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S. Y. Panitkin

Publications and source records attributed to S. Y. Panitkin.

14 recordsLinked to original sources
arXiv2002

Longitudinal Flow of Protons from 2-8 AGeV Central Au+Au Collisions

Rapidity distributions of protons from central $^{197}$Au + $^{197}$Au collisions measured by the E895 Collaboration in the energy range from 2 to 8 AGeV at the Brookhaven AGS are presented. Longitudinal flow parameters derived using a thermal model including collective longitudinal expansion are extracted from these distributions. The results show an approximately linear increase in the longitudinal flow velocity, $<βγ>_{L}$, as a function of the logarithm of beam energy.

nucl-ex↗
arXiv2001

Transverse Momentum Dependence of Intercept Parameter λof Two-Pion (-Kaon) Correlation Functions in q-Bose Gas Model

Within recently proposed approach aimed to effectively describe the observed non-Bose type behavior of the intercept λof two-particle correlation function C(p,K) of identical pions or kaons detected in heavy-ion collisions, the q-deformed oscillators and q-Bose gas picture are employed. For the intercept λ, connected with deformation parameter q, the model predicts a fully specified dependence of λon pair mean momentum {\bf K}. The intercepts λ_πand λ_K for pions and kaons, differing noticeably at small {\bf K}, should merge at {\bf K} large enough, i.e., in the range |{\bf K}| \ge 800 MeV/c, where the effect of resonance decays is negligible. In this paper we confront, fixing q appropriately, the predicted dependence λ_π=λ_π({\bf K}) with recent results from STAR/RHIC for π^-π^- and π^+π^+ pairs, and find nice agreement. Using the same q, we also predict behavior of λfor kaons.

hep-ph↗
arXiv2001

Laying the groundwork at the AGS: Recent results from experiment E895

The E895 Collaboration at the Brookhaven AGS has performed a systematic investigation of Au+Au collisions at 2-8 AGeV, using a large-acceptance Time Projection Chamber. In addition to extensive measurements of particle flow, spectra, two-particle interferometry, and strangeness production, we have performed novel hybrid analyses, including azimuthally-sensitive pion HBT, extraction of the six-dimensional pion phasespace density, and a first measurement of the Lambda-proton correlation function.

nucl-ex↗
arXiv2001

Anti-flow of K$^0_s$ Mesons in 6 AGeV Au + Au Collisions

We have measured the sideward flow of neutral strange ($K^0_s$) mesons in 6 AGeV Au + Au collisions. A prominent anti-flow signal is observed for an impact parameter range (b $\lesssim 7$ fm) which spans central and mid-central events. Since the $K^0_s$ scattering cross section is relatively small in nuclear matter, this observation suggests that the in-medium kaon vector potential plays an important role in high density nuclear matter.

nucl-ex↗
arXiv2001

Directed Flow of $Λ$-Hyperons in 2-6 AGeV Au+Au Collisions

Directed flow measurements for $Λ$-hyperons are presented and compared to those for protons produced in the same Au+Au collisions (2, 4, and 6 AGeV; $b < 5 - 6$ fm). The measurements indicate that $Λ$-hyperons flow consistently in the same direction and with smaller magnitudes than those of protons. Such a strong positive flow [for $Λ$s] has been predicted in calculations which include the influence of the $Λ$-nucleon potential. The experimental flow ratio $Λ$/p is in qualitative agreement with expectations ($\sim 2/3$) from the quark counting rule at 2 AGeV but is found to decrease with increasing beam energy.

nucl-ex↗
arXiv2000

Azimuthal Dependence of Pion Interferometry at the AGS

Two-pion correlation functions, measured as a function of azimuthal emission angle with respect to the reaction plane, provide novel information on the anisotropic shape and orientation of the pion-emitting zone formed in heavy ion collisions. We present the first experimental determination of this information, for semi-central Au+Au collisions at 2-6 AGeV. The source extension perpendicular to the reaction plane is greater than the extension in the plane, and tilt of the pion source in coordinate space is found to be opposite its tilt in momentum space.

nucl-ex↗
arXiv2000

Pion Imaging at the AGS

Source imaging analysis was performed on two-pion correlations in central Au + Au collisions at beam energies between 2 and 8$A$ GeV. We apply the imaging technique by Brown and Danielewicz, which allows a model-independent extraction of source functions with useful accuracy out to relative pion separations of about 20 fm. We found that extracted source functions have Gaussian shapes. Values of source functions at zero separation are almost constant across the energy range under study. Imaging results are found to be consistent with conventional source parameters obtained from a multidimensional HBT analysis.

nucl-ex↗
arXiv2000

Sideward Flow in Au + Au Collisions Between 2A GeV and 8A GeV

Using the large acceptance Time Projection Chamber of experiment E895 at Brookhaven, measurements of collective sideward flow in Au + Au collisions at beam energies of 2, 4, 6 and 8A GeV are presented in the form of in-plane transverse momentum and the first Fourier coefficient of azimuthal anisotropy v_1. These measurements indicate a smooth variation of sideward flow as a function of beam energy. The data are compared with four nuclear transport models which have an orientation towards this energy range. All four exhibit some qualitative trends similar to those found in the data, although none shows a consistent pattern of agreement within experimental uncertainties.

nucl-ex↗
arXiv1999

Probing Baryon Freeze-out Density at the AGS with Proton Correlations

First measurements of the beam energy dependence of the two proton correlation function in central Au+Au collisions are performed by the E895 Collaboration at the BNL AGS. The imaging technique of Brown-Danielewicz is used in order to extract information about the proton source at freeze-out. Measured correlation functions and sources do not exhibit significant changes with beam energy.

nucl-ex↗
arXiv1999

Imaging proton sources and space-momentum correlations

The reliable extraction of information from two-proton correlation functions is a long-standing problem in two-particle interferometry. Recently introduced imaging techniques give one the ability to reconstruct source functions from the correlation data in a model independent way. We explore the applicability of two-proton imaging to realistic sources with transverse space-momentum correlations. We find that the proton images are very sensitive to these correlations. We show that one can reliably reconstruct the source functions from the two-proton correlation functions, regardless of the degree of the space-momentum correlations.

nucl-th↗
arXiv1999

Proton and deuteron distributions as signatures for collective particle dynamics and event shape geometries at the RHIC

We present predictions for the formation of (anti)nuclear bound states in nucleus-nucleus reactions at RHIC energies. he phase space coalescence method is used in combination with RQMD-v2.4 transport calculations to demonstrate the relevance of particle production as well as the longitudinal and transverse flow components. The formation of deuterons follows an approximate scaling law proportional to the relative freeze-out densities of nucleons and produced secondaries. For antideuterons, an additional suppression appears that is proportional to the number of nucleons, pointing toward multiple rescattering and absorption prior to freeze-out.

nucl-th↗
arXiv1999

Beam energy dependence of two-proton correlations at the AGS

First measurements of the beam energy dependence of the two proton correlation function in central Au+Au collisions are performed by the E895 Collaboration at the BNL AGS. No significant changes with beam energy were observed. The imaging technique of Brown-Danielewicz is used in order to extract information about the space-time content of the proton source at freeze-out. Extracted source functions show peculiar enhancement at low relative separation.

nucl-ex↗
arXiv1999

Deuteron production and space-momentum correlations at RHIC

We present predictions for the formation of (anti)nuclear bound states in Au+Au central collisions at $\sqrt{s}=200A$ GeV. The coalescence afterburner was applied to the freeze-out phase space distributions of nucleons provided by the transport model, RQMD version 2.4. We study the sensitivity of the deuteron spectra to space-momentum correlations. It is found that the deuteron transverse momentum distributions are strongly affected by the nucleon space-momentum correlations.

nucl-th↗