Showing papers by "Victoria Jane Martin published in 2016"
TL;DR: In this paper, a measurement of the inelastic proton-proton cross section using 60''μb^{-1} of pp collisions at a center-of-mass energy sqrt[s] of 13'TeV with the ATLAS detector at the LHC is presented.
Abstract: This Letter presents a measurement of the inelastic proton-proton cross section using 60 μb^{-1} of pp collisions at a center-of-mass energy sqrt[s] of 13 TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region (2.07 10^{-6}, where M_{X} is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this ξ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with M_{X}>13 GeV. The measured cross section is compared with a range of theoretical predictions. When extrapolated to the full phase space, a cross section of 78.1±2.9 mb is measured, consistent with the inelastic cross section increasing with center-of-mass energy.
191 citations
TL;DR: In this article, the authors describe a model-agnostic search for pairs of jets (dijets) produced by resonant and non-resonant phenomena beyond the Standard Model.
185 citations
TL;DR: In this article, the authors measured the transverse momentum and the related angular variable of DrellΓCoYan lepton pairs with the ATLAS detector at the LHC and compared their results to predictions from perturbative and resummed QCD calculations.
Abstract: Distributions of transverse momentum [Formula: see text] and the related angular variable [Formula: see text] of DrellΓCoYan lepton pairs are measured in 20.3┬afb[Formula: see text] of protonΓCoproton collisions at [Formula: see text]┬aTeV with the ATLAS detector at the LHC. Measurements in electron-pair and muon-pair final states are corrected for detector effects and combined. Compared to previous measurements in protonΓCoproton collisions at [Formula: see text]┬aTeV, these new measurements benefit from a larger data sample and improved control of systematic uncertainties. Measurements are performed in bins of lepton-pair mass above, around and below the Z-boson mass peak. The data are compared to predictions from perturbative and resummed QCD calculations. For values of [Formula: see text] the predictions from the Monte Carlo generator ResBos are generally consistent with the data within the theoretical uncertainties. However, at larger values of [Formula: see text] this is not the case. Monte Carlo generators based on the parton-shower approach are unable to describe the data over the full range of [Formula: see text] while the fixed-order prediction of Dynnlo falls below the data at high values of [Formula: see text]. ResBos and the parton-shower Monte Carlo generators provide a much better description of the evolution of the [Formula: see text] and [Formula: see text] distributions as a function of lepton-pair mass and rapidity than the basic shape of the data.
160 citations
TL;DR: In this article, a search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge or at the same location.
Abstract: A search for strongly produced supersymmetric particles is conducted using signatures involving multiple energetic jets and either two isolated leptons (e or μ) with the same electric charge or at ...
159 citations
TL;DR: In this article, an inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment, where first and second generation leptoquarks were sought in events with two electrons (muons) and two or more jets.
Abstract: An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at √s = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb−1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results.
130 citations
TL;DR: In this paper, measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV were presented, where the gauge bosons were reconstructed using their leptonic decay modes into electrons and m...
Abstract: This paper presents measurements of W(+/-)Z production in pp collisions at a center-of-mass energy of 8 TeV. The gauge bosons are reconstructed using their leptonic decay modes into electrons and m ...
126 citations
TL;DR: Results of a search for new phenomena in events with at least three photons are reported, with limits at the 95 % confidence level on new phenomena presented based on the rate of events in an inclusive signal region and a restricted signal region targeting the rare decay of the Higgs boson.
Abstract: Results of a search for new phenomena in events with at least three photons are reported. Data from proton-proton collisions at a centre-of-mass energy of 8 TeV, corresponding to an integrated lumi ...
104 citations
TL;DR: In this paper, a 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.
Abstract: A 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 ...
96 citations
TL;DR: In this paper, the authors presented evidence for single top-quark production in the s-channel using proton-proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS detector at the CERN Large Hadron Co...
95 citations
TL;DR: In this paper, the results from two previously published ATLAS analyses are interpreted in terms of third-generation leptoquarks decaying to [formula: see text] and [Formula] final states.
Abstract: 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. No statistically significant excess above the Standard Model expectation is observed in any channel and scalar leptoquarks are excluded at 95 % CL with masses up to [Formula: see text] 1050 GeV for first-generation leptoquarks, [Formula: see text] 1000 GeV for second-generation leptoquarks, [Formula: see text] 625 GeV for third-generation leptoquarks in the [Formula: see text] channel, and 200 [Formula: see text] 640 GeV in the [Formula: see text] channel.
91 citations
TL;DR: In this article, a measurement of the double-differential cross section for the Drell-Yan Z/γ∗ → l+l− and photon-induced γγ → l + l− processes where l is an electron or muon was performed for invariant masses of the lepton pairs, mll, between 116 GeV and 1500 GeV.
Abstract: This paper presents a measurement of the double-differential cross section for the Drell-Yan Z/γ∗ → l+l− and photon-induced γγ → l+l− processes where l is an electron or muon. The measurement is performed for invariant masses of the lepton pairs, mll, between 116 GeV and 1500 GeV using a sample of 20.3 fb−1 of pp collisions data at centre-of-mass energy of s=8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented double differentially in invariant mass and absolute dilepton rapidity as well as in invariant mass and absolute pseudorapidity separation of the lepton pair. The single-differential cross section as a function of mll is also reported. The electron and muon channel measurements are combined and a total experimental precision of better than 1% is achieved at low mll. A comparison to next-to-next-to-leading order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading order electroweak effects indicates the potential of the data to constrain parton distribution functions. In particular, a large impact of the data on the photon PDF is demonstrated.[Figure not available: see fulltext.]
TL;DR: Contributions from CP-violating interactions between the Higgs boson and electroweak gauge bosons are described in an effective field theory framework, in which the strength of CP violation is governed by a single parameter.
Abstract: A test of CP invariance in Higgs boson production via vector-boson fusion using the method of the Optimal Observable is presented. The analysis exploits the decay mode of the Higgs boson into a pai ...
TL;DR: In this paper, a detailed study of techniques for identifying boosted, hadronically decaying W bosons using 20.3 fb −¹ of proton-proton collision data collected by the ATLAS detector at the LHC at a center-of-mass energy √s = 8 TeV.
Abstract: This paper reports a detailed study of techniques for identifying boosted, hadronically decaying W bosons using 20.3 fb −¹ of proton–proton collision data collected by the ATLAS detector at the LHC at a centre-of-mass energy √s = 8 TeV. A range of techniques for optimising the signal jet mass resolution are combined with various jet substructure variables. The results of these studies in Monte Carlo simulations show that a simple pairwise combination of groomed jet mass and one substructure variable can provide a 50 % efficiency for identifying W bosons with transverse momenta larger than 200 GeV while maintaining multijet background efficiencies of 2–4 % for jets with the same transverse momentum. These signal and background efficiencies are confirmed in data for a selection of tagging techniques.
TL;DR: In this paper, a measurement of the complete set of angular coefficients A0−7 describing these distributions in the Z-boson Collins-Soper frame was presented, which correspond to 20.3 fb−1 of pp collisions at s=8 TeV, collected by the ATLAS detector at the CERN LHC.
Abstract: The angular distributions of Drell-Yan charged lepton pairs in the vicinity of the Z-boson mass peak probe the underlying QCD dynamics of Z-boson production. This paper presents a measurement of the complete set of angular coefficients A0−7 describing these distributions in the Z-boson Collins-Soper frame. The data analysed correspond to 20.3 fb−1 of pp collisions at s=8 TeV, collected by the ATLAS detector at the CERN LHC. The measurements are compared to the most precise fixed-order calculations currently available (O(αs2)) and with theoretical predictions embedded in Monte Carlo generators. The measurements are precise enough to probe QCD corrections beyond the formal accuracy of these calculations and to provide discrimination between different parton-shower models. A significant deviation from the (O(αs2)) predictions is observed for A0 − A2. Evidence is found for non-zero A5,6,7, consistent with expectations.[Figure not available: see fulltext.]
TL;DR: A measurement of the average number of charged particles inside jets using 20.3 fb of data recorded with the ATLAS detector in dijet events using quark and gluon jet fractions and the resulting charged-particle multiplicity is compared to several models.
Abstract: 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-pertur ...
TL;DR: In this article, a search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb(-1) of proton-proton collision data at root s = 8 TeV.
Abstract: A search for direct pair production of the supersymmetric partner of the top quark, decaying via a scalar tau to a nearly massless gravitino, has been performed using 20 fb(-1) of proton-proton collision data at root s = 8 TeV. The data were collected by the ATLAS experiment at the LHC in 2012. Top squark candidates are searched for in events with either two hadronically decaying tau leptons, one hadronically decaying tau and one light lepton, or two light leptons. No significant excess over the Standard Model expectation is found. Exclusion limits at 95 % confidence level are set as a function of the top squark and scalar tau masses. Depending on the scalar tau mass, ranging from the 87 GeV LEP limit to the top squark mass, lower limits between 490 and 650 GeV are placed on the top squark mass within the model considered.
TL;DR: In this paper, the authors measured the charged particle distributions in proton-proton collisions at a center-of-mass energy of 13 TeV, using a data sample of nearly 9 million events, corresponding to an integrated luminosity.
TL;DR: The production rates of prompt and non-prompt mesons in their dimuon decay modes are measured using data collected with the ATLAS experiment at the Large Hadron Collider, in proton–proton collisions at s=7 and 8 respectively.
Abstract: The production rates of prompt and non-prompt J/psi and psi(2S) mesons in their dimuon decay modes are measured using 2.1 and 11.4 fb(-1) of data collected with the ATLAS experiment at the Large Ha ...
TL;DR: In this paper, the 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 13 TeV are presented.
Abstract: The 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 $\sqrt{s}$ = 13 TeV 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$^{-1}$. Six signal selections are defined that best exploit the signal characteristics. The data agree with the Standard Model background expectation in all six signal selections, and the largest deviation is a 2.1 standard deviation excess. The results are interpreted in a simplified model where pair-produced gluinos decay via the lightest chargino to the lightest neutralino. In this model, gluinos are excluded up to masses of approximately 1.6 TeV depending on the mass spectrum of the simplified model, thus surpassing the limits of previous searches.
TL;DR: In this paper, the production of W-+/- Z events in proton-proton collisions at a centre-of-mass energy of 13 TeV is measured with the ATLAS detector at the LHC.
TL;DR: In this paper, the ATLAS experiment at the Large Hadron Collider was used to measure photon production in root S-NN = 2.76-TeV Pb + Pb collisions.
Abstract: Prompt photon production in root S-NN = 2.76-TeV Pb + Pb collisions has been measured by the ATLAS experiment at the Large Hadron Collider using data collected in 2011 with an integrated luminosity ...
TL;DR: In this article, high-mass resonances in the dijet invariant mass spectrum with one or two jets identified as $b$-jets are performed using an integrated luminosity of $3.2$ fb$^{-1}$ of proton--proton collisions with a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the Large Hadron Collider.
TL;DR: In this paper, the per-event charged particle yield as a function of the charged-particle transverse momentum and rapidity is performed using p+Pbp+Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of sqrt (SNN) = 5.01 TeV.
TL;DR: In this article, the cross-section for the production of a single top quark in association with a W boson in proton-proton collisions at is measured and the dataset corresponds to an integrated luminosity of 20.3 fb(-...
Abstract: The cross-section for the production of a single top quark in association with a W boson in proton-proton collisions at is measured. The dataset corresponds to an integrated luminosity of 20.3 fb(- ...
TL;DR: In this paper, the authors measured the centrality dependence of the mean charged-particle multiplicity as a function of pseudorapidity in approximately 1 mu b−1 of proton-lead collisions at a nucleon-nucleon center-of-mass energy of root s(NN) = 502 TeV using the ATLAS detector at the Large Hadron Collider.
Abstract: The centrality dependence of the mean charged-particle multiplicity as a function of pseudorapidity is measured in approximately 1 mu b(-1) of proton-lead collisions at a nucleon-nucleon centre-of-mass energy of root s(NN) = 502 TeV using the ATLAS detector at the Large Hadron Collider Charged particles with absolute pseudorapidity less than 27 are reconstructed using the ATLAS pixel detector The p + Pb collision centrality is characterised by the total transverse energy measured in the Pb-going direction of the forward calorimeter The charged-particle pseudorapidity distributions are found to vary strongly with centrality, with an increasing asymmetry between the proton-going and Pb-going directions as the collisions become more central Three different estimations of the number of nucleons participating in the p + Pb collision have been carried out using the Glauber model as well as two Glauber-Gribov inspired extensions to the Glauber model Charged-particle multiplicities per participant pair are found to vary differently for these three models, highlighting the importance of including colour fluctuations in nucleon-nucleon collisions in the modelling of the initial state of p + Pb collisions
TL;DR: In this paper, the production of $W$ boson pairs in proton-proton collisions at 8 TeV was studied using data corresponding to 20.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider.
Abstract: The production of $W$ boson pairs in proton-proton collisions at $\sqrt{s}=$ 8 TeV is studied using data corresponding to 20.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The $W$ bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 $WW$ candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the $W$ branching fractions to leptons in order to obtain the total $WW$ production cross section, which is found to be 71.1$\pm1.1$(stat)$^{+5.7}_{-5.0}$(syst)$\pm1.4$ pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2$^{+1.6}_{-1.4}$(scale)$\pm1.2$(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.
TL;DR: A search for single top-quarks production via flavour-changing neutral current processes from gluon plus up- or charm-quark initial states in proton–proton collisions at the LHC is presented and an upper limit on the production cross-section multiplied by the t→Wb branching fraction is set.
Abstract: A search for single top-quark production via flavour-changing neutral current processes from gluon plus up- or charm-quark initial states in proton-proton collisions at the LHC is presented. Data collected with the ATLAS detector in 2012 at a centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb[Formula: see text] are used. Candidate events for a top quark decaying into a lepton, a neutrino and a jet are selected and classified into signal- and background-like candidates using a neural network. No signal is observed and an upper limit on the production cross-section multiplied by the [Formula: see text] branching fraction is set. The observed 95 % CL limit is [Formula: see text] and the expected 95 % CL limit is [Formula: see text]. The observed limit can be interpreted as upper limits on the coupling constants of the flavour-changing neutral current interactions divided by the scale of new physics [Formula: see text] and [Formula: see text] and on the branching fractions [Formula: see text] and [Formula: see text].
TL;DR: The production of D*(+/-), D-+/- and D-S charmed mesons has been measured with the ATLAS detector in pp collisions at,/7s = 7 TeV at the LHC, using data corresponding to an integrated luminosi...
TL;DR: A search for neutral Higgs bosons of the minimal supersymmetric standard model (MSSM) and for a heavneutral Z′ boson is performed using a data sample corresponding to an integrated luminosity of 3.2 fb from proton–proton collisions at the LHC.
Abstract: A search for neutral Higgs bosons of the minimal supersymmetric standard model (MSSM) and for a heavneutral Z' boson is performed using a data sample corresponding to an integrated luminosity of 3. ...
TL;DR: The data acquisition and high level trigger system of the ATLAS experiment at the Large Hadron Collider at CERN, as deployed during Run 1, is described.
Abstract: This paper describes the data acquisition and high level trigger system of the ATLAS experiment at the Large Hadron Collider at CERN, as deployed during Run 1. Data flow as well as control, configuration and monitoring aspects are addressed. An overview of the functionality of the system and of its performance is presented and design choices are discussed.