Generalization of radiative jet energy loss to non-zero magnetic mass

Reliable predictions for jet quenching in ultra-relativistic heavy ion collisions require accurate computation of radiative energy loss. With this goal, an energy loss formalism in a realistic finite size dynamical QCD medium was recently developed. While this formalism assumes zero magnetic mass - in accordance with the one-loop perturbative calculations - different non-perturbative approaches report a non-zero magnetic mass at RHIC and LHC. We here generalize the energy loss to consistently include a possibility for existence of non-zero magnetic screening. We also present how the inclusion of finite magnetic mass changes the energy loss results. Our analysis indicates a fundamental constraint on magnetic to electric mass ratio.Comment: 4 pages, 2 figure

Charged particle elliptic flow in p+p collisions at LHC energies in a transport model PACIAE

The parton and hadron cascade model PACIAE based on PYTHIA was used to investigate the charged particle elliptic flow in minimum bias pp collisions at the LHC energies. The strings were distributed randomly in the transverse ellipsoid of the pp collision system with major axis of $R$ (proton radius) and minor axis of $R(1-\xi)$ before parton rescattering. The charged particle elliptic flow as a function of the random number $\xi$ and transverse momentum $p_T$ were investigated. The calculated $v_2/\epsilon$ as a function of reaction energy increases monotonously with increasing reaction energy up to $\sqrt{s}\sim$7 TeV and then turns to saturation. With the parton-parton cross section enlarges three times in parton rescattering, the rapidity integrated charged particle elliptic flow may reach 0.025 at $p_T \sim$2 GeV/c in the minimum bias pp collisions at $\sqrt{s}$=7 TeV.Comment: 7 pages, 4 figure

Medium-induced emissions of hard gluons

We present a derivation of the medium-induced gluon radiation spectrum beyond the current limitation of soft gluon emission. Making use of the path integral approach to describe the propagation of high-energy particles inside a medium, we study the limiting case of a hard gluon emission. Analytical and numerical results are presented and discussed within the multiple soft scattering approximation. An ansatz interpolating between soft and hard gluon emissions is provided. The Landau-Pomeranchuk-Migdal effect is observed in the expected kinematic region.Comment: 17 pages, 6 figures. Minor corrections, references updated. Accepted by Phys. Lett.

Jet Evolution in the Quark-Gluon Plasma from RHIC to the LHC

The observed suppression of high-$p_\perp$ hadrons allows different explanations. We discuss two possible scenarios: In scenario 1, parton energy loss from scattering in the hot medium is complemented by final state interactions in the resonance matter. Scenario 2 has an enhanced transport parameter $\hat q$ which is fitted to RHIC data. For LHC, the two scenarios lead to very different predictions for the nuclear modification factor of hadrons. In addition, jet reconstruction allows more specific tests of the mechanisms responsible for jet quenching. We calculate the distribution of partons inside a jet and find different results for the two scenarios.Comment: 25 pages, 6 figure

Full jet tomography of high-energy nuclear collisions

Parton energy loss in the hot QCD medium will manifest itself not only in leading hadron spectra but also in reconstructed jet productions in high-energy nucleus-nucleus collisions. In this paper we report on recent theoretical efforts in studying full jet observables in relativistic heavy-ion collisions by discussing the modifications of jet shapes, inclusive jet cross section and the vector boson accompanied jet production in the presence of the QGP-induced jet quenching.Comment: Plenary talk at Hard Probe 2010, October 10-15, 2010, Eilat, Israel. 8 pages, 6 figure

Components of the elliptic flow in Pb-Pb collisions at 2.76 TeV

We calculate the elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV in relativistic viscous hydrodynamics. The recent data of the ALICE Collaboration on the elliptic flow as function of the centrality can be very well described using the hydrodynamic expansion of a fluid with a small shear viscosity eta/s=0.08. The elliptic flow as function of the transverse momentum shows systematic deviations from a hydrodynamic behavior in the small momenta region pt<800MeV. It indicates that a non-negligible contribution of non-thermalized particles from jet fragmentation is present

Proton-proton cross-sections: the interplay between density and radius

We argue that there are two mechanisms responsable for the growth of high energy cross-sections - \sigma_{tot} and \sigma_{el}, say - in pp collisions. One is by the increase of matter \emph{density}, resulting in the black disk saturation. The other is by exclusively radial expansion affecting the periphery of the overlap area. Within this simple model we can reproduce all available data in pp from ISR to LHC. In order to achieve a fast growth in the very high energy cosmic ray energies, we propose a fast black disk saturation followed by the dominance of geometric scaling (GS)

Search for a W ' boson decaying to a muon and a neutrino in pp collisions at √s =7 TeV

This is the Pre-Print version of the Article. The official published version can be accessed from the link below - Copyright @ 2011 ElsevierA new heavy gauge boson, W', decaying to a muon and a neutrino, is searched for in pp collisions at a centre-of-mass of 7 TeV. The data, collected with the CMS detector at the LHC, correspond to an integrated luminosity of 36 inverse picobarns. No significant excess of events above the standard model expectation is found in the transverse mass distribution of the muon-neutrino system. Masses below 1.40 TeV are excluded at the 95% confidence level for a sequential standard-model-like W'. The W' mass lower limit increases to 1.58 TeV when the present analysis is combined with the CMS result for the electron channel.This work is supported by the FMSR (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES (Croatia); RPF (Cyprus); Academy of Sciences and NICPB (Estonia); Academy of Finland, ME, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NKTH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); NRF and WCU (Korea); LAS (Lithuania); CINVESTAV, CONACYT, SEP, and UASLP-FAI (Mexico); PAEC (Pakistan); SCSR (Poland); FCT (Portugal); JINR (Armenia, Belarus, Georgia, Ukraine, Uzbekistan); MST and MAE (Russia); MSTD (Serbia); MICINN and CPAN (Spain); Swiss Funding Agencies (Switzerland); NSC (Taipei); TUBITAK and TAEK (Turkey); STFC (United Kingdom); DOE and NSF (USA)

Search for a standard-model-like Higgs boson with a mass in the range 145 to 1000 GeV at the LHC

Open Access: This article is distributed under the terms of the Creative Commons Attribution License.-- et al.A search for a standard-model-like Higgs boson in the H → WW and H → ZZ decay channels is reported, for Higgs boson masses in the range 145 <mH < 1000 GeV. The search is based upon proton–proton collision data samples corresponding to an integrated luminosity of up to 5.1 fb−1 at √s=7 TeV and up to 5.3 fb−1 at √s=8 TeV , recorded by the CMS experiment at the LHC. The combined upper limits at 95 % confidence level on products of the cross section and branching fractions exclude a standard-model-like Higgs boson in the range 145<mH<710 GeV, thus extending the mass region excluded by CMS from 127–600 GeV up to 710 GeV.European Commission; Federal Ministry of Science, Research and Economy (Austria); National Fund for Scientific Research (Belgium); Research Foundation – Flanders; Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brasil); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Brasil); Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro; Fundação de Amparo à Pesquisa do Estado de São Paulo; Bulgarian Ministry of Education and Science; Centre National de la Recherche Scientifique (France); Commissariat à l'énergie atomique et aux énergies alternatives (France); Ministry of Science and Technology of the People's Republic of China; Chinese Academy of Sciences; National Natural Science Foundation of China; Colciencias (Colombia); Croatian Ministry of Science, Education and Sport; Academy of Finland; Helsinki Institute of Physics; Bundesministerium für Bildung und Forschung (Deutschland); Deutsche Forschungsgemeinschaft; Helmholtz Association; General Secretariat of Research and Technology (Greece); Hungarian Scientific Research Fund; National Office for Research and Technology (Hungary); Department of Atomic Energy (India); Department of Science and Technology (India); Council of Science and Industrial Research (India); Institute for Research in Fundamental Sciences (Iran); Science Foundation Ireland; Istituto Nazionale di Fisica Nucleare (Italia); Korean Ministry of Education, Science and Technology; Lithuanian Academy of Sciences; Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (México); Consejo Nacional de Ciencia y Tecnología (México); Secretaría de Educación Pública (México); Universidad Autónoma de San Luis Potosí; Ministry of Science and Innovation (New Zealand); Ministry of Science and Higher Education and the National Science Centre (Poland); Fundação para a Ciência e a Tecnologia (Portugal); Joint Institute for Nuclear Research (Russia); Russian Academy of Sciences; Russian Foundation for Basic Research; Ministry of Education, Science and Technological Development (Serbia); Ministerio de Ciencia e Innovación (España); Swiss Funding Agencies; Swiss National Science Foundation; National Science Council (Taiwan); The Scientific and Technological Research Council of Turkey; Turkish Atomic Energy Authority; Science and Technology Facilities Council (UK); Department of Energy (US); National Science Foundation (US); A. G. Leventis Foundation; Alfred P. Sloan Foundation; Alexander von Humboldt Foundation; Foundation for Polish Science.Peer Reviewe

Enhanced J/ψ-pair production from double-parton scatterings in nucleus–nucleus collisions at the Large Hadron Collider

AbstractA generic expression of double-parton scattering cross sections in high-energy nucleus–nucleus (A–A) collisions is derived as a function of the corresponding single-parton hard cross sections and of the A–A event centrality. We consider the case of prompt-J/ψ production in lead–lead (Pb–Pb) at the CERN Large Hadron Collider and find that about 20% (35%) of the J/ψ events in minimum-bias (most central) collisions contain a second J/ψ from double-parton interactions. In Pb–Pb at 5.5 TeV, in the absence of final-state effects, about 240 double-J/ψ events are expected per unit midrapidity and per inverse-nanobarn in the dilepton decay modes. The implications of double-J/ψ production on the interpretation of the observed J/ψ suppression in A–A collisions are discussed