122536153
Formation of superheavy elements in cold fusion reactions
The process of the synthesis of superheavy elements ~SHEs! is not yet understood completely. In the presented work we make an attempt to describe the cold fusion reactions of the type X1(Pb,Bi)→SHE 11n at subbarrier energies. The process of the formation of SHEs is subdivided into three steps. ~1! The capture of two spherical nuclei and the formation of a common shape of the two touching nuclei. Low-energy surface vibrations and transfer of few nucleons are taken into account in the first step of the reaction. ~2! The formation of a spherical or near spherical compound nucleus. ~3! The survival of the excited compound nucleus due to evaporation of neutrons and g-ray emission in competition with fission. A lowering of the fission barrier was taken into account, which arises from a reduction of shell effects at increasing excitation energy of the compound nucleus. The following reactions were analyzed in detail: (Fe, Ni, Zn, Ge)1Pb, (Ti, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se)1Pb, (Fe, Ni, Zn, Ge) 1Pb, and (Ti, Cr, Fe, Ni, Zn, Ge)1Bi. The presented model describes well the available experimental cross-section data and allows for predicting cross-section values for the synthesis of so-far unknown heavier elements.
119438146
The discovery of the heaviest elements
201093324
Proton Radioactivity
121183473
Observation of rotating nuclear molecules and determination of their lifetimes
Long-living rotating nuclear molecules (or “dinuclear systems”) have been observed at the velocity filter SHIP at GSI in reactions of 64Ni + 207Pb at Coulomb barrier energies. The rotation was directly revealed by the velocity spectra of deep inelastic target-like transfer products which are formed during the lifetime of the nuclear molecule and emitted after its breakup. The corresponding rotation angles were about 180 degree pointing to long nuclear interaction times or lifetimes of the system, respectively. We deduced the lifetimes from the lines in the velocity spectra originating from two different rotation angles. Further, the unambiguous correlation of a certain transfer product with its individual velocity spectrum allowed us to study the lifetimes as a function of the number of transferred protons.
13153867
Mass measurements of very neutron-deficient Mo and Tc isotopes and their impact on rp process nucleosynthesis.
The masses of ten proton-rich nuclides, including the N=Z+1 nuclides ⁸⁵Mo and ⁸⁷Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical x-ray bursts. Surprisingly low α separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.
16408480
Effective Kaon energy from a novel chiral SU(3) model
Abstract A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons and anti-kaons in the nuclear medium, The saturation properties of nuclear matter are reproduced as well as the results of the Dirac-Briickner theory, After introducing the coupling between the omega meson and the kaon, our results for effective kaon and anti-kaon energy are quite similar as calculated in the one-boson-exchange model.
119466901
Small scale WIMP physics
The dark matter distribution on small scales may depend on the the properties of the first generation of dark matter halos to form, which is in turn determined by the microphysics of the dark matter particles. We overview the microphysics of WIMPs and our calculations of the collisional damping and free streaming scales. We then plot the resulting density perturbation power spectrum and red‐shift at which typical halos form, taking into account the effect of uncertainties in the WIMP properties (mass and interaction channel) and the primordial power spectrum. Finally we review recent developments regarding the properties and fate of the first WIMPy halos.
118543996
On nonrelativistic diffeomorphism invariance
We study certain aspects of the recently proposed notion of nonrelativistic diffeomorphism invariance. In particular, we consider specific examples of invariant actions, extended gauge symmetry as well as an application to the theory of quantum Hall effect. We also discuss an alternative approach based on Horava-Lifshitz gravity.
1364874
The First wimpy halos
Dark matter direct and indirect detection signals depend crucially on the dark matter distribution. While the formation of large scale structure is independent of the nature of the cold dark matter (CDM), the fate of inhomogeneities on subgalactic scales, and hence the present day CDM distribution on these scales, depends on the microphysics of the CDM particles. We study the density contrast of weakly interacting massive particles (WIMPs) on subgalactic scales. We calculate the damping of the primordial power spectrum due to collisional damping and free streaming of WIMPy CDM and show that free streaming leads to a CDM power spectrum with a sharp cut-off at about 10(-6) M-circle dot. We also calculate the transfer function for the growth of the inhomogeneities in the linear regime, taking into account the suppression in the growth of the CDM density contrast after matter-radiation equality due to baryons and show that our analytic results are in good agreement with numerical calculations. Combining the transfer function with the damping of the primordial fluctuations we produce a WMAP normalized primordial CDM power spectrum, which can serve as an input for high resolution CDM simulations. We find that the smallest inhomogeneities typically have comoving radius of about 1 pc and enter the nonlinear regime at a red-shift of 60 +/- 20. We study the effect of scale dependence of the primordial power spectrum on these numbers and also use the spherical collapse model to make simple estimates of the properties of the first generation of WIMP halos to form. We find that the very first WIMPy halos may have a significant impact on indirect dark matter searches.
121734598
Thermal decoupling of WIMPs from first principles
Weakly interacting massive particles (WIMPs) are arguably the most natural dark matter candidates from a particle physics point of view. After their number density has frozen out in the early universe, thereby setting their relic density today, WIMPs are still kept very close to thermal equilibrium by scattering events with standard model particles. The complete decoupling from the thermal bath happens as late as at temperatures of around ~1−10 MeV and provides an important cosmological scale that can directly be translated into a small scale cut-off of the spectrum of matter density fluctuations. We present here a full analytic treatment of the kinetic decoupling process from first principles. This allows an exact determination of the decoupling scale, for arbitrary WIMP candidates and any scattering amplitude. As an application, we consider the situation of the lightest supersymmetric particle as well as the lightest Kaluza–Klein particle that arises in theories with universal extra dimensions; furthermore, we show that our formalism can also easily be applied to, e.g., the evolution of the non-relativistic electrons into the recombination regime. Finally, we comment on the impacts for the smallest gravitationally bound structures and the prospects for the indirect detection of dark matter.
17693958
Discrete energy spectrum of Hawking radiation from Schwarzschild surfaces
We analyze the allowed energy levels of Hawking radiation from Schwarzschild surfaces in space-times with large extra dimensions. From the requirement that the wave functions associated with these particles be single-valued and obey radial boundary conditions, we derive an upper bound of their discrete energy spectrum as a function of the number of large extra dimensions and the mass of the black hole. Furthermore, we investigate the spacing of the energy levels.