Observation ofD S ** (2536) meson production by neutrinos in BEBC

Zeitschrift für Physik C Particles and Fields - Neutrino interactions in BEBC produce theD ** (2536) charmed strange meson. The mass of this state is 2534.2±1.2 MeV. The production rate...     

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.     

Trilepton production by neutrinos and antineutrinos

We calculate the electromagnetic and hadronic contributions to neutrino production of μ^?e⁺e^? events and antineutrino production of μ⁺e⁺e^? events. Due to an increase in cross section and acceptance, these rates are much larger in bubble-chamber experiments than the corresponding rates for trimuon events in counter experiments. Verification of these rates would confirm our understanding of the physics behind trilepton events. We stress the importance of measuring also a rate for μ^?e^? events to determine the cross section for the associated production of charmed particles.     

On t-flavour production by neutrinos

Realistic upper bounds for t-quark production by neutrinos and antineutrinos are calculated in the standard six-quark model, including threshold suppression factors and the latest limits on mixing angles. For the presently allowed mass range m_t ? 14 GeV, the production rates in existing neutrino beams are at best marginal, but increase very rapidly with energy. Detection of t-hadrons by semileptonic t-decay is considered; the resulting dimuon signal differs qualitatively from c and $\text{c}$ decay backgrounds, but its separation requires good statistics.     

Fifth quark and dimuon production by neutrinos

It is shown that the recent experiment data on dimuon production by neutrinos and antineutrinos, even with currently available statistics and uncertainties, set a severe upper bound on the semileptonic decay branching ratio of a fifth quark, if any. With this semileptonic branching ratio, production of the b quark is suspicious theoretically.     

Coherent production of photons by neutrinos

The reaction ν+N→ν+N+γ, involving the coherent emission of a photon in a neutrino-nucleus collision, can produce “single shower” events that simulate the reaction ν+e→ν+e. The ratio of coherent photons to electrons (for an ²⁷Al target) is estimated to be 40% at E_ν=20GeV and 10% at E_ν=20 GeV. We examine the extent to which the “excess” of showers seen in the Aachen-Padova experiment could be understood by this mechanism.     

Sources of tetramuon production by neutrinos

We evaluate four sources of tetramuon production by neutrinos: (a) heavy quark cascade, (b) heavy lepton cascade, (c) charm production with radiative pair, (d) charm production plus an associated charm pair. Rates relative to ν→μ^? of order (a) 10^?6, (b) 10^?5, (c) 10^?7, (d) 10^?9, can be obtained. Invariant mass and azimuthal correlation distributions in 4μ events are presented. Relative multimuon rates differ strikingly in the models considered.     

Dilepton and strange particles production by neutrinos in gargamelle

New results are presented of an analysis of pictures taken during an exposure of Gargamelle to the CERN ν beam in 1975. In addition to three ν_μ+N→μ^?+e⁺+V⁰+ hadrons events previously reported, an excess is found of events of the type ν_μ+N→μ^?+e⁺+ hadrons without V⁰. An analysis of strange particle production in charged current events suggests a possible violation of the ΔS=ΔQ rule. Interpreted in terms of charm production, the data permit an estimate of branching ratios and production rate of charmed particles. A limit is also placed on charmed particle production by neutral currents.     

Dilepton and trilepton production by antineutrinos and neutrinos in neon

A sample of over 25,000 fully measured neutrino and antineutrino charged current interactions in BEBC includes 192 dilepton candidates. The prompt signal after subtraction of background is 41 ±7µ⁺ e ^-, 35±7µ⁺µ^- events from \(\bar v\) interactions, and 32±7µ^-µ⁺ events from ν interactions. There are 2 trileptons, µ^-µ^- e ⁺ and µ^-µ^-µ⁺. Results are compared with other experimental data and with the standard model. Limits to prompt like sign µ⁺ e ⁺, µ⁺µ⁺ and µ^-µ^- signals are given and compared with other experiments and with theoretical calculations.     

Observation of charmed baryon production in νp interactions in BEBC

Two examples of charmed baryon production by neutrinos have been observed in BEBC filled with hydrogen. Both events fit uniquely the reaction νp → μ^?pK^?π⁺π⁺ and thus apparently violate the ΔS = ΔQ rule. None of the appropriate mass combinations is consistent with the mass values of the D⁰ and D⁺ mesons. However, for the mass combinations of the pK^?π⁺ systems, values of (2.285 ± 0.005) GeV and (2.280 ± 0.003) GeV are found for event 1 and 2, respectively. These values agree with the mass of (2.285 ± 0.006) GeV for the Λ_c⁺ charmed baryon determined recently in e⁺e^? collisions at SLAC.     

A lower bound on heavy-lepton production by neutrinos

A lower bound on σ(νA→M…) is given, in terms of the structure functions which can most easily be measured in ν+A→μ+… reactions, for heavy leptons (m) of the type required by renormalizable models of weak interactions.     

Lepton assignment in E7 model and multilepton production by neutrinos

We propose a lepton assignment within the frame work of E7 gauge model and show that observed multilepton events by neutrinos can be explained, within this assignment, by the production of a heavy lepton.     

Diffractive production of charmed strange mesons by neutrinos and antineutrinos

The diffractive production of charmed strangeD _s ^* and possiblyD _s mesons by neutrinos and antineutrinos on nucleons in hydrogen, deuterium and neon targets is observed. The slope parameter of thet distribution is 3.3±0.8 (GeV)^?2. The production rate per charged current neutrino interaction with an isoscalar target times the D _s ⁺ →φτ⁺ branching fraction is (1.03±0.27)×10^?4.     

Coherent production ofρ − mesons in charged current antineutrino-neon interactions in BEBC

Coherent production ofρ ^? mesons in charged current antineutrino interactions on neon nuclei is studied in the BEBC bubble chamber exposed to the CERN SPS wide band beam. The cross section is measured to be (95±25)·10^?40 cm² per neon nucleus, averaged over the beam energy spectrum. The distributions of kinematical variables and the absolute value of the cross section are in agreement with theoretical predictions based on the CVC hypothesis and the vector meson dominance model.     

Charged lepton production from iron induced by atmospheric neutrinos

The charged current lepton production induced by neutrinos in ⁵⁶Fe nuclei has been studied. The calculations have been done for the quasielastic as well as the inelastic reactions assuming Δ-dominance and take into account the effect of Pauli blocking, Fermi motion and the renormalization of weak transition strengths in the nuclear medium. The quasielastic production cross-sections for lepton production are found to be strongly reduced due to nuclear effects, while there is about 10% reduction in the inelastic cross-sections in the absence of the final-state interactions of the pions. The numerical results for the momentum and angular distributions of the leptons averaged over the various atmospheric-neutrino spectra at the Soudan and Gran Sasso sites have been presented. The effect of nuclear-model dependence and the atmospheric-flux dependence on the relative yield of μ to e has been studied and discussed.     

Densitometer for measuring densities in range ofD=0 toD=6

An instrument permitting measurement of the density of a photographic film in a range ofD=0 toD=6 has been designed by simply adapting a normal densitometer. The advantages of this equipment are described as well as the possibilities arising for film dosimetry.     

Heavy quark cascade mechanism of tetramuon production by neutrinos in a scale-breaking model

A few neutrino-induced tetramuon events have recently been reported by two experimental groups with a production rate of 10^–6 for( ^{– – + +})/ ( ^–). However, the rate for such events is not yet determined theoretically. In the present paper, we report on a detailed calculation of the rate in the framework of a heavy quark cascade mechanism, using the QCD-improved parton distribution functions parametrized by Buras and Gaemers, which have successfully fitted various experimental data. Our calculation for( ^{– – + +})/ () accords well with the CDHS and FHPRW rate. The computed rate is also in accord with that obtained via the radiative charm model calculation, whereby the normal charm dimuon production is accompanied by a radiative ^{+ –} pair.