Post on 27-Mar-2015
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 = 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
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 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%
Annalisa Mastroserio ALICE meeting Italia – Vietri Sul Mare
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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