Examinando por Autor "Zhevlakov A.S."

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    Probing light dark matter with positron beams at NA64
    (American Physical Society, 2024-02 ) Andreev, Yu. M.; Antonov, A.; Banerjee, D.; Banto Oberhauser B.; Bernhard J.; Bisio P.; Bondí M.; Celentano A.; Charitonidis N.; Cooke D.; Crivelli P.; Depero E.; Dermenev A.V.; Donskov S.V.; Dusaev R.R.; Enik T.; Frolov V.N.; Gardikiotis A.; Gninenko S.N.; Hösgen M.; Kachanov V.A.; Kambar Y.; Karneyeu A.E.; Kekelidze G.; Ketzer B.; Kirpichnikov D.V.; Kirsanov M.M.; Gertsenberger S.V.; Girod S.; Kasianova E.A.; Kramarenko V.A.; Kravchuk L.V.; Krasnikov N.V.; Kuleshov S.V.; Lyubovitskij V.E.; Lysan V.; Marini A.; Marsicano L.; Matveev V.A.; Mena Fredes R.; Mena Yanssen R.; Molina Bueno L.; Mongillo M.; Peshekhonov D.V.; Polyakov V.A.; Radics B.; Salamatin K.; Samoylenko V.D.; Sieber H.; Shchukin D.; Soto O.; Tikhomirov V.O.; Tlisova I.; Toropin A.N.; Tuzi M.; Ulloa P.; Volkov P.V.; Volkov, V. Yu.; Voronchikhin I.V.; Zamora-Saá J.; Zhevlakov A.S.
    We present the results of a missing-energy search for light dark matter which has a new interaction with ordinary matter transmitted by a vector boson, called dark photon A′. For the first time, this search is performed with a positron beam by using the significantly enhanced production of A′ in the resonant annihilation of positrons with atomic electrons of the target nuclei, followed by the invisible decay of A′ into dark matter. No events were found in the signal region with (10.1±0.1)×109 positrons on target with 100 GeV energy. This allowed us to set new exclusion limits that, relative to the collected statistics, prove the power of this experimental technique. This measurement is a crucial first step toward a future exploration program with positron beams, whose estimated sensitivity is here presented.
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    Search for Light Dark Matter with NA64 at CERN
    (American Physical Society, 2023-10-20) Andreev, Yu. M.; Banerjee D.; Banto Oberhauser B.; Bernhard J.; Bisio P.; 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.; Galleguillos Silva R.B.; Gardikiotis A.; Gertsenberger S.V.; Girod S.; Gninenko S.N.; Hösgen M.; Kachanov V.A.; Kambar Y.; Karneyeu A.E.; Kasianova E.A.; Kekelidze G.D.; Ketzer B.; Kirpichnikov D.V.; Kirsanov M.M.; Kolosov V.N.; Kramarenko V.A.; Kravchuk L.V.; Krasnikov N.V.; Kuleshov S.V.; Lyubovitskij V.E.; Lysan V.; Marini A.; Marsicano L.; Matveev V.A.; Mena Fredes R.; Mena Yanssen R.G.; Molina Bueno L.; Mongillo M.; Peshekhonov D.V.; Polyakov V.A.; Radics B.; Salamatin K.M.; Samoylenko V.D.; Sieber H.; Shchukin D.A.; Soto O.; Tikhomirov V.O.; Tlisova I.V.; Toropin A.N.; Tuzi M.; Vasilishin B.I.; Volkov P.V.; Volkov, V. Yu.; Voronchikhin I.V.; Zamora-Saá J.; Zhevlakov A.S.
    Thermal dark matter models with particle χ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV χ production through the interaction mediated by a new vector boson, called the dark photon A′, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With 9.37×1011 electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the A′ couplings to photons for masses mA′≲0.35 GeV, and to exclude scalar and Majorana dark matter with the χ-A′ coupling αD≤0.1 for masses 0.001≲mχ≲0.1 GeV and 3mχ≤mA′.