Discovery of Long-Lived Shape Isomeric States which Decay by Strongly Retarded High-Energy Particle Radioactivity

The reaction 28Si + 181Ta has been studied at E(Lab) = 125 and 135 MeV. Coincidences between high energy particles and various X- and gamma-rays from abnormally long-lived states were observed. e.g. 7.8 - 8.6 MeV alpha-particles with gamma-rays of a superdeformed band, 5.1 - 5.5 MeV alpha-particles with X- and gamma-rays of W, Re, and Pt, and 3.88 MeV particles (interpreted as protons) with 185.8 keV gamma-rays. The data are interpreted in terms of the production of long-lived (t(1/2) of several months) high spin isomeric states in the second well of the potential in the parent nuclei, which decay to the normal states in the daughters, and in the third well of the potential, which decay to the second well.Comment: 25 pages including 11 figures and 3 table

Singlino dominated LSP as CDM candidate in supersymmetric models with an extra U(1)

We consider a singlino dominated neutralino in supersymmetric models with an extra U(1). In case both the $\mu$ term and also the $Z^\prime$ mass are generated by the vacuum expectation value of the scalar component of the same singlet chiral superfield, generically the lightest neutralino is not expected to be dominated by the singlino. However, if the gaugino corresponding to the extra U(1) is sufficiently heavy, the lightest neutralino can be dominated by the singlino and still satisfy the constraints resulting from the $Z^\prime$ phenomenology. We assume a supersymmetry breaking scenario in which the extra U(1) gaugino can be much heavier than other gauginos. In that framework we show that the singlino dominated lightest neutralino may be a good candidate for dark matter in a parameter space where various phenomenological constraints are satisfied.Comment: 25 pages, 6 figures, title is changed, introduction is extended, sec.2 is moved to appendix, some references are added, published versio

Self-intersecting marginally outer trapped surfaces

We have shown previously that a merger of marginally outer trapped surfaces (MOTSs) occurs in a binary black hole merger and that there is a continuous sequence of MOTSs which connects the initial two black holes to the final one. In this paper, we confirm this scenario numerically and we detail further improvements in the numerical methods for locating MOTSs. With these improvements, we confirm the merger scenario and demonstrate the existence of self-intersecting MOTSs formed in the immediate aftermath of the merger. These results will allow us to track physical quantities across the non-linear merger process and to potentially infer properties of the merger from gravitational wave observations

A Note on Gravitational Baryogenesis

The coupling between Ricci scalar curvature and the baryon number current dynamically breaks CPT in an expanding universe and leads to baryon asymmetry. We study the effect of time dependence of equation of state parameter of the FRW universe on this asymmetry.Comment: 10 pages, accepted for publication in Physical Review

Scaling of v2v_2 in heavy ion collisions

We interpret the scaling of the corrected elliptic flow parameter w.r.t. the corrected multiplicity, observed to hold in heavy ion collisions for a wide variety of energies and system sizes. We use dimensional analysis and power-counting arguments to place constraints on the changes of initial conditions in systems with different center of mass energy $\sqrt{s}$. Specifically, we show that a large class of changes in the (initial) equation of state, mean free path, and longitudinal geometry over the observed $\sqrt{s}$ are likely to spoil the scaling in $v_2$ observed experimentally. We therefore argue that the system produced at most Super Proton Synchrotron (SPS) and Relativistic Heavy Ion Collider (RHIC) energies is fundamentally the same as far as the soft and approximately thermalized degrees of freedom are considered. The ``sQGP'' (Strongly interacting Quark-Gluon Plasma) phase, if it is there, is therefore not exclusive to RHIC. We suggest, as a goal for further low-energy heavy ion experiments, to search for a ``transition'' $\sqrt{s}$ where the observed scaling breaks.Comment: Accepted for publication by Phys. Rev. C Based on presentation in mini-symposium on QGP collective properties, Frankfurt. Discussion expanded, results adde

Coherent Description for Hitherto Unexplained Radioactivities by Super- and Hyperdeformed Isomeric States

Recently long-lived high spin super- and hyperdeformed isomeric states with unusual radioactive decay properties have been discovered. Based on these newly observed modes of radioactive decay, consistent interpretations are suggested for previously unexplained phenomena seen in nature. These are the Po halos, the low-energy enhanced 4.5 MeV alpha-particle group proposed to be due to an isotope of a superheavy element with Z = 108, and the giant halos.Comment: 8 pages, 2 figures, 1 table, to be published in Int. J. Mod. Phys.

Reheating and gravitino production in braneworld inflation

We consider the constraints that can be imposed on a wide class of Inflation models in modified gravity scenarios in which the Friedmann equation is modified by the inclusion of $\rho^2$ terms, where $\rho$ is the total energy density. In particular we obtain the reheating temperature and gravitino abundance associated with the end of inflation. Whereas models of chaotic inflation and natural inflation can easily avoid the conventional gravitino overproduction problem, we show that supersymmetric hybrid inflation models (driven by both F and D-terms) do not work in the $\rho^2$ dominated era. We also study inflation driven by exponetial potentials in this modified background, and show that the gravitino production is suppressed enough to avoid there being a problem, although other conditions severely constrain these models.Comment: 24page

Neutralino dark matter in brane world cosmology

The thermal relic density of the neutralino dark matter in the brane world cosmology is studied. Since the expansion law at a high energy regime in the brane world cosmology is modified from the one in the standard cosmology, the resultant relic density can be altered. It has been found that, if the five dimensional Planck mass $M_5$ is lower than $10^4$ TeV, the brane world cosmological effect is significant at the decoupling time and the resultant relic density is enhanced. We calculate the neutralino relic density in the Constrained Minimal Supersymmetric Standard Model (CMSSM) and show that the allowed region is dramatically modified from the one in the standard cosmology and eventually disappears as $M_5$ is decreasing. We also find a new lower bound on $M_5 \gtrsim 600$ TeV based on the neutralino dark matter hypothesis, namely the lower bound in order for the allowed region of the neutralino dark matter to exist.Comment: 12 pages, 8 figure