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Search Results: 1 - 10 of 7505 matches for " Ivan Vitev "
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Open charm tomography of cold and hot nuclear matter
Vitev, Ivan;
Brazilian Journal of Physics , 2007, DOI: 10.1590/S0103-97332007000500015
Abstract: we identify the nuclear effects that modify the cross sections for open heavy flavor production in proton-nucleus and nucleus-nucleus collisions. in p+a reactions, we calculate and resum the coherent nuclear-enhanced power corrections from the final-state parton scattering in the medium. we find that single and double inclusive open charm production can be suppressed as much as the yield of neutral pions from dynamical high-twist shadowing. effects of energy loss in p+a collisions are also investigated. these lead to significantly weaker transverse momentum dependence of the nuclear attenuation and give a sizable contribution to the forward rapidity hadron suppression. in a+a reactions we revisit the question of the measured large heavy flavor quenching at rhic. we derive the collisional broadening of the heavy meson's transverse momentum and the distortion of its intrinsic light cone wave function. the medium-induced dissociation probability of heavy mesons is shown to be sensitive to the opacity of the quark-gluon plasma and the time dependence of its formation and evolution. in contrast to previous results on heavy quark modification, our approach predicts suppression of b-mesons comparable to that of d-mesons at transverse momenta as low as pt ~ 10 gev. it allows for an improved description of the large attenuation of non-photonic electrons in central au+au reactions at rhic. preliminary results in the implementation of collisional and radiative energy loss in a langevin simulation approach to heavy quark diffusion and attenuation are also presented.
Non-Abelian energy loss in cold nuclear matter
Vitev, Ivan
High Energy Physics - Phenomenology , 2007, DOI: 10.1103/PhysRevC.75.064906
Abstract: We use a formal recurrence relation approach to multiple parton scattering to find the complete solution to the problem of medium-induced gluon emission from partons propagating in cold nuclear matter. The differential bremsstrahlung spectrum, where Landau-Pomeranchuk-Migdal destructive interference effects are fully accounted for, is calculated for three different cases: (1) a generalization of the incoherent Bertsch-Gunion solution for asymptotic on-shell jets, (2) initial-state energy loss of incoming jets that undergo hard scattering and (3) final-state energy loss of jets that emerge out of a hard scatter. Our analytic solutions are given as an infinite opacity series, which represents a cluster expansion of the sequential multiple scattering. These new solutions allow, for the first time, direct comparison between initial- and final-state energy loss in cold nuclei. We demonstrate that, contrary to the naive assumption, energy loss in cold nuclear matter can be large. Numerical results to first order in opacity show that, in the limit of large jet energies, initial- and final-state energy losses exhibit different path length dependences, linear versus quadratic, in contrast to earlier findings. In addition, in this asymptotic limit, initial-state energy loss is considerably larger than final-state energy loss. These new results have significant implications for heavy ion phenomenology in both p+A and A+A reactions.
Formation time of hadronic resonances
Vitev Ivan
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20123600018
Abstract: In heavy-ion collisions, formation time of hadrons of high transverse momentum can play a pivotal role in determining the perturbative dynamics of the final-state parton and particle system. We present methods to evaluate the formation times of light hadrons, hadronic resonances, open heavy flavor and quarkonia. Experimental implications of the short formation times of heavy particles are discussed in light of recent RHIC and LHC data.
Multiparton Tomography of Hot and Cold Nuclear Matter
Ivan Vitev
Physics , 2003, DOI: 10.1063/1.1664337
Abstract: Multiple parton interactions in relativistic heavy ion reactions result in transverse momentum diffusion and medium induced non-Abelian energy loss of the hard probes traversing cold and hot nuclear matter. A systematic study of the interplay of nuclear effects on the $p_T \geq 2$ GeV inclusive hadron spectra demonstrates that the competition between nuclear shadowing, multiple scattering and jet quenching leads to distinctly different enhancement/suppression of moderate and high-$p_T$ hadron production in $d+Au$ and $Au+Au$ collisions at RHIC. The associated increase of di-jet acoplanarity, measured via the broadening of the back-to-back di-hadron correlation function, provides an additional experimental tool to test the difference in the dynamical properties of the media created in such reactions.
Initial State Parton Broadening and Energy Loss Probed in d+Au at RHIC
Ivan Vitev
Physics , 2003, DOI: 10.1016/S0370-2693(03)00535-5
Abstract: The impact parameter and rapidity dependence of the Cronin effect for massless pions in $d+Au$ reactions at $\sqrt{s}_{NN}=200$ GeV at RHIC is computed in the framework of pQCD multiple elastic scattering on a nuclear target. We introduce a formalism to incorporate initial state energy loss in perturbative calculations and take into account the elastic energy loss in addition to the transverse momentum broadening of partons.We argue that the centrality dependence of the Cronin effect can distinguish between different hadron production scenarios at RHIC. Its magnitude and rapidity dependence are shown to carry important experimental information about the properties of cold nuclear matter up to the moderate- and large-$x$ antishadowing/EMC regions.
Jet tomography
Ivan Vitev
Physics , 2004, DOI: 10.1088/0954-3899/30/8/019
Abstract: I summarize the recent advances in jet tomographic studies of cold and hot nuclear matter based on perturbative QCD calculations of medium-induced gluon bremsstrahlung. Quantitative applications to ultrarelativistic heavy ion reactions at RHIC indicate the creation of a deconfined state of QCD with initial energy density on the order of 100 times cold nuclear matter density.
Jets in nuclear collisions
Ivan Vitev
Physics , 2004,
Abstract: Ultra-relativistic heavy ion collisions at RHIC and the LHC open exciting new possibilities for jet physics studies in the presence of hot and dense nuclear matter. Recent theoretical advances in understanding the QCD multi-parton dynamics provide a good description of the quenching in the single and double inclusive high-pT hadron spectra. Measurement of the redistribution of the lost energy and the corresponding increase in the soft hadron multiplicities is the next critical step in elucidating the modification of the jet properties in the nuclear environment.
Leading order pQCD hadron production and nuclear modification factors at RHIC and the LHC
Ivan Vitev
Physics , 2002,
Abstract: Hadron production in leading order pQCD is reviewed. The shape of the single inclusive particle spectra is well described for $p_T \geq 2-3$ GeV at center of mass energies from 20 GeV to 2 TeV. The phenomenological K-factor is found to decrease systematically with $\sqrt{s}$. For ultra-relativistic heavy ion reactions the calculation is augmented with the effects of initial multiple parton scattering and final state radiative energy loss. Baseline CERN-LHC predictions for hadron production in $p+p$ and suppression in central $Pb+Pb$ reactions at $\sqrt{s} = 5.5$ TeV are given in comparison to the corresponding results at BNL-RHIC and CERN-SPS energies.
NLO analysis of inclusive jet, tagged jet and di-jet production in Pb+Pb collisions at the LHC
Ivan Vitev
Physics , 2011, DOI: 10.1088/0954-3899/38/12/124087
Abstract: We present results and predictions at next-to-leading order for the recent LHC lead-lead run at a center-of-mass energy of 2.76 TeV per nucleon-nucleon pair. Specifically, we focus on the suppression the single and double inclusive jet cross sections and demonstrate how the di-jet asymmetry, recently measured by ATLAS and CMS, can be extracted from this general result. The case of jets tagged by an electroweak boson is exemplified by the $Z^0$+jet channel. We predict a signature transition from enhancement to suppression of the tagged jet related to the medium-induced modification of the parton shower. Finally, we clarify the relation between the suppression of inclusive jets, tagged jets and di-jets and the quenching of inclusive particles on the example of the recent ALICE charged hadron attenuation data.
Jet quenching at intermediate RHIC energies
Ivan Vitev
Physics , 2004, DOI: 10.1016/j.physletb.2004.12.013
Abstract: The final state energy loss of fast partons penetrating a longitudinally expanding quark-gluon plasma of effective gluon rapidity density $dN^{g}/dy=650-800$ is evaluated and incorporated together with the multiple initial state Cronin scattering in the lowest order perturbative QCD hadron production formalism. Predictions for the neutral pion attenuation in central $Au+Au$ collisions at the intermediate RHIC energy of $\sqrt{s_{NN}}=62$ GeV relative to the binary collision scaled $p+p$ result are given. The quenching is found to be a factor of 2-3 with a moderate transverse momentum dependence and the attenuation of the away-side di-hadron correlation function is estimated to be 3-5 fold.
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