An experiment has been performed to search for the muon-and electron-number non-conserving decay µ + → e + γ. The upper limit for the branching ratio is found to be Γ(µ−11 with 90% confidence.13.35.Bv; 11.30.Er; 23.40.Bw

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A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). This apparatus uses superfluid 4 He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized 3 He from an Atomic Beam Source injected into the superfluid 4 He and transported to the measurement cells where it serves as a co-magnetometer. The superfluid 4 He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of 2 − 3 × 10 −28 e-cm, with anticipated systematic uncertainties below this level.

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The MEGA experiment, which searched for the muon-and electron-number violating decay ϩ →e ϩ ␥, is described. The spectrometer system, the calibrations, the data taking procedures, the data analysis, and the sensitivity of the experiment are discussed. The most stringent upper limit on the branching ratio, B( ϩ →e ϩ ␥)Ͻ1.2ϫ10 Ϫ11 with 90% confidence, is derived from a likelihood analysis.

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The (m+, m ) and (m. , m ) reactions were studied on a variety of nuclei at a bombarding energy of 160 MeV. The full m energy spectra were measured with a m spectrometer at several detection angles. The energy spectra and angular distributions are characteristic of quasifree reactions. Effects due to multiple scattering, neutron screening, and Pauli blocking are clearly observed.

Observation of the T +1 component of the isovector monopole and the giant dipole resonances in the reactions 90 Zr and 120 Sn(/r~,7r°) at T^-=165 MeV is reported. The isobaric analog state and T -1 component of the giant dipole resonance in the reaction 120 Sn(/r + , 7T°) were also observed. Excitation energies and widths of the monopole are given.PACS numbers: 24.30.Cz, 24.30.Eb, 25.80.Fm Macroscopic 1 as well as microscopic 2 theories of nuclear structure hypothesize the existence of a collective isovector monopole (IVM) excitation of the nucleus. The possibility of experimentally observing the IVM was discussed as early as 1958 by Danos, 3 who estimated the electroexcitation cross section. Isoscalar collective excitations with angular momentum / = 0, 2, and 3 have been observed and studied in hadron and electron scattering while the isovector dipole or giant dipole resonance (GDR) is a prominent feature of the scattering of electrons and photons from nuclei. Evidence has been given for the observation of the isovector quadrupole resonance. 4 However, at present there is no clear experimental evidence for the IVM. 5 Recently, arguments have been given that the (7r~, 77°) reaction at energies near the (3, 3) resonance might detect the IVM. 6 These arguments are supported by the previously reported observation 7 of the GDR in the (77*, TT°) reactions on 40 Ca. Pion charge-exchange excitation of the IVM is expected to have the following qualitative properties: (1) a zero-degree cross section of a few hundred microbarns per steradian; (2) a forward-peaked angular distribution; and (3) an excitation energy of approximately 170/A l/s MeV in the parent nucleus.Here we report the observation of the IVM in the (ir~9 TT°) reaction at pion kinetic energy 165 MeV on 90 Zr and 120 Sn. Results for 120 Sn(77 + , TT°) are also discussed. The experiments were carried out at the low-energy pion channel at the Clinton P. Anderson Meson Physics Facitity (LAMPF). The LAMPF TT° spectrometer 8 was used to measure the direction and energy of the outgoing 77°. Data were taken at spectrometer angles of 0° and 20° and sorted into several narrower ranges of scattering angle. The spectrometer acceptance and line shape were measured with the reaction n~p -n°n at 165 MeV. The ratio of calculated to measured acceptance was found to be independent of scattering angle to within the 4% statistical errors of the measurement. Figure 1 shows the double-differential cross sections for the reactions 120 Sn(7T + ,7r°) and 120 Sn(7r",7r°) as functions of ir° energy for scattering angles of 4.5°, 6.8% and 11,0°. The isobaric analog state (IAS) is clearly visible in the (fl" + , 77°) data at a 77° energy of 157 MeV. The cross section for excitation of this Z = 0 state is seen to decrease as the scattering angle increases. The IVM is seen in the (77", 77 0 ) data at a 77 0 energy of 150 MeV. The angular dependence is similar to that of the IAS as expected.To perform a quantitative analysis we make the assumption that the double-differential cross secti...