Документ взят из кэша поисковой машины. Адрес оригинального документа : http://nuclphys.sinp.msu.ru/conf/epp10/Kiselev.pdf Дата изменения: Sat Sep 7 17:46:32 2013 Дата индексирования: Fri Feb 28 02:29:46 2014 Кодировка:

Hadronic resonance production with the ALICE experiment in pp and Pb-Pb collisions at LHC energies
Sergey Kiselev (ITEP Moscow) for the ALICE collaboration

ITEP

· · · · ·

Motivation Analysis details pp@7 TeV: K*(892)0, (1020), (1385) Pb-Pb@2.76 ATeV: K*(892)0, (1020) Summary
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Motivation
·
pp collisions: reference fo
Resonance K*(892)
0

r tuning QCD-inspired event generators

(MeV) 50 4.3 36

c (fm) 4 46 6

Decay +K K+ + K + ±
-

(1020)

the baseline for heavy-ion collisions

(1385)±

·

AA collisions: restoration o

f chiral symmetry modification of width, mass and branching ratio

regeneration and rescattering effects timescale between chemical and kinetic freeze-out

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ALICE detector

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Particle identification, centrality in Pb-Pb
TPC resolution ~ 5 - 6% TOF resolution ~ 90 ps

Pb-Pb: centrality selection using VZERO data collected by ALICE during 2010 and used for resonance analyses: pp@7 GeV: ~ 60 Mevents for K*, ~ 200 Mevents for * Pb-Pb@2.76 AGeV: ~ 10 Mevents central rapidity region: |y| < 0.5
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pp: signal extraction
K*
ALICE Coll. EPJ C72(2012)2183



*

combinatorial background: mixed-event or like-sign techniques fit: Breit-Wigner (Voigtian for ) + polynomial
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pp: pT spectrum
K*
ALICE Coll. EPJ C72(2012)2183



*

PYTHIA Perugia 2011
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pT < 2 GeV/c: PYTHIA D6T pT > 3 GeV/c: PYTHIA Perugia 2011
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The models underpredict the data
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pp: < pT >

resonance < pT > in agreement with the trend drawn by other particles at 7 TeV < pT > for , K and p in pp at s = 200 GeV, Phys.Rev.C 79(2009)34909, is still compatible with ISR parameterization (s = 25 GeV, Nucl.Phys.B 114(1976)334 )
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pp: particle ratios
ALICE Coll. EPJ C72(2012)2183

K*/K

-

/K*

both K*/K- and /K* independent of s
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pp: particle ratios
/
ALICE Coll. EPJ C72(2012)2183

/

/: saturates above 200 GeV /K

/: not reproduced by Pythia Perugia 2011

agreement with a prediction of HIJING/BB model with a Strong Color Field modeled with increased string tension
/K: independent of s
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pp: particle ratios
*

*/- : independent of s */K- : independent of s */- : hint of a decrease with s
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*/- and */K- : agree with Becattini thermal model (arXiv:0912.2855), s = 0.6, T=170 MeV
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Pb-Pb: signal extraction
K*

combinatorial background: mixed-event or like-sign techniques fit: Breit-Wigner (Voigtian for ) + polynomial
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Pb-Pb: mass and width
K*

masses and widths compatible with PDG values
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Pb-Pb: pT spectrum
K*

fit: Blast-Wave function, Phys.Rev. C48(1993)2462
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Pb-Pb: < pT >
K*

< pT >

LHC

> < pT >

RHIC

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Pb-Pb: particle ratios vs. < N
K*

part

>



K*0/K- : hint for a decreasing trend a possible increase in rescattering effects for central collisions

/, /K : independent of collision centrality

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Pb-Pb: particle ratios vs. s
K*

NN



(K*/K)AA < (K*/K)pp rescattering effects ?
Thermal models: Andronic et al., Phys.Lett.B 673(2009)142 Torrieri/Rafelski, J.Phys.G 28(2002)1911 GC Thermal model, J.Phys.G 38(2011)124081 22-28 Aug 2013

/, /K : independent of s
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Pb-Pb: R
R
AA

AA

and RCP
R
CP

1/Ncoll d(AA)/dpT = -----------------------d(pp)/dpT

1/Ncoll (0-20%) d(0-20%)/dpT = ----------------------------------------1/Ncoll (60-80%) d(60-80%)/dpT

RAA (,K) R
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AA

( ) R

AA

(p)

RCP(K*) tends to be lower than RCP(), but same within uncertainties
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Summary: pp
pp@7 TeV: K*(892)0, (1020), (1385)
none of PHOJET and PYTHIA tunes give a fully satisfactory description of pT spectrum. In particular they underestimate strange baryon resonances yields
particle ratios: o K*/K-, K*/ and /K are independent of s o /: saturates above s = 200 GeV o /: not reproduced by PYTHIA, agrees with HIJING/BB model with a Strong Color Field modeled with increased string tension o */- and */K- : independent of s, agree with the thermal model o */- : hint of a decrease with s, overpredicted by the thermal model

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Summary: Pb-Pb
Pb-Pb@2.76 ATeV: K*(892)0, (1020)
masses and widths compatible with PDG values

< pT >

LHC

> < pT >

RHIC

particle ratios: o /K , / independent of collision centrality and s o K*/K- hint of decrease with centrality rescattering effects ? o (K*/K-)AA < (K*/K-)pp rescattering effects ? RAA and RCP: o high pT suppression in central events o RAA (,K) RAA () RAA (p)

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