Aims. Intergalactic magnetic fields in the voids of the large-scale structure can be probed via measurements of secondary gamma-ray emission from gamma-ray interactions with extragalactic... Show moreAims. Intergalactic magnetic fields in the voids of the large-scale structure can be probed via measurements of secondary gamma-ray emission from gamma-ray interactions with extragalactic background light. Lower bounds on the magnetic field in the voids were derived from the nondetection of this emission. It is not clear a priori what kind of magnetic field is responsible for the suppression of the secondary gamma-ray flux: a cosmological magnetic field that might be filling the voids, or the field spread by galactic winds driven by star formation and active galactic nuclei. Methods. We used IllustrisTNG cosmological simulations to study the effect of magnetized galactic wind bubbles on the secondary gamma-ray flux. Results. We show that within the IllustrisTNG model of baryonic feedback, galactic wind bubbles typically provide energy-independent secondary flux suppression at a level of about 10%. The observed flux suppression effect has to be due to the cosmological magnetic field in the voids. This might not be the case for the special case when the primary gamma-ray source has a hard intrinsic gamma-ray spectrum that peaks in the energy range above 50 TeV. In this case, the observational data may be strongly affected by the magnetized bubble that is blown by the source host galaxy. Show less
The extension of the Standard Model with two gauge-singlet Majorana fermions can simultaneously explain two beyond-the-Standard-model phenomena: neutrino masses and oscillations, as well as the... Show moreThe extension of the Standard Model with two gauge-singlet Majorana fermions can simultaneously explain two beyond-the-Standard-model phenomena: neutrino masses and oscillations, as well as the origin of the matter-antimatter asymmetry in the Universe. The parameters of such a model are constrained by the neutrino oscillation data, direct accelerator searches, big bang nucleosynthesis, and requirement of successful baryogenesis. We show that their combination still leaves an allowed region in the parameter space below the kaon mass. This region can be probed by the further searches of NA62, DUNE, or SHiP experiments. Show less
Traditional direct searches for dark matter, looking for nuclear recoils in deep underground detectors, are challenged by an almost complete loss of sensitivity for light dark matter particles.... Show moreTraditional direct searches for dark matter, looking for nuclear recoils in deep underground detectors, are challenged by an almost complete loss of sensitivity for light dark matter particles. Consequently, there is a significant effort in the community to devise new methods and experiments to overcome these difficulties, constantly pushing the limits of the lowest dark matter mass that can be probed this way. From a model-building perspective, the scattering of sub-GeV dark matter on nucleons essentially must proceed via new light mediator particles, given that collider searches place extremely stringent bounds on contact-type interactions. Here we present an updated compilation of relevant limits for the case of a scalar mediator, including a new estimate of the near-future sensitivity of the NA62 experiment as well as a detailed evaluation of the model-specific limits from Big Bang nucleosynthesis. We also derive updated and more general limits on DM particles upscattered by cosmic rays, applicable to arbitrary energy- and momentum dependences of the scattering cross section. Finally we stress that dark matter self-interactions, when evaluated beyond the common s-wave approximation, place stringent limits independently of the dark matter production mechanism. These are, for the relevant parameter space, generically comparable to those that apply in the commonly studied freeze-out case. We conclude that the combination of existing (or expected) constraints from accelerators and astrophysics, combined with cosmological requirements, puts robust limits on the maximally possible nuclear scattering rate. In most regions of parameter space these are at least competitive with the best projected limits from currently planned direct detection experiments. Show less
Bondarenko, K.; Boiarskyi, O.; Ovchynnikov, M.; Ruchayskiy, O.; Shchutska, L. 2019
Long-lived particles can manifest themselves at the LHC via “displaced vertices”—several charged tracks originating from a position separated from the proton interaction point by a macroscopic... Show moreLong-lived particles can manifest themselves at the LHC via “displaced vertices”—several charged tracks originating from a position separated from the proton interaction point by a macroscopic distance. Here we demonstrate the potential of the muon trackers at the CMS experiment for displaced vertex searches. We use heavy neutral leptons and Chern-Simons portal as two examples of long-lived particles for which the CMS muon tracker can provide essential information about their properties. Show less
Bondarenko, K.; Boyarsky, A.; Ovchynnikov, M.; Ruchayskiy, O. 2019
In recent years, a number of intensity frontier experiments have been proposed to search for feebly interacting particles with masses in the GeV range. We discuss how the characteristic shape of... Show moreIn recent years, a number of intensity frontier experiments have been proposed to search for feebly interacting particles with masses in the GeV range. We discuss how the characteristic shape of the experimental sensitivity regions — upper and lower boundaries of the probed region, the maximal mass reach — depends on the parameters of the experiments. We use the SHiP and the MATHUSLA experiments as examples. We find a good agreement of our estimates with the results of the Monte Carlo simulations. This simple approach allows to cross-check and debug Monte Carlo results, to scan quickly over the parameter space of feebly interacting particle models, and to explore how sensitivity depends on the geometry of experiments. Show less
Bondarenko, K.; Boyarsky, A.; Ovchynnikov, M.; et al 2019
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... Show moreHeavy 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. Show less
Bondarenko, K.; Boiarskyi, O.; Ovchynnikov, M.; et al 2019
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... Show moreThe 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.} Show less
Sokolenko, A.; Bondarenko, K.; Brinckmann, T.; Zavala, J.; Vogelsberger, M.; Bringmann, T.; Boyarsky, A. 2018
