1,775 research outputs found

    Running of Low-Energy Neutrino Masses, Mixing Angles and CP Violation

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    We calculate the running of low-energy neutrino parameters from the bottom up, parameterizing the unknown seesaw parameters in terms of the dominance matrix RR. We find significant running only if the RR matrix is non-trivial and the light-neutrino masses are moderately degenerate. If the light-neutrino masses are very hierarchical, the quark-lepton complementarity relation θc+θ12=π/4\theta_c + \theta_{12} = \pi/4 is quite stable, but θ13,23\theta_{13,23} may run beyond their likely future experimental errors. The running of the oscillation phase δ\delta is enhanced by the smallness of θ13\theta_{13}, and jumps in the mixing angles occur in cases where the light-neutrino mass eigenstates cross.Comment: 14 pages, 7 figure

    Implications of XENON100 and LHC results for Dark Matter models

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    We perform a fit to the recent Xenon100 data and study its implications for Dark Matter scenarios. We find that Inelastic Dark Matter is disfavoured as an explana- tion to the DAMA/LIBRA annual modulation signal. Concerning the scalar singlet DM model, we find that the Xenon100 data disfavors its constrained limit. We study the CMSSM as well as the low scale phenomenological MSSM taking into account latest Tevatron and LHC data (1.1/fb) about sparticles and Bs \rightarrow {\mu}{\mu}. After the EPS 2011 conference, LHC excludes the "Higgs-resonance" region of DM freeze-out and Xenon100 disfavors the "well-tempered" bino/higgsino, realized in the "focus-point" region of the CMSSM parameter space. The preferred region shifts to heavier sparticles, higher fine-tuning, higher tan {\beta} and the quality of the fit deteriorates.Comment: v4: addendum included at the light of the Dark Matter and Higgs data presented during july 2012 by the Xenon100, ATLAS and CMS collaboration

    Matter parity as the origin of scalar Dark Matter

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    We extend the concept of matter parity PM=(−1)3(B−L)P_M=(-1)^{3(B-L)} to non-supersymmetric theories and argue that PMP_M is the natural explanation to the existence of Dark Matter of the Universe. We show that the non-supersymmetric Dark Matter must be contained in scalar 16 representation(s) of SO(10),SO(10), thus the unique low energy Dark Matter candidates are PMP_M-odd complex scalar singlet(s) SS and inert scalar doublet(s) H2.H_2. We have calculated the thermal relic Dark Matter abundance of the model and shown that its minimal form may be testable at LHC via the SM Higgs boson decays H1→DMDM.H_1\to DM DM. The PAMELA anomaly can be explained with the decays DM→νlWDM\to \nu l W induced via seesaw-like operator which is additionally suppressed by Planck scale. Because the SM fermions are odd under matter parity too, the DM sector is just our scalar relative.Comment: The origin of scalar DM is emphasized, version accepted by PR

    Evolutionary algorithms for hyperparameter optimization in machine learning for application in high energy physics

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    The analysis of vast amounts of data constitutes a major challenge in modern high energy physics experiments. Machine learning (ML) methods, typically trained on simulated data, are often employed to facilitate this task. Several choices need to be made by the user when training the ML algorithm. In addition to deciding which ML algorithm to use and choosing suitable observables as inputs, users typically need to choose among a plethora of algorithm-specific parameters. We refer to parameters that need to be chosen by the user as hyperparameters. These are to be distinguished from parameters that the ML algorithm learns autonomously during the training, without intervention by the user. The choice of hyperparameters is conventionally done manually by the user and often has a significant impact on the performance of the ML algorithm. In this paper, we explore two evolutionary algorithms: particle swarm optimization (PSO) and genetic algorithm (GA), for the purposes of performing the choice of optimal hyperparameter values in an autonomous manner. Both of these algorithms will be tested on different datasets and compared to alternative methods.Comment: Corrected typos. Removed a remark on page 2 regarding the similarity of minimization and maximization problem. Removed a remark on page 9 (Summary) regarding thee ANN, since this was not studied in the pape

    Dark Matter as the signal of Grand Unification

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    We argue that the existence of Dark Matter (DM) is a possible consequence of GUT symmetry breaking. In GUTs like SO(10), discrete Z_2 matter parity (-1)^{3(B-L)} survives despite of broken B-L, and group theory uniquely determines that the only possible Z_2-odd matter multiplets belong to representation 16. We construct the minimal non-SUSY SO(10) model containing one scalar 16 for DM and study its predictions below M_{G}. We find that EWSB occurs radiatively due to DM couplings to the SM Higgs boson. For thermal relic DM the mass range M_{DM}\sim (0.1-1) TeV is predicted by model perturbativity up to M_{G}. For M_{DM}\sim (1) TeV to explain the observed cosmic ray anomalies with DM decays, there exists a lower bound on the spin-independent direct detection cross section within the reach of planned experiments.Comment: DM direct detection cross section is corrected by adding s-quark contribution which turned out to be the dominant one. The prediction is just below the present CDMS and XENON10 bound. Extended version, RGE-s included, new references adde

    Direct detection and CMB constraints on light DM scenario of top quark asymmetry and dijet excess at Tevatron

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    We study in detail the model by Isidori and Kamenik that is claimed to explain the top quark forward-backward asymmetry at Tevatron, provide GeV-scale dark matter (DM), and possibly improve the agreement between data and theory in Tevatron W+jj events. We compute the DM thermal relic density, the spin-independent DM-nucleon scattering cross section, and the cosmic microwave background constraints on both Dirac and Majorana neutralino DM in the parameter space that explains the top asymmetry. A stable light neutralino is not allowed unless the local DM density is 3-4 times smaller than expected, in which case Dirac DM with mass around 3 GeV may be possible, to be tested by the Planck mission. The model predicts a too broad excess in the dijet distribution and a strong modification of the missing E_T distribution in W+jj events.Comment: 4 pages, 4 figures; fig. 2 corrected, conclusions slightly changed, matches published versio

    Implications of the 125 GeV Higgs boson for scalar dark matter and for the CMSSM phenomenology

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    We study phenomenological implications of the ATLAS and CMS hint of a 125±1125\pm 1 GeV Higgs boson for the singlet, and singlet plus doublet non-supersymmetric dark matter models, and for the phenomenology of the CMSSM. We show that in scalar dark matter models the vacuum stability bound on Higgs boson mass is lower than in the standard model and the 125 GeV Higgs boson is consistent with the models being valid up the GUT or Planck scale. We perform a detailed study of the full CMSSM parameter space keeping the Higgs boson mass fixed to 125±1125\pm 1 GeV, and study in detail the freeze-out processes that imply the observed amount of dark matter. After imposing all phenomenological constraints except for the muon (g−2)μ,(g-2)_\mu, we show that the CMSSM parameter space is divided into well separated regions with distinctive but in general heavy sparticle mass spectra. Imposing the (g−2)μ(g-2)_\mu constraint introduces severe tension between the high SUSY scale and the experimental measurements -- only the slepton co-annihilation region survives with potentially testable sparticle masses at the LHC. In the latter case the spin-independent DM-nucleon scattering cross section is predicted to be below detectable limit at the XENON100 but might be of measurable magnitude in the general case of light dark matter with large bino-higgsino mixing and unobservably large scalar masses.Comment: 17 pages, 7 figures. v3: same as published versio

    Enhanced anti-deuteron Dark Matter signal and the implications of PAMELA

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    We show that the jet structure of DM annihilation or decay products enhances the anti-deuterium production rate by orders of magnitude compared to the previous computations done assuming a spherically symmetric coalescence model. In particular, in the limit of heavy DM, M >> m_p, we get a constant rather than 1/M^2 suppressed anti-deuterium production rate. Therefore, a detectable anti-deuterium signal is compatible with the lack of an excess in the anti-proton PAMELA flux. Most importantly, cosmic anti-deuterium searches become sensitive to the annihilations or decays of heavy DM, suggesting to extend the experimental anti-deuterium searches above the O(1) GeV scale.Comment: 13 pages, 7 figures. Final versio

    PPPC 4 DM ID: A Poor Particle Physicist Cookbook for Dark Matter Indirect Detection

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    We provide ingredients and recipes for computing signals of TeV-scale Dark Matter annihilations and decays in the Galaxy and beyond. For each DM channel, we present the energy spectra of electrons and positrons, antiprotons, antideuterons, gamma rays, neutrinos and antineutrinos e, mu, tau at production, computed by high-statistics simulations. We estimate the Monte Carlo uncertainty by comparing the results yielded by the Pythia and Herwig event generators. We then provide the propagation functions for charged particles in the Galaxy, for several DM distribution profiles and sets of propagation parameters. Propagation of electrons and positrons is performed with an improved semi-analytic method that takes into account position-dependent energy losses in the Milky Way. Using such propagation functions, we compute the energy spectra of electrons and positrons, antiprotons and antideuterons at the location of the Earth. We then present the gamma ray fluxes, both from prompt emission and from Inverse Compton scattering in the galactic halo. Finally, we provide the spectra of extragalactic gamma rays. All results are available in numerical form and ready to be consumed.Comment: 57 pages with many figures and tables. v4: updated to include a 125 higgs boson, computation and discussion of extragalactic spectra corrected, some other typos fixed; all these corrections and updates are reflected on the numerical ingredients available at http://www.marcocirelli.net/PPPC4DMID.html they correspond to Release 2.
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