343 research outputs found

    Proteasome inhibitors as a possible therapy for SARS-CoV-2

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    The COVID-19 global pandemic is caused by SARS-CoV-2, and represents an urgent medical and social issue. Unfortunately, there is still not a single proven effective drug available, and therefore, current therapeutic guidelines recommend supportive care including oxygen administration and treatment with antibiotics. Recently, patients have been also treated with off-label therapies which comprise antiretrovirals, anti-inflammatory compounds, antiparasitic agents and plasma from convalescent patients, all with controversial results. The ubiquitin–proteasome system (UPS) is important for the maintenance of cellular homeostasis, and plays a pivotal role in viral replication processes. In this review, we discuss several aspects of the UPS and the effects of its inhibition with particular regard to the life cycle of the coronaviruses (CoVs). In fact, proteasome inhibition by various chemical compounds, such as MG132, epoxomycin and bortezomib, may reduce the virus entry into the eucariotic cell, the synthesis of RNA, and the subsequent protein expression necessary for CoVs. Importantly, since UPS inhibitors reduce the cytokine storm associated with various inflammatory conditions, it is reasonable to assume that they might be repurposed for SARS-CoV-2, thus providing an additional tool to counteract both virus replication as well as its most deleterious consequences triggered by abnormal immunological response

    Deconstructing Non-Abelian Gauge Theories at One Loop

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    Deconstruction of 5D Yang-Mills gauge theories is studied in next-to-leading order accuracy. We calculate one-loop corrections to the mass spectrum of the non-linear gauged sigma-model, which is the low energy effective theory of the deconstructed theory. Renormalization is carried out following the standard procedure of effective field theories. The relation between the radius of the compactified fifth dimension and the symmetry breaking scale of the non-linear sigma-model is modified by radiative corrections. We demonstrate that one can match the low lying spectrum of the gauge boson masses of the effective 4D gauged non-linear sigma-model to the Kaluza-Klein modes of the 5D theory at one-loop accuracy

    Limits on a Composite Higgs Boson

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    Precision electroweak data are generally believed to constrain the Higgs boson mass to lie below approximately 190 GeV at 95% confidence level. The standard Higgs model is, however, trivial and can only be an effective field theory valid below some high energy scale characteristic of the underlying non-trivial physics. Corrections to the custodial isospin violating parameter T arising from interactions at this higher energy scale dramatically enlarge the allowed range of Higgs mass. We perform a fit to precision electroweak data and determine the region in the (m_H, Delta T) plane that is consistent with experimental results. Overlaying the estimated size of corrections to T arising from the underlying dynamics, we find that a Higgs mass up to 500 GeV is allowed. We review two composite Higgs models which can realize the possibility of a phenomenologically acceptable heavy Higgs boson. We comment on the potential of improvements in the measurements of m_t and M_W to improve constraints on composite Higgs models.Comment: 9 pages, 2 eps figures. Shortened for PRL; some references elminate

    The Electroweak Chiral Lagrangian and CP-Violating Effects in Technicolor Theories

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    We estimate the CP-violating WWγWW\gamma and WWZWWZ anomalous form factors, arising from CP-violating interactions in extended technicolor theories, and discuss their future experimental detectability. The electric dipole moment of the WW boson is found to be as large as {\cal O}(10^{-21}) \; \mbox{e cm}. We connect the CP-odd WWγWW\gamma and WWZWWZ couplings to the corresponding CP-violating electroweak chiral lagrangian operators. The electric dipole moments of the neutron and the electron in technicolor theories are estimated to be as large as {\cal O}(10^{-26}) \; \mbox{e cm} and {\cal O}(10^{-29}) \; \mbox{e cm} respectively. We also suggest the potential to observe large CP-violating technicolor effects in the decay tb+W+t \rightarrow b + W^+.Comment: 34 pages, YCTP-P9-94, LaTex. (minor changes in wording and notation, the figures are appended at the end as one postscript file

    Analyticity, Crossing Symmetry and the Limits of Chiral Perturbation Theory

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    The chiral Lagrangian for Goldstone boson scattering is a power series expansion in numbers of derivatives. Each successive term is suppressed by powers of a scale, Λχ\Lambda_\chi, which must be less than of order 4πf/N4\pi f/\sqrt{N} where ff is the Goldstone boson decay constant and NN is the number of flavors. The chiral expansion therefore breaks down at or below 4πf/N4 \pi f/\sqrt{N}. We argue that the breakdown of the chiral expansion is associated with the appearance of physical states other than Goldstone bosons. Because of crossing symmetry, some ``isospin'' channels will deviate from their low energy behavior well before they approach the scale at which their low energy amplitudes would violate unitarity. We argue that the estimates of ``oblique'' corrections from technicolor obtained by scaling from QCD are untrustworthy.Comment: harvmac, 18 pages (3 figures), HUTP-92/A025, BUHEP-92-18, new version fixes a TeX problem in little mod

    Low-Energy Constraints on New Physics Revisited

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    It is possible to place constraints on non-Standard-Model gauge-boson self-couplings and other new physics by studying their one-loop contributions to precisely measured observables. We extend previous analyses which constrain such nonstandard couplings, and we present the results in a compact and transparent form. Particular attention is given to comparing results for the light-Higgs scenario, where nonstandard effects are parameterized by an effective Lagrangian with a linear realization of the electroweak symmetry breaking sector, and the heavy-Higgs/strongly interacting scenario, described by the electroweak chiral Lagrangian. The constraints on nonstandard gauge-boson self-couplings which are obtained from a global analysis of low-energy data and LEP/SLC measurements on the Z pole are updated and improved from previous studies. Replaced version: tables and figures of Section VIb recalculated. There were roundoff problems, especially in Fig. 8. Text unchanged.Comment: \documentstyle[preprint,aps,floats,psfig]{revtex}, 10 figures, postscript version available from ftp://ftp.kek.jp/kek/preprints/TH/TH-51

    Complete analysis on the next-to-leading order supersymmetric QCD corrections to B0Bˉ0B^0-\bar{B}^0 mixing

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    We present a complete next-to-leading-order calculation of the QCD corrections to B0Bˉ0B^0-\bar{B}^0 (K0Kˉ0K^0-\bar{K}^0) mixing in the framework of the minimal flavor violating (MFV) supersymmetry. We take into account the contributions from the gluino and find that the gluino-mediated corrections modify the LO result obviously even when the mass of gluino mg~mwm_{\tilde{g}} \gg m_{\rm w}. In general, one cannot neglect gluino contributions.Comment: 91 pages + 11 eps figures, publication version in PR

    The Effective Electroweak Chiral Lagrangian: The Matter Sector

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    We parametrize in a model-independent way possible departures from the minimal Standard Model predictions in the matter sector. We only assume the symmetry breaking pattern of the Standard Model and that new particles are sufficiently heavy so that the symmetry is non-linearly realized. Models with dynamical symmetry breaking are generically of this type. We review in the effective theory language to what extent the simplest models of dynamical breaking are actually constrained and the assumptions going into the comparison with experiment. Dynamical symmetry breaking models can be approximated at intermediate energies by four-fermion operators. We present a complete classification of the latter when new particles appear in the usual representations of the SU(2)L×SU(3)cSU(2)_L\times SU(3)_c group as well as a partial classification in the general case. We discuss the accuracy of the four-fermion description by matching to a simple `fundamental' theory. The coefficients of the effective lagrangian in the matter sector for dynamical symmetry breaking models (expressed in terms of the coefficients of the four-quark operators) are then compared to those of models with elementary scalars (such as the minimal Standard Model). Contrary to a somewhat widespread belief, we see that the sign of the vertex corrections is not fixed in dynamical symmetry breaking models. This work provides the theoretical tools required to analyze, in a rather general setting, constraints on the matter sector of the Standard Model.Comment: Latex, 45 pages, 8 eps figures. Sections 5, 6 and 9 have been rewritten to clarify the contents. Some mistakes and typos have been corrected. Two references have been added. Figures 7 and 8 have been modifie

    Top-Charm Associated Production in High Energy e+ee^+e^- Collisions

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    The possibility of exploring the flavor changing neutral current tcZ/tcγtcZ/tc\gamma couplings in the production vertex for the reaction \epem\to t\bar c + \bar tc is examined. Using a model independent parameterization for the effective Lagrangian to describe the most general three-point interactions, production cross sections are found to be relatively small at LEP II, but potentially sizeable at higher energy \epem colliders. The kinematic characteristics of the signal are studied and a set of cuts are devised for clean separation of the signal from background. The resulting sensitivity to anomalous flavor changing couplings at LEP II with an integrated luminosity of 4×5004\times 500 pb1^{-1} is found to be comparable to their present indirect constraints from loop processes, while at higher energy colliders with 0.510.5-1 TeV center-of-mass energy and 50-200 fb1^{-1} luminosity, one expects to reach a sensitivity at or below the percentage level.Comment: Latex, 22 page

    Contributions of LEP1.5, LEP2 and linear-collider data to indirect constraints on non-Abelian gauge-boson couplings

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    It is possible to place direct constraints on WW-photon and WWZ couplings by studying their tree-level contributions to the process e^+e^- ---> W^+W^-. However, these couplings also contribute at the loop level to e^+e^- ---> f fbar processes where `f' is any Standard-Model fermion. In this paper the available LEP1.5 and LEP2 data, the anticipated LEP2 data and possible linear collider data for these latter processes is combined with low-energy and Z-pole data to place indirect constraints on nonstandard WW-photon and WWZ couplings. The direct and indirect constraints are then compared. An effective Lagrangian is used to describe the new physics. In order that the implications of this analysis are as broad as possible, both the light-Higgs scenario, described by an effective Lagrangian with a linear realization of the symmetry-breaking sector, and the strongly interacting scenario, described by the electroweak chiral Lagrangian, are considered.Comment: \documentstyle[preprint,aps,floats,psfig]{revtex}, 4 figures, postscript version available from ftp://ftp.kek.jp/kek/preprints/TH/TH-53
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