Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in pp collisions at √ s = 13 TeV with the ATLAS detectorThe ATLAS Collaboration A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton-proton collisions at √ s = 13 TeV is presented. This search uses 36.1 fb −1 of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67% (39%) at the 95% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass m H = 125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models.The ATLAS detector [46,47] is a large multi-purpose apparatus with a forward-backward symmetric cylindrical geometry 1 and nearly 4π coverage in solid angle. The collision point is encompassed by an inner tracking detector (ID) surrounded by a 2 T superconducting solenoid, electromagnetic (EM) and hadronic calorimeters, and a muon spectrometer (MS) with a toroidal magnetic field. The ID provides tracking for charged particles for |η| < 2.5. It consists of silicon pixel and strip detectors surrounded by a straw tube tracker that also provides transition radiation measurements for electron identification. The EM and hadronic calorimeter system covers the pseudorapidity range |η| < 4.9. For |η| < 2.5, the liquid-argon EM calorimeter is finely segmented and plays an important role in electron and photon identification. The MS includes fast trigger chambers (|η| < 2.4) and high-precision tracking chambers covering |η| < 2.7. A two-level trigger system selects events to be recorded for offline physics analysis [48]. Data and simulationThis search utilises data collected with single-lepton triggers by the ATLAS detector during the 2015 and 2016 data-taking periods. A combination of a lower p T threshold trigger with an isolation requirement and a higher p T threshold trigger without any isolation requirement is used. The p T threshold of the isolated electron (muon) trigger ranges from 24 (20) to 26 GeV depending on the instantaneous luminosity. The higher p T threshold is 50 (60) GeV for the electron (muon) case over all the data-taking periods. The overall trigger efficiency is above 98% for the BSM signal processes after the full event selection described in Section 4.To study the invisible Higgs boson decays, Monte Carlo events are produced for the SM ZH process with a subsequent Z boson decay into a dilepton pair and the H → ZZ → νννν decay (ZH → + inv). The ZH signal processes from both the quark-antiquark (qqZH) and gluon-gluon (ggZH) initial 1 ATLAS uses a...
The number of J/ψ events collected with the BES detector at the BEPC from June 12 to July 28, 2009 is determined to be (225.3±2.8)×10 6 using J/ψ →inclusive events, where the uncertainty is the systematic error and the statistical one is negligible.
Protein secondary structure prediction is one of the most important and challenging problems in bioinformatics. Machine learning techniques have been applied to solve the problem and have gained substantial success in this research area. However there is still room for improvement toward the theoretical limit. In this paper, we present a novel method for protein secondary structure prediction based on a data partition and semi-random subspace method (PSRSM). Data partitioning is an important strategy for our method. First, the protein training dataset was partitioned into several subsets based on the length of the protein sequence. Then we trained base classifiers on the subspace data generated by the semi-random subspace method, and combined base classifiers by majority vote rule into ensemble classifiers on each subset. Multiple classifiers were trained on different subsets. These different classifiers were used to predict the secondary structures of different proteins according to the protein sequence length. Experiments are performed on 25PDB, CB513, CASP10, CASP11, CASP12, and T100 datasets, and the good performance of 86.38%, 84.53%, 85.51%, 85.89%, 85.55%, and 85.09% is achieved respectively. Experimental results showed that our method outperforms other state-of-the-art methods.
The ATLAS CollaborationSearches for scalar leptoquarks pair-produced in proton-proton collisions at √ s = 13 TeV at the Large Hadron Collider are performed by the ATLAS experiment. A data set corresponding to an integrated luminosity of 36.1 fb −1 is used. Final states containing two electrons or two muons and two or more jets are studied, as are states with one electron or muon, missing transverse momentum and two or more jets. No statistically significant excess above the Standard Model expectation is observed. The observed and expected lower limits on the leptoquark mass at 95% confidence level extend up to 1.29 TeV and 1.23 TeV for first-and second-generation leptoquarks, respectively, as postulated in the minimal Buchmüller-Rückl-Wyler model, assuming a branching ratio into a charged lepton and a quark of 50%. In addition, measurements of particle-level fiducial and differential cross sections are presented for the Z → ee, Z → µµ and tt processes in several regions related to the search control regions. Predictions from a range of generators are compared with the measurements, and good agreement is seen for many of the observables. However, the predictions for the Z → measurements in observables sensitive to jet energies disagree with the data.Electrons are reconstructed from ID tracks which are matched to energy clusters found in the electromagnetic calorimeter. The reconstruction efficiency is higher than 97% for candidates with p T greater than 30 GeV. An object is identified as an electron following requirements made on the quality of the associated track, shower shapes exploiting the longitudinal segmentation of the electromagnetic calorimeter, leakage into the hadronic calorimeter, the quality of the track-to-cluster matching and measurements of transition radiation made with the TRT [71]. The transverse energy of the electron candidates in the ee j j (eν j j) channel must exceed 40 (65) GeV. Only electron candidates in the pseudorapidity region |η| < 2.47 and excluding
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