arXiv subjects

Anastasia Sokolenko

Publications and source records attributed to Anastasia Sokolenko.

24 records · Page 2Linked to original sources

arXiv2020

Direct detection and complementary constraints for sub-GeV dark matter

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. 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.

hep-ph↗

arXiv2020

Effective photon mass and (dark) photon conversion in the inhomogeneous Universe

Photons traveling cosmological distances through the inhomogeneous Universe experience a great variation in their in-medium induced effective mass. Using the EAGLE suite of hydrodynamical simulations, we infer the free electron distribution and thereby the effective photon mass after reionization. We use this data to study the inter-conversion of kinetically mixed photons and dark photons, which may occur at a great number of resonance redshifts, and obtain the "optical depth" against conversion along random lines-of-sight. Using COBE/FIRAS, Planck, and SPT measurements, we constrain the dark photon parameter space from the depletion of CMB photons into dark photons that causes both spectral distortions and additional anisotropies in the CMB. Finally, we also consider the conversion of sub-eV dark radiation into ordinary photons. We make the line-of-sight distributions of both, free electrons and dark matter, publicly available.

astro-ph.CO↗

arXiv2020

Constraining dark photons and their connection to 21 cm cosmology with CMB data

In the inhomogeneous Universe, the cosmological conversion of dark photons into ordinary photons (and vice versa) may happen at a great number of resonance redshifts. This alters the CMB observed energy spectrum and degree of small-scale anisotropies. We utilize results from the EAGLE simulation to obtain the conversion probability along random line-of-sights to quantify these effects. We then apply our results to the case where dark photons are sourced by dark matter decay and their high-redshift conversion into ordinary photons modify the global 21 cm signal expected from the cosmic dawn era. Concretely, we show that a significant portion of the parameter space for which a converted population of photons in the Rayleigh-Jeans tail of the CMB explains the absorption strength observed by EDGES, is ruled out from the brightness temperature measurements of COBE/FIRAS and the CMB anisotropy measurements of Planck and SPT.

astro-ph.CO↗

arXiv2019

Towards an improved model of self-interacting dark matter haloes

In this work, we discuss the relation between the strength of the self-interaction of dark matter particles and the predicted properties of the inner density distributions of dark matter haloes. We present the results of $N$-body simulations for 28 haloes performed with the same initial conditions for cold dark matter and for self-interacting dark matter, for a range of cross-sections. We provide a simple phenomenological description of these results and compare with the semi-analytical model typically used in the literature. Using these results, we then predict how the inner dark matter surface density and core radius should depend on the self-interaction cross-section for observed haloes.

astro-ph.CO↗

arXiv2018

Connection between diphoton and triboson channels in new physics searches

Diphoton channel provides a clean signature in searches for new physics. In this paper, we discuss a connection between the diphoton channel ($γγ$) and triboson channels ($Zγγ$, $ZZγ$, $WWγ$) imposed by the $SU(2)_{L}\times U(1)_{Y}$ symmetry of the Standard Model (SM) in certain classes of models. To illustrate this idea we choose a simple model that has all these channels. In this model, the same physics can give rise to $γ+$MET instead of $γγ$ and 2 bosons plus missing energy instead of 3-boson channels. We analyze existing constraints and previous searches and show that channels $WWγ$ and especially $Zγ+$MET have a potential to discover new physics at the LHC.

hep-ph↗

arXiv2018

Constraining self-interacting dark matter with scaling laws of observed halo surface densities

The observed surface densities of dark matter halos are known to follow a simple scaling law, ranging from dwarf galaxies to galaxy clusters, with a weak dependence on their virial mass. Here we point out that this can not only be used to provide a method to determine the standard relation between halo mass and concentration, but also to use large samples of objects in order to place constraints on dark matter self-interactions that can be more robust than constraints derived from individual objects. We demonstrate our method by considering a sample of about 50 objects distributed across the whole halo mass range, and by modelling the effect of self-interactions in a way similar to what has been previously done in the literature. Using additional input from simulations then results in a constraint on the self-interaction cross section per unit dark matter mass of about $σ/m_χ\lesssim 0.3$ cm$^2$/g. We expect that these constraints can be significantly improved in the future, and made more robust, by i) an improved modelling of the effect of self-interactions, both theoretical and by comparison with simulations, ii) taking into account a larger sample of objects and iii) by reducing the currently still relatively large uncertainties that we conservatively assign to the surface densities of individual objects. The latter can be achieved in particular by using kinematic observations to directly constrain the average halo mass inside a given radius, rather than fitting the data to a pre-selected profile and then reconstruct the mass. For a velocity-independent cross-section, our current result is formally already somewhat smaller than the range $0.5-5$ cm$^2$/g that has been invoked to explain potential inconsistencies between small-scale observations and expectations in the standard collisionless cold dark matter paradigm.

astro-ph.CO↗