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arXiv2014

Structure of hypernuclei in relativistic approaches

We review the relativistic mean-field approach to various aspects of hypernuclei. It was Brockmann and Weise who first applied this approach to hypernuclei. At that time, it had been already observed experimentally that the spin-orbit splittings in hypernuclei are significantly smaller than that in ordinary nuclei. The relativistic approach was suitable for a discussion of spin-orbit splittings in hypernuclei, as the spin-orbit interaction is naturally emerged with the relativistic framework. Since this seminal work, many developments have been done and the relativistic approach has been applied both to the ground state and to excited states of hypernuclei. We summarize those developments in the Chapter. We shall concentrate on $Λ$-hypernuclei and do not discuss $Σ$ hypernuclei, since the theoretical treatment is rather similar to each other.

nucl-th↗
arXiv2014

Search for a $πΛN-πΣN$ dibaryon in p+p@3.5 GeV

This work is dedicated to the search for a $πΛN\!-\!πΣN$ resonance $\mathcal{Y}$ with the quantum numbers ($Y,I,J^P$) = (1,3/2,$2^+$). The double charged $Σ(1385)N\!-\!Δ(1232)Y$ quasibound state was looked for in the reaction $pp\rightarrow \mathcal{Y}^{++}K^0$ with its unique decay into $Σ^+$ and proton measured with the HADES setup at a kinetic beam energy of 3.5 GeV. The analysis including background determination and a description of the data with a $K^0_S$ Monte Carlo cocktail are presented.

nucl-ex↗
arXiv2014

Charge Symmetry Breaking in the Nucleon and Parity Violating Elastic Electron-Proton Scattering

The basic facts of charge symmetry breaking (CSB) phenomena are reviewed. The relevance of CSB to parity-violating electron-proton scattering experiments that seek to extract strange elastic form factors is discussed. Experimentalists have stated and written that the current uncertainty in our knowledge of CSB limits the ability to push further on the strange form factors. I discuss recent calculations using relativistic chiral perturbation theory and realistic values of strong coupling constants which show that the uncertainties due to lack of knowledge of CSB are at least ten times smaller than present experimental uncertainties. Estimates of CSB effects are made for the JLab Qweak and Mainz P2 experiments.

nucl-th↗
arXiv2014

Results of the material screening program of the NEXT experiment

The 'Neutrino Experiment with a Xenon TPC (NEXT)', intended to investigate neutrinoless double beta decay, requires extremely low background levels. An extensive material screening and selection process to assess the radioactivity of components is underway combining several techniques, including germanium gamma-ray spectrometry performed at the Canfranc Underground Laboratory; recent results of this material screening program are presented here.

physics.ins-det↗
arXiv2014

Light (Hyper-)Nuclei production at the LHC measured with ALICE

The high center-of-mass energies delivered by the LHC during the last three years of operation led to accumulate a significant statistics of light (hyper-)nuclei in pp, p--Pb and Pb--Pb collisions. The ALICE apparatus allows for the detection of these rarely produced particles over a wide momentum range thanks to its excellent vertexing, tracking and particle identification capabilities. The last is based on the specific energy loss in the Time Projection Chamber and the velocity measurement with the Time-Of-Flight detector. The Cherenkov technique, exploited by a small acceptance detector (HMPID), has also been used for the most central Pb--Pb collisions to identify (anti-)deuterons at intermediate transverse momentum.\\ Results on the production of stable nuclei and anti-nuclei in pp, p--Pb and Pb--Pb collisions are presented. Hypernuclei production rates in Pb--Pb are also described, together with a measurement of the hypertriton lifetime. The results are compared with the predictions from thermal and coalescence models. Moreover the results on the search for weakly-decaying light exotic states, such as the $ΛΛ$ (H-dibaryon) and the $Λ$-neutron bound states are discussed.

hep-ex↗
arXiv2014

Differences between Axions and Generic Light Scalars in Laboratory Experiments

It is well-known that electric dipole moment (EDM) constraints provide the most stringent bounds on axion-mediated macroscopic spin-dependent (SD) and time reversal and parity violating (TVPV) forces. These bounds are several orders of magnitude stronger than those arising from direct searches in fifth-force experiments and combining astrophysical bounds on stellar energy loss with Eotvos tests of the weak equivalence principle (WEP). This is a consequence of the specific properties of the axion, invoked to solve the Strong CP problem. However, the situation is quite different for generic light scalars that are unrelated to the strong CP problem. In this case, bounds from fifth-force experiments and astrophysical processes are far more stringent than the EDM bounds, for the mass range explored in direct searches.

hep-ph↗
arXiv2014

136Sn and three body forces

New experimental data on 2+ energies of 136,138Sn confirms the trend of lower 2+ excitation energies of even-even tin isotopes with N > 82 compared to those with N< 82. However, none of the theoretical predictions using both realistic and empirical interactions can reproduce experimental data on excitation energies as well as the transition probabilities (B(E2; 6+ -> 4+)) of these nuclei, simultaneously, apart from one whose matrix elements have been changed empirically to produce mixed seniority states by weakening pairing. We have shown that the experimental result also shows good agreement with the theory in which three body forces have been included in a realistic interaction. The new theoretical results on transition probabilities have been discussed to identify the experimental quantities which will clearly distinguish between different views.

nucl-th↗
arXiv2014

Light-ion production in the interaction of 175 MeV quasi-mono-energetic neutrons with iron and with bismuth

Nuclear data for neutron-induced reactions in the intermediate energy range of 20 to 200 MeV are of great importance for the development of nuclear reaction codes since little data exist in that range. Also several different applications benefit from such data, notably accelerator-driven incineration of nuclear waste. The Medley setup was used for a series of measurements of p, d, t, $^3$He and $α$-particle production by 175 MeV quasi-mono-energetic neutrons on various target nuclei. The measurements were performed at the The Svedberg Laboratory in Uppsala, Sweden. Eight detector telescopes placed at angles between 20$^\circ$ and 160$^\circ$ were used. Medley uses the $ΔE$-$ΔE$-$E$ technique to discriminate among the particle types and is able to measure double-differential cross sections over a wide range of particle energies. This paper briefly describes the experimental setup, summarizes the data analysis and reports on recent changes in the previously reported preliminary data set on bismuth. Experimental data are compared with INCL4.5-Abla07, MCNP6 using CEM03.03, TALYS and PHITS model calculations as well as with nuclear data evaluations. The models agree fairly well overall but in some cases systematic differences are found.

nucl-ex↗
arXiv2014

Feasibility Study of $ϕ$(1020) Production at NICA/MPD

The goal of this article is to give information about the new accelerator complex NICA at JINR, to provide overview of the MultiPurpose Detector (MPD) and its sub-detectors and to present the current results of the MPD performance for $ϕ$-meson production.

physics.ins-det↗
arXiv2014

The Neutron Lifetime

The decay of the free neutron into a proton, electron, and antineutrino is the prototype semileptonic weak decay and the simplest example of nuclear beta decay. The nucleon vector and axial vector weak coupling constants G_V and G_A determine the neutron lifetime as well as the strengths of weak interaction processes involving free neutrons and protons that are important in astrophysics, cosmology, solar physics and neutrino detection. In combination with a neutron decay angular correlation measurement, the neutron lifetime can be used to determine the first element of the CKM matrix Vud. Unfortunately the two main experimental methods for measuring the neutron lifetime currently disagree by almost 4 sigma. I will present a brief review of the status of the neutron lifetime and prospects for the future.

nucl-ex↗
arXiv2014

Searches for Exotic Interactions Using Neutron Spin Rotation

Various theories beyond the Standard Model predict new particles with masses in the sub-eV range with very weak couplings to ordinary matter. I present both measured and projected limits on the strengths of two possible interactions that could be mediated by these new particles, and how one may additionally use these results to search for in matter gravitational torsion.

nucl-ex↗
arXiv2014

Recent progress in the development of large area silica aerogel for use as RICH radiator in the Belle II experiment

We report recent progress in the development of large-area hydrophobic silica aerogels for use as radiators in the aerogel-based ring-imaging Cherenkov (A-RICH) counter to be installed in the forward end cap of the Belle II detector, which is currently being upgraded at the High Energy Accelerator Research Organization (KEK), Japan. The production of approximately 450 aerogel tiles with refractive indices of either 1.045 or 1.055 was completed in May, 2014, and the tiles are now undergoing optical characterization. Installation of the aerogels was tested by installing them into a partial mock-up of the support structure.

physics.ins-det↗
arXiv2017

News on spectra from the NA61/SHINE experiment

NA61/SHINE is a fixed target experiment at the CERN Super-Proton-Synchrotron. The main goals of the experiment are to discover the critical point of strongly interacting matter and study the properties of the onset of deconfinement. In order to reach these goals, a study of hadron production properties is performed in nucleus-nucleus, proton-proton and proton-nucleus interactions as a function of collision energy and size of the colliding nuclei. In this talk, recent results on particle production in p+p interactions, as well as Be+Be and Ar+Sc collisions in the SPS energy range are reviewed. Transverse momentum, transverse mass and rapidity spectra obtained with various analysis methods are presented. Surprises in studies of signatures of onset of deconfinement are discussed. The results are compared with available world data.

hep-ex↗
arXiv2017

Controlling $T_c$ of Iridium films using interfacial proximity effects

High precision calorimetry using superconducting transition edge sensors requires the use of superconducting films with a suitable $T_c$, depending on the application. To advance high-precision macrocalorimetry, we require low-$T_c$ films that are easy to fabricate. A simple and effective way to suppress $T_c$ of superconducting Iridium through the proximity effect is demonstrated by using Ir/Pt bilayers as well as Au/Ir/Au trilayers. While Ir/Au films fabricated by applying heat to the substrate during Ir deposition have been used in the past for superconducting sensors, we present results of $T_c$ suppression on Iridium by deposition at room temperature in Au/Ir/Au trilayers and Ir/Pt bilayers in the range of $\sim$20-100~mK. Measurements of the relative impedance between the Ir/Pt bilayers and Au/Ir/Au trilayers fabricated show factor of $\sim$10 higher values in the Ir/Pt case. These new films could play a key role in the development of scalable superconducting transition edge sensors that require low-$T_c$ films to minimize heat capacity and maximize energy resolution, while keeping high-yield fabrication methods.

physics.ins-det↗
arXiv2017

Fitting and selecting scattering data

The main purpose of scattering experiments is to unveil the underlying structure of the colliding particles and their interaction. Typically one measures scattering observables (cross sections and polarizations) at discrete angles and energies and mutually consistent data may validate or falsify proposed theories or models. However, the accumulation of data from different laboratories while potentially improves the statistical significance it may sometimes generate mutually inconsistent data as a side-effect. Thus, some decision has to be made on what are the maximal amount of data which are mutually compatible. We show elastic $πN $ and $NN$ scattering as prominent examples where this selection is called for. We discuss how it can be done in a self-consistent manner invoking a principle of maximal consensus of the database and with the help of a sufficiently flexible model involving a minimal number of theoretical assumptions. In the NN case this has become possible with a combination of long distance field theoretical constraints at the hadronic level such as pion exchanges and electromagnetic effects and a coarse graining of the unknown interaction over the shortest de Broglie wavelength being probed in the scattering process.

nucl-th↗
arXiv2017

Possibility of shears mechanism due to attractive interaction in the island of $A$ $\sim$ 140 region

The present work identify an island in the values of dimensionless parameter $χ$ as +0.10 $<$ $χ$ $<$ +0.55 outside which no magnetic rotational (MR) bands due to the repulsive interaction would be observed. The semi-classical calculations within the hybrid shears mechanism with the principal axis cranking model (HSPAC) reveal the possibility of the shears band due to the attractive interaction for nuclei in A $\sim$ 140 region. Though the limited information exists in literature, the HSPAC calculation exhibits the dipole bands above the 4389-keV and 4160-keV excited states in $^{145}$Sm and $^{146}$Eu nuclei, respectively, demand their candidature of the attractive shears bands. Other interesting consequence of the HSPAC calculations is the increasing nature of the $B(M1)$ and $B(E2)$ transition strengths with spin unlike the decreasing nature of the transition strengths ($B(M1)$ and $B(E2)$ values) of the MR bands. Thus measurement of the transition probability has been required on urgent basis to validate the strong candidature of such an extreme excitation mechanism in $^{145}$Sm and $^{146}$Eu nuclei.

nucl-th↗
arXiv2017

A unified model for nucleosynthesis of heavy elements in stars

We propose a unified model for the nucleosynthesis of heavy (A > 57) elements in stars. The neutron flux can be set to describe neutron capture in arbitrary neutron flux. Our approach solves the coupled differential equations, that describe the neutron capture and decays of 2696 nuclei, numerically without truncating those to include only either capture or decay as traditionally assumed in weak neutron flux (s process). As a result the synthesis of heavy nuclei always evolves along a wide band in the valley of stable nuclei. The observed abundances in the Solar system are reproduced reasonably already in the simplest version of the model. The model predicts that the nucleosynthesis in weak or modest neutron flux produces elements that are traditionally assumed to result in the high neutron flux of supernovae explosions (r process).

astro-ph.SR↗