In-medium jet shape from energy collimation in parton showers: comparison with CMS PbPb data at 2.76 GeV

Redamy Perez Ramos (1) , Thorsten Renk (1, 2)

1 JYU - University of Jyväskylä
2 HIP - Helsinki Institute of Physics

We present the medium-modified energy collimation and the jet shape in the leading-logarithmic approximation of QCD. As a consequence of more accurate kinematic considerations in the argument of the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) fragmentation functions (FFs) we find a correction of order ${\cal O}(\alpha_s)$ which accounts for the scaling violation of DGLAP FFs at small $x$. We also compare our calculations with the event generator YaJEM. The modification of jets by the medium in both cases is implemented by altering the infra-red sector using the Borghini-Wiedemann model. The energy collimation and jet shapes qualitatively describe a clear broadening of showers in the medium, which is further supported by YaJEM in the final comparison of the jet shape with CMS PbPb data at center of mass energy 2.76 GeV. The comparison of the biased versus unbiased YaJEM jet shape with the CMS data shows a more accurate agreement for biased showers and illustrates the importance of an accurate simulation of the experimental jet-Finding strategy.

Mots clés: QCD jets; collider physics; QGP; fragmentation functions; jet shapes; energy collimation

Domaines: Physique des Hautes Energies - Phénoménologie [hep-ph]

Redamy Perez Ramos, Thorsten Renk. In-medium jet shape from energy collimation in parton showers: comparison with CMS PbPb data at 2.76 GeV. 2014. ⟨hal-00933921v1⟩