Measurement of the radiative decay of polarized muons in the MEG experiment

We studied the radiative muon decay $\mu^+ \to e^+\nu\bar{\nu}\gamma$ by using for the first time an almost fully polarized muon source. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon decays collected in the MEG experiment in the years 2009--2010 and measured the branching ratio B($\mu^+ \to e^+\nu\bar{\nu}\gamma$) = (6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for $\mu^+ \to e^+\gamma$ process.Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which was recently calculated. Published versio

Large Area ?-thermal Phonon TES Detector Mediated by the quasi-particle Diffusion Signal for Space Application

Low temperature detectors operated at about 0.1K have achieved excellent spectral performances in the soft X-rays, becoming appealing for new challenging measurements with space missions in Astrophysics. In order to exploit their full sensitivity, it is necessary to minimize the background signals generated by the cosmic rays, i.e., high energy protons and light nuclei, that leave sizable amounts of energy in the same spectral window of the astrophysics signals. Detectors for GeV protons and nuclei operating few millimeters from the X-ray detector at 0.1K can act as anti-coincidence to disentangle the fake signal of cosmics. Fast and large detectors are designed and fabricated. These operate by mixing the fast a-thermal phonon signal with the slow diffusive thermal ones. A greater uniformity in the response should be obtained using large shaped superconducting aluminium films that acts as phonon collectors: the quasi-particles created by high energy phonons diffuse along the film toward a small Ir TES sensor giving out to a fast rise time. Here we present the measurement of an operating prototype of a superconducting anticoincidence detector for the proposed space mission ATHENA+

large area superconducting tes spiderweb bolometer for multi mode cavity microwave detect

For the cosmic microwave background, the increase of the sensitivity of present superconducting TES Spiderweb Bolometers can be done coupling them to a large set of modes of the EM radiation inside the cavity. This will require a proper shaping of the horn-cavity assembly for the focal plane of the microwave telescope and the use of large area bolometers. Large area spiderweb bolometers of 8 mm diameter and a mesh size of 250 μm are fabricated in order to couple with approximately the first 20 modes of the cavity at about 140 GHz. These bolometers are fabricated with micro machining techniques from silicon wafer covered with SiO2 – Si3N4 CVD thick films, 0.3 μm and 1 μm respectively. The sensor is a Ti/Au/Ti 3 layer TES sensor with Tc tuned in the 330-380 mK and 2 mK transition width. The TES is electronically coupled to the EM gold absorber that is grown on to the spiderweb mesh in order to sense the temperature of the electron gas heated by the EM radiation. The gold absorber mesh has 5 um beam size over a Si3N4 10 μm beam size supporting mesh. The Si3N4 mesh is then fully suspended by means of DRIE back etching of the Si substrate. Here we present the first results of these large area bolometers

Measurement of the radiative decay of polarized muons in the MEG experiment

We studied the radiative muon decay (Formula presented.) by using for the first time an almost fully polarized muon source. We identified a large sample ((Formula presented.) 13,000) of these decays in a total sample of (Formula presented.) positive muon decays collected in the MEG experiment in the years 2009–2010 and measured the branching ratio (Formula presented.) for (Formula presented.) and (Formula presented.) , consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for (Formula presented.) process

Search for the lepton flavour violating decay μ+→ e +γ with the full dataset of the MEG experiment: MEG Collaboration

The final results of the search for the lepton flavour violating decay μ+→ e +γ based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and totalling 7.5 × 10 14 stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of B(μ+→ e +γ) < 4.2 × 10 - 13 (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date

Search for the lepton flavour violating decay μ+→ e +γ with the full dataset of the MEG experiment: MEG Collaboration

none84siThe final results of the search for the lepton flavour violating decay mu(+) -> e(+)gamma based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009-2013 and totalling 7.5x10(14) stopped muons on target are presented. Nosignificant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of B(mu(+) -> e(+) gamma) < 4.2 x 10(-13) (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date.Baldini, A.M.; Bao, Y.; Baracchini, E.; Bemporad, C.; Berg, F.; Biasotti, M.; Boca, G.; Cascella, M.; Cattaneo, P.W.; Cavoto, G.; Cei, F.; Cerri, C.; Chiarello, G.; Chiri, C.; Corvaglia, A.; de Bari, A.; De Gerone, M.; Doke, T.; D’Onofrio, A.; Dussoni, S.; Egger, J.; Fujii, Y.; Galli, L.; Gatti, F.; Grancagnolo, F.; Grassi, M.; Graziosi, A.; Grigoriev, D.N.; Haruyama, T.; Hildebrandt, M.; Hodge, Z.; Ieki, K.; Ignatov, F.; Iwamoto, T.; Kaneko, D.; Kang, T.I.; Kettle, P.-R.; Khazin, B.I.; Khomutov, N.; Korenchenko, A.; Kravchuk, N.; Lim, G.M.A.; Maki, A.; Mihara, S.; Molzon, W.; Mori, Toshinori; Morsani, F.; Mtchedilishvili, A.; Mzavia, D.; Nakaura, S.; Nardò, R.; Nicolò, D.; Nishiguchi, H.; Nishimura, M.; Ogawa, S.; Ootani, W.; Orito, S.; Panareo, M.; Papa, A.; Pazzi, R.; Pepino, A.; Piredda, G.; Pizzigoni, G.; Popov, A.; Raffaelli, F.; Renga, F.; Ripiccini, E.; Ritt, S.; Rossella, M.; Rutar, G.; Sawada, R.; Sergiampietri, F.; Signorelli, G.; Simonetta, M.; Tassielli, G.F.; Tenchini, F.; Uchiyama, Y.; Venturini, M.; Voena, C.; Yamamoto, A.; Yoshida, K.; You, Z.; Yudin, Yu. V.; Zanello, D.Baldini, A. M.; Bao, Y.; Baracchini, E.; Bemporad, C.; Berg, F.; Biasotti, M.; Boca, Gianluigi; Cascella, M.; Cattaneo, P. W.; Cavoto, G.; Cei, F.; Cerri, C.; Chiarello, G.; Chiri, C.; Corvaglia, A.; DE BARI, Antonio; De Gerone, M.; Doke, T.; D’Onofrio, A.; Dussoni, S.; Egger, J.; Fujii, Y.; Galli, L.; Gatti, F.; Grancagnolo, F.; Grassi, M.; Graziosi, A.; Grigoriev, D. N.; Haruyama, T.; Hildebrandt, M.; Hodge, Z.; Ieki, K.; Ignatov, F.; Iwamoto, T.; Kaneko, D.; Kang, T. I.; Kettle, P. R.; Khazin, B. I.; Khomutov, N.; Korenchenko, A.; Kravchuk, N.; Lim, G. M. A.; Maki, A.; Mihara, S.; Molzon, W.; Mori, Toshinori; Morsani, F.; Mtchedilishvili, A.; Mzavia, D.; Nakaura, S.; Nardo', Roberto; Nicolò, D.; Nishiguchi, H.; Nishimura, M.; Ogawa, S.; Ootani, W.; Orito, S.; Panareo, M.; Papa, A.; Pazzi, R.; Pepino, A.; Piredda, G.; Pizzigoni, G.; Popov, A.; Raffaelli, F.; Renga, F.; Ripiccini, E.; Ritt, S.; Rossella, M.; Rutar, G.; Sawada, R.; Sergiampietri, F.; Signorelli, G.; Simonetta, M.; Tassielli, G. F.; Tenchini, F.; Uchiyama, Y.; Venturini, M.; Voena, C.; Yamamoto, A.; Yoshida, K.; You, Z.; Yudin, Y. u. V.; Zanello, D

Search for the lepton flavour violating decay mu(+) -> e(+) gamma with the full dataset of the MEG experiment

The final results of the search for the lepton flavour violating decay μ+→e+γ based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and totalling 7.5×1014 stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of B(μ+→e+γ)<4.2×10−13 (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date