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.
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.
116132021
PRIMORDIAL INFLATION WITH FLAT SUPERGRAVITY POTENTIALS DUE TO D TERMS
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.
2260171
SUPERSYMMETRIC D-TERM INFLATION AND B-BALL BARYOGENESIS
We consider the B-ball cosmology of the minimal supersymmetric standard model in the context of D-term inflation models where the reheating temperature is determined by the Affleck-Dine mechanism to be of the order of 1 GeV. We show that such a low reheating temperature can arise quite naturally as the result of a symmetry which is required to maintain the flatness of the inflaton potential. In this case the B-balls will decay well after the freeze-out temperature of the lightest supersymmetric particle, allowing baryons and cold dark matter to originate primarily from B-ball decays. [S0031-9007(98)07324-4].
42466564
CP violation for electroweak baryogenesis from mixing of standard model and heavy vector quarks.
It is known that the CP violation in the minimal standard model is insufficient to explain the observed baryon asymmetry of the Universe in the context of electroweak baryogenesis. In this paper we consider the possibility that the additional CP violation required could originate in the mixing of the standard model quarks and heavy vector quark pairs. We consider the baryon asymmetry in the context of the spontaneous baryogenesis scenario. It is shown that, in general, the CP-violating phase entering the mass matrix of the standard model and heavy vector quarks must be space dependent in order to produce a baryon asymmetry, suggesting that the additional CP violation must be spontaneous in nature. This is true for the case of the simplest models which mix the standard model and heavy vector quarks. We derive a charge potential term for the model by diagonalizing the quark mass matrix in the presence of the electroweak bubble wall, which turns out to be quite different from the fermionic hypercharge potentials usually considered in spontaneous baryogenesis models, and obtain the rate of baryon number generation within the wall. We find, for the particular example where the standard model quarks mix with weak-isodoublet heavy vector quarks via the expectation value of a gauge singlet scalar, that we, can account for the observed baryon asymmetry with conservative estimates for the uncertain parameters of electroweak baryogenesis, provided that the heavy vector quarks are not heavier than a few hundred GeV and that the coupling of the standard model quarks to the heavy vector quarks and gauge singlet scalars is not much smaller than order of 1, corresponding to a mixing angle of the heavy vector quarks and standard model quarks not much smaller than order of 10(-1).
123166163
Smoothing with split linear fits
We introduce a family of smoothing algorithms that can produce discontinuous output. Unlike most commonly used smoothers, that tend to blur discontinuities in the data, this smoother can be used for smoothing with edge detection. We cite examples of other approaches to (two-dimensional) smoothing with edge detection in image processing, and apply our one-dimensional smoother to sea surface temperature data where the discontinuities arise from changes in ocean currents.
117580235
A precision measurement of the lithium-7(d, p) lithium-8 reaction cross section
118737108
Search for single top production with the D0 detector at the Fermilab Tevatron Collider
We attempt to identify a single top signal in the muon + jets data collected using the D0 detector at the Fermilab Tevatron at a center-of-mass energy of {radical}s = 1.8 TeV from 1992-96. The data corresponds to an integrated luminosity of 103.7 pb{sup -1}. While resolving a signal has proved impossible, we are able to place an upper limit on the production cross section for single top events using these data. The cross section for production of single top via 95% p{bar p} {yields} tb and p{bar p} {yields} qtb is less than 78 pb at the 95% confidence level based on muon + jets data only.
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.
62325539
Computing Environments for Data Analysis. Part 2. Hardware
This is the second in a series of papers on aspects of modern computing environments that are relevant to statistical data analysis. We argue that a network of graphics workstations is far superior to conventional batch or time-sharing computers as an environment for interactive data analysis. The second paper in the series discusses the hardware of graphics workstations in detail.