1. 26.03.2009Task-Force meeting, CERN S.Kiselev 1 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

2. Medium modifications of jet hadrochemistry 26.03.2009Task-Force meeting, CERN S.Kiselev 2 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 P q→qg, … are enhanced by one common model-independent factor (1+f med ). Since the model does not implement other effects, it may be expected to underestimate the medium modifications of jet hadrochemistry.

3. No medium modification MLLA (modified leading logarithmic approximation) + LPHD (local parton–hadron duality) formalism 26.03.2009Task-Force meeting, CERN S.Kiselev 3 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

4. Particle ratios vs p T 26.03.2009Task-Force meeting, CERN S.Kiselev 4 ~50 – 100% medium effect Cone opening angle Θ c = 0.28

5. Jet modification factor J AA 26.03.2009Task-Force meeting, CERN S.Kiselev 5 dN h /dp T (med) J AA = ---------------- dN h /dp T (vac) A significantly modified jet hadrochemistry can be expected Increases with m h and E jet Maximum effect at p T ~ 5 GeV/c

6. TOF PID performance One can study jet hadrochemistry with TOF at 0.5 < p T < ~3-5 GeV/c 26.03.20096Task-Force meeting, CERN S.Kiselev

7. ALICE PID performance 26.03.2009Task-Force meeting, CERN S.Kiselev 7 … with ALICE at p T < ~30 GeV/c

8. Methods, variables, … 26.03.2009Task-Force meeting, CERN S.Kiselev 8 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, …

9. Jet hadrochemistry in p+p at LHC 26.03.2009Task-Force meeting, CERN S.Kiselev 9 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

10. Next steps 26.03.2009Task-Force meeting, CERN S.Kiselev 10 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 …

11. Conclusions 26.03.2009Task-Force meeting, CERN S.Kiselev 11 “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