9782765
Gauge singlet scalars as cold dark matter.
We consider a very simple extension of the standard model in which one or more gauge singlet scalars S-i couples to the standard model via an interaction of the form lambda(S)S(i)(dagger)S(i)H(dagger)H, where H is the standard model Higgs doublet. The thermal relic density of S scalars is calculated as a function of the coupling lambda(S) and the S scalar mass ms. The regions of the (m(S),lambda(S)) parameter space which can be probed by present and future experiments designed to detect scattering of S dark matter particles from Ge nuclei, and to observe upward-moving muons and contained events in neutrino detectors due to high-energy neutrinos from annihilations of S dark matter particles in the Sun and the Earth, are discussed. Present experimental bounds place only very weak constraints on the possibility of thermal relic S scalar dark matter. The next generation of cryogenic Ge detectors and of large area (10(4) m(2)) neutrino detectors will be able to investigate most of the parameter space corresponding to thermal relic S scalar dark matter up to m(S) approximate to 50 GeV, while a 1 km(2) detector would in general be able to detect thermal relic S scalar dark matter up to m(S) approximate to 100 GeV and would be able to detect up to m(S) approximate to 500 GeV or more if the Higgs boson is lighter than 100 GeV.
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.
14318680
Supergravity and two-field inflation effects in right-handed sneutrino modified D-term inflation.
We extend previous work on the minimal D-term inflation model modified by right-handed (RH) sneutrino fields to include additional inflaton-sector supergravity corrections and two-field inflation effects. We show that supergravity corrections simultaneously allow ns to be within 3-year Wilkinson Microwave Anisotropy Probe limits and the cosmic string contribution to the cosmic microwave background (CMB) power spectrum to be less than 5%. For gauge coupling g 0.1H. The running spectral index is alpha[approximate]-0.0002 when mPhi 0.008 for mPhi>1.0H.
14078444
Dynamical cosmological constant from a very recent phase transition
Observation indicates that the expansion of the Universe is accelerating and favours a dynamical cosmological constant, Λ(t). We consider the possibility that this is due to a scalar field which has undergone a very recent phase transition. We study a simple class of model, corresponding to a φ4 potential with a time-dependent mass squared term. For the models considered the phase transition occurs at a red shift z⩽1.2. The evolution of the equation of state ωφ and energy density ρφ with time is distinct from existing dynamical Λ models based on slowly rolling fields, with ωφ and ρφ rapidly changing in a characteristic way following the transition. The φ energy density is composed of a time-dependent vacuum energy and coherently oscillating condensate component with a negative pressure. The condensate component will typically collapse to form non-topological soliton lumps, ‘φ-axitons’, which smoothly populate the Universe.
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.
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.
20474546
Measurements of atomic level widths in thulium: Effect on the measurement of neutrino mass from tritium beta decay spectra.
Measurements have been made with curved crystal x-ray spectrometers of the natural line widths of the L/sub 1/M/sub 2/ (GAMMA = 12.1 +- 2 eV), L/sub 1/M/sub 3/ (GAMMA = 12.7 +- 1 eV), and M/sub 1/N/sub 3/ (GAMMA = 19 +- 3 eV) atomic transitions in Tm. These results are combined with published results to determine M/sub 1/, M/sub 2/, and M/sub 3/ internal conversion line widths for /sup 169/Tm. These lines have been used in the calibration of a beta spectrometer for recent measurements of the electron antineutrino mass from the tritium beta decay spectrum. A reanalysis of these results suggests that there is no conclusive evidence for a finite mass for the electron antineutrino.
26401416
Weak pion-nucleon coupling strength: New constraint from parity mixing in 18F.
The circular polarization of the 1.081 MeV γ rays from 18F has been measured to be (1.7±5.8)×10-4. 18F was produced by a 4.05 MeV 3He+ beam impinging on a recirculating water target with a thin entrance window. The circular polarization was measured with four magnetic transmission polarimeters, each backed by a 150 cm3 n-type Ge detector. A fast data acquisition system limited overall peak losses to 30% at a count rate of 60 kHz per detector. Supplementary experiments were carried out to investigate the sensitivity of the circular polarization measurement to systematic variations of beam position and intensity. These effects were found to be negligible relative to the statistical uncertainty. The experimental result is interpreted in terms of an isovector parity-nonconserving matrix element between the ‖0+,T=1,1.042 MeV〉 and ‖0-,T=0,1.081 MeV〉 states in 18F that is dominated by the weak pion exchange contribution. The present result for the weak pion-nucleon coupling strength is ‖fπ1‖=(0.4-0.4+1.4)×10-7, which is significantly smaller than recent theoretical predictions based on the Weinberg-Salam model.