O(18) revived: Splitting the spinor

We propose an O(18) theory which is perturbatively unifiable and which accounts for the absence of right-handed families in the low-energy world. The theory predicts a fourth left-handed family as well as four right-handed families at energies near the weak scale. It also implies the existence of eight light neutrinos, all of which contribute to the width of the Z⁰. Cosmological arguments suggest that four of these neutrinos should have masses between 2 and 35 GeV, and that the other four should be much lighter. They also suggest the existence of a doubly charged scalar φ⁺⁺ and a singly charged scalar φ⁺. Dramatic signatures include the production of four right-handed charged leptons and eight right-handed quarks, $\text{Z}{}^0\text{→ v′}{}_{\mathrm{<mtext>R</mtext>}}\text{+}\text{v}\text{′}{}_{\mathrm{<mtext>R</mtext>}}\text{→ v}{}_{\mathrm{<mtext>R</mtext>}}\text{γ +\_}\text{v}{}_{\mathrm{<mtext>R</mtext>}}\text{γ}$, and e⁺e^? → φ⁺⁺ + φ^??. The lightest right-handed charged quark should be surprinsingly long-lived $\text{(τ?10}{}^{\mathrm{?2}}\text{sec}\text{)}$ for a particle of mass ? 100 GeV.     

Tests of real W-boson pair production

The energy spectrum and the angular distribution of the muon in the reaction $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{W}{}^{\mathrm{+}}\text{W}{}^{\mathrm{?}}\text{→}\text{q}\text{q}\text{(}\text{two quark jets}\text{)+μ}{}^{\mathrm{?}}\text{ν}{}_{\mathrm{\mu }}$ are calculated in the framework of the Weinberg-Salam model. It is shown that the signal is well above the conventional backgrounds and thus could provide a clean signature for real W⁺W^? production at LEP energies. Other distributions are briefly described.     

Some properties of heavy lepton families

The simplest four-quark SU(2) ? U(1) models with an anomally-free heavy lepton sector can have two charged heavy leptons and one or two neutral leprons. Such models also explain the rise in R (the ratio of hadronic to muon pair production in e⁺e^? collisions). We study some consequences of different choices of leptonic numbers for L₁ and L₂. In particular, we derive, the leptonic decay width when several final-stae leptons are massive; the cross section for $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{L}{}_1\text{L}{}_2$ production; the branching ratio for $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→}\text{L}{}_2\text{L}{}_2\text{→}\text{e}\text{3μ+}\text{missing energy}$.     

A search for the decay μ → e γ

We report on the final analysis of a search for the decay μ⁺→e⁺γ performed at SIN. No evidence for the existence of the process has been found. An upper limit for the branching ratio of 1.0 × 10^?9 (90% confidence) is presented. The measured positron-photon energy distributions are completely described by the decay $\text{μ}{}^{\mathrm{+}}\text{→}\text{e}{}^{\mathrm{+}}\text{ν}{}_{\mathrm{<mtext>e</mtext>}}\text{ν}{}_{\mathrm{\mu }}\text{γ}$ and accidental coincidences.     

Flavor changing neutral currents and multileptons in e+e- and vμN,vμN

New quarks and new flavor-changing neutral currents give multiple lepton plus hadron final states in e⁺e^-, $\text{v}{}_{\mathrm{\mu }}\text{N,}\text{v}{}_{\mathrm{\mu }}\text{N}$. We observe that (i) e⁺e^- is a favored place to search for their effects through inclusive ratios σ(e⁺e^-+x:σ (μ⁺μ^- +x): σ(e±μ±+x) and same sign leptons e±e±+x, μ±μ±+x,e±μ±+x. Above a new flavor threshold four charged lrpton final states may become important. (ii) Trilepton final states in $\text{v}{}_{\mathrm{\mu }}\text{N,}\text{v}{}_{\mathrm{\mu }}\text{N}$ are not sensitive to the presence of flavor-changing neutral currents. Much more sensitive are the processes $\text{v}{}_{\mathrm{\mu }}\text{N}$ are ⁺e^-+βand (for charm changing neutral currents) $\text{v}{}_{\mathrm{\mu }}\text{N→e}{}^{\mathrm{+}}\text{β}$.     

A search at high energies for antineutrino-electron elastic scattering

We have searched for candidates for the weak neutral leptonic current reaction $\text{ν}{}_{\mathrm{\mu }}\text{+}\text{e}{}^{\mathrm{?}}\text{→}\text{ν}{}_{\mathrm{\mu }}\text{+}\text{e}{}^{\mathrm{?}}$ in the Fermilab 15 ft bubble chamber filled with a heavy neon-hydrogen mix. Based on zero observed events of this type we find the 90% confidence level upper limit for the rate for this reaction relative to the total antineutrino charged current rate to be 3.9 × 10^?4 and, in the Weinberg-Salam model, sin²θ_W ? 0.37.     

Measurement of the parameter η&#x0304; in the radiative decay of the muon as a test of the v-a structure of the weak interaction

The parameter η&#x0304; of muon decay has been measured in the radiative decay $\text{μ}{}^{\mathrm{+}}\text{→}\text{e}{}^{\mathrm{+}}\text{ν}{}_{\mathrm{<mtext>e</mtext>}}\text{ν}\text{?}{}_{\mathrm{\mu }}\text{γ}$ of unpolarized positive muons. The result $\text{η}\text{?}\text{?0.083}$ (68% confidence) or $\text{η}\text{?}\text{= ?0.03±0.10}$ with ρ fixed at $\text{3}\text{4}$ yields an improvement of the previous value by more than a factor of two. An analysis of all data on muon decay that are presently available slightly improves the constraints on the weak coupling constants to: g_s?0.29g_v, g_p?0.27g_v, g_T?0.23g_v and 0.92g_v?g_A?1.2g_v     

A search for monojet events produced by virtual Z0 bosons in e+e− annihalation at petra

A search was performed for the associated production of two different Higgs bosons via a virtual Z⁰ in e⁺e^? annihilation (e⁺e^? → h₁⁰h₂⁰) using the JADE detector at PETRA. This was motivated by the interpretation of the monojet events observed at the CERN p$\text{p}$ collider as anomalous Z⁰ decays into two neutral Higgs bosons (h₁⁰ and h₂⁰), where h₁⁰ is stable and escapes detection while h₂⁰ decays into hadrons. Single- or di-jet events with large momentum imbalance are then expected at PETRA energies. No evidence for such events was found in our data; this excludes h₂⁰ masses in the range of 1 to 21 GeV with 95% CL, if the branching fraction for Z⁰ → h₁⁰h₂⁰ is a larger than one half that for $\text{Z}{}^0\text{→ v}{}_{\mathrm{\mu }}\text{v}{}_{\mathrm{\mu }}$. The possibility that the monojets could originate from supersymmetric higgsino production from Z⁰ decay is also examined.     

The radiative photino decay into a higgsino

The radiative decay of the photino (γ&#x0304;) to a higgsino (H?) is calculated in the minimal supersymmetric electroweak theory coupled to N = 1 supergravity. From the recent analyses on two photon production at PETRA, we find that the possibility that $\text{m}{}_{\mathrm{<mtext>H</mtext><mtext>?</mtext>}}\text{/m}{}_{\mathrm{<mtext>\gamma </mtext><mtext>?</mtext>}}\text{<1}$ is almost excluded, unless $\text{m}{}_{\mathrm{<mtext>\gamma </mtext><mtext>?</mtext>}}\text{?}\text{O}\text{(20)}\text{GeV}$. We also calculated the cross section for $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{-}}\text{→}\text{γ}\text{?}\text{→γ}\text{H}\text{?}\text{+γ}\text{H}\text{?}$ as a function of photon energy.     

On the possibility of a search for a supersymmetric channel of proton decay p→K+ν, with lifetime around 1033 years

A search for a characteristic supersymmetric channel of proton decay, $\text{p}\text{→}\text{K}{}^{\mathrm{+}}\text{ν}$, is discussed in the paper. From calculations of background produced by atmospheric neutrinos, the lifetime $\text{τ(}\text{p}\text{→}\text{K}{}^{\mathrm{+}}\text{ν}\text{)<3×10}{}^{32}\text{y}$ is derived as the upper limit for possible measurements using water-Cherenkov detectors. It is shown that liquid-scintillation detectors have a much better signature for this channel of proton decay.At the same time background produced by atmospheric neutrinos with a signature of $\text{p}\text{→}\text{K}{}^{\mathrm{+}}\text{ν}$ decay in liquid-scintillation detectors is lower and can be further suppressed using some observational criteria.The possibility of searching for $\text{p}\text{→}\text{K}{}^{\mathrm{+}}\text{ν}$ proton decay with lifetime ～10³³ y using a 4–10 kiloton (kt) liquid-scintillation detector is discussed.     

Compilation of coupling constants and low-energy parameters

The electron capture decay ${}^{163}\text{Ho}\text{→}{}^{163}\text{Dy}{}^{\mathrm{<mtext>H</mtext>}}\text{+ν}{}_{\mathrm{<mtext>e</mtext>}}$ occurs with a record low energy release, Q ～ 2.6 keV. The daughter Dy^H atom has an electron hole, H, and predominantly decays by electron ejection Dy^H→Dy^H₁H₂+e^?. We investigate the neutrino mass sensitivity of the electron spectrum in the overall process Ho→Dy^H₁H₂+e^?+ν_e. In this spectrum, the fraction of events sensitive to a fixed non-zero neutrino mass in one to two orders of magnitude smaller than in the standard case of tritium β decay. But the electron energies in ¹⁶³Ho decay are considerably smaller than in ³H decay (Q ～ 18 keV). This suggests experiments whose energy resolution could be much better than that of the magnetic spectrometers conventionally used in the tritium case.     

Search for sleptons and squarks at the Z0 peak in e-e+ colliders

We investigate single scalar lepton and scalar quark production processes $\text{e}{}^{\mathrm{-}}\text{e}{}^{\mathrm{+}}\text{→ Z}{}^0\text{→}\text{?}{}^{\mathrm{\pm }}\text{γ}\text{?}{}^{\mathrm{\pm }}\text{,}\text{q}\text{γ}\text{q}\text{and}\text{q}\text{g}\text{q}$ at the Z⁰ peak. We find that a detectable number of these scalars should be produced at the SLC and LEP-I colliders even if their masses substantially exceed the beam energy E = m_Z/2?45 GeV.     

Effects of neutral weak currents in annihilation

General cross-sections are given for annihilation via one photon and W⁰ exchange. Effects of the W⁰ in the special cases e⁺e^?→μ⁺μ^? and $\text{p}\text{p}\text{→?}{}^{\mathrm{+}}\text{?}{}^{\mathrm{?}}$ at high energies are discussed. These effects are estimated to be comparable to the effects from one γ exchange at energies accesible in NAL and SPS.     

An experimental study of the form factor in the decay K+ → πoe+ν

The q² variation of the factor $\text{?}{}_{\mathrm{+}}\text{(q}{}^2\text{)}$ in the decay K⁺→π⁰e⁺ν has been studied using a sample of even detected in the CERN 1.1 m³ heavy-liquid bubble chamber. The data are consistent with a linear development $\text{?}{}_{\mathrm{+}}\text{(q}{}^2\text{)=?}{}_{\mathrm{+}}\text{(0) (1+λ}{}_{\mathrm{+}}\text{q/m}{}^2{}_{\mathrm{\pi }}\text{)}$ with λ₊=0.027±0.008.     

Anomalous events in e+e−→μ+μ−γ. excited states and/or new interactions?

We first show that the enhancement observed by Cello can neither be explained by real or virtual μ¹ production through μ¹μγ or μ¹μZ couplings nor by μμγγ or μμγZ contact terms, when one imposes the usual constraints from $\text{g -2, e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{→γγ, Z→}\text{ll}\text{γ}$. We then propose an explanation using an eeμμ¹ contact term which is less constrained. In addition to $\text{μ}{}^1\text{→μγ}$ this leads to a direct decay $\text{μ}{}^1\text{→μee}$. Generalized to other types of fermion pairs we have here an interesting source of multifermion anomalous events.     

New upper limit for μ− → e+ conversion

An upper limit for μ^? → e⁺ conversion has been established by searching for specific decay properties of the expected final state nucleus. We obtain $\text{R}{}_{\mathrm{<mtext>coh</mtext>}}\text{= (μ}{}^{\mathrm{?}}\text{+}{}^{127}\text{I →}\text{e}{}^{\mathrm{+}}{}^{127}\text{Sb}{}^1\text{)/(μ}{}^{\mathrm{?}}\text{→ v}{}_{\mathrm{\mu }}\text{) < 3 × 10}{}^{\mathrm{?10}}$ with 90% c.l.     

Positron production by muon neutrinos BEBC filled with a neon-hydrogen mixture

For e⁺ energy > 0.3 GeV and 10 GeV < visible energy < 100 GeV we find that: (i) $\text{? = (v}{}_{\mathrm{\mu }}\text{+}\text{Ne}\text{→ μ}{}^{\mathrm{?}}\text{e}{}^{\mathrm{+}}\text{)/(v}{}_{\mathrm{\mu }}\text{+}\text{Ne}\text{→ μ}{}^{\mathrm{?}}\text{) = (0.41 ± 0.15)\%}$; (ii) 1.2 ± 0.5 neutral strange particles are produced per μ^?e⁺ event; (iii) the lifetime of possible positron-parent particles is < 3 × 10^?10 s (90% C.L.); (iv) the cross section for direct e⁺ production via the neutral current is < 0.2 times that via the charged current (90% C.L.); (v) the cross section for producing heavy leptons, L⁺, decaying into e⁺ … is < 0.7 × 10^?3 times that for μ^?production, implying M(L⁺) > 10 GeV.     

Decays of charmed mesons via color-octet decays of the c-quark

We unify the color-octet weak transitions first studied in cq? annihilation models with the coherence structure of c-quark decay models. We find then, with a dominant c-quark decay contribution, $\text{2.3,?}{}_{\mathrm{\tau }}\text{(}\text{D}{}^{\mathrm{+}}\text{)}\text{τ(}\text{D}{}^0\text{)?3.0}$ and τ(D⁺)≈7.5×10^?13 s, not inconsistent with the trends in the experimental results.     

On the semileptonic decay of charmed hadrons

The semileptonic and leptonic decay modes of charmed hadrons produced in e⁺e^? collisions above 4 GeV in the cm have been investigated by selecting events with a single electron plus at least two charged tracks. The electron momentum spectrum peaks near 0.5 GeV/c with few events above 0.7 GeV/c. The spectrum excludes large rates for the decays $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}$ and $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}\text{π}$, but is compatible with $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}\text{K}{}^1\text{(892)}$, $\text{D}\text{→}\text{e}\text{v}{}_{\mathrm{<mtext>e</mtext>}}\text{K}$ or a mixture of both. The semileptonic branching ratio is obtained both by comparing the inclusive electron cross section with the total cross section attributable to charm, and by studying the fraction of events containing a second electron. The semileptonic charm branching ratios obtained are 0.11 ± 0.03 and 0.16 ± 0.06 respectively. A single event with three electrons and hadrons is found, consistent with the estimated background. The 90% confidence upper limit for σ(e⁺e^? → 3e + hadrons) is 0.1 nb.     

Electromagnetic annihilation of e+e− into quarkonium states with even charge conjugation

We calculate the production of narrow resonances with even charge conjugation ${}^3\text{P}{}_{\mathrm{J}}\text{=1,2}$ in e⁺e^? annihilation in the quarkonium and vectordominance models. We give unitarity bounds for $\text{Γ(}{}^3\text{P}{}_{\mathrm{J}}\text{→ e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{)}$ in terms of $\text{Γ(}{}^3\text{P}{}_{\mathrm{J}}\text{→ γγ)}$ and $\text{Γ(}{}^3\text{P}{}_{\mathrm{J}}\text{→ e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{?}}\text{)}$. The electromagnetic production dominates through the neutral current at low energies independent of details of the model. For masses above 10 GeV the situation is reversed.