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\title{
Hadronic composition as a characteristics of jet quenching at the LHC
}
\author{Sebastian Sapeta$^{1}$\\
$^1$M. Smoluchowski Institute of Physics, Jagellonian University,\\
   Reymonta 4, 30-059 Cracow, Poland}

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There are several
mechanisms which may lead to modification of the hadronic composition of jets (hadrochemistry), {\it e.g.} exchange of quantum numbers (color, flavor, baryon number) between projectile and the medium, recombination of partons from the jet with partons from the medium as well as recoil effects.
All the above may require serious modeling.  Instead, we consider the framework which takes into account only the exchange of momentum between the medium and the developing partonic cascade.

To calculate single particle distributions of identified hadrons we use the framework of Modified Leading Logarithmic Approximation (MLLA) \cite{Dokshitzer}. This perturbative approach combined with the hypothesis of Local Parton-Hadron Duality (LPHD) was shown to reproduce correctly 
not only the distributions of all charged particles but also the spectra of identified hadrons such as pions, kaons and protons \cite{Azimov:1984np, Azimov:1985by}. 
To model the medium-modification of jets we supplement the above formalism by the formulation of parton energy loss proposed in~\cite{Borghini:2005em}. The effects of medium-induced gluon radiation are introduced by enhancing the singular parts of the leading order splitting functions by the factor $1+f_{\rm med}$. This leads to the softening of hadron spectra. The model accounts for the nuclear modification factor at RHIC when $f_{\rm med}$ is of the order of 1. 

Our main result are  the rations of $K^{\pm}/\pi^{\pm}$ and $p^{\pm}/\pi^{\pm}$
 \cite{Sapeta:2007ad}. We observe a significant difference between the ratios in vacuum and medium jets. According to our analysis, 
in the presence of medium the ratios increase up to 50\%  for kaons and 100\% for protons. This enhancement seems to be a generic feature for radiative energy loss jet quenching models.
In addition we observe only mild dependence on the the jet energy and the jet opening angle.
The medium modified hadron spectra may be also superimposed on the high multiplicity environment of heavy ion collisions expected at the LHC.
We have checked that due to the characteristically different hadrochemistry of the jet and the background our result concerning the ratios 
remains virtually unchanged. 
Hence, we conclude that the hadrochemical composition of jets may be
very fragile to the medium effects and could be used as an additional handle to study microscopic mechanisms underlying the jet quenching phenomenon.  


%%% REFERENCES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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%  ``Distorting the hump-backed plateau of jets with dense QCD matter'',
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%\cite{Sapeta:2007ad}
\bibitem{Sapeta:2007ad}
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  %``Jet hadrochemistry as a characteristics of jet quenching,''
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\end{thebibliography}

\end{document}

