Jet Fragmentation in p+Pb Collisions

A measurement of jet fragmentation functions into charged particles in $\sqrt{s_{\mathrm{NN}}}$=5.02TeV p+Pb collisions and pp collisions at $\sqrt{s}$=2.76 TeV is presented. The analysis utilizes 28 nb$^{-1}$ of p+Pb data and 4.0 pb$^{-1}$ of pp data both collected in 2013 by the ATLAS detector at the LHC. The measurement is reported in the center of mass frame in the range $|y^*|<$1.6 as a function of the charged-particle longitudinal momentum fraction and for jets with transverse momentum 45 $ < p_{T} <$ 260 GeV and charged particles with $p_{T}>3.5$ GeV. The $\sqrt{s}$=2.76 TeV pp fragmentation functions were extrapolated to $\sqrt{s}$=5.02 TeV in order to provide a comparison for the p+Pb fragmentation functions. Differences are observed between the fragmentation functions measured in pPb collisions and the extrapolated pp fragmentation functions at high-$z$ which are not statistical in nature.