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Coloma, P., Esteban, I., Gonzalez-Garcia, M. C., Larizgoitia, L., Monrabal, F., & Palomares-Ruiz, S. (2022). Bounds on new physics with data of the Dresden-II reactor experiment and COHERENT. J. High Energy Phys., 05(5), 037–33pp.
Abstract: Coherent elastic neutrino-nucleus scattering was first experimentally established five years ago by the COHERENT experiment using neutrinos from the spallation neutron source at Oak Ridge National Laboratory. The first evidence of observation of coherent elastic neutrino-nucleus scattering with reactor antineutrinos has now been reported by the Dresden-II reactor experiment, using a germanium detector. In this paper, we present constraints on a variety of beyond the Standard Model scenarios using the new Dresden-II data. In particular, we explore the constraints imposed on neutrino nonstandard interactions, neutrino magnetic moments, and several models with light scalar or light vector mediators. We also quantify the impact of their combination with COHERENT (CsI and Ar) data. In doing so, we highlight the synergies between spallation neutron source and nuclear reactor experiments regarding beyond the Standard Model searches, as well as the advantages of combining data obtained with different nuclear targets. We also study the possible signal from beyond the Standard Model scenarios due to elastic scattering off electrons (which would pass selection cuts of the COHERENT CsI and the Dresden-II experiments) and find more stringent constraints in certain parts of the parameter space than those obtained considering coherent elastic neutrino-nucleus scattering.
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Garani, R., & Palomares-Ruiz, S. (2022). Evaporation of dark matter from celestial bodies. J. Cosmol. Astropart. Phys., 05(5), 042–53pp.
Abstract: Scatterings of galactic dark matter (DM) particles with the constituents of celestial bodies could result in their accumulation within these objects. Nevertheless, the finite temperature of the medium sets a minimum mass, the evaporation mass, that DM particles must have in order to remain trapped. DM particles below this mass are very likely to scatter to speeds higher than the escape velocity, so they would be kicked out of the capturing object and escape. Here, we compute the DM evaporation mass for all spherical celestial bodies in hydrostatic equilibrium, spanning the mass range [10(-)(10) – 10(2)] M-circle dot, for constant scattering cross sections and s-wave annihilations. We illustrate the critical importance of the exponential tail of the evaporation rate, which has not always been appreciated in recent literature, and obtain a robust result: for the geometric value of the scattering cross section and for interactions with nucleons, at the local galactic position, the DM evaporation mass for all spherical celestial bodies in hydrostatic equilibrium is approximately given by E-c/T-chi similar to 30, where E-c is the escape energy of DM particles at the core of the object and T-chi is their temperature. In that case, the minimum value of the DM evaporation mass is obtained for super-Jupiters and brown dwarfs, m(ev)(ap) similar or equal to 0.7 GeV. For other values of the scattering cross section, the DM evaporation mass only varies by a factor smaller than three within the range 10(-41) cm(2) <= sigma(p) <= 10(-31) cm(2), where sigma(p) is the spin-independent DM-nucleon scattering cross section. Its dependence on parameters such as the galactic DM density and velocity, or the scattering and annihilation cross sections is only logarithmic, and details on the density and temperature profiles of celestial bodies have also a small impact.
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Farzan, Y., & Palomares-Ruiz, S. (2014). Dips in the diffuse supernova neutrino background. J. Cosmol. Astropart. Phys., 06(6), 014–21pp.
Abstract: Scalar (fermion) dark matter with mass in the MeV range coupled to ordinary neutrinos and another fermion (scalar) is motivated by scenarios that establish a link between radiatively generated neutrino masses and the dark matter relic density. With such a coupling, cosmic supernova neutrinos, on their way to us, could resonantly interact with the background (lark matter particles, giving rise to a dip in their redshift-integrated spectra. Current and future neutrino detectors, such as Super-Kamiokande. LENA and HyperKamiokande, could be able to detect this distortion.
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Moline, A., Ibarra, A., & Palomares-Ruiz, S. (2015). Future sensitivity of neutrino telescopes to dark matter annihilations from the cosmic diffuse neutrino signal. J. Cosmol. Astropart. Phys., 06(6), 005–34pp.
Abstract: Cosmological observations and cold dark matter N-body simulations indicate that our Universe is populated by numerous halos, where dark matter particles annihilate, potentially producing Standard Model particles. In this paper we calculate the contribution to the diffuse neutrino background from dark matter annihilations in halos at all redshifts and we estimate the future sensitivity to the annihilation cross section of neutrino telescopes such as IceCube or ANTARES. We consider various parametrizations to describe the internal halo properties and for the halo mass function in order to bracket the theoretical uncertainty in the limits from the modeling of the cosmological annihilation flux. We find that observations of the cosmic diffuse neutrino flux at large angular distances from the galactic center lead to constraints on the dark matter annihilation cross section which are complementary to ( and for some extrapolations of the astrophysical parameters, better than) those stemming from observations of the Milky Way halo, especially for neutrino telescopes not pointing directly to the Milky Way center, as is the case of IceCube.
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Escudero, M., Lopez-Honorez, L., Mena, O., Palomares-Ruiz, S., & Villanueva-Domingo, P. (2018). A fresh look into the interacting dark matter scenario. J. Cosmol. Astropart. Phys., 06(6), 007–35pp.
Abstract: The elastic scattering between dark matter particles and radiation represents an attractive possibility to solve a number of discrepancies between observations and standard cold dark matter predictions, as the induced collisional damping would imply a suppression of small-scale structures. We consider this scenario and confront it with measurements of the ionization history of the Universe at several redshifts and with recent estimates of the counts of Milky Way satellite galaxies. We derive a conservative upper bound on the dark matter photon elastic scattering cross section of sigma gamma DM < 8 x 10(-10) sigma(T) (m(DM)/GeV) at 95% CL, about one order of magnitude tighter than previous constraints from satellite number counts. Due to the strong degeneracies with astrophysical parameters, the bound on the dark matter-photon scattering cross section derived here is driven by the estimate of the number of Milky Way satellite galaxies. Finally, we also argue that future 21 cm probes could help in disentangling among possible non-cold dark matter candidates, such as interacting and warm dark matter scenarios. Let us emphasize that bounds of similar magnitude to the ones obtained here could be also derived for models with dark matter-neutrino interactions and would be as constraining as the tightest limits on such scenarios.
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Jeong, Y. S., Palomares-Ruiz, S., Reno, M. H., & Sarcevic, I. (2018). Probing secret interactions of eV-scale sterile neutrinos with the diffuse supernova neutrino background. J. Cosmol. Astropart. Phys., 06(6), 019–43pp.
Abstract: Sterile neutrinos with mass in the eV-scale and large mixings of order theta(0) similar or equal to 0.1 could explain some anomalies found in short-baseline neutrino oscillation data. Here, we revisit a neutrino portal scenario in which eV-scale sterile neutrinos have self-interactions via a new gauge vector boson phi. Their production in the early Universe via mixing with active neutrinos can be suppressed by the induced effective potential in the sterile sector. We study how different cosmological observations can constrain this model, in terms of the mass of the new gauge boson, M-phi, and its coupling to sterile neutrinos, g(s). Then, we explore how to probe part of the allowed parameter space of this particular model with future observations of the diffuse supernova neutrino background by the Hyper-Kamiokande and DUNE detectors. For M-phi similar to 5 – 10 keV and g(s) similar to 10-(4) – 10(-2), as allowed by cosmological constraints, we find that interactions of diffuse supernova neutrinos with relic sterile neutrinos on their way to the Earth would result in significant dips in the neutrino spectrum which would produce unique features in the event spectra observed in these detectors.
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Lopez-Honorez, L., Mena, O., Palomares-Ruiz, S., Villanueva-Domingo, P., & Witte, S. J. (2020). Variations in fundamental constants at the cosmic dawn. J. Cosmol. Astropart. Phys., 06(6), 026–25pp.
Abstract: The observation of space-time variations in fundamental constants would provide strong evidence for the existence of new light degrees of freedom in the theory of Nature. Robustly constraining such scenarios requires exploiting observations that span different scales and probe the state of the Universe at different epochs. In the context of cosmology, both the cosmic microwave background and the Lyman-a forest have proven to be powerful tools capable of constraining variations in electromagnetism, however at the moment there do not exist cosmological probes capable of bridging the gap between recombination and reionization. In the near future, radio telescopes will attempt to measure the 21 cm transition of neutral hydrogen during the epochs of reionization and the cosmic dawn (and potentially the tail end of the dark ages); being inherently sensitive to electromagnetic phenomena, these experiments will offer a unique perspective on space-time variations of the fine-structure constant and the electron mass. We show here that large variations in these fundamental constants would produce features on the 21 cm power spectrum that may be distinguishable from astrophysical uncertainties. Furthermore, we forecast the sensitivity for the Square Kilometer Array, and show that the 21 cm power spectrum may be able to constrain variations at the level of O(10(-3)).
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Lopez-Honorez, L., Mena, O., Palomares-Ruiz, S., & Vincent, A. C. (2013). Constraints on dark matter annihilation from CMB observations before Planck. J. Cosmol. Astropart. Phys., 07(7), 046–26pp.
Abstract: We compute the bounds on the dark matter (DM) annihilation cross section using the most recent Cosmic Microwave Background measurements from WMAP9, SPT'11 and ACT'10. We consider DM with mass in the MeV-TeV range annihilating 100% into either an e(+)e(-) or a mu(+)mu(-) pair. We consider a realistic energy deposition model, which includes the dependence on the redshift, DM mass and annihilation channel. We exclude the canonical thermal relic abundance cross section (<sigma nu > = 3 x 10(-26) cm(3)s(-1)) for DM masses below 30 GeV and 15 GeV for the e(+)e(-) and mu(+)mu(-) channels, respectively. A priori, DM annihilating in halos could also modify the reionization history of the Universe at late times. We implement a realistic halo model taken from results of state-of-the-art N-body simulations and consider a mixed reionization mechanism, consisting on reionization from DM as well as from first stars. We find that the constraints on DM annihilation remain unchanged, even when large uncertainties on the halo model parameters are considered.
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Bhattacharya, A., Esmaili, A., Palomares-Ruiz, S., & Sarcevic, I. (2017). Probing decaying heavy dark matter with the 4-year IceCube HESE data. J. Cosmol. Astropart. Phys., 07(7), 027–36pp.
Abstract: After the first four years of data taking, the IceCube neutrino telescope has observed 54 high-energy starting events (HESE) with deposited energies between 20TeV and 2PeV. The background from atmospheric muons and neutrinos is expected to be of about 20 events, all below 100TeV, thus pointing towards the astrophysical origin of about 8 events per year in that data set. However, their precise origin remains unknown. Here, we perform a detailed analysis of this event sample (considering simultaneously the energy, hemisphere and topology of the events) by assuming two contributions for the signal events: an isotropic power-law flux and a flux from decaying heavy dark matter. We fit the mass and lifetime of the dark matter and the normalization and spectral index of an isotropic power-law flux, for various decay channels of dark matter. We find that a significant contribution from dark matter decay is always slightly favored, either to explain the excess below 100TeV, as in the case of decays to quarks or, as in the case of neutrino channels, to explain the three multi-PeV events. Also, we consider the possibility to interpret all the data by dark matter decays only, considering various combinations of two decay channels. We show that the decaying dark matter scenario provides a better fit to HESE data than the isotropic power-law flux.
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Olivares-Del Campo, A., Boehm, C., Palomares-Ruiz, S., & Pascoli, S. (2018). Dark matter-neutrino Interactions through the lens of their cosmological Implications. Phys. Rev. D, 97(7), 075039–23pp.
Abstract: Dark matter and neutrinos provide the two most compelling pieces of evidence for new physics beyond the Standard Model of particle physics, but they are often treated as two different sectors. The aim of this paper is to determine whether there are viable particle physics frameworks in which dark matter can be coupled to active neutrinos. We use a simplified model approach to determine all possible scenarios where there is such a coupling and study their astrophysical and cosmological signatures. We find that dark matter-neutrino interactions have an impact on structure formation and lead to indirect detection signatures when the coupling between dark matter and neutrinos is sufficiently large. This can be used to exclude a large fraction of the parameter space. In most cases, dark matter masses up to a few MeV and mediator masses up to a few GcV are ruled out. The exclusion region can be further extended when dark matter is coupled to a spin-1 mediator or when the dark matter particle and the mediator are degenerate in mass if the mediator is a spin-0 or spin-1/2 particle.
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