5,571 research outputs found

    Incorporating Memory Effects in Phase Separation Processes

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    We consider the modification of the Cahn-Hilliard equation when a time delay process through a memory function is taken into account. We then study the process of spinodal decomposition in fast phase transitions associated with a conserved order parameter. Finite-time memory effects are seen to affect the dynamics of phase transition at short times and have the effect of delaying, in a significant way, the process of rapid growth of the order parameter that follows a quench into the spinodal region. These effects are important in several systems characterized by fast processes, like nonequilibrium dynamics in the early universe and in relativistic heavy-ion collisions.Comment: 5 pages, 2 eps figures. Version in press Phys. Lett.

    Roe and Its Global Impact

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    Roe and Its Global Impact

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    A Scalar Boson as a Messenger of New Physics

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    Quantum corrections generate a quadratically divergent mass term for the Higgs boson in the Standard Model. Thus, if the Higgs boson has a mass of order 100 GeV, it implies the presence of a cut-off of the theory around TeV scale, and some particles associated with the new physics may appear around the cut-off scale Λ\Lambda. However, if Λ\Lambda is several TeV, it may be difficult to find such particles at the LHC. In this paper, we consider a situation in which the new physics provides relatively light particles compared with the scale Λ\Lambda. In such a situation, we show that diphoton event and four lepton event by the decay of the Higgs and/or a new particle have naturally large cross section, and LHC may test the new physics in a considerably broad parameter region even if Λ\Lambda is several TeV.Comment: 13 pages, 6 figures; v2 minor correction

    Full one-loop electroweak radiative corrections to single Higgs production in e+ e-

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    We present the full O(α){{\cal O}}(\alpha) electroweak radiative corrections to single Higgs production in \epemt. This takes into account the full one-loop corrections as well as the effects of hard photon radiation. We include both the fusion and Higgs-strahlung processes. The computation is performed with the help of {\tt GRACE-loop} where we have implemented a generalised non-linear gauge fixing condition. The latter includes 5 gauge parameters that can be used for checks on our results. Besides the UV, IR finiteness and gauge parameter independence checks it proves also powerful to test our implementation of the 5-point function. We find that for a 500GeV machine and a light Higgs of mass 150GeV, the total O(α){{\cal O}}(\alpha) correction is small when the results are expressed in terms of αQED\alpha_{{\rm QED}}. The total correction decreases slightly for higher energies. For moderate centre of mass energies the total O(α){{\cal O}}(\alpha) decreases as the Higgs mass increases, reaching -10% for MH=350M_H=350GeV and s=500\sqrt{s}=500GeV. In order to quantify the genuine weak corrections we have subtracted the universal virtual and bremsstrahlung correction from the full O(α){{\cal O}}(\alpha). We find, for MH=150M_H=150GeV, a weak correction slowly decreasing from -2% to -4% as the energy increases from s=300\sqrt{s}=300GeV to s=1\sqrt{s}=1TeV after expressing the tree-level results in terms of GΌG_\muComment: 16 pages, 3 figures. Only correction is a reference to a web-pag

    Neutral atomic carbon in the globules of the Helix

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    We report detection of the 609u line of neutral atomic carbon in globules of the Helix nebula. The measurements were made towards the position of peak CO emission. At the same position, we obtained high-quality CO(2-1) and 13CO(2-1) spectra and a 135" x 135" map in CO(2-1). The velocity distribution of CI shows six narrow (1 -> 2 km/sec) components which are associated with individual globules traced in CO. The CI column densities are 0.5 -> 1.2 x 10^16/cm^2. CI is found to be a factor of ~6 more abundant than CO. Our estimate for the mass of the neutral envelope is an order of magnitude larger than previous estimates. The large abundance of CI in the Helix can be understood as a result of the gradual photoionisation of the molecular envelope by the central star's radiation field.Comment: 5 pages, Latex, AAS macros, 3 EPS figures, to appear in Astrophysical Journal Letter

    Energy minimization using Sobolev gradients: application to phase separation and ordering

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    A common problem in physics and engineering is the calculation of the minima of energy functionals. The theory of Sobolev gradients provides an efficient method for seeking the critical points of such a functional. We apply the method to functionals describing coarse-grained Ginzburg-Landau models commonly used in pattern formation and ordering processes.Comment: To appear J. Computational Physic

    Prospects for detecting an ηcâ€Č\eta_c' in two photon processes

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    We argue that an experimental search for an ηcâ€Č\eta_c', the first radial excitation of the ηc(2980)\eta_c(2980), may be carried out using the two photon process e^+e^- \to e^+e^- \gamma \gamma \ra e^+e^-\eta_c'. We estimate the partial width Γγγ(ηcâ€Č)\Gamma_{\gamma \gamma}(\eta_c') and the branching fraction B(ηcâ€Č→h)B(\eta_c' \to h), where hh is an exclusive hadronic channel, and find that for h=KsoK±π∓h = K^o_s K^\pm \pi^\mp it may be possible to observe this state in two photon collisions at CLEO-II.Comment: 9 pages, LATEX forma

    The Higgs Boson Might Not Couple To B Quarks

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    We discuss an alternative version of the electroweak standard model, in which only the heavy t quark, not the light fermions, couples to the Higgs boson with a strength given by the standard model. The Higgs particle decays dominantly into two gluons jets. The branching ratio for the 2 gamma decay is about 3.5%. The Higgs particle would be a narrow object (width about 60 KeV), and its mass might be consistent with the value given by typical estimates of radiative effects measured by the LEP experiments.Comment: 7 pages, 6 figures, to appear in Physics Letters

    Flavor changing interactions mediated by scalars at the weak scale

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    The quark and lepton mass matrices possess approximate flavor symmetries. Several results follow if the interactions of new scalars possess these approximate symmetries. Present experimental bounds allow these exotic scalars to have a weak scale mass. The Glashow-Weinberg criterion is rendered unnecessary. Finally, rare leptonic B meson decays provide powerful probes of these scalars, especially if they are leptoquarks.Comment: 13 pages, report LBL-3234
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