Abstract:
Jet production in lead-lead (PbPb) and proton-proton (pp) collisions at a
nucleon-nucleon center-of-mass energy of 5.02TeV is studied with the CMS detector at the
LHC, using PbPb and pp data samples corresponding to integrated luminosities of 404 μb−1
and 27.4 pb−1, respectively. Jets with different areas are reconstructed using the anti-kT
algorithm by varying the distance parameter R. The measurements are performed using
jets with transverse momenta (pT) greater than 200 GeV and in a pseudorapidity range
of | | < 2. To reveal the medium modification of the jet spectra in PbPb collisions, the
properly normalized ratio of spectra from PbPb and pp data is used to extract jet nuclear
modification factors as functions of the PbPb collision centrality, pT and, for the first time,
as a function of R up to 1.0. For the most central collisions, a strong suppression is observed
for high-pT jets reconstructed with all distance parameters, implying that a significant
amount of jet energy is scattered to large angles. The dependence of jet suppression on R
is expected to be sensitive to both the jet energy loss mechanism and the medium response,
and so the data are compared to several modern event generators and analytic calculations.
The models considered do not fully reproduce the data.
