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arXiv2009

Design considerations for the Micro Vertex Detector of the Compressed Baryonic Matter experiment

The CBM experiment will investigate heavy-ion collisions at beam energies from 8 to 45 AGeV at the future accelerator facility FAIR. The goal of the experiment is to study the QCD phase diagram in the region of moderate temperatures and highest net-baryon densities in search of the first-order phase transition from confined to deconfined matter at the QCD critical point. To do so, CBM aims to measure rare hadronic, leptonic and photonic probes among them open charm. In order to reject the rich background generated by the heavy ion collisions, a micro vertex detector (MVD) providing an unprecedented combination of high rate capability and radiation hardness, very light material budget and excellent granularity is required. In this work, we will present and discuss the concept of this detector.

nucl-ex↗
arXiv2009

Enhanced Direct Photon Production in Au+Au Collisions at 200 GeV in PHENIX

The production of electron pairs with transverse momentum between 1 and 5 GeV/c and m< 300 MeV has been measured at mid-rapidity in 200 GeV p+p and Au+Au collisions by the PHENIX experiment at RHIC. A significant excess above the hadronic background was observed in both p+p and Au+Au collisions. Treating the excess as internal conversion of direct photons, the direct photon yield in Au+Au was found to be enhanced compared to the binary-scaled p+p yield. The enhancement is consistent with an exponential inverse slope of 221 +- 23 +- 18 MeV and predictions from hydrodynamical models with initial temperature between 300 and 600 MeV at formation times of 0.6-0.15 fm/c.

nucl-ex↗
arXiv2009

Recent quarkonia results from the PHENIX experiment

The PHENIX collaboration efforts towards constraining and understanding quarkonia production mechanisms are outlined. J/psi measurements and feed-down sources studies in p-p collisions at 200 GeV, together with their possible indications on the hadro-production mechanisms, are discussed. J/psi photo-production in ultra-peripheral collisions at 200 GeV is also examined. Finally, a glimpse of the first bottomonia results in minimum bias Au-Au collisions at 200 GeV and their implications are presented.

nucl-ex↗
arXiv2009

Initiation of nuclear reactions under laser irradiation of Au nanoparticles in the presence of Thorium aqua-ions

Initiation of nuclear reactions in Thorium nuclei is experimentally studied under laser exposure of Au nanoparticles suspended in the aqueous solution of Th(NO3)4 (232Th). It is found that the reaction pathway depends in which water, either H2O or D2O, the laser exposure is carried out. Saturation of the liquids (H2O or D2O) with gaseous H2 or D2, respectively, enhances the nuclear reactions under laser exposure allowing their excitation at peak intensity as low as 1010 W/cm2. Enhanced gamma-activity of the probe is observed after the end of laser exposure for several hours.

physics.gen-ph↗
arXiv2009

Summary of the J-PARC UCN Taskforce

Discussions in the taskforce meetings in the period of Jan.-Mar. 2009 on the technical possibility of the ultracold neutron (UCN) source at the Japan Proton Accelerator Research Complex (J-PARC) is summarized.

physics.ins-det↗
arXiv2009

pi+Xi- Correlations and the $Ξ^{*}(1530)$ Puzzle

The analysis of the preliminary RHIC data on $π^{+}-Ξ^{-}$ correlation function is carried out.The $Ξ^*(1530)$ resonance is successfully described. The values of the fireball radius and of the $π^{+}-Ξ^{-}$ scattering lengths are obtained.

nucl-th↗
arXiv2009

Theory Support for the Excited Baryon Program at the Jlab 12 GeV Upgrade

This document outlines major directions in theoretical support for the measurement of nucleon resonance transition form factors at the JLab 12 GeV upgrade with the CLAS12 detector. Using single and double meson production, prominent resonances in the mass range up to 2 GeV will be studied in the range of photon virtuality $Q^2$ up to 12 GeV$^2$ where quark degrees of freedom are expected to dominate. High level theoretical analysis of these data will open up opportunities to understand how the interactions of dressed quarks create the ground and excited nucleon states and how these interactions emerge from QCD. The paper reviews the current status and the prospects of QCD based model approaches that relate phenomenological information on transition form factors to the non-perturbative strong interaction mechanisms, that are responsible for resonance formation.

nucl-th↗
arXiv2009

Managing Information for Sparsely Distributed Articles and Readers: The Virtual Journals of the Joint Institute for Nuclear Astrophysics (JINA)

The research area of nuclear astrophysics is characterized by a need for information published in tens of journals in several fields and an extremely dilute distribution of researchers. For these reasons it is difficult for researchers, especially students, to be adequately informed of the relevant published research. For example, the commonly employed journal club is inefficient for a group consisting of a professor and his two students. In an attempt to address this problem, we have developed a virtual journal (VJ), a process for collecting and distributing a weekly compendium of articles of interest to researchers in nuclear astrophysics. Subscribers are notified of each VJ issue using an email-list server or an RSS feed. The VJ data base is searchable by topics assigned by the editors, or by keywords. There are two related VJs: the Virtual Journal of Nuclear Astrophysics (JINA VJ), and the SEGUE Virtual Journal (SEGUE VJ). The JINA VJ also serves as a source of new experimental and theoretical information for the JINA REACLIB reaction rate database. References to review articles and popular level articles provide an introduction to the literature for students. The VJs and support information are available at http://groups.nscl.msu.edu/jina/journals

astro-ph.IM↗
arXiv2011

Ultra-peripheral Au+Au collisions at PHENIX

Ultra-peripheral collisions (UPC) of heavy-ions involve long range electromagnetic interactions at impact parameters twice larger than the nuclear radius, where no nucleon-nucleon collisions occur. The first measurement of photoproduction of $J/ψ$ and of two-photon production of high-mass $e^+ e^-$ pairs in ultra-peripheral nucleus-nucleus interactions will be presented, using Au+Au data at $\sqrt{s_{_{NN}}}$ = 200 GeV. The measured cross sections at midrapidity are consistent with various theoretical predictions.

nucl-ex↗
arXiv2009

$K_s^0 Hadronization Following DIS at CLAS

The hadronization of $K^0$ particles was measured in semi-inclusive deep inelastic scattering (SIDIS) kinematics for several nuclear targets using the CLAS detector. Multiplicity ratios and $Δp_T^2$ values were extracted from the data. These results may be compared with similar values for $π^+$ hadronization from CLAS (at the same kinematics) and $K^+$ hadronization from HERMES (at higher energy transfer). The physics goal of these measurements is to understand the space-time evolution as the struck quark becomes a full-blown hadron as it propagates through nuclear matter.

nucl-ex↗
arXiv2009

Direct Photons at RHIC

A brief overview of direct-photon measurements in p+p and Au+Au collisions at sqrt(s_NN) = 200 GeV with the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is given. Direct-photon yields for pT > 4 GeV/c and photon-hadron azimuthal correlations were determined with the aid of an electromagnetic calorimeter. By detecting e+e- pairs from the internal conversion of virtual photons direct-photon yields were measured between 1 < pT < 4 GeV/c. In Au+Au collisions thermal photons from a quark-gluon plasma (QGP) are expected to contribute significantly to the total direct-photon yield in this range.

nucl-ex↗
arXiv2009

NA49 evidence for the onset of deconfinement

We review the experimental results obtained by the NA49 collaboration in the context of its beam energy scan programme. The data on particle yields and spectral distributions suggest that the deconfinement phase transition is first reached in central collisions of heavy nuclei at about 30A GeV beam energy. Hadron-string transport models as well as the hadron gas model fail to describe the observed energy dependences unless additional parameters or unmeasured states are included.

nucl-ex↗
arXiv2009

Event-by-event Particle Yield Ratio Fluctuations in the CBM and NA49 Experiments

Non-statistical event-by-event fluctuations are considered an important signal for the critical endpoint of the QCD phase diagram. Event-by-event fluctuations of different observables are thus investigated in detail in current experiments. In this contribution, a study of the centrality dependence of event-by-event fluctuations of particle yield ratios by the NA49 experiment in Pb+Pb collisions at 158A GeV beam energy is presented for the first time. An increase of the absolute values of dynamical fluctuations towards lower centralities is observed. The influence of resonance decays will be discussed. Event-by-event fluctuations are an important observable to be studied at the future CBM experiment at FAIR. CBM will investigate the intermediate region of the QCD phase diagram in great detail searching for the first order phase transition line and the expected critical endpoint. It is therefore important to investigate the sensitivity of the CBM detector to particle ratio fluctuations in Au+Au collisions at 10-45 AGeV beam energy. Detailed simulation studies will be presented.

nucl-ex↗
arXiv2009

$ϕ$ Meson As a Probe of QCD Equation of State

In this work, we extract the QCD Equation of State (EoS) using experimental results of the $ϕ$ meson produced in nuclear collisions at AGS, SPS and RHIC energies. The data are confronted to simple thermodynamic expectations and lattice results. The experimental data indicate a first order phase transition, with a mixed phase stretching energy density between $\sim$ 1 and 3.2 GeV/$fm^3$.

hep-ph↗
arXiv2010

Nuclear Reactions

Nuclear reactions generate energy in nuclear reactors, in stars, and are responsible for the existence of all elements heavier than hydrogen in the universe. Nuclear reactions denote reactions between nuclei, and between nuclei and other fundamental particles, such as electrons and photons. A short description of the conservation laws and the definition of basic physical quantities is presented, followed by a more detailed account of specific cases: (a) formation and decay of compound nuclei; (b)direct reactions; (c) photon and electron scattering; (d) heavy ion collisions; (e) formation of a quark-gluon plasma; (f) thermonuclear reactions; (g) and reactions with radioactive beams. Whenever necessary, basic equations are introduced to help understand general properties of these reactions. Published in Wiley Encyclopedia of Physics, ISBN-13: 978-3-527-40691-3 - Wiley-VCH, Berlin, 2009.

nucl-th↗
arXiv2009

Theory and Applications of Coulomb Excitation

Because the interaction is well-known, Coulomb excitation is one of the best tools for the investigation of nuclear properties. In the last 3 decades new reaction theories for Coulomb excitation have been developed such as: (a) relativistic Coulomb excitation, (b) Coulomb excitation at intermediate energies, and (c) multistep coupling in the continuum. These developments are timely with the advent of rare isotope facilities. Of special interest is the Coulomb excitation and dissociation of weakly-bound systems. I review the Coulomb excitation theory, from low to relativistic collision energies. Several applications of the theory to situations of interest in nuclear physics and nuclear astrophysics are discussed.

nucl-th↗