A
bstract
A search for dark matter and unparticle production at the LHC has been performed using events containing two charged leptons (electrons or muons), consistent with the decay of a Z boson, ...and large missing transverse momentum. This study is based on data collected with the CMS detector in 2015, corresponding to an integrated luminosity of 2.3 fb
−1
of proton-proton collisions at the LHC, at a center-of-mass energy of 13 TeV. No excess over the standard model expectation is observed. Compared to previous searches in this topology, which exclusively relied on effective field theories, the results are interpreted in terms of a simplified model of dark matter production for both vector and axial vector couplings between a mediator and dark matter particles. The first study of this class of models using CMS data at
s
=
13
TeV is presented. Additionally, effective field theories of dark matter and unparticle production are used to interpret the data.
Understanding how pathogens respond to changing environmental conditions is a central challenge in disease ecology. The environmentally sensitive fungal pathogen Batrachochytrium dendrobatidis (Bd), ...which causes the amphibian disease chytridiomycosis, has spread globally causing amphibian extirpations in a wide variety of climatic regions. To gain an in‐depth understanding of Bd's responses to temperature, we used an integrative approach, combining empirical laboratory experiments with mathematical modeling. First, we selected a single Bd isolate and serially propagated two lineages of the isolate for multiple generations in two stable thermal conditions: 4°C (cold‐adapted lineage) and 23°C (warm‐adapted lineage). We quantified the production of infectious zoospores (fecundity), the timing of zoospore release, and zoospore activity in reciprocal temperature transplant experiments in which both Bd lineages were grown in either high or low temperature conditions. We then developed population growth models for the Bd lineages under each set of temperature conditions. We found that Bd had lower population growth rates, but longer periods of zoospore activity in the low temperature treatment (4°C) compared to the high temperature treatment (23°C). This effect was more pronounced in Bd lineages that were propagated in the low temperature treatment (4°C), suggesting a shift in Bd's response to low temperature conditions. Our results provide novel insights into the mechanisms by which Bd can thrive in a wide variety of temperature conditions, potentially altering the dynamics of chytridiomycosis and thus, the propensity for Bd to cause amphibian population collapse. We also suggest that the adaptive responses of Bd to thermal conditions warrant further investigation, especially in the face of global climate change.
Temperature alters development of fungal pathogens such as Batrachochytrium dendrobatidis, a lethal pathogen of amphibians. Yet, it is not clear how this pathogen maintains high virulence in low (sub‐optimal) temperatures. We investigated how Bd responds to temperature treatments when serially propagated in different thermal conditions and found differences in life history characteristics that could explain why Bd maintains high levels of virulence in suboptimal thermal conditions.
A search for events containing four top quarks (tt¯tt¯) is reported from proton–proton collisions recorded by the CMS experiment at s=13 TeV and corresponding to an integrated luminosity of 2.6 fb−1. ...The analysis considers the single-lepton (e or μ)+jets and the opposite-sign dilepton (μ+μ−, μ±e∓, or e+e−)+jets channels. It uses boosted decision trees to combine information on the global event and jet properties to distinguish between tt¯tt¯ and tt¯ production. The number of events observed after all selection requirements is consistent with expectations from background and standard model signal predictions, and an upper limit is set on the cross section for tt¯tt¯ production in the standard model of 94 fb at 95% confidence level (10.2 × the prediction), with an expected limit of 118 fb. This is combined with the results from the published CMS search in the same-sign dilepton channel, resulting in an improved limit of 69 fb at 95% confidence level (7.4 × the prediction), with an expected limit of 71 fb. These are the strongest constraints on the rate of tt¯tt¯ production to date.
A
bstract
Measurements are presented of Wγγ and Zγγ production in proton-proton collisions. Fiducial cross sections are reported based on a data sample corresponding to an integrated luminosity of ...19.4 fb
−1
collected with the CMS detector at a center-of-mass energy of 8 TeV. Signal is identified through the W → ℓν and Z → ℓℓ decay modes, where ℓ is a muon or an electron. The production of Wγγ and Zγγ, measured with significances of 2.6 and 5.9 standard deviations, respectively, is consistent with standard model predictions. In addition, limits on anomalous quartic gauge couplings in Wγγ production are determined in the context of a dimension-8 effective field theory.
We report here the discovery of fossil hominid teeth at Gladysvale, near Johannesburg in the southern Transvaal. This find makes the site the seventh in South Africa to yield australopithecine ...remains and the first new early hominid-bearing locality to be found in this region since 1948. Apart from the hominid specimens, our excavations at Gladysvale have added appreciably to the abundant Plio-Pleistocene fauna previously recorded from the cave deposit. The fauna indicates that savanna conditions prevailed during deposition of at least part of the fill. Preliminary faunal dating gives an age of deposition of between c1.7 and c2.5 mya.
A
bstract
An analysis of dijet events in PbPb and pp collisions is performed to explore the properties of energy loss by partons traveling in a quark-gluon plasma. Data are collected at a ...nucleon-nucleon center-of-mass energy of 2.76 TeV at the LHC. The distribution of transverse momentum (
p
T
) surrounding dijet systems is measured by selecting charged particles in different ranges of
p
T
and at different angular cones of pseudorapidity and azimuth. The measurement is performed as a function of centrality of the PbPb collisions, the
p
T
asymmetry of the jets in the dijet pair, and the distance parameter R used in the anti-
k
T
jet clustering algorithm. In events with unbalanced dijets, PbPb collisions show an enhanced multiplicity in the hemisphere of the subleading jet, with the
p
T
imbalance compensated by an excess of low-
p
T
particles at large angles from the jet axes.
We report the measurement of γγ → ηc ( 1S ) ,ηc ( 2S ) → η'π+π- with η' decays to γρ and ηπ+π- using 941fb-1 of data collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The ...ηc ( 1S ) mass and width are measured to be M= 2984.6±0.7 ( stat ) ±2.2 ( syst ) ±0.3 ( model ) MeV/c2 and Γ = 30.8-2.2+2.3 ( stat ) ±2.5 ( syst ) ±1.4 ( model ) MeV , respectively. First observation of ηc ( 2S ) → η'π+π- with a significance of 5.5σ including systematic error is obtained, and the ηc ( 2S ) mass is measured to be M= 3635.1±3.7 ( stat ) ±2.9 ( syst ) ±0.4 ( model ) MeV/c2 . The products of the two-photon decay width and branching fraction ( B ) of decays to η'π+π- are determined to be Γ γγ Γ γγ B = 65.4±2.6 ( stat ) ±7.8 ( syst ) eV for ηc ( 1S ) and 5.6-1.1+1.2 ( stat ) ±1.1 ( syst ) eV for ηc ( 2S ) . The cross sections for γγ → η'π+π- and η'f2 ( 1270 ) are measured for the first time.
We report the first observation of the double strange baryon Ξ(1620)^{0} in its decay to Ξ^{-}π^{+} via Ξ_{c}^{+}→Ξ^{-}π^{+}π^{+} decays based on a 980 fb^{-1} data sample collected with the Belle ...detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The mass and width are measured to be 1610.4±6.0(stat)_{-4.2}^{+6.1} (syst) MeV/c^{2} and 59.9±4.8(stat)_{-7.1}^{+2.8}(syst) MeV, respectively. We obtain 4.0σ evidence of the Ξ(1690)^{0} with the same data sample. These results shed light on the structure of hyperon resonances with strangeness S=-2.
The dimuon invariant mass spectrum is searched in the range between 5.5 and 14 GeV for a light pseudoscalar Higgs boson a, predicted in a number of new physics models, including the next-to-minimal ...supersymmetric standard model. The data sample used in the search corresponds to an integrated luminosity of 1.3 fb(-1) collected in pp collisions at √s = 7 TeV with the CMS detector at the LHC. No excess is observed above the background predictions and upper limits are set on the cross section times branching fraction σ × B(pp→a→μ(+)μ(-)) in the range of 1.5-7.5 pb. These results improve on existing bounds on the abb coupling for m(a) < m(Υ(1S)) and are the first significant limits for m(a) > m(Υ(3S)). Constraints on the supersymmetric parameter space are presented in the context of the next-to-minimal model.
A
bstract
Searches for new physics by the CMS collaboration are interpreted in the framework of the phenomenological minimal supersymmetric standard model (pMSSM). The data samples used in this study ...were collected at
s
=
7
and 8 TeV and have integrated luminosities of 5.0 fb
−1
and 19.5 fb
−1
, respectively. A global Bayesian analysis is performed, incorporating results from a broad range of CMS supersymmetry searches, as well as constraints from other experiments. Because the pMSSM incorporates several well-motivated assumptions that reduce the 120 parameters of the MSSM to just 19 parameters defined at the electroweak scale, it is possible to assess the results of the study in a relatively straightforward way. Approximately half of the model points in a potentially accessible subspace of the pMSSM are excluded, including all pMSSM model points with a gluino mass below 500 GeV, as well as models with a squark mass less than 300 GeV. Models with chargino and neutralino masses below 200 GeV are disfavored, but no mass range of model points can be ruled out based on the analyses considered. The nonexcluded regions in the pMSSM parameter space are characterized in terms of physical processes and key observables, and implications for future searches are discussed.
PDF
