Showing papers on "Electroweak interaction published in 1995"
TL;DR: The generality of the arguments rules out any mechanism of electroweak baryogenesis that does not make use of a new source of [ital CP] violation and concludes the QCD damping effects reduce the asymmetry produced to a negligible amount.
Abstract: We analyze the mechanism of electroweak baryogenesis proposed by Farrar and Shaposhnikov in which the phase of the CKM mixing matrix is the only source of [ital CP] violation. This mechanism is based on a phase separation of baryons via the scattering of quasiparticles by the wall of an expanding bubble produced at the electroweak phase transition. In agreement with the recent work of Gavela, Hernandez, Orloff, and Pene, we conclude the QCD damping effects reduce the asymmetry produced to a negligible amount. We interpret the damping as quantum decoherence. We compute the asymmetry analytically. Our analysis reflects the observation that only a thin, outer layer of the bubble contributes to the coherent scattering of the quasiparticles. The generality of our arguments rules out any mechanism of electroweak baryogenesis that does not make use of a new source of [ital CP] violation.
376 citations
TL;DR: In this paper, the mass of the lightest Higgs boson in the Minimal Supersymmetric Standard Model was derived in a model-independent way, including leading and next-to-leading order (two-loop) radiative corrections.
326 citations
Book•
23 Feb 1995
TL;DR: In this paper, the standard electroweak model, the weak neutral current, the measurement of electroweak parameters from deep inelastic neutrino scattering, F. Einsweiler, D. Treille future e+e-colliders at high energy and D. Burke.
Abstract: Part 1 The standard electroweak model: structure of the standard model, P. Langacker renormalization of the standard model, W. Hollik predictions for e+e- processes, W. Holik radiative corrections to neutral current processes, W. Marciano. Part 2 Precision tests at e+e-colliders: e+e- annihilation below the Z pole, D. Haidt and R. Marshall Z-pole experiments, D. Schaile polarization in e+e- annihilation, A. Blondel the LEP II program, D. Treille future e+e- colliders at high energy, D. Burke. Part 3 The weak neutral current: the measurement of electroweak parameters from deep inelastic neutrino scattering, F. Perrier elastic neutrino-nucleon scattering, A.K. Mann neutrino-electron scattering, J. Panman atomic parity violation experiments, C. Wieman the theory of atomic parity violation, J. Sapirstein charged lepton-hadron asymmetries in target experiments, P. Souder precision electroweak tests at HERA, H. Spiesberger. Part 4 The weak charged current: the unitarity of the Quark mixing matrix, A. Sirlin beta decay, right-handed currents and the search for new physics, J. Deutsch precision measurements in muon and tau decays, W. Fetscher and H.-J. Gerber muon decay and beta decay beyond the standard model, P. Herczeg. Part 5 Precision tests at hadron colliders, E. Einsweiler. Part 6 Implications of precision experiments: tests of the standard model and searches for new physics, P. Langacker exotic fermions, D. London. Part 7 The future, M Luo.
285 citations
TL;DR: In this article, the background-field Green functions are shown to possess very desirable theoretical properties and a consistent on-shell renormalization procedure retaining the full gauge symmetry is presented.
250 citations
TL;DR: In this article, the authors show that the asymmetric reheating can be related to a difference of the electroweak symmetry breaking scales in the two sectors, which is needed for a solution of the neutrino puzzles in this picture.
Abstract: The existence of a shadow world (or mirror universe) with matter and forces identical to that of the visible world but interacting with the latter only via gravity can be motivated by superstring theories as well as by recent attempts to understand the nature of a sterile neutrino needed if all known neutrino data are to be consistent with each other. A simple way to reconcile the constraints of big bang nucleosynthesis in such a theory is to postulate that the reheating temperature after inflation in the mirror universe is lower than that in the visible one. We have constructed explicit models that realize this proposal and have shown that the asymmetric reheating can be related to a difference of the electroweak symmetry breaking scales in the two sectors, which is needed for a solution of the neutrino puzzles in this picture. Cosmological implications of the mirror matter are also discussed.
201 citations
TL;DR: In this article, the Minimal Supersymmetric Standard Model with a gauged family-dependent U(1) was augmented with an extra chiral electroweak singlet field.
190 citations
TL;DR: In this article, the authors study the cosmology of the Supersymmetric Standard Model augmented by a gauge singlet to solve the μ-problem and describe the evolution of the domain walls which are created during electroweak symmetry breaking due to the discrete Z 3 symmetry in this model.
176 citations
TL;DR: In this article, the authors discuss radiative electroweak symmetry breaking with non-universal scalar masses at the GUT scale, and identify two classes of nonuniversalities which give solutions with A o ⋍ B o⋍ M 1 2 ⋈ O(M z ) and with μ ⪢ M Z or μ ⋌ O(m z ), respectively.
146 citations
TL;DR: The gauge hierarchy achieved by a fine-tuning in the superpotential would be violated in general due to the nonuniversal SUSY-breaking terms, but it is preserved for a certain class of the soft terms derived from a [ital hidden] ansatz.
Abstract: Supersymmetric grand unified theories with nonuniversal soft supersymmetry- (SUSY-) breaking terms are studied. By integrating out the superheavy fields at a unification scale, we compute their low-energy effective Lagrangian. We find new contributions to the scalar potential specific to the nonuniversal supersymmetry breaking. A D-term contribution to the scalar masses is one example. The gauge hierarchy achieved by a fine-tuning in the superpotential would be violated in general due to the nonuniversal SUSY-breaking terms. We show, however, it is preserved for a certain class of the soft terms derived from a hidden ansatz. We also discuss some phenomenological implications of the nonuniversal supersymmetry breaking, including predictions of the radiative electroweak symmetry-breaking scenario and of no-scale-type models.
144 citations
TL;DR: In this paper, a framework relying on both perturbative and non-perturbative lattice computations which will be able to reliably determine the parameters of the EW phase transition was discussed, and a motivation for the use of 3D effective theory in the lattice simulations, rather than the complete 4D one, was provided.
TL;DR: A new effect that produces baryons at a first order electroweak phase transition when there is a {ital CP}-violating field present on propagating bubble walls is described.
Abstract: We describe a new effect that produces baryons at a first order electroweak phase transition. It operates when there is a {ital CP}-violating field present on propagating bubble walls. The novel aspect is that it involves a purely classical force, which alters the motion of particles across the wall and through diffusion creates a chiral asymmetry in front of the wall. We develop a technique for computing the baryon asymmetry using the Boltzmann equation, and a fluid approximation which allows us to model strong scattering effects. The final formula for the baryon asymmetry has a remarkably simple form.
TL;DR: In this article, the finite temperature phase transition in the SU (2) Higgs model on the lattice was investigated and the phase transition was shown to be of first order and its strength is rapidly decreasing with increasing Higgs boson mass.
TL;DR: In this article, the two-loop electroweak contributions to the anomalous magnetic moment of the muon involving triangle fermionic loops of leptons and quarks were investigated.
TL;DR: In this paper, the production of the Standard Model Higgs boson in the four-fermion reaction e + e − → μ + μsu−b b is studied and the complete tree-level matrix element, including signal and background in the standard electroweak theory, is computed and initial state radiation is taken into account in the leading-log approximation.
TL;DR: In this article, the full set of weak-scale gauge and Yukawa threshold corrections in the minimal supersymmetric standard model, including all finite (non-logarithmic) corrections, were computed.
TL;DR: Upper bounds on superpartner masses in the minimal supersymmetric model are computed, and it is found that supersymmetry cannot provide a complete explanation of weak scale stability, if squarks and gluinos have masses beyond the physics reach of the CERN LHC.
Abstract: Superpartner masses cannot be arbitrarily heavy if supersymmetric extensions of the standard model explain the stability of the gauge hierarchy. This ancient and hallowed motivation for weak scale supersymmetry is often quoted, yet no reliable determination of this upper limit on superpartner masses exists. In this paper we compute upper bounds on superpartner masses in the minimal supersymmetric model, and we identify which values of the superpartner masses correspond to the most natural explanation of the hierarchy stability. We compare the most natural value of these masses and their upper limits to the physics reach of current and future colliders. As a result, we find that supersymmetry could explain weak scale stability naturally even if no superpartners are discovered at the CERN LEP II or the Fermilab Tevatron (even with the Main Injector upgrade). However, we find that supersymmetry cannot provide a complete explanation of weak scale stability, if squarks and gluinos have masses beyond the physics reach of the CERN LHC. Moreover, in the most natural scenarios, many sparticles, for example, charginos, squarks, and gluinos, lie within the physics reach of either LEP II or the Tevatron. Our analysis determines the most natural value of the chargino (squark) [(gluino)]more » mass consistent with current experimental constraints is {similar_to}50 (250) [(250)] GeV and the corresponding theoretical upper bound is {similar_to}250 (700) [(800)] GeV.« less
TL;DR: In this paper, the cross-section for W+W− → W− with arbitrarily polarized W bosons is calculated within the Electroweak Standard Model including the complete virtual and soft-photonic O (α) corrections.
TL;DR: In this paper, the authors explore the idea that the fundamental reason underlying the striking feature m b, m r ⪡ m t is that all of the elements of the down-quark and charged lepton effective Yukawa matrices actually arise from higher-dimension operators, suppressed by inverse powers of the Planck mass.
CERN1
TL;DR: In this article, the authors discussed the two-loop electroweak contributions to the anomalous magnetic moment of the muon involving triangle fermionic loops of leptons and quarks.
Abstract: We discuss, within the framework of the Standard Model, the calculation of the two-loop electroweak contributions to the anomalous magnetic moment of the muon involving triangle fermionic loops of leptons and quarks. Because of the large ratios of masses involved, these contributions are rather large. The result we obtain differs from a previous estimate reported in the literature. The discrepancy originates in the cancellation of anomalies in $SU(3)_c\times SU(2)_L\times U(1)_Y$, a cancellation that requires the consideration of both leptons {\it and} quarks within each generation and that had been previously overlooked.
TL;DR: In this article, the unification of gauge couplings within the framework of a wide class of realistic free-fermionic string models was discussed, including flipped SU(5), SO(6) × SO(4), and various SU(3) × SU(2) × U(1) models.
TL;DR: HECTOR as mentioned in this paper is a Fortran program for semi-analytical calculations of radiative QED, QCD, and electroweak corrections to the double-differential cross sections of NC and CC deep inelastic charged lepton proton (or lepton deuteron) scattering.
Abstract: A description of the Fortran program HECTOR for a variety of semi-analytical calculations of radiative QED, QCD, and electroweak corrections to the double-differential cross sections of NC and CC deep inelastic charged lepton proton (or lepton deuteron) scattering is presented. HECTOR originates from the substantially improved and extended earlier programs HELIOS and TERAD91. It is mainly intended for applications at HERA or LEPxLHC, but may be used also for muon scattering in fixed target experiments. The QED corrections may be calculated in different sets of variables: leptonic, hadronic, mixed, Jaquet-Blondel, double angle etc. Besides the leading logarithmic approximation up to order O(alpha^2), exact order O(alpha) corrections and inclusive soft photon exponentiation are taken into account. The photoproduction region is also covered.
TL;DR: In this article, the distributions of leptons from the decay of electroweak vector bosons produced in hadron collisions were studied using the Collins-Soper resummation formalism.
TL;DR: The Minimal Supersymmetric Standard Model (MSSM) as discussed by the authors is a GUT model with a successful prediction of many unrelated phenomena with a minimum number of parameters.
Abstract: The Minimal Supersymmetric Standard Model (MSSM) distinguishes itself from other GUT's by a successful prediction of many unrelated phenomena with a minimum number of parameters. Among them: a) Unification of the gauge couplings constants; b) Unification of the b-quark and τ-lepton masses; c) Proton stability; d) Electroweak symmetry breaking at a scale far below the unification scale and the corresponding relation between the gauge boson masses and the top quark mass. A combined fit of the free parameters in the MSSM to these low energy constraints shows that the MSSM model can satisfy these constraints simultaneously. From the fitted parameters the masses of the as yet unobserved superpartners of the SM particles are predicted, the top mass is constrained to a range between 140 and 200 GeV, and the second order QCD coupling constant is required to be between 0.108 and 0.132. The complete second order renormalization group equations for the gauge and Yukawa couplings are used and analytical solutions for the neutral gauge boson, the Higgs masses and the sparticle masses are derived, taking into account the one-loop corrections to the Higgs potential.
CERN1
TL;DR: In this paper, the precision electroweak data at LEP were used to place bounds on B-violating Yukawa couplings, two theoretically appealing examples being provided by R-parity violating supersymmetry and diquarks.
TL;DR: In this article, a large scale numerical simulation showed that the high temperature Chern-Simons number diffusion rate in the electroweak theory has a classical limit Γ = κ ( α w T ) 4, where α w is the weak fine structure constant.
TL;DR: In this article, the authors presented the QCD corrections to Higgs boson self-energies for an arbitrary momentum transfer and for different internal quark masses to treat the case of CP-even, CP-odd, and charged higgs bosons which appear in extensions of the standard model scalar sector.
Abstract: We present the QCD corrections to Higgs boson self-energies for an arbitrary momentum transfer and for different internal quark masses to treat the case of CP-even, CP-odd, and charged Higgs bosons which appear in extensions of the standard model scalar sector. Using Ward identities, we then relate these results obtained by directly evaluating the relevant two-loop Feynman diagrams to the known expressions for the electroweak vector boson vacuum polarization functions. Finally, we derive the exact analytical expressions for the QCD corrections to the decays of these Higgs particles into quark pairs in the general case, and reproduce in a completely independent way known results in some special cases.
TL;DR: In this paper, the authors review the status of and recent developments in dynamical electroweak symmetry breaking, concentrating on the ideas of technicolour and top quark condensates.
Abstract: We review the status of and recent developments in dynamical electroweak symmetry breaking, concentrating on the ideas of technicolour and top quark condensates. The emphasis is on the essential physical ideas and experimental implications rather than on detailed mathematical formalism. After a general overview of the subject, we give a first introduction to technicolour, and extended technicolour, illustrating the ideas with a simple (unrealistic) model. Then we review the progress that has been made with enhancing the technicolour condensate, using the Schwinger-Dyson gap equation. The discussion includes the so-called walking technicolour and strong extended technicolour approaches. We then turn to the experimental prospects of technicolour models, including longitudinal gauge boson scattering experiments at the LHC, the detection of pseudo-Goldstone bosons and the hints about electroweak symmetry breaking which comes from precision measurements at LEP. We also discuss a low-scale technicolour model, which has experimental signatures at LEP and the Tevatron. Finally we turn to the idea of the top quark condensate. After reviewing the basic ideas of this approach, we turn to some extensions of these ideas involving fourth-family condensates and the role of irrelevant operators.
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TL;DR: In this article, the neutral currents coupled to all neutral vector bosons present in the theory were studied and it was shown that there are no flavor changing neutral currents at tree level coupled with the lightest vector boson.
Abstract: Assuming the existence of right-handed neutrinos, we consider an electroweak model based on the gauge symmetry SU(4)L ⊗ U(1)N. We study the neutral currents coupled to all neutral vector bosons present in the theory. There are no flavor changing neutral currents at tree level, coupled with the lightest neutral vector boson.
TL;DR: In this paper, the authors present analytic results for the two-loop leading heavy top-quark contributions as required for precise predictions of electroweak observables, where the Higgs boson mass is kept arbitrary.
Abstract: We present analytic results for the two-loop leading heavy top-quark contributions as required for precise predictions of electroweak observables. The Higgs boson mass is kept arbitrary. We discuss a set of recurrence relations for diagrams with three masses at zero momentum, which allow one to reduce the calculation to a few master integrals. Simple analytic expressions are obtained for the \ensuremath{\rho} parameter and for the Zbb\ifmmode\bar\else\textasciimacron\fi{} vertex. Results are pesented for the on-shell and the MS\ifmmode\bar\else\textasciimacron\fi{} definition of the top quark mass. We explicitly discuss and verify the validity of Ward-Takahashi identities and check that the use of an anticommuting ${\ensuremath{\gamma}}_{5}$ preserves the latter.