High $p_{T}$ inclusive hadron and photon spectra in pp and PbPb collisions

TL;DR

This paper presents measurements of high transverse momentum charged hadron and photon spectra in PbPb collisions at 2.76 TeV, revealing significant suppression of hadrons but no modification of photons, indicating a strongly interacting medium.

Contribution

First measurement of high pT hadron and photon spectra in PbPb collisions at 2.76 TeV with detailed comparison to theoretical models and pp references.

Findings

Charged hadron spectra show strong suppression at high pT.

Isolated photon spectra are consistent with no medium modification.

Results support the formation of a strongly interacting quark-gluon plasma.

Abstract

In this article, we report the inclusive charged hadron and isolated photon spectra at $\sqrt{s_{NN}}=2.76$ TeV PbPb collisions measured with the CMS detector at LHC. Charged particle momentum spectra are compared to a constructed reference measurement of proton-proton collisions at $\sqrt{s}=2.76$ TeV by using a combination of $x_T$ scaling and direct interpolation at fixed $p_{T}$. Photon results are compared to next to leading order calculations at the same center of mass energy. Nuclear modification factors ($R_{AA}$) are calculated to study the properties of the medium. While a large suppression is observed in the charged particle $R_{AA}$ at high transverse momentum, isolated photons show no modifications, revealing that PbPb collisions at $\sqrt{s_{NN}}=2.76$ TeV produce a strongly interacting colored medium.