Showing papers on "Elementary particle published in 1989"
TL;DR: In this paper, the authors survey the low-energy phenomenological implications of superstring-inspired E 6 models and present experimental limits on these particles from both accelerator and non-accelerator data.
827 citations
TL;DR: An extension of the minimal model to include a singlet Higgs field whose vacuum expectation value determines the mixing is explored, and the possible production mechanisms and phenomenological signatures of the different Higgs bosons at these machines are analyzed.
Abstract: The minimal supersymmetric standard model contains two Higgs doublets which must mix via a mass parameter whose magnitude remains to be explained. We explore an extension of the minimal model to include a singlet Higgs field whose vacuum expectation value determines the mixing. We study the spectrum and couplings of Higgs bosons in this extended model and compare them with those in the minimal model. We examine a number of limiting cases analytically and also make numerical studies of the extended model both with and without constraints from the renormalization-group analysis of a parent superstring-inspired grand-unified-theory model. We establish the conditions for there to be a charged Higgs boson lighter than the ${W}^{\ifmmode\pm\else\textpm\fi{}}$ and the circumstances under which there is no light neutral Higgs boson. With a particularly simple set of boundary conditions at the unification scale, the renormalization-group equations imply that one or more Higgs bosons are light enough to be found at the CERN LEP or SLAC Linear Collider and that many supersymmetric particles should be accessible to these accelerators and the Fermilab Tevatron; relatively few would require the Superconducting Super Collider, Large Hadron Collider, or a TeV-scale ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ collider for discovery. Finally, we analyze the possible production mechanisms and phenomenological signatures of the different Higgs bosons at these machines.
564 citations
TL;DR: It is argued that in the high-energy electron end-point region in B decay the usual inclusive ("quark decay") calculations are unjustified and must be replaced by explicit sums over decays of the original meson into low-mass exclusive hadronic final states.
Abstract: We predict the matrix elements and resulting electron spectra for semileptonic meson decays using the quark potential model. Particular attention is paid to the high-energy electron end-point region in B decay since it is crucial to a determination of the b→u weak mixing angle. It is argued that in this region the usual inclusive ("quark decay") calculations are unjustified and must be replaced by explicit sums over decays of the original meson into low-mass exclusive hadronic final states.
520 citations
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TL;DR: The mass of the elementary particles is the central problem of modern physics, and is intimately connected with other fundamental problems such as the origin of CP violation, the mystery of the energy scales that determine the properties of the weak and gravitational interactions, the compositeness of particles, supersymmetry theory, and properties of not yet discovered Higgs bosons as mentioned in this paper.
Abstract: Mass is one of the most fundamental concepts of physics. Understanding and calculating the masses of the elementary particles is the central problem of modern physics, and is intimately connected with other fundamental problems such as the origin of CP violation, the mystery of the energy scales that determine the properties of the weak and gravitational interactions, the compositeness of particles, supersymmetry theory and the properties of the not‐yet‐discovered Higgs bosons.
241 citations
TL;DR: It is shown that generically cosmic strings will interact with matter via their pure gauge potential, and the cross section is purely geometrical, and does not vanish in the limit of zero string size.
Abstract: It is shown that generically cosmic strings will interact with matter via their pure gauge potential. The cross section is purely geometrical, and does not vanish in the limit of zero string size. The mechanism is the Aharonov-Bohm effect, which is already known to cause scattering of charged particles off an infinitesimally thin solenoid. A related mechanism for particle production is also discussed.
238 citations
TL;DR: In this article, a search for light Higgs bosons has been performed in an electron beam-dump experiment and no positive signal is observed which allows us to reject at 90% CL the existence of a standard Higgs in the range from 1.2 to 52 MeV.
227 citations
TL;DR: A new lower bound on the {ital W}{sub {ital R}} mass, related to the strength of these lepton-lepton couplings, is derived as a result of the constraints obtained from low-energy experiments on a doubly charged Higgs doublet and a very light neutral Higgs triplet.
Abstract: In the context of minimal left-right-symmetric extensions of the standard $\mathrm{SU}{(2)}_{L}\ifmmode\times\else\texttimes\fi{}\mathrm{U}(1)$ model, four possible scenarios emerge depending upon the number of neutral Higgs fields that acquire nonzero vacuum expectation values. We examine these four scenarios in the case of a simple form for the scalar potential of the model. We find that by combining the minimization conditions appropriate to each of these scenarios with constraints coming from ${K}_{L}\ensuremath{-}{K}_{S}$ mixing and the absence of flavor-changing neutral currents, two of the scenarios are ruled out. For the allowed scenarios rather definitive consequences for the Higgs sector can be obtained. For instance, several of the scalar bosons are forced to be very heavy by flavor-changing neutral-current constraints. Aside from the Higgs boson which plays the role of the standard-model Higgs fields, the three left-handed triplet members are most likely to be light. Indeed, in one of the vacuum-expectation-value scenarios they are forced to be light (the neutral member being massless at the tree level). We catalogue the constraints from low-energy experiments on a doubly charged Higgs triplet and a very light neutral Higgs triplet, when these couple to two leptons (as in the left-right model). Many of the constraints we obtain are new. A new lower bound on the ${W}_{R}$ mass, related to the strength of these lepton-lepton couplings, is derived. The cross sections for these bosons are large out to masses of order several TeV and signatures for their decay are striking and essentially background-free.
178 citations
TL;DR: In this paper, a framework for deep inelastic scattering with bound state properties in accordance with a QCD force field acting like a vortex line in a colour superconducting vacuum is presented.
Abstract: We present a framework for deep inelastic scattering, with bound state properties in accordance with a QCD force field acting like a vortex line in a colour superconducting vacuum, which implies some simple coherence effects. Within this scheme one may describe the results of present energies very well, but one obtains an appreciable depletion of gluon radiation in the HERA energy regime.
169 citations
TL;DR: In this paper, a three-body Faddeev-type formulation of baryons, as qqq colour-singlet states bound by gluon exchange, which is covariant, has dynamically hidden chiral symmetry and incorporates the colour dynamics was derived.
Abstract: From QCD we derive a three-body Faddeev-type formulation of baryons, as qqq colour-singlet states bound by gluon exchange, which is covariant, has dynamically hidden chiral symmetry and incorporates the colour dynamics. The formulation exploits the dynamical role of colour "3 diquark substructure in baryons to simplify computations. For non-zero current quark masses the jP = ~ + and ~ - baryon octet mass formulae are shown to satisfy the Gell-Mann-Okubo and the Coleman-Glashow multiplet mass relationships.
146 citations
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TL;DR: It is found that for an axion mass of greater than approx.10/sup -3/ eV, axion emission shortens the duration of the expected neutrino burst so significantly that it would be inconsistent with the neutrinos observations made by the Kamiokande II and Irvine-Michigan-Brookhaven detectors.
Abstract: We consider the effect of free-streaming axion emission on numerical models for the cooling of the newly born neutron star associated with SN 1987A. We find that for an axion mass of greater than \ensuremath{\sim}${10}^{\mathrm{\ensuremath{-}}3}$ eV, axion emission shortens the duration of the expected neutrino burst so significantly that it would be inconsistent with the neutrino observations made by the Kamiokande II and Irvine-Michigan-Brookhaven detectors. However, we have not investigated the possibility that axion trapping (which should occur for masses \ensuremath{\ge}0.02 eV) sufficiently reduces axion emission so that axion masses greater than \ensuremath{\sim}2 eV would be consistent with the neutrino observations.
140 citations
TL;DR: In this paper, a general form of non-unitary modification to the hamiltonian evolution equation caused by wormholes interacting with a microscopic system is derived, which suppresses elements of the density matrix which are off-diagonal in the configuration space representation, thus causing the wave function to collapse.
TL;DR: It is shown that Higgs bosons which have an enhanced coupling to bottom quarks may be predominantly produced via bottom-quark fusion through the supersymmetric two-Higgs-doublet model.
Abstract: We study the production of Higgs bosons from heavy-quark fusion at future hadron colliders. We use a heavy-quark distribution function to combine the processes QQ\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}H and gQ\ensuremath{\rightarrow}HQ with the process gg\ensuremath{\rightarrow}QQ\ifmmode\bar\else\textasciimacron\fi{}H to obtain a cross section in which potentially large logarithms, of order ln(${m}_{H}$/${m}_{Q}$), are summed to all orders in the strong coupling. We show that Higgs bosons which have an enhanced coupling to bottom quarks may be predominantly produced via bottom-quark fusion. We concentrate on the supersymmetric two-Higgs-doublet model, in which this enhancement occurs naturally.
TL;DR: In this article, a relativistic particle with rigidity whose action A =−α∫ kds depends on the curvature of particle world trajectory k, is studied, and the classical motion of the particle is shown to go along a helical line at superrelativistic velocity and its translational motion along the momentum direction at the velocity of light (c).
Abstract: The model of relativistic particle with rigidity whose action A=−α∫ kds depends on the curvature of particle world trajectory k, is studied. The classical motion of the particle is shown to go along a helical line at superrelativistic velocity and its translational motion along the momentum direction—at the velocity of light (c). After quantization, the parameter a becomes integer, α=n, n>0. The quantum states of the system are massless states of helicities λ=n and λ=−n in which the evolution of gauge-invariant coordinate occurs at velocity c.
TL;DR: A renormalization-group-improved perturbative unitarity bound for elastic scattering amplitudes is proposed, which leads to upper bounds on the Higgs boson and top-quark masses as a function of the energy at which perturbation unitarity is violated and new physics enters.
Abstract: A renormalization-group-improved perturbative unitarity bound for elastic scattering amplitudes is proposed. This prescription leads to upper bounds on the Higgs boson and top-quark masses as a function of the energy at which perturbative unitarity is violated and new physics enters. Upper bounds on the scale of new physics in models with no Higgs boson are also discussed.
TL;DR: The expression for the plasmon{r arrow}{nu}{bar {nu}} decay rate is rederived and the dispersion relation of a massless neutrino propagating in matter in the presence of an external magnetic field is determined.
Abstract: Using covariant methods we calculate the neutrino electromagnetic vertex in a gas of electrons to lowest order in a loop expansion and to the lowest order in $\frac{1}{{M}_{W}^{2}}$. The new induced terms, while they are chirality preserving, yield additional contributions to the dipole moments in the nonrelativistic limit. These are identical for particles and antiparticles and so need not vanish for Majorana neutrinos. As applications of our formulas, the expression for the $\mathrm{plasmon}\ensuremath{\rightarrow}\ensuremath{
u}\overline{\ensuremath{
u}}$ decay rate is rederived and the dispersion relation of a massless neutrino propagating in matter in the presence of an external magnetic field is determined. The possible implications of these effects are considered.
TL;DR: This work uses measured nuclear magnetic moments together with some very general assumptions about nuclear wave functions to estimate the spin-dependent elastic cross sections of supersymmetric dark-matter particles on a variety of nuclei.
Abstract: We use measured nuclear magnetic moments together with some very general assumptions about nuclear wave functions to estimate the spin-dependent elastic cross sections of supersymmetric dark-matter particles on a variety of nuclei. Our cross sections are nearly always smaller than the corresponding single-particle estimates. In light nuclei with mirror partners, we make use of β-decay ft values in addition to magnetic moments and obtain even more accurate results.
TL;DR: In this paper, the area of the parameter space that gives rise to a massive, stable neutralino χ, with a cosmologically significant relic density, is described, and the effect of the lightest Higgs exchange on the elastic neutralino-nucleus cross section is shown.
TL;DR: A simple extension of the standard model is proposed by adding an SU(2)/sub /ital H// horizontal gauge symmetry in the leptonic sector, which leads to a large transition magnetic moment of the electron neutrino while keeping the neutrinos mass naturally small.
Abstract: We propose a simple extension of the standard model by adding an SU(2)/sub /ital H// horizontal gauge symmetry in the leptonic sector, which leads to a large transition magnetic moment of the electron neutrino while keeping the neutrino mass naturally small. This model can provide a solution, to the solar neutrino puzzle while at the same time avoiding the SN 1987A bound on the neutrino magnetic moment.
TL;DR: An extensive study of production and decay properties of charged and neutral IVB at the CERN proton-antiproton collider is presented in this article, based on all the available data from the UA1 experiment from the running periods 1982-1985.
Abstract: An extensive study of production and decay properties of charged and neutral Intermediate Vector Bosons (IVB) at the CERN proton-antiproton collider is presented. Intermediate Vector Bosons were detected in the electron, muon, and tau decay modes at centre-of-mass energies of 0.546 and 0.630 TeV. This paper is a summary, based on all the available data from the UA1 experiment from the running periods 1982–1985. Results are presented and compared with expectations of the Standard Eletroweak Model and QCD-improved Drell-Yan annihilation processes. The general conclusion is that there is an excellent agreement between the predictions of the Standard Model and our measurements.
TL;DR: In this paper, the authors determined the diquark decay constant from consistency conditions with QCD sum rules and showed the importance of the strong quark-quark interaction for weak decays at low energies.
Abstract: We determine the “diquark decay constant” from consistency conditions with QCD sum rules. A large numerical value is obtained. The implications are discussed and the diquark picture is applied to weak baryon decays. The results show the importance of the strong quark-quark interaction for weak decays at low energies.
TL;DR: An electroweak theory in which left-handed quarks and leptons transform as doublets under separate SU(2) gauge groups is presented, which predicts small deviations in the properties of the /ital Z/ which will be visible at the SLAC Linear Collider and the CERN collider LEP.
Abstract: We present an electroweak theory in which left-handed quarks and leptons transform as doublets under separate SU(2) gauge groups. Spontaneous symmetry breakdown results in two charged and two neutral massive vector bosons. The lightest charged and neutral gauge bosons behave like the /ital W/ and /ital Z/ of the standard SU(2)/times/U(1) electroweak model. The heavier /ital W/ and /ital Z/, which can be as light as several hundred GeV, couple primarily to quarks. Our theory predicts small deviations in the properties of the /ital Z/ which will be visible at the SLAC Linear Collider and the CERN collider LEP.
TL;DR: A wider framework involving the existence of generations with exotic SU(2){sub {ital L}}{direct product}U(1){ sub {ital Y}} quantum numbers is considered, which allows us to derive a spectrum of fermions which contain the known quarks and leptons.
Abstract: A possible extension of the standard model can be defined by gauging the global baryon- and lepton-number U(1) symmetries. Gauging baryon and lepton numbers provides a natural framework for the seesaw mechanism in the lepton sector, and the Peccei-Quinn mechanism in the quark sector. Another consequence of this extension is that the usual three generations of fermions are not anomaly-free. However, we consider a wider framework involving the existence of generations with exotic SU(2){sub {ital L}}{direct product}U(1){sub {ital Y}} quantum numbers. This allows us to derive'' a spectrum of fermions which contain the known quarks and leptons.
TL;DR: It is demonstrated that the basic tree-level sum rules for Higgs-boson masses receive very small corrections even when the scale of the supersymmetry-breaking mass parameters describing the latter sector are very large.
Abstract: We compute the renormalization of the Higgs-boson masses of the minimal supersymmetric extension of the standard model as a function of the scale of mass breaking between gauge-Higgs bosons and their supersymmetric gaugino-Higgsino partners. We demonstrate that the basic tree-level sum rules for Higgs-boson masses receive very small corrections even when the scale of the supersymmetry-breaking mass parameters describing the latter sector are very large. We show analytically that the mass sum rules are screened against large effects from large mass splitting between the two sectors.
TL;DR: A model for a relativistic many-body system at finite temperature in the framework of thermo field dynamics, which is a real-time formalism of finite-temperature field theory, which contains the scalar and the vector mesons as well as the Dirac nucleon.
Abstract: We propose a model for a relativistic many-body system at finite temperature in the framework of thermo field dynamics, which is a real-time formalism of finite-temperature field theory. Our model contains the scalar (\ensuremath{\sigma}) and the vector (\ensuremath{\omega}) mesons as well as the Dirac nucleon. The full propagator and self-energy for each particle are presented in terms of spectral representations. The Feynman rules for a perturbation expansion are shown. They are applied to the study of collective modes in hot and dense matter within the random-phase approximation. The dispersion relations of the longitudinal and transverse collective modes in the meson branch are calculated. We also estimate the effective meson mass which is defined as the energy needed to create one meson at rest in extreme matter. The effects of vacuum fluctuations are also examined. They contribute a fair amount to the collective modes through the effective nucleon mass.
TL;DR: The most general expression for the vacuum-polarization tensor is written down that is consistent with gauge and Lorentz invariance in four dimensions and contains a term which signals parity and CP violation either in the Lagrangian, or in the background, or both.
Abstract: For the propagation of electromagnetic fields within a medium (e.g., a plasma or a heat bath at finite temperature), we write down the most general expression for the vacuum-polarization tensor that is consistent with gauge and Lorentz invariance in four dimensions. The expression contains a term which signals parity and CP violation either in the Lagrangian, or in the background, or both. The effect of this term is to split the otherwise degenerate transverse degrees of polarization of the photon. The physical implications of this term are discussed.
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01 Jan 1989TL;DR: The atom completed and a new particle the muon and the pion strangeness antibaryons the resonances weak interactions the neutral kaon system the structure of the nucleon the J/y, the t, and charm quarks, gluons and jets the fifth quirk from neutral currents to weak vector bosons.
Abstract: The atom completed and a new particle the muon and the pion strangeness antibaryons the resonances weak interactions the neutral kaon system the structure of the nucleon the J/y, the t, and charm quarks, gluons and jets the fifth quirk from neutral currents to weak vector bosons.
TL;DR: Perturbative QCD and a truncated meson theory describe the high- and low-photon-loop-momentum contributions, respectively, and the matching between these complementary pictures for strong interactions is discussed.
Abstract: We estimate the π+-π0 electromagnetic mass difference within the 1/N expansion approach to hadronic matrix elements. Perturbative QCD and a truncated meson theory describe the high- and low-photon-loop-momentum contributions, respectively. The matching between these complementary pictures for strong interactions is discussed.
TL;DR: In this article, a left-right symmetric model was presented in which small and finite Dirac neutrino masses are generated as two-loop radiative corrections. But the model also features a generalized seesaw mechanism for the charged fermions which is achieved by the inclusion of heavy charged singlet fermion.
Abstract: We present a left-right symmetric model in which small and finite Dirac neutrino masses are generated as two-loop radiative corrections. Typical masses of the order 10−2eV, 1 eV and 102eV are obtained for νe, νμ and ντ, respectively. The model also features a generalized seesaw mechanism for the charged fermions which is achieved by the inclusion of heavy charged singlet fermions.
TL;DR: A screening theorem is proved that, as the Higgs-boson mass becomes large, the leading radiative corrections to any loop order are not measurable, thereby generalizing previous results of explicit calculations of one and two loops.
Abstract: We study the effects of a heavy Higgs boson on low-energy (<1 TeV) observables in the standard model. We prove a screening theorem that, as the Higgs-boson mass becomes large, the leading radiative corrections to any loop order are not measurable, thereby generalizing previous results of explicit calculations of one and two loops. More importantly, the reasons behind such an effect are identified and discussed in detail.
TL;DR: This analysis shows that, depending upon the nucleus, the single-particle estimate of the figure of merit as defined by Ellis and Flores must be corrected by a factor which may be as large as an order of magnitude.
Abstract: Using the nuclear shell model we calculate the correction factor to the single-particle estimate of the spin-dependent elastic cross section on nuclei of dark matter. Our analysis shows that, depending upon the nucleus, the single-particle estimate of the figure of merit as defined by Ellis and Flores must be corrected by a factor which may be as large as an order of magnitude.