Ionization of the diffuse gas in galaxies: Hot low-mass evolved stars at work

We revisit the question of the ionization of the diffuse medium in late type galaxies, by studying NGC 891, the prototype of edge-on spiral galaxies. The most important challenge for the models considered so far was the observed increase of [OIII]/Hbeta, [OII]/Hbeta, and [NII]/Halpha with increasing distance to the galactic plane. We propose a scenario based on the expected population of massive OB stars and hot low-mass evolved stars (HOLMES) in this galaxy to explain this observational fact. In the framework of this scenario we construct a finely meshed grid of photoionization models. For each value of the galactic latitude z we look for the models which simultaneously fit the observed values of the [OIII]/Hbeta, [OII]/Hbeta, and [NII]/Halpha ratios. For each value of z we find a range of solutions which depends on the value of the oxygen abundance. The models which fit the observations indicate a systematic decrease of the electron density with increasing z. They become dominated by the HOLMES with increasing z only when restricting to solar oxygen abundance models, which argues that the metallicity above the galactic plane should be close to solar. They also indicate that N/O increases with increasing z.Comment: Accepted for publication in MNRA

Citrus exocortis viroid and Hop stunt viroid doubly infecting grapevines in Brazil.

Viroids, non-protein-coding small (246-40 I nt) eircular single-stranded RNAs with autonornous replication, are currently classified into two farnilics. Within the farnily Pospiviroidae, Citrus exocortis viroid (CEVd) belongs to lhe genus Pospiviroid while Hop stunt viroid (HSVd) is the single rnembcr of the genus Hostuviroid. These pathogens are distributcd worldwide and infect a large nurnbcr of hosts. In Brazil, isolates of CEVd and HSVd have been detected in both citrus and grapevine. To characterize and study the genetic variability of thcse viroids, total RNA frorn leaves of grapevine Vitis vinifera 'Cabemet Sauvignon' and V Iabrusca 'Niagara Rosada' frorn Bento Gonçalves, RS, was used as a tcmplate for RTPCR amplification with specific primers for lhe five viroids described infccting grapevines [HSVd, CEVd, Grapevine yellow peckle viroid I (GYSVd-I), Grapevine yellow speckle viroid 2 (GYSVd-2) and Australian grapevine viroid (AGVd)]. Leaf sarnples of Citrus medica infected with CEVd frorn São Paulo were also analyzed. The resulting products wcre separated by agarose gel electrophoresis and DNA fragrncnts of lhe expected sizc were eluted, cloned and sequeneed. The grapevine samples analyzed wcre doubly infcctcd by CEVd and HSVd. A phylogcnctic analysis showed that the Brazilian grapevine HSVd variants clustercd with other grapevine HSVd variants, forming a specific group separated from citrus variants, whereas the Brazilian CEVd variants clustered with other citrus and grapevine variants. Additional keywords: CEVd, HSVd, Pospiviroid, Hostuviroid, Pospiviroidae. RESUMO Videiras duplamente infectadas pelo Citrus exocortis viroid e Hop stunt viroid no Brasil Os viróides são os menores fitopatógenos conhecidos, sendo constituídos de uma molécula de RNA fita simples, circular, com forte estrutura secundária. Possuem genomas que variam entre 246 e 40 I nucleotideos e, por não traduzirem proteínas próprias, são totalmente dependentes da célula hospedeira para sua replicação. São classificados em duas famílias e sete gêneros. O Citrus exoconis viroid (CEVd) pertence ao gênero Pospiviroid, enquanto o Hop stunt viroid (HSVd) é o único membro do gênero Hostuviroid, ambos pertencentes à família Pospiviroidae. Estes patógenos apresentam ampla distribuição mundial e infcctam um grande número de hospedeiras. No Brasil, isolados do CEVd e do HSVd foram detectados em citros e videiras. Com o objetivo de caracterizar e estudar a variabilidade genética destes viróides, promoveu-se extração de RNA total de folhas de videira Vitis vinifera 'Cabernet Sauvignon' e V Iabrusca 'Niagara Rosada' provenientes de Bento Gonçalves, RS, e RT-PCR com oligonucleotídeos específicos para os cinco viróides já descritos em videira [HSVd, CEVd, Grapevine yellow speckle viroid I (GYS Vd-I), Crape vine yellow speckle viroid 2 (GYSV d-2) e Australian grapevine viroid (AGVd)). Amostras de folhas de Citrus medica infectadas pelo CEVd provenientes de São Paulo também foram analisadas. Os fragmentos de DNA amplificados foram eluídos, clonados e seqüenciados. As análises das seqüências revelaram que as amostras de videira estavam duplamente infectadas com o CEVd e HSVd. As análises filogenéticas mostraram que os clones de HSVd de videira aqui caracterizados agruparam-se com outros variantes de videira, formando um grupo separado de um segundo formado por variantes de eitros. Já os clones de CEVd de videira agruparam-se com isolados de citros e videira. Palavras-chave adicionais: CEVd, HSVd, Pospiviroid, Hostuviroid, Posp

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

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

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

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 squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using √s=8 TeV proton-proton collision data

A search for squarks and gluinos in final states containing high-p T jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in s√=8 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 20.3 fb−1. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with tan β = 30, A 0 = −2m 0 and μ > 0, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector