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f 0 , Δ ++ , a 1 with ALICE

f 0 , Δ ++ , a 1 with ALICE. Sergey Kiselev, ITEP Moscow for the TOF group Introduction Input info and assumptions Acceptance Signal and background p+p Au+Au Summary. Introduction. SQM’07: short-lived resonances, motivation + last results.

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f 0 , Δ ++ , a 1 with ALICE

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  1. f0, Δ++, a1 with ALICE • Sergey Kiselev, ITEP Moscow for the TOF group • Introduction • Input info and assumptions • Acceptance • Signal and background • p+p • Au+Au • Summary INFN, Bologna S.Kiselev

  2. Introduction SQM’07:short-lived resonances, motivation + last results 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)  Λπ 88 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. Life Time f0, Δ++ and a1 will be analyzed INFN, Bologna S.Kiselev

  3. Introduction – 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 ?) INFN, Bologna S.Kiselev

  4. Introduction – 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. INFN, Bologna S.Kiselev

  5. Input info – resonance parameters PYTHIA mass 1.0 width 0.0 Br.rat. decay products 0.520000 pi+ pi- 0.260000 pi0 pi0 0.110000 K+ K- 0.055000 K_L0 K_L0 0.055000 K_S0 K_S0 PDG f0 • mass 980 MeV, width 70 MeV, K+K-/π+π- with BR=0.11/0.52 mf < 2mK=988 MeV a1  mass 1260 MeV, width 400 MeV, πγ with Br=1 (enlarge statistics) INFN, Bologna S.Kiselev

  6. Input info and assumptions • Background: SHAKER events • dNch/dy = const • pt distribution: π – fit to Tevatron data, others – mt scaling • 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 resolusion σp/p = 1% • No matter between a target and TOF/PHOS  optimistic estimation of the signals INFN, Bologna S.Kiselev

  7. Input and assumptions - ratios nucl-ex/0305034 nucl-ex/0403010 nucl-ex/0403026 nucl-ex/0510033 INFN, Bologna S.Kiselev

  8. Input and assumptions - spectra nucl-ex/0305034 nucl-ex/0510033 mT scaling steeper than data INFN, Bologna S.Kiselev

  9. Geometrical acceptance TOF: | - 900|<450 PHOS: | - 900|<100 Δ = 1000 INFN, Bologna S.Kiselev

  10. p+p: signal and background p+p at LHC  106 SHAKER events with dNch/dy = 5 f0 K+K- f0 π+ π- like-sign orevent-mixing techniques should be used INFN, Bologna S.Kiselev

  11. p+p: signal and backgroud Δ++  π+p a1+  π+γ like-sign or event-mixing techniques should be used INFN, Bologna S.Kiselev

  12. p+p: S/B(2σ) even in p+p, signal from a1 is very small (real BR ~1%), S/B ~ 10-3 % ! INFN, Bologna S.Kiselev

  13. p+p: S/B vs pt for pt study higher statistics, ~ 107, is needed INFN, Bologna S.Kiselev

  14. p+p: S/B vs pt INFN, Bologna S.Kiselev

  15. peripheral Au+Au: signal and backgroud f0 K+K- • dNch/dy = 2000  0 - 5 % centrality bin of Au+Au • dNch/dy = 125  60-65 % centrality bin of Au+Au • 104 SHAKER events with dNch/dy = 125 INFN, Bologna S.Kiselev

  16. peripheral Au+Au: signal and backgroud f0 π+ π- Δ++  π+p INFN, Bologna S.Kiselev

  17. p+p vs peripheral Au+Au S ~ dNch /dy, if B ~ (dNch/dy)2 S/B ~ (dNch/dy)-1, S/√(S+B) does not depend on dNch/dy to have S/√(S+B) ~ 10 ~105 events of a given centrality bin are needed INFN, Bologna S.Kiselev

  18. Au+Au: other centralities Δ++  π+p for Δ++it works! S/B ~ (dNch/dy)-1 INFN, Bologna S.Kiselev

  19. A question to the STAR team • f0 π+π- : ~107 min.bias p+p events ~106 Au+Au (40% - 80%) events dNch/dy = 125 - 20 • Δ++π+ p : ~6 106min.bias p+p events ~2 106Au+Au min.bias ~2 106Au+Au central ~107 d+Au min.bias dNch/dy = 4 - 15 • No info on S/B, only spectra and ratios • No a detailed paper, only short papers (SQM’03, QM’04, QM’05) • What are the S/B values? INFN, Bologna S.Kiselev

  20. Summary • estimations of signals from the f0, Δ++ and a1 resonances with ALICE have been made • p+p: S/B ~ 10% for f0 and Δ++, ~10-3 % for a1 • Au+Au: S/B is smaller and follows S/B ~ (dNch/dy)-1, S/√(S+B)does not depends on dNch/dy • like-sign orevent-mixing techniques should be used to extract a signal • to have S/√(S+B)~10, 105 events of a given centrality are needed • S/B increases as a function of pt ~107 events are needed for the pt study INFN, Bologna S.Kiselev

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