arXiv subjects

Ivan Vitev

Publications and source records attributed to Ivan Vitev.

At least 127 records · Page 7Linked to original sources

arXiv2006

Testing the mechanism of QGP-induced energy loss

We present an analytic model of jet quenching, based on the (D)GLV energy loss formalism, to describe the system size dependence of QGP-induced parton absorption in relativistic heavy ion collisions. Numerical simulations of the transverse momentum dependence of jet quenching are given for central Au+Au and Cu+Cu reactions. Low pT dijet correlations are shown to be sensitive to the reappearance of the lost energy as soft hadrons. At high pT we find that the attenuation of dihadrons is similar to that of single inclusive particles. Comparison to recent data from PHENIX and STAR is given as test of the jet quenching theory.

hep-ph↗

arXiv2006

Nuclear effects on open charm production in p+A reactions

We calculate and resum the nuclear enhanced power corrections from the final state partonic scattering in nuclear matter to open charm production and correlations. In p+A reactions, we find that single and double inclusive D mesons can be suppressed as much as the neutral pions from the dynamical high twist shadowing. Effects of initial state energy loss in p+A collisions are also investigated and may lead to significantly weaker transverse momentum dependence of the nuclear suppression.

hep-ph↗

arXiv2006

Testing the theory of QGP-induced energy loss at RHIC and the LHC

We compare an analytic model of jet quenching, based on the GLV non-Abelian energy loss formalism, to numerical results for the centrality dependent suppression of hadron cross sections in Au+Au and Cu+Cu collisions at RHIC. Simulations of neutral pion quenching versus the size of the colliding nuclear system are presented to high transverse momentum pT. At low and moderate pT, we study the contribution of medium-induced gluon bremsstrahlung to single inclusive hadron production. In Pb+Pb collisions at the LHC, the redistribution of the lost energy is shown to play a critical role in yielding nuclear suppression that does not violate the participant scaling limit.

hep-ph↗

arXiv2006

Recent PQCD calculations of heavy quark production

We summarize the results of a recent study of heavy quark production and attenuation in cold nuclear matter. In p+p collisions, we investigate the relative contribution of partonic sub-processes to $D$ meson production and $D$ meson-triggered inclusive di-hadrons to lowest order in perturbative QCD. While gluon fusion dominates the creation of large angle $D\bar{D}$ pairs, charm on light parton scattering determines the yield of single inclusive $D$ mesons. The distinctly different non-perturbative fragmentation of $c$ quarks into $D$ mesons versus the fragmentation of quarks and gluons into light hadrons results in a strong transverse momentum dependence of anticharm content of the away-side charm-triggered jet. In p+A reactions, we calculate and resum the coherent nuclear-enhanced power corrections from the final-state partonic 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 in the incoherent Bertsch-Gunion limit and may lead to significantly weaker transverse momentum dependence of the nuclear attenuation.

hep-ph↗

arXiv2006

Coherent QCD multiple scattering in proton-nucleus collisions

We argue that high energy proton-nucleus (p+A) collisions provide an excellent laboratory for studying nuclear size enhanced parton multiple scattering where power corrections to the leading twist perturbative QCD factorization approach can be systematically computed. We identify and resum these corrections and calculate the centrality and rapidity dependent nuclear suppression of single and double inclusive hadron production at moderate transverse momenta. We demonstrate that both spectra and dihadron correlations in p+A reactions are sensitive measures of such dynamical nuclear attenuation effects

hep-ph↗

arXiv2005

Large Angle Hadron Correlations from Medium-Induced Gluon Radiation

Final state medium-induced gluon radiation in ultradense nuclear matter is examined and shown to favor large angle emission when compared to vacuum bremsstrahlung due to the suppression of collinear gluons. Perturbative expression for the contribution of its hadronic fragments to the back-to-back particle correlations is derived. It is found that in the limit of large jet energy loss gluon radiation determines the yield and angular distribution of | Delta phi | > Pi/2 di-hadrons to transverse momenta pT2 of the associated particles. Clear transition from enhancement to suppression of the away-side hadron correlations is established at moderate pT2 and its experimentally accessible features are predicted versus the trigger particle momentum pT1.

hep-ph↗

arXiv2005

Large angle hadron correlations from medium-induced gluon radiation

Final state medium-induced gluon radiation in ultradense nuclear matter is shown to favor large angle emission when compared to vacuum bremsstrahlung due to the suppression of collinear gluons. In a simple model of momentum transfers from the medium to the jet+gluon system the phase space distribution of non-Abelian bremsstrahlung is examined to first order in opacity. Perturbative expression for the contribution of the hadronic fragments from medium-induced gluons to the back-to-back particle correlations is derived. It is found that in the limit of large jet energy loss gluon radiation determines the yield and angular distribution of $|Δϕ| \geq \fracπ{2}$ di-hadrons to high transverse momenta $p_{T_2}$ of the associated particles. Clear transition from enhancement to suppression of the away-side di-hadron correlations is established at moderate $p_{T_2}$ and its experimentally accessible features are predicted versus the trigger particle momentum $p_{T_1}$. The measured away-side correlation function is shown to be sensitive to the broad rapidity distribution of di-jets and their vacuum and medium-induced acoplanarity.

hep-ph↗

arXiv2005

Coherent power corrections to structure functions

We calculate and resum a perturbative expansion of nuclear enhanced power corrections to the structure functions measured in deeply inelastic scattering of leptons on a nuclear target. Our results for the Bjorken x-, Q**2- and A-dependence of nuclear shadowing in F2(x,Q**2;A) and the nuclear modifications to FL(x,Q**2;A), obtained in terms of the QCD factorization approach, are consistent with the existing data. We predict the dynamical shadowing from final state interactions in neutrino-nucleus reactions for sea and valence quarks in the structure functions F2(x,Q**2;A) and xF3(x,Q**2;A), respectively. In p+A collisions we calculate the centrality and rapidity dependent nuclear suppression of single and double inclusive hadron production at moderate transverse momenta.

hep-ph↗

arXiv2005

Jet quenching in relativistic heavy ion collisions

Parton propagation in dense nuclear matter results in elastic, inelastic and coherent multiple soft scattering with the in-medium color charges. Such scattering leads to calculable modifications of the hadron production cross section that is evaluated in the framework of the perturbative QCD factorization approach. Final state medium-induced gluon bremsstrahlung is arguably the most efficient way of suppressing large transverse momentum particle production in nucleus-nucleus collisions. The observed hadronic attenuation, known as jet quenching, can be related to the properties of the medium, such as density and temperature, and carries valuable information about the early stages of heavy ion reactions. Non-Abelian energy loss in the quark-gluon plasma can be studied in much greater detail through the modification of the two particle back-to-back correlations. Perturbative calculations give good description of the redistribution of the lost energy in lower transverse momentum particles and predict significant increase of the correlation width of away-side di-hadrons. In contrast, energy loss in cold nuclear matter was found to be small but for large values of Feynman-x is expected to complement the dynamical higher twist shadowing in experimentally observable forward rapidity hadron suppression.

hep-ph↗

arXiv2005

Resummed QCD Power Corrections to Nuclear Shadowing

We calculate and resum a perturbative expansion of nuclear enhanced power corrections to the structure functions measured in deeply inelastic scattering of leptons on a nuclear target. Our results for the Bjorken $x$-, $Q^2$- and $A$-dependence of nuclear shadowing in $F_2^A(x,Q^2)$ and the nuclear modifications to $F_L^A(x,Q^2)$, obtained in terms of the QCD factorization approach, are consistent with the existing data. We demonstrate that the low-$Q^2$ behavior of these data and the measured large longitudinal structure function point to a critical role for the power corrections when compared to other theoretical approaches.

hep-ph↗

arXiv2004

Probing the phases of QCD in ultra-relativistic nuclear collisions

The status of RHIC theory and phenomenology is reviewed with an emphasis on the indications for the creation of a new deconfined state of matter. The critical role of high energy nuclear physics in the development of theoretical tools that address various aspects of the QCD many body dynamics is highlighted. The perspectives for studying nuclear matter under even more extreme conditions at the LHC and the overlap with high energy physics is discussed.

hep-ph↗

arXiv2004

Jet quenching at intermediate RHIC energies

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.

nucl-th↗

arXiv2004

Coherent multiple scattering and dihadron correlations in heavy ion collisions

We present a systematic calculation of the coherent multiple parton scattering with several nucleons in lepton-nucleus and hadron-nucleus collisions. We show that in l+A reactions coherence leads to nuclear shadowing in the structure functions and a modification of the QCD sum rules. In p+A reactions we evaluate the nuclear suppression of single and double inclusive hadron production at moderate transverse momenta. We demonstrate that both spectra and dihadron correlations in p+A collisions at RHIC are sensitive measures of such dynamical nuclear attenuation effects.

hep-ph↗

arXiv2004

Jets in nuclear collisions

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.

hep-ph↗

arXiv2004

The perturbative QCD factorization approach in high energy nuclear collisions

I discuss the systematic modifications to the perturbative QCD factorization approach in high energy l+A, p+A and A+A reactions. These include transverse momentum diffusion manifest in the Cronin effect and a small increase in the dijet acoplanarity; nuclear size enhanced power corrections that lead to shadowing in deeply inelastic scattering and suppression of single and double inclusive hadron production at forward rapidity at RHIC but disappear as a function of the transverse momentum; inelastic attenuation of the jet cross sections or jet quenching that persists to much higher pT.

hep-ph↗

arXiv2004

Jet tomography

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.

hep-ph↗

arXiv2004

Nuclear shadowing in neutrino-nucleus deeply inelastic scattering

In the framework of the collinear factorized pQCD approach we calculate the small-$x_B$ process-dependent nuclear modification to the structure functions measured in neutrino-nucleus deeply inelastic scattering. We include both heavy quark mass corrections $(M^2/Q^2)$ and resummed nuclear-enhanced dynamical power corrections in the quantity $(ξ^2/Q^2)(A^{1/3}-1)$ with $ξ^2$ evaluated to leading order in $α_s$. Our formalism predicts a measurable difference in the shadowing pattern of the structure functions $F_2^A(x_B,Q^2)$ and $F_3^A(x_B,Q^2)$ and a significant low- and moderate-$Q^2$ modification of the QCD sum rules. We also comment on the relevance of our results to the NuTeV extraction of $\sin^2θ_W$.

hep-ph↗

arXiv2003

Transverse momentum diffusion and broadening of the back-to-back di-hadron correlation function

We extend the Gyulassy-Levai-Vitev reaction operator approach to multiple elastic scattering of fast partons traversing dense nuclear matter to take into account the leading power corrections due to the medium recoil and to derive the change in the partons' longitudinal momentum.We employ a boost-invariant formalism to generalize previous treatments of the problem, which were specific to the target rest frame. We apply the transverse momentum diffusion results in a simple analytic model to evaluate the broadening of the back-to-back di-hadron correlation function in $d+Au$ reactions.

nucl-th↗