Measurement of the TeV atmospheric muon charge ratio with the complete OPERA data set

The OPERA detector, designed to search for νμ→ντ oscillations in the CNGS beam, is located in the underground Gran Sasso laboratory, a privileged location to study TeV-scale cosmic rays. For the analysis here presented, the detector was used to measure the atmospheric muon charge ratio in the TeV region. OPERA collected charge-separated cosmic ray data between 2008 and 2012. More than 3 million atmospheric muon events were detected and reconstructed, among which about 110000 multiple muon bundles. The charge ratio Rμ≡Nμ+/Nμ- was measured separately for single and for multiple muon events. The analysis exploited the inversion of the magnet polarity which was performed on purpose during the 2012 Run. The combination of the two data sets with opposite magnet polarities allowed minimizing systematic uncertainties and reaching an accurate determination of the muon charge ratio. Data were fitted to obtain relevant parameters on the composition of primary cosmic rays and the associated kaon production in the forward fragmentation region. In the surface energy range 1–20 TeV investigated by OPERA, Rμ is well described by a parametric model including only pion and kaon contributions to the muon flux, showing no significant contribution of the prompt component. The energy independence supports the validity of Feynman scaling in the fragmentation region up to 200  TeV/nucleon primary energy

Observation of tau neutrino appearance in the CNGS beam with the OPERA experiment

The OPERA experiment is searching for oscillations in appearance mode, i.e., via the direct detection of leptons in charged-current interactions. The evidence of appearance has been previously reported with three candidate events using a sub-sample of data from the 2008–2012 runs. We report here a fourth candidate event, with the decaying into a hadron, found after adding the 2012 run events without any muon in the final state to the data sample. Given the number of analyzed events and the low background, oscillations are established with a significance of 4.2

Limits on muon-neutrino to tau-neutrino oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam

The OPERA experiment, exposed to the CERN to Gran Sasso ν μ beam, collected data from 2008 to 2012. Four oscillated ν τ Charged Current interaction candidates have been detected in appearance mode, which are consistent with ν μ → ν τ oscillations at the atmospheric Δ m 2 within the “standard” three-neutrino framework. In this paper, the OPERA ν τ appearance results are used to derive limits on the mixing parameters of a massive sterile neutrino

Measurement of branching fractions for B J / K decays and search for a narrow resonance in the J / final state

We report an observation of the and decays using pairs collected at the resonance with the Belle detector at the KEKB asymmetric-energy collider. We obtain the branching fractions and . We search for a new narrow charmonium(-like) state in the mass spectrum and find no significant excess. We set upper limits on the product of branching fractions, , at where a -odd partner of may exist, at and assuming their known mass and width, and over a range from 3.8 to . The obtained upper limits at 90 confidence level for , , and are , , and , respectively

Search for B decays to final states with the η c meson

We report a search for B decays to selected final states with the η c meson: B ± → K ± η c π + π − , B ± → K ± η c ω , B ± → K ± η c η and B ± → K ± η c π 0 . The analysis is based on 772 × 10 6 B B ¯ $$B\overline{B}$$ pairs collected at the Υ(4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e − collider. We set 90% confidence level upper limits on the branching fractions of the studied B decay modes, independent of intermediate resonances, in the range (0 . 6–5 . 3) × 10 −4 . We also search for molecular-state candidates in the D 0 D ¯ ∗ 0 − D ¯ 0 D ∗ 0 , D 0 D ¯ 0 + D ¯ 0 D 0 $${D}^0{\overline{D}}^{\ast 0}-{\overline{D}}^0{D}^{\ast 0},{D}^0{\overline{D}}^0+{\overline{D}}^0{D}^0$$ and D ∗ 0 D ¯ ∗ 0 + D ¯ ∗ 0 D ∗ 0 $${D}^{\ast 0}{\overline{D}}^{\ast 0}+{\overline{D}}^{\ast 0}{D}^{\ast 0}$$ combinations, neutral partners of the Z (3900) ± and Z (4020) ± , and a poorly understood state X (3915) as possible intermediate states in the decay chain, and set 90% confidence level upper limits on the product of branching fractions to the mentioned intermediate states and decay branching fractions of these states in the range (0 . 6–6 . 9) × 10 −5