RRC "Kurchatov Institute", Moscow S.Kiselev1 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 Promp photons Thermal photons in Hot Hadron Gas (HHG) scenario Thermal photons in Qurk Gluon Plasma (QGP) scenario  Summary

RRC "Kurchatov Institute", Moscow S.Kiselev2 Short-lived resonances. Data and ALICE activity a 1 (1260)  π  ~ ρ 0 (770)  π + π - ~ p+p/d+A/Au+Au -70 p+p/Au+Au Δ ++ (1232)  p π + ~ p+p/d+Au -40 f 0 (980)  π + π p+p/Au+Au K * (892)  π K ~100 4 p+p/d+Au/Au+Au -10 p+p/Au+Au Σ*(1385)  Λ π p+p/d+Au/Au+A 0 Λ*(1520)  p K p+p/d+Au/Au+Au 0 p+p/Au+Au Ξ*(1530)  Ξ π ~ p+p/d+Au/Au+Au 0 ω(782)  π + π - π p+p/d+Au 0 ω(782)  π 0  9 23 p+p/d+Au/Au+Au 0 ω(782)  π + π ω(782)  e + e p+p/d+Au/Au+Au in prog. Φ(1020)  K + K p+p/d+Au/Au+Au 0 p+p/Au+Au Φ(1020)  e + e p+p/d+Au/Au+Au in prog. p+p channel B.R.(%) c  (fm) RHIC data Δm (MeV) ALICE studies Life Time

RRC "Kurchatov Institute", Moscow S.Kiselev3 RHIC data: Masses and Widths No mass or width modification of η, ω, Φ, Λ*, Σ* or Ξ* Mass shift observed for K*, Δ ++ and ρ 0 at low-p T  possible explanations –π + π - rescattering in p+p collisions –Medium modifications –Bose-Einstein correlations ρ 0 at high-p T  No apparent mass shift! R. Rapp, Nucl.Phys. A725, 254 (2003), E.V. Shuryak and G.E. Brown, Nucl. Phys. A 717 (2003) 322 P. Fachini et.al., J.Phys.G33: ,2007 G.D. Lafferty, Z. Phys. C 60, 659 (1993); R. Rapp, Nucl.Phys. A725 (2003) S. Pratt et al., Phys.Rev. C68 (2003) P.Fachini SQM07

RRC "Kurchatov Institute", Moscow S.Kiselev4 Nuclear Modification Ratios (R CP ) for resonances RHIC results have shown as, in the intermediate p t 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 f o (980)( or ?) A. Badalà- SQM07- Levoča – 24/06/-29/06/07 f 0 motivation

RRC "Kurchatov Institute", Moscow S.Kiselev 5 Δ ++  Mass and Width Δ ++ mass shift observed in both minimum bias p+p and d+Au at √s NN = 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: ,2007 PDG Δ ++ motivation P.Fachini SQM07

RRC "Kurchatov Institute", Moscow S.Kiselev6 a 1 motivation  Volker Koch, workshop on dileptons at CBM, GSI, 2007:  in the case of a full restoration of the symmetry the spectral functions of the ρ meson and its chiral partner the a 1 meson become degenerate.  it has been proposed to measure the a 1 mass spectrum in a hot and dense medium and compare it to the mass spectrum of the ρ meson  If the degeneracy would be observed it is expected to serve as an unambigious experimental signal for the detection of chiral symmetry restoration in the hot and dense medium.

RRC "Kurchatov Institute", Moscow S.Kiselev7 Input info and assumptions  Before to study with AliRoot it is worth to make fast estimation  Background: SHAKER events dN ch /dy = const p t distribution: π – fit to Tevatron data, others – m t scaling: dN/dp t = [(m t π +2)/(m t +2)] 12.3 dN π /dp t K  /π  = 0.2, p  /π  = 0.074,  /π 0 = 0.17  Signal dN res /dy = const, p t distribution – m t scaling Ratios weakly depend on beam energy and event centrality: (dN res /dy)/ (dN ch /dy)  f 0 / π - = 0.07 (STAR data)   Δ ++ /p = 0.22 (STAR data)   a 1 + / π + = (A.Andronic)   Cut p t > 0.2 GeV/c, momentum resolution σ p /p = 1%  No matter between a target and TOF  optimistic estimation of the signals

RRC "Kurchatov Institute", Moscow S.Kiselev8 p+p: S/B(  2σ) res ona nce m MeV  MeV chan nel BR (%) dN res /dy dN ch /dy accep (%) at p t =0.5 S/B (%)S √S+B f0f K+K-K+K ~288860/19327 = f0f π+π -π+π ~ / = Δ π+pπ+p ~ / = a1+a π+γπ+γ ~21001/ = a1+a π+γπ+γ ~21003/60616 = a1+a π+γπ+γ ~2933/ = very small signal from a 1, even in p+p, S/B ~ %

RRC "Kurchatov Institute", Moscow S.Kiselev9 Au+Au: other centralities S/B ~ (dN ch /dy) -1 dN ch /dystatisticsS/B (%)S /√(S+B) / = / = / = / = Δ ++  π + p

RRC "Kurchatov Institute", Moscow S.Kiselev10 short-lived resonances: summary  Short-lived resonances: mass shift in p+p for some of resonances  estimations of signals from resonances f 0, Δ ++ and a 1 with TOF/ALICE have been made: - p+p: S/B ~ 10% (~0.004% for a 1 ) - Au+Au: S/B is smaller as S/B ~ (dN ch /dy) -1,  low signals from f 0 and Δ ++ - like-sign or event-mixing techniques should be used - to have S/√(S+B) ~10, 10 5 events are needed - S/B increases as a function of p t  Netx step: p+p simulations in the AliRoot package

Jets: motivation  Initial production at high-p T 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 gluon radiation Use jets and high-p T particles to probe the medium Goal: measure medium properties Density, temperature, number of degrees of freedom Dynamical properties e.g. viscosity 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 RRC "Kurchatov Institute", Moscow S.Kiselev

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

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

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 p hadron ~1-5 GeV/c even for the highest energy jets. We even don’t need jet reconstructions: instead of z we can use z’ = p hadron /E leading 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

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

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

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’ = p hadron /E leading particle or  ’=ln(E leading particle /p hadron )  analysis for different types of particles (π, K, p, φ…) Simulations in the AliRoot package RRC "Kurchatov Institute", Moscow S.Kiselev

RRC "Kurchatov Institute", Moscow S.Kiselev18 Prompt photons: pp data fit + binary scaling  PHENIX hep-ph/ (√s) 5 Ed 3 σ/d 3 p = F(x T,y)  One can use a data tabulation of the F(x T,y) to generate prompt photons.  A+B: Ed 3 N/d 3 p(b)= Ed 3 σ pp /d 3 p AB T AB (b)= Ed 3 σ pp /d 3 p N coll (b)/σ pp in  Nuclear effects (Cronin, quenching, …) are not taken into account.  Realization: GePP.C macros for ROOT

RRC "Kurchatov Institute", Moscow S.Kiselev19 GePP: results Comparison with RHIC data Prediction for LHC

RRC "Kurchatov Institute", Moscow S.Kiselev20 Bjorken -(1+1)-HydroDynamics (BHD) Proper time  and rapidity y Phys.Rev.D27(1983)140 There is no dependence on Lorenz boost variable y: Landau hydrodynamical model, viscosity and conductivity are neglected

RRC "Kurchatov Institute", Moscow S.Kiselev21 Photon spectrum in BHD Photon spectra follow from convoluting the photon production rates with the space–time evolution For a longitudinally expanding cylinder For proper time  and rapidity y ` For an ideal gas Main parameters: initial  0, T 0 and T f (at freeze-out) Connection with the local rest frame Input function – production rate E dN/d 4 xd 3 p (E,T) Phys.Rep.364(2002)98  0 ↔ yield, T 0 ↔ spectrum slope T f ↔ weak sensitivity, T f = 100 MeV

RRC "Kurchatov Institute", Moscow S.Kiselev22 Rates: HHG scenario  C.Song, Phys.Rev.C47(1993)2861 an effective chiral Lagrangian with π, ρ and a 1 mesons to calculate the processes 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

GeTP_HHG: SPS and RHIC data SPSRHIC RRC "Kurchatov Institute", Moscow S.Kiselev23 one can fit SPS data at high p t one can fit RHIC data but with not reasonable parameters

Rates from QGP -1 st order RRC "Kurchatov Institute", Moscow S.Kiselev24 Perturbative thermal QCD applying Hard Thermal Loop (HTL) resummation Phys.Lett.B510(2001)98

Rates from QGP -2 nd order RRC "Kurchatov Institute", Moscow S.Kiselev25 Thermal photon production in the QGP is a non-perturbative mechanism that can not be accessed in perturbative HTL resummed thermal field theory 2-loop contribution is the same order in α s 3-loop …. One must consider the QGP rates as an educated guess. PL B510(2001)98

Rates from QGP RRC "Kurchatov Institute", Moscow S.Kiselev26 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

GeTP_QGP: SPS and RHIC data SPSRHIC RRC "Kurchatov Institute", Moscow S.Kiselev27

GeTP_QGP: prediction for LHC RRC "Kurchatov Institute", Moscow S.Kiselev hydro, F.Arleo, D. d’Enterria, D. Peressounko, nucl-th/ The same τ 0, T 0 : steeper HHG spectrum in 1+1 due to radial flow in 2+1

Direct photon generators: summary RRC "Kurchatov Institute", Moscow S.Kiselev29 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, µ q =0, 1 st 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, …

Summary RRC "Kurchatov Institute", Moscow S.Kiselev30 The TOF/ITEP group activity ALICE physicsPWG 1. Short-lived resonancesPWG2 2. Jets compositionPWG4 3. Direct photon generatorsPWG4