2019, Ahdida, C., Albanese, R. M., Alexandrov, A., Anokhina, A., Atkin, E., Dmitrenko, V., Etenko, A., Filippov, K., Gavrilov, G., Grachev, V., Kudenko, Y., Novikov, A., Polukhina, N., Samsonov, V., Shustov, A., Skorokhvatov, M., Smirnov, S., Teterin, P., Ulin, S., Uteshev, Z., Vlasik, K., Аткин, Эдуард Викторович, Дмитренко, Валерий Васильевич, Этенко, Александр Владимирович, Грачев, Виктор Михайлович, Куденко, Юрий Григорьевич, Полухина, Наталья Геннадьевна, Шустов, Александр Евгеньевич, Скорохватов, Михаил Дмитриевич, Смирнов, Сергей Юрьевич, Тетерин, Пётр Евгеньевич, Улин, Сергей Евгеньевич, Утешев, Зияэтдин Мухамедович, Власик, Константин Федорович

© 2019 CERN.This paper presents a fast approach to simulating muons produced in interactions of the SPS proton beams with the target of the SHiP experiment. The SHiP experiment will be able to search for new long-lived particles produced in a 400 GeV/c SPS proton beam dump and which travel distances between fifty metres and tens of kilometers. The SHiP detector needs to operate under ultra-low background conditions and requires large simulated samples of muon induced background processes. Through the use of Generative Adversarial Networks it is possible to emulate the simulation of the interaction of 400 GeV/c proton beams with the SHiP target, an otherwise computationally intensive process. For the simulation requirements of the SHiP experiment, generative networks are capable of approximating the full simulation of the dense fixed target, offering a speed increase by a factor of (106). To evaluate the performance of such an approach, comparisons of the distributions of reconstructed muon momenta in SHiP's spectrometer between samples using the full simulation and samples produced through generative models are presented. The methods discussed in this paper can be generalised and applied to modelling any non-discrete multi-dimensional distribution.

2019, Agafonova, N., Alexandrov, A., Anokhina, A., Aoki, S., Polukhina, N., Полухина, Наталья Геннадьевна

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 nu(e), nu(mu), and nu(tau) 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 3.3 sigma significance.

2019, Agafonova, N., Alexandrov, A., Anokhina, A., Aoki, S., Polukhina, N., Полухина, Наталья Геннадьевна

© 2019 American Physical Society. All rights reserved.OPERA is a long-baseline experiment designed to search for νμ → ντ 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 ντ appearance in 2015, with 5.1σ significance, the criteria to select ντ 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 ντ properties has been improved. Results are reported.

2019, Ahdida, C., Albanese, R., Alexandrov, A., Anokhina, A., Atkin, E., Dmitrenko, V., Etenko, A., Filippov, K., Gavrilov, G., Grachev, V., Kudenko, Y., Novikov, A., Polukhina, N., Samsonov, V., Shustov, A., Skorokhvatov, M., Smirnov, S., Teterin, P., Ulin, S., Uteshev, Z., Vlasik, K., Аткин, Эдуард Викторович, Дмитренко, Валерий Васильевич, Этенко, Александр Владимирович, Грачев, Виктор Михайлович, Куденко, Юрий Григорьевич, Полухина, Наталья Геннадьевна, Шустов, Александр Евгеньевич, Скорохватов, Михаил Дмитриевич, Смирнов, Сергей Юрьевич, Тетерин, Пётр Евгеньевич, Улин, Сергей Евгеньевич, Утешев, Зияэтдин Мухамедович, Власик, Константин Федорович

The Search for Hidden Particles (SHiP) Collaboration has shown that the CERN SPS accelerator with its 400 GeV/c proton beam offers a unique opportunity to explore the Hidden Sector [1-3]. The proposed experiment is an intensity frontier experiment which is capable of searching for hidden particles through both visible decays and through scattering signatures from recoil of electrons or nuclei. The high-intensity experimental facility developed by the SHiP Collaboration is based on a number of key features and developments which provide the possibility of probing a large part of the parameter space for a wide range of models with light long-lived super-weakly interacting particles with masses up to O(10) GeV/c(2) in an environment of extremely clean background conditions. This paper describes the proposal for the experimental facility together with the most important feasibility studies. The paper focuses on the challenging new ideas behind the beam extraction and beam delivery, the proton beam dump, and the suppression of beam-induced background.

2019, Agafonova, N., Alexandrov, A., Anokhina, A., Aoki, S., Polukhina, N., Полухина, Наталья Геннадьевна

© 2019 IOP Publishing Ltd and Sissa Medialab.The OPERA experiment discovered muon neutrino into tau neutrino oscillations in appearance mode, detecting tau leptons by means of nuclear emulsion films. The apparatus was also endowed with electronic detectors with tracking capability, such as scintillator strips and resistive plate chambers. Because of its location in the underground Gran Sasso laboratory, under 3800 m.w.e., the OPERA detector has also been used as an observatory for TeV muons produced by cosmic rays in the atmosphere. In this paper the measurement of the single muon flux modulation and its correlation with the seasonal cycle of atmospheric temperature is reported.

2020, Agafonova, N., Aleksandrov, A., Anokhina, A., Aoki, S., Polukhina, N., Полухина, Наталья Геннадьевна

© 2020, The Author(s).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 cc¯ 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 ντ 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.

2019, Ahdida, C., Albanese, R., Alexandrov, A., Anokhina, A., Atkin, E., Dmitrenko, V., Etenko, A., Filippov, K., Gavrilov, G., Grachev, V., Kudenko, Y., Novikov, A., Polukhina, N., Samsonov, V., Shustov, A., Skorokhvatov, M., Smirnov, S., Teterin, P., Ulin, S., Uteshev, Z., Vlasik, K., Аткин, Эдуард Викторович, Дмитренко, Валерий Васильевич, Этенко, Александр Владимирович, Грачев, Виктор Михайлович, Куденко, Юрий Григорьевич, Полухина, Наталья Геннадьевна, Шустов, Александр Евгеньевич, Скорохватов, Михаил Дмитриевич, Смирнов, Сергей Юрьевич, Тетерин, Пётр Евгеньевич, Улин, Сергей Евгеньевич, Утешев, Зияэтдин Мухамедович, Власик, Константин Федорович

Heavy Neutral Leptons (HNLs) are hypothetical particles predicted by many extensions of the Standard Model. These particles can, among other things, explain the origin of neutrino masses, generate the observed matter-antimatter asymmetry in the Universe and provide a dark matter candidate. The SHiP experiment will be able to search for HNLs produced in decays of heavy mesons and travelling distances ranging between O(50 m) and tens of kilometers before decaying. We present the sensitivity of the SHiP experiment to a number of HNL's benchmark models and provide a way to calculate the SHiP's sensitivity to HNLs for arbitrary patterns of flavour mixings. The corresponding tools and data files are also made publicly available.

2020, Ahdida, C., Albanese, R., Alexandrov, A., Anokhina, A., Atkin, E., Dmitrenko, V., Etenko, A., Filippov, K., Gavrilov, G., Grachev, V., Kudenko, Y., Novikov, A., Polukhina, N., Samsonov, V., Shustov, A., Skorokhvatov, M., Smirnov, S., Teterin, P., Ulin, S., Uteshev, Z., Vlasik, K., Аткин, Эдуард Викторович, Дмитренко, Валерий Васильевич, Этенко, Александр Владимирович, Грачев, Виктор Михайлович, Куденко, Юрий Григорьевич, Полухина, Наталья Геннадьевна, Шустов, Александр Евгеньевич, Скорохватов, Михаил Дмитриевич, Смирнов, Сергей Юрьевич, Тетерин, Пётр Евгеньевич, Улин, Сергей Евгеньевич, Утешев, Зияэтдин Мухамедович, Власик, Константин Федорович

© 2020 CERN. Published by IOP Publishing Ltd on behalf of Sissa Medialab. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.The Search for Hidden Particles (SHiP) experiment proposal at CERN demands a dedicated dipole magnet for its scattering and neutrino detector. This requires a very large volume to be uniformly magnetized at B > 1.2 T, with constraints regarding the inner instrumented volume as well as the external region, where no massive structures are allowed and only an extremely low stray field is admitted. In this paper we report the main technical challenges and the relevant design options providing a comprehensive design for the magnet of the SHiP Scattering and Neutrino Detector.