Showing papers on "Elementary particle published in 1997"

Influence of strongly coupled, hidden scalars on Higgs signals

Abstract: To investigate the possible effects of a light hidden sector on Higgs boson detection, we discuss a model of scalar singlets coupled to the Standard Model. The model effectively makes the Higgs width a free parameter due to additional invisible decay modes. This width can become arbitrarily large. Theoretical and experimental bounds on model parameters are presented. It is shown, how Standard Model predictions change and that in the case of large coupling, Higgs signals will be diluted. We study, to which extent such a strongly coupled, hidden sector can be excluded by present and future Higgs search experiments.

Analysis of a Kπ-Scattering Phase Shift and Evidence for the κ(900) Meson

Abstract: Recently we have shown an evidence for existence of \sigma-particle in the previous works/ where the \pi\pi S-wave phase shift is reanalyzed, by introducing a repulsive background suggested by the chiral symmetry, and by applying a new method of Interfering Breit-Wigner Amplitudes. In this work we also show, reanalyzing the K\pi S-wave phase shift from a similar standpoint, an evidence for existence of \kappa(900), possibly to be a member of \sigma-nonet.

Heavy SUSY Higgs bosons at e+e− linear colliders

Abstract: The production mechanisms and decay modes of the heavy neutral and charged Higgs bosons in the Minimal Supersymmetric Standard Model are investigated at future e +e − colliders in the TeV energy regime. We generate supersymmetric particle spectra by requiring the MSSM Higgs potential to produce correct radiative electroweak symmetry breaking, and we assume a common scalar mass m0, gaugino mass m1/2 and trilinear coupling A, as well as gauge and Yukawa coupling unification at the Grand Unification scale. Particular emphasis is put on the low tan β solution in this scenario where decays of the Higgs bosons to Standard Model particles compete with decays to supersymmetric charginos/neutralinos as well as sfermions. In the high tan β case, the supersymmetric spectrum is either too heavy or the supersymmetric decay modes are suppressed, since the Higgs bosons decay almost exclusively into b and τ pairs. The main production mechanisms for the heavy Higgs particles are the associated AH production and H +H− pair production with cross sections of the order of a few fb.

HIGLU and HDECAY: Programs for Higgs boson production at the LHC and Higgs boson decay widths

Abstract: The total cross section for neutral Higgs boson production via the gluon fusion mechanism including NLO (two-loop) QCD corrections can be calculated numerically with the program HIGLU within the Standard Model (SM) as well as its minimal supersymmetric extension (MSSM). The program HDECAY determines the decay widths and branching ratios of the Higgs bosons within the SM and the MSSM, including the dominant higher-order corrections. The program is able to calculate the branching ratios of the MSSM Higgs bosons into standard and supersymmetric particles.

Constraints on the W R mass and CP violation in left-right models

Abstract: We update the constraints on the right-handed W{sub R} gauge boson mass, mixing angle {zeta} with the left-handed W{sub L} gauge boson, and other parameters in general left-right symmetric models with different mechanisms of CP violation. Constraints mostly independent of any assumption on the quark sector are obtained from a reanalysis of muon decay data. The best {chi}{sup 2} fit of the data gives g{sub R}/g{sub L}=0.94{plus_minus}0.09 for the ratio of right to left gauge couplings, with M{sub W{sub R}}{ge}485 GeV and {vert_bar}{zeta}{vert_bar}{le}0.0327. Fixing g{sub L}=g{sub R} (in particular for manifestly left-right symmetric models), we obtain M{sub W{sub R}}{approx_gt}549 GeV and {vert_bar}{zeta}{vert_bar}{approx_gt}0.0333. Estimates of the left-right hadronic matrix elements in the neutral kaon system and their uncertainties are revised using large N{sub c} and chiral perturbation theory arguments. With explicitly given assumptions on the long-distance ({Delta}S=1){sup 2} contributions to the K{sub L}-K{sub S} mass difference, lower bounds on M{sub W{sub R}} are obtained. With the same assumptions, one also gets strong upper bounds from the CP-violating parameter {epsilon}{sub K}, for most of the parameter space of left-right models where the right-handed third family does not contribute in CP-violating quantities. For manifestly left-right symmetric models the lower bound obtained is M{submore » W{sub R}}{approx_gt}(1.6{sub {minus}0.7}{sup +1.2}) TeV. {copyright} {ital 1997} {ital The American Physical Society}« less

The search for elementary particles with fractional electric charge and the philosophy of speculative experiments

Abstract: All known elementary particles that can be isolated as individual particles have an electric charge that is equal in magnitude to the electron’s charge, q=1.6×10−19 C, or is zero. This includes the muon and tau charged leptons, the neutrinos, the photon, the nucleons, and the mesons. There have been many searches without confirmed success for isolated particles with fractional electric charge such as ±q/3, or ±q/2, or ±3q/2. The theory of the physics of elementary particles does not require the existence of such particles. In particular, current theory holds that quarks, whose charge is ±(1/3)q or ±2/3q, cannot be isolated. Despite past failures and current theory, we have been engaged for the past few years in a new search for isolated elementary particles with fractional electric charge. In the course of this paper we discuss models for fractional charge particles, summarize previous searches, and describe our experimental method; and because this is speculative research we will also present our thought...

Higgs boson decay to top quarks at O({alpha}{sub s}{sup 2})

Abstract: Three-loop corrections to the scalar and pseudoscalar current correlator are calculated. By applying the large momentum, expansion mass terms up to order (m{sup 2}/q{sup 2}){sup 4} are evaluated analytically. As an application O({alpha}{sub s}{sup 2}) corrections to the decay of a scalar and pseudoscalar Higgs boson into top quarks are considered. It is shown that for a Higgs mass not far above the t{bar t} threshold these higher order mass corrections are necessary to get reliable results. {copyright} {ital 1997} {ital The American Physical Society}

The structure of cosmic string wakes

Abstract: The clustering of baryons and cold dark matter induced by a single moving string is analyzed numerically, making use of the new three-dimensional Eulerian cosmological hydrocode of Sornborger et al., which uses the piecewise parabolic method to track the baryons and the particle-in-cell method to evolve the dark matter particles. A long straight string moving with a speed comparable to c induces a planar overdensity (a "wake"). Since the initial perturbation is a velocity kick toward the plane behind the string and there is no initial Newtonian gravitational line source, the baryons are trapped in the center of the wake, leading to an enhanced baryon to dark matter ratio. The cold coherent flow leads to very low postshock temperatures of the baryonic fluid. In contrast, long strings with small-scale structure (which can be described by adding a Newtonian gravitational line source) move slowly and form filamentary objects. The large central pressure due to the gravitational potential causes the baryons to be expelled from the central regions and leads to a relative deficit in the baryon to dark matter ratio. In this case, the velocity of the baryons is larger, leading to high postshock temperatures.

Interaction of particles and radiation with matter

Abstract: Introduction: Fundamentals of the Structure of Matter.- A. Elementary Particles.- B. The Atomic Nucleus.- C. Atoms and Molecules.- I. Interaction of Charged Particles with Matter.- First Lecture.- 1.1 Ionization Stopping and Multiple Scattering of Fast Heavy Particles in Disordered Media: Relationship Between Parameters Characterizing the Passage of Particles Through Matter and Characteristics of Elementary Processes.- 1.2 The Classical Theory of Ionization Stopping.- Second Lecture.- 2.1 Quantum Theory of Ionization Stopping of Fast Charged Particles.- 2.2 Stopping Times and Path Ranges of Particles in Media.- 2.3 Calculation of the Average Multiple-Scattering Angle.- 2.4 Straggling: Fluctuations of Ionization Losses.- Third Lecture.- 3.1 "Dielectric Theory" of Ionization Stopping.- 3.2 Application of the "Dielectric Theory": Ionization Stopping in a Rarefied Gas.- 3.3 Stopping of a Charged Particle in a Degenerate Electron Gas.- 3.4 Local Density Approximation.- 3.5 Relativistic Effects: The Bethe-Bloch Formula.- Fourth Lecture.- 4.1 Ionization Stopping of Slow Particles.- 4.2 Bragg's Composition Law.- 4.3 The Stopping Power of a Medium for Particles and Antiparticles: The Z3 Correction to the Bethe-Bloch Formula.- 4.4 Passage of Multiple-Charged Ions Through Matter.- 4.5 The Passage of Electrons Through Matter.- Fifth Lecture.- 5.1 Channelling.- 5.2 The Shadow Effect (Blocking).- Sixth Lecture.- 6.1 Interaction of Molecular Ions with Matter.- 6.2 Application of the Method of Computer Simulation.- II. Interaction of Electromagnetic Radiation with Matter.- Seventh Lecture.- 7.1 Passage of ? Radiation Through Matter.- 7.2 Interaction of ? Quanta with the Atomic Nuclei of Matter. The Mossbauer Effect.- Eighth Lecture.- 8.1 Rotation of the Plane of Polarization of Light as an Effect Due to Parity Violation in Atoms.- 8.2 Experimental Observation of Parity Violation in Atoms.- Ninth Lecture.- 9.1 Electromagnetic Radiation Caused by the Passage of Particles Through Matter: Direct Processes.- 9.2 Characteristic Radiation of the Atoms of a Medium Due to the Interaction of Particles with Matter.- 9.3 Angular Anisotropy of the Characteristic Radiation. The Alignment Phenomenon of Atoms in a Medium.- 9.4 Electromagnetic Radiation in Charged Particle Channelling.- III. Interaction of Neutrons with Matter.- Tenth Lecture.- 10.1 Elementary Theory of the Slowing Down of Neutrons.- 10.2 The Mean Stopping Time of a Neutron: The Stopping Path.- Eleventh Lecture.- 11.1 Motion of Neutrons Upon Thermalization: The Diffusion Coefficient.- 11.2 The Equation of Diffusion: The Mean Lifetime of the Neutron.- 11.3 Typical Problems of Thermal Neutron Diffusion Theory.- 11.3.1A Stationary Point Source in an Infinite Medium.- 11.3.2 Boundary Conditions for Neutrons Passing from a Medium to Vacuum.- 11.3.3 Diffusion of Thermal Neutrons from a Point-Like Pulsed Source.- Twelfth Lecture.- 12.1 Neutron Diffraction in a Crystal.- 12.2 Coherent and Incoherent Neutron Scattering.- 12.3 The Influence of Thermal Oscillations of the Lattice: The Phenomenon of Inelastic Diffraction.- 12.4 Neutron Scattering by Polycrystals.- IV. Mesoatomic and Mesomolecular Processes.- Thirteenth Lecture.- 13.1 Mesoatoms and Their Properties.- 13.2 Cascade of Electromagnetic Transitions in Mesoatoms: Influence of the Medium on a Mesoatomic Cascade.- 13.3 Methods Involving Pions and Muons in Chemical Studies.- 13.3.1 Analysis of the Composition and Structure of Matter Based on Mesonic X-Rays.- 13.3.2 Charge Exchange of ? Mesons on Hydrogen Nuclei.- 13.3.3 Polarization and Depolarization of Muons in Muonic Atoms.- 13.3.4 Muonium.- Fourteenth Lecture.- 14.1 The Formation of Mesomolecules.- 14.2 Muonic Catalysis of Nuclear Fusion.- References to Figures and Tables.

From Sets to Quarks

Abstract: From sets and simple operations on sets, a Feynman Checkerboard physics model is constructed that allows computation of force strength constants and constituent mass ratios of elementary particles, with a Lagrangian structure that gives a Higgs scalar particle mass of about 146 GeV and a Higgs scalar field vacuum expectation value of about 252 GeV, giving a tree level constituent Truth Quark (top quark) mass of roughly 130 GeV, which is (in my opinion) supported by dileptonic events and some semileptonic events. See this http URL and this http URL Chapter 1 - Introduction. Chapter 2 - From Sets to Clifford Algebras. Chapter 3 - Octonions and E8 lattices. Chapter 4 - E8 spacetime and particles. Chapter 5 - HyperDiamond Lattices. Chapter 6 - Internal Symmetry Space. Chapter 7 - Feynman Checkerboards. Chapter 8 - Charge = Amplitude to Emit Gauge Boson. Chapter 9 - Mass = Amplitude to Change Direction. Chapter 10 - Protons, Pions, and Physical Gravitons.

Limitations of a Standard Model Higgs Boson

Abstract: This contribution reviews the latest results of the perturbative calculations of heavy-Higgs amplitudes. A comparison of perturbative results with nonperturbative lattice calculations is made, and the theoretical uncertainties of the lower and upper bound on the Standard Model Higgs mass are presented.

Neutrino scattering in a newly born neutron star

Abstract: We calculate neutrino cross sections from neutral-current reactions in the dense matter encountered in the evolution of a newly born neutron star. Effects of composition and of strong interactions in the deleptonization and cooling phases of the evolution are studied. The influence of the possible presence of strangeness-rich hyperons on the neutrino scattering cross sections is explored. Due to the large vector couplings of the Σ- and Ξ-, |CV| ~ 2, these particles, if present in protoneutron star matter, give significant contributions to neutrino scattering. In the deleptonization phase, the presence of strangeness leads to large neutrino energies, which results in large enhancements in the cross sections compared to those in matter with nucleons only. In the cooling phase, in which matter is nearly neutrino-free, the response of the Σ- hyperons to thermal neutrinos is the most significant. Neutrinos couple relatively weakly to the Λ hyperons and, hence, their contributions are significant only at high density.

Highly nonideal classical thermal plasmas: Experimental study of ordered macroparticle structures

Abstract: The formation of spatially ordered CeO2 particle structures in a thermal plasma at atmospheric pressure and temperatures of 1700–2200 K is studied. The spatial structure of the particles in the plasma is analyzed using laser time-of-flight counting of individual particles. Probe and optical diagnostics are used to determine the parameters of the thermal plasma. The CeO2 particles were positively charged (about 103 electronic charges). The resulting Coulomb interaction parameter for the particles is γp>120, which corresponds to a highly nonideal plasma.

The new limits of the neutrinoless $(\mu^-,e^-)$ conversion branching ratio

Abstract: The nuclear physics dependence of the exotic $(\mu^-,e^-)$ conversion branching ratio $R_{\mu e^-}$ for the experimentally most interesting nuclei $^{208}Pb$ and $^{48}Ti$, is investigated in various nuclear models. The results thus obtained are combined with the new experimental limits extracted at PSI for these nuclei to put bounds on the elementary particle parameters entering $R_{\mu e^-}$ such as intermediate neutrino masses and mixing angles as well as relevant parameters of intermediate supersymmetric particles (masses and mixing of s-fermions and neutralinos).

Does antimatter emit a new light

Abstract: We identify a number of problematic aspects of current classical and quantum theories of antimatter; we introduce a new mathematical formalism which is an antiautomorphic image of that of matter equivalent to charge conjugation at the operator level, but applicable from Newton's equations to quantum mechanics; we show that the emerging new theory of antimatter recovers known experimental data on electroweak interactions; we finally identity the following predictions of the theory: 1) reversal in the field of matter of the gravitational curvature (antigravity) for stable antiparticles and their bound states, such as the anti-hydrogen atom; 2) conventional (attractive) gravity for a bound state of an elementary particle and its antiparticle, such as the positronium; and 3) prediction that the anti- hydrogen atom emits a new photon which coincides with the conventional photon for all electroweak interactions but experiences repulsion in the gravitational field of matter

The new limits of the neutrinoless , conversion branching ratio

Abstract: The nuclear physics dependence of the exotic conversion branching ratio for the experimentally most interesting nuclei, and , is investigated in various nuclear models. The results thus obtained are combined with the new experimental limits extracted at PSI for these nuclei, to put bounds on the elementary particle parameters entering such as intermediate neutrino masses and mixing angles as well as relevant parameters of intermediate supersymmetric particles (masses and mixing of s-fermions and neutralinos).

The first elementary particle

Abstract: The electron is 100 years old this year. Of all the elementary particles, it is by far the most familiar, useful and venerable. But is it elementary? And what other particles are elementary?

The masses of elementary particles

Abstract: The calculation for the masses of elementary particles is based on the ten dimensional superstring. A Kaluza--Klein substructure is proposed for the six extra spatial dimensions in the ten-dimensional superstring. The periodic table of elementary particles can be constructed from the Kaluza--Klein substructure. All leptons, quarks, and gauge bosons can be placed in the periodic table. The masses of elementary particles can be generated using only four known constants: the number of the extra spatial dimensions in the ten-dimensional superstring, the mass of the electron, the mass of Z0, and αe. The calculated masses derived from the periodic table are in good agreement with the observed values. The calculated mass (176.6 GeV) of the top quark is in excellent agreement with the observed mass (176 GeV). The periodic table also provides an explanation for why the cross section for jet transverse energy, >200 GeV, is greater than the perturbative QCD prediction. The periodic table based on the ten-dimensional superstring provides the most comprehensive explanation and calculation for the properties and the masses of all elementary particles.

Nuclear Spin Responses for Neutrinos in Astroparticle Physics

Abstract: Nuclear spin responses are of vital importance for studies of neutrinos, weakly interacting particles and of weak interactions in nuclei. The physics objectives are concerned with lepton nuclear physics within and beyond the standard theory. Here nuclei, which consist of elementary particles in good quantum (eigen) states, are used as excellent micro-laboratories for studying fundamental particles and interactions. Subjects discussed include neutrinos(ν) and weak interactions, weakly interacting massive particles as candidates for dark matters (DM), and other related problems. Experimental studies of them are made by investigating ultra rare nuclear processes at low background underground laboratories. Nuclear responses relevant to electroweak processes, neutrinos, and weakly interacting massive particles are discussed. Nuclear spin isospin responses associated with axial charged weak currents are investigated by using charge-exchange spin flip nuclear reactions at the RCNP ring cyclotron laboratory.

Electron dipole moments

Abstract: It is now one hundred years since J J Thomson showed that cathode rays are composed of electrons, the lightest of the known charged particles. Yet a century later, after many spectacular advances in particle physics, it is curious that the two most elementary properties of the electron, its mass and charge, remain a deep mystery. In the modern theory of elementary particles, the Standard Model, the mass and charge of the electron cannot be calculated from first principles. Rather, the values measured in experiments are inserted into the theory "by hand". Presumably at some time in the future these values will be understood from first principles, but at present no one knows why the charge and mass of the electron, or indeed any other elementary particle, have those particular values.

Is the Planck momentum attainable

Abstract: We present evidence that an interplay of the laws of microphysics and cosmology renders the Planck momentum unattainable by an elementary particle. Several categories of accelerators are analyzed and shown to fail.