Recent developments of the nuclear emulsion technology led to the production of films with nanometric silver halide grains suitable to track low energy nuclear recoils with submicrometric length. ...This improvement opens the way to a directional Dark Matter detection, thus providing an innovative and complementary approach to the on-going WIMP searches. An important background source for these searches is represented by neutron-induced nuclear recoils that can mimic the WIMP signal. In this paper we provide an estimation of the contribution to this background from the intrinsic radioactive contamination of nuclear emulsions. We also report the neutron-induced background as a function of the read-out threshold, by using a GEANT4 simulation of the nuclear emulsion, showing that it amounts to about 0.06 per year per kilogram, fully compatible with the design of a 10 kg × year exposure.
The OPERA experiment has conclusively observed the appearance of tau neutrinos in the muon neutrino CNGS beam. Exploiting the OPERA detector capabilities, it was possible to isolate high purity ...samples of νe, νμ and ντ charged current weak neutrino interactions, as well as neutral current weak interactions. In this paper, the full dataset is used for the first time to test the three-flavor neutrino oscillation model and to derive constraints on the existence of a light sterile neutrino within the framework of the 3+1 neutrino model. For the first time, tau and electron neutrino appearance channels are jointly used to test the sterile neutrino hypothesis. A significant fraction of the sterile neutrino parameter space allowed by LSND and MiniBooNE experiments is excluded at 90% C.L. In particular, the best-fit values obtained by MiniBooNE combining neutrino and antineutrino data are excluded at 3.3σ significance.
K2K and T2K Loverre, P F; collaborations), the K2K T2K
Journal of physics. Conference series,
05/2006, Letnik:
39, Številka:
1
Journal Article
Recenzirano
Odprti dostop
K2K is the first accelerator experiment to investigate neutrino oscillation in the Δm2 region of atmospheric neutrinos. The observed energy dependent disappearance of νµ leads, with a preliminary ...analysis of the full statistics, to the determination of sin22θ 1.19±0.23 and Δm2 (2.55±0.40)×10−3 eV2. The T2K experiment, follow-up of K2K, will start data taking in 2009. T2K will use the new high intensity muon neutrino beam now under construction at JPARC. Neutrino interactions will be detected, as for K2K, in SuperKamiokande at a distance of 295 km. Main goals of the experiment are a high sensitivity search for νe appearance and a study of νµ with precision δ(Δm223) ∼ 1 × 10−4eV2 and δ(sin22θ23) ∼ 0.01.
An event topology with two secondary vertices compatible with the decay of short-lived particles was found in the analysis of neutrino interactions in the OPERA target. The observed topology is ...compatible with tau neutrino charged current (CC) interactions with charm production and neutrino neutral current (NC) interactions with Formula omitted pair production. However, other processes can mimic this topology. A dedicated analysis was implemented to identify the underlying process. A Monte Carlo simulation was developed and complementary procedures were introduced in the kinematic reconstruction. A multivariate analysis technique was used to achieve an optimal separation of signal from background. Most likely, this event is a Formula omitted CC interaction with charm production, the tau and charm particle decaying into 1 prong and 2 prongs, respectively. The significance of this observation is evaluated.
The OPERA detector, designed to search for v.sub.μ right arrow v.sub.τ 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 R.sub.μ = N.sub.μ + /N.sub.μ- 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, R.sub.μ 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.
The OPERA experiment searching for nu(mu)- nu(tau) oscillations in the CERN to Gran Sasso nu(mu) beam, has detected so far three candidates of nu(tau) charged current interactions. All three events ...are attributed by the authors to the standard nu(mu)-nu(tau) oscillation at the atmospheric \(Dm^2\). It is then possible to constrain the number of additional interactions, which could e.g. result from non-standard oscillations involving more than 3 neutrino mass states. In this paper, a 90 percent CL upper limit of 5.5 events is set on the number of additional nu(tau) interactions. This limit is then converted into limits on exotic nu(mu)-nu(tau) oscillations.
Latest results of the OPERA experiment on nu-tau appearance in the CNGS neutrino beam N. Agafonova, A. Alexandrov, A. Anokhina, S. Aoki, A. Ariga, T. Ariga, A. Bertolin, C. Bozza, R. Brugnera, A. Buonaura, S. Buontempo, M. Chernyavskiy, A. Chukanov, L. Consiglio, N. D'Ambrosio, G. De Lellis, M. De Serio, P. del Amo Sanchez, A. Di Crescenzo, D. Di Ferdinando, N. Di Marco, S. Dmitrievsky, M. Dracos, D. Duchesneau, S. Dusini, T. Dzhatdoev, J. Ebert, A. Ereditato, J. Favier, R. A. Fini, F. Fornari, T. Fukuda, G. Galati, A. Garfagnini, V. Gentile, J. Goldberg, S. Gorbunov, Y. Gornushkin, G. Grella, A. M. Guler, C. Gustavino, C. Hagner, T. Hara, T. Hayakawa, A. Hollnagel, K. Ishiguro, A. Iuliano, K. Jakovcic, C. Jollet, C. Kamiscioglu, M. Kamiscioglu, S. H. Kim, N. Kitagawa, B. Klicek, K. Kodama, M. Komatsu, U. Kose, I. Kreslo, F. Laudisio, A. Lauria, A. Longhin, P. Loverre, M. Malenica, A. Malgin, G. Mandrioli, T. Matsuo, V. Matveev, N. Mauri, E. Medinaceli, A. Meregaglia, S. Mikado, M. Miyanishi, F. Mizutani, P. Monacelli, M. C. Montesi, K. Morishima, M. T. Muciaccia, N. Naganawa, T. Naka, M. Nakamura, T. Nakano, K. Niwa, S. Ogawa, A. Olchevsky, N. Okateva, K. Ozaki, A. Paoloni, L. Paparella, B. D. Park, L. Pasqualini, A. Pastore, L. Patrizii, H. Pessard, C. Pistillo, D. Podgrudkov, N. Polukhina, M. Pozzato, F. Pupilli, M. Roda, T. Roganova, H. Rokujo, G. Rosa, O. Ryazhskaya, A. Sadovsky, O. Sato, A. Schembri, I. Shakiryanova, T. Shchedrina, E. Shibayama, H. Shibuya, T. Shiraishi, S. Simone, C. Sirignano, G. Sirri, A. Sotnikov, M. Spinetti, L. Stanco, N. Starkov, S. M. Stellacci, M. Stipcevic, P. Strolin, S. Takahashi, M. Tenti, F. Terranova, V. Tioukov, S. Tufanli, A. Ustyuzhanin, S. Vasina, P. Vilain, E. Voevodina, L. Votano, J. L. Vuilleumier, G. Wilquet, B. Wonsak, C. S. Yoon
SciPost physics proceedings,
2019
1
Journal Article
Recenzirano
Odprti dostop
OPERA is a long-baseline experiment designed to search for $\nu_{\mu}\to\nu_{\tau}$ oscillations in appearance mode. It was based at the INFN Gran Sasso laboratory (LNGS) and took data from 2008 to ...2012 with the CNGS neutrino beam from CERN. After the discovery of $\nu_\tau$ appearance in 2015, with $5.1\sigma$ significance, the criteria to select $\nu_\tau$ candidates have been extended and a multivariate approach has been used for events identification. In this way the statistical uncertainty in the measurement of the oscillation parameters and of $\nu_\tau$ properties has been improved. Results are reported.
The results of a leading-order QCD analysis of neutrino-induced charm production are presented. They are based on a sample of 4111 $\numu$- and 871 $\anumu$-induced opposite-sign dimuon events with ...$E_{\mu 1},E_{\mu 2} 6~{\rm GeV}$, $35 E_{\nu} 290~{\rm GeV}$ and $Q^2 5.5\,{\rm GeV^2}$, observed in the CHARM~II detector exposed to the CERN wideband neutrino and antineutrino beams. The analysis yields the value of \linebreak the charm quark mass $m_c=1.79\pm0.38\,{\rm GeV}/c^2$ and the Cabibbo--Kobayashi--Maskawa matrix element $|V_{cd}|=0.219\pm0.016$. The strange quark content of the nucleon is found to be suppressed with respect to non-strange sea quarks by a factor $\kappa =0.39\pm0.09$.
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