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  • 1. Betti, M. G.
    et al.
    Biasotti, M.
    Bosca, A.
    Calle, F.
    Canci, N.
    Cavoto, G.
    Chang, C.
    Cocco, A. G.
    Colijn, A. P.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    D'Ambrosio, N.
    De Groot, N.
    de Salas, Pablo Fernández
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Faverzani, M.
    Ferella, Alfredo
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ferri, E.
    Garcia-Abia, P.
    Garcia-Cortes, I
    Garcia Gomez-Tejedor, G.
    Gariazzo, S.
    Gatti, F.
    Gentile, C.
    Giachero, A.
    Gudmundsson, Jón E.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hochberg, Y.
    Kahn, Y.
    Kievsky, A.
    Lisanti, M.
    Mancini-Terracciano, C.
    Mangano, G.
    Marcucci, L. E.
    Mariani, C.
    Martinez, J.
    Messina, M.
    Molinero-Vela, A.
    Monticone, E.
    Morono, A.
    Nucciotti, A.
    Pandolfi, F.
    Parlati, S.
    Pastor, S.
    Pedros, J.
    de los Heros, C. Perez
    Pisanti, O.
    Polosa, A. D.
    Puiu, A.
    Rago, I
    Raitses, Y.
    Rajteri, M.
    Rossi, N.
    Rucandio, I
    Santorelli, R.
    Schaeffner, K.
    Tully, C. G.
    Viviani, M.
    Zhao, F.
    Zurek, K. M.
    Neutrino physics with the PTOLEMY project: active neutrino properties and the light sterile case2019In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 047Article in journal (Refereed)
    Abstract [en]

    The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected cosmological signal. In this paper we discuss in details the theoretical aspects of the experiment and its physics goals. In particular, we mainly address three issues. First we discuss the sensitivity of PTOLEMY to the standard neutrino mass scale. We then study the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, we consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum.

  • 2. Betti, M. G.
    et al.
    Biasotti, M.
    Boscá, A.
    Calle, F.
    Carabe-Lopez, J.
    Cavoto, G.
    Chang, C.
    Chung, W.
    Cocco, A. G.
    Colijn, A. P.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    D'Ambrosio, N.
    de Salas, Pablo F.
    Stockholm University, Faculty of Science, Department of Physics. Instituto de Física Corpuscular (CSIC-Universitat de València), Spain.
    Faverzani, M.
    Ferella, Alfredo
    Stockholm University, Faculty of Science, Department of Physics.
    Ferri, E.
    Garcia-Abia, P.
    Garcia Gomez-Tejedor, G.
    Gariazzo, S.
    Gatti, F.
    Gentile, C.
    Giachero, A.
    Gudmundsson, Jón E.
    Stockholm University, Faculty of Science, Department of Physics. Luleå University of Technology, Sweden.
    Hochberg, Y.
    Kahn, Y.
    Lisanti, M.
    Mancini-Terracciano, C.
    Mangano, G.
    Marcucci, L. E.
    Mariani, C.
    Martínez, J.
    Messina, M.
    Molinero-Vela, A.
    Monticone, E.
    Nucciotti, A.
    Pandolfi, F.
    Pastor, S.
    Pedrós, J.
    de los Heros, C. Pérez
    Pisanti, O.
    Polosa, A. D.
    Puiu, A.
    Raitses, Y.
    Rajteri, M.
    Rossi, N.
    Santorelli, R.
    Schaeffner, K.
    Strid, C. F.
    Stockholm University, Faculty of Science, Department of Physics. Luleå University of Technology, Sweden.
    Tully, C. G.
    Zhao, F.
    Zurek, K. M.
    A design for an electromagnetic filter for precision energy measurements at the tritium endpoint2019In: Progress in Particle and Nuclear Physics, ISSN 0146-6410, E-ISSN 1873-2224, Vol. 106, p. 120-131Article, review/survey (Refereed)
    Abstract [en]

    We present a detailed description of the electromagnetic filter for the PTOLEMY project to directly detect the Cosmic Neutrino Background (CNB). Starting with an initial estimate for the orbital magnetic moment, the higher-order drift process of E x B is configured to balance the gradient-B drift motion of the electron in such a way as to guide the trajectory into the standing voltage potential along the mid-plane of the filter. As a function of drift distance along the length of the filter, the filter zooms in with exponentially increasing precision on the transverse velocity component of the electron kinetic energy. This yields a linear dimension for the total filter length that is exceptionally compact compared to previous techniques for electromagnetic filtering. The parallel velocity component of the electron kinetic energy oscillates in an electrostatic harmonic trap as the electron drifts along the length of the filter. An analysis of the phase-space volume conservation validates the expected behavior of the filter from the adiabatic invariance of the orbital magnetic moment and energy conservation following Liouville's theorem for Hamiltonian systems.

  • 3.
    de Salas, Pablo Fernández
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Malhan, Khyati
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Freese, Katherine
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Nordic Institute for Theoretical Physics (Nordita). University of Michigan, U.S.A..
    Hattori, K.
    Valluri, M.
    On the estimation of the local dark matter density using the rotation curve of the Milky Way2019In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 10, article id 037Article in journal (Refereed)
    Abstract [en]

    The rotation curve of the Milky Way is commonly used to estimate the local dark matter density rho(DM,circle dot). However, the estimates are subject to the choice of the distribution of baryons needed in this type of studies. In this work we explore several Galactic mass models that differ in the distribution of baryons and dark matter, in order to determine rho(DM,circle dot). For this purpose we analyze the precise circular velocity curve measurement of the Milky Way up to similar to 25 kpc from the Galactic centre obtained from Gaia DR2 [1]. We find that the estimated value of rho(DM,circle dot) stays robust to reasonable changes in the spherical dark matter halo. However, we show that rho(DM,circle dot) is affected by the choice of the model for the underlying baryonic components. In particular, we find that rho(DM,circle dot) is mostly sensitive to uncertainties in the disk components of the Galaxy. We also show that, when choosing one particular baryonic model, the estimate of rho(DM,circle dot) has an uncertainty of only about 10% of its best-fit value, but this uncertainty gets much bigger when we also consider the variation of the baryonic model. In particular, the rotation curve method does not allow to exclude the presence of an additional very thin component, that can increase rho(DM,circle dot) by more than a factor of 8 (the thin disk could even be made of dark matter). Therefore, we conclude that exclusively using the rotation curve of the Galaxy is not enough to provide a robust estimate of rho(DM,circle dot). For all the models that we study without the presence of an additional thin component, our resulting estimates of the local dark matter density take values in the range rho(DM,circle dot) similar or equal to 0.3-0.4 GeV/cm(3), consistent with many of the estimates in the literature.

  • 4.
    de Salas, Pablo Fernández
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Institut de Física Corpuscular (CSIC–Universitat de València), Spain.
    Pastor, S.
    Ternes, C. A.
    Thakore, T.
    Tórtola, M.
    Constraining the invisible neutrino decay with KM3NeT-ORCA2019In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 789, p. 472-479Article in journal (Refereed)
    Abstract [en]

    Several theories of particle physics beyond the Standard Model consider that neutrinos can decay. In this work we assume that the standard mechanism of neutrino oscillations is altered by the decay of the heaviest neutrino mass state into a sterile neutrino and, depending on the model, a scalar or a Majoron. We study the sensitivity of the forthcoming KM3NeT-ORCA experiment to this scenario and find that it could improve the current bounds coming from oscillation experiments, where three-neutrino oscillations have been considered, by roughly two orders of magnitude. We also study how the presence of this neutrino decay can affect the determination of the atmospheric oscillation parameters sin(2) theta(23) and Delta m(31)(2), as well as the sensitivity to the neutrino mass ordering.

  • 5. Gariazzo, S.
    et al.
    de Salas, Pablo Fernández
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Pastor, S.
    Thermalisation of sterile neutrinos in the early universe in the 3+1 scheme with full mixing matrix2019In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 014Article in journal (Refereed)
    Abstract [en]

    In the framework of a 3+1 scheme with an additional inert state, we consider the thermalisation of sterile neutrinos in the early Universe taking into account the full 4 x 4 mixing matrix. The evolution of the neutrino energy distributions is found solving the momentum-dependent kinetic equations with full diagonal collision terms, as in previous analyses of flavour neutrino decoupling in the standard case. The degree of thermalisation of the sterile state is shown in terms of the effective number of neutrinos, N-eff, and its dependence on the three additional mixing angles (theta(14), theta(24), theta(34)) and on the squared mass difference Delta m(41)(2) is discussed. Our results are relevant for fixing the contribution of a fourth light neutrino species to the cosmological energy density, whose value is very well constrained by the final Planck analysis. For the preferred region of active-sterile mixing parameters from short-baseline neutrino experiments, we find that the fourth state is fully thermalised (N-eff similar or equal to 4).

  • 6. Mertsch, P.
    et al.
    Parimbelli, G.
    de Salas, Pablo Fernández
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gariazzo, S.
    Lesgourgues, J.
    Pastor, S.
    Neutrino clustering in the Milky Way and beyond2020In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 1, article id 015Article in journal (Refereed)
    Abstract [en]

    The standard cosmological model predicts the existence of a Cosmic Neutrino Background, which has not yet been observed directly. Some experiments aiming at its detection are currently under development, despite the tiny kinetic energy of the cosmological relic neutrinos, which makes this task incredibly challenging. Since massive neutrinos are attracted by the gravitational potential of our Galaxy, they can cluster locally. Neutrinos should be more abundant at the Earth position than at an average point in the Universe. This fact may enhance the expected event rate in any future experiment. Past calculations of the local neutrino clustering factor only considered a spherical distribution of matter in the Milky Way and neglected the influence of other nearby objects like the Virgo cluster, although recent N-body simulations suggest that the latter may actually be important. In this paper, we adopt a back-tracking technique, well established in the calculation of cosmic rays fluxes, to perform the first three-dimensional calculation of the number density of relic neutrinos at the Solar System, taking into account not only the matter composition of the Milky Way, but also the contribution of the Andromeda galaxy and the Virgo cluster. The effect of Virgo is indeed found to be relevant and to depend non-trivially on the value of the neutrino mass. Our results show that the local neutrino density is enhanced by 0.53% for a neutrino mass of 10 meV, 12% for 50 meV, 50% for 100 meV or 500% for 300 meV.

  • 7.
    Widmark, Axel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Malhan, Khyati
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    F. de Salas, Pablo
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sivertsson, Sofia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Measuring the Matter Density of the Galactic Disk Using Stellar StreamsManuscript (preprint) (Other academic)
    Abstract [en]

    We present a novel method for determining the total matter surface density of the Galactic disk by analysing the kinematics of a dynamically cold stellar stream that passes through or close to the Galactic plane. The method relies on the fact that the vertical component of energy for such stream stars is approximately constant, such that their vertical positions and vertical velocities are interrelated via the matter density of the Galactic disk. By testing our method on mock data stellar streams, with realistic phase-space dispersions and Gaia uncertainties, we demonstrate that it is applicable to small streams out to a distance of a few kilo-parsec, and that the surface density of the disk can be determined to a precision of 6 %. This method is complementary to other mass measurements. In particular, it does not rely on any equilibrium assumption for stars in the Galactic disk, and also makes it possible to measure the surface density to good precision at large distances from the Sun. Such measurements would inform us of the matter composition of the Galactic disk and its spatial variation, place stronger constraints on dark disk sub-structure, and even diagnose possible non-equilibrium effects that bias other types of dynamical mass measurements.

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