14,500 research outputs found

    The Heliosphere---Blowing in the Interstellar Wind

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    Measurements of the velocity of interstellar HeI inside of the heliosphere have been conducted over the past forty years. These historical data suggest that the ecliptic longitude of the direction of the interstellar flow has increased at an average rate of about 0.19 degrees per year over time. Possible astronomical explanations for these short-term variations in the interstellar gas entering the heliosphere are presented.Comment: Accepted for the proceedings of Solar Wind 1

    Review of Linac-Ring Type Collider Proposals

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    There are three possibly types of particle colliders schemes: familiar (well known) ring-ring colliders, less familiar however sufficiently advanced linear colliders and less familiar and less advanced linac-ring type colliders. The aim of this paper is two-fold: to present possibly complete list of papers on linac-ring type collider proposals and to emphasize the role of linac-ring type machines for future HEP research.Comment: quality of figures is improved, some misprints are correcte

    Probe of anomalous quartic WWZγWWZ\gamma couplings in the photon-photon collisions

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    In this paper, we examine the potentials of the processes γγ→W+W−Z\gamma \gamma\rightarrow W^{+} W^{-}Z and e+e−→e+γ∗γ∗e−→e+W+W−Ze−e^{+}e^{-} \rightarrow e^{+}\gamma^{*} \gamma^{*} e^{-} \rightarrow e^{+} W^{+} W^{-} Z e^{-} at the CLIC with s=0.5,1.5\sqrt{s}=0.5,1.5 and 33 TeV to investigate anomalous quartic WWZγWWZ\gamma couplings by two different CP-violating and CP-conserving effective Lagrangians. We find 95%95\% confidence level limits on the anomalous coupling parameters at the three CLIC energies and various integrated luminosities. The best limits obtained from the process γγ→W+W−Z\gamma \gamma\rightarrow W^{+} W^{-}Z on the anomalous k0WΛ2\frac{k_{0}^{W}}{\Lambda^{2}}, kcWΛ2\frac{k_{c}^{W}}{\Lambda^{2}} and k2mΛ2\frac{k_{2}^{m}}{\Lambda^{2}} couplings defined by CP-conserving effective Lagrangians are [−1.73; 1.73]×10−7[-1.73;\, 1.73]\times 10^{-7} GeV−2^{-2}, [−2.44; 2.44]×10−7[-2.44;\, 2.44]\times 10^{-7} and [−1.89; 1.89]×10−7[-1.89; \, 1.89]\times 10^{-7} GeV−2^{-2}, while anΛ2\frac{a_{n}}{\Lambda^{2}} coupling determined by CP-violating effective Lagrangians is obtained as [−1.74; 1.74]×10−7[-1.74;\, 1.74]\times 10^{-7} GeV−2^{-2}. In addition, the best limits derived on k0WΛ2\frac{k_{0}^{W}}{\Lambda^{2}}, kcWΛ2\frac{k_{c}^{W}}{\Lambda^{2}} and k2mΛ2\frac{k_{2}^{m}}{\Lambda^{2}} and anΛ2\frac{a_{n}}{\Lambda^{2}} from the process e+e−→e+γ∗γ∗e−→e+W+W−Ze−e^{+}e^{-} \rightarrow e^{+}\gamma^{*} \gamma^{*} e^{-} \rightarrow e^{+} W^{+} W^{-} Z e^{-} are obtained as [−1.09; 1.09]×10−6[-1.09;\, 1.09]\times 10^{-6} GeV−2^{-2}, [−1.54; 1.54]×10−6[-1.54;\, 1.54]\times 10^{-6} GeV−2^{-2}, [−1.18; 1.18]×10−6[-1.18;\, 1.18]\times 10^{-6} and [−1.04; 1.04]×10−6[-1.04;\, 1.04]\times 10^{-6} GeV−2^{-2}, respectively.Comment: 33 pages, 27 figures, 4 tables, version to appear in JHE

    Statistical Modeling of Spatial Extremes

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    The areal modeling of the extremes of a natural process such as rainfall or temperature is important in environmental statistics; for example, understanding extreme areal rainfall is crucial in flood protection. This article reviews recent progress in the statistical modeling of spatial extremes, starting with sketches of the necessary elements of extreme value statistics and geostatistics. The main types of statistical models thus far proposed, based on latent variables, on copulas and on spatial max-stable processes, are described and then are compared by application to a data set on rainfall in Switzerland. Whereas latent variable modeling allows a better fit to marginal distributions, it fits the joint distributions of extremes poorly, so appropriately-chosen copula or max-stable models seem essential for successful spatial modeling of extremes.Comment: Published in at http://dx.doi.org/10.1214/11-STS376 the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Spatial modeling of extreme snow depth

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    The spatial modeling of extreme snow is important for adequate risk management in Alpine and high altitude countries. A natural approach to such modeling is through the theory of max-stable processes, an infinite-dimensional extension of multivariate extreme value theory. In this paper we describe the application of such processes in modeling the spatial dependence of extreme snow depth in Switzerland, based on data for the winters 1966--2008 at 101 stations. The models we propose rely on a climate transformation that allows us to account for the presence of climate regions and for directional effects, resulting from synoptic weather patterns. Estimation is performed through pairwise likelihood inference and the models are compared using penalized likelihood criteria. The max-stable models provide a much better fit to the joint behavior of the extremes than do independence or full dependence models.Comment: Published in at http://dx.doi.org/10.1214/11-AOAS464 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Quantum effects on Higgs-strahlung events at Linear Colliders within the general 2HDM

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    The associated production of neutral Higgs bosons with the Z gauge boson is investigated in the context of the future linear colliders, such as the ILC and CLIC, within the general two-Higgs-doublet model (2HDM). We compute the corresponding production cross-sections at one-loop, in full consistency with the available theoretical and phenomenological constraints. We find that the wave-function renormalization corrections to the external Higgs fields are the dominant source of the quantum effects, which turn out to be large and negative, and located predominantly in the region around \tan\beta=1 and moderate values of the parameter \lambda_5 (being \lambda_5 < 0). This behavior can be ultimately traced back to the enhancement potential of the triple Higgs boson self-couplings, a trademark feature of the 2HDM with no counterpart in the Higgs sector of the Minimal Supersymmetric Standard Model. The predicted Higgs-strahlung rates comfortably reach a few tens of femtobarn, which means barely 10^3 - 10^4 events per 500 inverse femtobarn of integrated luminosity. Due to their great complementarity, we argue that the combined analysis of the Higgs-strahlung events and the previously computed one-loop Higgs-pair production processes could be instrumental to probe the structure of the Higgs sector at future linac facilities.Comment: LaTeX, 16 pages, 9 Figures, 2 Tables. Extended discussion, references added, matches published version in Phys. Rev.

    Establishing the Isolated Standard Model

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    The goal of this article is to initiate a discussion on what it takes to claim "there is no new physics at the weak scale," namely that the Standard Model (SM) is "isolated." The lack of discovery of beyond the SM (BSM) physics suggests that this may be the case. But to truly establish this statement requires proving all "connected" BSM theories are false, which presents a significant challenge. We propose a general approach to quantitatively assess the current status and future prospects of establishing the isolated SM (ISM), which we give a reasonable definition of. We consider broad elements of BSM theories, and show many examples where current experimental results are not sufficient to verify the ISM. In some cases, there is a clear roadmap for the future experimental program, which we outline, while in other cases, further efforts -- both theoretical and experimental -- are needed in order to robustly claim the establishment of the ISM in the absence of new physics discoveries.Comment: 10 pages, 2 figures, 1 tabl

    Constraining the Higgs self couplings at e+e−e^+e^- colliders

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    We study the sensitivity to the shape of the Higgs potential of single, double, and triple Higgs production at future e+e−e^+e^- colliders. Physics beyond the Standard Model is parameterised through the inclusion of higher-dimensional operators (Φ†Φ−v2/2)n/Λ(2n−4)(\Phi^\dagger \Phi- v^2/2)^n/\Lambda^{(2n-4)} with n=3,4n=3,4, which allows a consistent treatment of independent deviations of the cubic and quartic self couplings beyond the tree level. We calculate the effects induced by a modified potential up to one loop in single and double Higgs production and at the tree level in triple Higgs production, for both ZZ boson associated and WW boson fusion production mechanisms. We consider two different scenarios. First, the dimension six operator provides the dominant contribution (as expected, for instance, in a linear effective-field-theory(EFT)); we find in this case that the corresponding Wilson coefficient can be determined at O(10%)\mathcal{O}(10\%) accuracy by just combining accurate measurements of single Higgs cross sections at s^=\sqrt{\hat s}=240-250 GeV and double Higgs production in WW boson fusion at higher energies. Second, both operators of dimension six and eight can give effects of similar order, i.e., independent quartic self coupling deviations are present. Constraints on Wilson coefficients can be best tested by combining measurements from single, double and triple Higgs production. Given that the sensitivity of single Higgs production to the dimension eight operator is presently unknown, we consider double and triple Higgs production and show that combining their information colliders at higher energies will provide first coarse constraints on the corresponding Wilson coefficient.Comment: minor changes, version accepted for publication in JHE

    A two-step approach to model precipitation extremes in California based on max-stable and marginal point processes

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    In modeling spatial extremes, the dependence structure is classically inferred by assuming that block maxima derive from max-stable processes. Weather stations provide daily records rather than just block maxima. The point process approach for univariate extreme value analysis, which uses more historical data and is preferred by some practitioners, does not adapt easily to the spatial setting. We propose a two-step approach with a composite likelihood that utilizes site-wise daily records in addition to block maxima. The procedure separates the estimation of marginal parameters and dependence parameters into two steps. The first step estimates the marginal parameters with an independence likelihood from the point process approach using daily records. Given the marginal parameter estimates, the second step estimates the dependence parameters with a pairwise likelihood using block maxima. In a simulation study, the two-step approach was found to be more efficient than the pairwise likelihood approach using only block maxima. The method was applied to study the effect of El Ni\~{n}o-Southern Oscillation on extreme precipitation in California with maximum daily winter precipitation from 35 sites over 55 years. Using site-specific generalized extreme value models, the two-step approach led to more sites detected with the El Ni\~{n}o effect, narrower confidence intervals for return levels and tighter confidence regions for risk measures of jointly defined events.Comment: Published at http://dx.doi.org/10.1214/14-AOAS804 in the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

    Updated Post-WMAP Benchmarks for Supersymmetry

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    We update a previously-proposed set of supersymmetric benchmark scenarios, taking into account the precise constraints on the cold dark matter density obtained by combining WMAP and other cosmological data, as well as the LEP and b -> s gamma constraints. We assume that R parity is conserved and work within the constrained MSSM (CMSSM) with universal soft supersymmetry-breaking scalar and gaugino masses m_0 and m_1/2. In most cases, the relic density calculated for the previous benchmarks may be brought within the WMAP range by reducing slightly m_0, but in two cases more substantial changes in m_0 and m_1/2 are made. Since the WMAP constraint reduces the effective dimensionality of the CMSSM parameter space, one may study phenomenology along `WMAP lines' in the (m_1/2, m_0) plane that have acceptable amounts of dark matter. We discuss the production, decays and detectability of sparticles along these lines, at the LHC and at linear e+ e- colliders in the sub- and multi-TeV ranges, stressing the complementarity of hadron and lepton colliders, and with particular emphasis on the neutralino sector. Finally, we preview the accuracy with which one might be able to predict the density of supersymmetric cold dark matter using collider measurements.Comment: 43 pages LaTeX, 13 eps figure
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