26.03.2009 Task-Force meeting, CERN S.Kiselev

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Jet hadrochemistry with ALICE. An idea.

• Sergey Kiselev, ITEP Moscow for the TOF group

• Medium modifications of jet hadrochemistry• ALICE PID performance• Methods, variables, …• Jet hadrochemistry in p+p at LHC• Next steps• Conclusions

Medium modifications of jet hadrochemistry

26.03.2009 Task-Force meeting, CERN S.Kiselev

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S.Sapeta, U.A.Wiedemann EPJ, C55, 293 (2008)A unique prescription of how to model the medium modification of jet fragmentation does not exist.

Medium modification of jets depends on the exchange of- momentum- color- flavor- baryon number

between the partonic projectile and the medium

A simple model of a parton shower with enhanced medium induced branching but unmodified hadronization is used. Parton splitting functions Pq→qg , … are enhanced by one common model-independent factor (1+fmed).

Since the model does not implement other effects, it may be expected to underestimate the medium modifications of jet hadrochemistry.

No medium modificationMLLA (modified leading logarithmic approximation)

+ LPHD (local parton–hadron duality) formalism

26.03.2009 Task-Force meeting, CERN S.Kiselev

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Fig.2. Two examples for the comparison of the MLLA+LPHD formalism with data on single inclusive spectra inside a jet as a function of the logarithm of the hadron momentum fraction ξ. (a) The distribution (4) of charged pions (π+ + π−), kaons (K+ + K−) and (anti-) protons (p + pbar) in a jet of energy Ejet = 14.5 GeV, compared to TPC data on e+e− collisions. The MLLA parameters are Λ = 155 MeV and KLPHD = 1.22. (b) The MLLA+LPHD distribution of all charged hadrons in a jet of energy Ejet = 108 GeV for various opening angles Θc, compared to CDF data from p pbar collisions. The MLLA parameters are Λ = Q0 = 235 MeV, KLPHD = 0.555

Particle ratios vs pT

26.03.2009 Task-Force meeting, CERN S.Kiselev

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~50 – 100% medium effect

Cone opening angle Θc = 0.28

Jet modification factor JAA

26.03.2009 Task-Force meeting, CERN S.Kiselev

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dNh/dpT (med) JAA = ---------------- dNh/dpT (vac)

A significantly modified jethadrochemistry can be expected

Increases with mh and Ejet

Maximum effect at pT ~ 5 GeV/c

TOF PID performance

• One can study jet hadrochemistry with TOF at 0.5 < pT < ~3-5 GeV/c

26.03.2009 6Task-Force meeting, CERN S.Kiselev

ALICE PID performance

26.03.2009 Task-Force meeting, CERN S.Kiselev

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… with ALICE at pT < ~30 GeV/c

Methods, variables, …

26.03.2009 Task-Force meeting, CERN S.Kiselev

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Methods:- jet reconstruction- a la RHIC triggered particle azimuthal correlations

Variables for each of species (π± , K± , p± ):- multiplicity- longitudinal distributions- transverse distributions

- ratios K±/π± , …

Systems:- pp, PYTHIA, HERWIG, … - pA , HIJING, … - AA, HIJING, PYQUEN, …

Jet hadrochemistry in p+p at LHC

26.03.2009 Task-Force meeting, CERN S.Kiselev

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There are theoretical speculations that at LHC energies “medium”/”collective state” can be created even in p+p(due to multiple scattering)

If so, jet hadrochemistry and other characteristics of jet quenching can be used to “feel” the medium as deviations from vacuum values

Next steps

26.03.2009 Task-Force meeting, CERN S.Kiselev

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at generator level:- comparison generator predictions with data

(single inclusive spectra, … for π± , K± , p±) inside a jet

- sensitivity to a generator …

In the AliRoot package:- a task/macro to start analysis for pp on CAF

…

Conclusions

26.03.2009 Task-Force meeting, CERN S.Kiselev

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“The analysis of the hadrochemical composition of jets in heavy ion collisions is a terra incognita, for which data are not available yet. It is in experimental reach of the LHC.”(S.Sapeta, U.A.Wiedemann EPJ, C55, 293 (2008))

ALICE PID performance let us study medium modifications of jet hadrochemistry