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Showing papers on "Elementary particle published in 1986"


Journal ArticleDOI
TL;DR: In this article, a superheated superconducting colloid (SSCD) detector using a SQUID readout system has been proposed, and two tests designed to study the practicality of such a detector are presented.
Abstract: The growing synergy between astrophysics, particle physics, and low background experiments strengthens the possibility of detecting astrophysical non-baryonic matter. The idea of direct detection is that an incident, massive weakly interacting particle could collide with a nucleus and transfer an energy that could be measured. The present low levels of background achieved by the PNL/USC Ge detector represent a new technology which yields interesting bounds on galactic cold dark matter and on light bosons emitted from the Sun. Further improvements require the development of cryogenic detectors, e.g. superheated superconducting colloid (SSCD) and crystal bolometers. We report two tests designed to study the practicality of a superheated superconducting colloid detector using a SQUID readout system. Furthermore, we show that in case of particles with spin interactions, one should consider detectors based on compounds of boron, lithium and fluorine.

752 citations


Book
01 Jan 1986
TL;DR: In this article, a course given at the University of Maryland for advanced graduate students has been used to deal with some of the latest developments in our attempts to construct a unified theory of the fundamental interactions of nature.
Abstract: Derived from a course given at the University of Maryland for advanced graduate students, this book deals with some of the latest developments in our attempts to construct a unified theory of the fundamental interactions of nature. Among the topics covered are spontaneous symmetry breaking, grand unified theories, supersymmetry and supergravity. The books starts with a quick review of elementary particle theory and continues with a discussion of composite quarks, leptons, Higgs bosons and CP violation; it concludes with consideration of supersymmetric unification schemes, in which bosons and leptons are considered in some sense equivalent. The second edition is updated and corrected and contains new chapters on recent developments.

509 citations


Book ChapterDOI
John Ellis1
01 Jan 1986
TL;DR: In this paper, a brief survey of some of the most interesting new particle searches which can be performed at LEP is given, with particular emphasis on the Higgs bosons and supersymmetry.
Abstract: In this contribution I have given a brief survey of some of the most interesting new particle searches which can be performed at LEP. Particular emphasis has been given to the particles (Higgs bosons, supersymmetry) whose existence is motivated by attempts to understand the masses of the elementary particles. There are many other aspects to LEP physics, such as precision measurements on the Z0 peak, toponium, QCD studies, and looking at the reaction e+e− → W+W−. However, I think that these few examples are sufficient to show that LEP physics will be very interesting, to Jack and to the rest of us.

442 citations


Journal ArticleDOI
TL;DR: In this paper, the electroweak radiative corrections to the partial decay widths of the Z-boson into a pair of leptons or quarks have been calculated in the standard theory.

182 citations


Journal ArticleDOI
TL;DR: The constituent-quark model is used to predict the electron spectra in semileptonic meson decays, and particular attention is paid to the end-point region of the spectrum in B decays.
Abstract: We use the constituent-quark model to predict the electron spectra in semileptonic meson decays. Particular attention is paid to the end-point region of the spectrum in B decays, which is important to the determination of the b..-->..u weak mixing angle.

145 citations


Journal ArticleDOI
TL;DR: In this article, a simple renormalization framework was extended to treat the Higgs potential of the standard model and the one-loop correction δ(M) in the natural relation h (M) = √ 1 2 G μ m H 2 [1 + δ (M)] was obtained.

143 citations


Journal ArticleDOI
TL;DR: In this paper, the authors review the progress that has been made in understanding weak interaction effects in hadrons and their focus is on the quark model and its role in connecting hadronic processes with the underlying SU(2) L × U(1) weak interaction theory.

142 citations


Journal ArticleDOI
TL;DR: It is found that at the Fermilab Tevatron energy ..sqrt..s-italic = 2 TeV, W-itali-gluon fusion exceeds the Drell-Yan production of top quarks for masses above 100 GeV.
Abstract: We show that heavy-quark production via W-italic-gluon fusion in high-energy p-italicp-italic and p-barp-italic collisions is an important source of the heavier member of an SU(2)/sub L-italic/ doublet of quarks if the mass splitting within the doublet is large. W-italic-gluon fusion exceeds the strong production of heavy quarks for mass splittings greater than 300--350 GeV at ..sqrt..s-italic = 10 TeV and 400--450 GeV at ..sqrt..s-italic = 40 TeV. An alternative way to regard W-italic-gluon fusion is as the production of the heavier quark by fusing its light partner with a W-italic boson. We use a distribution function for the light partner to show that this process gives results which agree qualitatively with W-italic-gluon fusion. We also discuss the Drell-Yan production of an SU(2)/sub L-italic/ doublet of heavy quarks via a virtual W-italic boson and corrections to this process from initial gluons. We find that at the Fermilab Tevatron energy ..sqrt..s-italic = 2 TeV, W-italic-gluon fusion exceeds the Drell-Yan production of top quarks for masses above 100 GeV.

137 citations


Journal ArticleDOI
TL;DR: In this paper, the problem of computing the cross section for producing heavy strongly interacting particles (quarks, gluinos, squarks) in high-energy hadron collisions was considered.

128 citations


Journal ArticleDOI
TL;DR: In this paper, a bound on the Higgs isosplitting of about 7mZ follows from current deep inelastic νμ, ν μ data, assuming degenerate masses for the neutral scalars, and precise measurements of mZ, mW and sin2 ζW with an accuracy of 1mZ or less.

112 citations



Journal ArticleDOI
TL;DR: The dispersion law for these excitations is given and shows that they grow more particlelike (are asymptotically free) at large momenta, thus providing a qualitative description of the short-lived excitation at the origin of a gluon jet.
Abstract: The dynamical generation of a pole in the self-energy of a Yang-Mills field: an extension of the Schwinger mechanism: establishes a link between the tendency of the field to form nonperturbative vacuum condensates and its ''noninterpolating'' property in the confining phase: the fact that it has no particles associated with it. The nonvanishing residue of such a pole: a parameter b/sup 4/ of dimension (mass)/sup 4/: on the one hand provides for a nonvanishing value of , a contribution to the ''gluon condensate.'' On the other hand, it implies a dominant nonperturbative form of the propagator that has no particle singularity on the real k/sup 2/ axis; instead, it describes a quantized field whose elementary excitations are short lived. The dispersion law for these excitations is given and shows that they grow more particlelike (are asymptotically free) at large momenta, thus providing a qualitative description of the short-lived excitation at the origin of a gluon jet. At large k/sup 2/, the nonperturbative propagator reproduces nonperturbative corrections derived from the operator-product expansion.

Journal ArticleDOI
TL;DR: The cross section ratio of neutral-current and charged-current semi-leptonic interactions of muon-neutrinos on isoscalar nuclei has been measured with the result: Rv=0.3093±0.0031 for hadronic energy larger than 4 GeV as discussed by the authors.

Journal ArticleDOI
Ira Wasserman1
TL;DR: It is shown that heavy neutral fermions in the galactic halo could produce numerous detectable low-energy events in a ''thermal'' neutrino detector if the heavy-fermionndashnucleon vector coupling is comparable in strength to the vector weak interaction.
Abstract: It is shown that heavy neutral fermions in the galactic halo could produce numerous detectable low-energy events in a ''thermal'' neutrino detector if the heavy-fermionndashnucleon vector coupling is comparable in strength to the vector weak interaction. The conditions under which a detectable event rate could arise for fermions with purely axial-vector couplings are also discussed. In a silicon detector heavy-fermion events would be concentrated at low energies, and could be distinguished from solar or supernova neutrino events, which are expected to have a flatter energy spectrum. A measurement of the energy spectrum of heavy-fermion events could lead to a determination of the fermion mass, subject to astrophysical uncertainties concerning the velocity distribution of halo particles.

Journal ArticleDOI
TL;DR: In this paper, the authors predict the quantitative lifetime differences of weakly decaying charmed baryons which arise due to preasymptotic bound state effects, and compare these predictions in a nonrelativistic quark model and in a bag model.
Abstract: We predict the quantitative lifetime differences of weakly decaying charmed baryons which arise due to preasymptotic bound state effects. These predictions are to a large extent model independent. We also give and compare detailed quantitative estimates obtained in a nonrelativistic quark model and in a bag model. Finally, we show how the various nonspectator effects can be separated and determined phenomenologically, once the lifetime of charmed baryons are measured with sufficient accuracy.

Journal ArticleDOI
TL;DR: If the authors' galactic halo is composed of heavy (several gigaelectron- volts), weakly interacting particles, pair annihilation into a heavy-quark--antiquark bound state plus a monochromatic photon can produce potentially observable sharp peaks in the diffuse cosmic-..gamma..-ray background.
Abstract: If our galactic halo is composed of heavy (several gigaelectron- volts), weakly interacting particles, pair annihilation into a heavy-quark--antiquark bound state plus a monochromatic photon can produce potentially observable sharp peaks in the diffuse cosmic-\ensuremath{\gamma}-ray background.

Journal ArticleDOI
TL;DR: Constraints on the mixings of the exotic fermions are placed from experimental limits on flavor-changing neutral currents and the observed weak universality of charged-current interactions.
Abstract: In E/sub 6/ superstring theories, there are new fermion fields which lie in the 27-dimensional representation along with the known fermions. We examine possible production modes of these exotic fermions and their likely decays. Whereas e/sup +/e/sup -/ collider data exclude new charged fermions with masses below 23 GeV, it appears that present pp-bar collider data for dimuons and for isolated single electrons exclude exotic quarks with masses below 30 GeV and considerable regions of lepton mass assignments in the range 20-45 GeV (assuming m/sub E/>mE,m/sub N//sub E/). We place constraints on the mixings of the exotic fermions from experimental limits on flavor-changing neutral currents and the observed weak universality of charged-current interactions. The decays of the exotic h quark (singlet, charge -(1/3)) satisfy the bound GAMMA(h..-->..de/sup +/e/sup -/)/GAMMA(h..-->..ue..nu..)> or approx. =12%. Production and decays of very heavy exotics are also considered.

Journal ArticleDOI
TL;DR: Polarization effects in composite and supersymmetric models are studied in detail and the nonvanishing effects are connected to the breaking of the chiral symmetry by the new interactions.
Abstract: Electrons and positrons in storage rings have natural polarization which is perpendicular to the beam direction. Effects of the transverse polarization to azimuthally integrated cross sections are studied. In the standard model, the polarization does not affect the cross section up to a correction proportional to the electron mass, which is negligible at high energies. This fact is closely related to the chiral symmetry of the standard model. It is not necessarily true if there are new interactions beyond the standard model. Polarization effects in composite and supersymmetric models are studied in detail. New particles such as scalar bosons and excited electrons in composite models can give nonzero polarization effects. In supersymmetric theories, the transverse polarization is useful to probe the mixing of the scalar-electron states. The nonvanishing effects are connected to the breaking of the chiral symmetry by the new interactions.

Journal ArticleDOI
Bob Holdom1
TL;DR: It is proposed that a dynamical mass for a fourth family of quarks is responsible for breaking of the weak interactions, and for breaking the extended-technicolor interactions which provide mass to the third family, which greatly simplifies the extended technicolor sector and avoids fermions with exotic quantum numbers.
Abstract: It is proposed that a dynamical mass for a fourth family of quarks is responsible for breaking of the weak interactions, and for breaking of the extended-technicolor interactions which provide mass to the third family. This greatly simplifies the extended technicolor sector and avoids fermions with exotic quantum numbers. A technicolor sector is still required, but it is lighter than usual. The most-attractive-channel hypothesis for symmetry breakdown is relied on.


Journal ArticleDOI
Alain J. Martin1
TL;DR: In this article, it was shown that the large angular momentum behavior of the leading Regge trajectory of a meson (q\(\bar q\)) or a baryon (qqq) can be obtained by minimizing the classical energy of the system for given angular momentum.
Abstract: We prove that the large angular momentum behaviour of the leading Regge trajectory of a meson (q\(\bar q\)) or a baryon (qqq) can be obtained by minimizing the classical energy of the system for given angular momentum. A two-body quark-antiquark linear potential plus relativistic kinematics produces asymptotically linear Regge trajectories for mesons. For baryons we take either a sum of two-body potentials with half strength or a string of minimum length connecting the quarks, and find in both cases that the favoured configuration is a quark-diquark system and that the baryon and meson trajectories have the same slope. Short-distance singularities of the potential are shown to be unimportant.

Journal ArticleDOI
TL;DR: The effects of spin-dependent charge-symmetry-breaking forces can be measured in elastic scattering and it is found that a term in the one-pion exchange potential arising from the neutron-proton mass difference is dominant.
Abstract: The effects of spin-dependent charge-symmetry-breaking forces can be measured in elastic $n\ensuremath{-}p$ scattering. We find that a term in the one-pion exchange potential arising from the neutron-proton mass difference is dominant. This, together with single-photon exchange, gives a result in agreement with a recent precise measurement made at TRIUMF. Other shorter-ranged effects associated with rho exchange, meson mixing, two-pion exchanges, and quark interactions give smaller contributions.

Journal ArticleDOI
TL;DR: An effective Lagrangian for QCD is developed in terms of order parameters of the gluon condensate in which the order parameters are identified with averages of the low-momentum components of the vector potential.
Abstract: We develop an effective Lagrangian for QCD in terms of order parameters of the gluon condensate. (A useful analogy to the Ginzburg-Landau theory of superconductivity may be made.) In this work the order parameters are identified with averages of the low-momentum components of the vector potential. The theory is formulated such that only a single order parameter, which describes the number of gluon pairs in the condensate (of all colors), is relevant. This order parameter becomes spatially dependent in the presence of quarks and one obtains a dynamical model for the formation of hadrons as nontopological soliton solutions of the effective Lagrangian of our model.

Journal ArticleDOI
TL;DR: The standard model for big-bang nucleosynthesis is modified to allow for the presence of a generic particle species, i.e., one which maintains good thermal contact with either the photons or the light neutrino species throughout the epoch of primordialucleosynthesis.
Abstract: We modify the standard model for big-bang nucleosynthesis to allow for the presence of a generic particle species, i.e., one which maintains good thermal contact with either the photons or the light neutrino species throughout the epoch of primordial nucleosynthesis. The production of D, /sup 3/He, /sup 4/He, and /sup 7/Li is calculated as a function of the mass, degrees of freedom, and spin statistics of the generic particle. We show that in general, the effect of an additional generic species cannot simply be parameterized as the equivalent number of additional light neutrino species. The presence of generic particles also affects the predicted value for the neutrino-to-photon temperature ratio.

Journal ArticleDOI
TL;DR: In this paper, the existence of light gluinos with mass above 1 GeV/c2 and lifetime in the range 5·10−11 s to 5· 10−7s was shown to be impossible.
Abstract: A sensitive search has been done for the production of new long-lived and penetrating particles by 300 GeV/c negative pions. No new state —decaying into at least two charged known particles —has been detected with mass above 1 GeV/c2 and lifetime in the range 5·10−11 s to 5·10−7s. We give upper limits on production cross sections, and consequences on the existence of heavy “axion-like” particles, heavy neutrinos and supersymmetric particles. In particular, this experiment excludes the existence of light gluinos with lifetime in the range 5·10−11 to 10−8s: this closes the last “window of opportunity” for gluinos withM<2 GeV/c2 and lifetime measurable in particle physics experiments.

Journal ArticleDOI
TL;DR: In this paper, a complete set of symmetry-related hadronic loops were considered for the analysis of baryon spectroscopy and it was shown that these effects very likely constitute the dominant contribution to the observed splitting and mixing pattern of the (56, 0+) and (70, 1−)-multiplet.

Journal ArticleDOI
TL;DR: In this article, the effects of the additional Higgs bosons in the radiative corrections to the leptonic processes were investigated in the 1-loop renormalization of the SU(2)×U(1) electroweak gauge theory with two Higgs doublets.
Abstract: The 1-loop renormalization of theSU(2)×U(1) electroweak gauge theory with two Higgs doublets is performed in the on-shell scheme with finite self energies and vertices. Assuming different vacuum expectation values for the scalar doublets, which yield enhanced Yukawa couplings to fermions, we calculate the effects of the additional Higgs bosons in the radiative corrections to the leptonic processes:μ-decay,vμe-scattering, ande+e−→μ+μ−,τ+τ− with longitudinal polarization at PETRA and LEP/SLC energies. It is found that large effects occur in theMW−MZ mass relation, the determination of sin2θw from\(\sigma (v_\mu e)/\sigma (\bar v_\mu e)\) and thee+e− forward-backward and polarization asymmetries, if either the charged Higgs or the additional neutral scalar/pseudoscalar are heavy. Enhancement effects and effects of light neutral bosons can better be observed in thee+e−→τ+τ− integrated cross section.

Journal ArticleDOI
TL;DR: In this article, the renormalization scheme dependence of electroweak parameters shifts is used to estimate uncertainties due to higher order effects, taking care of a systematic leading log summation.
Abstract: The renormalization scheme dependence of electroweak parameters shifts is used to estimate uncertainties due to higher order effects. Parameter shifts are calculated from weakly scheme dependent quantities, taking care of a systematic leading log summation. A “non-standard” definition of sin2θW is also considered which is to be used if the ρ-parameter is kept as free parameter. Results for the leptonic decay widths of the vector bosons are also given.

Journal ArticleDOI
TL;DR: Applied to the standard model, this suggests that there is an upper limit to quark and lepton masses and has implications for the ''decoupling'' of heavy fermions and on the issue of whether apparently ''anomalous'' gauge theories can be consistently quantized.
Abstract: A fermion mass generated by spontaneous symmetry breaking is proportional to its Yukawa coupling y to a Higgs field. Like the Higgs-field self-coupling, y may well be trivial and diverge at a finite energy scale ..lambda../sub f/, corresponding to an upper limit on fermion masses. We verify this by solving a simple model by means of a 1/N expansion. Applied to the standard model, this suggests that there is an upper limit to quark and lepton masses. These results have implications for the ''decoupling'' of heavy fermions and bear on the issue of whether apparently ''anomalous'' gauge theories can be consistently quantized.

Journal ArticleDOI
TL;DR: The agreement with experiment is quite satisfactory in spite of very limited freedom in the choice of the parameter values, giving strong support to the idea that qualitatively and even semiquantitatively baryon physics can be deduced from meson physics via solitons.
Abstract: A chiral-invariant effective Lagrangain is constructed from pions and the low-mass mesons. Soliton solutions of this Lagrangain are investigated. These are used to predict properties of baryons. The agreement with experiment is quite satisfactory in spite of very limited freedom in the choice of the parameter values. This gives strong support to the idea that qualitatively and even semiquantitatively baryon physics can be deduced from meson physics via solitons.