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Prospects in ALICE for f mesons

International Conference on STRANGENESS IN QUARK MATTER Levoca, Slovakia – June 2007. Prospects in ALICE for f mesons. Daniel Tapia Takaki (Birmingham, UK) for the ALICE Collaboration. Structure of Talk. Resonances in ALICE ALICE Detector & PID capabilities

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Prospects in ALICE for f mesons

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  1. International Conference on STRANGENESS IN QUARK MATTER Levoca, Slovakia – June 2007 Prospects in ALICE for f mesons Daniel Tapia Takaki(Birmingham, UK) for the ALICE Collaboration

  2. Structure of Talk • Resonances in ALICE • ALICE Detector & PID capabilities • Simulation method & MC predictions • f signal and background predictions • Conclusions Daniel Tapia Takaki (Birmingham)

  3. Resonances in ALICE • ALICE is a general-purpose heavy-ion (HI) experiment designed to study the physics of strongly interacting matter and the Quark Gluon Plasma (QGP) in nucleus-nucleus collisions at the CERN LHC. • Resonances are a useful probe with which to study the QGP. (see Wed afternoon session). • ALICE will allow the study of resonance production in pp and Pb-Pb collisions. • This talk is devoted to the prospects of f meson productionat the ALICE experiment. ALICE: Physics Performance Report, Vol. II. B. Alessandro et al., ALICE Collaboration. J. Phys. G: Nucl. Part. Phys. 32 1295-2040, 2006. (See A. Badala talk on Thursday) Daniel Tapia Takaki (Birmingham)

  4. Interest in f production • Interesting due to its quark content. It is sensitive tostrangeness production. • It interacts weakly with non-strange hadrons in the hadronic phase due to its small cross section. • Several theoretical predictions suggest changes in the f mass and width due to medium-induced effects. • The f in hadronic and leptonic mode. The dileptons will have a different medium interaction. Proposed as a probe of chiral symmetry restoration. Daniel Tapia Takaki (Birmingham)

  5. Interest in f production in pp collisions Tevatron experiment E735, √s = 1.8 TeV • Production of the f can be measured early in the running of LHC, because of its narrow width, which gives it good S/B. • Interesting for itself, as one more hadronic measurement. Could be done at several energies. f measurements not very high precision at Tevatron, so even “low” energy points from LHC startup are interesting. 900 f->K+K- events <Pt>vs μ NΦ/Nh vs μ Mf = 1019 ± 2 (stat) MeV/c2 s =6.5 ± 0.7 (stat) MeV/c2 T. Alexopoulos, et al., Z. Phys. C. 67, 411-416 (1995) Daniel Tapia Takaki (Birmingham)

  6. HMPID PID (RICH) @ high pt TOF PID TRD Electron ID PMD g multiplicity TPC Tracking, dEdx ITS Low pt tracking Vertexing MUON m-pairs PHOS g,p0 The ALICE experiment • ITS - Tracking, vertex finding and PID by dE/dx. • Time Projection Chamber, used for tracking and particle identification (PID) by dE/dx. • TRD – tracking and electron identification. • TOF – Tracking and hadron identification by Time of Flight. ALICE studies both pp and Pb-Pb collisions. Daniel Tapia Takaki (Birmingham)

  7. Alice uses ~ all known techniques! p/K TPC + ITS (dE/dx) K/p e /p p/K TOF e /p K/p HMPID (RICH) p/K K/p 0 1 2 3 4 5 p (GeV/c) TRD e /p PHOS g /p0 1 10 100 p (GeV/c) ALICE Particle Identification capabilities Particle ID from low to high momenta.ALICE can combine the single detector PID information. Daniel Tapia Takaki (Birmingham)

  8. Detector simulation & MC predictions • The simulation of the pp (Pb-Pb) physics is generated by PYTHIA (HIJING). • The output is then passed to the ALICE simulation and reconstruction algorithm – using the ALICE offline computing framework known as AliRoot. • Results from fast-simulation (pp) and detailed simulation (Pb-Pb) are presented. PYTHIA’s prediction for pp mb at ALICE. Rapidity distribution for the f meson at the generation level. Daniel Tapia Takaki (Birmingham)

  9. ~ 1 hr nominal run.Inv. Mass with no PID. Background estimation • A good estimation of the shape and size backgrounds is essential for the study of resonances measurement. • Like-sign and mixed events are popular techniques. • Both methods were implemented in AliRoot. PYTHIA pp mb @ 14 TeV cms energy 4x106 events – No PID was used. K+K- spectrum Mass (GeV/c2) Daniel Tapia Takaki (Birmingham)

  10. Background estimation (2) PYTHIA pp mb @ 14 TeV cms energy Ratio of same-event background to Like-sign same event inv. Mass. • Either method works well. This agrees with reported results. Physical Review C 72 014903 (2005). K+K- spectrum • Same-event background • Like-sign same-event Same-event background Like-sign same-event 2x106 events. K+K- spectrum • Same-event background • Like-sign same-event • Mixed event Daniel Tapia Takaki (Birmingham)

  11. Background estimation (3) PYTHIA pp mb @ 14 TeV cms energy 2x106 events. Ratio of Like-sign same event to mixed event mass distribution. • The ratio of same to mixed event for the K+K+ and K-K- pairs. • The signal can be obtained subtracting the background from either method. K+K+ pairs K+K+ pairs Same event Mixed event Mass Mass Ratio of Like-sign same event to mixed event mass distribution. K-K- pairs K-K- pairs Mass Mass Daniel Tapia Takaki (Birmingham)

  12. Number of f found consistent with the number generated. Signal – background subtracted PYTHIA pp mb @ 14 TeV cms energy • Reconstructed mass and width consistent with generated. ΦK+K- Background subtracted Like-sign • 2 x106 PYTHIA mb pp events. • Fast-simulation results. • Perfect PID. Daniel Tapia Takaki (Birmingham)

  13. ~ 1 hr nominal run.Inv. Mass with no PID. Results in Proton-Proton collisions with no PID PYTHIA mb pp @ 14 TeV cms energy • ALICE should be able to measure the f meson early in the LHC running - even before the PID system become available. K+K- spectrum 4x106 events – No PID was used. Mass (GeV/c2) 2.4<Pt<2.6 GeV ΦK+K- 2.4<Pt<2.6 GeV Daniel Tapia Takaki (Birmingham)

  14. ~ 1/2 min nominal run. f meson in Pb-Pb collisions HIJING Pb-Pb @ 5.5 TeV ΦK+K- Reconstructed transverse-momentum K- K+ f K+K- K+K-spectrum • 4,000 HIJING central Pb-Pb events. • Detailed simulation method. • Perfect PID Daniel Tapia Takaki (Birmingham)

  15. Conclusions • The ALICE experiment will allow the study of resonances in great detail. It has excellent PID. A study of the f meson in hadronic (and leptonic) decay channels will be possible. • Like-sign and mixing-event were tested for background subtraction. They give consistent result. • The f analysis might be one of the first resonance measurements in ALICE because of its good S/B ratio. • ALICE should be able to study the f meson in pp collisions before the PID system become available. • In Pb-Pb collisions the f meson can also be measured (even with small statistics). Daniel Tapia Takaki (Birmingham)

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