• Volume 75, Issue 2

August 2010,   pages  1-392a

• Foreword

• The canonical and grand canonical models for nuclear multifragmentation

Many observables seen in intermediate energy heavy-ion collisions can be explained on the basis of statistical equilibrium. Calculations based on statistical equilibrium can be implemented in microcanonical ensemble, canonical ensemble or grand canonical ensemble. This paper deals with calculations with canonical and grand canonical ensembles. A recursive relation developed recently allows calculations with arbitrary precision for many nuclear problems. Calculations are done to study the nature of phase transition in nuclear matter.

• Dilepton production in nucleon–nucleon collisions around 1 GeV/nucleon: A theoretical update

We present a fully relativistic and gauge invariant framework for calculating the cross-sections of dilepton production in nucleon–nucleon ($N N$) collisions which is based on the meson-exchange approximation for the $N N$ scattering amplitudes. Predictions of our model are compared with those of other covariant models that have been used to describe this reaction. We discuss the comparison of our calculations with the old DLS and the recent HADES data.

• Vector mesons in strongly interacting matter

Properties of hadrons in strongly interacting matter provide a link between quantum chromodynamics in the strong coupling regime and experimental observables. QCD sum rules show that changes in chiral and higher-order condensates, partially associated with a restoration of chiral symmetry in the nuclear medium, will lead to significant changes in the low-energy spectrum of hadrons. Heavy-ion collisions and reactions with elementary probes have been used to extract experimental information on in-medium properties of hadrons. Results on the light vector mesons $\rho$, $\omega$, and $\phi$, are summarized and compared. Almost all experiments report a softening of the spectral functions with increases in width depending on the density and temperature of the hadronic environment. No evidence for mass shifts is found in majority of the experiments. Remaining inconsistencies among experimental results demonstrate the need for further measurements with higher statistics and inrceased acceptance in particular for low-momentum vector mesons.

• Hypernuclear and strangeness physics program at J-PARC

The inauguration ceremony of the Japan Proton Accelerator Research Complex (J-PARC) was held on 6 July 2009, celebrating the completion of its construction. Now, the beam commissioning of the 50-GeV main proton synchrotron is in progress to improve the beam intensity and quality. Many important experimental programs are planned with the improved beams. In this report, some of them are introduced.

• Multi-reaction-channel fitting calculations in a coupled-channel model: Photoinduced strangeness production

To describe photo- and meson-induced reactions on the nucleon, one is faced with a rather extensive coupled-channel problem. Ignoring the effects of channel coupling, as one would do in describing a certain reaction at the tree level, invariably creates a large inconsistency between the different reactions that are described. In addition, the imaginary parts of the amplitude, which are related through the optical theorem, to total cross-sections, are directly reflected in certain polarization observables. Performing a full coupled-channel calculation thus offers the possibility to implement the maximum number of constraints. The drawback one is faced with is to arrive at a simultaneous fit of a large number of reaction channels. While some of the parameters are common to many reactions, one is still faced with the challenge to optimize a large number of parameters in a highly non-linear calculation. Here we show that such an approach is possible and present some results for photoinduced strangeness production.

• Hadrons and broken symmetries with WASA-at-COSY

The WASA Detector Facility is an internal experiment at the cooler synchrotron (COSY) in Jülich, Germany. The COSY accelerator provides proton and deuteron beams with momenta up to 3.7 GeV/c giving access to hadron physics including the strange quark sector. The physics program with the WASA detector involves hadron dynamics and hadron structure. Key experiments address fundamental symmetries and symmetry violations via the study of rare and not-so-rare meson decays. From the very first production run, results on the Dalitz plot slope parameter in the isospin violating $\eta \rightarrow 3\pi^{0}$ decay have been obtained. The $3\pi^{0}$ final state is also used to study meson production mechanisms. Investigations of other decay modes of the $\eta$-meson address $C$, $P$, and $T$ symmetries and combinations. Higher orders in chiral perturbation theory are probed with the $\eta \rightarrow \pi^{0} \gamma \gamma$ decay. The status and plans for studying hadron structure with Dalitz decays of mesons are presented.

• High energy nuclear collisions: Theory overview

We review some basic concepts of relativistic heavy-ion physics and discuss our understanding of some key results from the experimental program at the relativistic heavy-ion collider (RHIC). We focus in particular on the early time dynamics of nuclear collisions, some result from lattice QCD, hard probes and photons.

• Transport properties of the fluid produced at Relativistic Heavy-Ion Collider

It is by now well known that the relativistic heavy-ion collisions at RHIC, BNL have produced a strongly interacting fluid with remarkable properties, among them the lowest ever observed ratio of the coefficient of shear viscosity to entropy density. Arguments based on ideas from the string theory, in particular the AdS/CFT correspondence, led to the conjecture – now known to be violated – that there is an absolute lower limit $1/4\pi$ on the value of this ratio. Causal viscous hydrodynamics calculations together with the RHIC data have put an upper limit on this ratio, a small multiple of $1/4\pi$, in the relevant temperature regime. Less well-determined is the ratio of the coefficient of bulk viscosity to entropy density. These transport coefficients have also been studied non-perturbatively in the lattice QCD framework, and perturbatively in the limit of high-temperature QCD. Another interesting transport coefficient is the coefficient of diffusion which is also being studied in this context. In this paper some of these recent developments are reviewed and then the opportunities presented by the anticipated LHC data are discussed, for the general nuclear physics audience.

• Nuclear symmetry energy: An experimental overview

The nuclear symmetry energy is a fundamental quantity important for studying the structure of systems as diverse as the atomic nucleus and the neutron star. Considerable efforts are being made to experimentally extract the symmetry energy and its dependence on nuclear density and temperature. In this article, the experimental studies carried out up-to-date and their current status are reviewed.

• Present and future strategies for neutrinoless double beta decay searches

The renewed interest shown in these days towards neutrinoless double beta decay, a lepton number violating process which can take place only if neutrinos are Majorana particles ($\nu = \bar{\nu}$) with a nonvanishing mass, is justified by the fact that the Majorana nature of neutrinos is expected in many theories beyond the Standard Model. We also now know, thanks to the neutrino oscillation experiments, that neutrinos are in fact massive, as expected in these theories and not requested in the Standard Model. Moreover, since neutrino oscillation experiments measure only the absolute value of the difference of the square of the neutrino masses, the discovery of neutrinoless double beta decay would help to disentangle questions that still remain unsolved: what is the absolute mass scale of the neutrinos and which mass hierarchy (normal, inverted or quasi-degenerate) is the correct one?

The scope of this paper is not only to review the present results reached in the field by the different groups and technologies worldwide, but also to illustrate and comment on the (near and long-term) future strategies that experimentalists are trying to pursue to reach the needed sensitivity required to explore the inverted hierarchy neutrino mass scale.

• Structure of nuclear transition matrix elements for neutrinoless double-$\beta$ decay

The structure of nuclear transition matrix elements (NTMEs) required for the study of neutrinoless double-$\beta$ decay within light Majorana neutrino mass mechanism is disassembled in the PHFB model. The NTMEs are calculated using a set of HFB intrinsic wave functions, the reliability of which has been previously established by obtaining an overall agreement between the theoretically calculated spectroscopic properties and the available experimental data. Presently, we study the role of short-range correlations, radial evolution of NTMEs and deformation effects due to quadrupolar correlations. In addition, limits on effective light neutrino mass $\langle m_{\nu} \rangle$ are extracted from the observed limits on half-lives $T_{1/2}^{0\nu}$ of neutrinoless double-$\beta$ decay.

• Signals from dark Universe: DAMA/LIBRA at LNGS

The DAMA/LIBRA set-up (about 250 kg highly radiopure NaI(Tl) sensitive mass) is running at the Gran Sasso National Laboratory of the INFN. The first DAMA/LIBRA results point out the presence of a dark matter particle component in the galactic halo, as well as the former DAMA/NaI set-up; cumulatively the data support such evidence at $8.2\sigma$ CL and satisfy all the peculiarities of the dark matter annual modulation signature.

• Nuclear physics with superconducting cyclotron at Kolkata: Scopes and possibilities

The K500 superconducting cyclotron at the Variable Energy Cyclotron Centre, Kolkata, India is getting ready to deliver its first accelerated ion beam for experiment. At the same time, the nuclear physics programme and related experimental facility development activities are taking shape. A general review of the nuclear physics research opportunities with the superconducting cyclotron and the present status of the development of different detector arrays and other experimental facilities will be presented.

• Hybrid recoil mass analyzer at IUAC – First results using gas-filled mode and future plans

Hybrid recoil mass analyzer (HYRA) is a unique, dual-mode spectrometer designed to carry out nuclear reaction and structure studies in heavy and medium-mass nuclei using gas-filled and vacuum modes, respectively and has the potential to address newer domains in nuclear physics accessible using high energy, heavy-ion beams from superconducting LINAC accelerator (being commissioned) and ECR-based high current injector system (planned) at IUAC. The first stage of HYRA is operational and initial experiments have been carried out using gas-filled mode for the detection of heavy evaporation residues and heavy quasielastic recoils in the direction of primary beam. Excellent primary beam rejection and transmission efficiency (comparable with other gas-filled separators) have been achieved using a smaller focal plane detection system. There are plans to couple HYRA to other detector arrays such as Indian national gamma array (INGA) and $4\pi$ spin spectrometer for ER tagged spectroscopic/spin distribution studies and for focal plane decay measurements.

• Overview of the JYFLTRAP mass measurements and high-precision $Q$-values for weak interaction studies

The JYFLTRAP Penning trap set-up at the University of Jyväskylä, Finland, is a Penning trap facility that has provided high-precision atomic mass values for short-lived nuclides since 2003. Until now, masses of more than 250 short-lived nuclides have been measured. Since JYFLTRAP is coupled to the chemically insensitive IGISOL mass separator, any element can be accessed. So far, a huge mass surface extending from magnesium ($Z = 12$) to lead ($Z = 82$) has been covered.

• The DESIR Facility at SPIRAL2

The DESIR Collaboration proposes the construction of an experimental facility to exploit the low-energy beams from SPIRAL1, SPIRAL2 and S3. The high degree of purity required to push experiments towards the limits of stability will be achieved by the implementation in the SPIRAL2 production building of a high-efficiency RFQ cooler coupled to a high-resolution mass separator. Beams from the low-energy branch of the separator spectrometer S3 and from SPIRAL1 will allow complementary studies of refractory elements produced by means of fusion reactions as well as of light and intense exotic beams, respectively.

• NUSTAR and the status of the R3B project at FAIR

Over the last 15 years, reaction experiments on fixed targets using secondary beams of high energy have developed a potential as exploratory tool to study the properties of nuclei far from stability. NUSTAR (nuclear structure, astrophysics and reactions) is a collaboration of the international nuclear structure and astrophysics community with the aim to further explore this method at the FAIR Facility. Within the FAIR complex, NUSTAR defines a facility where the heart is the super-fragment separator (Super-FRS), which serves three experimental branches: The RING, the LOW- and the HIGH-ENERGY branches.

• A vision for the next decade: Plans for rare isotope beams 2010–2015

We present a short overview of the rare isotope facility at TRIUMF, Canada’s National Laboratory for Particle and Nuclear Physics. Plans for the future are also presented.

• RIKEN radioactive isotope beam factory project – Present status and perspectives

Programs for studying nuclear reactions and structure of exotic nuclei available at the RIKEN radioactive isotope beam factory project are introduced and discussed by demonstrating recent highlights. Special emphasis is given to the present status and future plans of new devices.

• List of participants

• Pramana – Journal of Physics

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November 2019

• Editorial Note on Continuous Article Publication

Posted on July 25, 2019