Eur Phys J C Part Fields
January 2016
Searches for pair-produced scalar leptoquarks are performed using 20 fb[Formula: see text] of proton-proton collision data provided by the LHC and recorded by the ATLAS detector at [Formula: see text] TeV. Events with two electrons (muons) and two or more jets in the final state are used to search for first (second)-generation leptoquarks. The results from two previously published ATLAS analyses are interpreted in terms of third-generation leptoquarks decaying to [Formula: see text] and [Formula: see text] final states.
View Article and Find Full Text PDFEur Phys J C Part Fields
January 2016
The decays [Formula: see text] and [Formula: see text] are studied with the ATLAS detector at the LHC using a dataset corresponding to integrated luminosities of 4.9 and 20.6 fb[Formula: see text] of collisions collected at centre-of-mass energies [Formula: see text] TeV and 8 TeV, respectively.
View Article and Find Full Text PDFWith an integrated luminosity of 2.47 fb(-1) recorded by the ATLAS experiment at the LHC, the exclusive decays B(s)(0)→J/ψϕ and B(d)(0)→J/ψK(*0) of B mesons produced in pp collisions at √s=7 TeV are used to determine the ratio of fragmentation fractions f(s)/f(d). From the observed B(s)(0)→J/ψϕ and B(d)(0)→J/ψK(*0) yields, the quantity (f(s)/f(d))[B(B(s)(0)→J/ψϕ)/B(B(d)(0)→J/ψK(*0))] is measured to be 0.
View Article and Find Full Text PDFA study of the decays [Formula: see text] and [Formula: see text] has been performed using data corresponding to an integrated luminosity of 25 fb[Formula: see text] of 7 and 8 TeV proton-proton collisions collected with the ATLAS detector during the LHC Run 1. For the [Formula: see text] dimuon decay, an upper limit on the branching fraction is set at [Formula: see text] at 95 % confidence level. For [Formula: see text], the branching fraction [Formula: see text] is measured.
View Article and Find Full Text PDFA search for squarks and gluinos in final states containing hadronic jets, missing transverse momentum but no electrons or muons is presented. The data were recorded in 2015 by the ATLAS experiment in [Formula: see text] proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 3.
View Article and Find Full Text PDFA search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton has been performed using 3.2 fb[Formula: see text] of proton-proton collision data at [Formula: see text] recorded by the ATLAS detector at the Large Hadron Collider in 2015. Two exclusive final states are considered, with either exactly one or at least two tau leptons.
View Article and Find Full Text PDFMeasurements of normalized differential cross-sections of top-quark pair production are presented as a function of the top-quark, [Formula: see text] system and event-level kinematic observables in proton-proton collisions at a centre-of-mass energy of [Formula: see text]. The observables have been chosen to emphasize the [Formula: see text] production process and to be sensitive to effects of initial- and final-state radiation, to the different parton distribution functions, and to non-resonant processes and higher-order corrections. The dataset corresponds to an integrated luminosity of 20.
View Article and Find Full Text PDFMeasurements of distributions of charged particles produced in proton-proton collisions with a centre-of-mass energy of 13 TeV are presented. The data were recorded by the ATLAS detector at the LHC and correspond to an integrated luminosity of 151 [Formula: see text]. The particles are required to have a transverse momentum greater than 100 MeV and an absolute pseudorapidity less than 2.
View Article and Find Full Text PDFEur Phys J C Part Fields
December 2016
The dijet production cross section for jets containing a -hadron (-jets) has been measured in proton-proton collisions with a centre-of-mass energy of [Formula: see text] TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of [Formula: see text]. The cross section is measured for events with two identified -jets with a transverse momentum [Formula: see text] GeV and a minimum separation in the [Formula: see text]-[Formula: see text] plane of [Formula: see text].
View Article and Find Full Text PDFEur Phys J C Part Fields
December 2016
The algorithms used by the ATLAS Collaboration to reconstruct and identify prompt photons are described. Measurements of the photon identification efficiencies are reported, using 4.9 fb[Formula: see text] of collision data collected at the LHC at [Formula: see text] [Formula: see text] and 20.
View Article and Find Full Text PDFA test of CP invariance in Higgs boson production via vector-boson fusion using the method of the is presented. The analysis exploits the decay mode of the Higgs boson into a pair of [Formula: see text] leptons and is based on 20.3 [Formula: see text] of proton-proton collision data at [Formula: see text] = 8 [Formula: see text] collected by the ATLAS experiment at the LHC.
View Article and Find Full Text PDFEur Phys J C Part Fields
November 2016
The luminosity determination for the ATLAS detector at the LHC during collisions at [Formula: see text] 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of [Formula: see text] is obtained for the [Formula: see text] of collision data delivered to ATLAS at [Formula: see text] 8 TeV in 2012.
View Article and Find Full Text PDFThis paper presents a dedicated search for exotic decays of the Higgs boson to a pair of new spin-zero particles, [Formula: see text], where the particle decays to -quarks and has a mass in the range of 20-60 GeV. The search is performed in events where the Higgs boson is produced in association with a [Formula: see text] boson, giving rise to a signature of a lepton (electron or muon), missing transverse momentum, and multiple jets from -quark decays. The analysis is based on the full dataset of collisions at [Formula: see text] recorded in 2015 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 3.
View Article and Find Full Text PDFA search for neutral Higgs bosons of the minimal supersymmetric standard model (MSSM) and for a heavneutral [Formula: see text] boson is performed using a data sample corresponding to an integrated luminosity of 3.2 fb[Formula: see text] from proton-proton collisions at [Formula: see text] [Formula: see text] recorded by the ATLAS detector at the LHC. The heavy resonance is assumed to decay to a [Formula: see text] pair with at least one [Formula: see text] lepton decaying to final states with hadrons and a neutrino.
View Article and Find Full Text PDFThe large rate of multiple simultaneous proton-proton interactions, or pile-up, generated by the Large Hadron Collider in Run 1 required the development of many new techniques to mitigate the adverse effects of these conditions. This paper describes the methods employed in the ATLAS experiment to correct for the impact of pile-up on jet energy and jet shapes, and for the presence of spurious additional jets, with a primary focus on the large 20.3 [Formula: see text] data sample collected at a centre-of-mass energy of [Formula: see text].
View Article and Find Full Text PDFThe results of a search for gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a centre-of-mass energy of [Formula: see text] are presented. The dataset used was recorded in 2015 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 3.2 fb[Formula: see text].
View Article and Find Full Text PDFEur Phys J C Part Fields
October 2016
The result of a search for pair production of the supersymmetric partner of the Standard Model bottom quark ([Formula: see text]) is reported. The search uses 3.2 fb[Formula: see text] of collisions at [Formula: see text] TeV collected by the ATLAS experiment at the Large Hadron Collider in 2015.
View Article and Find Full Text PDFA search is performed for a heavy particle decaying into different flavour dilepton pairs ([Formula: see text], [Formula: see text] or [Formula: see text]), using 3.2 fb[Formula: see text] of proton-proton collision data at [Formula: see text] TeV collected in 2015 by the ATLAS detector at the Large Hadron Collider. No excess over the Standard Model prediction is observed.
View Article and Find Full Text PDFEur Phys J C Part Fields
September 2016
The performance of the jet trigger for the ATLAS detector at the LHC during the 2011 data taking period is described. During 2011 the LHC provided proton-proton collisions with a centre-of-mass energy of 7 TeV and heavy ion collisions with a 2.76 TeV per nucleon-nucleon collision energy.
View Article and Find Full Text PDFA search has been made for supersymmetry in a final state containing two photons and missing transverse momentum using the ATLAS detector at the Large Hadron Collider. The search makes use of [Formula: see text] of proton-proton collision data collected at a centre-of-mass energy of 13 TeV in 2015. Using a combination of data-driven and Monte-Carlo-based approaches, the Standard Model background is estimated to be [Formula: see text] events.
View Article and Find Full Text PDFA search for singly produced vector-like quarks, where can be either a quark with charge [Formula: see text] or a quark with charge [Formula: see text], is performed in proton-proton collisions recorded with the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 20.3 fb[Formula: see text] and was produced with a centre-of-mass energy of [Formula: see text] TeV.
View Article and Find Full Text PDFEur Phys J C Part Fields
July 2016
This paper presents measurements of distributions of charged particles which are produced in proton-proton collisions at a centre-of-mass energy of [Formula: see text] and recorded by the ATLAS detector at the LHC. A special dataset recorded in 2012 with a small number of interactions per beam crossing (below 0.004) and corresponding to an integrated luminosity of 160 [Formula: see text] was used.
View Article and Find Full Text PDFEur Phys J C Part Fields
June 2016
The number of charged particles inside jets is a widely used discriminant for identifying the quark or gluon nature of the initiating parton and is sensitive to both the perturbative and non-perturbative components of fragmentation. This paper presents a measurement of the average number of charged particles with [Formula: see text] [Formula: see text] inside high-momentum jets in dijet events using 20.3 fb[Formula: see text] of data recorded with the ATLAS detector in collisions at [Formula: see text] [Formula: see text] collisions at the LHC.
View Article and Find Full Text PDFEur Phys J C Part Fields
May 2016
This paper presents a new method of reconstructing the individual charged and neutral hadrons in tau decays with the ATLAS detector. The reconstructed hadrons are used to classify the decay mode and to calculate the visible four-momentum of reconstructed tau candidates, significantly improving the resolution with respect to the calibration in the existing tau reconstruction. The performance of the reconstruction algorithm is optimised and evaluated using simulation and validated using samples of [Formula: see text] and [Formula: see text]+jets events selected from proton-proton collisions at a centre-of-mass energy [Formula: see text], corresponding to an integrated luminosity of 5 [Formula: see text].
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