14020557
Inflaton condensate fragmentation in hybrid inflation models
Inflation ends with the formation of a Bose condensate of inflatons. We show that in hybrid inflation models this condensate is typically unstable with respect to spatial perturbations and can fragment to condensate lumps. The case of D-term inflation is considered as an example and it is shown that fragmentation occurs if λ≳0.2g, where λ is the superpotential coupling and g is the U(1)FI gauge coupling. Condensate fragmentation can result in an effective enhancement of inflaton annihilations over decays as the main mode of reheating. In the case of D-term inflation models in which the standard model fields carry U(1)FI charges, if condensate fragmentation occurs then reheating is dominated by inflaton annihilations, typically resulting in the overproduction of thermal gravitinos. Fragmentation may also have important consequences for SUSY flat direction dynamics and for preheating.
14559444
B-ball baryogenesis and the baryon to dark matter ratio
We demonstrate that B-ball decay in the MSSM can naturally solve the puzzle of why the densities of baryons and dark matter in the Universe are similar. This requires that the B-balls survive thermalization and decay below the freeze-out temperature of the neutralino LSP, typically 1-10 GeV, It is shown that this can happen if the baryon asymmetry originates from a squark condensate along the d = 6 u(c)d(c)d(c) D-flat direction of the MSSM scalar potential. For this to work the reheating temperature after inflation must be no greater than 10(3-5) GeV.
119508847
The dynamics of Affleck-Dine condensate collapse
In the MSSM, cosmological scalar field condensates formed along flat directions of the scalar potential (Affleck-Dine condensates) are typically unstable with respect to formation of Q-balls, a type of non-topological soliton. We consider the dynamical evolution of the Affleck-Dine condensate in the MSSM. We discuss the creation and linear growth, in F- and D-term inflation models, of the quantum seed perturbations which in the non-linear regime catalyse the collapse of the condensate to non-topological soliton lumps. We study numerically the evolution of the collapsing condensate lumps and show that the solitons initially formed are not in general Q-balls, but Q-axitons, a pseudo-breather which can have very different properties from Q-balls of the same charge. We calculate the energy and charge radiated from st spherically symmetric condensate lump as it evolves into a Q-axiton. We also discuss the implications for baryogenesis and dark matter. (C) 2000 Elsevier Science B,V. All rights reserved.
16624602
Flat direction dynamics in a non-topological soliton-dominated universe
In running mass inflation and hybrid inflation models it is possible that the inflaton field will fragment into non-topological solitons, resulting in a highly inhomogeneous post-inflation era prior to reheating. In supersymmetric models with a conventional homogeneous post-inflation era, the dynamics of flat direction scalars are determined by cH2 corrections to the mass squared terms (where ), coming from F-terms in the early universe combined with Planck-scale suppressed interactions. Here we reconsider the mass squared corrections for a universe dominated by inflatonic non-topological solitons. We show that in this case the dynamics of a coherently oscillating flat direction scalar are typically the same as for the case where there is no significant mass squared correction, even in the vicinity of the non-topological solitons. Therefore the dynamics of flat direction scalars in a universe dominated by inflatonic non-topological solitons are equivalent to the case c = 0 of a homogeneous universe.
45299887
Can a Brans-Dicke scalar account for dark matter in extended inflation models?
We discuss the possibility that the dark matter in the Universe could be due to the oscillation of the Brans-Dicke scalar in extended inflation models. The constraints following from the requirement that the energy density perturbations due to quantum scalar field fluctuations are within observational limits, and from the requirement that the energy density in the oscillating Brans-Dicke scalar field, induced by the expansion of bubbles at the first-order phase transition, is smaller than the critical density at present, are discussed for the case of a coupling of the Brans-Dicke scalar to the Ricci scalar of the form phi(n+2)/M(n). Solutions of the equations of motion are given in the slow-rolling approximation for a general value of n, and the cases of n = 0 (minimal extended inflation) and n = 2 are discussed in detail. It is shown that the dominant source of energy density fluctuations produced during inflation is the isocurvature fluctuations of the Brans-Dicke scalar. The requirement that the fluctuations in the microwave background due to the isocurvature fluctuations are not too large implies that the reheat temperature at the end of inflation is less than 3 x 10(13) GeV. For the case where gravity is neglected during the expansion of bubbles at the first-order transition and where the isocurvature fluctuations account for the density perturbations observed by COBE, it is shown that only for a very small range of reheat temperatures at the end of inflation is the model consistent with the requirements that the range of non-Newtonian corrections to the gravitational potential is less that 1 cm and that there are no inhomogeneities in the cosmic microwave background radiation due to large bubbles. If we do not require that the isocurvature fluctuations account for the density perturbations observed by COBE, then the range of reheat temperatures can be larger. In general, the range of non-Newtonian corrections to the gravitational potential is not expected to be much smaller than the present upper limits from Cavendish-type experiments. The possible effects of gravitational suppression of the growth of large bubbles is also considered. It is shown that although gravity can suppress the growth of large bubbles, allowing for a wider range of reheat temperatures and shorter range non-Newtonian forces, gravity will have no effect on bubble percolation at the end of the first-order phase transition. The possible advantages of an oscillating Brans-Dicke scalar with respect to structure formation are considered, in particular, the possibility that the Brans-Dicke scalar could account for both cold and hot dark matter in a combined CDM + HDM scenario for structure formation, with the hot component arising from excitation of the Brans-Dicke scalar field by the expansion of bubbles during the first-order phase transition.
119266670
Cosmological evolution of scalar fields and gravitino dark matter in gauge mediation at low reheating temperatures
We consider the dynamics of the supersymmetry-breaking scalar field and the production of dark matter gravitinos via its decay in a gauge-mediated supersymmetry breaking model with metastable vacuum. We find that the scalar field amplitude and gravitino density are extremely sensitive to the parameters of the hidden sector. For the case of an O'Raifeartaigh sector, we show that the observed dark matter density can be explained by gravitinos even for low reheating temperatures TR10GeV. Such low reheating temperatures may be implied by detection of the NLSP at the LHC if its thermal freeze-out density is in conflict with BBN.
118875304
Preliminary Measurement of the Differential Cross Section from Neutrino-Nucleon Deeply Inelastic Scattering at Nutev
Preliminary results for the neutrino-nucleon differential cross section from the NuTeV experiment are presented. The extraction of the differential cross section from NuTeV is discussed and the structure functions $F_2$ and $\Delta xF_3$ are presented. Comparisons are made with CCFR results.
123577692
Ionization Chambers for Monitoring in High-Intensity Neutrino Beams
Radiation-hard ionization chambers were tested using an intense electron beam from the accelerator test facility (ATF) at the Brookhaven National Laboratory (BNL). The detectors were designed to be used as the basic element for monitoring muons in the Main Injector Neutrino beamline (NuMI) at the Fermi National Accelerator Laboratory (FNAL). Measurements of linearity of response, voltage dependence, and the onset of ionization saturation as a function of gap voltage were performed.
54041161
An optical readout TPC (O-TPC) for studies in nuclear astrophysics with gamma-ray beams at HIγS1
We report on the construction, tests, calibrations and commissioning of an Optical Readout Time Projection Chamber (O-TPC) detector operating with a CO2(80%) + N2(20%) gas mixture at 100 and 150 Torr. It was designed to measure the cross sections of several key nuclear reactions involved in stellar evolution. In particular, a study of the rate of formation of oxygen and carbon during the process of helium burning will be performed by exposing the chamber gas to intense nearly mono-energetic gamma-ray beams at the High Intensity Gamma Source (HI?S) facility. The O-TPC has a sensitive target-drift volume of 30x30x21 cm3. Ionization electrons drift towards a double parallel-grid avalanche multiplier, yielding charge multiplication and light emission. Avalanche-induced photons from N2 emission are collected, intensified and recorded with a Charge Coupled Device (CCD) camera, providing two-dimensional track images. The event's time projection (third coordinate) and the deposited energy are recorded by photomultipliers and by the TPC charge-signal, respectively. A dedicated VME-based data acquisition system and associated data analysis tools were developed to record and analyze these data. The O-TPC has been tested and calibrated with 3.183 MeV alpha-particles emitted by a 148Gd source placed within its volume with a measured energy resolution of 3.0%. Tracks of alpha and 12C particles from the dissociation of 16O and of three alpha-particles from the dissociation of 12C have been measured during initial in-beam test experiments performed at the HI?S facility at Duke University. The full detection system and its performance are described and the results of the preliminary in-beam test experiments are reported.
60877186
Interactive Graphics For Data Analysis
119087432
Ionization chambers for monitoring in high-intensity charged particle beams
Radiation-hard ionization chambers were tested using an intense electron beam from the accelerator test facility at the Brookhaven National Laboratory. The detectors were designed to be used as the basic element for monitoring muons in the Main Injector Neutrino beamline at the Fermi National Accelerator Laboratory. Measurements of linearity of response, voltage dependence, and the onset of ionization saturation as a function of gap voltage were performed.