Showing papers on "Elementary particle published in 1987"
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01 Jan 1987
TL;DR: In this article, the Dirac Delta Function and Decay Rates and Cross Sections C Pauli and Dirac Matrices D Feynman Rules (Tree Level) are presented for elementary particle physics.
Abstract: 1 Historical Introduction to the Elementary Particles 2 Elementary Particle Dynamics 3 Relativistic Kinematics 4 Symmetries 5 Bound States 6 The Feynman Calculus 7 Quantum Electrodynamics 8 Electrodynamics and Chromodynamics of Quarks 9 Weak Interactions 10 Gauge Theories 11 Neutrino Oscillations 12 Afterword: What's Next? A The Dirac Delta Function B Decay Rates and Cross Sections C Pauli and Dirac Matrices D Feynman Rules (Tree Level)
1,714 citations
TL;DR: In this paper, the exact formulas for the capture of weakly interacting massive particles (WIMPs) by a massive body are derived and the exact capture rate for the sun is also recalculated and found to be from 1.5 times higher to 3 times lower than previously believed.
Abstract: The exact formulas for the capture of weakly interacting massive particles (WIMPs) by a massive body are derived. Capture by the earth is found to be significantly enhanced whenever the WIMP mass is roughly equal to the nuclear mass of an element present in the earth in large quantities. For Dirac neutrino WIMPs of mass 10-90 GeV, the capture rate is 10-300 times that previously believed. Capture rates for the sun are also recalculated and found to be from 1.5 times higher to 3 times lower than previously believed, depending on the mass and type of WIMP. The earth alone or the earth in combination with the sun is found to give a much stronger annihilation signal from Dirac neutrino WIMPs than the sun alone over a very large mass range. This is particularly important in the neighborhood of the mass of iron where previous analyses could not set any significant limits.
546 citations
TL;DR: In this paper, the authors proposed a new scenario of the baryon asymmetry generation in the framework of standard electroweak theory which is based on the recent observation that anomalous Baryon number violating processes are nonsuppressed at high temperatures.
519 citations
TL;DR: This model of meson decays in a model with chromoelectric flux-tube breaking motivated by the strong-coupling limit of QCD promises to be a useful tool for understanding the properties of unconventional mesons, especially meson hybrids.
Abstract: We have examined meson decays in a model with chromoelectric flux-tube breaking motivated by the strong-coupling limit of QCD. Our analysis includes all of the simple decay modes of mesons with up to two units of orbital or one unit of radial excitation, as well as a number of other interesting modes and higher-mass resonances. In conjunction with the wave functions of a relativized version of the quark model, our calculations provide, in terms of a single elementary flux-tube-breaking amplitude, predictions for meson decay amplitudes which are in excellent correspondence to experiment. The model also (1) leads to an understanding of the relevance and success of the $^{3}\mathrm{P}_{0}$ model, (2) provides predictions for channels in which it should be possible to see many of the missing low-lying mesons of the quark model, (3) points toward solutions to some puzzles in meson phenomenology, and (4) promises to be a useful tool for understanding the properties of unconventional mesons, especially meson hybrids.
245 citations
TL;DR: In this article, the authors consider the production and experimental signatures of excited quarks Q* of spin and isospin 1/2 at hadron colliders and estimate the background for those channels which are most promising for Q* identification.
Abstract: Composite models generally predict the existence of excited quark and lepton states. We consider the production and experimental signatures of excited quarks Q* of spin and isospin 1/2 at hadron colliders and estimate the background for those channels which are most promising for Q* identification. Multi-TeVpp-colliders will give access to such particles with masses up to several TeV.
166 citations
TL;DR: In this paper, the upper bound on the Higgs boson mass was derived from the condition that baryon asymmetry produced during the electroweak phase transition should not be diluted by the anomalous electroweak Baryon number nonconserving processes.
Abstract: We determine the upper bound on the Higgs boson mass from the condition that baryon asymmetry produced during the electroweak phase transition should not be diluted by the anomalous electroweak baryon number non-conserving processes. The value is insensitive to the mass of t-quark and equal to 45 GeV, slightly depending on the magnitute of the preexponential factor in the rate of the B non-conservation. This gives also upper bound on the top quark mass mt<80 GeV.
157 citations
TL;DR: From neutral-current constraints based on present experimental data, lower bounds of about 180 and 210 GeV are obtained for the second W and Z bosons of this model, respectively.
Abstract: If the particle content of a supersymmetric SU(3)\ifmmode\times\else\texttimes\fi{}SU(2)\ifmmode\times\else\texttimes\fi{}SU(2)\ifmmode\times\else\texttimes\fi{}U(1) gauge model is extended to include new quarks and leptons as given by the 27 representation of ${\mathrm{E}}_{6}$, an unconventional left-right assignment is possible, resulting in a number of desirable features, one of which is a simpler Higgs-boson structure. Also, a conserved multiplicative quantum number can be defined as a generalization of the usual R parity in most models of supersymmetry. This prevents ${W}_{L}$-${W}_{R}$ mixing and makes possible a massless Dirac neutrino whose right-handed component is effectively inert. From neutral-current constraints based on present experimental data, lower bounds of about 180 and 210 GeV are obtained for the second W and Z bosons of this model, respectively.
144 citations
TL;DR: It is shown that the interaction of global strings with Goldstone bosons can be described by a model of strings coupled to an antisymmetric tensor field with a particular choice of the coupling constant.
Abstract: It is shown that the interaction of global strings with Goldstone bosons can be described by a model of strings coupled to an antisymmetric tensor field with a particular choice of the coupling constant. This formalism is applied to calculate the rate of Goldstone-boson radiation from a class of closed-loop trajectories. The lifetime of a typical loop is found to be very short, about twenty oscillation periods, in agreement with an earlier estimate by Davis.
132 citations
TL;DR: In this paper, the authors investigated the production of a standard Higgs boson pair in proton-proton collisions at the SSC energy, which alloys us to study the trilinear Higgs coupling.
128 citations
TL;DR: It is found that thermal production of axions in the early Universe (via the Primakoff and photoproduction processes) dominates coherent production by a factor of about 1200, and the photon luminosity from the decays of these relic axions leads to a model-independent upper limit to the axion mass of order 2 to 5eV.
Abstract: It is found that, for Peccei-Quinn symmetry-breaking scales of less than about 4 x 10 to the 8th GeV (corresponding to axion masses of greater than about 0.03 eV) thermal production of axions in the early universe (via the Primakoff and photoproduction processes) dominates coherent production by a factor of about 1200/m sub a/(1 eV)/ exp 2.175. The photon luminosity from the decays of these relic axions leads to an upper limit to the axion mass of order 2-5 eV. If the axion mass saturates this bound, relic axion decays may well be detectable.
116 citations
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TL;DR: In this paper, the spectroscopy of bound states of charm, beauty, and the postulated top particles of heavy quarks are discussed. And the experimental data concerning particles containing heavy quark is presented.
Abstract: This review is devoted to the subject of heavy quarks. Experimental data concerning particles containing heavy quarks is presented. The spectroscopy of bound states of charm, beauty, and the postulated top particles are discussed. (AIP)
TL;DR: In this article, the relevance of heavy quark fusion processes for production of both neutral and charged Higgs bosons was examined, and it was shown that gg fusion is generally larger than t t fusion for the neutral Higgs and even dominates WW/ZZ fusion in the region m H 0 ≤ 1 TeV for top masses above m t = 150 GeV.
TL;DR: By using SN 1987a as a 'source' of neutrinos with energy approx.10 MeV, this work finds that the Majoron-electron neutrino coupling must be less than about 10/sup -3/; if neut rinos couple to a massless vector particle, its dimensionless coupling mustBe less thanAbout 10/Sup -3 /; and if neutRinos couple with strength g to a massive boson of mass M, then g/M must
Abstract: By using SN 1987a as a 'source' of neutrinos with energy approx.10 MeV we place limits on the couplings of neutrinos with cosmic background particles. Specifically, we find that the Majoron-electron neutrino coupling must be less than about 10/sup -3/; if neutrinos couple to a massless vector particle, its dimensionless coupling must be less than about 10/sup -3/; and if neutrinos couple with strength g to a massive boson of mass M, then g/M must be less than 12 MeV/sup -1/. 11 refs., 3 tabs.
TL;DR: In this article, the cross-section ratio of neutral-current and charged-current semileptonic 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.
Abstract: The cross-section ratio of neutral-current and charged-current semileptonic 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. From this ratio we determined the electroweak mixing angle sin2θW, wheremc is the charm-quark mass in GeV/c2. Comparison with direct measurements ofmw andmz determines the radiative shift of the intermediate boson mass Δr=0.077±0.025(exp.)±0.038(syst.), in agreement with the prediction. Assuming the validity of the electroweak standard theory we determined ϱ=0.990−0.013(mc−1.5)±0.009(exp.)±0.003(theor.).
TL;DR: In this article, the interaction of high energy protons (between 100 MeV and 20 GeV incident energy) with nuclei is studied in the frame of an intranuclear cascade (INC) model.
TL;DR: In supersymmetric E/sub 6/ gauge models based on superstring theory, an exactly conserved multiplicative quantum number can be defined to separate all particles into two groups, making possible a truly massless Dirac neutrino whose right-handed component is effectively inert and a second W boson with a mass perhaps as low as 300 GeV in a model with unconventional particle assignments.
Abstract: In supersymmetric E/sub 6/ gauge models based on superstring theory, an exactly conserved multiplicative quantum number can be defined to separate all particles into two groups. This dichotomy is especially important if left-right symmetry is realized at low energies. It makes possible a truly massless Dirac neutrino whose right-handed component is effectively inert and a second W boson with a mass perhaps as low as 300 GeV in a model with unconventional particle assignments.
TL;DR: A QCD parton-shower Monte Carlo model is used to simulate the production and decay of W bosons in hadron-hadron collisions and the overall event topologies for both the leptonic and hadronic decay modes of the W and W' bosons are analyzed.
Abstract: A QCD parton-shower Monte Carlo model is used to simulate the production and decay of W bosons in hadron-hadron collisions at c.m. energies of 540 and 1600 GeV. In addition, fictitious narrow heavy W' bosons are generated at c.m. energies of 1600 and 40X0 GeV. The overall event topologies for both the leptonic and hadronic decay modes of the W and W' bosons are analyzed using jet and cluster techniques. The leptonic mode allows for a study of the jets produced by the initial-state parton showers, while an analysis of the hadronic mode enables us to place limits on the ability to reconstruct, from an examination of ''jets,'' the mass of the produced W or W' boson. Our results are equally valid for the production of heavy Z' bosons of the corresponding mass.
TL;DR: It may be possible to tag the WW fusion events in a manner analogous to that used in two photon physics, whereby the Higgs bosons produced by WW fusion at the SSC will have transverse mementum of order M/sub w/.
Abstract: Heavy Higgs bosons produced by WW fusion at the Superconducting Super Collider will have transverse momentum of order ${M}_{W}$. The background due to qq\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}ZZ will produce pairs with characteristically less transverse momentum, so the transverse momentum of the Z pair provides a useful signature. The transverse momentum of the Higgs boson is balanced by that of the quarks that emitted the virtual W's. These quark jets can be used to tag WW fusion events.
TL;DR: In the limit that the singlet-Higgs coupling becomes much larger than the Higgs self-coupling, the 4W vertex differs from that in the standard model.
Abstract: We study the effects on the vector-boson parameters due to a heavy scalar singlet interacting strongly with the Higgs sector of the standard model. The one-loop-induced effects due to the additional scalar are not suppressed by inverse powers of its mass. In the limit that the singlet-Higgs coupling becomes much larger than the Higgs self-coupling, the 4W vertex differs from that in the standard model. In this limit the leading corrections are not related to the divergences of the gauged nonlinear \ensuremath{\sigma} model.
TL;DR: In this paper, a new method of QCD-analysis of singlet and nonsinglet structure functions based on their expansion in orthogonal Jacobi polynomials is proposed.
Abstract: A new method of QCD-analysis of singlet and nonsinglet structure functions based on their expansion in orthogonal Jacobi polynomials is proposed. An accuracy of the method is studied and its application is demonstrated using the structure functionF2(x, Q2) obtained by the EMC Collaboration from measurements with an iron target.
TL;DR: The production and subsequent decays of the S- and P-wave quarkonium states of a heavy quark that may be produced at a multi-TeV hadron collider are studied to assess the prospects for discovery of a new heavy quarks via its bound-state decays.
Abstract: We study the production and subsequent decays of the S- and P-wave quarkonium states of a heavy quark that may be produced at a multi-TeV hadron collider. Our considerations are focused on the lighter member of a fourth-generation doublet, for which the weak decays of the quark are expected to be suppressed by mixing angles. For quarkonium masses \ensuremath{\lesssim}1 TeV, the dominant production is via gluon fusion. In addition to the decay channels that are present in the charm and bottom systems, heavy quarkonia can decay into ${W}^{+}$${W}^{\mathrm{\ensuremath{-}}}$, ${Z}^{0}$${Z}^{0}$, and ${Z}^{0}$\ensuremath{\gamma} pairs. Furthermore, the latter decay rates may be enhanced due to couplings of the heavy quarks to the longitudinal components of the gauge bosons. We assess the prospects for discovery of a new heavy quark via its bound-state decays. Quarks with masses up to \ensuremath{\approxeq}100 GeV can be found from the decay of the ${1}^{\mathrm{\ensuremath{-}}\mathrm{\ensuremath{-}}}$ state (\ensuremath{\psi}) into lepton pairs. If the decay of the pseudoscalar quarkonium state into a Z boson and a Higgs boson is kinematically allowed, there is a rather clean signal for the Higgs boson, even for the intermediate-mass Higgs boson with 2${m}_{t}$${m}_{H}$2${M}_{W}$. Furthermore, H\ensuremath{\gamma} and HH pairs would also be present at fairly large rates.
TL;DR: An upper bound of 108 GeV to the mass of the lightest Higgs scalar is found, independent of the precise gauge group, soft-supersymmetry-breaking parameters, or superpotential parameters.
Abstract: We consider low-energy supersymmetric models which come from ${\mathrm{E}}_{6}$-based grand unified or superstring-inspired theories whose scalar fields come from 27's, 27\ifmmode\bar\else\textasciimacron\fi{}'s, or 1's of ${\mathrm{E}}_{6}$. Two classes of models emerge. In one, an upper bound of 108 GeV to the mass of the lightest Higgs scalar is found, independent of the precise gauge group, soft-supersymmetry-breaking parameters, or superpotential parameters. In the other, the requirement of perturbative unification is sufficient to arrive at a similar bound. Other Higgs-boson mass relations are also discussed. Failure to find a Higgs boson with a mass near or below 108 GeV would therefore rule out nearly all such ${\mathrm{E}}_{6}$-based models.
TL;DR: A minimal extension of the standard model is proposed toorate the light-neutrino masses and the resolution of the strong CP problem, and a unique light pseudo-Goldstone boson arises from the model.
Abstract: A minimal extension of the standard model is proposed to incor- porate the light-neutrino masses and the resolution of the strong CP problem. A unique light pseudo-Goldstone boson, whose coupling to the electron is 1 or 2 orders of magnitude greater than that of the conventional hadronic axion, arises from the model. The scale of Peccei-Quinn symmetry breaking is shown to be greater than 10/sup 10/ GeV through its connection to the light-neutrino masses, and is further constrained if the (hypothetical) fourth family of quarks and leptons exist.
TL;DR: A linear combination of polarized forward-backward asymmetry and polarization asymmetry with initial-state-electron longitudinal polarization whose deviation from the value of the standard model can measure the effects of new currents directly.
Abstract: We study various forward-backward and polarization asymmetries evaluated near the Z/sup 0/ resonance for theories with SU(2)/sub L/ x U(1)/sub Y/ x U(1)/sub Y//sub '/ and SU(2)/sub L/ x SU(2)/sub R/ x U(1)/sub B//sub -//sub L/ gauge structures. Extension to other gauge structures is very simple in our formalism. We construct a linear combination of polarized forward-backward asymmetry and polarization asymmetry with initial-state-electron longitudinal polarization whose deviation from the value of the standard model can measure the effects of new currents directly. The analysis is exact at the tree level of the theory and enables one to study any model with any Higgs sector in terms of a fixed number of parameters. The results show that for a typical class of models the measurement of different asymmetries to 1% will impose a lower bound on M/sub Z//sub '/, the mass of an additional neutral gauge boson, to be of order 10 M/sub Z/. Even much less accurate measurements will yield interesting information about new gauge structures. We also examine the implications of extended gauge structures for the precise value of the W/sup +- / mass.
TL;DR: The properties of excited weak bosons which naturally arise in composite models of quarks, leptons, andWeak bosons are discussed in the framework of generalized vector-boson dominance and the proposed Superconducting Super Collider is found to be the suitable machine for their discovery.
Abstract: The properties of excited weak bosons which naturally arise in composite models of quarks, leptons, and weak bosons are discussed in the framework of generalized vector-boson dominance. Special emphasis is given to their low-energy implications, their decay modes, and production in high-energy hadron-hadron collisions. The proposed Superconducting Super Collider is found to be the suitable machine for their discovery.
TL;DR: It is shown that gluon fusion via quark and scalar-quark loops dominates the usual electroweak quark-antiquark annihilation process if there exist sufficiently heavy quarks or scalar quarks.
Abstract: We discuss the pair production of charged Higgs bosons in high-energy hadron collisions, concentrating on supersymmetric models with two Higgs doublets. We show that gluon fusion via quark and scalar-quark loops dominates the usual electroweak quark-antiquark annihilation process if there exist sufficiently heavy quarks or scalar quarks.
TL;DR: In this article, the decays of a heavy neutral gauge boson (Z,Z) into superstring-inspired electroweak models with an extra U(1) gauge group, two Higgs doublets, and a Higgs singlet were evaluated.
Abstract: We evaluate the decays of a heavy neutral gauge boson ${Z}_{2}$ into ${W}^{+}$${W}^{\mathrm{\ensuremath{-}}}$, the Z and a Higgs boson, or two Higgs bosons in superstring-inspired electroweak models with an extra U(1) gauge group, two Higgs doublets, and a Higgs singlet. The branching ratios for these processes are generally similar and two-boson decay modes of ${Z}_{2}$ must exist at the few-percent level if kinematically accessible, although the bosonic modes which dominate in any given scenario depend on the U(1) quantum numbers and mixing in the Higgs sector. Lower bounds on the ${Z}_{2}$ mass versus the Z,Z' mixing are discussed; for the no-scale must be above 550 GeV.
CERN1
TL;DR: In this article, the authors explore the phenomenological constraints on minimal model parameters imposed by the experimental non-observation of charginos and charged Higgs bosons, as well as by cosmological constraint on neutralinos.
TL;DR: In this paper, the authors set upper limits for rare exclusive decays of B mesons arising from higher order processes in the standard model of electroweak interactions via "penguin diagrams" in B decay.
TL;DR: In this article, the branching ratio with respect to the π+π-channel was shown to be 3.5×10−6, which is similar to the result obtained previously by dispersion relation techniques in a non-chiral model.
Abstract: We calculate theK S Emphasis>0 →γγ decay within the approach of non-linear realization of chiralS U(3)×S U(3). The branching ratio with respect to theπ+π- channel turns out to be 3.5×10−6 and therefore similar to the result gotten previously by dispersion relation techniques in a non-chiral model. We also discuss theK L 0 →γγ decay by taking into account new results onη1-η8 mixing from recent measurements of the η→γγ decay.