
\documentclass[11pt]{amsart}
\usepackage{geometry}                % See geometry.pdf to learn the layout options. There are lots.
\geometry{a4paper}                   % ... or a4paper or a5paper or ... 
\usepackage{graphicx}
\usepackage{amssymb}
\usepackage{epstopdf}
\DeclareGraphicsRule{.tif}{png}{.png}{`convert #1 `dirname #1`/`basename #1 .tif`.png}

\title{Particle production and fragmentation studies at H1}
\author{Daniel Traynor, on  behalf of the H1 Collaboration}
%\date{}                                           % Activate to display a given date or no date

\begin{document}
\maketitle



Results from H1 were presented for the average charged track multiplicity and the normalised distribution of the scaled momentum, $\rm xp$, of charged final state hadrons as measured in deep-inelastic $\rm ep$ scattering at high $Q^2$ in the Breit frame of reference~\cite{h1a}. The analysis covers the range of photon virtuality $100 < Q^2 < 20 000 ~\rm GeV^{2}$. The results are compared with $e^+e^-$ annihilation data and with various calculations based on perturbative QCD using different models of the hadronisation process.

The results broadly support the concept of quark fragmentation universality in $ep$ collisions and $e^+e^-$ annihilation. A small multiplicity depletion compared to $e^+e^-$ is observed at low $Q$ which can be attributed to higher order QCD processes occurring as part of the hard interaction in ep scattering but not in $e^+e^-$ annihilation. At high $Q$ a large depletion is also observed. In the low and high $Q$ regions, where the comparison to $e^+e^-$ is poor, the Monte Carlo models are able to provide a better description of the data. The results are compared with NLO QCD calculations as implemented in the CYCLOPS program. All three parameterisations of the fragmentation functions used in this program fail to describe the scaling violations seen in the data. 


Results from a study of mini jets in deep-inelastic electron proton scattering were presented with the 
aim of finding evidence for hadronic activities in excess to those expected from the primary interaction~\cite{h1b}. The analysis is performed separately for the inclusive jet sample, which defines the towards direction, and for a dijet sample where the second jet is required to have an azimuthal angle larger than 140 degrees with respect to the leading jet, which defines the away region.The dijet sample is split into two samples which are enhanced in direct photon and resolved photon processes. The transverse region between the toward and away regions should be sensitive to additional hadronic activity. The results are compared to various QCD based models. The analysis covers the range $5 < Q^2 < 100 ~\rm GeV^{2}$, the leading jet is required to have a $p_{t,jet} > 5~\rm{GeV}$ as are both dijets, the mini jets must have a $p_{t}>3~\rm {GeV}$. 

An overall good description of the data in �the toward region� and �the away region� is given by all models for both the inclusive sample and the dijet sample, which proves that the models are able to describe the primary process. In the transverse region the predictions of the models without Multiple interactions are generally undershooting the data for the inclusive sample and for the dijet sample with resolved photon events. The inclusion of multiple interactions improve the agreement signi�cantly but not completely.


\begin{thebibliography}{99}

\bibitem{h1a} H1 Collab., F.D. Aaron et al., Published in Phys.Lett.B654:148-159,2007.  [arxiv:0706.2456]

\bibitem{h1b} Sakar Osman, H1 Collaboration, presented at DIS 2007, Spring 2007.

\end{thebibliography}



\end{document}  


