B−L non-conserving proton decay in guts

It is shown that B?L non-conserving proton decay (p→e^?π⁺π⁺ etc.) is allowed through gauge boson mixing in both SO(10) and E(6) GUTs, but not in the SU(5) GUT. The lifetime for this decay mode is estimated.     

Baryon wave functions and nucleon decay

We apply to nucleon decay the knowledge about the short-distance structure of baryon wave functions gleaned from QCD form factor calculations nd the $\text{J}\text{gY →}\text{p}\text{?}\text{p}$ decay rate. We review the uncertainties arising when current algebra and PCAC are used to relate $\text{N}\text{→}\text{?}\text{+}$ meson decay rates to 〈0|qqq|N〉 matrix elements. We show that the relevant matrix elements are not directly related to those of the leading twist operators “measured” in conventional high momentum transfer physics, but argue for an indirect based on models that fit both form factor and $\text{J}\text{Ψ}$ decay data. We use these inputs to calculate the p → e⁺π⁰ decay rate in minimal SU(5) and other grand unified theories (GUTs) for a specified value of the heavy vector boson mass m_X. Our results combined with the recent experimental lower limit on this mode indicate that m_X > 2 × 10¹⁵ GeV in the minimal SU(5) GUT, and we derive analogous bounds for supersymmetric GUTs. Our calculated lifetime for a given value of m_X is considerably shorter than previous estimates made using non-relativistic SU(6) or the bag model, a difference traceable to the different normalizations of 2 and 3 quark wave functions at short distances.     

Four families of composite quarks and leptons

Four families of composite quarks and leptons, two standard and two non-standard, are found in a unique solution SU(3)_HC × SU(6)_L × SU(6)_R of a restricted 't Hooft anomaly-matching program. Testable predictions emerge, such as prohibition of μ → eγ, zero charge asymmetry in e⁺e^? → τ⁺τ^? in contrast to e⁺e^? → μ⁺μ^?, and a rich new hadron spectrum masses around M_W. A minimal set of spectator fermions contains color-singlet objects with fractional quark-like charges.     

SU(3)×SU(2)×U(1) next-to-leading corrections for proton decay in the SU(5) model

We compute in the standard model of SU(3)^c×(SU(2)×U(1)) with massless quarks and leptons the two-loop anomalous dimensions of the four-fermion operators relevant to proton decay in process involving (u, d, e, ν_e). The calculation is carried out by the use of dimensional reduction, a variant of dimensional regularization. Our aim is to give a complete calculation within the SU(5) GUT model of the next-to-leading enhancement-suppression factor for nucleon decay due to renormalization effects arising from hard gluons, W's and B's in process which involve (u, d, e, ν_e). It turns out that the result is sensitive to the ratios x_(i) = M_{H (i)}/M_X where M_H(i) are the masses of the twelve superheavy Higgs scalars in the $\text{24}$ multiplet which breaks SU(5) → SU(3)×SU(2)×U(1).     

ΔB = −ΔL, neutron →e−π+, e−K+, μ−π+ and μ−K+ decay modes in SU(2)L × SU(2)R × SU(4)col or SO(10)

It is stressed that within the simplest model SU(4) of color, unifying quarks with leptons, where B  L is a gauge symmetry, a spontaneous breaking of this symmetry leads naturally to baryonlepton decays like n→e^?k⁺, e^?K⁺, μ^?π⁺, μ^?K⁺ [in constant to SU(5) where B  L is not gauged]. Our mechanism is crucially tied to the presence of the Higgs multiplet (2, 2, 15) of SU(2) × SU(2) × SU(4), which is needed to account for the observed quarklepton mass ratios.     

SU(2)×U(1) effects in e+e− annihilation: Generalized charge asymmetry

The observability of the SU(2)×U(1) electroweak charge asymmetry effects in e⁺e^? annihilation at $\text{s}\text{=29}\text{GeV}$ is addressed in the context of a Feynman-Field type fragmentation model. We assume three colors of five flavored quarks and one heavy lepton τ. We neglect, at this time, the hard gluon bremsstrahlung events. We take b→c+X as the b-decay mode and we assume all τ's and heavy hadrons decay within the resolution of the detector so thatonly light hadrons and leptons are detected. Allowing all these decays to occur, we then compute the expected front-back asymmetry of negatively charged particles weighted with zⁿ for z?0.0175, where n = 0.5, 1…, 7, 10, and z is the light-cone momentum fraction. We find, for example, that such an asymmetry is ≈5% for n=2for sin²θ_w=0.236 and Λ_{QCD=0.34 GeV}. In other words, due to the large number of charge particles produced per event, this SU(2)×U(1) charge asymmetry may be accessible experimentally in e⁺e^? → X already at PEP and PETRA energies.     

Baryon poles in proton decay amplitudes

The decay rate of the p→π⁰e⁺ mode is calculated in SU(5) grand unified theory using a pole model with proton and $\text{1}\text{2}{}^{\mathrm{?}}$ baryon poles. Baryon-to-vacuum amplitudes are calculated in the framework of the MIT bag model. It is found that the partial decay rate [～(5×10³¹ yr)^?)] is close to the partial decay rates calculated by different methods.     

Electroproduction final states as ω → 1

The successful model of Barbour and Moorhouse for pion photoproduction is extended to electroproduction and combined with recent ideas on configuration mixing or SU(6) breaking in deep inelastic electroproduction as ω → 1. We find that two consequences obtain in the current fragmentation region as ω → 1: (a) the missing mass spectrum in ep → eπ^?X and en → eπ⁺X will be featureless (phase space); (b) in ep → eM^+,0X and en → eM^0,?X for any non-strange meson M the missing hadron system will contain only octets. Hence, in particular, ep → eπΔ will vanish relative to ep → eπ⁺n as ω → 1. For K production only Λ and no Σ final states will be produced.     

Limits for short-lived neutral particles emitted in μ+ or π+ decay

In the data taken for the μ⁺ → e⁺e⁺e^- and π⁺ → e⁺νe⁺e^- experiments a search was made for neutral particles φ produced in the decay μ⁺ → e⁺φ or π⁺ → e⁺νφ with subsequent decay φ → e⁺e^-. No candidates were found, Upper limits for the branching ratios are given as a function of their masses and lifetimes. For lifetimes below 10⁻¹⁰ s limits down to 2 × 10⁻¹² are obtained.     

Polarization amplitudes fore + e − →W + W − ande + e − →ZZ

The main purpose of this work is to study the three weak boson vertex. We give explicit formulae for all polarization amplitudes of the processese ⁺ e ^? →W ⁺ W ^? ande ⁺ e ^? →ZZ, with arbitrary couplings between the various intermediate vector bosons. Using these expressions we discuss possible signatures ofC, P andT violation in the three vector boson coupling, as well as the effects of anomalous magnetic dipole and electric quadrupole moments ofW ^±. The amplitudes for the above processes in any SU(2) × U(1) and SU(2)_L × SU(2)_R × U(1) gauge theory are also given, while the special case of the Weinberg-Salam model is studied in detail.     

Electron-positron annihilation into two and three photons around the ψ

We study the effect of the direct decay of a ψ into three photons on electron-positron annihilation into two and three photons. In a charmonium-like bound state model we find a clear effect in e⁺e^? → 3γ and a somewhat less pronounced effect in e⁺e^? → 2γ, the actual size depending strongly on the charge of the ψ constituents. The effect is reduced when we take initial state radiative corrections into account.     

Measurement of the ω, ρ → π0 e + e − branching fractions

The e ⁺ e ^? → ω, ρ → π⁰ e ⁺ e ^? processes have been investigated in the experiments with Spherical Neutral Detector at the VEPP-2M e ⁺ e ^? collider. The measurements provide the probability ?(ω → π⁰ e ⁺ e ^?) = (0.761 ± 0.053 ± 0.064) × 10^?3 of the ω → π⁰ e ⁺ e ^g- conversion decay and the upper limit ?(ρ → π⁰ e ⁺ e ^?) < 1.2 × 10^?5 (at 90% CL) for the ρ → π⁰ e ⁺ e ^? decay. The transition form factor was measured at three values of the 4-momentum transfer squared.     

Measurement of the ϕ → π0 e + e − decay probability

The measurement of the ? → π⁰ e ⁺ e ^? conversion decay probability on the SND detector at the VEPP-2M e ⁺ e ^? collider gave the value Br(? → π ⁰ e ⁺ e ^?) = (1.01 ± 0.28 ± 0.29) × 10^?5.     

Semi-simple unification on T/Z12 orientifold in the type IIB supergravity

The semi-simple unification model based on SU(5)_GUT×U(3)_H gauge group is an interesting extension of the minimal SU(5)_GUT grand unification theory (GUT), since it solves the two serious problems in the standard GUT: the triplet–doublet splitting problem and the presence of dangerous dimension five operators for proton decay. Here, the extra U(3)_H gauge interaction plays a crucial role on the GUT breaking. In this Letter, we show that the full multiplet structure of the U(3)_H sector required for the desired GUT breaking is reproduced naturally on T⁶/Z₁₂ orientifold in the type IIB supergravity with a D3–D7 system. The SU(5)_GUT vector multiplet lives on D7-branes and the U(3)_H sector resides on D3-branes. We also show that various interesting features in the original SU(5)_GUT×U(3)_H model are explained in the present brane-world scenario. A possible extension to the type IIB string theory is also discussed.     

The process e + e − → ωπ0 near the Φ resonance

The reaction e ⁺ e ^?→ωπ⁰ near a Φ resonance was studied with a spherical neutral detector at VEPP-2M e ⁺ e ^? collider. Both main modes of decay of a ω meson were investigated: ω→π⁺π^?π⁰ and ω→π ⁰γ. The probability of decay Φ→ωπ⁰ was obtained from the magnitude of the interference wave in the cross section for the reaction e ⁺ e ^?→ωπ⁰→ π⁺π^?π⁰π⁰: B(Φ→ωπ⁰) = (5.5 _?1.4 ^+1.6 ±0.3) ×10^?5. The ratio of the partial widths of the ω meson was obtained from the ratio of the cross sections for the two modes: Γ(ω→π⁰γ )/Γ(ω→π⁺π^?π⁰) = 0.0994 ± 0.0036 ± 0.0038.     

Effects of additional Higgses in supersymmetric grand unified theories

We consider modifications of the minimal supersymmetric SU(5) grand unified model. With the additional Higgses 10 +$\text{10}$, the theory may be modified so that the proton decays dominantly via the conventional mode p→e⁺π with the lifetime π_p=(0.04-710)×10³⁰yr, and sin²θ_W=0.222±0.003.     

Z0 decay into neutralinos and the Higgs fermion mass mH

The Z⁰ decay width into neutralinos is calculated in the minimal supersymmetrics SU(2) × U(1) model. In some region of the parameters space “jet(s) + missing” and “ℓ⁺ℓ⁻ + missing” events at SPS are predicted with a ratio 5 : 1. If neutralino signals are not found at LEP and SLC, we can get a lower bound on m_H independently of all other parameters.     

Deep-inelastic one-particle inclusive processes in the parton model

We study the processes e + N → e′ + h + anything, e⁺ + e^? → h + anything, within the parton model of Landshoff, Polkinghorne and Short. Definite and peculiar predictions are obtained, also common to the Drell, Levy and Yan cut-off theory and to the λφ³ ladder model. These predictions can be summarized as follows: (i) in the photon fragmentation region the cross section factorizes after integration over transverse momentum of h; (ii) in the target fragmentation region Regge behaviour, valid at large ω, gives rise to double Regge exchange for small values of the Feynman variable y, but only up to $\text{y ??1/ω}$; (iii) the structure functions vanish at y = 0; (iv) total multiplicities in the first process increase like 1n ω for large ω, and in the second reach a finite limit at large q².In the case where only one SU(3) multiplet of partons is present (as in the quark parton model) unique relations, valid in the limit of exact SU(3), are found between the cross section and multiplicities in the first process and the analogous quantities for the forward region of the second process.     

Electromagnetic transition form factors of Λ → <Emphasis Type="Italic">ne</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> weak dilepton decay

Weak radiative decay Λ → ne⁺e^? depends in general on four independent electromagnetic transition form factors. These form factors can be fixed in an extended model of dominance of vector mesons, where the asymptotic behavior of form factors is in agreement with quark counting rules. The dependence of the branching ratio of the Λ → ne⁺e^? decay on the relative weight of four electromagnetic form factors is investigated.     

On W±, Z0, γ self-interactions: High energy behaviour and tree unitarity bounds

We analyze the high-energy behaviour of vector boson scattering amplitudes within the framework of a recently suggested lagrangian model based on global weak isospin symmetry broken by electromagnetism. Requiring vanishing of the most strongly (as s²) rising contribution to vector boson scattering amplitudes leads to vector boson self-interactions dependent on a single parameter, for which the anomalous W^± magnetic moment, κ, can be chosen. Tree unitarity is violated at about 2 TeV for arbitrary κ as in the SU(2)_L × U(1)_Y theory for m_H → ∞. The model is well suited for significant tests of the vector boson sector of the SU(2)_L × U(1)_Y electroweak theory in processes such as e⁺e⁻ → W⁺W⁻.