scholarly journals ATLAS b-jet identification performance and efficiency measurement with $$t{\bar{t}}$$ events in pp collisions at $$\sqrt{s}=13$$ TeV

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Hadron Collider ◽  
Efficiency Measurement ◽  
Atlas Collaboration ◽  
Centre Of Mass ◽  
Identification Performance ◽  
Momentum Range ◽  
Proton Proton ◽  
Proton Collisions ◽  
Proton Proton Collisions

AbstractThe algorithms used by the ATLAS Collaboration during Run 2 of the Large Hadron Collider to identify jets containing b-hadrons are presented. The performance of the algorithms is evaluated in the simulation and the efficiency with which these algorithms identify jets containing b-hadrons is measured in collision data. The measurement uses a likelihood-based method in a sample highly enriched in $$t{\bar{t}}$$tt¯ events. The topology of the $$t \rightarrow W b$$t→Wb decays is exploited to simultaneously measure both the jet flavour composition of the sample and the efficiency in a transverse momentum range from 20 to 600 GeV. The efficiency measurement is subsequently compared with that predicted by the simulation. The data used in this measurement, corresponding to a total integrated luminosity of 80.5 $$\hbox {fb}^{-1}$$fb-1, were collected in proton–proton collisions during the years 2015–2017 at a centre-of-mass energy $$\sqrt{s}=$$s= 13 TeV. By simultaneously extracting both the efficiency and jet flavour composition, this measurement significantly improves the precision compared to previous results, with uncertainties ranging from 1 to 8% depending on the jet transverse momentum.

scholarly journals HIGHLIGHTS FROM THE LHC

2013 ◽  
Vol 53 (A) ◽  
pp. 518-523
Author(s):  
Arno Straessner
Keyword(s):  
Large Hadron Collider ◽  
Standard Model ◽  
Hadron Collider ◽  
Centre Of Mass ◽  
Proton Proton ◽  
Exotic Particles ◽  
Proton Collisions ◽  
Total Luminosity ◽  
Future Data ◽  
Proton Proton Collisions

The Large Hadron Collider (LHC) and the two multi-purpose detectors, ATLAS and CMS, have been operated successfully at record centre-of-mass energies of 7 ÷ 8TeV. This paper presents the main physics results from proton–proton collisions based on a total luminosity of 2 × 5 fb<sup>−1</sup>. The most recent results from Standard Model measurements, Standard Model and MSSM Higgs searches, as well as searches for supersymmetric and exotic particles are reported. Prospects for ongoing and future data taking are presented.

scholarly journals Total, Elastic and Single Diffractive Cross Sections for LHC Energies

2017 ◽  
Vol 45 ◽  
pp. 1760062
Author(s):  
Mairon M. Machado ◽  
Magno V. T. Machado
Keyword(s):  
Cross Sections ◽  
Lower Energy ◽  
Atlas Collaboration ◽  
Centre Of Mass ◽  
Proton Proton ◽  
Energy Data ◽  
Proton Collisions ◽  
Proton Proton Collisions

In this contribution we provide predictions for total, elastic and single diffractive cross sections calculated for the proton-proton collisions at the LHC in centre-of-mass energies of 0.9, 7, 8 and 14 TeV. We consider the framework of the Miettinen-Pumplin model which correctly describes the lower energy data available by Fermilab-Tevatron. Our predictions are based on the fitted parameters of the model for the Tevatron measurements and for TOTEM-LHC measurements at 7 TeV. We extrapolate the results for the higher energies runs of LHC and provide predictions for them. We verify that those prediction are in agreement with the recent CERN-ATLAS Collaboration result.

scholarly journals Measurement of $$K_S^0$$ and $$\Lambda ^0$$ production in $$t \bar{t}$$ dileptonic events in pp collisions at $$\sqrt{s} =$$ 7 TeV with the ATLAS detector

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
O. Abdinov ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Final States ◽  
Centre Of Mass ◽  
Mass Energy ◽  
Proton Proton ◽  
Proton Collisions ◽  
Strange Particles ◽  
Proton Proton Collisions

AbstractMeasurements of $$K_S^0$$KS0 and $$\Lambda ^0$$Λ0 production in $$t\bar{t}$$tt¯ final states have been performed. They are based on a data sample with integrated luminosity of 4.6 $$\mathrm {fb}^{-1}$$fb-1 from proton–proton collisions at a centre-of-mass energy of 7 TeV, collected in 2011 with the ATLAS detector at the Large Hadron Collider. Neutral strange particles are separated into three classes, depending on whether they are contained in a jet, with or without a b-tag, or not associated with a selected jet. The aim is to look for differences in their main kinematic distributions. A comparison of data with several Monte Carlo simulations using different hadronisation and fragmentation schemes, colour reconnection models and different tunes for the underlying event has been made. The production of neutral strange particles in $$t\bar{t}$$tt¯ dileptonic events is found to be well described by current Monte Carlo models for $$K_S^0$$KS0 and $$\Lambda ^0$$Λ0 production within jets, but not for those produced outside jets.

scholarly journals Status of searches for electroweak-scale supersymmetry after LHC Run 2

2022 ◽  
Author(s):  
Wolfgang Adam ◽  
Iacopo Vivarelli
Keyword(s):  
Hadron Collider ◽  
General Purpose ◽  
Conclusive Evidence ◽  
Centre Of Mass ◽  
Mass Energy ◽  
Large Dataset ◽  
Proton Proton ◽  
Proton Collisions ◽  
Proton Proton Collisions ◽  
Second Period

The second period of datataking at the Large Hadron Collider (LHC) has provided a large dataset of proton–proton collisions that is unprecedented in terms of its centre-of-mass energy of 13 TeV and integrated luminosity of almost 140 fb[Formula: see text]. These data constitute a formidable laboratory for the search for new particles predicted by models of supersymmetry. The analysis activity is still ongoing, but a host of results on supersymmetry had already been released by the general purpose LHC experiments ATLAS and CMS. In this paper, we provide a map into this remarkable body of research, which spans a multitude of experimental signatures and phenomenological scenarios. In the absence of conclusive evidence for the production of supersymmetric particles we discuss the constraints obtained in the context of various models. We finish with a short outlook on the new opportunities for the next runs that will be provided by the upgrade of detectors and accelerator.

scholarly journals Measurement of the transverse momentum distribution of Drell–Yan lepton pairs in proton–proton collisions at $$\sqrt{s}=13\,$$TeV with the ATLAS detector

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Angular Variable ◽  
Centre Of Mass ◽  
Mass Energy ◽  
Lepton Pairs ◽  
Muon Pair ◽  
Full Spectrum ◽  
Proton Proton ◽  
Proton Collisions ◽  
Proton Proton Collisions

Abstract This paper describes precision measurements of the transverse momentum $$p_\mathrm {T}^{\ell \ell }$$pTℓℓ ($$\ell =e,\mu $$ℓ=e,μ) and of the angular variable $$\phi ^{*}_{\eta }$$ϕη∗ distributions of Drell–Yan lepton pairs in a mass range of 66–116 GeV. The analysis uses data from 36.1 fb$$^{-1}$$-1 of proton–proton collisions at a centre-of-mass energy of $$\sqrt{s}=13\,$$s=13TeV collected by the ATLAS experiment at the LHC in 2015 and 2016. Measurements in electron-pair and muon-pair final states are performed in the same fiducial volumes, corrected for detector effects, and combined. Compared to previous measurements in proton–proton collisions at $$\sqrt{s}=7$$s=7 and $$8\,$$8TeV, these new measurements probe perturbative QCD at a higher centre-of-mass energy with a different composition of initial states. They reach a precision of 0.2$$\%$$% for the normalized spectra at low values of $$p_\mathrm {T}^{\ell \ell }$$pTℓℓ. The data are compared with different QCD predictions, where it is found that predictions based on resummation approaches can describe the full spectrum within uncertainties.

scholarly journals A search for the decays of stopped long-lived particles at $$ \sqrt{\mathrm{s}} $$ = 13 TeV with the ATLAS detector

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
◽  
G. Aad ◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Branching Fraction ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Centre Of Mass ◽  
Proton Proton ◽  
Proton Collisions ◽  
Atlas Experiment ◽  
Using Data ◽  
Lower Limits ◽  
Proton Proton Collisions

Abstract A search for long-lived particles, which have come to rest within the ATLAS detector, is presented. The subsequent decays of these particles can produce high-momentum jets, resulting in large out-of-time energy deposits in the ATLAS calorimeters. These de- cays are detected using data collected during periods in the LHC bunch structure when collisions are absent. The analysed dataset is composed of events from proton-proton collisions produced by the Large Hadron Collider at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV and recorded by the ATLAS experiment during 2017 and 2018. The dataset used for this search corresponds to a total live time of 579 hours. The results of this search are used to derive lower limits on the mass of gluino R-hadrons, assuming a branching fraction $$ \mathcal{B}\left(\overset{\sim }{g}\to q\overline{q}{\chi}_1^0\right) $$ B g ~ → q q ¯ χ 1 0 = 100%, with masses of up to 1.4 TeV excluded for gluino lifetimes of 10−5 to 103 s.

scholarly journals Search for squarks and gluinos in final states with jets and missing transverse momentum using 139 fb−1 of $$ \sqrt{s} $$ = 13 TeV pp collision data with the ATLAS detector

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
G. Aad ◽  
◽  
B. Abbott ◽  
D. C. Abbott ◽  
A. Abed Abud ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Hadron Collider ◽  
Atlas Detector ◽  
Simplified Model ◽  
Supersymmetric Particle ◽  
Final States ◽  
Proton Proton ◽  
Missing Transverse Momentum ◽  
First And Second Generation ◽  
Proton Proton Collisions

Abstract A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded by the ATLAS experiment in proton-proton collisions at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. The results are interpreted in the context of various R-parity-conserving models where squarks and gluinos are produced in pairs or in association and a neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.30 TeV for a simplified model containing only a gluino and the lightest neutralino, assuming the latter is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.85 TeV are excluded if the lightest neutralino is massless. These limits extend substantially beyond the region of supersymmetric parameter space excluded previously by similar searches with the ATLAS detector.

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