38172031
Correspondence of I- and Q-balls as non-relativistic condensates
If a real scalar field is dominated by non-relativistic modes, then it approximately conserves its particle number and obeys an equation that governs a complex scalar field theory with a conserved global U(1) symmetry. From this fact, it is shown that the I-ball (oscillon) can be naturally understood as a projection (e.g., real part) of the non-relativistic Q-ball solution. In particular, we clarify that the stability of the I-ball is guaranteed by the U(1) symmetry in the corresponding complex scalar field theory as long as the non-relativistic condition holds. We also discuss the longevity of I-ball from the perspective of the complex scalar field in terms of U(1) charge violating processes.
46432574
Thermalization after/during reheating
A bstractIf reheating of the Universe takes place via Planck-suppressed decay, it seems that the thermalization of produced particles might be delayed, since they have large energy/small number densities and number violating large angle scatterings which decrease the momentum of particles by large amount are inefficient correspondingly. In this paper, we study the thermalization of such “under occupied” decay products in detail, following recent developments in understanding the thermalization of non-abelian plasma. Contrary to the above naive expectation, it is shown that in most cases thermalization after/during reheating occurs instantaneously by properly taking account of scatterings with small angles and of particles with small momenta. In particular, the condition for instantaneous thermalization before the completion of reheating is found to be $ {\alpha^{{{8 \left/ {5} \right.}}}}\gg \left( {{{{{m_{\phi }}}} \left/ {{{M_{\mathrm{pl}}}}} \right.}} \right){{\left( {{{{M_{\mathrm{pl}}^2{\varGamma_{\phi }}}} \left/ {{m_{\phi}^3}} \right.}} \right)}^{{{1 \left/ {5} \right.}}}} $, which is much milder than that obtained in previous works with small angle scatterings taken into account.
119075237
Affleck-Dine Baryogenesis and Dark Matter Production after High-scale Inflation
The discovery of the primordial B-mode polarisation by the BICEP2 experiment indicates inflation with a relatively high energy scale. Taking this indication into account, we propose consistent scenarios to account for the observed baryon and dark matter densities in gravity and gauge mediated supersymmetry breaking models. The baryon asymmetry is explained by the Afflck-Dine mechanism, which requires relatively low reheating temperature to avoid a sizable baryonic isocurvature perturbation. The low reheating temperature then requires non-thermal production of dark matter to account for the correct relic density of dark matter. Our scenarios can account for the observations of baryon and dark matter density in gravity and gauge mediation and predict some parameters, including the mass of dark matter.
118606041
Dark Matter Production in Late Time Reheating
We estimate dark matter density for the Universe with a reheating temperature smaller than the mass of dark matter, assuming dark matter to be a weakly interacting massive particle. During the reheating process, an inaton decays and releases high energy particles, which are scattered inelastically by the thermal plasma and emit many particles. Dark matters are produced through these inelastic scattering processes and pair creation processes by high energy particles. We properly take account of the Landau-Pomeranchuk-Migdal eect on inelastic processes and show that the resultant energy density of dark matter is much larger than that estimated in the literature and can be consistent with that observed when the mass of dark matter is larger than O(100) GeV.
120026676
Light output response of KamLAND liquid scintillator for protons and 12C nuclei
Abstract The light output responses for protons and carbon nuclei in the KamLAND liquid scintillator were precisely measured using a monochromatic neutron beam. The observed response for proton recoils is well described by Birks formula with the higher-order correction, for the recoil energy from 424 keV to 10.5 MeV. The response for carbon recoils is also well described by modifying the Birks formula with the nuclear energy loss terms, for the measured recoil energy from 171 keV to 2.2 MeV. The obtained light output responses were used to estimate the background energy spectrum of the C 13 ( α , n ) O 16 reaction in the KamLAND. The systematic uncertainty of the energy scale in the expected background spectrum was further improved with the measured light output responses.
120784399
Background reduction using single-photoelectron counting for WIMP search
Abstract We have developed a new background reduction method based on single photoelectron counting of scintillators for the WIMP search experiment. We introduced this method to our detector system ELEGANT VI, which has an active shield in all directions ( 4 π ) using a pulse height or, equivalently, the difference in the number of photoelectrons between two (left and right) photomultiplier tubes attached to CaF 2 scintillators. The number distribution is uniquely described by a binomial function, via which we developed the unambiguous background subtraction method. This method reduces the backgrounds further compared to charge-sensitive ADC and offers improved sensitivity for the search for WIMPs.