Search results for "Particle physics"
showing 10 items of 6826 documents
Evidence for the associated production of a W boson and a top quark in ATLAS at √s = 7 TeV
2012
This Letter presents evidence for the associated production of a W boson and a top quark using 2.05 fb[superscript −1] of pp collision data at √s = 7 TeV accumulated with the ATLAS detector at the LHC. The analysis is based on the selection of the dileptonic final states with events featuring two isolated leptons, electron or muon, with significant transverse missing momentum and at least one jet. An approach based on boosted decision trees has been developed to improve the discrimination of single top-quark Wt events from background. A template fit to the final classifier distributions is performed to determine the cross-section. The result is incompatible with the background-only hypothes…
Combination of D0 measurements of the top quark mass
2017
We present a combination of measurements of the top quark mass by the D0 experiment in the lepton+jets and dilepton channels. We use all the data collected in Run I (1992--1996) at $\sqrt s=1.8$ TeV and Run II (2001--2011) at $\sqrt s=1.96$ TeV of the Tevatron $p \bar{p}$ collider, corresponding to integrated luminosities of 0.1 fb$^{-1}$ and 9.7 fb$^{-1}$, respectively. The combined result is: $m_t = 174.95 \pm0.40\,{\rm(stat)} \pm 0.64\,{\rm(syst)}\,{\rm{GeV}}=174.95 \pm 0.75 \, {\rm{GeV}}$.
Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
2018
The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of √s=1.96 TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is At¯tFB=0.128±0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions.
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
2016
We measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in top-antitop to lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/- 0.85(syst) GeV.
Revisiting the axial form factor of the nucleon for low Q2 pion electroproduction
2003
Abstract An extensive programme of charged pion electroproduction off the proton has been performed at the three-spectrometer facility at the Mainz Microton MAMI. The reaction p ( e , e ′ π + ) n was measured at a constant invariant mass of W = 1125 MeV and four-momentum transfers of Q 2 = 0.058, 0.117, 0.195, and 0.273 (GeV/ c ) 2 . For each Q 2 value. measurements at different values of ϵ, the virtual photon polarization parameters, allow for a Rosenbluth separation of longitudinal and transverse cross sections. Preliminary results from new measurements in 2000 and 2002 seem to indicate that the transverse cross section at lower Q 2 values is considerably lower than expected from previous…
Model for T2K indication with maximalθ23and trimaximalθ12
2011
Recently T2K experiment gives hint in favor of large reactor angle ${\ensuremath{\theta}}_{13}$. Most of the models, with tribimaximal mixing at the leading order, can not reproduce such a large mixing angle since they predict typically corrections for the reactor angle of the order ${\ensuremath{\theta}}_{13}\ensuremath{\sim}{\ensuremath{\lambda}}_{C}^{2}$, where ${\ensuremath{\lambda}}_{C}\ensuremath{\sim}0.2$. In this paper, we discuss the possibility to achieve large ${\ensuremath{\theta}}_{13}$ within the T2K region with maximal atmospheric mixing angle, ${sin}^{2}{\ensuremath{\theta}}_{23}=1/2$, and trimaximal solar mixing angle, ${sin}^{2}{\ensuremath{\theta}}_{12}=1/3$, through th…
S-4 as a natural flavor symmetry for lepton mixing
2008
Group theoretical arguments seem to indicate the discrete symmetry S4 as the minimal flavour symmetry compatible with tribimaximal neutrino mixing. We prove in a model independent way that indeed S4 can realize exact tribimaximal mixing through different symmetry breaking patterns. We present two models in which lepton tribimaximal mixing is realized in different ways and for each one we discuss the superpotential that leads to the correct breaking of the flavor symmetry.
Tracking the Preferences of Users Using Weak Estimators
2011
Published version of am article from the book:AI 2011: Advances in Artificial Intelligence. Also available from the publisher on SpringerLink:http://dx.doi.org/10.1007/978-3-642-25832-9_81 Since a social network, by definition, is so diverse, the problem of estimating the preferences of its users is becoming increasingly essential for personalized applications which range from service recommender systems to the targeted advertising of services. However, unlike traditional estimation problems where the underlying target distribution is stationary, estimating a user’s interests, typically, involves non-stationary distributions. The consequent time varying nature of the distribution to be trac…
Adaptive Tracking Control of Nonlinear Time-Varying Systems with Unknown Control Coefficients and Unknown Time-Varying Parameters
2019
This paper investigates the tracking control of a class of strict-feedback uncertain nonlinear systems in the presence of unknown signs of control coefficients and unknown time-varying parameters as well as unknown disturbances. A robust adaptive controller and a new decoupled backstepping approach to stability analysis are developed by constructing a new compensation scheme. By introducing a Nussbaum function and a new type of hyperbolic tangent function, the effects of unknown time-varying parameters and unknown control coefficients are effectively compensated. By using the decoupled backstepping technique, it is proved that under the proposed control, all closed-loop states are uniform u…
DEPFET Active Pixel Detectors for a Future Linear e(+)e(-) Collider
2013
arXiv:1212.2160v1.-- et al.