A search for an unexpected asymmetry in the production of $e^+ μ^-$ and $e^- μ^+$ pairs in proton-proton collisions recorded by the ATLAS detector at $\sqrt s = 13$ TeV
This search, a type not previously performed at ATLAS, uses a comparison of the production cross sections for $e^+ μ^-$ and $e^- μ^+$ pairs to constrain physics processes beyond the Standard Model. It uses $139 \text{fb}^{-1}$ of proton$-$proton collision data recorded at $\sqrt{s} = 13$ TeV at the LHC. Targeting sources of new physics which prefer final states containing $e^{+}μ^{-}$ to $e^{-}μ^{+}$, the search contains two broad signal regions which are used to provide model-independent constraints on the ratio of cross sections at the 2% level. The search also has two special selections targeting supersymmetric models and leptoquark signatures. Observations using one of these selections are able to exclude, at 95% confidence level, singly produced smuons with masses up to 640 GeV in a model in which the only other light sparticle is a neutralino when the $R$-parity-violating coupling $λ'_{231}$ is close to unity. Observations using the other selection exclude scalar leptoquarks with masses below 1880 GeV when $g_{\text{1R}}^{eu}=g_{\text{1R}}^{μc}=1$, at 95% confidence level. The limit on the coupling reduces to $g_{\text{1R}}^{eu}=g_{\text{1R}}^{μc}=0.46$ for a mass of 1420 GeV.
The measurement of the jet energy resolution is presented using data recorded with the ATLAS detector in proton-proton collisions at sqrt(s) = 7 TeV. The sample corresponds to an integrated luminosity of 35 pb-1. Jets are reconstructed from energy deposits measured by the calorimeters and calibrated using different jet calibration schemes. The jet energy resolution is measured with two different in situ methods which are found to be in agreement within uncertainties. The total uncertainties on these measurements range from 20% to 10% for jets within |y|<2.8 and with transverse momenta increasi…
Several extensions of the Standard Model predict the production of dark matter particles at the LHC. An uncharted signature of dark matter particles produced in association with $VV=W^\pm W^\mp$ or $ZZ$ pairs from a decay of a dark Higgs boson $s$ is searched for using 139 fb$^{-1}$ of $pp$ collisions recorded by the ATLAS detector at a center-of-mass energy of 13 TeV. The $s\to V(q\bar q)V(q\bar q)$ decays are reconstructed with a novel technique aimed at resolving the dense topology from boosted $VV$ pairs using jets in the calorimeter and tracking information. Dark Higgs scenarios with $m_s…
An overview of the latest results for top pair production in association with a vector gauge boson in the ATLAS detector at LHC is presented. The results involving $Z$ and $W$ bosons are recorded at $\sqrt{13}$ TeV collision energy, while the results involving photons are recorded at $\sqrt{7}$ TeV and $\sqrt{8}$ TeV collision energy.
The status of the ATLAS Higgs boson search using about 5 fb^-1 of data recorded in 2011 is summarized. Proceedings from Physics at the LHC 2012 (Vancouver).
Charged Higgs bosons produced in association with a single top quark and decaying via $H^{\pm} \rightarrow τν$ are searched for with the ATLAS experiment at the LHC, using proton-proton collision data at $\sqrt{s} = 13$ TeV corresponding to an integrated luminosity of 3.2 $\mathrm{fb}^{-1}$. The final state is characterised by the presence of a hadronic $τ$ decay and missing transverse momentum, as well as a hadronically decaying top quark, resulting in the absence of high-transverse-momentum electrons and muons. The data are found to be consistent with the expected background from Standard Mo…
Searches for non-resonant and resonant Higgs boson pair production are performed in the $γγWW^{*}$ channel with the final state of $γγ\ellνjj$ using 36.1 fb$^{-1}$ of proton-proton collision data recorded at a centre-of-mass energy of $\sqrt{s} = 13$ TeV by the ATLAS detector at the Large Hadron Collider. No significant deviation from the Standard Model prediction is observed. A 95% confidence-level observed upper limit of 7.7 pb is set on the cross section for non-resonant production, while the expected limit is 5.4 pb. A search for a narrow-width resonance $X$ decaying to a pair of Standard …
The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton-proton collisions at sqrt(s) = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9 fb. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In t…
Model-independent search for the presence of new physics in events including $H\rightarrowγγ$ with $\sqrt{s}$ = 13 TeV pp data recorded by the ATLAS detector at the LHC
本文利用ATLAS探测器139 fb$^{-1}$的13 TeV pp数据，对含$H\rightarrowγγ$的22种末态进行模型无关新物理搜索，未发现显著超出并给出95%置信水平截面上限及探测器效率。
Search for dark matter produced in association with a dark Higgs boson decaying into $W^{+}W^{-}$ in the one-lepton final state at $\sqrt{s}$=13 TeV using 139 fb$^{-1}$ of $pp$ collisions recorded with the ATLAS detector
本文利用ATLAS探测器139 fb$^{-1}$的13 TeV $pp$碰撞数据，搜寻与衰变为$W^{+}W^{-}$的暗Higgs玻色子协同产生的暗物质，未发现超出标准模型的异常，排除了质量在140至390 GeV的暗Higgs情景。
Charged Higgs bosons produced either in top-quark decays or in association with a top-quark, subsequently decaying via $H^{\pm} \to τ^{\pm}ν_τ$, are searched for in 36.1 fb$^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV recorded with the ATLAS detector. Depending on whether the top-quark produced together with $H^{\pm}$ decays hadronically or leptonically, the search targets $τ$+jets and $τ$+lepton final states, in both cases with a hadronically decaying $τ$-lepton. No evidence of a charged Higgs boson is found. For the mass range of $m_{H^{\pm}}$ = 90-2000 GeV, upper limits at th…
A 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$^{-1}$ of proton-proton collision data at $\sqrt{s}=13$ TeV 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. No excess over the Standard Model prediction is observed in the data. Results are interpreted in the context of gauge-mediated supersymmetry breaking and a simplified model of gluino pair production with tau-ri…
Recent results on searches for third generation supersymmetry carried out by the ATLAS collaboration with 2.05 fb-1 of sqrt(s) = 7 TeV pp collisions recorded with the LHC in 2011 are reported. These analyses focus on search for gluino- and squark-mediated stau production, direct scalar bottom pair production and gluino-mediated sbottom and stop pair production.
The latest search for the Standard Model (SM) Higgs boson based on 4.7-4.9 fb-1 of pp collision data at sqrt(s)=7 TeV recorded with the ATLAS detector is presented here.
With over 45/pb of 7 TeV pp collisions recorded, the ATLAS Standard Model physics program is well under way. These proceedings survey the latest tests of the Standard Model at this unprecedented energy scale. An overview of recent ATLAS results is given. Measurements of the W charge asymmetry, di-boson production, and single top-quark production are highlighted.
A direct search for Higgs bosons produced via vector-boson fusion and subsequently decaying into invisible particles is reported. The analysis uses 139 $\text{fb}^{-1}$ of $pp$ collision data at a centre-of-mass energy of $\sqrt{s}$=13 $\text{TeV}$ recorded by the ATLAS detector at the LHC. The observed numbers of events are found to be in agreement with the background expectation from Standard Model processes. For a scalar Higgs boson with a mass of 125 $\text{GeV}$ and a Standard Model production cross section, an observed upper limit of $0.145$ is placed on the branching fraction of its dec…
Results of a search for new particles decaying into eight or more jets and moderate missing transverse momentum are presented. The analysis uses 139 fb$^{-1}$ of proton$-$proton collision data at $\sqrt{s} = 13$ TeV collected by the ATLAS experiment at the Large Hadron Collider between 2015 and 2018. The selection rejects events containing isolated electrons or muons, and makes requirements according to the number of $b$-tagged jets and the scalar sum of masses of large-radius jets. The search extends previous analyses both in using a larger dataset and by employing improved jet and missing tr…
An overview of the analyses that led to the observation of the Higgs boson production in association with a top quark pair ($t\bar t H$) with the ATLAS experiment is given. Up to 80 fb$^{-1}$ of proton-proton collision data recorded by the ATLAS experiment at a center-of-mass energy of $\sqrt{s} = 13$ TeV at the Large Hadron Collider (LHC) have been used to achieve this major milestone.
A search for a pair of neutral, scalar bosons with each decaying into two $W$ bosons is presented using 36.1 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. This search uses three production models: non-resonant and resonant Higgs boson pair production and resonant production of a pair of heavy scalar particles. Three final states, classified by the number of leptons, are analysed: two same-sign leptons, three leptons, and four leptons. No significant excess over the expected Standard Model background…
New measurements are presented from proton-proton collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC. Minimum bias distributions are measured in distinct phase-space regions and compared with Monte Carlo model predictions. Activity in the underlying event is measured with respect to the track with the highest tranverse momentum in the event. Angular correlations between charged particles are studied to provide model-sensitive measurements.
The search for Higgs boson pair ($HH$) production is at the core of the ATLAS experimental program, as it probes the Brout-Englert-Higgs mechanism, as well as new physics beyond the Standard Model. Based on the proton-proton collision data recorded by the ATLAS experiment at CERN's Large Hadron Collider in 2015 and 2016, three public results on the search for $HH \to bbbb$, $HH \to bbγγ$ and $HH \to WWγγ$ were recently released and are summarised in these proceedings.
We summarize the analysis of high-pT jets in early pp collisions recorded with the ATLAS detector. Two searches for new physics are presented: One for dijet resonances, and one for quark contact interactions. The first search sets the most stringent current limit on the mass of a hypothetical excited quark.
Measurement of the Higgs boson mass in the $H \rightarrow ZZ^* \rightarrow 4\ell$ decay channel using 139 fb$^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collisions recorded by the ATLAS detector at the LHC
First ATLAS searches for signals of Supersymmetry in proton-proton collisions at the LHC are presented. These searches are performed in various channels containing different lepton and jet multiplicities in the final states; the full data sample recorded in the 2010 LHC run, corresponding to an integrated luminosity of 35 $\rm{pb}^{-1}$, has been analysed. The limits on squarks and gluinos are the most stringent to date.
After the first LHC long shutdown with upgrades to the machine and the detectors, since 2015 the ATLAS experiment recorded more than 30 fb-1 of integrated luminosity of pp collision data at 13 TeV centre- of-mass energy. The data collected to date, the detector and physics performance, and measurements of Standard Model processes are reviewed briefly before summarising the latest ATLAS results in the Brout- Englert-Higgs sector, where substantial progress has been made since the discovery. Searches for physics phenomena beyond the Standard Model are also summarized. These proceedings reflect o…
The ATLAS detector has been used to search for high mass ee or mumu resonances, such as new heavy neutral gauge bosons. Over 1 fb^{-1} of proton-proton collisions at s = 7 TeV recorded by the ATLAS experiment are used to search for a high mass state decaying to dilepton pairs. No excess over Standard Model expectations is observed, and limits are placed on benchmark models predicting spin-1 and spin-2 resonances.
The results on W and Z boson properties by both ATLAS and CMS (except mass) are presented in this document. The inclusive W and Z boson cross section production, the W charge asymmetry, the differential production as a function of the boson rapidity and transverse momentum, the W polarization and the sinus of the weak angle are shown in this document. The studies included are based on LHC collisions at ps = 7 TeV, recorded during 2010 and 2011.
This paper presents measurements of distributions of charged particles which are produced in proton--proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV 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 $160 \mathrm{μb^{-1}}$ was used. A minimum-bias trigger was utilised to select a data sample of more than 9 million collision events. The multiplicity, pseudorapidity, and transverse momentum distributions of charged particles are sh…
The searches for supersymmetric and beyond Standard Model Higgs boson with the ATLAS detector are presented. The results are based on integrated luminosity of 35 pb$^{-1}$ to 1.6 fb$^{-1}$ of proton-proton collision data recorded at a centre-of-mass energy of 7 TeV at LHC. No signal is observed in any of the investigated channel and exclusion limits on production cross-sections are given as function of Higgs boson mass and of minimal supersymmetric model parameters.
R-parity violation in supersymmetry gives rise to many unique experimental signatures. We describe searches with the ATLAS detector for supersymmetry with R-parity violating decays. Examples include searches for resonant sneutrino decays to an electron and a muon, and displaced vertices arising from the late decays of heavy objects with a muon in the final state. The most recent results on these channels are presented based on data recorded with the ATLAS detector in 7TeV proton-proton collisions at the CERN Large Hadron Collider in 2010 and 2011.
Measurements of the production cross section of top-quark pairs ($t\bar t$) in $pp$ collisions at $\sqrt{s}$ = 7 TeV are presented using 35 \ipb\ of data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in the single lepton (electron or muon) and dilepton topologies with multi-jets, and large missing transverse energy. The result is $σ_{t\bar t} = 180 \pm 9\,\mathrm{(stat.)} \pm15 \,\mathrm{(syst.)} \pm 6 \,\mathrm{(lumi.)\,pb}$, which agrees with the Standard Model prediction.
A blind analysis searching for the decay Bs0 -> mumu has been performed using proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the LHC. With an integrated luminosity of 2.4 fb^(-1) no excess of events over the background expectation is found and an upper limit is set on the branching fraction BR(Bs0 -> mu mu) < 2.2 (1.9) x10^(-8) at 95% (90%) confidence level.
The ALFA subdetector is designed to measure elastic proton-proton scattering from which the total cross section and $ρ$-parameter are determined. In 2016, special runs at a center-of-mass energy of $\sqrt{s} = 13$\,TeV and with $β^\star = 2.5$\,km were recorded.
The latest results are presented of the search for new physics in inclusive dijet events recorded with the ATLAS detector. The search for resonances in the dijet mass spectrum is updated with 0.81 fb^-1 of 2011 data. The latest analysis of dijet angular distributions, with 36 pb^-1 of 2010 data, is also presented. In-depth information is provided about the model-independent search for resonances. Limits are provided for excited quarks, axigluons, scalar color octets, and to Gaussian signals that allow to set approximate limits in a model-independent way.
Summary of first ATLAS results is given for the Standard Model Higgs boson in the mass range 110 < mH < 130 GeV, when produced in association with a W/Z boson and decaying to a pair of b-quarks. No evidence for the Higgs boson production is observed in a dataset of proton-proton collisions at a center of mass energy of 7 TeV and corresponding to 1.04 fb-1 of integrated luminosity, recorded by the ATLAS experiment at the LHC in 2011. Upper limits on Higgs boson production cross sections for the channels considered are presented.
Recent analyses of top quark production in association with vector bosons are summarized, representing the most precise inclusive and differential cross section measurements of these processes to date. Proton-proton collision data at a center-of-mass energy of $\sqrt{s}=13$ TeV, recorded by the ATLAS and CMS detectors at the LHC are analyzed, corresponding to an integrated luminosity of up to 139 fb$^{-1}$ for each experiment. Comparisons with theory calculations are performed and overall good agreement with standard model predictions are obtained.
We present the measurement of the production cross section for top quark pair ($t\bar{t}$) in pp collisions at $\sqrt{s}$ = 7 TeV using the data recorded with the ATLAS detector at the Large Hadron Collider (LHC). Events are selected in single lepton (electron or muon) and dilepton ($ee$, $μμ$, $eμ$) topologies with multi-jets, and large missing transverse energy (MET). The combined result from these measurements is $σ_{t\bar{t}}$ = $176 \pm 5 \mathrm{(stat.)} ^{+13}_{-10}\mathrm{(syst.)} \pm 7 \mathrm{(lumi.)} \mathrm{pb}$, which is in good agreement with the Standard Model prediction.
The possibility to determine the recorded integrated luminosity via the measurements of the W and Z boson production cross-sections with the ATLAS detector is discussed. The current results based on 2010 data are briefly summarized. Special attention is drawn to theoretical uncertainties of the measurement. The latter give a large contribution to the systematic uncertainties of the measurements. An outlook on the expected precision of an analysis based on 1fb-1 is given and the implications on a possible luminosity determination are discussed.
The ATLAS detector at the LHC recorded 0.49nb$^{-1}$ of Pb+Pb collisions and 25pb$^{-1}$ of $pp$ collisions, both at the center-of-mass energy 5.02TeV per nucleon pair. Recently, ATLAS also recorded 3$μ$b$^{-1}$ of Xe+Xe collisions at the center-of-mass energy 5.44TeV, which provides a new opportunity to study the system-size dependence of the charged-hadron production in heavy-ion collisions. The large acceptance of the ATLAS detector allows to measure the spectra of charged hadrons in a wide range of pseudorapidity and transverse momentum. The nuclear modification factors $R_\mathrm{AA}$ are…
Weak scale supersymmetry is one of the best motivated and studied Standard Model extensions. It predicts the existence of new heavy coloured particles called squarks and gluinos which are the supersymmetric partners of the quarks and gluons, respectively. The poster summarises results on inclusive searches for supersymmetric squarks and gluinos in events containing jets and missing transverse momentum without leptons. The searches use the full data sample recorded in 2012 at $\sqrt{s}$=8~TeV centre-of-mass energy by the ATLAS experiment at the LHC.
Recent measurements of Higgs boson cross-section and properties are presented using up to $139~\text{fb}^{-1}$ of proton-proton collision data delivered by the Large Hadron Collider at $\sqrt{s}~=~13~\text{TeV}$ and recorded by the ATLAS and CMS detectors. Three measurements are discussed. The first is the measurement of Higgs boson production with sizeable transverse momentum decaying to a $b\bar{b}$ pair. The remaining two measurements exploit the $H \rightarrow WW^*$ decay channel in various production modes: gluon fusion, vector boson fusion, and production in association with a $W$ or $Z$…
ATLAS has made several measurements of the top quark mass using proton-proton collision data recorded in 2012 at the LHC with a centre-of-mass energy of 8 TeV. Those summarised here include an indirect determination of the top quark pole mass from lepton differential cross-sections; previous direct measurements of the top quark mass in the $t\bar{t}\to\textrm{dilepton}$ and $t\bar{t}\to\textrm{all-jets}$ decay channels as well as in the $t$-channel of single-top-quark production; and lastly, the new direct measurement of the top quark mass in the $t\bar{t}\to\textrm{lepton+jets}$ decay channel…
We report on the search for the Standard Model Higgs boson decaying into two photons based on proton-proton collision data with a center-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. The dataset has an integrated luminosity of about 1.08 fb-1. The expected cross section exclusion at 95% confidence level varies between 2.0 and 5.8 times the Standard Model cross section over the diphoton mass range 110 - 150 GeV. The maximum deviations from the background-only expectation are consistent with statistical fluctuations.
A search for the Standard Model Higgs boson in the two photon decay channel is reported, using 1.08 fb^-1 of proton-proton collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS detector. No significant excess is observed in the investigated mass range of 110-150 GeV. Upper limits on the cross-section times branching ratio of between 2.0 and 5.8 times the Standard Model prediction are derived for this mass range.
A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb-1 to 4.8 fb-1. Higgs boson decays into oppositely-charged muon or tau lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusio…
A search for new phenomena in events featuring a high energy jet and large missing transverse momentum in proton-proton collisions at sqrt(s) = 7 TeV is presented using a dataset corresponding to an integrated luminosity of 33 pb^-1 recorded with the ATLAS detector at the Large Hadron Collider. The number of observed events is consistent with the Standard Model prediction and this result is interpreted in terms of limits on a model of Large Extra Dimensions.
Many supersymmetry models feature gauginos and also sleptons with masses below a few hundred GeV. These can give rise to direct pair production rates at the LHC that can be observed in the data sample recorded by the ATLAS detector. The talk presents results from searches for gaugino and slepton pair production in final states with leptons.
The cross section of the $t\bar{t}Z$~and $t\bar{t}W$~processes are measured in a simultaneous fit using 36.1 $\text{fb}^{-1}$ of of proton--proton collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS experiment at the LHC. In addition, a fit is performed in the 4$\ell$ channel only, resulting in a cross section of $σ_{t\bar{t}Z} = 1.07 \pm 0.26 \,\text{pb}$. This result is consistent with the combined fit and agrees with the prediction by the Standard Model.
The cross section of the $t\bar{t}Z$ and $t\bar{t}W$ processes are measured in a simultaneous fit using 36.1 $\text{fb}^{-1}$ of proton-proton collisions at a centre of mass energy of $\sqrt{s}=13$ TeV recorded by the ATLAS detector at the LHC. The result is found to be $σ_{t\bar{t}Z} = 0.95 \pm 0.08 \text{ (stat.)} \pm 0.10 \text{ (syst.)}\,\text{pb}$ and $σ_{t\bar{t}W} = 0.87 \pm 0.13 \text{ (stat.)} \pm 0.14 \text{ (syst.)}\,\text{pb}$ and compatible with the Standard Model.
The ATLAS experiment identifies and reconstructs muons with two high precision tracking systems, the Inner Detector and the Muon Spectrometer, which provide independent measurements of the muon momentum. This paper summarizes the performance of the combined muon reconstruction in terms of reconstruction efficiency, momentum scale and resolution. Data-driven techniques are used to derive corrections to be applied to the simulation in order to reproduce the reconstruction efficiency, momentum scale and resolution observed in experimental data, and to assess systematic uncertainties on these quan…
Results from the latest searches for pair-produced scalar leptoquarks using 36.1 $\text{fb}^{-1}$ of $pp$-collision data recorded by the ATLAS detector at $\sqrt{s}$ = 13 TeV were presented. No statistically significant excess of data over Standard Model prediction is observed. The observed limits on first- (second-) generation leptoquark masses are excluded up to 1400 (1560) GeV in the minimal Buchmüller-Rückl-Wyler model, assuming a leptoquark decay branching ratio of 100% into a charged lepton and a quark. Third generation leptoquark masses are excluded up to 1000 GeV at the highest and low…
Searches for the production of electroweak supersymmetric particles decaying into final states with exactly two isolated, oppositely-charged leptons (electrons, muons), no reconstructed jets and missing transverse momentum are performed using 20.3 fb-1 of 2012 proton-proton collision data at sqrt(s) = 8 TeV recorded with the general purpose detector ATLAS at the Large Hardon Collider. In the absence of any significant excess with respect to the prediction from Standard Model processes, the results are interpreted in the framework of simplified Supersymmetry models.
A search for new spin-0 resonances decaying into two photons in the ATLAS experiment at the LHC is described. The analysis is based on $pp$ collision data at $\sqrt{s}$=13 TeV corresponding to integrated luminosities of 3.2/fb and 12.2/fb recorded in 2015 and 2016, respectively. A deviation from the Standard Model background-only hypothesis corresponding to 3.4 standard deviations is observed in the 2015 data for a resonance mass hypothesis of 730 GeV. No significant excess at such mass over the background expectation is observed in the 2016 data. Limits on the production cross section times b…
The investigation of the mechanism responsible for electroweak symmetry breaking is one of the most important tasks of the scientific program of the Large Hadron Collider. The experimental results on the search of the Standard Model Higgs boson with 1 to 2 fb^-1 of proton proton collision data at sqrt s=7 TeV recorded by the ATLAS detector are presented and discussed. No significant excess of events is found with respect to the expectations from Standard Model processes, and the production of a Higgs boson is excluded at 95% Confidence Level for the mass regions 144-232, 256-282 and 296-466 Ge…
Measurements of the branching ratios of top quark decays into leptons and jets using events with $t \overline{t}$ (top antitop) pairs are reported. Events were recorded with the ATLAS detector at the LHC in pp collisions at a center-of-mass energy of 7 TeV. The collected data sample corresponds to an integrated luminosity of 4.6 ${\mathrm{fb}}^{-1}$. The measured top quark branching ratios agree with the Standard Model predictions within the measurement uncertainties of a few percent.
The production cross-section of B+ mesons is measured as a function of transverse momentum pT and rapidity y in proton--proton collisions at center-of-mass energy sqrt(s) = 7 TeV, using 2.4 fb-1 of data recorded with the ATLAS detector at the Large Hadron Collider. The differential production cross-sections, determined in the range 9<pT<120 GeV and y<2.25, are compared to next-to-leading-order theoretical predictions.
During 2015 the ATLAS experiment recorded 3.8 fb$^{-1}$ of proton--proton collision data at a centre-of-mass energy of 13 TeV. The ATLAS trigger system is a crucial component of the experiment, responsible for selecting events of interest at a recording rate of approximately 1 kHz from up to 40 MHz of collisions. This paper presents a short overview of the changes to the trigger and data acquisition systems during the first long shutdown of the LHC and shows the performance of the trigger system and its components based on the 2015 proton--proton collision data.
The production of events with multiple high transverse momentum particles including charged leptons and jets is measured, using 1.04 fb-1 of proton-proton collision data recorded by the ATLAS detector during the first half of 2011 at sqrt(s) = 7 TeV. No excess beyond Standard Model expectations is observed, and upper limits on the fiducial cross sections for non-Standard Model production of these final states are set. Using models for string ball and black hole production and decay, exclusion contours are determined as a function of mass threshold and the fundamental gravity scale.
The top quark mass has been measured using the template method in the top antitop -> lepton + jets channel based on data recorded in 2011 with the ATLAS detector at the LHC. The data were taken at a proton-proton centre-of-mass energy of sqrt(s) = 7 TeV and correspond to an integrated luminosity of 1.04/fb. The analyses in the electron + jets and muon + jets decay channels yield consistent results. The top quark mass is measured to be m_top = 174.5 +/- 0.6_stat +/- 2.3_syst GeV.
