Study of jet quenching using photon-jet events in PbPb collisions at 2.76 TeV with CMS
The first measurement of the transverse momentum ( p T ) imbalance of isolated–photon + jet pairs in relativistic heavy ion collisions is reported. The analysis uses data from PbPb collisions at a centre-of-mass energy of 2.76 TeV per nucleon pair, corresponding to an integrated luminosity of 150 μ b − 1 recorded by the CMS experiment at the LHC in 2011. For events containing an isolated photon with transverse momentum p T > 60 GeV / c and an associated jet with p T > 30 GeV / c , the photon + jet p T imbalance is studied as a function of collision centrality and compared to pp data and pythia calculations at the same centre-of-mass energy. Using the p T of the isolated photon as an estimate of the energy of the scattered parton, this measurement allows an unbiased characterization of the in-medium parton energy loss.

title: Searches for light- and heavy-flavour three-jet resonances in pp collisions at $s = 8$ TeV
abstract: A search for three-jet hadronic resonance production in pp collisions at a centre-of-mass energy of 8 TeV has been conducted by the CMS Collaboration at the LHC with a data sample corresponding to an integrated luminosity of 19.4 fb−119.4 fb−1. The search method is model independent, and events are selected that have high jet multiplicity and large values of jet transverse momenta. The signal models explored assume R-parity-violating supersymmetric gluino pair production and have final states with either only light-flavour jets or both light- and heavy-flavour jets. No significant deviation is found between the selected events and the expected standard model multijet and View the MathML sourcett¯ background. For a gluino decaying into light-flavour jets, a lower limit of 650 GeV on the gluino mass is set at a 95% confidence level, and for a gluino decaying into one heavy- and two light-flavour jets, gluino masses between 200 and 835 GeV are, for the first time, likewise excluded.

title: Probing medium-induced energy loss with direct jet reconstruction in p+p and Cu+Cu collisions at PHENIX
abstract: We present the application of a new jet reconstruction algorithm that uses a Gaussian filter to locate and reconstruct the jet energy to p + p and heavy ion data from the PHENIX detector. This algorithm is combined with a fake jet rejection scheme that provides efficient jet reconstruction with an acceptable fake rate. We show our first results on the measured jet spectra, and on jet–jet angular correlation in p+p and Cu+Cu collisions.

title: Direct jet reconstruction in p + p and Cu + Cu collisions at PHENIX
abstract: Direct jet reconstruction in heavy ion collisions is an important probe for the in-medium parton energy loss and jet–medium interactions and reconstructed jets provide additional constraints to characterize the underlying mechanisms. However, traditional jet reconstruction algorithms operating in the large soft background at RHIC produce fake jets well above the intrinsic production rate of high- p T hard scattering, thus impeding the detection of the low cross section jet signal at RHIC energies. We developed a jet reconstruction algorithm that locates and reconstructs the jet energy using a Gaussian filter. This algorithm is combined with a fake jet rejection scheme that provides efficient jet reconstruction with acceptable fake rate in a background environment up to the central Au + Au collision at s NN = 200 GeV . We present results of its application in p + p and Cu + Cu collisions using data from the PHENIX detector, including jet spectrum up to 60 GeV/ c , nuclear modification factor, and fragmentation function.

title: Jet reconstruction in hadronic collisions by Gaussian filtering
abstract: Author(s): Lai, Yue-Shi; Cole, Brian A |  A new algorithm for jet finding in hadronic collisions is presented. The algorithm, based on a Gaussian filter in $(\eta,\phi)$, is specifically intended for use in heavy ion collisions and/or for detectors with limited acceptance. The performance of the algorithm is compared to two conventional algorithms, a seedless cone algorithm and a $k_\perp$ algorithm, for Pythia simulated di-jet events in $\sqrt{s} = 200 \mathrm{GeV}$ $p + p$ collisions with $4 \mathrm{GeV}/c \le \sqrt{Q^2} \le 16 \mathrm{GeV}/c$. The Gaussian filter is found to perform as well as, and in some instances better than, the conventional algorithms.

title: Direct jet reconstruction in p + p and Cu + Cu at PHENIX
abstract: Author(s): Lai, Y-S; collaboration, FTPHENIX |  The Relativistic Heavy Ion Collider collides heavy nuclei at ultrarelativistic energies, creating a strongly interacting, partonic medium that is opaque to the passage of high energy quarks and gluons. Direct jet reconstruction applied to these collision systems provides a crucial constraint on the mechanism for in-medium parton energy loss and jet-medium interactions. However, traditional jet reconstruction algorithm operating in the large soft background at RHIC give rise to fake jets well above the intrinsic production rate of high-pT partons, impeding the detection of the low cross section jet signal at RHIC energies. We developed a new jet reconstruction algorithm that uses a Gaussian filter to locate and reconstruct the jet energy. This algorithm is combined with a fake jet rejection scheme that provides efficient jet reconstruction with acceptable fake rate in a background environment up to the central Au + Au collision at sqrt(s_NN) = 200 GeV. We present results of its application in p + p and Cu + Cu collisions using data from the PHENIX detector, namely p + p cross section, Cu + Cu jet yields, the Cu + Cu nuclear modification factor, and Cu + Cu jet-jet azimuthal correlation.

title: Evidence of sigma particle in J / psi ---> omega pi pi