The ATLAS detector at the LHC is used to search for excited electrons and excited muons in the channel pp -> ll* -> llgamma, assuming that excited leptons are produced via contact interactions. The ...analysis is based on 13 fb-1 of pp collisions at a centre-of-mass energy of 8 TeV. No evidence for excited leptons is found, and a limit is set at the 95% credibility level on the cross section times branching ratio as a function of the excited-lepton mass m_l*. For m_l* > 0.8 TeV, the respective upper limits on sigma*B(l* -> lgamma) are 0.75 fb and 0.90 fb for the e* and mu* searches. Limits on sigma*B are converted into lower bounds on the compositeness scale Lambda. In the special case where Lambda = m_l*, excited-electron and excited-muon masses below 2.2 TeV are excluded.
This article describes a search for high-mass resonances decaying to a pair of photons using a sample of 20.3 fb-1 of pp collisions at s=8 TeV recorded with the ATLAS detector at the Large Hadron ...Collider. The data are found to be in agreement with the Standard Model prediction, and limits are reported in the framework of the Randall-Sundrum model. This theory leads to the prediction of graviton states, the lightest of which could be observed at the Large Hadron Collider. A lower limit of 2.66 (1.41) TeV at 95% confidence level is set on the mass of the lightest graviton for couplings of k/M¯Pl=0.1 (0.01).
A search is presented for direct chargino production based on a disappearing-track signature using 20.3 fb super(-1) of proton-proton collisions at radicals = 8 TeV collected with the ATLAS ...experiment at the LHC. In anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is nearly mass degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. Some models with supersymmetry also predict charginos with a significant lifetime. This analysis attains sensitivity for charginos with a lifetime between 0.1 and 10 ns, and significantly surpasses the reach of the LEP experiments. No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level.
A search has been performed for pair production of heavy vectorlike down-type (B) quarks. The analysis explores the lepton-plus-jets final state, characterized by events with one isolated charged ...lepton (electron or muon), significant missing transverse momentum, and multiple jets. One or more jets are required to be tagged as arising from b quarks, and at least one pair of jets must be tagged as arising from the hadronic decay of an electroweak boson. The analysis uses the full data sample of pp collisions recorded in 2012 by the ATLAS detector at the LHC, operating at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3 fb super(-1). No significant excess of events is observed above the expected background. Limits are set on vectorlike B production, as a function of the B branching ratios, assuming the allowable decay modes are B arrow right Wt/Zb/Hb. In the chiral limit with a branching ratio of 100% for the decay B arrow right Wt, the observed (expected) 95% C.L. lower limit on the vectorlike B mass is 810 GeV (760 GeV). In the case where the vectorlike B quark has branching ratio values corresponding to those of an SU(2) singlet state, the observed (expected) 95% C.L. lower limit on the vectorlike B mass is 640 GeV (505 GeV). The same analysis, when used to investigate pair production of a colored, charge 5/3 exotic fermion T sub(5/3), with subsequent decay T sub(5/3) arrow right Wt, sets an observed (expected) 95% C.L. lower limit on the T sub(5/3) mass of 840 GeV (780 GeV).
A measurement of the Higgs boson mass is presented based on the combined data samples of the ATLAS and CMS experiments at the CERN LHC in the H arrow right gamma gamma and H arrow right ZZ arrow ...right 4scriptl decay channels. The results are obtained from a simultaneous fit to the reconstructed invariant mass peaks in the two channels and for the two experiments. The measured masses from the individual channels and the two experiments are found to be consistent among themselves. The combined measured mass of the Higgs boson is mH=125.09+ or -0.21 (stat)+ or -0.11 (syst) GeV.
The reconstruction of the signal from hadrons and jets emerging from the proton–proton collisions at the Large Hadron Collider (LHC) and entering the ATLAS calorimeters is based on a ...three-dimensional topological clustering of individual calorimeter cell signals. The cluster formation follows cell signal-significance patterns generated by electromagnetic and hadronic showers. In this, the clustering algorithm implicitly performs a topological noise suppression by removing cells with insignificant signals which are not in close proximity to cells with significant signals. The resulting
topological cell clusters
have shape and location information, which is exploited to apply a local energy calibration and corrections depending on the nature of the cluster. Topological cell clustering is established as a well-performing calorimeter signal definition for jet and missing transverse momentum reconstruction in ATLAS.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, ...corresponding to an integrated luminosity of 4.6 fb super(-1). Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Standard Model prediction at next-to-leading-order accuracy.
With advances in medical care, more youth with intellectual and/or developmental disabilities (IDD) are transitioning into adulthood. Patient- and family-centered, integrated care is warranted around ...this time of transition. Support teams (including the youth, caregivers, teachers, and pediatricians) should engage in transition planning, ideally starting between 12 and 14 years of age, to identify and develop resources to support the maturing youth's capacity for independent decision-making. Care teams should consider the varied levels of alternative decision-making support, which may include supported decision-making, medical proxy decision-making, power of attorney, and/or establishment of legal guardianship arrangements, to support the youth's health and well-being optimally. Ultimately, if independent decision-making is not appropriate, the goal for youth with IDD should be the least restrictive alternative, while preserving human rights and human dignity and promoting their autonomy. These considerations review alternative decision-making support, concepts, and legal requirements available for youth with IDD and their care teams. Pediatricians can support youth with IDD and their families in the transition process and decision-making autonomy by actively engaging the youth in care decisions, supporting needs for augmentative communication, fostering their expression of preferences and understanding of care decisions, and linking them to resources such as the medical-legal partnership model.
A search for the Standard Model Higgs boson produced in association with a top-quark pair, Formula: see text, is presented. The analysis uses 20.3 fb
of
collision data at Formula: see text, collected ...with the ATLAS detector at the Large Hadron Collider during 2012. The search is designed for the Formula: see text decay mode and uses events containing one or two electrons or muons. In order to improve the sensitivity of the search, events are categorised according to their jet and
-tagged jet multiplicities. A neural network is used to discriminate between signal and background events, the latter being dominated by Formula: see text+jets production. In the single-lepton channel, variables calculated using a matrix element method are included as inputs to the neural network to improve discrimination of the irreducible Formula: see text background. No significant excess of events above the background expectation is found and an observed (expected) limit of 3.4 (2.2) times the Standard Model cross section is obtained at 95 % confidence level. The ratio of the measured Formula: see text signal cross section to the Standard Model expectation is found to be Formula: see text assuming a Higgs boson mass of 125Formula: see text.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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