Examinando por Autor "Bernhard, J."
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Ítem Measurement of the intrinsic hadronic contamination in the NA64−e high-purity e+/e− beam at CERN(Elsevier B.V., 2023-12) Andreev, Yu. M.; Banerjee, D.; Banto Oberhauser, B.; Bernhard, J.; Bisio, P.; Bondí, M.; Celentano, A.; Charitonidis, N.; Chumakov, A. G.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A. V.; Donskov, S. V.; Dusaev, R. R.; Enik, T.; Frolov, V. N.; Gardikiotis, A.; Gerassimov, S. G.; Gninenko, S. N.; Hösgen, M.; Jeckel, M.; Kachanov, V. A.; Kambar, Y.; Karneyeu, A. E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D. V.; Kirsanov, M. M.; Kolosov, V. N.; Konorov, I. V.; Gertsenberger, S. V.; Kasianova, E. A.; Kovalenko, S. G.; Kramarenko, V. A.; Kravchuk, L. V.; Krasnikov, N. V.; Kuleshov, S. V.; Lyubovitskij, V. E.; Lysan, V.; Marini, A.; Marsicano, L.; Matveev, V. A.; Mikhailov, Yu. V.; Molina Bueno, L.; Mongillo, M.; Peshekhonov, D. V.; Polyakov, V. A.; Radics, B.; Rojas, R.; Salamatin, K.; Samoylenko, V. D.; Sieber, H.; Shchukin, D.; Soto, O.; Tikhomirov, V. O.; Tlisova, I.; Toropin, A. N.; Trifonov, A. Yu.; Tuzi, M.; Ulloa, P.; Vasilishin, B. I.; Vasquez Arenas, G.; Volkov, P. V.; Volkov, V. Yu.; Voronchikhin, I. V.; Zamora-Saá, J.; Zhevlakov, A. S.We present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c. The analysis, performed using data collected by the NA64-e experiment in 2022, is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64 detector. We determined the contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those from a dedicated setup, in which only hadrons impinged on the detector. We also obtained an estimate of the relative protons, anti-protons and pions yield by exploiting the different absorption probabilities of these particles in matter. We cross-checked our results with a dedicated Monte Carlo simulation for the hadron production at the primary T2 target, finding a good agreement with the experimental measurements.Ítem Search for a light Z′ in the Lμ-Lτ scenario with the NA64-e experiment at CERN(American Physical Society, 2022-08) Andreev, Yu. M.; Banerjee, D.; Banto Oberhauser, B.; Bernhard, J.; Bisio, P.; Bondí, M.; Burtsev, V.E.; Celentano, A.; Charitonidis, N.; Chumakov, A.G.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A.V.; Donskov, S.V.; Dusaev, R.R.; Enik, T.; Frolov, V.N.; Gardikiotis, A.; Gerassimov, S.G.; Gninenko, S.N.; Hösgen, M.; Jeckel, M.; Kachanov, V.A.; Karneyeu, A.E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D.V.; Kirsanov, M.M.; Kolosov, V.N.; Konorov, I.V.; Kovalenko, S.G.; Kramarenko, V.A.; Kravchuk, L.V.; Krasnikov, N.V.; Kuleshov, S.V.; Lyubovitskij, V.E.; Lysan, V.; Marsicano, L.; Matveev, V.A.; Mikhailov, Yu. V.; Molina Bueno, L.; Peshekhonov, D.V.; Polyakov, V.A.; Radics, B.; Rojas, R.; Rubbia, A.; Salamatin, K.M.; Samoylenko, V.D.; Sieber, H.; Shchukin, D.; Tikhomirov, V.O.; Tlisova, I.; Toropin, A.N.; Trifonov, A. Yu.; Ulloa, P.; Vasilishin, B.I.; Vasquez Arenas, G.; Volkov, P.V.; Volkov, V. Yu.; Voronchikhin, I.The extension of Standard Model made by inclusion of additional U(1) gauge Lμ-Lτ symmetry can explain the difference between the measured and the predicted value of the muon magnetic moment and solve the tension in B meson decays. This model predicts the existence of a new, light Z′ vector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. In this work, we present a rigorous evaluation of the upper limits in the Z′ parameter space, obtained from the analysis of the data collected by the NA64-e experiment at CERN SPS, that performed a search for light dark matter with 2.84×1011 electrons impinging with 100 GeV on an active thick target. The resulting limits touch the muon g-2 preferred band for values of the Z′ mass of order of 1 MeV, while the sensitivity projections for the future high-statistics NA64-e runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario. © 2022 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Ítem Search for a New B-L Z′ Gauge Boson with the NA64 Experiment at CERN(American Physical Society, 2022-10-14) Andreev, Yu. M.; Banerjee, D.; Oberhauser B., Banto; Bernhard, J.; Bisio, P.; Burtsev, V.E.; Celentano, A.; Charitonidis, N.; Chumakov, A.G.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A.V.; Donskov, S.V.; Dusaev, R.R.; Enik, T.; Frolov, V.N.; Gardikiotis, A.; Gerassimov, S.G.; Gninenko, S.N.; Hösgen, M.; Jeckel, M.; Kachanov, V.A.; Karneyeu, A.E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D.V.; Kirsanov, M.M.; Kolosov, V.N.; Kovalenko, S.G.; Kramarenko, V.A.; Kravchuk, L.V.; Krasnikov, N.V.; Kuleshov, S.V.; Lyubovitskij, V.E.; Lysan, V.; Marsicano, L.; Matveev, V.A.; Mikhailov, Yu. V.; Molina Bueno, L.; Peshekhonov, D.V.; Polyakov, V.A.; Radics, B.; Rubbia, A.; Samalantin, K.M.; Samoylenko, V.D.; Sieber, H.; Shchukin, D.; Soto, O.; Tikhomirov, V.O.; Tlisova, I.V.; Toropin, A.N.; Vasilishin, B.I.; Volkov, P.V.; Volkov, V. Yu.; Voronchikhin, I.; Zamora Saá, J.A search for a new Z′ gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×1011 electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Z′-e coupling strength, which, for the mass range 0.3mZ′ 100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data. © 2022 authors. Published by the American Physical Society.Ítem Search for Axionlike and Scalar Particles with the NA64 Experiment(American Physical Society, 2020-08) Banerjee, D.; Bernhard, J.; Burtsev, V.E.; Chumakov, A.G.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A.V.; Donskov, S.V.; Dusaev, R.R.; Enik, T.; Charitonidis, N.We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a(s)→γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing of the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×1011 electrons on target, allowing us to set new limits on the a(s)γγ-coupling strength for a(s) masses below 55 MeV. © 2020 authors. Published by the American Physical Society. Funded by SCOAP3.Ítem Search for pseudoscalar bosons decaying into e+e- pairs in the NA64 experiment at the CERN SPS(American Physical Society, 2021-12-01) Andreev, Yu. M.; Banerjee, D.; Bernhard, J.; Burtsev, V. E.; Charitonidis, N.; Chumakov, A. G.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A. V.; Donskov, S. V.; Dusaev, R. R.; Enik, T.; Feshchenko, A.; Frolov, V. N.; Gardikiotis, A.; Gerassimov, S. G.; Gninenko, S. N.; Hösgen, M.; Jeckel, M.; Kachanov, V. A.; Karneyeu, A. E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D. V.; Kirsanov, M. M.; Kolosov, V. N.; Konorov, I. V.; Kovalenko, S. G.; Kramarenko, V. A.; Kravchuk, L. V.; Krasnikov, N. V.; Kuleshov, S. V.; Lyubovitskij, V. E.; Lysan, V.; Matveev, V. A.; Mikhailov, Yu. V.; Molina Bueno, L.; Peshekhonov, D. V.; Polyakov, V. A.; Radics, B.; Rojas, R.; Rubbia, A.; Samoylenko, V. D.; Sieber, H.; Shchukin, D.; Tikhomirov, V. O.; Tlisova, I.; Toropin, A. N.; Trifonov, A. Yu.; Vasilishin, B. I.; Vasquez Arenas, G.; Volkov, P. V.; Volkov, V. Yu.; Ulloa, P.We report the results of a search for a light pseudoscalar particle a that couples to electrons and decays to e+e- performed using the high-energy CERN SPS H4 electron beam. If such light pseudoscalar exists, it could explain the ATOMKI anomaly (an excess of e+e- pairs in the nuclear transitions of Be8 and He4 nuclei at the invariant mass ≃17 MeV observed by the experiment at the 5 MV Van de Graaff accelerator at ATOMKI, Hungary). We used the NA64 data collected in the "visible mode"configuration with a total statistics corresponding to 8.4×1010 electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter ϵ we also used the data collected in 2016-2018 in the "invisible mode"configuration of NA64 with a total statistics corresponding to 2.84×1011 EOT. The background and efficiency estimates for these two configurations were retained from our previous analyses searching for light vector bosons and axionlike particles (ALP) (the latter were assumed to couple predominantly to γ). In this work we recalculate the signal yields, which are different due to different cross section and lifetime of a pseudoscalar particle a, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space ma-ϵ in the mass range from 1 to 17.1 MeV is excluded. At the mass of the central value of the ATOMKI anomaly (the first result obtained on the beryllium nucleus, 16.7 MeV) the values of ϵ in the range 2.1×10-4<ϵ<3.2×10-4 are excluded.