Vietri sul Mare, 30 Maggio 2006 II Congresso Nazionale sulla Fisica di ALICE A. De Caro 0.

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Vietri sul Mare, 30 Maggio 2006 II Congresso Nazionale sulla Fisica di ALICE

A. De Caro 1

Mesone in ALICE

A. De Caro, D. De Gruttola, C. Guarnaccia

Gruppo ALICE TOF

A. De Caro 3

Outlet

· meson as investigation probe for QGP formation;

· experimental results for ;

· @ ALICE PPRv2;

· @ ALICE PDC04;

· Conclusions.

A. De Caro 4

meson as QGP signature

· Strangeness enhancement as probe of (partial) chiral symmetry restoration

J. Rafelsky, B. Müller, Phys. Rev Lett. 48 (1982) 1066,

P. Koch, B. Müller, J. Rafelsky, Phys. Rep. 142 (1985) 167;

· Enhancement of meson (lightest vector meson with hidden strangeness)

A. Shor, Phys. Rev. Lett. 54 (1985) 1122,H. Sorge et al., Phys. Lett., B289 (1992) 6,A.J. Baltz and C. Dover, Phys. Rev. C53 (1996)

· Modification of meson resonance spectrumR. D. Pisarski, Phys. Lett. B110 (1982) 155,T. Hatsuda, Nucl. Phys. A544 (1992) 27c,M. Asakawa, C. M. Ko, Phys. Rev. C48 (1993)

526R,P. Fachini, in proc. of QM2004 (2004),

nucl-ex/0403026,L. Hot, K. Haglin, nucl-ex/0409036 (2004).

A. De Caro 5

meson as QGP signature

A. Mischke for NA49 collaboration, hep-ex/0311010

A. De Caro 6

Actual Pairs

Background

signal : 1410131

(within the window of 1.014<m<1.024 )

S/B = 1/6

Mass peak position and width are consistent with the PDB value

Relativistic Breit-Wigner convoluted with a Gaussian

PHENIX results:PHENIX results:KK++KK-- signal from the TOF-TOF pairs signal from the TOF-TOF pairs

M. Muniruzzaman for PHENIX Coll. @ SQM03J.Phys. G30 (2004) S571-S574

A. De Caro 7

STAR results: STAR results: KK++KK-- signal signal

STAR Coll., nucl-ex/0306013

A. De Caro 8

meson detection @ LHC with ALICE experiment: in PPR 2nd volume

· B. Batyunya, N. Slavin, G. Paic, ALICE-INT-1997-26;

· B. Batyunya, A. De Caro, G. Paic, A. Pesci and S. Zaporozhets, ALICE-INT-2003-67; Phys.Part.Nucl.Lett.2:110-115 (2005);

· A. De Caro, A. Pesci and S. B. Sellitto for ALICE-TOF group, K+K- in TOF acceptance (|| ≤ 1, full azimuthal coverage and 0.5 GeV/c ≤ pT ≤ 2.5(3) GeV/c)

· two Ph. D. thesis;

· “Study of QGP signatures on K+K- signal in Pb-Pb ALICE events”, to appear in Eur. J. Phys. (2005);

· B. Batyunya, K+K- at high pT without PID.

A. De Caro 9

Simulation strategy

1st step: full detector simulation• 250 central HIJING events, tracked with B=0.4 T

2nd step: event generation according to• parameterized mT and y distributions for primary particles

(K±, and )

• corrected for track reconstruction momentum and angular resolutions

106 events in the full pT region with PID information

A. De Caro 10

K+K- invariant mass spectrum

Background estimate:

like sign distribution,

i.e. K+K++K-K-

and K+K+ (same event).

More studies have to be done because of different shapes between the like-sign and unlike-sign distributions in the real life.

A. De Caro 11

(K+K-): signal extrapolation

· Five (free) fitting parameters:· A, spectrum area,· m0, mean value,· , FWHM of the Breit-

Wigner resonance,· , standard deviation of the

Gaussian distribution,· B, residual bkg level.

· Some results:m0 = (1019.39±0.05) MeV/c2

= (4.3 ± 0.5) MeV/c2

= (1.2 ± 0.1) MeV/c2

BWG(m) = A1

(m'−m0)2 +Γ 2

2πσe

−(m−m' )2

2σ 2dm' + B

A. De Caro 12

K+K- significance

STPCBTPC + STPC

STOFBTOF + STOF

STOForTPCBTOForTPC + STOForTPC

Signal and bkg pairs counted in the mass window: mK+K- - m0 < /2

A. De Caro 13

K+K- @ ALICE PDC04

· 3840 HIJING events, b [0;5] fm· Kinematics tree (Monte Carlo informations)· Reconstructed track tree (miniESD):

· TPC or ITS refit ok;

· it exists a PID value;

· reconstructed till the primary (reconstructed) vertex .

A. De Caro 14

Analysis on Monte Carlo

A. De Caro 15

Analysis on miniESD tree: PID and MC parameter infos

A. De Caro 16

Analysis on miniESD tree: PID and ESD parameter infos

A. De Caro 17

K+K- combinatorial background

K+K- pairs

true K+ + true K-

true K+ + false K-

true K- + false K+

false K+ + false K-

A. De Caro 18

Conclusions

· PPR results vs PDC04 analysis· combinatorial background enhanced due to kaon

contamination;· to reproduce PPR results for ->K+K-, we need:

· more statistics, more then one million of central event.

· In the meanwhile we are working out appropriate cuts to enhance the signal-to-background ratio.

· We are ready to analyze the PDC06 data.

A. De Caro 19

ALICE PID performances @ PDC04

· True identified kaons/ reconstructed tracks identified as kaonsvs (reconstructed) momentum

· Kaon contamination: False identified kaons/ reconstructed tracks identified as kaonsvs (reconstructed) momentum

A. De Caro 20

· True identified kaons/ reconstructed tracks identified as kaonsvs (reconstructed) polar angle

· Kaon contamination: False identified kaons/ reconstructed tracks identified as kaonsvs (reconstructed) polar angle

A. De Caro 21

· True identified kaons/ reconstructed tracks identified as kaonsvs (reconstructed) azimuthal angle

· Kaon contamination: False identified kaons/ reconstructed tracks identified as kaonsvs (reconstructed) azimuthal angle

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≤ 150 000

A. De Caro 24

~ 300 000

Vietri sul Mare, 30 Maggio 2006 II Congresso Nazionale sulla Fisica di ALICE A. De Caro 0.

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