A catalog of warps in spiral and lenticular galaxies in the Southern hemisphere

A catalog of optical warps of galaxies is presented. This can be considered complementary to that reported by Sanchez-Saavedra et al., with 42 galaxies in the northern hemisphere, and to that by Reshetnikov & Combes, with 60 optical warps. The limits of the present catalog are: logr25 > 0.60, B_{t} < 14.5, delta(2000) < 0, -2.5 < t < 7. Therefore, lenticular galaxies have also been considered. This catalog lists 150 warped galaxies out of a sample of 276 edge-on galaxies and covers the whole southern hemisphere, except the Avoidance Zone. It is therefore very suitable for statistical studies of warps. It also provides a source guide for detailed particular observations. We confirm the large frequency of warped spirals: nearly all galaxies are warped. The frequency and warp angle do not present important differences for the different types of spirals. However, no lenticular warped galaxy has been found within the specified limits. This finding constitutes an important restriction for theoretical models.Comment: 12 pages, 6 figures, to be published in Astronomy and Astrophysic

Old stellar Galactic disc in near-plane regions according to 2MASS: scales, cut-off, flare and warp

We have pursued two different methods to analyze the old stellar population near the Galactic plane, using data from the 2MASS survey. The first method is based on the isolation of the red clump giant population in the color-magnitude diagrams and the inversion of its star counts to obtain directly the density distribution along the line of sight. The second method fits the parameters of a disc model to the star counts in 820 regions. Results from both independent methods are consistent with each other. The qualitative conclusions are that the disc is well fitted by an exponential distribution in both the galactocentric distance and height. There is not an abrupt cut-off in the stellar disc (at least within R<15 kpc). There is a strong flare (i.e. an increase of scale-height towards the outer Galaxy) which begins well inside the solar circle, and hence there is a decrease of the scale-height towards the inner Galaxy. Another notable feature is the existence of a warp in the old stellar population whose amplitude is coincident with the amplitude of the gas warp. It is shown for low latitude stars (mean height: |z|~300 pc) in the outer disc (galactocentric radius R>6 kpc) that: the scale-height in the solar circle is h_z(R_sun)=3.6e-2 R_sun, the scale-length of the surface density is h_R=0.42 R_sun and the scale-length of the space density in the plane (i.e. including the effect of the flare) is H=0.25 R_sun. The variation of the scale-height due to the flare follows roughly a law h_z(R) =~ h_z(R_sun) exp [(R-R_\odot)/([12-0.6R(kpc)] kpc)] (for R<~15 kpc; R_sun=7.9 kpc). The warp moves the mean position of the disc to a height z_w=1.2e-3 R(kpc)^5.25 sin(phi+(5 deg.)) pc (for R<~13 kpc; R_sun=7.9 kpc).Comment: LaTEX, 20 pages, 23 figures, accepted to be published in A&

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

AGENTES ASOCIADOS Y SU PAPEL EN LA DECLINACIÓN Y MUERTE DE ENCINOS (QUERCUS, FAGACEAE) EN EL CENTRO-OESTE DE MÉXICO

This study was carried out to identify bioticand abiotic agents and to determine theirrole in oak decline and death in five statesof the Mexican Republic: Aguascalientes,Colima, Guanajuato, Jalisco and Nayarit.Two 0.1-ha permanent plots wereestablished at the most representativeforested areas with tree death, diebackand bleeding cankers in these statesand sampled during 2003, 2004 and 2005(10 plots in total). Field observations weremade, and foliage, branch, trunk and soilsamples were collected to identify theassociated agents in each plot. Isolates frombleeding cankers were made in situ. Themost commonly found biotic agents were:Phytophthora cinnamomi, Pythium sp.,Hypoxylon antropunctatum, Ganodermaspp., Armillaria sp., Apiognomoniaquercina, the dwarf mistletoe(Phoradendron villosum), bark borers,insect defoliators and livestock overgrazing.Among the abiotic stress factors commonlyfound were the effects due to lowtemperature-lack of water and fire. Basedon their incidence, P. cinnamomi, H.antropunctatum and low temperature-lackof water were considered the most importantcontributors to the decline and death of theoaks. P. cinnamomi was identified in four ofthe 10 plots, mainly in Colima and Jalisco;H. antropunctatum was detected in sixplots, particularly in Nayarit andAguascalientes. Stem cankers (cracks) dueto low temperature-lack of water wereobserved in four plots, damaging 52% of the trees in Aguascalientes and 24% inGuanajuato. It was concluded that P.cinnamomi is killing some oak species, H.antropunctatum is colonizing weakenedtrees, and low temperature-lack of water iscausing stress and in some cases death inoaks.Este estudio tuvo como objetivo identificary determinar el papel tanto de los factoresbióticos como de los abióticos asociados ala declinación y muerte del encino en cincoestados de la República mexicana: Aguascalientes, Colima, Guanajuato, Jalisco yNayarit. Para esto, se establecieron dossitios permanentes de 0.1 ha en cada una delas áreas más representativas (con arboladomuerto, con muerte regresiva y cancros conexudado) de los estados mencionados (10sitios en total), los cuales fueron muestreados durante 2003, 2004 y 2005. Sehicieron observaciones y colectas en campode follaje, ramas, tronco y suelo, paraidentificar a los diferentes agentes de dañoen cada sitio. Se realizaron aislamientosin situ de cancros con exudado en mediosespecíficos. Los agentes bióticos máscomunes fueron: Phytophthora cinnamomi,Pythium sp., Hypoxylon antropunctatum,Ganoderma sp., Armillaria sp.,Apiognomonia quercina, el muérdagoenano (Phoradendron villosum), barrenadores, defoliadores y sobrepastoreo. Entre los abióticos causantes de estrés ymuerte, destacaron los daños ocasionadospor las bajas temperaturas-falta de aguay fuego. Con base en su incidencia, P.cinnamomi, H. antropunctatum y las bajastemperaturas-falta de agua son considerados los factores de mayor importanciaen la declinación y muerte del encino. P.cinnamomi fue identificado en cuatro delos diez sitios, particularmente de Colimay Jalisco; H. antropunctatum fué detectadoen seis de diez, principalmente en losrodales de Nayarit y Aguascalientes. Loscancros de troncos (rajaduras), debido a lasbajas temperaturas-falta de agua, seobservaron en cuatro sitios, afectando al52% de los árboles en Aguascalientes y24% en Guanajuato. Se concluye que P.cinnamomi está ocasionando la muertede algunas especies de encino, H.antropunctatum está coloni-zando árbolesdebilitados y las bajas temperaturas-faltade agua están participando como agentescausantes de estrés y muerte en algunoscasos

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30

Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations

Search for anomalous t t-bar production in the highly-boosted all-hadronic final state

A search is presented for a massive particle, generically referred to as a Z', decaying into a t t-bar pair. The search focuses on Z' resonances that are sufficiently massive to produce highly Lorentz-boosted top quarks, which yield collimated decay products that are partially or fully merged into single jets. The analysis uses new methods to analyze jet substructure, providing suppression of the non-top multijet backgrounds. The analysis is based on a data sample of proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 5 inverse femtobarns. Upper limits in the range of 1 pb are set on the product of the production cross section and branching fraction for a topcolor Z' modeled for several widths, as well as for a Randall--Sundrum Kaluza--Klein gluon. In addition, the results constrain any enhancement in t t-bar production beyond expectations of the standard model for t t-bar invariant masses larger than 1 TeV.Comment: Submitted to the Journal of High Energy Physics; this version includes a minor typo correction that will be submitted as an erratu

Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector

Results of a search for H → τ τ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ → `νν¯ with ` = e, µ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of µ = 1.43 +0.43 −0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model

Measurement of χ c1 and χ c2 production with s√ = 7 TeV pp collisions at ATLAS

The prompt and non-prompt production cross-sections for the χ c1 and χ c2 charmonium states are measured in pp collisions at s√ = 7 TeV with the ATLAS detector at the LHC using 4.5 fb−1 of integrated luminosity. The χ c states are reconstructed through the radiative decay χ c → J/ψγ (with J/ψ → μ + μ −) where photons are reconstructed from γ → e + e − conversions. The production rate of the χ c2 state relative to the χ c1 state is measured for prompt and non-prompt χ c as a function of J/ψ transverse momentum. The prompt χ c cross-sections are combined with existing measurements of prompt J/ψ production to derive the fraction of prompt J/ψ produced in feed-down from χ c decays. The fractions of χ c1 and χ c2 produced in b-hadron decays are also measured