Phys. Rev. D 82 (2010) 12004 Phys. Rev. D 82 (2010) 12004 3σ Signal Significance N(total)= 67±22(stat.) 1 b = 10-28 m2 Barn  probability of an interaction between particles At 200 GeV the total inelastic p+p cross-section is 42 mb Rosi Reed - SJSU 9/16/2010

  28. STAR  vs. theory + world data STAR 2006 √s=200 GeV p+p ++→e+e- cross sectionconsistentwithpQCDandworld data trend Phys. Rev. D 82 (2010) 12004 Rosi Reed - SJSU 9/16/2010

  29. Measuring  in Au+Au How many p+p collisions = 1 Au+Au collision? 0-60% Centrality Bright Colors = collision RefMult# charged particles # collisions RefMult is the observable # collisions per centrality based on model Rosi Reed - SJSU 9/16/2010

  30.  in Au+Au 200 GeV First Heavy Ion  Measurement! 4 Million Events 4.6s significance 95 Signal counts Rosi Reed - SJSU 9/16/2010

  31. (1S+2S+3S) Ratio 0-60% Centrality • Yield of (1S+2S+3S) • 78±15(stat:)+17/-22(sys.) • Evidence that  can be measured in heavy ion collisions • Ratio of Observed/Expected • 0.920±0.35(stat.)+0.06/-0.18 • Indicates little suppression at RHIC energies Rosi Reed - SJSU 9/16/2010

  32. Temperature! Ratio of (1S+2S+3S) = 0.92Some suppression of (3S) T =0.8 Tc 0.53 (lower bound)  Suppression of (2S+3S)  T = 1.2 Tc 1.28 (upper bound)  T << Tc not physical S. Digal, P. Petreczky, and H. Satz, Phys. Rev. D64, 094015 (2001) 140 < T < 210 MeV Rosi Reed - SJSU 9/16/2010

  33. Conclusions Phys. Rev. D 82 (2010) 12004 • (1S+2S+3S) peak measured in p+p collisions • (1S+2S+3S) peak observed in Au+Au collisions • Proof that  can be measured in Heavy Ion collisions! • Temperature is 140 < T < 210 MeV • Indicates we will be able to set an upper limit with more statistics! • Future Measurements • 3x more p+p data from 2009 • 4x more Au+Au data from 2010 • Improve Temperature Precision Rosi Reed - SJSU 9/16/2010

  34. Back-Up

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