572 research outputs found
45S rDNA external transcribed spacer organization reveals new phylogenetic relationships in Avena genus
Research ArticleThe genus Avena comprises four distinct genomes organized in diploid (AA or CC), tetraploid
(AABB or AACC) and hexaploid species (AACCDD), constituting an interesting model
for phylogenetic analysis. The aim of this work was to characterize 45S rDNA intergenic
spacer (IGS) variability in distinct species representative of Avena genome diversityĀ±A.
strigosa (AA), A. ventricosa (CvCv), A. eriantha (CpCp), A. barbata (AABB), A. murphyi
(AACC), A. sativa (AACCDD) and A. sterilis (AACCDD) through the assessment of the 5'
external transcribed spacer (5'-ETS), a promising IGS region for phylogenetic studies poorly
studied in Avena genus. In this work, IGS length polymorphisms were detected mainly due
to distinct 5'-ETS sequence types resulting from major differences in the number and organization
of repeated motifs. Although species with A genome revealed a 5'-ETS organization
(A-organization) similar to the one previously described in A. sativa, a distinct organization
was unraveled in C genome diploid species (C-organization). Interestingly, such new organization
presents a higher similarity with other Poaceae species than A-genome sequences,
supporting the hypothesis of C-genome being the ancestral Avena genome. Additionally,
polyploid species with both genomes mainly retain the A-genome 5'-ETS organization, confirming
the preferential elimination of C-genome sequences in Avena polyploid species.
Moreover, 5'-ETS sequences phylogenetic analysis consistently clustered the species studied
according to ploidy and genomic constitution supporting the use of ribosomal genes to
highlight Avena species evolutive pathways.info:eu-repo/semantics/publishedVersio
Production of Ļ(nS) mesons in Pb + Pb and pp collisions at 5.02 TeV
A measurement of the production of vector bottomonium states, Ļ(1S), Ļ(2S), and Ļ(3S), in Pb + Pb and pp collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb-1 of Pb + Pb data collected in 2018, 0.44 nb-1 of Pb + Pb data collected in 2015, and 0.26 fb-1 of pp data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum pĪ¼Ī¼T < 30 GeV, absolute rapidity |yĪ¼Ī¼| < 1.5, and Pb + Pb event centrality 0-80%. The production rates of the three bottomonium states in Pb + Pb collisions are compared with those in pp collisions to extract the nuclear modification factors as functions of event centrality, pĪ¼Ī¼T, and |yĪ¼Ī¼|. In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations
Search for new phenomena in multi-body invariant masses in events with at least one isolated lepton and two jets using ās = 13 TeV protonāproton collision data collected by the ATLAS detector
A search for resonances in events with at least one isolated lepton (e or Ī¼) and two jets is performed using 139 fb ā1 of s = 13 TeV protonāproton collision data recorded by the ATLAS detector at the LHC. Deviations from a smoothly falling background hypothesis are tested in three- and four-body invariant mass distributions constructed from leptons and jets, including jets identified as originating from bottom quarks. Model-independent limits on generic resonances characterised by cascade decays of particles leading to multiple jets and leptons in the final state are presented. The limits are calculated using Gaussian shapes with different widths for the invariant masses. The multi-body invariant masses are also used to set 95% confidence level upper limits on the cross-section times branching ratios for the production and subsequent decay of resonances predicted by several new physics scenarios. [Figure not available: see fulltext.]
Measurement of the VH,HāÆāāÆĻĻ process with the ATLAS detector at 13 TeV
A measurement of the Standard Model Higgs boson produced in association with a W or Z boson and decaying into a pair of Ļ-leptons is presented. This search is based on proton-proton collision data collected at s=13 TeV by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 140 fbā1. For the Higgs boson candidate, only final states with at least one Ļ-lepton decaying hadronically (Ļāhadrons+Ī½Ļ) are considered. For the vector bosons, only leptonic decay channels are considered: Zāāā and WāāĪ½ā, with ā=e,Ī¼. An excess of events over the expected background is found with an observed (expected) significance of 4.2 (3.6) standard deviations, providing evidence of the Higgs boson produced in association with a vector boson and decaying into a pair of Ļ-leptons. The ratio of the measured cross-section to the Standard Model prediction is Ī¼VHĻĻ=1.28ā0.29+0.30(stat.)ā0.21+0.25(syst.). This result represents the most accurate measurement of the VH(ĻĻ) process achieved to date
Measurement of the total cross section and Ļ -parameter from elastic scattering in pp collisions at ās=13 TeV with the ATLAS detector
In a special run of the LHC with Ī²ā= 2.5 km, protonāproton elastic-scattering events were recorded at s=13 TeV with an integrated luminosity of 340Ī¼b-1 using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from - t= 2.5 Ā· 10 - 4 GeV 2 to - t= 0.46 GeV 2 using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section Ļtot , parameters of the nuclear slope, and the Ļ -parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit tā 0 . These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for Ļtot and Ļ are Ļtot(ppāX)=104.7Ā±1.1mb,Ļ=0.098Ā±0.011. The uncertainty in Ļtot is dominated by the luminosity measurement, and in Ļ by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude
Search for top-philic heavy resonances in pp collisions at s=13Ā TeV with the ATLAS detector
A search for the associated production of a heavy resonance with a top-quark or a top-antitop-quark pair, and decaying into a ttĀÆ pair is presented. The search uses the data recorded by the ATLAS detector in pp collisions at s=13Ā TeV at the Large Hadron Collider during the years 2015ā2018, corresponding to an integrated luminosity of 139Ā fb-1. Events containing exactly one electron or muon are selected. The two hadronically decaying top quarks from the resonance decay are reconstructed using jets clustered with a large radius parameter of R=1. The invariant mass spectrum of the two top quark candidates is used to search for a resonance signal in the range of 1.0Ā TeV to 3.2Ā TeV. The presence of a signal is examined using an approach with minimal model dependence followed by a model-dependent interpretation. No significant excess is observed over the background expectation. Upper limits on the production cross section times branching ratio at 95% confidence level are provided for a heavy Zā² boson based on a simplified model, for Zā² mass between 1.0Ā TeV and 3.0Ā TeV. The observed (expected) limits range from 21Ā (14)Ā fb to 119Ā (86)Ā fb depending on the choice of model parameters
Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of Ļ-leptons in pp collisions at ās = 13 TeV with the ATLAS detector
A search for flavour-changing neutral current (FCNC) tqH interactions involving a top quark, another up-type quark (q = u, c), and a Standard Model (SM) Higgs boson decaying into a Ļ-lepton pair (H ā Ļ + Ļ ā) is presented. The search is based on a dataset of pp collisions at s = 13 TeV that corresponds to an integrated luminosity of 139 fb ā1 recorded with the ATLAS detector at the Large Hadron Collider. Two processes are considered: single top quark FCNC production in association with a Higgs boson (pp ā tH), and top quark pair production in which one of top quarks decays into Wb and the other decays into qH through the FCNC interactions. The search selects events with two hadronically decaying Ļ-lepton candidates (Ļ had) or at least one Ļ had with an additional lepton (e, Ī¼), as well as multiple jets. Event kinematics is used to separate signal from the background through a multivariate discriminant. A slight excess of data is observed with a significance of 2.3Ļ above the expected SM background, and 95% CL upper limits on the t ā qH branching ratios are derived. The observed (expected) 95% CL upper limits set on the t ā cH and t ā uH branching ratios are 9.4Ć10ā4(4.8ā1.4+2.2Ć10ā4) and 6.9Ć10ā4(3.5ā1.0+1.5Ć10ā4) , respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective tqH couplings are CcĻ < 1.35 (0.97) and CuĻ < 1.16 (0.82). [Figure not available: see fulltext.
Search for a CP-odd Higgs boson decaying into a heavy CP-even Higgs boson and a Z boson in the ā+āāttĀÆ and Ī½Ī½ĀÆbbĀÆ final states using 140 fb<sup>ā1</sup> of data collected with the ATLAS detector
A search for a heavy CP-odd Higgs boson, A, decaying into a Z boson and a heavy CP-even Higgs boson, H, is presented. It uses the full LHC Run 2 dataset of pp collisions at s = 13 TeV collected with the ATLAS detector, corresponding to an integrated luminosity of 140 fbā1. The search for A ā ZH is performed in the ā+āāttĀÆ and Ī½Ī½ĀÆbbĀÆ final states and surpasses the reach of previous searches in different final states in the region with mH > 350 GeV and mA > 800 GeV. No significant deviation from the Standard Model expectation is found. Upper limits are placed on the production cross-section times the decay branching ratios. Limits with less model dependence are also presented as functions of the reconstructed m(ttĀÆ) and m(bbĀÆ) distributions in the ā+āāttĀÆ and Ī½Ī½ĀÆbbĀÆ channels, respectively. In addition, the results are interpreted in the context of two-Higgs-doublet models
Differential ttĀÆcross-section measurements using boosted top quarks in the all-hadronic final state with 139 fbā1 of ATLAS data
Measurements of single-, double-, and triple-differential cross-sections are presented for boosted top-quark pair-production in 13 TeV protonāproton collisions recorded by the ATLAS detector at the LHC. The top quarks are observed through their hadronic decay and reconstructed as large-radius jets with the leading jet having transverse momentum (pT) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the ttĀÆ ā WWbbĀÆ branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have pT> 500 GeV and pT> 350 GeV, respectively, is 331 Ā± 3(stat.) Ā± 39(syst.) fb. This is approximately 20% lower than the prediction of 398ā49+48 fb by Powheg+Pythia 8 with next-to-leading-order (NLO) accuracy but consistent within the theoretical uncertainties. Results are also presented at the parton level, where the effects of top-quark decay, parton showering, and hadronization are removed such that they can be compared with fixed-order next-to-next-to-leading-order (NNLO) calculations. The parton-level cross-section, measured in a fiducial phase space similar to that at particle level, is 1.94 Ā± 0.02(stat.) Ā± 0.25(syst.) pb. This agrees with the NNLO prediction of 1.96ā0.17+0.02 pb. Reasonable agreement with the differential cross-sections is found for most NLO models, while the NNLO calculations are generally in better agreement with the data. The differential cross-sections are interpreted using a Standard Model effective field-theory formalism and limits are set on Wilson coefficients of several four-fermion operators. [Figure not available: see fulltext.]
Measurement of the Higgs boson mass in the H ā Z Zā ā 4 decay channel using 139 fbā1 of ās = 13 TeV pp collisions recorded by the ATLAS detector at the LHC
The mass of the Higgs boson is measured in the HāZZāā4ā decay channel. The analysis uses protonāproton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector between 2015 and 2018, corresponding to an integrated luminosity of 139 fbā1. The measured value of the Higgs boson mass is 124.99Ā±0.18(stat.)Ā±0.04(syst.) GeV. In final states with muons, this measurement benefits from an improved momentum-scale calibration relative to that adopted in previous publications. The measurement also employs an analytic model that takes into account the invariant-mass resolution of the four-lepton system on a per-event basis and the output of a deep neural network discriminating signal from background events. This measurement is combined with the corresponding measurement using 7 and 8 TeV pp collision data, resulting in a Higgs boson mass of 124.94Ā±0.17(stat.)Ā±0.03(syst.) GeV
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