I give an estimate for the skewness and the kurtosis of the baryon number distribution in two representative models; i.e., models of a hadron resonance gas and relativistic mean-field nuclear matter. I emphasize formal similarity between these two descriptions. The hadron resonance gas leads to a deviation from the Skellam distribution if quantum statistical correlation is taken into account at high baryon density, but this effect is not strong enough to explain fluctuation data seen in the beam-energy scan at RHIC/STAR. In the calculation of mean-field nuclear matter, the density correlation with the vector $\omega$ field rather than the effective mass with the scalar $\sigma$ field renders the kurtosis suppressed at higher baryon density so as to account for the experimentally observed behavior of the kurtosis. Finally, I discuss the difference between the baryon number and the proton number fluctuations from correlation effects in isospin space. The numerical results suggest that such effects are only minor even in the case of complete randomization of isospin.

An excited metastable nuclear state of ${}^{192}\mathrm{Os}$ in a hydrogen-like charge state has been studied for the first time. It was populated in projectile fragmentation of a ${}^{197}\mathrm{Au}$ beam on a ${}^9\mathrm{Be}$ target with the UNILAC-SIS accelerators at GSI. Fragmentation products in the region of interest were passed through the fragment separator and injected into the experimental storage ring (ESR). Cooling of the injected beam particles enabled Schottky mass spectrometry to be performed. Analysis shows the lifetime of the state to be considerably longer than that of the neutral ion $[{\tau }_{\mathrm{neut}}=8.5\left(14\right)\mathrm{s}]$; this change is attributed to hindrance of internal conversion in hydrogen-like ${}^{192}\mathrm{Os}$. Calculations have been performed to estimate the lifetime, and the result has been compared with that measured experimentally. There is good agreement between the expected $[{\tau }_{\mathrm{H}-\mathrm{like}}=13.0\left(24\right)\mathrm{s}]$ and measured lifetimes (${\tau }_{\mathrm{rest}}=15.1_{-1.3}^{+1.5}$ s) from the internal decay of ${}^{192m}\mathrm{Os}$. This provides a test for the reliability of the values obtained from internal conversion coefficient calculations in highly ionized systems and is the first measurement of its kind to be performed using the ESR setup.

The $\beta$ decay of molecular tritium currently provides the highest sensitivity in laboratory-based neutrino mass measurements. The upcoming Karlsruhe Tritium Neutrino (KATRIN) experiment will improve the sensitivity to 0.2 eV, making a percent-level quantitative understanding of molecular effects essential. The modern theoretical calculations available for neutrino mass experiments agree with spectroscopic data. Moreover, when neutrino mass experiments performed in the 1980s with gaseous tritium are reevaluated using these modern calculations, the extracted neutrino mass squared values are consistent with zero instead of being significantly negative. However, the calculated molecular final-state branching ratios are in conflict with dissociation experiments performed in the 1950s. We reexamine the theory of the final-state spectrum of molecular-tritium decay and its effect on the determination of the neutrino mass, with an emphasis on the role of the vibrational- and rotational-state distribution in the ground electronic state. General features can be reproduced quantitatively from considerations of kinematics and zero-point motion. We summarize the status of validation efforts and suggest means for resolving the apparent discrepancy in dissociation rates.

Proton-${}^3\mathrm{H}$ elastic scattering and charge-exchange reaction ${}^3\mathrm{H}(p,n){}^3\mathrm{He}$ in the energy regime above the four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained by using realistic two-nucleon potentials and a two-proton Coulomb force as dynamic input. Differential cross section, proton analyzing power, outgoing neutron polarization, and proton-to-neutron polarization transfer coefficients are calculated between 6 and 30 MeV proton beam energy. Good agreement with the experimental data is found for the differential cross section both in elastic and charge-exchange reactions; the latter shows a complicated energy and angular dependence. The most sizable discrepancies between predictions and data are found for the proton analyzing power and outgoing neutron polarization in the charge-exchange reaction, while the respective proton-to-neutron polarization transfer coefficients are well described by the calculations.

A precision measurement of the ${}^{71}\mathrm{Ga}({}^3\mathrm{He},t){}^{71}\mathrm{Ge}$ charge-exchange reaction was performed. By using a rather complete set of theoretical form factors to describe the cross-section angular distributions over a large angular range, the Gamow-Teller strength distribution up to the effective neutron-separation energy in ${}^{71}\mathrm{Ge}$ was extracted. The data and the analysis constrain the ${}^{71}\mathrm{Ga}({\nu }_e,e^{-})$ solar neutrino rate in a neutrino nonoscillation scenario. For nonoscillating neutrinos we report a solar neutrino capture rate of $122.4\pm 3.4\left(\mathrm{stat}\right)\pm 1.1\left(\mathrm{sys}\right)$ SNU, which is lower than the presently accepted value of $132\pm 18$ SNU, though not in disagreement given the quoted errors.

We investigate the two-particle intensity correlation function of $\Lambda$ in relativistic heavy-ion collisions. We find that the behavior of the $\Lambda \Lambda$ correlation function at small relative momenta is fairly sensitive to the interaction potential and collective flows. By comparing the results of different source functions and potentials, we explore the effect of intrinsic collective motions on the correlation function. We find that the recent STAR data give a strong constraint on the scattering length and effective range of $\Lambda \Lambda$ interaction, as $-1.8{\mathrm{fm}}^{-1}<1/a_0<-0.8{\mathrm{fm}}^{-1}$ and $3.5\mathrm{fm}<r_{\mathrm{eff}}<7\mathrm{fm}$, respectively, if $\Lambda$ samples do not include the feed-down contribution from long-lived particles. We find that the feed-down correction for ${\Sigma }^0$ decay reduces the sensitivity of the correlation function to the detail of the $\Lambda \Lambda$ interaction. As a result, we obtain a weaker constraint, $1/a_0<-0.8 {\mathrm{fm}}^{-1}$. Implication for the signal of existence of $H$-dibaryon is discussed. Comparison with the scattering parameters obtained from the double $\Lambda$ hypernucleus may reveal in-medium effects in the $\Lambda \Lambda$ interaction.

We present state-of-the-art calculations of viscous photon emission from nuclear collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). Fluctuating initial density profiles are evolved with event-by-event viscous hydrodynamics. Momentum spectra of thermal photons radiated by these explosively expanding fireballs and their $p_T$-differential anisotropic flow coefficients $v_n\left(p_T\right)$ are computed, both with and without accounting for viscous corrections to the standard thermal emission rates. Viscous corrections to the rates are found to have a larger effect on the $v_n$ coefficients than the viscous suppression of hydrodynamic flow anisotropies. The benefits of taking the ratio of elliptic to triangular flow, $v_2/v_3$, are discussed, and the space-time regions that contribute dominantly to the photon flow harmonics are identified. The directed flow $v_1$ of thermal photons is predicted for the energies currently available at the RHIC and the LHC.

In most heavy ion collision simulations involving relativistic hydrodynamics, the Cooper-Frye formula is applied to transform the hydrodynamical fields to particles. In this article the so-called negative contributions in the Cooper-Frye formula are studied using a coarse-grained transport approach. The magnitude of negative contributions is investigated as a function of hadron mass, collision energy in the range of $E_{\mathrm{lab}}=5\text{–}160A$ GeV, collision centrality, and the energy density transition criterion defining the hypersurface. The microscopic results are compared to negative contributions expected from hydrodynamical treatment assuming local thermal equilibrium. The main conclusion is that the number of actual microscopic particles flying inward is smaller than the negative contribution one would expect in an equilibrated scenario. The largest impact of negative contributions is found to be on the pion rapidity distribution at midrapidity in central collisions. For this case negative contributions in equilibrium constitute 8–13% of positive contributions, depending on collision energy, but only 0.5–4% in cascade calculation. The dependence on the collision energy itself is found to be nonmonotonous with a maximum at $10–20A$ GeV.

A new critical survey is presented of all half-life, decay-energy, and branching-ratio measurements related to 20 superallowed $0^{+}\to 0^{+}\beta$ decays. Included are 222 individual measurements of comparable precision obtained from 177 published references. Compared with our last review in 2008, we have added results from 24 new publications and eliminated 9 references, the results from which having been superseded by much more precise modern data. We obtain world-average $ft$ values for each of the 18 transitions that have a complete set of data, then apply radiative and isospin-symmetry-breaking corrections to extract “corrected” $\mathcal{F}t$ values. Fourteen of these $\mathcal{F}t$ values now have a precision of order 0.1% or better. In the process of obtaining these results we carefully evaluate the available calculations of the isospin-symmetry-breaking corrections by testing the extent to which they lead to $\mathcal{F}t$ values consistent with conservation of the vector current. Only one set of calculations satisfactorily meets this condition. The resultant average $\mathcal{F}t$ value, when combined with the muon lifetime, yields the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa matrix, $V_{ud}=0.97417\pm 0.00021.$ The unitarity test on the top row of the matrix becomes $|V_{ud}{|}^2+|V_{us}{|}^2+{\left|V_{ub}\right|}^2=0.99978\pm 0.00055$ if the Particle Data Group (PDG) recommended value for $V_{us}$ is used. However, recent lattice QCD calculations, not included yet in the PDG evaluation, have introduced some inconsistency into kaon-decay measurements of $V_{us}$ and $V_{us}/V_{ud}.$ We examine the impact of these new results on the unitarity test and conclude that there is no evidence of any statistically significant violation of unitarity. Finally, from the $\mathcal{F}t$-value data we also set limits on the possible existence of scalar interactions.

We investigate ${}^9\mathrm{Be}+{}^{208}\mathrm{Pb}$ elastic scattering, breakup, and fusion at energies around the Coulomb barrier. The three processes are described simultaneously, with identical conditions of calculations. The ${}^9\mathrm{Be}$ nucleus is defined in an $\alpha +\alpha +n$ three-body model, using the hyperspherical coordinate method. We first analyze spectroscopic properties of ${}^9\mathrm{Be}$ and show that the model provides a fairly good description of the low-lying states. The scattering with ${}^{208}\mathrm{Pb}$ is then studied with the continuum discretized coupled channel method, where the $\alpha +\alpha +n$ continuum is approximated by a discrete number of pseudostates. The use of a three-body model for ${}^9\mathrm{Be}$ improves previous theoretical works, where ${}^9\mathrm{Be}$ is assumed to have a two-body structure (${}^8\mathrm{Be}+n$ or ${}^5\mathrm{He}+\alpha$), although neither ${}^8\mathrm{Be}$ nor ${}^5\mathrm{He}$ are bound. Optical potentials for the $\alpha +{}^{208}\mathrm{Pb}$ and  $n+{}^{208}\mathrm{Pb}$ systems are taken from the literature. We present cross sections at different energies, and we investigate the convergence with respect to the truncation of the $\alpha +\alpha +n$ continuum. In general, good agreement with experiment is obtained, despite no parameter fitting being made. We show that continuum effects increase at low energies, and we confirm that breakup channels enhance the fusion cross sections below the Coulomb barrier.

The deuteron quadrupole moment is calculated using two covariant spectator theory model wave functions obtained from the 2007 high-precision fits to $np$ scattering data. Included in the calculation are a new class of isoscalar $np$ interaction currents automatically generated by the nuclear force model used in these fits. The prediction for model WJC-1, with larger relativistic $P$-state components, is $2.5\%$ smaller than the experimental result, in common with the inability of models prior to 2014 to predict this important quantity. However, model WJC-2, with very small $P$-state components, gives agreement to better than 1%, similar to the results obtained recently from chiral effective field theory predictions to next-to-next-to-next-to-leading order.

Antineutrino spectra following the neutron induced fission of ${}^{235}\mathrm{U},{}^{238}\mathrm{U},{}^{239}\mathrm{Pu}$, and ${}^{241}\mathrm{Pu}$ are calculated using the summation approach. While each system involves the decay of more than 800 fission products, the energy region of the spectra most relevant to neutrino oscillations and the reactor antineutrino anomaly is dominated by fewer than 20 nuclei, for which we provide a priority list to drive new measurements. The very-high-energy portion of the spectrum is mainly due to the decay of just two nuclides, ${}^{92}\mathrm{Rb}$ and ${}^{96}\mathrm{Y}$. The integral of the signal measured by antineutrino experiments is found to have a dependence on the mass and proton numbers of the fissioning system. In addition, we observe that $\sim 70\%$ of the signal originates from the light fission fragment group and about $50\%$ from the decay of odd-$Z,$ odd-$N$ nuclides.

Measurements of the neutron radiative-capture cross section of ${}^{124}\mathrm{Xe}$ have been performed for the first time for neutron energies above 100 keV. In addition, data for the ${}^{124}\mathrm{Xe}\left(n,2n\right){}^{123}\mathrm{Xe}$ reaction cross section have been obtained from threshold to 14.8 MeV to cover the entire energy range of interest, while previous data existed only at around 14 MeV. The results of these measurements provide the basis for an alternative and sensitive diagnostic tool for investigating properties of the inertial confinement fusion plasma in deuterium-tritium (DT) capsules at the National Ignition Facility located at Lawrence Livermore National Laboratory. Here, areal density $\rho R$ (density $\times$ radius) of the fuel, burn asymmetry, and fuel-ablator mix are of special interest. The ${}^{124}\mathrm{Xe}\left(n,\gamma \right){}^{125}\mathrm{Xe}$ reaction probes the down-scattered neutrons, while the ${}^{124}\mathrm{Xe}\left(n,2n\right){}^{123}\mathrm{Xe}$ reaction provides a measure of the 14 MeV direct neutrons.

We present the two- and three-pion-exchange contributions to the nucleon-nucleon interaction which occur at next-to–next-to–next-to–next-to–leading order (${\mathrm{N}}^4\mathrm{LO}$, fifth order) of chiral effective field theory and calculate nucleon-nucleon scattering in peripheral partial waves with $L\ge 3$ by using low-energy constants that were extracted from $\pi N$ analysis at fourth order. While the net three-pion-exchange contribution is moderate, the two-pion exchanges turn out to be sizable and prevailingly repulsive, thus compensating the excessive attraction characteristic for next-to–next-to–leading order and ${\mathrm{N}}^3\mathrm{LO}$. As a result, the ${\mathrm{N}}^4\mathrm{LO}$ predictions for the phase shifts of peripheral partial waves are in very good agreement with the data (with the only exception being the ${}^1{F}_3$ wave). We also discuss the issue of the order-by-order convergence of the chiral expansion for the $NN$ interaction.

Background: Neutron emission is correlated in fission events because, on average, more than one neutron is emitted per fission. Measurements of these correlations, coupled with studies of more inclusive observables such as neutron multiplicity, provide sensitive information about the fission mechanism. Neutron-neutron angular correlations have been studied in both spontaneous fission of ${}^{252}\mathrm{Cf}$ and neutron-induced fission of ${}^{235}\mathrm{U}$. These correlations, until recently incalculable in most available simulations of fission, can now be calculated in event-by-event simulations of fission.

Purpose: Phenomenological studies of fission are of interest both for basic science and for practical applications. Neutron-neutron angular correlations are characteristic of the fissioning isotope and could be used in material identification.

Method: We use our model of complete fission events, freya, to first study the sensitivity of two-neutron angular correlations to the model inputs and then compare to available data. We also compare our simulations to neutron-fragment angular correlations.

Results: We find that the correlations calculated with freya are fairly robust with respect to the input parameters. Any strong deviations in the correlations result in poor agreement with measured inclusive neutron observables such as neutron multiplicity as a function of fragment mass and the neutron multiplicity distribution. The agreement of freya with the present set of correlation data is found to be good.

Conclusions: freya can be used to reliably predict neutron-neutron angular correlations and could then be used to identify materials.

Time reversal invariance violating (TRIV) effects in neutron transmission through a nuclear target are discussed. We demonstrate the existence of a class of experiments that are free from false asymmetries. We discuss the enhancement of TRIV effects for neutron energies corresponding to $p$-wave resonances in the compound nuclear system. We analyze a model experiment and show that such tests can have a discovery potential of ${10}^2–{10}^4$ compared to current limits.

We develop a dynamical coupled-channels model of $K^{-}p$ reactions, aiming at extracting the parameters associated with hyperon resonances and providing the elementary antikaon-nucleon scattering amplitudes that can be used for investigating various phenomena in the strangeness sector such as the production of hypernuclei from kaon-nucleus reactions. The model consists of (a) meson-baryon $\left(MB\right)$ potentials $v_{M^{\prime }{B}^{\prime },MB}$ derived from the phenomenological SU(3) Lagrangian, and (b) vertex interactions ${\Gamma }_{MB,Y^{*}}$ for describing the decays of the bare excited hyperon states $\left(Y^{*}\right)$ into $MB$ states. The model is defined in a channel space spanned by the two-body $\overline{K}N,\pi \Sigma ,\pi \Lambda ,\eta \Lambda$, and $K\Xi$ states and also the three-body $\pi \pi \Lambda$ and $\pi \overline{K}N$ states that have the resonant $\pi {\Sigma }^{*}$ and ${\overline{K}}^{*}N$ components, respectively. The resulting coupled-channels scattering equations satisfy the multichannel unitarity conditions and account for the dynamical effects arising from the off-shell rescattering processes. The model parameters are determined by fitting the available data of the unpolarized and polarized observables of the $K^{-}p\to \overline{K}N,\pi \Sigma ,\pi \Lambda ,\eta \Lambda ,K\Xi$ reactions in the energy region from the threshold to invariant mass $W=2.1$ GeV. Two models with equally good ${\chi }^2$ fits to the data have been constructed. The partial-wave amplitudes obtained from the constructed models are compared with the results from a recent partial-wave analysis by the Kent State University group. We discuss the differences between these three analysis results. Our results at energies near the threshold suggest that the higher partial waves should be treated on the same footing as the $S$ wave if one wants to understand the nature of $\Lambda \left(1405\right)1/2^{-}$ using the data below the $\overline{K}N$ threshold, as will be provided by the J-PARC E31 experiment.

We study the phase diagram of isospin-asymmetrical nuclear matter in the density-temperature plane, allowing for four competing phases of nuclear matter: (i) the unpaired phase; (ii) the translationally and rotationally symmetric, but isospin-asymmetrical BCS condensate; (iii) the current-carrying Larkin-Ovchinnikov-Fulde-Ferrell phase; and (iv) the heterogeneous phase-separated phase. The phase diagram of nuclear matter composed of these phases features two tricritical points, in general, as well as crossovers from the asymmetrical BCS phase to a Bose-Einstein condensate (BEC) of deuterons plus a neutron gas, for both the homogeneous superfluid phase (at high temperatures) and the heterogeneous phase (at low temperatures). The BCS-BEC-type crossover in the condensate occurs as the density is reduced. We analyze in detail some intrinsic properties of these phases, including the Cooper-pair wave function, the coherence length, the occupation numbers of majority and minority nucleonic components, and the dispersion relations of quasiparticle excitations about the ground state. We show by explicit examples that the physics of the individual phases and the transition from weak to strong coupling can be well understood by tracing the behavior of these quantities.

The world data on elastic electron scattering on ${}^3\mathrm{He}$ and ${}^4\mathrm{He}$ is used to determine the Zemach moments ${\langle r\rangle }_{\left(2\right)}$ and ${\langle r^3\rangle }_{\left(2\right)}$. These quantities are required to interpret the Lamb shift and hyperfine splitting data of muonic helium presently being measured at the Paul Scherrer Institute by the CREMA Collaboration. The rms radii are determined as well.

We investigate ultrarelativistic collisions of the ${}^{12}\mathrm{C}$ nucleus with heavy targets and show that harmonic flow measures based on ratios of cumulant moments are particularly suited for study of the intrinsic deformation of the ${}^{12}\mathrm{C}$ wave function. In this way one can probe the expected $\alpha$ clusterization in the ground state, which leads to a large initial triangularity in the shape of the fireball in the transverse plane. We show that the clusterization effect results in very characteristic behavior of the ratios of the cumulant moments as functions of the number of participant nucleons, for both elliptic and triangular deformations. Thus experimental event-by-event studies of harmonic flow in ultrarelativistic light-heavy collisions may offer a new window through which to look at the ground-state structure of light nuclei.