124068899
Structure equations for a monopole model with a coleman-weinberg potential
SummaryA model consisting of aSO3 gauge field interacting with an isovector Higgs field is investigated. When the Higgs mass parameter vanishes, no symmetry breakdown occurs at the tree level, but may be induced at the one-loop level. The one-loop effective potential is of the Coleman-Weinberg type, which is required of many new inflationary cosmological scenarios. Approximate equations determining the structure of a magnetic monopole are obtained at the one-loop level of this model.RiassuntoSi studia un modello ehe consiste in un campo di gauge SO3 che interagisce con un campo di Higgs isovettoriale. Quando il parametro di massa di Higgs si annulla non si verifica una rottura di simmetria a livello di albero, ma tale rottura si può indurre a livello di un loop. Il Potenziale efficace ad un loop è del tipo di Coleman-Weinberg, cui sono richiesti molti nuovi scenari di espansione cosmologica. Si ottengono equazioni approssimate che determinano la struttura di un monopolo magnetico al livello di un loop di questo modello.
120292912
Gravitational field of a superconducting global string
SummaryThe Newtonian gravitational field of a superconducting global cosmic string is investigated using the weak-field approximation, and is found to receive contributions from the global string field, the condensate field, and the electromagnetic fields. For certain parameter ranges the gravitational field in the region exterior to the string may be everywhere repulsive, everywhere attractive, or repulsive in some regions and attractive in others. For a neutral superconducting global string there can exist a particular current for which the gravitational field of the superconducting global string approximately coincides with that of a Grand Unified Theory (GUT) scale Weyl string, and, as pointed out by Widom, Srivastava, and Redington, observed asymptotic galactic rotation velocities can be roughly explained without the introduction of any further dark-matter hypothesis.
29278740
Domain defects in strings and walls.
A type of model is considered where the Witten mechanism allows the breaking of a discrete symmetry within the core of a cosmic string or a domain wall. The formation of a real scalar field condensate results in the creation of different, but energetically degenerate, domains which are separated by massive domain defects. The defects within strings (domain kinks) are particlelike states, whereas the defects within walls (domain ribbons) resemble stringlike states. Relativistic kink-antikink pairs annihilate after their initial formation, with the release of boson radiation, and kink-antikink pairs can be created through string intercommutations. Ribbons and antiribbons can be either infinite in extent or form closed loops. Ribbon loops can be involved in fission or fusion processes producing boson radiation, and oscillating ribbon loops decay mainly through the production of boson radiation, with a negligible fraction of the released energy being emitted in the form of gravitational radiation.
8897328
Supersymmetry breaking and Fermi balls.
A simple model is presented where the disappearance of domain walls and the associated production of {open_quote}{open_quote}Fermi balls,{close_quote}{close_quote} which have been proposed as candidates for cold dark matter, are features which arise rather naturally in response to softly broken supersymmetry. {copyright} {ital 1996 The American Physical Society.}
120927641
A parameterization forSO(3) Yang-Mills-Higgs systems
SummaryA model consisting of anSO(3) gauge field interacting with an isovector Higgs field is investigated. The gauge fields and field tensors are parameterized by the Higgs field directionality and a gauge field structure function in terms of which the magnetic field and magnetic charge density of a 't Hooft-Polyakov magnetic monopole can be simply expressed. An isovector Debye potential for a 't Hooft-Polyakov gauge field is written in terms of the gauge field structure function.
119125621
Moduli vacuum bubbles produced by evaporating black holes
We consider a model with a toroidally compactified extra dimension giving rise to a temperature-dependent 4D effective potential with one-loop contributions due to the Casimir effect, along with a 5D cosmological constant. The forms of the effective potential at low and high temperatures indicate a possibility for the formation of a domain wall bubble, formed by the modulus scalar field, surrounding an evaporating black hole. This is viewed as an example of a recently proposed black hole vacuum bubble arising from matter-sourced moduli fields in the vicinity of an evaporating black hole [D. Green, E. Silverstein, and D. Starr, Phys. Rev. D 74, 024004 (2006)]. The black hole bubble can be highly opaque to lower-energy particles and photons, and thereby entrap them within. For high-temperature black holes, there may also be a symmetry-breaking black hole bubble of false vacuum of the type previously conjectured by Moss [I. G. Moss, Phys. Rev. D 32, 1333 (1985)], tending to reflect low-energy particles from its wall. A double bubble composed of these two different types of bubble may form around the black hole, altering the hole's emission spectrum that reaches outside observers. Smaller mass black holes that have already evaporated away could have left vacuum bubbles behind that contribute to the dark matter.
22405819
A search for narrow resonances in proton-proton collisions at 53 GeV centre-of-mass energy
Abstract A search for narrow resonances produced in pp collisions at the CERN ISR has been carried out using two magnetic spectrometers to measure and identify two-final-state charged hadrons. The resultant two-particle invariant mass spectra show no strong structure suggesting any new narrow resonance. The statistical significance of various enhancements seen in the data is discussed, and upper limits on the cross section times branching ratio for new particle production are presented.
121418547
Observation of pairs of charmed particles produced by high-energy photons in nuclear emulsions coupled with a magnetic spectrometer
Abstract Preliminary results of an experiment using nuclear emulsions exposed to a tagged photon beam at the CERN SPS (experiment WA58) are presented. Six events showing pairs of charmed particles have been found. One of these has been interpreted as an associated production of Λ c + and D 0 . The mean lifetime of the neutral D meson based on three events is τ 0 = (0.58 −0.2 +0.8 × 10 −13 s,, whereas a statistical analysis of eight charged charmed particles, assumed to be D mesons, leads to an estimate of the mean lifetime of τ ± ≈ 4.4 × 10 −13 s.
120429047
The design of the optical components and gas control systems of the CERN Omega ring imaging Cherenkov detector
Abstract A large ring imaging Cherenkov detector (RICH) has been commissioned for use at the CERN Omega spectrometer. In the first of a series of reports we begin by discussing the general design of the device and illustrate the dependence of the attainable spatial resolution and range of particle identification on its optical parameters. We then describe in detail the construction and performance of the major optical components and gas systems of the detector.
122300884
Forward electroproduction of single charged pions in the resonance region using a deuterium target
Abstract The rates for forward electroproduction of single charged pions from deutrium have been measured in the resonance region, at a virtual photon mass squared ≈−0.5( GeV/ c 2 ) 2 . Results are presented in the form of a π− to π + cross-section ratio.
209918258
Observation of an $\omega \pi^0$ State of Mass 1.25-{GeV} Produced by Photons of Energy 20-{GeV} - 70-{GeV}