4th Week Paper List
First results from DAMA/LIBRA and the combined results with DAMA/NaI
R. Bernabei (1,2), P. Belli (2), F. Cappella (3,4), R. Cerulli (5), C.J. Dai (6), A. d'Angelo (3,4), H.L. He (6), A. Incicchitti (4), H.H. Kuang (6), J.M. Ma (6), F. Montecchia (1,2), F. Nozzoli (1,2), D. Prosperi (3,4), X.D. Sheng (6), Z.P. Ye (6,7) ((1) Univ. Roma Tor Vergata, (2) INFN Roma Tor Vergata, (3) Univ. Roma, (4) INFN Roma, (5) INFN LNGS, (6) IHEP Beijing, (7) Univ. Jing Gangshan)
The highly radiopure ≃ 250 kg NaI(Tl) DAMA/LIBRA set-up is running at the Gran Sasso National Laboratory of the I.N.F.N.. In this paper the first result obtained by exploiting the model independent annual modulation signature for Dark Matter (DM) particles is presented. It refers to an exposure of 0.53 ton×yr. The collected DAMA/LIBRA data satisfy all the many peculiarities of the DM annual modulation signature. Neither systematic effects nor side reactions can account for the observed modulation amplitude and contemporaneously satisfy all the several requirements of this DM signature. Thus, the presence of Dark Matter particles in the galactic halo is supported also by DAMA/LIBRA and, considering the former DAMA/NaI and the present DAMA/LIBRA data all together (total exposure 0.82 ton×yr), the presence of Dark Matter particles in the galactic halo is supported at 8.2 σ C.L.
Links : https://arxiv.org/abs/0804.2741
Toward (Finally!) Ruling Out Z and Higgs Mediated Dark Matter Models
Miguel Escudero, Asher Berlin, Dan Hooper, Meng-Xiang Lin
In recent years, direct detection, indirect detection, and collider experiments have placed increasingly stringent constraints on particle dark matter, exploring much of the parameter space associated with the WIMP paradigm. In this paper, we focus on the subset of WIMP models in which the dark matter annihilates in the early universe through couplings to either the Standard Model Z or the Standard Model Higgs boson. Considering fermionic, scalar, and vector dark matter candidates within a model-independent context, we find that the overwhelming majority of these dark matter candidates are already ruled out by existing experiments. In the case of Z mediated dark matter, the only scenario that is not already experimentally excluded is that of a fermionic dark matter candidate with an axial coupling and with a mass within a few GeV of the Z resonance (mDM≃mZ/2). Several Higgs mediated scenarios are currently viable if the mass of the dark matter is near the Higgs pole (mDM≃mH/2). Otherwise, the only scenarios that are not excluded are those in which the dark matter is a scalar (vector) heavier than 400 GeV (1160 GeV) with a Higgs portal coupling, or a fermion with a pseudoscalar (CP violating) coupling to the Standard Model Higgs boson. With the exception of dark matter with a purely pseudoscalar coupling to the Higgs, it is anticipated that planned direct detection experiments will probe the entire range of models considered in this study
Links : https://arxiv.org/abs/1609.09079
The core-halo mass relation of ultra-light axion dark matter from merger history
Xiaolong Du, Christoph Behrens, Jens C. Niemeyer, Bodo Schwabe
In the context of structure formation with ultra-light axion dark matter, we offer an alternative explanation for the mass relation of solitonic cores and their host halos observed in numerical simulations. Our argument is based entirely on the mass gain that occurs during major mergers of binary cores and largely independent of the initial core-halo mass relation assigned to hosts that have just collapsed. We find a relation between the halo mass Mh and corresponding core mass Mc, Mc∝M2β−1h, where (1−β) is the core mass loss fraction. Following the evolution of core masses in stochastic merger trees, we find empirical evidence for our model. Our results are useful for statistically modeling the effects of dark matter cores on the properties of galaxies and their substructures in axion dark matter cosmologies.
Links : https://arxiv.org/abs/1609.09414
Patrick deNiverville, Chien-Yi Chen, Maxim Pospelov, Adam Ritz
We analyze the prospects for detection of light sub-GeV dark matter produced in experiments designed to study the properties of neutrinos, such as MiniBooNE, T2K, SHiP, DUNE etc. We present an improved production model, when dark matter couples to hadronic states via a dark photon or baryonic vector mediator, incorporating bremsstrahlung of the dark vector. In addition to elastic scattering, we also study signatures of light dark matter undergoing deep inelastic or quasi-elastic NCπ0-like scattering in the detector producing neutral pions, which for certain experiments may provide the best sensitivity. An extensive appendix provides documentation for a publicly available simulation tool {\tt BdNMC} that can be applied to determine the hidden sector dark matter production and scattering rate at a range of proton fixed target experiments.
Links : https://arxiv.org/abs/1609.01770
The Mass Function of Unprocessed Dark Matter Halos and Merger Tree Branching Rates
Andrew J. Benson (1) ((1) Carnegie Observatories)
A common approach in semi-analytic modeling of galaxy formation is to construct Monte Carlo realizations of merger histories of dark matter halos whose masses are sampled from a halo mass function. Both the mass function itself, and the merger rates used to construct merging histories are calibrated to N-body simulations. Typically, "backsplash" halos (those which were once subhalos within a larger halo, but which have since moved outside of the halo) are counted in both the halo mass function, and in the merger rates (or, equivalently, progenitor mass functions). This leads to a double-counting of mass in Monte Carlo merger histories which will bias results relative to N-body results. We measure halo mass functions and merger rates with this double-counting removed in a large, cosmological N-body simulation with cosmological parameters consistent with current constraints. Furthermore, we account for the inherently noisy nature of N-body halo mass estimates when fitting functions to N-body data, and show that ignoring these errors leads to a significant systematic bias given the precision statistics available from state-of-the-art N-body cosmological simulations.
Links : https://arxiv.org/abs/1610.01057
Carsten Rott, Seongjin In, Jason Kumar, David Yaylali
We consider the use of directionality in the search for monoenergetic sub-GeV neutrinos arising from the decay of stopped kaons, which can be produced by dark matter annihilation in the core of the Sun. When these neutrinos undergo charged-current interactions with a nucleus at a neutrino detector, they often eject a proton which is highly peaked in the forward direction. The direction of this track can be measured at DUNE, allowing one to distinguish signal from background by comparing on-source and off-source event rates. We find that directional information can enhance the signal to background ratio by up to a factor of 5.
Links : https://arxiv.org/abs/1609.04876
Gregory A. Dooley, Annika H. G. Peter, Tianyi Yang, Beth Willman, Brendan F. Griffen, Anna Frebel
A recent surge in the discovery of new ultrafaint dwarf satellites of the Milky Way has inspired the idea of searching for faint satellites, 103M⊙<M∗<106M⊙, around less massive field galaxies in the Local Group. Such satellites would be subject to weaker environmental influences than Milky Way satellites, and could lead to new insights on low mass galaxy formation. In this paper, we predict the number of luminous satellites expected around field dwarf galaxies by applying several abundance matching models and a reionization model to the dark-matter only Caterpillar simulation suite. For three of the four abundance matching models used, we find a >99% chance that at least one satellite with stellar mass M∗>105M⊙ exists around the combined five Local Group field dwarf galaxies with the largest stellar mass. When considering satellites with M∗>104M⊙, we predict a combined 5−25 satellites for the five largest field dwarfs, and 10−50 for the whole Local Group field dwarf population. Because of the relatively small number of predicted dwarfs, and their extended spatial distribution, a large fraction each Local Group dwarf's virial volume will need to be surveyed to guarantee discoveries. We compute the predicted number of satellites in a given field of view of specific Local Group galaxies, as a function of minimum satellite luminosity, and explicitly obtain such values for the Solitary Local dwarfs survey. Uncertainties in abundance matching and reionization models are large, implying that comprehensive searches could lead to refinements of both models
Links : https://arxiv.org/abs/1610.00708