Kovalenko, Sergey

2021-10-01, Cazzaniga, C., Odagiu, P., Depero, E., Molina Bueno, L., Andreev, Yu M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Girod, S., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, Sergey, Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, Sergey, Lyubovitskij, Valery, Lysan, V., Matveev, V. A., Mikhailov, Yu V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu, Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu, Ulloa, P.

AbstractWe report the results of a search for a new vector boson ($$ A'$$ A ′ ) decaying into two dark matter particles $$\chi _1 \chi _2$$ χ 1 χ 2 of different mass. The heavier $$\chi _2$$ χ 2 particle subsequently decays to $$\chi _1$$ χ 1 and an off-shell Dark Photon $$ A'^* \rightarrow e^+e^-$$ A ′ ∗ → e + e - . For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay $$A'\rightarrow \chi \overline{\chi }$$ A ′ → χ χ ¯ and axion-like or pseudo-scalar particles $$a \rightarrow \gamma \gamma $$ a → γ γ . With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for $$A'$$ A ′ masses from 2$$m_e$$ m e up to 390 MeV and mixing parameter $$\varepsilon $$ ε between $$3\times 10^{-5}$$ 3 × 10 - 5 and $$2\times 10^{-2}$$ 2 × 10 - 2 .

2019-12-09, Arberlaez, Carolina, Carcamo Hernández, Antonio, Cepedello, Ricardo, Hirsch, Martin, Kovalenko, Sergey

We discuss a radiative type-I seesaw. In these models, the radiative generation of Dirac neutrino masses allows to explain the smallness of the observed neutrino mass scale for rather light right-handed neutrino masses in a type-I seesaw. We first present the general idea in a model-independent way. This allows us to estimate the typical scale of right-handed neutrino mass as a function of the number of loops. We then present two example models, at the one- and two-loop level, which we use to discuss neutrino masses and lepton-flavor-violating constraints in more detail. For the two-loop example, right-handed neutrino masses must lie below 100 GeV, thus making this class of models testable in heavy neutral lepton searches.

2018-04-01, Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, Sergey, Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, Sergey, Lyubovitskij, Valery, Lysan, V., Matveev, V. A., Mikhailov, Yu V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu, Vasilishin, B. I., Vasquez Arenas, G., Ulloa, P.

A search is performed for a new sub-GeV vector boson (A0 ) mediated production of dark matter (χ) in the fixed-target experiment, NA64, at the CERN SPS. The A0 , called dark photon, can be generated in the reaction e−Z → e−ZA0 of 100 GeV electrons dumped against an active target followed by its prompt invisible decay A0 → χχ¯. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to 4.3 × 1010 electrons on target no evidence of such a process has been found. New stringent constraints on the A0 mixing strength with photons, 10−5 ≲ ϵ ≲ 10−2, for the A0 mass range mA0 ≲ 1 GeV are derived. For models considering scalar and fermionic thermal dark matter interacting with the visible sector through the vector portal the 90% C.L. limits 10−11 ≲ y ≲ 10−6 on the dark-matter parameter y ¼ ϵ2αDð mχ mA0 Þ4 are obtained for the dark coupling constant αD ¼ 0.5 and dark-matter masses 0.001 ≲ mχ ≲ 0.5 GeV. The lower limits αD ≳ 10−3 for pseudo-Dirac dark matter in the mass region mχ ≲ 0.05 GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using exact tree level calculations of the A0 production cross sections, which turn out to be significantly smaller compared to the one obtained in the Weizsäcker-Williams approximation for the mass region mA0 ≳ 0.1 GeV.

2024-02-01, de Jesus, A. S., Kovalenko, Sergey, de Melo, T. B., Neto, J. P., Oviedo-Torres, Y. M., Queiroz, F. S., Villamizar, Y. S., Zerwekh, Alfonso

The Standard Model has no Flavor-Changing Neutral Current (FCNC) processes at the tree level. Therefore, processes featuring FCNC in new physics are tightly constrained by data. Typically, the lower bounds on the scale of new physics obtained from or mixing lie well above 10 TeV, surpassing the reach of current and future colliders. In this paper, we demonstrate, using a specific model that features flavor-changing interactions, that such limits can be severely weakened by specific choices of the quark mixing matrices with no prejudice while maintaining the CKM matrix in agreement with the data. We highlight the valuable role of the often-overlooked mixing in deriving robust FCNC limits and show that the LHC and HL-LHC are promising probes for flavor-changing interactions mediated by a boson.

2002-09-19, Šimkovic, F., Lyubovitskij, Valery, Gutsche, Th, Faessler, Amand, Kovalenko, Sergey

We found a new important tree-level contribution to muon–electron nuclear conversion from neutrino exchange between two quarks in the same nucleon and demonstrated that this process, contrary to common belief, can be observed in the near future experiments if there exists a mixed sterile-active neutrino state νh heavier than the quark confinement scale Λc ∼ 1 GeV. From the present non-observation of muon–electron conversion we derive new experimental constraints on νh − νe,µ mixing

2019-09-18, Banerjee, D., Burtsev, V. E., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, Sergey, Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, Valery, Lysan, V., Matveev, V. A., Mikhailov, Yu V., Molina Bueno, L., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, Christian A., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu, Vasilishin, B. I., Vasquez Arenas, G., Volkov, P. V., Volkov, V. Yu, Ulloa, P.

A search for sub-GeV dark matter production mediated by a new vector boson A′, called dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×1011 electrons on target no evidence of such a process has been found. The most stringent constraints on the A′ mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.

2017-01-05, Banerjee, D., Burtsev, V., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kovalenko, Sergey, Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, Sergey, Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Petuhov, O., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu, Vasilishin, B., Vasquez Arenas, G, Ulloa, P., Zhukov, K., Zioutas, K.

We report on a direct search for sub-GeV dark photons (A0 ), which might be produced in the reaction e−Z → e−ZA0 via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The dark photons would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75 × 109 electrons on target. We set new limits on the γ − A0 mixing strength and exclude the invisible A0 with a mass ≲100 MeV as an explanation of the muon gμ − 2 anomaly.

2023-12-10, Bonilla, Cesar, Carcamo Hernández, Antonio, Díaz Sáez, Bastián, Kovalenko, Sergey, Marchant González, Juan

We propose a Majoron-like extension of the Standard Model with an extra global -symmetry where neutrino masses are generated through an inverse seesaw mechanism at the 1-loop level. In contrast to the tree-level inverse seesaw, our framework contains dark matter (DM) candidates stabilized by a residual -symmetry surviving spontaneous breaking of the -group. We explore the case in which the DM is a Majorana fermion. Furthermore, we provide parameter space regions allowed by current experimental constraints coming from the dark matter relic abundance, (in)direct detection, and charged lepton flavor violation.

2018-05-01, M. González, Kovalenko, Sergey, M. Hirsch

The decay rate of neutrinoless double beta (0νββ) decay contains terms from heavy particle exchange, which lead to dimension-9 (d ¼ 9) six fermion operators at low energies. Limits on the coefficients of these operators have been derived previously neglecting the running of the operators between the high scale, where they are generated, and the energy scale of 0νββ decay, where they are measured. Here we calculate the leading-order QCD corrections to all possible d ¼ 9 operators contributing to the 0νββ amplitude and use renormalization group running to calculate 1-loop improved limits. Numerically, QCD running dramatically changes some limits by factors of the order of or larger than typical uncertainties in nuclear matrix element calculations. For some specific cases, operator mixing in the running changes limits even by up to 3 orders of magnitude. Our results can be straightforwardly combined with new experimental limits or improved nuclear matrix element calculations to rederive updated limits on all short-range contributions to 0νββ decay.

2018-05-01, Arberlaez, Carolina, M. González, M. Hirsch, Kovalenko, Sergey

Recently it has been demonstrated that QCD corrections are numerically important for short-range mechanisms (SRM) of neutrinoless double beta decay (0νββ) mediated by heavy particle exchange. This is due to the effect of color mismatch for certain effective operators, which leads to mixing between different operators with vastly different nuclear matrix elements (NMEs). In this note we analyze the QCD corrections for long-range mechanisms (LRM), due to diagrams with light-neutrino exchange between a Standard Model (V-A)×(V-A) and a beyond the SM lepton number violating vertex. We argue that in contrast to the SRM in the LRM case, there is no operator mixing from color-mismatched operators. This is due to a combined effect of the nuclear short-range correlations and color invariance. As a result, the QCD corrections to the LRM amount to an effect no more than 60%, depending on the operator in question. Although less crucial, taken into account QCD running makes theoretical predictions for 0νββ-decay more robust also for LRM diagrams. We derive the current experimental constraints on the Wilson coefficients for all LRM effective operators.