Multiplicity and Sphericity dependence of jet peak shape in pp collisions at √s = 5 TeV

Abstract

In the early stages of a proton-proton collision it is possible that two energetic partons collide in a hard scattering process. This results in jets, which are sprays of particles travelling close together in phase space. Studying these jets can give us information about their creation process and their interactions with any coloured medium. One way to study the jets is through two particle correlations. Within these two particle angular correlations the jets give rise to a Gaussian jet peak. To analyse the jets themselves the shape of the jet peak can be examined. The main characteristics are the width and height of the jet peak. These jet peaks have been analysed for different multiplicities, different transverse momenta (pT) of the particles and different sphericities. The sphericity analysis is particularly relevant because the possibility that an effect is caused by a bias introduced by the shape of the collision instead of the formation of a deconfined coloured medium, known as the quark gluon plasma or QGP, needs to be ruled out. It is concluded that the jet peak gets narrower with increasing pT. The width of the jet peak is stable with increasing multiplicity except for particles with the lowest pT, in which case it increases slightly as a function of multiplicity. This applies for the analysed sphericity subsets of 0.0-1.0 (inclusive), 0.0-0.3 (low) and 0.3-0.7 (intermediate). The sphericity subset of 0.7-1.0 (high) showed interesting anomalous behaviour which could not be fitted, meaning no conclusion could be drawn based on this sphericity subset