The fluctuation-dissipation theorem requires the presence of thermal noise in viscous fluids. The time and length scales of heavy-ion collisions are small enough so that the thermal noise can have a measurable effect on observables. Thermal noise is included in numerical simulations of high-energy lead-lead collisions, increasing average values of the momentum eccentricity and contributing to its event-by-event fluctuations.

We perform a principal component analysis (PCA) of $v_3\left(p_T\right)$ in event-by-event hydrodynamic simulations of Pb+Pb collisions at the Large Hadron Collider (LHC). The PCA procedure identifies two dominant contributions to the two-particle correlation function, which together capture 99.9% of the squared variance. We find that the subleading flow (which is the largest source of flow factorization breaking in hydrodynamics) is predominantly a response to the radial excitations of a third-order eccentricity. We present a systematic study of the hydrodynamic response to these radial excitations in 2+1D viscous hydrodynamics. Finally, we construct a good geometrical predictor for the orientation angle and magnitude of the leading and subleading flows using two Fourier modes of the initial geometry.

We have studied the strangeness-changing antineutrino-induced reactions ${\overline{\nu }}_{l}p\to l^{+}\varphi B$, with $\varphi B=K^{-}p$, ${\overline{K}}^{0}n$, ${\pi }^0\Lambda$, ${\pi }^0{\Sigma }^0$, $\eta \Lambda$, $\eta {\Sigma }^0$, ${\pi }^{+}{\Sigma }^{-}$, ${\pi }^{-}{\Sigma }^{+}$, $K^{+}{\Xi }^{-}$, and $K^0{\Xi }^0$, using a chiral unitary approach. These ten coupled channels are allowed to interact strongly, using a kernel derived from the chiral Lagrangians. This interaction generates two $\Lambda \left(1405\right)$ poles, leading to a clear single peak in the $\pi \Sigma$ invariant mass distributions. At backward scattering angles in the center-of-mass frame, ${\overline{\nu }}_{\mu }p\to {\mu }^{+}{\pi }^0{\Sigma }^0$ is dominated by the $\Lambda \left(1405\right)$ state at around 1420 MeV while the lighter state becomes relevant as the angle decreases, leading to an asymmetric line shape. In addition, there are substantial differences in the shape of $\pi \Sigma$ invariant mass distributions for the three charge channels. If observed, these differences would provide valuable information on a claimed isospin $I=1$, strangeness $S=-1$ baryonic state around 1400 MeV. Integrated cross sections have been obtained for the $\pi \Sigma$ and $\overline{K}N$ channels and the impact of unitarization in the results has been investigated. The number of events with $\Lambda \left(1405\right)$ excitation in ${\overline{\nu }}_{\mu }p$ collisions in the recent antineutrino run at the Main Injector Experiment for $\nu$-A (MINERνA) has also been obtained. We find that this reaction channel is relevant enough to be investigated experimentally and to be taken into account in the simulation models of future experiments with antineutrino beams.

MiniBooNE [A. A. Aguilar-Arevalo et al. (MiniBooNE Collaboration), Phys. Rev. D 83, 052007 (2011)] and MINERvA (B. Eberly et al., arXiv:1406.6415v2 [hep-ex]) charge current ${\pi }^{+}$ production data in the $\Delta$ region are discussed. It is argued that despite the differences in neutrino flux, they measure the same dynamical mechanism of pion production and should be strongly correlated. The correlation is clearly seen in the Monte Carlo simulations done with the NuWro generator but is missing in the data. Both the normalization and the shape of the ratio of measured differential cross sections in pion kinetic energy are different from the Monte Carlo results; in the case of normalization the discrepancy is by a factor of $1.49$.

Measurements of fusion excitation functions of ${}^{58}\mathrm{Ni}+{}^{124}\mathrm{Sn}$ and ${}^{64}\mathrm{Ni}+{}^{124}\mathrm{Sn}$ are extended towards lower energy to cross sections of 1 $\mu \mathrm{b}$ and are compared to detailed coupled-channels calculations. The calculations clearly show the importance of including transfer reactions in a coupled-channels treatment for such heavy systems. This result is different from the conclusion made in a previous article which claimed that the influence of transfer on fusion is not important for fusion reactions of $\mathrm{Ni}+\mathrm{Sn}$. In the energy region studied in this experiment no indication of fusion hindrance has been observed, which is consistent with a systematic study of this behavior.

We study the impact of the nucleon-$\alpha P$-wave resonances on neutrino-pair bremsstrahlung. Because of the noncentral spin-orbit interaction, these resonances lead to an enhanced contribution to the nucleon spin structure factor for temperatures $T\lesssim 4$ MeV. If the $\alpha$-particle fraction is significant and the temperature is in this range, this contribution is competitive with neutron-neutron bremsstrahlung. This may be relevant for neutrino production in core-collapse supernovae or other dense astrophysical environments. Similar enhancements are expected for resonant noncentral nucleon-nucleus interactions.

Background: The available data for $E2$ transition strengths in the region between neutron-deficient hafnium and platinum isotopes are far from complete. More and precise data are needed to enhance the picture of structure evolution in this region and to test state-of-the-art nuclear models. In a simple model, the maximum collectivity is expected at the middle of the major shell. However, for actual nuclei, particularly in heavy-mass regions, which should be highly complex, this picture may no longer be the case, and one should use a more realistic nuclear-structure model. We address this point by studying the spectroscopy of Hf as a representative case.

Purpose: We remeasure the $2_1^{+}$ half-lives of ${}^{172,174,176}\mathrm{Hf}$, for which there is some disagreement in the literature. The main goal is to measure, for the first time, the half-lives of higher-lying states of the rotational band. The new results are compared to a theoretical calculation for absolute transition strengths.

Method: The half-lives were measured using $\gamma \text{−}\gamma$ and conversion-electron-$\gamma$ delayed coincidences with the fast timing method. For the determination of half-lives in the picosecond region, the generalized centroid difference method was applied. For the theoretical calculation of the spectroscopic properties, the interacting boson model is employed, whose Hamiltonian is determined based on microscopic energy-density functional calculations.

Results: The measured $2_1^{+}$ half-lives disagree with results from earlier $\gamma \text{−}\gamma$ fast timing measurements, but are in agreement with data from Coulomb excitation experiments and other methods. Half-lives of the $4_1^{+}$ and $6_1^{+}$ states were measured, as well as a lower limit for the $8_1^{+}$ states.

Conclusions: This work shows the importance of a mass-dependent effective boson charge in the interacting boson model for the description of $E2$ transition rates in chains of nuclei. It encourages further studies of the microscopic origin of this mass dependence. New experimental values on transition rates in nuclei from neighboring isotopic chains could support these studies.

Besides earlier predictions based on both phenomenological models and modern microscopic many-body theories, circumstantial evidence was recently found for a reduced kinetic symmetry energy of isospin-asymmetric nucleonic matter compared to the free Fermi gas model prediction due to the short-range correlation of high-momentum neutron-proton pairs. While keeping the total symmetry energy near the saturation density of nuclear matter consistent with existing experimental constraints, we examine the correspondingly enhanced role of the isospin degree of freedom in heavy-ion collisions at intermediate energies due to the reduced (enhanced) kinetic (potential) symmetry energy. Important observable consequences are investigated.

Background: The proton capture reaction ${}^{13}\mathrm{C}\left(p,\gamma \right){}^{14}\mathrm{N}$ is an important reaction in the CNO cycle during hydrogen burning in stars with mass greater than the mass of the Sun. It also occurs in astrophysical sites such as red giant stars: the asymptotic giant branch (AGB) stars. The low energy astrophysical $S$ factor of this reaction is dominated by a resonance state at an excitation energy of around 8.06 MeV $\left(J^{\pi }=1^{-},T=1\right)$ in ${}^{14}\mathrm{N}$. The other significant contributions come from the low energy tail of the broad resonance with $J^{\pi }=0^{-},T=1$ at an excitation of 8.78 MeV and the direct capture process.

Purpose: Measurements of the low energy astrophysical $S$ factor of the radiative capture reaction ${}^{13}\mathrm{C}\left(p,\gamma \right){}^{14}\mathrm{N}$ reported extrapolated values of $S\left(0\right)$ that differ by about $30\%$. Subsequent $R$-matrix analysis and potential model calculations also yielded significantly different values for $S\left(0\right)$. The present work intends to look into the discrepancy through a detailed $R$-matrix analysis with emphasis on the associated uncertainties.

Method: A systematic reanalysis of the available decay data following the capture to the $J^{\pi }=1^{-},T=1$ resonance state of ${}^{14}\mathrm{N}$ around 8.06 MeV excitation had been performed within the framework of the $R$-matrix method. A simultaneous analysis of the ${}^{13}\mathrm{C}\left(p,p_0\right)$ data, measured over a similar energy range, was carried out with the capture data. The data for the ground state decay of the broad resonance state $\left(J^{\pi }=0^{-},T=1\right)$ around 8.78 MeV excitations was included as well. The external capture model along with the background poles to simulate the internal capture contribution were used to estimate the direct capture contribution. The asymptotic normalization constants (ANCs) for all states were extracted from the capture data. The multichannel, multilevel $R$-matrix code azure2 was used for the calculation.

Results: The values of the astrophysical $S$ factor at zero relative energy, resulting from the present analysis, are found to be consistent within the error bars for the two sets of capture data used. However, it is found from the fits to the elastic scattering data that the position of the $J^{\pi }=1^{-},T=1$ resonance state is uncertain by about 0.6 keV, preferring an excitation energy value of 8.062 MeV. Also the extracted ANC values for the states of ${}^{14}\mathrm{N}$ corroborate the values from the transfer reaction studies. The reaction rates from the present calculation are about $10–15\%$ lower than the values of the NACRE II compilation but compare well with those from NACRE I.

Conclusion: The precise energy of the $J^{\pi }=1^{-},T=1$ resonance level around 8.06 MeV in ${}^{14}\mathrm{N}$ must be determined. Further measurements around and below 100 keV with precision are necessary to reduce the uncertainty in the $S$-factor value at zero relative energy.

The pygmy dipole resonance and photon strength function in stable and unstable Ni and Sn isotopes are calculated within the microscopic self-consistent version of the extended theory of finite Fermi systems, which, in addition to the standard quasiparticle random-phase approximation approach, includes phonon coupling effects. The Skyrme force SLy4 is used. A pygmy dipole resonance in ${}^{72}\mathrm{Ni}$ is predicted at the mean energy of 12.4 MeV exhausting 25.7% of the total energy-weighted sum rule. The microscopically obtained photon $E1$ strength functions are compared with available experimental data and used to calculate nuclear reaction properties. Average radiative widths and radiative neutron capture cross sections have been calculated taking phonon coupling into account as well as uncertainties caused by various microscopic level density models. In all three quantities considered, the contribution of phonon coupling turned out to be significant and is found necessary to explain available experimental data.

We calculate neutrino absorption rates due to charged-current reactions ${\nu }_e+n\to e^{-}+p$ and ${\overline{\nu }}_e+p\to e^{+}+n$ in the outer regions of a newly born neutron star called the neutrino-sphere. To improve on recent work which has shown that nuclear mean fields enhance the ${\nu }_e$ cross section and suppress the ${\overline{\nu }}_e$ cross section, we employ realistic nucleon-nucleon interactions that fit measured scattering phase shifts. Using these interactions we calculate the momentum-, density-, and temperature-dependent nucleon self-energies in the Hartree-Fock approximation. A potential derived from chiral effective field theory and a pseudopotential constructed to reproduce nucleon-nucleon phase shifts at the mean-field level are used to study the equilibrium proton fraction and charged-current rates. We compare our results to earlier calculations obtained using phenomenological mean-field models and to those obtained in the virial expansion valid at low density and high temperature. In the virial regime our results are consistent with previous calculations, and at higher densities relevant for the neutrino-sphere, $\rho \gtrsim {10}^{12}$ ${\mathrm{g}/\mathrm{cm}}^3$, we find the difference between the ${\nu }_e$ and ${\overline{\nu }}_e$ absorption rates to be larger than predicted earlier. Our results may have implications for heavy-element nucleosynthesis in supernovae, and for supernova neutrino detection.

The fragment production in collisions of ${}^{48,50}\mathrm{Ca}+{}^{12}\mathrm{C}$ at 50 MeV/nucleon are simulated via the isospin-dependent quantum molecular dynamics (IQMD) model followed by the gemini code. By changing the diffuseness parameter of neutron density distribution to obtain different neutron skin sizes, the effects of neutron skin thickness $\left({\delta }_{np}\right)$ on projectile-like fragments (PLFs) are investigated. The sensitivity of isoscaling behavior to neutron skin size is studied, from which it is found that the isoscaling parameter $\alpha$ has a linear dependence on ${\delta }_{np}$. A linear dependence between ${\delta }_{np}$ and the mean $N/Z$ [$N \left(Z\right)$ is neutron (proton) number] of the PLF is obtained as well. The results show that thicker neutron skin will lead to smaller isoscaling parameter $\alpha$ and $N/Z$. Therefore, it may be probable to extract information of neutron skin thickness from isoscaling parameter $\alpha$ and $N/Z$.

Background: Fusion between two massive nuclei is a very complex process and is characterized by three stages: (a) capture inside the potential barrier, (b) formation of an equilibrated compound nucleus (CN), and (c) statistical decay of the CN leading to a cold evaporation residue (ER) or fission. The second stage is the least understood of the three and is the most crucial in predicting yield of superheavy elements (SHE) formed in complete fusion reactions.

Purpose: A systematic study of average fusion probability, $\langle P_{\mathrm{CN}}\rangle$, is undertaken to obtain a better understanding of its dependence on various reaction parameters. The study may also help to clearly demarcate onset of non-CN fission (NCNF), which causes fusion probability, $P_{\mathrm{CN}}$, to deviate from unity.

Method: ER excitation functions for 52 reactions leading to CN in the mass region 170–220, which are available in the literature, have been compared with statistical model (SM) calculations. Capture cross sections have been obtained from a coupled-channels code. In the SM, shell corrections in both the level density and the fission barrier have been included. $\langle P_{\mathrm{CN}}\rangle$ for these reactions has been extracted by comparing experimental and theoretical ER excitation functions in the energy range $\sim 5$%–35% above the potential barrier, where known effects of nuclear structure are insignificant.

Results: $\langle P_{\mathrm{CN}}\rangle$ has been shown to vary with entrance channel mass asymmetry, $\eta$ (or charge product, $Z_p{Z}_t)$, as well as with fissility of the CN, ${\chi }_{\mathrm{CN}}$. No parameter has been found to be adequate as a single scaling variable to determine $\langle P_{\mathrm{CN}}\rangle$. Approximate boundaries have been obtained from where $\langle P_{\mathrm{CN}}\rangle$ starts deviating from unity.

Conclusions: This study quite clearly reveals the limits of applicability of the SM in interpreting experimental observables from fusion reactions involving two massive nuclei. Deviation of $\langle P_{\mathrm{CN}}\rangle$ from unity marks the beginning of the domain of dynamical models of fusion. Availability of precise ER cross sections over a wider energy range for many more reactions is desired for accurate determination of $\langle P_{\mathrm{CN}}\rangle$ and more insight into the dynamics of fusion in the heavy mass region.

I provide a unified description of efficiency correction and error estimation for moments of conserved quantities in heavy-ion collisions. Moments and cumulants are expressed in terms of the factorial moments, which can be easily corrected for the efficiency effect. By deriving the covariance between factorial moments, one can obtain the general error formula for the efficiency corrected moments based on the error propagation derived from the Delta theorem. The Skellam-distribution-based Monto Carlo simulation is used to test the Delta theorem and bootstrap error estimation methods. The statistical errors calculated from the two methods can well reflect the statistical fluctuations of the efficiency corrected moments.

We supplement the Heavy Ion Jet Interaction Generator (hijing) code with a collective cascade recipe and updated Martin-Stirling-Thorne-Watt (MSTW2009) parton distribution functions (PDFs) to describe nonsingle diffractive (NSD) $p+p$ and Pb collisions at CERN Large Hadron Collider energies. The collective cascade, developed in the space of an impact parameter, is used to induce nuclear modification of nucleons, that are involved in primary interactions, inside the dense nuclear medium. It is found that the improved hijing (Imhijing) code (that with MSTW2009 PDFs) reproduces rather well the pseudorapidity density, the multiplicity, and the transverse momentum distributions of charged particles within the pseudorapidity interval $|{\eta }_{\mathrm{c}.\mathrm{m}.\mathrm{system}}|<2.4$ in NSD $p+p$ collisions at $\sqrt{s_{\mathrm{NN}}}=0.9$, 2.36, and 7 TeV. The Imhijing with collective cascade calculations is also shown to be a good fit to the pseudorapidity density (in the laboratory system) and transverse momentum $\left(p_T\right)$ dependence of the nuclear modification of charged particles in NSD $p+\mathrm{Pb}$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. The effects of the collective cascade are clearly seen in the target $(3<{\eta }_{\mathrm{lab}}<4)$ and central (within $|{\eta }_{\mathrm{c}.\mathrm{m}.\mathrm{system}}|<0.3$ at $1<p_T<8\mathrm{GeV}/c)$ interaction regions when studying the pseudorapidity density and transverse momentum dependence of the nuclear modification factor of the charged particles, respectively.

Determining the nonperturbative $s\overline{s}$ content of the nucleon has attracted considerable interest and has been the subject of numerous experimental searches. These measurements used a variety of reactions, and place important limits on the vector form factors observed in parity-violating (PV) elastic scattering and the parton distributions determined by deep inelastic scattering (DIS). In spite of this progress, attempts to relate information obtained from elastic and DIS experiments have been sparse. To ameliorate this situation, we develop an interpolating model using light-front wave functions capable of computing both DIS and elastic observables. This framework is used to show that existing knowledge of DIS places significant restrictions on our wave functions. The result is that the predicted effects of nucleon strangeness on elastic observables are much smaller than those tolerated by direct fits to PV elastic scattering data alone. Using our model, we find $-0.024\le {\mu }_s\le 0.035$ and $-0.137\le {\rho }_s^D\le 0.081$ for the strange contributions to the nucleon magnetic moment and charge radius. The model we develop also independently predicts the nucleon's strange spin content $\Delta s$ and scalar density $\langle N\left|\overline{s}s\right|N\rangle$, and for these we find agreement with previous determinations.

We describe the microphysics, phenomenology, and astrophysical implication of a $B$-field induced unpairing effect that may occur in magnetars, if the local $B$ field in the core of a magnetar exceeds a critical value $H_{c2}$. Using the Ginzburg-Landau theory of superconductivity, we derive the $H_{c2}$ field for proton condensate taking into the correction $\left(\le 30\%\right)$ which arises from its coupling to the background neutron condensate. The density dependence of pairing of proton condensate implies that $H_{c2}$ is maximal at the crust-core interface and decreases towards the center of the star. As a consequence, magnetar cores with homogenous constant fields will be partially superconducting for “medium-field” magnetars $({10}^{15}\le B\le 5\times {10}^{16}\text{G})$ whereas “strong-field” magnetars $(B>5\times {10}^{16}\text{G})$ will be void of superconductivity. The neutrino emissivity of a magnetar's core changes in a twofold manner: (i) the $B$-field assisted direct Urca process is enhanced by orders of magnitude, because of the unpairing effect in regions where $B\ge H_{c2}$; (ii) the Cooper-pair breaking processes on protons vanish in these regions and the overall emissivity by the pair-breaking processes is reduced by a factor of only a few.

A systematic study of a momentum quadrupole fluctuation thermometer has been presented for heavy-ion collisions at 35 MeV/nucleon via the isospin-dependent quantum molecular dynamics model accompanied by the statistical decay model GEMINI. It is determined that the fragment momentum fluctuation temperature indeed reflects the average temperature of the excitation source in the fragmentation process and the secondary decay. We find that the divergence between the initial temperature and the final measurement temperature is different for protons, tritons, and ${}^3\mathrm{He}$. The maximum divergence of the temperature is about $20\%$ probed by protons. As an example of using protons as the probe particle, we find that the isospin dependence of the nuclear temperature is consistent between the initial temperature and the final measurement temperature.