Showing papers on "Elementary particle published in 1983"

Molecular Light Scattering and Optical Activity

Abstract: Ranging from the physics of elementary particles to the structure of viruses, the subject matter of this book stresses the importance of optical activity and chirality in modern science and will be of interest to a wide range of scientists. Using classical and quantum methods with a strong emphasis on symmetry principles, the volume develops the theory of varied optical activity and related phenomena from the perspective of molecular scattering of polarized light. First Edition Hb (1983): 0-521-24602-4

New Tests for Quark and Lepton Substructure

Abstract: If quarks and leptons are composite at the energy scale $\ensuremath{\Lambda}$, the strong forces binding their constituents induce flavor-diagonal contact interactions, which have significant effects at reaction energies well below $\ensuremath{\Lambda}$. Consideration of their effect on Bhabha scattering produces a new, stronger bound on the scale of electron compositeness: $\ensuremath{\Lambda}g750$ GeV. Collider experiments now being planned will be sensitive to $\ensuremath{\Lambda}\ensuremath{\sim}1\ensuremath{-}5$ TeV for both electrons and light quarks.

How to Get an Upper Bound on the Higgs Mass

Abstract: In view of the almost established triviality of ϕ 4 in four dimensions it is conjectured that the mass of the Higgs particle in the minimal model is bounded by an amount that can be estimated without the knowledge of the physics at shorter distances. A possible numerical experiment which could give a nonperturbative estimate for the bound is proposed. PACS numbers: 14.80.Gt, 11.15.Ex, 11.15.Ha, 12.10.En

Experimental J / ψ hadronic production from 150 to 280 GeV/c

Abstract: A detailed study ofJ/ψ hadronic production has been performed in a high statistics experiment (more than 1.5 106J/ψ observed in their dimuon decay mode). Data have been taken with incident π±,K±,p±, on hydrogen and platinum targets, at 150, 200 and 280 GeV/c. We find from the observed nuclear dependance of the cross sections, that about 18% of theJ/ψ are produced diffractively. Using known structure functions of the quarks in the nucleon and in the pion, we derive estimations for the gluon structure functions.

Effective gauge theory and the effect of heavy quarks in Higgs boson decays

Abstract: A general framework is given for evaluating the contributions of as yet undiscovered heavy quarks to the gluonic decay rate of the Weinberg-Salam type Higgs boson. Since the Yukawa coupling of the Higgs boson to a quark pair is proportional to the quark mass, loop graphs involving heavy quarks have a non-vanishing effect on the gluonic decay width of the Higgs boson. This effect of heavy quarks with massesM j(j=t,...) much greater than the Higgs boson massm H is calculated in an effective gauge theory. The effects of two different kinds of large logarithms, lnM 2 /μ m 2 /μ 2 are separated and summed up by the renormalization group method. It is found that the higher order QCD corrections are large and that the gluonic contribution to the hadronic decay width is significant if there are more than three generations. The Higgs decay width can therefore be used to probe the number of generations of heavy quarks.

Composite-meson model with vector dominance based on U(2) invariant four-quark interactions

Abstract: An effective Lagrangian for composite σ, π, ω and ρ mesons is derived from a four-quark theory of the Nambu-Jona-Lasinio type. We study the various mutual relations between the renormalized parameters of this model. If electro-weak interactions are added, the model provides a dynamical foundation of vector-meson dominance.

Quark content of neutral mesons

Abstract: Radiative transitions involving neutral mesons with J/sup P/ = 0/sup -/ (eta,eta',iota(1440)) and 2/sup +/ (f,f',theta(1640)) are used to provide information on the light-quark content of these mesons, and to test predictions of models in which these states are quarkonium-gluonium mixtures. Some suggested observations include (l) phi..-->..eta'..gamma.., predicted to have a branching ratio of 7 x 10/sup -5/ in the standard quarkonium picture of eta', (2) f'..--> gamma gamma.., predicted to have a partial width > or approx. =200 eV if f' = ss-bar but very sensitive to possible destructive interference from small nonstrange-quark admixtures, and (3) iota(1440)..--> gamma gamma.. and theta(1640)..--> gamma gamma.., which will be easily detectable unless these states are almost totally free of quarkonium admixtures.

Neutrino and anti-neutrino charged-current inclusive scattering in iron in the energy-range 20 less-than ev less-than 300 gev

Abstract: Inclusive charged-current interactions of high-energy neutrinos and antineutrinos have been studied with high statistics in a counter experiment at the CERN Super Proton Synchrotron. The energy dependence of the total cross-sections, the longitudinal structure function, and the nucleon structure functionsF2,xF3, and\(\bar q^{\bar v} \) are determined from these data. The analysis of theQ2-dependence of the structure functions is used to test quantum chromodynamics, to determine the scale parameter Λ and the gluon distribution in the nucleon.

Energy Loss of Slowly Moving Magnetic Monopoles in Matter

Abstract: The cross section for exciting simple atoms by slowly moving magnetic monopoles is calculated. Including the effects of the monopole magnetic field on the atomic energy levels, an energy loss per unit density is obtained that is much larger than previous studies. For helium $(\frac{1}{\ensuremath{\rho}})\frac{\mathrm{dE}}{\mathrm{dx}}=15(\frac{\ensuremath{\beta}}{{10}^{\ensuremath{-}4}}){[1\ensuremath{-}{(9.29\ifmmode\times\else\texttimes\fi{}\frac{{10}^{\ensuremath{-}5}}{\ensuremath{\beta}})}^{2}]}^{\frac{3}{2}}$ MeV ${\mathrm{cm}}^{2}$/g for $\ensuremath{\beta}$ in the range ${10}^{\ensuremath{-}4}$ to ${10}^{\ensuremath{-}3}$. The possibility of using helium as a monopole detector is discussed.

Flavor-changing decays of the Zsup0

Abstract: Using the standard model of electroweak interactions, we compute the branching ratios for Zsup0..-->..qx-bar, where q and x are quarks of different flavor. Such processes can be distinguished from the background only when q is much more massive than x (or vice versa); these rates are insignificant unless there are four (or more) generations of quarks. Since the results are then sensitive to the unknown mixing angles and masses of undiscovered quarks, we discuss these quantities briefly. We find that some values of these parameters lead to event rates that might be detectable in an esup+esup- machine operating on the Zsup0 resonance. The appendices contain our Feynman rules and technical details of the calculation.

Possible Astronomical Effects of Mirror Particles

Abstract: A discussion is given of the astronomical implications of a model wherein every elementary particle would have a corresponding mirror (M-) particle of the same mass, and to each interaction (strong, weak, electromagnetic) there would correspond an M-interaction Ordinary (O-) and M-particles could interact essentially only by gravitation As the model properties are strictly symmetric, so also would be the cosmological evolution of O- and M-matter Qualitative consideration of how M-irregularities would evolve in the early universe suggests that on mass scales M< or approx =10/sup 6/ M/sub sun/ there will be practically no mixing of O- and M-matter except by accretion The model can be tested by improving the observational data on the primordial helium abundance, the missing mass in the galactic disk, and perhaps the nonradial oscillations of the sun

Masses of Superpartners of Quarks, Leptons, and Gauge Mesons in Supergravity Grand Unified Theories.

Abstract: A class of ''realistic'' supergravity grand-unified-theory models possessing two W-inos and two Z-inos which lie above and below W/sup + -/ and Z/sup 0/ mass, respectively, are examined. A lower bound on the W-ino mass of approx. =30 GeV is obtained with an upper bound of approx. =250 GeV on the Higgs mass. It is shown that the Z/sup 0/ decays prominantly into two W-inos if the mass of the W-ino< or =M/sub W//2. The superpartners of quarks and leptons are shown to be approximately degenerate and in some models have mass < or approx. =100 GeV.

Charged hadron composition of the final-state in e+e- annihilation at high-energies

Abstract: The inclusive production of π± andK± mesons and of protons and antiprotons ine+e− annihilation has been measured at c.m. energies ofW=14, 22 and 34GeV. Using time of flight measurements and Cerenkov counters the full momentum range has been covered. Differential cross sections and total particle yields are given. At particle momenta of 0.4 GeV/c more than 90% of the charged hadrons are pions. With increasing momentum the fraction of pions among the charged hadrons decreases. AtW=34 GeV and a momentum of 5 GeV/c the particle fractions are approximately π±:K±:p,\(\bar p = 0.55:0.3:0.15\). On average an event atW=34 GeV contains 10.3±0.4π±, 2.0±0.2K± and 0.8±0.1p,\(\bar p\). In addition, we present results on baryon correlations using a sample of events where two or more protons and/or antiprotons are observed in the final state.

Particles vs. events: the concatenated structure of world lines in relativistic quantum mechanics

Abstract: The dynamical equations of relativistic quantum mechanics prescribe the motion of wave packets for sets of events which trace out the world lines of the interacting particles. Electromagnetic theory suggests thatparticle world line densities be constructed from concatenation of event wave packets. These sequences are realized in terms of conserved probability currents. We show that these conserved currents provide a consistent particle and antiparticle interpretation for the asymptotic states in scattering processes. The relation between current conservation and unitarity is used to establish relations between pair production and annihilation amplitudes and scattering. The discrete symmetriesC, T, P are studied and it is shown that no Dirac sea (for fermions where such a construction is possible, or bosons where it is not) is required for consistency of the theory. These currents, furthermore, represent the discrete symmetries in a way consistent with their interpretation as particle currents.

Higgs-boson effects in grand unified theories

Abstract: It is argued that fine tuning of a minimal set of parameters, needed to fix the hierarchy of gauge-boson masses and a knowledge of intermediate symmetry groups, leads to "natural" mass scales for physical Higgs bosons in grand unified theories. This is applied to $\ensuremath{\Delta}B=2$ transitions in models based on SU(5), SO(10), SU(16), and ${[\mathrm{SU}(2N)]}^{4}$. It turns out that the Higgs bosons which mediate $\ensuremath{\Delta}B=2$ neutron-antineutron and hydrogen-antihydrogen oscillations become superheavy, and so such transitions can be observable only in theories with low unification scales, such as SU(16) and ${[\mathrm{S}\mathrm{U}(8)]}^{4}$, if we adhere to the hypothesis of minimal fine tuning.

Hadron spectroscopy in a flux-tube quark model

Abstract: Color-magnetic interactions (one-gluon exchange) are incorporated into a semirelativistic quark model and the spectra of ground states and orbital and radial excitations of light mesons, light baryons, charmonium, and $b$-quarkonium are calculated by treating the magnetic splitting exactly by variational methods. The $\ensuremath{\pi}\ensuremath{-}\ensuremath{\rho}$ splitting is fit and the $N\ensuremath{-}\ensuremath{\Delta}$ splitting is predicted in excellent agreement with experiment. In general, spin-spin and tensor splittings among light mesons and light baryons are calculated in good agreement with experiment. The splittings in heavy-meson spectroscopy are also predicted accurately, including the $P$-wave states of charmonium and $b$-quarkonium. Some problems and limitations of the quark-model description of the light mesons and baryons are emphasized. Spin-orbit splittings in the light mesons and $P$-wave baryon multiplets are calculated, but a unified understanding of the systematics is not obtained. Radial excitations in the meson and baryon systems are generally in error by 100-150 MeV, and the systematics are not understood.

Supersymmetry at ordinary energies. II. R invariance, Goldstone bosons, and gauge-fermion masses

Abstract: We explore the observable consequences of supersymmetry, under the assumption that it is broken spontaneously at energies of order 300 GeV. Theories of this sort tend automatically to obey a global $R$ symmetry, which presents us with a choice among phenomenologically unacceptable alternatives. If the $R$ symmetry is broken by scalar vacuum expectation values of order 300 GeV, there will be a semiweakly coupled light Goldstone boson, similar to an axion. If it is not broken by such vacuum expectation values but is broken by quantum-chromodynamic (QCD) anomalies, then there will be a light ninth pseudoscalar meson. If it is not broken by QCD anomalies, then the asymptotic freedom of QCD is lost at high energies, killing the hope of an eventual meeting of the electroweak and strong couplings within the regime of validity of perturbation theory. We also confront the problem of an uncomfortably light gluino. A general analysis of gaugino masses shows that the gluino mass is at most of order 1 GeV, and in many cases much less.

Decay of long-lived particles in the early universe

Abstract: It is pointed out that radiative decay of massive fermions can distort the cosmic background radiation. The present investigation is concerned with a study of decay lifetimes in the range from 10 to 100,000 years. Attention is given to the physics involved in determining the effect of radiative decay of massive fermions on observed photon backgrounds. The case of particles which decoupled when the effective number of species in equilibrium was in the range from 50 to 100 is considered, and constraints on particle masses and lifetimes are placed on the basis of observed photon fluxes. This approach provides results with special applications to particles predicted by supersymmetry theories and to right-handed neutrinos. Implications for galaxy formation are also discussed.

The discovery of subatomic particles

Abstract: 1. A world of particles 2 The Discovery of the Electron: Flashback - The Nature of Electricity Electric Discharges and Cathode Rays Flashback - Newton's Laws of Motion Deflection of Cathode Rays Flashback - Electric Forces Electric Deflection of Cathode Rays Flashback - Magnetic Forces Magnetic Deflection of Cathode Rays Thomson's Results Flashback - Energy Energy Relations in Thomson's Experiment Electrons as Elementary Particles 3. The Atomic Scale: Flashback - Atomic Weights Flashback - Electrolysis Measuring the Electronic Charge 4 The Nucleus: The Discovery and Explanation of Radioactivity The Discovery of the Nucleus Atomic Numbers and Radioactive Series The Neutron 5 More Particles: Photons Neutrinos Positrons Other Antiparticles Muons and Pions Strange Particles More Hadrons Quarks. Appendix A Newton's Second Law of Motion B Electric and Magnetic Deflection of Cathode Rays C Electric Fields and Field Lines D Work and Kinetic Energy E Energy Conservation in Cathode-Ray Experiments F Gas Properties and Boltzmann's Constant G Millikan's Oil-drop Experiment H Radioactive Decay 1 Potential Energy in the Atom J Rutherford Scattering K Momentum Conservation and Particle Collisions. Reading Sources of Illustrations Index .

Experimental-study of inclusive muon spectra from electron-positron collisions in the energy region 33 less-than-or-equal-to square-root-s less-than-equal-to 38.54 gev

Abstract: The results of a high-statistics study of inclusive muon spectra at PETRA are reported. Improved mass limits have been obtained for heavy quarks, heavy leptons, and charged Higgs particles. It is shown that the fragmentation properties of b quarks and c quarks are different, with the mean fragmentation variables = 0.75 +- 0.03 +- 0.06, = 0.46 +- 0.02 +- 0.05 and the average semileptonic branching ratio for the B and C hadrons BR(B) = (10.5 +- 1.5 +- 1.3)%, BR(C) = (11.5 +- 1.0 +- 1.7)%.

Pion photoproduction in the. delta. (1232) region and chiral bag models

Abstract: We calculate pion photoproduction near the $\ensuremath{\Delta}(1232)$ resonance using a version of the chiral bag model based on an effective Lagrangian that reproduces correct pion-nucleon phenomenology through third order in the pion field. The pionic corrections to the $M1$ (or $M1+$) amplitude are common to a broad class of chiral bag models and substantially improve agreement with experiment. We treat also the $E2$ (or $E1+$) multipole which is accessible in our approach since the effective Lagrangian induces quark-quark tensor coupling through pion exchange; this in turn permits the admixture of baryon components involving quark excitation to $d$ states. The resulting $E2$ admixture is consistent with the rather loose bounds set by the present experimental information on this quantity. The present work neglects the tensor force and $d$ state arising from gluon exchange between quarks.

Meson exchange hamiltonian for n n scattering up to 1-gev and delta nucleus dynamics

Abstract: A Hamiltonian for $\ensuremath{\pi}$, $N$, and $\ensuremath{\Delta}$ is constructed from meson-exchange mechanisms. The $\mathrm{NN}$ interaction in the model is directly derived from the Paris potential. Good fits to $\mathrm{pp}$ scattering data up to 1 GeV, including the "resonant" $^{1}D_{2}$ and $^{3}F_{3}$ partial waves, have been obtained when a $\ensuremath{\pi}N\ensuremath{\leftrightarrow}\ensuremath{\Delta}$ interaction is introduced in a dynamical three-body approach. The model can be used for a many-body study of $\ensuremath{\Delta}$-nucleus dynamics.

Supersymmetry and neutral-flavor nonconservation

Abstract: In supersymmetric theories gauge fermions and scalar quarks and leptons may radiatively induce neutral-flavor violation. Experimentally adequate suppression of these effects by the "super---Glashow-Iliopoulos-Maiani" mechanism constrains the masses, generational mass splittings, and mixing angles of the superpartners. We analyze the structure of these processes and examine the constraints placed on the superpartners by present, and potentially feasible, experimental limits on the rates for flavor-changing neutral processes.

Photon decays of baryons with strangeness

Abstract: The photon-decay amplitudes and widths of the low-lying strange baryons are calculated within the framework of the nonrelativistic quark model of Isgur and Karl. A comparison with experiment is made.