A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated luminosity of 36.1 fb−1 o...
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A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated luminosity of 36.1 fb−1 of proton-proton collisions at the LHC at a center-of-mass energy of 13 TeV in 2015 and 2016. No significant excess over the expected background is observed. Upper limits at 95% confidence level are set on the visible cross section for beyond the Standard Model physics processes, and the production cross section times branching fraction of the Standard Model Higgs boson decaying into two photons in association with missing transverse momentum in three different benchmark models. Limits at 95% confidence level are also set on the observed signal in two-dimensional mass planes. Additionally, the results are interpreted in terms of 90% confidence-level limits on the dark-matter–nucleon scattering cross section, as a function of the dark-matter particle mass, for a spin-independent scenario.
The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a center-of-mass energy of s...
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The results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a center-of-mass energy of s=13 TeV are presented. The data set used was recorded during 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb−1. No significant excess beyond the expected background is found. Exclusion limits at 95% confidence level are set in a number of supersymmetric scenarios, reaching masses up to 2.1 TeV for gluino pair production and up to 1.25 TeV for squark pair production.
Dijet events are studied in the proton-proton collision data set recorded at s=13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated luminosities of 3.5 fb−1 and 3...
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Dijet events are studied in the proton-proton collision data set recorded at s=13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated luminosities of 3.5 fb−1 and 33.5 fb−1 respectively. Invariant mass and angular distributions are compared to background predictions and no significant deviation is observed. For resonance searches, a new method for fitting the background component of the invariant mass distribution is employed. The data set is then used to set upper limits at a 95% confidence level on a range of new physics scenarios. Excited quarks with masses below 6.0 TeV are excluded, and limits are set on quantum black holes, heavy W′ bosons, W* bosons, and a range of masses and couplings in a Z′ dark matter mediator model. Model-independent limits on signals with a Gaussian shape are also set, using a new approach allowing factorization of physics and detector effects. From the angular distributions, a scale of new physics in contact interaction models is excluded for scenarios with either constructive or destructive interference. These results represent a substantial improvement over those obtained previously with lower integrated luminosity.
The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model...
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The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of 190 μb−1 of minimum-bias events collected with proton-proton collisions at a center-of-mass energy s=7 TeV in the early low-luminosity data taking with the ATLAS detector at the LHC.
A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to 20.2 fb−1 of s=8 TeV pp collisions and were collected in 2012 by the ATLAS experi...
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A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to 20.2 fb−1 of s=8 TeV pp collisions and were collected in 2012 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of WW or WZ boson pairs accompanied by a high-mass dijet system, with one W decaying leptonically and a W or Z decaying hadronically. The hadronically decaying W/Z is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters α4 and α5 are set by fitting the transverse mass of the diboson system, and the resulting 95% confidence intervals are −0.024<α4<0.030 and −0.028<α5<0.033.
This paper presents the extended results of measurements of W±W±jj production and limits on anomalous quartic gauge couplings using 20.3 fb−1 of proton–proton collision data at s=8 TeV recorded by the ATL...
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This paper presents the extended results of measurements of W±W±jj production and limits on anomalous quartic gauge couplings using 20.3 fb−1 of proton–proton collision data at s=8 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two leptons (e or μ) with the same electric charge and at least two jets are analyzed. Production cross sections are determined in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. An additional fiducial region, particularly sensitive to anomalous quartic gauge coupling parameters α4 and α5, is introduced, which allows more stringent limits on these parameters compared to the previous ATLAS measurement.
A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of s=8 TeV is presented. The results are based on an integrated luminosity of 20.2 fb−1 r...
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A measurement of the production cross section for two isolated photons in proton-proton collisions at a center-of-mass energy of s=8 TeV is presented. The results are based on an integrated luminosity of 20.2 fb−1 recorded by the ATLAS detector at the Large Hadron Collider. The measurement considers photons with pseudorapidities satisfying |ηγ|<1.37 or 1.56<|ηγ|<2.37 and transverse energies of respectively ET,1γ>40 GeV and ET,2γ>30 GeV for the two leading photons ordered in transverse energy produced in the interaction. The background due to hadronic jets and electrons is subtracted using data-driven techniques. The fiducial cross sections are corrected for detector effects and measured differentially as a function of six kinematic observables. The measured cross section integrated within the fiducial volume is 16.8±0.8 pb. The data are compared to fixed-order QCD calculations at next-to-leading-order and next-to-next-to-leading-order accuracy as well as next-to-leading-order computations including resummation of initial-state gluon radiation at next-to-next-to-leading logarithm or matched to a parton shower, with relative uncertainties varying from 5% to 20%.
In bilateral teleoperation systems, beside the haptic feedback, the human operator also needs video information about the motion of the distantly controlled robot to complete the teleoperation task. In this study a so...
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In bilateral teleoperation systems, beside the haptic feedback, the human operator also needs video information about the motion of the distantly controlled robot to complete the teleoperation task. In this study a software design approach is presented for such bilateral teleoperation systems that include one or more video channels. A control algorithm is also presented that regulates the traffic in the video channels in order to assure good communication properties for the communication channels over which the control signals are interchanged by the master and slave side of the teleoperation system. Solutions are also given for the implementation of such teleoperation systems. Experimental measurements are presented to validate the proposed communication and software design approach.
The development of niching methods is a very active research area within multimodal optimization. It includes not only the creation of new methods, but the formalization of hybrid methodologies resulting from the appl...
The development of niching methods is a very active research area within multimodal optimization. It includes not only the creation of new methods, but the formalization of hybrid methodologies resulting from the application of basic niching techniques to global optimization metaheuristics. In this paper, we discuss some preliminary results of a recently proposed metaheuristic algorithm, Variable Mesh Optimization (VMO), in the context of multimodal problems. To overcome some of the encountered limitations, a revamped version called Niche-Clearing-based Variable Mesh Optimization (NC-VMO) is put forth. NC-VMO demonstrated its ability to optimize multimodal functions by using a niche clearing technique. Experimental results confirm that the proposed approach is also competitive with other niche-based optimization methods in the literature.
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