Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare Φ meson detection with HMPID Annalisa Mastroserio University of Bari, INFN (Bari) Outline Importance of the Φ meson Φ meson at Pt > 2 GeV/c HMPID in ALICE Preliminary results of Φ meson identification using HMPID More on HMPID performances Conclusions

Brief summary on Φ meson Mass = GeV Quark content ss Decay channels leptonic + hadronic Mean Life (~50 fm/c) compatible with the time duration of the colllision Compatible with the proton mass => Distinguish mass effects from meson/baryon type dipendencies Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

The Φ meson spectrum can be described by the same parameters as the protons ones (->relevance of the mass) Mass GeV & proton mass Φ meson is suppressed respect to protons as pions (-> relevance of the quark content!) Eur.Phys.J.C43: ,2005 Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Φ meson at Pt > 2 GeV/c Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Φ meson at Pt > 2 GeV/c Its not clear the Φ production at intermediate Pt -> this would support models which depend on the number of constituent quarks or models which depend upon just the mass of the particle and this would give new insights for the anomalous proton yield at Pt~2-5 GeV/c (Phys.Rev.Lett. 91, (2003) ) HMPID can identify protons up to 5 GeV/c kaons up to 3 GeV/c (-> Φ up to 6 GeV/c [both K] ) Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

HMPID detector geometry According to Hijing particle ratios we expect the number of Φ at Pt>2 GeV/c is ~ 1 per event at midrapidity ~ 5 m ! Fast Simulation needed Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

SIMULATION Pb-Pb central collisions in the AliRoot Framework No Reconstruction Hijing Generator s NN = 5.5 TeV 1. Pure Kinematics 2. Momentum Smearing According to the data from (ALICE- INT [B.Batyunya, A.De Caro, G.Paic, A.Pesci, S.Zaporozhets]) 3. K selection 1.3 GeV/c < P < 3 GeV/c |η|< 0.9 ID probability > 80% 4. M Φ (K + K - ) using the sample of selected kaons Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Θ C reconstructed by the fast simulation selected sample of Θ C ID Probability > 80% No cut on probability Contamination of kaons for the ID probability cut is 10% 2.5 GeV/c < P < 3 GeV/c Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Sample selected P TΦ > 2.6 GeV/c 2.6 GeV/c < P TΦ < 6 GeV/c No ID of the charged particles Kaons 1.3 GeV/c < P < 3 GeV/c PID cut 80% Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Study of Φ and f 2 (1270) MESON POLARIZATION AT Pt >2 GeV/c IN π - Be INTERACTIONS AT CERN SPS [WA77 Collaboration ] + modification according to Review of Particle physics [Physics Letters B] & SIGNAL & BACKGROUND Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

P TΦ > 2.6 GeV/c N Φ fit = ± 758 N ΦAliRoot = Γ Φ = 4.43 ± 0.08 MeV/c 2 RSL = 1.2 MeV/c 2 M Φ = MeV/c 2 (fixed) S/B = 0.05 S/ S+B = 94 No corrections for -HMPID geometrical acceptance (5%) - Tracking efficiency (constant ) BW of the previous fit Event mixing Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Comments Before the fitted width was tuned (it was ~ 5.53 MeV!) The generation of Φ has some properties : -The Φ s are generated according to a simple Breit Wigner (not a relativisic one) - the tails are truncated and the fitting procedure takes into account such a discontinuity Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

P TΦ > 6 GeV/c [without identification] Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Pt spectrum olf the Φ …ok… …but… Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Pt spectrum - Detail Systematic shift towards higher slopes due to a systematic effect Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

More on HMPID …. 1 Kaon at 0.5 T 2 kaons at 0.5 T Kaons (as Φ decay products) : acceptance of the modules Difficult to do in a Fast Simulation ! Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

-The fit is sentive to a possible encrease in the Φ width -The HMPID can raise the Φ momentum interval (Pt spectrum) up to 6 GeV/c ( -> production processes in Φ formation) - studies about Φ detection at higher Pt - The results coming from the PDC 06 would be very interesting for the shape of the invariant mass spectrum of the Φ using HMPID -HMPID can identify protons up to 5 GeV/c. Its possible to study both p and Φ production in order to look deeper at mass/quark effects Conclusions Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare