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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 = 1.019 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

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The Φ meson spectrum can be described by the same parameters as the protons’ ones

(->relevance of the mass)

Mass 1.019 GeV & proton mass

Φ meson is suppressed respect to protons as pions

(-> relevance of the quark content!)

Eur.Phys.J.C43:317-322,2005

Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

Φ meson at Pt > 2 GeV/chttp://home.physics.ucla.edu/calendar/conferences/sqm2006/agenda/talks/2006_03_26/session_1/blyth_sarah-louise.pdf

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Φ meson at Pt > 2 GeV/c

It’s 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, 172301 (2003) )

HMPID can identify

protons up to 5 GeV/ckaons up to 3 GeV/c (-> Φ up to 6 GeV/c [both K] )

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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

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SIMULATION 175 103 Pb-Pb central collisions

in the AliRoot Framework

No ReconstructionHijing Generator

√sNN = 5.5 TeV

1. Pure Kinematics 2. Momentum SmearingAccording to the data from (ALICE-INT-2003-067 [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. MΦ(K+K-) using the sample of selected kaons

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ΘC reconstructed by the fast simulation

selected sample of ΘC

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

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Sample selected

P TΦ > 2.6 GeV/c

2.6 GeV/c < PTΦ < 6 GeV/c

No ID of the charged particles

Kaons 1.3 GeV/c < P < 3 GeV/c

PID cut 80%

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Study of Φ and f2(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]” & http://pdg.lbl.gov/~reviews/rppref/mini/2006/dalitz_analysis-web.pdf

SIGNAL & BACKGROUND

)(1)(

)(

mBWq

mmBKG

dm

dN

m

mbth emmmBKG )()(

m

mmmmmmpq mm

2*

2/1221

2221

2

)()(

RSLm

M

p

qm

MmMm

mmBW

PDGm

PDGPDG

*)(

)(

)()(

)(

22222

Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare

P TΦ > 2.6 GeV/c

NΦ fit = 165454 ± 758 NΦAliRoot = 166568

ΓΦ = 4.43 ± 0.08 MeV/c2 RSL = 1.2 MeV/c2

MΦ = 1019.6 MeV/c2 (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

CommentsBefore 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

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P TΦ > 6 GeV/c

[without identification]

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Pt spectrum olf the Φ

…ok…

…but…

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Pt spectrum - Detail

Systematic shift towards higher slopes due to a systematic effect

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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 !

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-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. It’s possible to study both p and Φ production in order to look deeper at mass/quark effects

Conclusions

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