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\begin{center}{\bf Medium modified Fragmentation Functions: overview}\end{center}

%\vspace{12pt}

\centerline{ {\bf Carlos~A.~Salgado}$^{\rm a}$ }

%\vspace{12pt}

\begin{center}
$^{\rm a}$Departamento de F\'\i sica de Part\'\i culas and IGFAE, \\ Universidade de Santiago de Compostela, Spain \\
E-mail: {\it carlos.salgado@cern.ch}
\end{center}
%\vspace{12pt} %\vspace{12pt}

Medium-induced gluon radiation is usually identified as the dominant dynamical mechanism underling the {\it jet quenching} phenomenon observed in heavy-ion collisions (see e.g. \cite{CasalderreySolana:2007pr} for a recent review on the calculation of the spectrum and the corresponding phenomenological implementation). In its present implementation, multiple medium-induced gluon emissions are assumed to be independent, leading, in the eikonal approximation, to a Poisson distribution \cite{Salgado:2003gb}.

In \cite{Armesto:2007dt} we have introduced a medium term in the splitting probabilities 
%
\begin{equation}
P^{\rm tot}(z)= P^{\rm vac}(z)+\Delta P(z,t),
\label{eq:medsplit}
\end{equation}
%
so that both medium and vacuum contributions are included on the same footing in a DGLAP approach. In (\ref{eq:medsplit}), $\Delta P(z,t)$ is taken directly from the medium-induced gluon radiation spectrum %
\begin{equation}
\Delta P(z,t)\simeq \frac{2 \pi  t}{\alpha_s}\, 
\frac{dI^{\rm med}}{dzdt} ,
\label{medsplit}
\end{equation}
%
computed in the multiple scattering approximation \cite{Wiedemann:2000za}.

The improvements include energy-momentum conservation at each individual splitting, medium-modified virtuality evolution and a coherent implementation of vacuum and medium splitting probabilities. Noticeably, the usual formalism is recovered when the virtuality and the energy of the parton are very large. This leads to a similar description of the suppression observed in heavy-ion collisions with values of the transport coefficient of the same order as those obtained using the {\it quenching weights}.

Noticeably, in a previous publication \cite{Polosa:2006hb} it has been found that this formalism would lead to non-trivial angular dependences of the jet profiles when kinematic constrains are imposed. Similar structures were found at RHIC in two-particle correlations in the away side \cite{:2008cq}.

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\begin{thebibliography}{99}

%\cite{CasalderreySolana:2007pr}
\bibitem{CasalderreySolana:2007pr}
  J.~Casalderrey-Solana and C.~A.~Salgado,
  %``Introductory lectures on jet quenching in heavy ion collisions,''
  arXiv:0712.3443 [hep-ph].
  %%CITATION = ARXIV:0712.3443;%%

\bibitem{Salgado:2003gb}
  C.~A.~Salgado and U.~A.~Wiedemann,
  %``Calculating quenching weights,''
  Phys.\ Rev.\  D {\bf 68} (2003) 014008
  [arXiv:hep-ph/0302184];
  %%CITATION = PHRVA,D68,014008;%%
%\cite{Baier:2001yt}
%\bibitem{Baier:2001yt}
  R.~Baier, Y.~L.~Dokshitzer, A.~H.~Mueller and D.~Schiff,
  %``Quenching of hadron spectra in media,''
  JHEP {\bf 0109}, 033 (2001)
  [arXiv:hep-ph/0106347].
  %%CITATION = JHEPA,0109,033;%%

%\cite{Armesto:2007dt}
\bibitem{Armesto:2007dt}
  N.~Armesto, L.~Cunqueiro, C.~A.~Salgado and W.~C.~Xiang,
  %``Medium-evolved fragmentation functions,''
  arXiv:0710.3073 [hep-ph].
  %%CITATION = ARXIV:0710.3073;%%

\bibitem{Wiedemann:2000za}
  U.~A.~Wiedemann,
  %``Gluon radiation off hard quarks in a nuclear environment: Opacity
  %expansion,''
  Nucl.\ Phys.\  B {\bf 588} (2000) 303
  [arXiv:hep-ph/0005129].
  %%CITATION = NUPHA,B588,303;%

\bibitem{Polosa:2006hb}
  A.~D.~Polosa and C.~A.~Salgado,
  %``Jet shapes in opaque media,''
  Phys.\ Rev.\  C {\bf 75} (2007) 041901
  [arXiv:hep-ph/0607295].
  %%CITATION = PHRVA,C75,041901;%%

\bibitem{:2008cq}
  A.~Adare {\it et al.}  [PHENIX Collaboration],
  %``Dihadron azimuthal correlations in Au+Au collisions at sqrt(s_NN)=200
  %GeV,''
  arXiv:0801.4545 [nucl-ex].
  %%CITATION = ARXIV:0801.4545;%%

\end{thebibliography}

\end{document}
