Search

Physical review / D 13(11), 2934 - 2943 (1976). doi:10.1103/PhysRevD.13.2934, Published by Inst., Woodbury, NY

A search has been performed for the muon-number--violating decay ..mu -->..e/sup +/e/sup +/e/sup -/. No candidate event has been found, the result yielding an upper limit for the branching ratio of B/sub mu3e/ ..e/sup +/e/sup +/e/sup -/..nu../sub e/nu-bar/sub ..mu../ events, eleven such events were observed. They agree in number and spectra with expectations based on standard electroweak theory.

We describe a new neutrino (ν) detection technique which greatly enhances signal-to-noise ratios (S/N) for a variety of experiments with medium energy neutrino beams. This technique involves the simultaneous detection of a lepton and a neutron in various final states of ν induced interactions. We take as an example the reaction νep→e+n and demonstrate the feasibility of detecting the neutron in fast (≲ 30 ns) time coincidence with the positron trigger. The detection efficiency for 1–3 MeV neutrons by proton recoil in a liquid scintillator test module is shown to be 40%. Monte Carlo studies indicate an e±n detection efficiency of 6% for a sample 6.1 ton detector, to be compared with an e+ only detection efficiency of 32%. Cosmic ray and beam induced background rates are reduced by over a factor of 200, improving S/N by a factor of 40. We show that this sample detector, consisting of walls of liquid scintillator modules interspersed with drift chambers and surrounded by active anti-coincidence and passive shielding, can achieve the same sensitivity to νep→e+n as a detector three times its size. We point out the utility of such a detector for various potential neutrino experiments and facilities; i.e., the proposed High Intensity Los Alamos Neutrino Facility.

From a muon-proton scattering experiment with a streamer chamber at the Stanford Linear Accelerator we present results in the ranges 0.3 .. ..mu..pV where V is a vector meson (rho/sup 0/, ..omega.., or phi). It is shown that in rho production the skewing parameter and the longitudinal-transverse ratio change significantly as Q/sup 2/ increases above 1 GeV/sup 2/. The cross section for rho/sup 0/ production as a function of Q/sup 2/ falls below the vector-meson-dominance prediction. The ratio of the cross section for exclusive vector-meson production to the total cross section falls by a factor of 10 between photoproduction and a Q/sup 2/ of 2 GeV/sup 2/, yet the ratio of ..omega.. to rho production remains constant at the photoproduction value out to Q/sup 2/ > 2 GeV/sup 2/.

Based on approximately 10 000 inelastic muon scatters in a liquid deuterium target, we extract charged-hadron multiplicities and topological cross sections for events off the neutron in a range 0.3 < or = Q/sup 2/ < or = 4.5 GeV/sup 2/, 2.0 < or = W < or = 4.6 GeV. We find no significant changes in the multiplicity or topological fractional cross sections over the Q/sup 2/ range of our experiment. Empirically the average multiplicity off a neutron target is equal to that off a proton target over the Q/sup 2/ and W range of our experiment.

A search has been performed for the decays μ → eee, μ → e γ , and μ → eγγ with a sensitivity in the branching ratios at the level of 10 −10 . The experiment used a separated, 26 MeV/c μ + beam with an average intensity of 300kHz. A total of 2.2 × 10 11 muon decays were examined for the present result. The detector for the experiment Is the Crystal Box, which consists of a cylindrical drift chamber surrounded by 396 NaI(T1) crystals. A layer of scintillation counters in front of the crystals provided timing for electrons and a veto for photons. The energy resolution for electrons and photons is ≈6% (FWHM). The position resolution of the drift chamber is 350 μm leading to a vertex cut with a rejection of 10 3 for μ → eee. The timing resolution is ≈300 ps from the scintillators and ~1 ns from the crystals. No candidate for μ → eee has been found, yielding an upper limit for the branching ratio of B μ 3e −10 (90% C.L.).

We report the results of an experiment which examines the entire final state of events in which muon pairs were produced in 15.5-GeV/c ..pi../sup + -/p interactions. A portion of this data was presented earlier. Here we report on the final data sample of 890 events obtained from a total of 2.5 x 10/sup 8/ interactions (a sensitivity of (8.65 events/nb) x trigger efficiency). The experiment was sensitive primarily to the low-mass region and the good mass resolution made it possible to identify the contributions from the rho and ..omega.. decays and the eta and ..omega.. Dalitz decays. An excess of events is observed in the dimuon mass region approx.400 -- 600 MeV which is not accounted for by the above-mentioned decays. The final states were examined to search for characteristic differences from those in events without dimuons.

A clear, prompt dimuon signal has been observed in a low-statistics streamer-chamber experiment with 16-GeV/c $\ensuremath{\pi}p$ interactions. The good mass resolution makes it possible to identify the contributions from $\ensuremath{\rho}$ and $\ensuremath{\omega}$ decays and $\ensuremath{\eta}$ and $\ensuremath{\omega}$ Dalitz decays. An excess of events is observed in the mass region \ensuremath{\sim}400-600 MeV which is not accounted for by the above-mentioned decays.

We present the fractional energy distributions for positive and negative hadrons produced in muon-proton and muon-neutron scattering, and ensuing charge ratios for the photon fragmentation region. Data presented for a center-of-mass energy range $2.8lWl4.5$ GeV and a virtual-photon mass-squared range $0.5\ensuremath{\le}{Q}^{2}\ensuremath{\le}4.5$ ${\mathrm{GeV}}^{2}$ indicate an overall equality of summed structure functions for neutron and proton targets, which exhibit approximate independence of ${Q}^{2}$ and ${\ensuremath{\omega}}^{\ensuremath{'}}$, Implications in terms of quark-fragmentation ideas are discussed.

We report on mean hadron multiplicites and structure functions observed in muon--proton collisions at 14 GeV/c. A remarkable agreement is found with photoproduction and e$sup +$e$sup -$ annihilation data. (AIP)

The Drell-Yan contribution to the massive lepton-pair production in hadron-hadron scattering is calculated using the parton distributions extracted from deep inelastic eN and νN scattering data. The calculated cross sections at BNL energy agree well with the measured data.

A search has been performed for the decays μ → eee, μ → eγ, and μ → eγγ with a sensitivity in the branching ratios at the level of 10−10. The experiment used a surface muon beam at LAMPF with an average intensity of 300 kHz. A total of ≳1011 muon decays was examined for the present result. The detector for the experiment is the Crystal Box which consists of a cylindrical drift chamber surrounded by 396 NaI(T1) crystals. A layer of scintillation counters in front of the crystals provided timing for electrons and a veto for photons. The energy resolution for electrons and photons is ∼6% (FWHM). The position resolution of the drift chamber is 350 μm leading to a vertex cut with a rejection of 103 for μ → eee. The timing resolution is ∼400 ps from the scintillators and ∼1 ns from the crystals. From these values, the eee and eγγ limits are expected to be background free.

Physical review letters 37(2), 85 - 88 (1976). doi:10.1103/PhysRevLett.37.85, Published by APS, College Park, Md.

A search has been performed for the muon-number-violating decay ..mu.. ..-->.. e/sup +/e/sup +/e/sup -/. No candidate event has been found, yielding an upper limit for the branching ratio of B/sub ..mu..3e/ .. e/sup +/e/sup +/e/sup -/ anti nu/sub ..mu../nu/sub e/ events, 11 such events were observed. They agree in number and spectra with expectations based on standard electroweak theory. 9 references.