The OPERA experiment was designed to search for ν_{μ}→ν_{τ} oscillations in appearance mode, i.e., by detecting the τ leptons produced in charged current ν_{τ} interactions. The experiment took data ...from 2008 to 2012 in the CERN Neutrinos to Gran Sasso beam. The observation of the ν_{μ}→ν_{τ} appearance, achieved with four candidate events in a subsample of the data, was previously reported. In this Letter, a fifth ν_{τ} candidate event, found in an enlarged data sample, is described. Together with a further reduction of the expected background, the candidate events detected so far allow us to assess the discovery of ν_{μ}→ν_{τ} oscillations in appearance mode with a significance larger than 5σ.
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.
The OPERA experiment, designed to perform the first observation of
ν
μ
→
ν
τ
oscillations in appearance mode through the detection of the
τ
leptons produced in
ν
τ
charged current interactions, has ...collected data from 2008 to 2012. In the present paper, the procedure developed to detect
τ
particle decays, occurring over distances of the order of
1
mm
from the neutrino interaction point, is described in detail and applied to the search for charmed hadrons, showing similar decay topologies as the
τ
lepton. In the analysed sample, 50 charm decay candidate events are observed while
54
±
4
are expected, proving that the detector performance and the analysis chain applied to neutrino events are well reproduced by the OPERA simulation and thus validating the methods for
ν
τ
appearance detection.
After completion of the data taking for the νμ→ντ oscillation search, the CHORUS lead–scintillator calorimeter was used in the 1998 run as an active target. High-statistics samples of charged-current ...interactions were collected in the CERN SPS west area neutrino beam. This beam contained predominantly muon (anti-)neutrinos from sign-selected pions and kaons. We measure the flux and energy spectrum of the incident neutrinos and compare them with beam simulations. The neutrino–nucleon and anti-neutrino–nucleon differential cross-sections are measured in the range 0.01<x<0.7, 0.05<y<0.95, 10<Eν<200 GeV. We extract the neutrino–nucleon structure functions F2(x,Q2), xF3(x,Q2), and R(x,Q2) and compare these with results from other experiments.
A
bstract
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.
The OPERA experiment was designed to search for
ν
μ
→
ν
τ
oscillations in appearance mode through the direct observation of tau neutrinos in the CNGS neutrino beam. In this paper, we report a study ...of the multiplicity of charged particles produced in charged-current neutrino interactions in lead. We present charged hadron average multiplicities, their dispersion and investigate the KNO scaling in different kinematical regions. The results are presented in detail in the form of tables that can be used in the validation of Monte Carlo generators of neutrino–lead interactions.
The NEMO Phase-2 tower is the first detector which was operated underwater for more than 1 year at the “record” depth of 3500 m. It was designed and built within the framework of the NEMO (NEutrino ...Mediterranean Observatory) project. The 380 m high tower was successfully installed in March 2013 80 km offshore Capo Passero (Italy). This is the first prototype operated on the site where the Italian node of the KM3NeT neutrino telescope will be built. The installation and operation of the NEMO Phase-2 tower has proven the functionality of the infrastructure and the operability at 3500 m depth. A more than 1 year long monitoring of the deep water characteristics of the site has been also provided. In this paper the infrastructure and the tower structure and instrumentation are described. The results of long term optical background measurements are presented. The rates show stable and low baseline values, compatible with the contribution of
40
K light emission, with a small percentage of light bursts due to bioluminescence. All these features confirm the stability and good optical properties of the site.
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.
Abstract
This paper describes a new νe identification method specifically designed to improve the low-energy ($\lt {30}\, {\rm GeV}$) νe identification efficiency attained by enlarging the emulsion ...film scanning volume with the next-generation emulsion readout system. A relative increase of 25–70% in the νe low-energy region is expected, leading to improvements in the OPERA sensitivity to neutrino oscillations in the framework of the 3 + 1 model. The method is applied to a subset of data where the detection efficiency increase is expected to be more relevant, and one additional νe candidate is found. The analysis combined with the ντ appearance results improves the upper limit on sin 22θμe to 0.016 at 90% C.L. in the MiniBooNE allowed region $\Delta m^2_{41} \sim {0.3}\, {\rm eV}^{2}$.
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