Measurement of charged jet cross sections and jet shapes in proton-proton collisions at sqrt(s) = 2.76 TeV with the ALICE detector at LHC

We present measurements of charged jet cross sections and jet shape observables in leading jet in proton-proton (pp) collisions at sqrt(s) = 2.76 TeV with the ALICE detector at LHC. Jets are reconstructed at the midrapidity from charged particle using sequential recombination anti-kT jet finding algorithm for various R values. The results are compared to measurements from HERWIG, PHOJET and different tunes of PYTHIA6 and earlier measurements at 7 TeV.Comment: Proceedings of XXII DAE-BRNS High Energy Physics Symposium 2016 conference, 12-16 December, 201

Charge Particle Angular Correlations from Leading Photons at RHIC

We report on the observation of jet-like azimuthal and pseudorapidity correlations between the highest $p_T$ photon (leading photon) and charged hadrons produced in both p+p and Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV.Comment: 4 pages, 3 figures. Talk given at Quark Matter 2002 (QM 2002), Nantes, Bretagne, France, 18-24 Jul 200

The Sources of b-Quarks at the Tevatron and their Correlations

The leading-log order QCD hard scattering Monte-Carlo models of HERWIG, ISAJET, and PYTHIA are used to study the sources of b-quarks at the Tevatron. The reactions responsible for producing b and bbar quarks are separated into three categories; flavor creation, flavor excitation, and parton-shower/fragmentation. Flavor creation corresponds to the production of a b-bbar pair by gluon fusion or by annihilation of light quarks, while flavor excitation corresponds to a b or bbar quark being knocked out of the initial-state by a gluon or a light quark or antiquark. The third source occurs when a b-bbar pair is produced within a parton shower or during the fragmentation process of a gluon or a light quark or antiquark (includes gluon splitting). The QCD Monte-Carlo models indicate that all three sources of b-quarks are important at the Tevatron and when combined they qualitatively describe the inclusive cross-section data. Correlations between the b and bbar quark are very different for the three sources and can be used to isolate the individual contributions.Comment: RevTex4, 14 pages, 20 figures, submitted to Phys. Rev.

Supersymmetry versus black holes at the LHC

Supersymmetry and extra dimensions are the two most promising candidates for new physics at the TeV scale. Supersymmetric particles or extra-dimensional effects could soon be observed at the Large Hadron Collider. We propose a simple but powerful method to discriminate the two models: the analysis of isolated leptons with high transverse momentum. Black hole events are simulated with the CATFISH black hole generator. Supersymmetry simulations use a combination of PYTHIA and ISAJET, the latter providing the mass spectrum. Our results show the measure of the dilepton invariant mass provides a strong signature to differentiate supersymmetry and black hole events at the Large Hadron Collider. Analysis of event-shape variables and multilepton events complement and strengthen this conclusion.Comment: 12 pages, 5 figure

Single Production of Fourth Family Sneutrino via RPV Couplings at Linear Colliders

The single production of fourth family sneutrino $\tilde{\nu}_{4}$ via R-parity violating interactions in electron-positron collisions has been investigated. We study the decays of $\tilde{\nu}_{4}$ into different flavor dilepton $e^{\pm}\mu^{\mp}$ via R-parity violation. It is shown that R-parity violating couplings $(\lambda_{411},\lambda_{412})$ down to 0.001 will be reachable at future linear colliders which would provide better accuracy comparing to the indirect measurements as complementary to the LHC results.Comment: 11 pages, 6 figure

Higgs Boson Discovery Potential of LHC in the Channel pp→γγ+jetpp \to\gamma\gamma+jet

We discuss the SM Higgs discovery potential of LHC in the reaction $pp\to H+ jet\to\gamma\gamma+jet$ when the jet is observed at sufficiently high $E_t$ to be reliably identified. We conclude that this channel gives promising discovery possibilities for the Higgs boson mass range 100-140 GeV, during LHC operation at a low luminosity. With 30 fb$^{-1}$ of accumulated data and for $M_H=120$ GeV about 100 signal events could be observed with the number of background events larger by a factor of 2 only, showing a signal significance $S/\sqrt{B}\sim 7$. We use the difference of distributions in the partonic subprocess energy $\sqrt{\hat s}$ for the signal and background for a better separation of the signal.Comment: 15 pages including 6 figures, LaTeX, use epsfig.sty. To appear in Phys.Lett.B. In this replacement minor LaTeX improvements are mad

Photon-tagged jet measurements in Pb+Pb collisions with the CMS detector

Presented are the results of a detailed study for a complete simulation of the CMS detectors at the LHC in view of the expected modification of jet fragmentation functions in central Pb+Pb collisions at (s_NN)**0.5=5.5 TeV compared to the vacuum (p+p) case. The study is based on photon-jet events, using the correlation between isolated high-transverse energy (E_T>70 GeV) photons and fully reconstructed jets, based on the information provided by the CMS calorimeters and silicon tracker.Comment: 4 pages, 4 figures, ontribution to QM'08 conferenc

A New Approach to Nuclear Collisions at RHIC Energies

We present a new parton model approach for nuclear collisions at RHIC energies (and beyond). It is a selfconsistent treatment, using the same formalism for calculating cross sections like the total and the inelastic one and, on the other hand, particle production. Actually, the latter one is based on an expression for the total cross section, expanded in terms of cut Feynman diagrams. Dominant diagrams are assumed to be composed of parton ladders between any pair of nucleons, with ordered virtualities from both ends of the ladder.Comment: 8 pages, 3 figures (proceedings Quark Matter 99

Langevin dynamics of heavy flavors in relativistic heavy-ion collisions

We study the stochastic dynamics of c and b quarks, produced in hard initial processes, in the hot medium created after the collision of two relativistic heavy ions. This is done through the numerical solution of the relativistic Langevin equation. The latter requires the knowledge of the friction and diffusion coefficients, whose microscopic evaluation is performed treating separately the contribution of soft and hard collisions. The evolution of the background medium is described by ideal/viscous hydrodynamics. Below the critical temperature the heavy quarks are converted into hadrons, whose semileptonic decays provide single-electron spectra to be compared with the current experimental data measured at RHIC. We focus on the nuclear modification factor R_AA and on the elliptic-flow coefficient v_2, getting, for sufficiently large p_T, a reasonable agreement.Comment: Talk given at the workshop "Jets in Proton-Proton and Heavy-Ion Collisions", Prague, 12th-14th August 201

First Direct Measurement of Jets in sNN=200\sqrt{s_{NN}}=200 GeV Heavy Ion Collisions by STAR

We present the first measurement of reconstructed jets in ultra-relativistic heavy ion collisions. Utilizing the large coverage of the STAR Time Projection Chamber and Electromagnetic Calorimeter, we apply several modern jet reconstruction algorithms and background subtraction techniques and explore their systematic uncertainties in heavy ion events. The differential spectrum for inclusive jet production in central Au+Au collisions at $\sqrt {s_{NN}}= 200$ GeV is presented. In order to assess the jet reconstruction biases, this spectrum is compared with the jet cross section measured in $\sqrt{s}=200$ GeV p+p collisions scaled by the number of binary N-N collisions to account for nuclear geometric effects.Comment: Proceedings of the 3rd International Conference on Hard and Electro- Magnetic Probes of High-Energy Nuclear Collisions 8-14 June 2008, Illa da Toxa (Galicia-Spain