Study of some rare decays of the K+ meson

In a search for very rare decays of the K⁺ meson we observed the K⁺→μ⁺νe⁺e^? and K⁺→e⁺ν e⁺e^? modes with branching ratios of (10±3) ×10^?7 and (2⁺²_?2)×10^?7 respectively. We also put new limits on a decay allowed by the alternate scheme of lepton conservation K⁺→π^?μ⁺e⁺, on a decay with double charged weak current K⁺→π^? e⁺e⁺ and on other forbidden decays K⁺→μ^?νe⁺e⁺ and K⁺→π⁺μ^±e^±.     

Single weak boson production in electron-positron annihilation

The cross sections for the process,e ⁺ e ^?→W ^±+hadrons are estimated extensively at the lowest order in the minimal gauge theory ofSU(2) _L ×U(1). It is pointed out that our result on the angular distribution is not compatible with the result reported by Neufeld.     

Observation of possible production and decay of short-living heavy neutral particles in the SKAT neutrino experiment

In the SKAT bubble chamber neutrino experiment production of a short-living neutral particle with mass (1.4?m?2.5) GeV/c² and lifetime τ≈6×10^?12 s has been detected. The event may be interpreted as production and decay of the heavy lepton M⁰→μ^?+e⁺+ν_e with mass (1.4?m_M⁰?2.1) GeV/c². It might also be the production of a charmed particle D⁰→e⁺+τ^?+ν_e (D⁰→e⁺+π^?+ν_e) with mass 1.4?m_D⁰?2.5) GeV/c² in a non-diagonal neutral current. The probability to interpret the event as other possible processes is very low.     

Lepton charge and model of weak interactions with μ-e transitions

The gauge model of weak interactions is proposed and μ^±?e^? transitions predicted by the model are discussed. Estimates are given for μ^±→e^? transitions on hadrons like K⁺→π^?μ⁺e⁺ with Γ (K⁺→π^?μ⁺e⁺) ? 10^?11Γ(K⁺ and μ^? capture on nuclei with W(μ^?→e⁺) ? 10^?12W(μ^? → ν). Single μ^± production in e^? beams with a cross section δ ～ 10^?42?10^?41 cm² is predicted.     

Natural left-right symmetry,atomic parity experiments and asymmetries in high energy e+e− collisions in petra and pep regions

The previously proposed left-right-symmetric SU(2)_L × SU(2)_R × U(1) theory permits one of the two neutral gauge particles N₁ and N₂ to be particularly light (<mW⁺_L) compatible with all neutrin-data and the present atomic parity experiments. Distinguishing features of this theory (with the light mass solution) for e^?e⁺ → μ⁺μ^? and π⁺π^? at PETRA and PEP energies as compared to the SU(2) × U(1) predictions are given.     

A light neutral intermediate vector boson without large e+e−→ μ+μ− asymmetries

An effective SU(2)×U(1)×U(1)' electroweak theory is shown to permit the occurence of a pair of neutral intermediate vector bosons with masses 40 GeV?m_light?70 GeV, m^W.S._Z⁰<m_heavy?100 GeV. Neutrino neutral current interactions are shown to be the same as in the standard electroweak model, and e⁺e^?→μ⁺μ^? forward-backward asymmetries are within experimental bounds for m_light?40 GeV.     

Non-standard Higgs bosons inSU(2)×U(1) radiative corrections

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,v _μ e-scattering, ande ⁺ e ^?→μ ⁺ μ ^?,τ ⁺ τ ^? with longitudinal polarization at PETRA and LEP/SLC energies. It is found that large effects occur in theM _W ?M _Z mass relation, the determination of sin² θ _w 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.     

Hyperfeinstrukturuntersuchung des 6p 2 P 3/2-Terms im Au I-Spektrum durch Resonanzstreuung von Licht

From about 6×10⁶ stoppingK ^?-meson reactions in the Saclay 80 cm hydrogen bubble chamber 70Σ ^?→Λe^?¯ν and 11Σ⁺→Λe⁺ν decays have been identified. The ratio of the vector to axial vector coupling constant has been determined,f ₁/g ₁=?0.22±0.28, consistent with the predictionf ₁=0 of the CVC-theory. The branching ratios for the two decay modes are,Γ(Σ ^?→Λe^?ν)/Γ(Σ^?→ all modes)=(0.69±0.12). 10^?4,Γ(Σ⁺→Λe⁺ν)/Γ(Σ⁺→ all modes)=(0.29±0.10). 10^?4. The ratio, Γ(Σ⁺→Λe⁺)/Γ(Σ^?→Λe^?v)=0.69±0.18, agrees with the phase space ratio, 0.61, therefore a theory that includes no second class currents is consistent with the data.     

Must the new heavy lepton have it's own neutrino?

We consider a minimal gauge theory of leptons, including only e, μ, the newly found charged lepton L and two massless two-component neutrinos.The model implies muon number non conservation. The present limit on μ+Nucleus→e+Nucleus leads to a branching ratio for μ→eγ not larger than 1.7 × 10^?12. Striking violations of μ?e universality in L decays are predicted.     

Bounds on the masses of neutral generation-changing gauge bosons

The existence of several generations of quarks and leptons suggests the possibility of a gauge symmetry connecting the different generations. The neutral gauge bosons of such a scheme would mediate rare processes such as K_L⁰→μ^±, K⁺→π⁺e^?π⁺, μN→eN and would contribute to ΔM(K_S⁰?K_L⁰). We study these and other processes within a simple theoretical framework and derive bounds involving the masses and coupling constants of the generation-changing gauge bosons and various generation-mixing angles. The lower bounds for the relevant masses lie in the 10–100 TeV region. Various remarks concerning the relevance of these bounds to currently popular theoretical ideas and to future experiments are presented.     

Phenomenology of Σ+→pℓ+ℓ− and the structure of the weak non-leptonic Hamiltonian

The problem of the radiative non-leptonic weak baryon decays is reviewed in light of the new experimental findings. With the aim of exploring the structure of the weak non-leptonic Hamiltonian, we present a detailed phenomenological analysis of Σ⁺→p?⁺?^? transitions. Lower and upper limits for rates derivable with standard physics are determined as Γ(Σ⁺→pe ⁺ e ^?)/Σ⁺→pγ)≧7.2×10^?3 and 1/1210? Γ(Σ⁺→pe ⁺ e ⁺)/Γ(Σ⁺→pe ⁺ e ^?)?1/120. From existing data on Σ⁺→pe ⁺ e ^? we obtain limits on the values of the charge radius form factors |c ₁/b ₁|?5;|c ₂/b ₁|? 10, where the magnetic form factor is given by the Σ⁺→dγ, decay asb ₁(0)= 6.9±0.9 MeV. The short distance contribution of the QCD corrected single quarks→dλ transition is shown not to play a dominant role in these decays.     

Limits on the τ neutrino electromagnetic properties from single photon searches ate + e − colliders

We set limits on the magnetic moment and charge radius of the τ neutrino by examining the contributions to the processe ⁺ e ^?→v \(\bar \nu \) γ due to such interactions. We find thatK(ν_τ)<4×10^?6 (i.e.μ(ν_τ)<4×10^?6μ _B , μ _B =e/2m _e ) and 〈r ²〉<2×10^?31 cm² using the combined data of the MAC, ASP, CELLO, and Mark J collaborations for this process. We briefly discuss whether these bounds can be improved in any futuree ⁺ e ^? experiments.     

New measurements of the radiative decay modes of the φ-meson

The radiative decay models of the φ-meson have been studied: e⁺e^?→φ→ηγ→3γ; e⁺e^?→φ→π^oγ→3γ. Cross sections σ_{φ→ηγ→3γ} and σ_{φ→π^oγ→3γ} have been measured at five energies in the φ-meson energy region and clearly show the φ-resonance in the ηγ → 3γ mode as well as in the π^oγ → 3γ mode. From a Breit-Wigner fit to the experimental data the values of the branching ratios are deduced: B_φ→ηγ = (1.5 ± 0.4) × 10^?2; B_φ→π^oγ = (1.4 ± 0.5) × 10^?3.     

Search for rare φ decays in π+π−γ final state

A search for φ radiative decays has been performed using a data sample of about 2.0 million φ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From the selected e⁺e⁻→π⁺π⁻γ events the following results were obtained:B(φ→f₀(980)γ)<1×10⁻⁴ for destructive andB(φ→f₀(980)γ)<7×10⁻⁴ for constructive interference with the Bremsstrahlung process respectively,B(φ→γ→π⁺π⁻γ)<3×10⁻⁵ for E_γ>20 MeV,B(φ→ργ)<7×10⁻⁴. From the selected e⁺e⁻→μ⁺μ⁻γ eventsB(φ→μ⁺μ⁻γ)=(2.3±1.0)×10⁻⁵ has been obtained for E_γ>20 MeV. The upper limit on the P,CP-violating decay η→π⁺π⁻ has also been placed:B(η→π⁺π⁻)<9×10⁻⁴. All upper limits are at 90% C.L.     

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.     

The e + e −→π0π0γ process below 1.0 GeV

The e ⁺ e ^?→π⁰π⁰ γreaction was studied in the energy range 0.36–0.97 GeV on a VEPP-2M e ⁺ e ^? collider with an SND detector. The decay probabilities were found to be B(ω→ π⁰π⁰γ)= (7.8 ±2.7±2.0)×10^?5 and B(π→ π⁰π⁰γ)= (4.8 _?1.8 ^+3.4 ±0.2)×10^?5.     

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.     

Study of the ρ, ω, ϕ→ηγ→7γ decays with an SND detector on a VEPP-2M collider

The e ⁺ e ^?→ηγ→7γ process was studied in the energy range 2E=600–1060 MeV with an SND detector on a VEPP-2M e ⁺ e ^? collider. The decay branching ratios B(φ→ηγ)=(1.353±0.011±0.052)×10^?2, B(ω→ηγ)=(4.62±0.71±0.18)×10^?4, and B(ρ→ηγ)=(2.73±0.31±0.15)×10^?4 were measured.     

Multihadronic decays and partial widths of the J/Ψ (3100) resonance produced in e+e− annihilation at adone

The reactions e⁺e^?→ hadrons and e⁺e⁺e^?→e⁺e^? have been studied at the J/gY (3100) resonance). The relative weights of the topological cross sections for fixed charged multiplicity are σ₂=(32±5)%, σ₄=(49±8)%, σ₆=(18±3)%, and σ₈=(1±0.6)%. The average pion multiplicities are 〈n_ch〉=3.8±0.3 and 〈n_{π^o〉=3.1±0.8}. The decay widths are Γ_e=(4.6±0.8) keV, Γ_h=(59±24) keV, and Γ=(68±26) keV.     

Study of the process e + e − → π+π− in the energy region 400 < \sqrt s < 1000 MeV^\P

The cross section of the process e ⁺ e ^? → π⁺π^? was measured in the spherical neutral detector experiment at the VEPP-2M collider in the energy region $400 < \sqrt s < 1000 MeV$ . This measurement was based on about 12.4 × 10⁶ selected collinear events, which include 7.4 × 10⁶ e ⁺ e ^? → e ⁺ e ^?, 4.5 × 10⁶ e ⁺ e ^? → π⁺π^?, and 0.5 × 10⁶ e ⁺ e ^? → μ⁺μ^? selected events. The systematic uncertainty of cross section determination is 1.3%. The ρ-meson parameters were determined as m _ρ = 774.9±0.4±0.5 MeV, Γ _ρ = 146.5±0.8±1.5 MeV, and σ(ρ → π⁺π^?) = 1220 ± 7 ± 16 nb and the parameters of the G-parity suppressed decay ω → π⁺π^? as σ(ω → π⁺π^?) = 29.9 ± 1.4 ± 1.0 nb and φ_ρω = 113.5±1.3±1.7°.