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ALICE physics by the TOF/ITEP group

ALICE physics by the TOF/ITEP group. S. Kiselev, for the TOF/ITEP group Short-lived resonances Motivation for f 0 , Δ ++ and a 1 analysis Estimations of S/B for pp and AA events Jet chemical composition study Motivation TOF for jet study Fast generators of direct photons

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ALICE physics by the TOF/ITEP group

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  1. ALICE physics by the TOF/ITEP group • S. Kiselev, for the TOF/ITEP group • Short-lived resonances • Motivation for f0, Δ++ and a1 analysis • Estimations of S/B for pp and AA events • Jet chemical composition study • Motivation • TOF for jet study • Fast generators of direct photons • Promp photons • Thermal photons in Hot Hadron Gas (HHG) scenario • Thermal photons in Qurk Gluon Plasma (QGP) scenario • Summary RRC "Kurchatov Institute", Moscow S.Kiselev

  2. Short-lived resonances. Data and ALICE activity channel B.R.(%) c (fm) RHIC dataΔm (MeV)ALICE studies a1(1260) π  ~0.5 0.5 ρ0(770)π+ π-~100 1.3 p+p/d+A/Au+Au -70 p+p/Au+Au Δ++(1232)  p π+~100 1.6 p+p/d+Au -40 f0(980)  π+ π- 66 2.6 p+p/Au+Au K*(892) πK ~100 4 p+p/d+Au/Au+Au -10 p+p/Au+Au Σ*(1385)  Λπ88 5.5 p+p/d+Au/Au+A 0 Λ*(1520) p K45 12.6 p+p/d+Au/Au+Au 0p+p/Au+Au Ξ*(1530) Ξπ~100 21 p+p/d+Au/Au+Au 0 ω(782)  π+ π- π089 23 p+p/d+Au 0 ω(782) π0 9 23 p+p/d+Au/Au+Au 0 ω(782)  π+ π- 2 23 ω(782) e+e-7 10-223 p+p/d+Au/Au+Au in prog. Φ(1020) K+ K-49 44 p+p/d+Au/Au+Au 0 p+p/Au+Au Φ(1020) e+e-3 10-244 p+p/d+Au/Au+Au in prog. p+p Life Time RRC "Kurchatov Institute", Moscow S.Kiselev

  3. RHIC data: Masses and Widths P.Fachini SQM07 • No mass or width modification of η, ω, Φ, Λ*, Σ* or Ξ* • Mass shift observed for K*, Δ++ and ρ0 at low-pT  possible explanations • π+π- rescattering in p+p collisions • Medium modifications • Bose-Einstein correlations • ρ0 at high-pT No apparent mass shift! P. Fachini et.al., J.Phys.G33:431-440,2007 R. Rapp, Nucl.Phys. A725, 254 (2003), E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322 G.D. Lafferty, Z. Phys. C 60, 659 (1993); R. Rapp, Nucl.Phys. A725 (2003) 254-268 S. Pratt et al., Phys.Rev. C68 (2003) 064905 RRC "Kurchatov Institute", Moscow S.Kiselev

  4. f0 motivation A. Badalà- SQM07- Levoča – 24/06/-29/06/07 Nuclear Modification Ratios (RCP) for resonances RHIC results have shown as, in the intermediate pt region, nuclear modification factors depend on the constituent quarks rather than on particle mass. Recent suggestion by Maiani et al. (Phys. Lett. B645(2007)138) to use this observable to solve the problem of the real quark composition of some resonances as the fo(980)( or ?) RRC "Kurchatov Institute", Moscow S.Kiselev

  5. Δ++ motivation P.Fachini SQM07 Δ++  Mass and Width PDG • Δ++ mass shift observed in both minimum bias p+p and d+Au at √sNN = 200 GeV • Width agrees with PDG for both systems within errors • possible explanations: π+π- rescattering in p+p collisions, P. Fachini et.al., J.Phys.G33:431-440,2007 PDG RRC "Kurchatov Institute", Moscow S.Kiselev

  6. a1 motivation • Volker Koch, workshop on dileptons at CBM, GSI, 2007: • in the case of afull restoration of the symmetry the spectral functions oftheρmeson and its chiral partner the a1 meson becomedegenerate. • it has been proposed to measure the a1 mass spectrumin a hot and dense medium and compare it to the massspectrum of the ρmeson • If the degeneracy wouldbe observed it is expected to serve as an unambigiousexperimental signal for the detection of chiral symmetryrestoration in the hot and dense medium. RRC "Kurchatov Institute", Moscow S.Kiselev

  7. Input info and assumptions • Before to study with AliRoot it is worth to make fast estimation • Background: SHAKER events • dNch/dy = const • pt distribution: π – fit to Tevatron data, others – mt scaling: dN/dpt = [(mtπ +2)/(mt +2)]12.3 dNπ/dpt • K/π = 0.2, p/π = 0.074, /π0 = 0.17 • Signal • dNres /dy = const, pt distribution – mt scaling • Ratios weakly depend on beam energy and event centrality: (dNres/dy)/ (dNch/dy) • f0/ π- = 0.07 (STAR data)  0.0275 • Δ++/p = 0.22 (STAR data)  0.0064 • a1+/ π+ = 0.013 (A.Andronic)  0.0051 • Cut pt > 0.2 GeV/c, momentum resolution σp/p = 1% • No matter between a target and TOF  optimistic estimation of the signals RRC "Kurchatov Institute", Moscow S.Kiselev

  8. p+p: S/B(2σ) very small signal from a1, even in p+p, S/B ~ 10-3 % RRC "Kurchatov Institute", Moscow S.Kiselev

  9. Au+Au: other centralities Δ++  π+p S/B ~ (dNch/dy)-1 RRC "Kurchatov Institute", Moscow S.Kiselev

  10. short-lived resonances: summary • Short-lived resonances: mass shift in p+p for some of resonances • estimations of signals from resonances f0, Δ++ and a1 with TOF/ALICE have been made: - p+p: S/B ~ 10% (~0.004% for a1) - Au+Au: S/B is smaller as S/B ~ (dNch/dy)-1,  low signals from f0 and Δ++ - like-sign or event-mixing techniques should be used - to have S/√(S+B)~10, 105 events are needed - S/B increases as a function of pt • Netx step: p+p simulations in the AliRoot package RRC "Kurchatov Institute", Moscow S.Kiselev

  11. gluon radiation Jets: motivation Use jets and high-pT particles to probe the medium • Initial production at high-pT is calculable in perturbative QCD and can be calibrated by reference measurements • These partons will first travel through a dense color medium. They are expected to lose energy through collision energy loss and medium induced gluon radiation,“jet quenching”. • The magnitude of the energy loss depends on the gluon density of the medium and on the path length • However, we still need to calibrate our probe: • Fragmentation, hadronisation in the vacuum • … and in the medium • Calibrate/constrain energy loss mechanism • Check initial production rates • Goal: measure medium properties • Density, temperature, number of degrees of freedom • Dynamical properties e.g. viscosity RRC "Kurchatov Institute", Moscow S.Kiselev

  12. Jets: TOF PID performance • At first glance it is impossible to study high Pt with TOF RRC "Kurchatov Institute", Moscow S.Kiselev

  13. Single inclusive hadron distribution vs ξ M.Estienne. - PWG4 15. 01.2008 Medium effects introduced at parton splitting Hump-backed plateau N. Borghini & U. Wiedemann Hep-ph/0506218 z = phadron/Ejet • Quenching effect: decreases of the particles at high z (low x) & increases of the particles at low z (high x) =ln(EJet/phadron) • Fragmentation strongly modified at phadron~1-5 GeV/c even for the highest energy jets • ALICE should be well dedicated to test this x range (tracking down to 100 MeV/c) • EMCal => improves Ejet determination RRC "Kurchatov Institute", Moscow S.Kiselev

  14. Jets: TOF can help to study jet modification • We can use high Pt (even not identified) charged particle or photon as a trigger and study accompanying particles! • Fragmentation strongly modified at phadron~1-5 GeV/c even for the highest energy jets. • We even don’t need jet reconstructions: instead of z we can use z’ = phadron/Eleading particle (need theoretical predictions!) • Fragmentation distributions should also depend on particle type. (need theoretical predictions!) =>we need PID in this range to study jet chemical composition. (From RHIC data the p/π~1 at high Pt => we can even enlarge TOF PID range) RRC "Kurchatov Institute", Moscow S.Kiselev

  15. Jets: Azimuthal correlations RRC "Kurchatov Institute", Moscow S.Kiselev

  16. Jets: Azimuthal correlations • Lot of theoretical explanations of double away-side peak: deflected jet, large gluon radiation, shock waves (Mach cones), Cerenkov radiation • Long-range Δη correlation on the near-side (ridge): coupling of induced radiation to the longitudinal flow, turbulent color fields, anisotropic plasma, interplay of jet-quenching and strong radial flow… • Chemical composition of away side jet is different compare with trigger jet (fragmentation in vacuum) RRC "Kurchatov Institute", Moscow S.Kiselev

  17. Jets: summary • ALICE TOF can be used for the jet composition study. • Next steps: • Simulations on a generator (PYQUEN, HYDJET++, …) level: • double peak, barion/meson ratio,… • relative to leading particle energy distribution z’ = phadron/Eleading particle or ’=ln(Eleadingparticle/phadron) • analysis for different types of particles (π, K, p, φ…) • Simulations in the AliRoot package RRC "Kurchatov Institute", Moscow S.Kiselev

  18. Prompt photons: pp data fit + binary scaling • PHENIX hep-ph/0609037 (√s)5 Ed3σ/d3p = F(xT,y) • One can use a data tabulation of the F(xT,y) to generate prompt photons. • A+B: Ed3N/d3p(b)= Ed3σpp/d3p AB TAB(b)= Ed3σpp/d3p Ncoll(b)/σppin • Nuclear effects (Cronin, quenching, …) are not taken into account. • Realization: GePP.C macros for ROOT RRC "Kurchatov Institute", Moscow S.Kiselev

  19. GePP: results Comparison with RHIC data Prediction for LHC RRC "Kurchatov Institute", Moscow S.Kiselev

  20. Bjorken -(1+1)-HydroDynamics (BHD) Phys.Rev.D27(1983)140 Proper time  and rapidity y There is no dependence on Lorenz boost variable y: Landau hydrodynamical model, viscosity and conductivity are neglected RRC "Kurchatov Institute", Moscow S.Kiselev

  21. Phys.Rep.364(2002)98 Photon spectrum in BHD Photon spectra follow from convoluting thephoton productionrates with the space–time evolution For a longitudinallyexpanding cylinder For proper time  and rapidity y` Input function – production rate E dN/d4xd3p (E,T) Connection with the local rest frame For anidealgas Main parameters: initial 0 , T0and Tf (at freeze-out) 0 ↔ yield, T0 ↔ spectrum slope Tf ↔ weak sensitivity, Tf = 100 MeV RRC "Kurchatov Institute", Moscow S.Kiselev

  22. Rates: HHG scenario • C.Song, Phys.Rev.C47(1993)2861 an effective chiral Lagrangian with π, ρanda1 mesons to calculate theprocesses ππ →ργ , πρ → πγ, and ρ →ππγ . • C.Song and G.Fai, Phys.Rev.C58(1998)1689. parameterizations for photon rates. Realization:GeTP_HHG.C macros for ROOT RRC "Kurchatov Institute", Moscow S.Kiselev

  23. GeTP_HHG: SPS and RHIC data SPS RHIC one can fit SPS data at high pt one can fit RHIC data but with not reasonable parameters RRC "Kurchatov Institute", Moscow S.Kiselev

  24. Rates from QGP -1st order Phys.Lett.B510(2001)98 Perturbative thermal QCD applying Hard Thermal Loop (HTL) resummation RRC "Kurchatov Institute", Moscow S.Kiselev

  25. Rates from QGP -2nd order 2-loop contribution is the same order in αs 3-loop …. Thermal photon production in the QGP is a non-perturbative mechanism that can not be accessed in perturbative HTL resummed thermal field theory One must consider the QGP rates as an educated guess. PL B510(2001)98 RRC "Kurchatov Institute", Moscow S.Kiselev

  26. Rates from QGP Annihilation with scattering (aws) dominates at high E The Landau-Pomeranchuk-Migdal (LPM) effect (not taken into account in out study) reduces the 2-loop rates by ~30% in E/T > 1 Realization:GeTP_QGP.C macros for ROOT RRC "Kurchatov Institute", Moscow S.Kiselev

  27. GeTP_QGP: SPS and RHIC data SPS RHIC RRC "Kurchatov Institute", Moscow S.Kiselev

  28. GeTP_QGP: prediction for LHC 2+1 hydro, F.Arleo, D. d’Enterria, D. Peressounko, nucl-th/0707.2357 The same τ0 , T0: steeper HHG spectrum in 1+1 due to radial flow in 2+1 RRC "Kurchatov Institute", Moscow S.Kiselev

  29. Direct photon generators: summary • 3 fast generators of direct photons have been proposed: • - GePP.C – prompt photons (pp data fit + binary scaling) • - GeTP_HHG.C – thermal photons in the HHG scenario • - GeTP_QGP.C – thermal photons in the QGP scenario • in Bjorken (1+1) hydrodynamics + other assumptions: • ideal massless gas, µq =0, 1st order phase transition • One can fit SPS and RHIC data • Predictions for LHC • Next steps: implement the generators into AliRoot package, take in account the LMP effect, … RRC "Kurchatov Institute", Moscow S.Kiselev

  30. Summary The TOF/ITEP group activity RRC "Kurchatov Institute", Moscow S.Kiselev

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