We consider fermion-dimer scattering in the presence of a large positive scattering length in the frame of functional renormalization group equations. A flow equation for the momentum dependent fermion-dimer scattering amplitude is derived from first principles in a systematic vertex expansion of the exact flow equation for the effective action. The resummation obtained from the nonperturbative flow is shown to be equivalent to the one performed by the integral equation by Skorniakov and Ter-Martirosian (STM). The flow equation approach allows to integrate out fermions and bosons simultaneously, in line with the fact that the bosons are not fundamental but build up gradually as fluctuation induced bound states of fermions. In particular, the STM result for atom-dimer scattering is obtained by choosing the relative cutoff scales of fermions and bosons such that the fermion fluctuations are integrated out already at the initial stage of the RG evolution.

The low $p_T$ direct photon production from a variety of the hadronic sources is studied within the microscopic hadron-string dynamics transport approach for $p+\mathrm{C}$, $p+\mathrm{Pb}$, and $\mathrm{Pb}+\mathrm{Pb}$ collisions at $160A$ GeV. The direct photon emission from elementary hadronic scatterings as well as meson-meson bremsstrahlung are incorporated. The influence of in-medium effects such as a collisional broadening of the vector-meson spectral functions on the photon emission rate is found to be hardly observable in the final spectra that are dominated by bremsstrahlung-type processes. The uncertainties in the subtraction of the “background” from the photon decay of hadronic resonances inside the hot and dense fireball is investigated, additionally. Our findings are relevant for the interpretation and extraction of experimental data on direct photon production at low $p_T$.

We develop a combined hydro-kinetic approach which incorporates a hydrodynamical expansion of the systems formed in $A+A$ collisions and their dynamical decoupling described by escape probabilities. The method corresponds to a generalized relaxation time (${\tau }_{\mathrm{rel}}$) approximation for the Boltzmann equation applied to inhomogeneous expanding systems; at small ${\tau }_{\mathrm{rel}}$ it also allows one to catch the viscous effects in hadronic component–hadron-resonance gas. We demonstrate how the approximation of sudden freeze-out can be obtained within this dynamical picture of continuous emission and find that hypersurfaces, corresponding to a sharp freeze-out limit, are momentum dependent. The pion $m_T$ spectra are computed in the developed hydro-kinetic model, and compared with those obtained from ideal hydrodynamics with the Cooper-Frye isothermal prescription. Our results indicate that there does not exist a universal freeze-out temperature for pions with different momenta, and support an earlier decoupling of higher $p_T$ particles. By performing numerical simulations for various initial conditions and equations of state we identify several characteristic features of the bulk QCD matter evolution preferred in view of the current analysis of heavy ion collisions at RHIC energies.

A detailed description of the CUORICINO ${}^{130}\mathrm{Te}$ neutrinoless double-beta $(0\hspace{0.5em}\nu \beta \beta )$ decay experiment is given and recent results are reported. CUORICINO is an array of 62 tellurium oxide (${\mathrm{TeO}}_2$) bolometers with an active mass of 40.7 kg. It is cooled to $~8\text{−}10$ mK by a dilution refrigerator shielded from environmental radioactivity and energetic neutrons. It is running in the Laboratori Nazionali del Gran Sasso (LNGS) in Assergi, Italy. These data represent an exposure of 11.83 kg yr or 91 mole-years of ${}^{130}\mathrm{Te}$. No evidence for $0\hspace{0.5em}\nu \beta \beta$-decay was observed and a limit of $T_{1/2}^{0\hspace{0.5em}\nu }({}^{130}\mathrm{Te})⩾3.0\times {10}^{24}\hspace{0.5em}\mathrm{y}$ (90% CL) is set. This corresponds to an upper limit on the effective mass, $\langle m_{\nu }\rangle$, between 0.19 and $0.68$ eV when analyzed with the many published nuclear structure calculations. In the context of these nuclear models, the values fall within the range corresponding to the claim of evidence of $0\hspace{0.5em}\nu \beta \beta$-decay by H. V. Klapdor-Kleingrothaus et al. The experiment continues to acquire data.

The $\Delta I=2$ intruder band in ${}^{111}\mathrm{Sn}$, built upon the 4074.3 keV state, was studied. The states were populated in the ${}^{100}\mathrm{Mo}$(${}^{20}\mathrm{Ne}$, $\alpha 5n$) reaction at a beam energy of 136 MeV. Mean lifetimes of five states up to 8737.2 keV (spin $43/2^{-}$) have been measured for the first time using the Doppler shift attenuation method. In addition, an upper limit of mean lifetime has been estimated for the 9860.0 keV (spin ${47/2}^{-}$) state. The $B(E2)$ values, derived from the present lifetime results, indicate a quadrupole deformation of ${\beta }_2=0.28\pm 0.02$ for the ${31/2}^{-}$ state and decrease progressively with spin, suggesting a reduction in collectivity. The dynamic moment of inertia for the band also decreases continuously up to the highest observed frequencies. These results, along with the predictions of a total Routhian surface calculation, suggest that the $\Delta I=2$ band in ${}^{111}\mathrm{Sn}$ undergoes a change of shape from collective prolate to triaxial with increase in spin and possibly terminates in a noncollective oblate state at a high spin.

Excited states of ${}^4\mathrm{He}$ are studied in four-body calculations with explicitly correlated Gaussian bases. All the levels below $E_x=26$ MeV are reproduced reasonably well using realistic potentials. An analysis is made to show how the $0_2^{+}$ state becomes a resonance but those having almost the same structure as this state in different spin-isospin channels are not observed as resonances. The role of tensor force is stressed with a particular attention to the level spacing between the two $0^{-}$ states. The calculation of spectroscopic amplitudes, nucleon decay widths, and spin-dipole transition strengths demonstrates that the $0_2^{+}$ state and the three lowest-lying negative-parity states with $0^{-}$ and $2^{-}$ have ${}^3\mathrm{H}+p$ and ${}^3\mathrm{He}+n$ cluster configurations, leading to the interpretation that these negative-parity states are the inversion-doublet partners of the $0_2^{+}$ state.

Two-body scattering is studied by solving the Lippmann-Schwinger equation in momentum space without angular-momentum decomposition for a local spin-dependent short-range interaction plus Coulomb. The screening and renormalization approach is employed to treat the Coulomb interaction. Benchmark calculations are performed by comparing our procedure with partial-wave calculations in configuration space for $p\text{−}{}^{10}\mathrm{Be},p\text{−}{}^{16}\mathrm{O}$, and ${}^{12}\mathrm{C}\text{−}{}^{10}\mathrm{Be}$ elastic scattering, using a simple optical potential model.

The ratio of transverse momentum distribution of thermal photons to dilepton has been evaluated. It is observed that this ratio reaches a plateau beyond a certain value of transverse momentum. We argue that this ratio can be used to estimate the initial temperature of the system by selecting the transverse momentum and invariance mass windows judiciously. It is demonstrated that if the radial flow is large then the plateau disappears and hence a deviation from the plateau can be used as an indicator of large radial flow. The sensitivity of the results to various input parameters has been studied.

The basic idea of jet tomography is to infer information about the density evolution of the medium created in heavy-ion ($A\text{−}A$) collisions by studying the suppression of hard probes in an $A\text{−}A$ environment as compared to the baseline process known from proton-proton (p-p) collisions. The suppression of back-to-back correlations in heavy-ion collisions allows, due to a different geometrical bias, a view into the medium that is qualitatively different from the one offered by single-hadron suppression. A control parameter for the suppression corresponding to a systematic variation of in-medium path lengths and densities can be obtained by studying collisions at finite impact parameter $b$. A systematic variation of path length can then be introduced by studying the suppression pattern as a function of the angle ϕ with the reaction plane. Using a three-dimensional hydrodynamic evolution model for the medium and a Monte Carlo model that has been shown to successfully reproduce the measured suppression of back-to-back correlations in central collisions of Au-Au at 200$A$ GeV, we compute the suppression as a function of ϕ for $b$ of 2.4, 4.5, 6.3, and 7.5 fm. Given that this involves variations in both control parameters $b$ and ϕ, a comparison with data should eventually allow one to place strong constraints on the combination of the energy loss model and the medium evolution model.

We study the formalism to include isospin-symmetry-breaking corrections when extracting the up-down Cabibbo-Kobayashi-Maskawa matrix element from superallowed $0^{+}\to 0^{+}$ nuclear $\beta$ decay. We show that there are no first-order isospin-symmetry-breaking corrections to the relevant nuclear matrix elements. We find corrections to the treatment of Towner and Hardy, and assess these using schematic models of increasing complexity.

We have studied the unresolved $\gamma$-ray spectrum of three ytterbium nuclei produced in heavy-ion fusion reactions and measured the two damping widths, ${\Gamma }_{\mu }$, the spreading (compound-damping) width, and ${\Gamma }_{\mathrm{rot}}$, the rotational damping width, together with $P_{\mathrm{nar}}$, the probability that the population enters and leaves a given state via the same component of the wave function. Our results for ${\Gamma }_{\mu }$ and ${\Gamma }_{\mathrm{rot}}$ are in good agreement with theoretical expectations, as well as with those of other groups using different methods. Our results for $P_{\mathrm{nar}}$ lead to a new method for quantitative evaluation of the full order-to-chaos transition in these Yb nuclei. Finally, we provide the first evidence for the motional narrowing of ${\Gamma }_{\mathrm{rot}}$ in nuclei. The basic physics occurring in this region is level mixing, which our simulation technique reproduces surprisingly well.

An experiment has been performed to populate several extremely neutron-deficient nuclei around the mass-140 region of the nuclear chart, using a beam of ${}^{54}\mathrm{Fe}$ on a ${}^{92}\mathrm{Mo}$ target at an energy of 315 MeV. Analysis of these data using recoil-isomer tagging has established that the yrast $\pi h_{11/2}\otimes \nu h_{11/2},J^{\pi }=(8^{+})$, bandhead state in ${}^{136}\mathrm{Pm}$ is isomeric with a half-life of 1.5(1) μs. This isomeric state decays via a 43-keV, probable-$E1$ transition to a $J^{\pi }=(7^{-}$) state. Consideration of the theoretical Nilsson orbitals near the Fermi surface suggests that the $J^{\pi }=(8^{+})$ state has a $\nu h_{11/2}[505]{\frac{11}{2}}^{-}\otimes \pi h_{11/2}[532]{\frac{5}{2}}^{-}$ configuration, which decays to the $J^{\pi }=(7^{-})$ state with a $\nu h_{11/2}[505]{\frac{11}{2}}^{-}\otimes \pi d_{5/2}[411]{\frac{3}{2}}^{+}$ configuration. Differences in the shape-driving effects for these two configurations is reasoned to be responsible for the long half-life of the $J^{\pi }=(8^{+})$ isomeric state. The non-observation of other $\gamma$ rays in prompt or delayed coincidence with the 43-keV transition suggests that this transition may feed another, longer lived isomeric state with a half-life of the order of milliseconds or greater. However, the present experiment was not sensitive to the decay of this new $J^{\pi }=(7^{-}$) state by internal conversion or even $\beta$ decay.

The equation of state of the string model with linear strings comes close to describing the lattice quantum chromodynamics results and allows for the $E/N\approx 6T_0=1\mathrm{GeV}$ relation found in phenomenological statistical model. The $E/N$ value is derived from the zero pressure condition in quark matter and is a fairly general result. The baryochemical potential dependence of the hadron gas can be met if it is interpreted in the framework of an additive quark model. The conclusion is reached that stringy models explain the $E/N=6T_0$ relation naturally and independently of the value of the string tension.

The axial form factor of the nucleon is studied in a two-component model consisting of a three-quark intrinsic structure surrounded by a meson cloud. The experimental data in the space-like region are well reproduced with a minimal number of parameters. The results are similar to those obtained from a dipole fit for $0<Q^2<1\hspace{0.5em}{\mathrm{GeV}}^2$, but outside this region there are important deviations from the dipole parametrization. Finally, the theoretical formula for the axial form factor is extrapolated by analytic continuation to the time-like region, thus providing the first predictions in this kinematical region which is of interest for present and future colliders.

The chiral interpretation of twin bands in odd-odd nuclei was investigated in the interacting boson fermion-fermion model. The analysis of the wave functions has shown that the possibility for angular momenta of the valence proton, neutron and core to find themselves in the favorable, almost orthogonal geometry is present, but not dominant. Such behavior is found to be similar in nuclei where both the level energies and the electromagnetic decay properties display the chiral pattern, as well as in those where only the level energies of the corresponding levels in the twin bands are close together. The difference in the structure of the two types of chiral candidates nuclei can be attributed to different β and γ fluctuations, induced by the exchange boson-fermion interaction of the interacting boson fermion-fermion model. In both cases the chirality is weak and dynamic.

The low-lying, low-spin levels of ${}^{141}\mathrm{Pr}$ were investigated using ($n,n^{\text{'}}\gamma$) techniques. Level energies, branching ratios, and tentative spin assignments for more than 100 states, linked by nearly 300 transitions, were obtained from two angular distributions ($E_n=2.0$ and 3.0 MeV) and an excitation function measurement ($E_n=1.5\text{−}3.2$ MeV). The application of the Doppler-shift attenuation method led to the determination of lifetimes. The obtained spectroscopic data provide insight into the wave functions of the states observed. A detailed analysis of the $[2_1^{+}\otimes d_{5/2}]$ and $[2_1^{+}\otimes g_{7/2}]$ multiplets provides the first quantitative evidence for Pauli blocking in a spherical odd-mass nucleus. The unpaired particle is used to probe the microscopic structure of the first $2^{+}$ state of the adjacent core nuclei ${}^{140}\mathrm{Ce}$ and ${}^{142}\mathrm{Nd}$.

Exclusive light-charged-particle and IMF spectra have been measured with the ISiS detector array for bombardments of ${}^{27}\mathrm{Al}$, ${}^{\mathrm{nat}}\mathrm{Ag}$, and ${}^{197}\mathrm{Au}$ nuclei with 130–270-MeV ${}^3\mathrm{He}$ and 200-MeV protons. The results are consistent with previous interpretations based on inclusive data that describe the global yield of complex fragments in terms of a time-dependent process. The emission mechanism for energetic nonequilibrium fragments observed at forward angles with momenta up to twice the beam momentum is also investigated. This poorly understood mechanism, for which the angular distributions indicate formation on a time scale comparable to the nuclear transit time, are accompanied primarily by thermal-like emissions. The data are most consistent with a schematic picture in which nonequilibrium fragments are formed in a localized region of the target nucleus at an early stage in the energy-dissipation process, where the combined effects of high energy density and Fermi motion produce the observed suprathermal spectra.

We studied shock propagation and its stability with causal dissipative hydrodynamics in ($1+1$)-dimensional systems. We show that the presence of the usual viscosity is not enough to stabilize the solution. This problem is solved by introducing an additional viscosity that is related to the coarse-grain scale of the theory.

Using a single-phase liquid argon detector with a signal yield of 4.85 photoelectrons per keV of electronic-equivalent recoil energy (keVee), we measure the scintillation time dependence of both electronic and nuclear recoils in liquid argon down to 5 keVee. We develop two methods of pulse shape discrimination to distinguish between electronic and nuclear recoils. Using one of these methods, we measure a background- and statistics-limited level of electronic recoil contamination to be $7.6\times {10}^{-7}$ between 52 and 110 keV of nuclear recoil energy (keVr) for a nuclear recoil acceptance of $50\%$ with no nuclear recoil-like events above 62 keVr. Finally, we develop a maximum likelihood method of pulse shape discrimination based on the measured scintillation time dependence.