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Ivan Vitev

Publications and source records attributed to Ivan Vitev.

138 records · Page 8Linked to original sources
arXiv2003

Multiparton Tomography of Hot and Cold Nuclear Matter

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.

nucl-th↗
arXiv2003

Initial State Parton Broadening and Energy Loss Probed in d+Au at RHIC

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.

nucl-th↗
arXiv2002

Leading order pQCD hadron production and nuclear modification factors at RHIC and the LHC

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.

hep-ph↗
arXiv2002

High-p_T Tomography of d+Au and Au+Au at SPS, RHIC, and LHC

The interplay of nuclear effects on the p_T > 2 GeV inclusive hadron spectra in d+Au and Au+Au reactions at root(s) = 17, 200, 5500 GeV is compared to leading order perturbative QCD calculations for elementary p+p (p-bar+p) collisions. The competition between nuclear shadowing, Cronin effect, and jet energy loss due to medium-induced gluon radiation is predicted to lead to a striking energy dependence of the nuclear suppression/enhancement pattern in A+A reactions. We show that future d+Au data can used to disentangle the initial and final state effects.

hep-ph↗
arXiv2002

High-p_T Pion Quenching versus anti+Baryon Enhancement in Nucleus-Nucleus Collisions

Jet quenching of quarks and gluons in central A+A collisions suppresses the high-p_T meson production and exposes novel baryon dynamics that we attribute to (gluonic) baryon junctions. This mechanism predicts baryon enhancement in a finite moderate-p_T window that decreases with increasing impact parameter. We also extend recent calculations of the transverse momentum behavior of p/pi^+ and p-bar/pi^- to other baryon species and show that a similar pattern is expected for the K^-/Lambda and K^+/bar{Lambda} ratios. Within the framework of the model constant p-bar/p and bar{Lambda}/Lambda ratios are found in central Au+Au collisions at RHIC energies up to p_T ~= 4 - 5 GeV.

hep-ph↗
arXiv2002

Transverse Expansion and High $p_T$ Azimuthal Asymmetry at RHIC

Rapid 3+1D transverse plus Bjorken collective expansion in $A+A$ collisions at ultra-relativistic energies is shown to reduce substantially the azimuthal asymmetry resulting from jet quenching. While the azimuthal asymmetry in non-central collisions, $v_2(p_T>2 \rm{GeV/c})\sim 0.15$ reported by STAR at RHIC, can be accounted for by spatially anisotropic jet energy loss through a 1+1D expanding gluon plasma with $dN^g/dy\sim 1000$, we show that if rapid transverse collective expansion of the plasma is assumed, then the asymmetry due to jet quenching may be reduced below the observed level. Possible implications of this effect are discussed.

nucl-th↗
arXiv2002

Jet Quenching and the p-bar >= pi- Anomaly at RHIC

PHENIX data on Au+Au at root(s)_= 130 AGeV suggest that p-bar yields may exceed pi- at high p_T > 2 GeV/c. We propose that jet quenching in central collisions suppresses the hard PQCD component of the spectra in central A+A reactions, thereby exposing a novel component of baryon dynamics that we attribute to (gluonic) baryon junctions. We predict that the observed p-bar >= pi- and the p > pi+ anomaly at p_T ~ 2 GeV/c is limited to a finite p_T window that decreases with increasing impact parameter.

nucl-th↗
arXiv2001

The role of jet quenching in the p-bar >= pi- anomaly at RHIC

Preliminary PHENIX data on $Au+Au$ reactions at $\sqrt{s}= 130$ AGeV suggest that $\bar{p}$ yields may exceed $π^-$ at high $p_{\rm T} > 2$ GeV/c. We propose that jet quenching in central collisions suppresses the hard PQCD component of the spectra in central $A+A$ reactions, thereby exposing a novel non-perturbative component of baryon dynamics. We suggest that baryon junctions provide a possible explanation of the anomalous component. We predict that the $\bar{p} \geq π^-$ anomaly is limited to a finite $p_{\rm T}$ window and decreases with increasing impact parameter.

hep-ph↗
arXiv2001

High $p_T$ Azimuthal Asymmetry in Non-central A+A at RHIC

The high $p_{\rm T}>3$ GeV azimuthal asymmetry, $v_2(p_{\rm T})$, in non-central nuclear collisions at RHIC is shown to be a sensitive measure of the initial parton density distribution of the produced quark-gluon plasma. A generalization of the Gyulassy-Levai-Vitev (GLV) non-abelian energy loss formalism including Bjorken 1+1D expansion as well as important kinematic constraints is used.

nucl-th↗
arXiv1999

Jet Quenching in Thin Quark-Gluon Plasmas I: Formalism

The modification and amplification of the gluon angular distribution produced along with hard jets in nuclear collisions is computed. We consider the limit of a thin quark-gluon plasma, where the number of rescatterings of the jet and gluons is small. The focus is on jet quenching associated with the formation of highly off-shell partons in hard scattering events involving nuclei. The interference between the initial hard radiation amplitude, the multiple induced Gunion-Bertsch radiation amplitudes, and gluon rescattering amplitudes leads to an angular distribution that differs considerably from both the standard DGLAP evolution and from the classical limit parton cascading. The cases of a single and double rescattering are considered in detail, and a systematic method to compute all matrix elements for the general case is developed. A simple power law scaling of the angular distribution with increasing number of rescatterings is found and used for estimates of the fractional energy loss as a function of the plasma thickness.

hep-ph↗
arXiv1999

Jet quenching in thin plasmas

We investigate the energy loss of quarks and gluons produced in hard processes resulting from final state rescatterings in a finite quark-gluon plasma. The angular distribution of the soft gluon bremsstrahlung induced by n_s=1 rescatterings in the plasma is computed in the Gyulassy-Wang model. Special focus is on how the interference between the initial hard radiation amplitude, the multiple induced Gunion-Bertsch radiation amplitudes, and gluon rescattering amplitudes modifies the classical parton cascade results.

hep-ph↗