13,386 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

    Signs of heavy Higgs bosons at CLIC: An e+e−e^+ e^- road to the Electroweak Phase Transition

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    We analyse the sensitivity of the proposed Compact Linear Collider (CLIC) to the existence of beyond the Standard Model (SM) Higgs bosons through their decays into pairs of massive gauge bosons H→VVH \to VV and SM-like Higgses H→hhH \to hh, considering CLIC centre of mass energies s=1.4\sqrt{s} = 1.4 TeV and 33 TeV. We find that resonant di-Higgs searches at CLIC would allow for up to two orders of magnitude improvement w.r.t. the sensitivity achievable by HL-LHC in the mass range mH∈[250 GeV, 1 TeV]m_H \in [250\,\mathrm{GeV},\, 1 \,\mathrm{TeV}]. Focusing then on a real singlet extension of the SM, we explore the prospects of heavy Higgs searches at CLIC for probing the regions of parameter space yielding a strongly first order electroweak phase transition that could generate the observed matter-antimatter asymmetry of the Universe. Our study illustrates the complementarity between CLIC and other possible future colliders like FCC-ee in probing singlet extensions of the SM, and shows that high-energy e+e−e^+ e^- colliders provide a powerful means to unravel the nature of electroweak symmetry breaking in the early Universe.Comment: 27 pages, 15 figure

    Fatigue resistance of new and used nickel-titanium rotary instruments: a comparative study

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    Aim of the present study was twofold. First, to evaluate in vitro, the performance of two different NiTi rotary instruments in one molar case; then, to evaluate their resistance to cyclic fatigue, compared to new ones

    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

    Physics at LHC

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    The prospects for physics at the LHC are discussed, starting with the foretaste, preparation (and perhaps scoop) provided by the Tevatron, in particular, and then continuing through the successive phases of LHC operation. These include the start-up phase, the early physics runs, the possible search for new physics in double diffraction, the continuation to nominal LHC running, and the possible upgrade of the LHC luminosity. Emphasis is placed on the prospects for Higgs physics and the search for supersymmetry. The progress and discoveries of the LHC will set the time-scale and agenda for the major future accelerator projects that will follow it.Comment: 21 pages, 12 figures, Concluding talk at the Physics at LHC conference, Krakow, July 200

    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

    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

    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

    Summary of ICHEP 2004

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    Aspects of ICHEP 2004 are summarized from a theoretical point of view. QCD works, new NNLO calculations are becoming available and new string calculational tools are emerging, but no conclusions can yet be drawn about the discovery of the quark-gluon plasma or pentaquarks. The small upward shift in the experimental value of m_t raises somewhat the central value of the Higgs mass extracted from a global electroweak fit, and the CKM model describes well the data from the B factories. The Super-Kamiokande, KamLAND and K2K experiments have evidence for oscillation dips in their neutrino data. Little Higgs models are interesting alternatives to low-energy supersymmetry for stabilizing the electroweak scale. Convincing experimental evidence for dark matter particles is still lacking. The LHC is on its way, the technology choice clarifies the roadmap for the ILC, and a multi-TeV CLIC would also have rich physics agenda.Comment: 19 pages LaTeX, 12 eps figures, Summary of the International Conference on High-Energy Physics, Beijing, China, August 200
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