Imagens multiespectrais para avaliação de índice de área foliar e massa seca do capim 'Tifton 85', sob adubação nitrogenada

O presente trabalho teve por objetivo analisar as respostas do capim 'Tifton 85' (Cynodon spp.) à adubação nitrogenada, em termos de área foliar verde e de massa seca da parte aérea, utilizando índices calculados a partir de informações contidas em imagens multiespectrais, em comparação com indicadores obtidos por métodos diretos. Os tratamentos consistiram de quatro doses de N-ureia (0; 100; 150 e 200 kg ha-1), dispostos em um desenho experimental inteiramente casualizado, com quatro repetições. Aos 26 dias, após um corte de uniformização, foram determinados os seguintes atributos do dossel: o Índice de Área Foliar (IAF), a massa seca da parte aérea (MSPA), o índice de cobertura verde (ICV), utilizando uma câmara digital na faixa do visível e o Índice de Vegetação por Diferença Normalizada (NDVI), utilizando uma câmara multiespectral. Os quatro atributos do dossel vegetativo responderam positivamente à adubação nitrogenada. Enquanto o ICV mostrou relações curvilineares com o IAF e a MSPA (R² IAF=0,89; R² MSPA=0,87), o NDVI mostrou relações lineares (r² IAF=0,62; r2 MSPA=0,64), sem evidenciar tendência à saturação. Foi concluído que é possível avaliar a adubação nitrogenada em pastagens de Cynodon spp., utilizando análise de imagens, e que tanto o NDVI quanto o ICV podem ser utilizados como indicadores de produtividade do capim Tifton 8

Charged-hadron and identified-hadron (K0 S, , −) yield measurements in photonuclear Pb+Pband p+Pbcollisions at √ sNN = 5.02TeV with ATLAS

This paper presents the measurement of charged-hadron and identified-hadron (K0 S, , −) yields in photonuclear collisions using 1.7nb−1 of √ sNN = 5.02TeV Pb+Pb data collected in 2018 with the ATLAS detector at the Large Hadron Collider. Candidate photonuclear events are selected using a combination of tracking and calorimeter information, including the zero-degree calorimeter. The yields as a function of transverse momentum and rapidity are measured in these photonuclear collisions as a function of charged-particle multiplicity. These photonuclear results are compared with 0.1nb−1 of √ sNN = 5.02TeV p+Pbdata collected in 2016 by ATLAS using similar charged-particle multiplicity selections. These photonuclear measurements shed light on potential quark-gluon plasma formation in photonuclear collisions via observables sensitive to radial flow, enhanced baryon-to-meson ratios, and strangeness enhancement. The results are also compared with the Monte Carlo DPMJET-III generator and hydrodynamic calculations to test whether such photonuclear collisions may produce small droplets of quark-gluon plasma that flow collectively

Observation of quantum entanglement with top quarks at the ATLAS detector

Entanglement is a key feature of quantum mechanics with applications in fields such as metrology, cryptography, quantum information and quantum computation. It has been observed in a wide variety of systems and length scales, ranging from the microscopic to the macroscopic. However, entanglement remains largely unexplored at the highest accessible energy scales. Here we report the highest-energy observation of entanglement, in top–antitop quark events produced at the Large Hadron Collider, using a proton–proton collision dataset with a centre-of-mass energy of √s = 13 TeV and an integrated luminosity of 140 inverse femtobarns (fb)−1 recorded with the ATLAS experiment. Spin entanglement is detected from the measurement of a single observable D, inferred from the angle between the charged leptons in their parent top- and antitop-quark rest frames. The observable is measured in a narrow interval around the top–antitop quark production threshold, at which the entanglement detection is expected to be significant. It is reported in a fiducial phase space defined with stable particles to minimize the uncertainties that stem from the limitations of the Monte Carlo event generators and the parton shower model in modelling top-quark pair production. The entanglement marker is measured to be D = −0.537 ± 0.002 (stat.) ± 0.019 (syst.) for 340 GeV < mtt < 380 GeV. The observed result is more than five standard deviations from a scenario without entanglement and hence constitutes the first observation of entanglement in a pair of quarks and the highest-energy observation of entanglement so far

The performance of missing transverse momentum reconstruction and its significance with the ATLAS detector using 140 fb-1 of √s = 13 TeV TeV pp collisions

Abstract This paper presents the reconstruction of missing transverse momentum ( $$p_{\text {T}}^{\text {miss}}$$ p T miss ) in proton–proton collisions, at a center-of-mass energy of 13 TeV. This is a challenging task involving many detector inputs, combining fully calibrated electrons, muons, photons, hadronically decaying $$\tau$$ τ -leptons, hadronic jets, and soft activity from remaining tracks. Possible double counting of momentum is avoided by applying a signal ambiguity resolution procedure which rejects detector inputs that have already been used. Several $$p_{\text {T}}^{\text {miss}}$$ p T miss ‘working points’ are defined with varying stringency of selections, the tightest improving the resolution at high pile-up by up to 39% compared to the loosest. The $$p_{\text {T}}^{\text {miss}}$$ p T miss performance is evaluated using data and Monte Carlo simulation, with an emphasis on understanding the impact of pile-up, primarily using events consistent with leptonic Z decays. The studies use $$140~\text {fb}^{-1}$$ 140 fb - 1 of data, collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. The results demonstrate that $$p_{\text {T}}^{\text {miss}}$$ p T miss reconstruction, and its associated significance, are well understood and reliably modelled by simulation. Finally, the systematic uncertainties on the soft $$p_{\text {T}}^{\text {miss}}$$ p T miss component are calculated. After various improvements the scale and resolution uncertainties are reduced by up to $$76\%$$ 76 % and $$51\%$$ 51 % , respectively, compared to the previous calculation at a lower luminosity

Deep generative models for fast photon shower simulation in ATLAS

The need for large-scale production of highly accurate simulated event samples for the extensive physics programme of the ATLAS experiment at the Large Hadron Collider motivates the development of new simulation techniques. Building on the recent success of deep learning algorithms, variational autoencoders and generative adversarial networks are investigated for modelling the response of the central region of the ATLAS electromagnetic calorimeter to photons of various energies. The properties of synthesised showers are compared with showers from a full detector simulation using geant4. Both variational autoencoders and generative adversarial networks are capable of quickly simulating electromagnetic showers with correct total energies and stochasticity, though the modelling of some shower shape distributions requires more refinement. This feasibility study demonstrates the potential of using such algorithms for ATLAS fast calorimeter simulation in the future and shows a possible way to complement current simulation techniques

Search for heavy Majorana or Dirac neutrinos and right-handed W gauge bosons in final states with charged leptons and jets in pp collisions at √s = 13 TeV with the ATLAS detector

A search for heavy right-handed Majorana or Dirac neutrinos NR and heavy right-handed gauge bosons WR is performed in events with energetic electrons or muons, with the same or opposite electric charge, and energetic jets. The search is carried out separately for topologies of clearly separated final-state products (“resolved” channel) and topologies with boosted final states with hadronic and/or leptonic products partially overlapping and reconstructed as a large-radius jet (“boosted” channel). The events are selected from pp collision data at the LHC with an integrated luminosity of 139 fb−1 collected by the ATLAS detector at √s = 13 TeV. No significant deviations from the Standard Model predictions are observed. The results are interpreted within the theoretical framework of a left-right symmetric model, and lower limits are set on masses in the heavy righthanded WR boson and NR plane. The excluded region extends to about m(WR) = 6.4 TeV for both Majorana and Dirac NR neutrinos at m(NR) < 1 TeV. NR with masses of less than 3.5 (3.6) TeV are excluded in the electron (muon) channel at m(WR) = 4.8 TeV for the Majorana neutrinos, and limits of m(NR) up to 3.6 TeV for m(WR) = 5.2 (5.0) TeV in the electron (muon) channel are set for the Dirac neutrinos. These constitute the most stringent exclusion limits to date for the model considered