1,096 research outputs found

    Interpretations of SUSY Searches in ATLAS with Simplified Models

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    We present the status of interpretations of Supersymmetry (SUSY) searches in ATLAS at the Large Hadron Collider (LHC) using simplified models. Such models allow a systematic scan through the phase space in the sparticle mass plane, and in the corresponding final state kinematics. Models at various levels of simplification have been studied in ATLAS. The results can be extrapolated to more general new physics models which lead to the same event topology with similar mass hierarchies. Searches in the no-lepton channel with 1.04 fb^-1 of data from 2011 and the same-sign dilepton channel with 35 pb^-1 of data from 2010 are presented. No excess above the Standard Model expectation is observed, and the results are interpreted using the simplified models.Comment: 9 pages, 7 figures, 3 tables, for the proceedings of the DPF-2011 conference, Providence, RI, August 9-13, 201

    Effect of biopsy on survival of melanoma patients

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    Background Cutaneous malignant melanoma has a poor prognosis. The detrimental effect of incisional biopsies on the outcome of malignant melanoma has been debated. The aim of this study was to determine the effect of the presence and type of biopsy on the prognosis of malignant melanoma. Methods The medical records of 109 malignant melanoma patients treated at Tokushima University Hospital from 1983 to 2007 were reviewed. After excluding 28 cases with stage 0 disease or incomplete data, 81 cases were analyzed in detail with respect to patient sex, age, tumor site, clinical stage at diagnosis, presence of ulceration or lymph node metastasis, and prognosis. The five-year survival and five-year disease-free survival rates of patients who underwent incisional or excisional biopsies were compared with those who did not undergo a biopsy. Results The male-to-female ratio was 1:1.19. The mean age was 61.3 years (range, 19–93 years). The most common site was a lower extremity, and the most common clinical stage was stage II. No significant differences in clinicopathological features, five-year survival rates, and five-year disease-free survival rates were observed among the three groups. Conclusions The presence and type of biopsy neither affected the metastatic rate nor the prognosis of malignant melanoma. The use of incisional biopsies is not encouraged because tumor thickness cannot be measured accurately. However, they may be helpful for confirming the diagnosis if an excisional biopsy cannot be performed

    Extended Symmetry Preserving Attention Networks for LHC Analysis

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    Reconstructing unstable heavy particles requires sophisticated techniques to sift through the large number of possible permutations for assignment of detector objects to partons. An approach based on a generalized attention mechanism, symmetry preserving attention networks (SPANet), has been previously applied to top quark pair decays at the Large Hadron Collider, which produce six hadronic jets. Here we extend the SPANet architecture to consider multiple input streams, such as leptons, as well as global event features, such as the missing transverse momentum. In addition, we provide regression and classification outputs to supplement the parton assignment. We explore the performance of the extended capability of SPANet in the context of semi-leptonic decays of top quark pairs as well as top quark pairs produced in association with a Higgs boson. We find significant improvements in the power of three representative studies: search for ttH, measurement of the top quark mass and a search for a heavy Z' decaying to top quark pairs. We present ablation studies to provide insight on what the network has learned in each case

    Guided parent-delivered cognitive behavioural therapy for Japanese children and parents: a single-arm uncontrolled study

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    Background: Guided parent-delivered cognitive behavioural therapy (GPD-CBT) is an effective low-intensity treatment for childhood anxiety disorder in Western countries and can increase access to evidence-based psychological therapies. Aim: This study aimed to examine its feasibility in a Japanese sample. Method: Twelve children with anxiety disorders and their parents participated in the study, and ten children and parents completed the program. Participants were assessed at pre-, post- and one-month follow-up using a diagnostic interview for anxiety disorders, self- and parent-report measures for anxiety, depression, parental behaviour, and parental anxiety. Results: Four children (40% of completers) were free from their primary diagnoses immediately following the brief treatment, and seven children (70%) at the one-month follow-up. Changes in disorder severity, child and parent reported anxiety symptoms, and child reported depression symptoms were consistent with those found in Western trials of GPD-CBT and of Japanese trials of more intensive CBT for child anxiety disorders that involves both the child and the parent. Moderate increases were also found in child reported parental autonomy behaviours; however, there were only small changes in parent self-reported anxiety. Conclusion: These results support the potential of GPD-CBT to increase access to evidence-based treatments for anxiety disorders in Japanese children

    Prompt and non-prompt J/ψ elliptic flow in Pb+Pb collisions at √sNN=5.02 Tev with the ATLAS detector

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    The elliptic flow of prompt and non-prompt J/ψ was measured in the dimuon decay channel in Pb+Pb collisions at sNN−−−√=5.02 TeV with an integrated luminosity of 0.42 nb−1 with the ATLAS detector at the LHC. The prompt and non-prompt signals are separated using a two-dimensional simultaneous fit of the invariant mass and pseudo-proper decay time of the dimuon system from the J/ψ decay. The measurement is performed in the kinematic range of dimuon transverse momentum and rapidity 9<pT<30 GeV, |y|<2, and 0–60% collision centrality. The elliptic flow coefficient, v2, is evaluated relative to the event plane and the results are presented as a function of transverse momentum, rapidity and centrality. It is found that prompt and non-prompt J/ψ mesons have non-zero elliptic flow. Prompt J/ψ v2 decreases as a function of pT, while for non-prompt J/ψ it is, with limited statistical significance, consistent with a flat behaviour over the studied kinematic region. There is no observed dependence on rapidity or centrality

    Search for pairs of highly collimated photon-jets in pp collisions at root s=13 TeV with the ATLAS detector

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    Results of a search for the pair production of photon-jets—collimated groupings of photons—in the ATLAS detector at the Large Hadron Collider are reported. Highly collimated photon-jets can arise from the decay of new, highly boosted particles that can decay to multiple photons collimated enough to be identified in the electromagnetic calorimeter as a single, photonlike energy cluster. Data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.7  fb−1, were collected in 2015 and 2016. Candidate photon-jet pair production events are selected from those containing two reconstructed photons using a set of identification criteria much less stringent than that typically used for the selection of photons, with additional criteria applied to provide improved sensitivity to photon-jets. Narrow excesses in the reconstructed diphoton mass spectra are searched for. The observed mass spectra are consistent with the Standard Model background expectation. The results are interpreted in the context of a model containing a new, high-mass scalar particle with narrow width, X, that decays into pairs of photon-jets via new, light particles, a. Upper limits are placed on the cross section times the product of branching ratios σ×B(X→aa)×B(a→γγ)2 for 200  GeV<mX<2  TeV and for ranges of ma from a lower mass of 100 MeV up to between 2 and 10 GeV, depending upon mX. Upper limits are also placed on σ×B(X→aa)×B(a→3π0)2 for the same range of mX and for ranges of ma from a lower mass of 500 MeV up to between 2 and 10 GeV

    Search for top-quark decays t → Hq with 36 fb−1 of pp collision data at √ s= 13 TeV with the ATLAS detector

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    A search for flavour-changing neutral current decays of a top quark into an up-type quark (q = u, c) and the Standard Model Higgs boson, t → Hq, is presented. The search is based on a dataset of pp collisions at s√ = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb−1. Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target the H→bb¯¯ and H → τ+τ− decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are used to separate the signal from the background, which is dominated by top-quark pair production. No significant excess of events above the background expectation is found, and 95% CL upper limits on the t → Hq branching ratios are derived. The combination of these searches with ATLAS searches in diphoton and multilepton final states yields observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 1.1 × 10−3 (8.3 × 10−4) and 1.2 × 10−3 (8.3 × 10−4), respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.064 (0.055) and 0.066 (0.055), respectively

    Search for heavy particles decaying into a top-quark pair in the fully hadronic final state in pp collisions at √s=13  TeV with the ATLAS detector

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    A search for new particles decaying into a pair of top quarks is performed using proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at a center-of-mass energy of √s=13  TeV corresponding to an integrated luminosity of 36.1  fb−1. Events consistent with top-quark pair production and the fully hadronic decay mode of the top quarks are selected by requiring multiple high transverse momentum jets including those containing b-hadrons. Two analysis techniques, exploiting dedicated top-quark pair reconstruction in different kinematic regimes, are used to optimize the search sensitivity to new hypothetical particles over a wide mass range. The invariant mass distribution of the two reconstructed top-quark candidates is examined for resonant production of new particles with various spins and decay widths. No significant deviation from the Standard Model prediction is observed and limits are set on the production cross-section times branching fraction for new hypothetical Z′ bosons, dark-matter mediators, Kaluza-Klein gravitons and Kaluza-Klein gluons. By comparing with the predicted production cross sections, the Z′ boson in the topcolor-assisted-technicolor model is excluded for masses up to 3.1–3.6 TeV, the dark-matter mediators in a simplified framework are excluded in the mass ranges from 0.8 to 0.9 TeV and from 2.0 to 2.2 TeV, and the Kaluza-Klein gluon is excluded for masses up to 3.4 TeV, depending on the decay widths of the particles
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