0000000000028438
AUTHOR
Gerardo Vasquez
Measurement of the Soft-Drop Jet Mass in pp Collisions at s=13 TeV with the ATLAS Detector
Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by the ...
Search for squarks and gluinos in final states with jets and missing transverse momentum using 36 fb−1 of s=13 TeV pp collision data with the ATLAS detector
A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented ...
Comparison of Fragmentation Functions for Jets Dominated by Light Quarks and Gluons from pp and Pb+Pb Collisions in ATLAS
Charged-particle fragmentation functions for jets azimuthally balanced by a high-transverse-momentum, prompt, isolated photon are measured in 25 pb^{-1} of pp and 0.49 nb^{-1} of Pb+Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The measurements are compared to predictions of Monte Carlo generators and to measurements of inclusively selected jets. In pp collisions, a different jet fragmentation function in photon-tagged events from that in inclusive jet events arises from the difference in fragmentation between light quarks and gluons. The ratios of the fragmentation functions in Pb+Pb events to that in pp events are used to e…
Probing the Quantum Interference between Singly and Doubly Resonant Top-Quark Production in pp Collisions at s=13 TeV with the ATLAS Detector
This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μμ, or eμ) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb^{-1} of proton-proton collision data taken at sqrt[s]=13 TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are signifi…
Search for anomalous electroweak production of WW/WZ in association with a high-mass dijet system in pp collisions at s=8 TeV with the ATLAS detector
A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to $20.2$ fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ collisions, and were collected in 2012 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of $WW$ or $WZ$ boson pairs accompanied by a high-mass dijet system, with one $W$ decaying leptonically, and a $W$ or $Z$ decaying hadronically. The hadronically decaying $W/Z$ is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters $\alpha_4$ and $\alpha_5$ are set by fit…
Search for top squarks decaying to tau sleptons in pp collisions at s=13 TeV with the ATLAS detector
A search for direct pair production of top squarks in final states with two tau leptons, b-jets, and missing transverse momentum is presented. The analysis is based on proton-proton collision data ...
Observation of electroweak W±Z boson pair production in association with two jets in pp collisions at s=13 TeV with the ATLAS detector
An observation of electroweak W±Z production in association with two jets in proton–proton collisions is presented. The data collected by the ATLAS detector at the Large Hadron Collider in 2015 and 2016 at a centre-of-mass energy of s=13 TeV are used, corresponding to an integrated luminosity of 36.1fb−1 . Events containing three identified leptons, either electrons or muons, and two jets are selected. The electroweak production of W±Z bosons in association with two jets is measured with an observed significance of 5.3 standard deviations. A fiducial cross-section for electroweak production including interference effects and for a single leptonic decay mode is measured to be σWZjj−EW=0.57−0…
Search for dark matter in association with a Higgs boson decaying to two photons at s=13 TeV with the ATLAS detector
A search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated lumino ...
Search for flavor-changing neutral currents in top quark decays t→Hc and t→Hu in multilepton final states in proton-proton collisions at s=13 TeV with the ATLAS detector
Flavor-changing neutral currents are not present in the Standard Model at tree level and are suppressed in loop processes by the unitarity of the Cabibbo-Kobayashi-Maskawa matrix; the corresponding ...
Search for light resonances decaying to boosted quark pairs and produced in association with a photon or a jet in proton–proton collisions at s=13TeV with the ATLAS detector
This Letter presents a search for new light resonances decaying to pairs of quarks and produced in association with a high- pT photon or jet. The dataset consists of proton–proton collisions with an integrated luminosity of 36.1 fb −1 at a centre-of-mass energy of s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Resonance candidates are identified as massive large-radius jets with substructure consistent with a particle decaying into a quark pair. The mass spectrum of the candidates is examined for local excesses above background. No evidence of a new resonance is observed in the data, which are used to exclude the production of a lepto-phobic axial-vector Z′ boson.
Search for a Structure in the Bs0π± Invariant Mass Spectrum with the ATLAS Experiment
A search for the narrow structure, X(5568), reported by the D0 Collaboration in the decay sequence X→B_{s}^{0}π^{±}, B_{s}^{0}→J/ψϕ, is presented. The analysis is based on a data sample recorded with the ATLAS detector at the LHC corresponding to 4.9 fb^{-1} of pp collisions at 7 TeV and 19.5 fb^{-1} at 8 TeV. No significant signal was found. Upper limits on the number of signal events, with properties corresponding to those reported by D0, and on the X production rate relative to B_{s}^{0} mesons, ρ_{X}, were determined at 95% confidence level. The results are N(X)<382 and ρ_{X}<0.015 for B_{s}^{0} mesons with transverse momenta above 10 GeV, and N(X)<356 and ρ_{X}<0.016 for transverse m…
Search for Resonant and Nonresonant Higgs Boson Pair Production in the bb¯τ+τ− Decay Channel in pp Collisions at s=13 TeV with the ATLAS Detector
A search for resonant and nonresonant pair production of Higgs bosons in the b (b) over bar tau(+)tau(-) final state is presented. The search uses 36.1 fb(-1) of pp collision data with root s = 13 ...
Search for the Production of a Long-Lived Neutral Particle Decaying within the ATLAS Hadronic Calorimeter in Association with a Z Boson from pp Collisions at s=13 TeV
This Letter presents a search for the production of a long-lived neutral particle (Zd) decaying within the ATLAS hadronic calorimeter, in association with a standard model (SM) Z boson produced via an intermediate scalar boson, where Z→+ (=e, μ). The data used were collected by the ATLAS detector during 2015 and 2016 pp collisions with a center-of-mass energy of s=13 TeV at the Large Hadron Collider and correspond to an integrated luminosity of 36.1±0.8 fb-1. No significant excess of events is observed above the expected background. Limits on the production cross section of the scalar boson times its decay branching fraction into the long-lived neutral particle are derived as a function of …
Search for resonances in the mass distribution of jet pairs with one or two jets identified as b-jets in proton–proton collisions at s=13 TeV with the ATLAS detector
Searches for 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. No evidence of anomalous phenomena is observed in the data, which are used to exclude, at 95% credibility level, excited $b^{*}$ quarks with masses from 1.1 TeV to 2.1 TeV and leptophobic $Z'$ bosons with masses from 1.1 TeV to 1.5 TeV. Contributions of a Gaussian signal shape with effective cross sections ranging from approximately 0.4 to 0.001 pb are also excluded in the mass…
Search for heavy resonances decaying to a photon and a hadronically decaying Z/W/H boson in pp collisions at s=13 TeV with the ATLAS detector
This Letter presents a search for the production of new heavy resonances decaying into a Higgs boson and a photon using proton-proton collision data at √ s = 13 TeV collected by the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 139 fb − 1 . The analysis is performed by reconstructing hadronically decaying Higgs boson ( H → b ¯ b ) candidates as single large-radius jets. A novel algorithm using information about the jet constituents in the center-of-mass frame of the jet is implemented to identify the two b quarks in the single jet. No significant excess of events is observed above the expected background. Upper limits are set on the production cross-s…
Search for Higgs bosons produced via vector-boson fusion and decaying into bottom quark pairs in s=13 TeV pp collisions with the ATLAS detector
A search for the b (b) over bar decay of the Standard Model Higgs boson produced through vector-boson fusion is presented. Three mutually exclusive channels are considered: two all-hadronic channel ...
Search for new phenomena in dijet events using 37 fb−1 of pp collision data collected at s=13 TeV with the ATLAS detector
Dijet events are studied in the proton-proton collision dataset recorded at root s = 13 TeV with the ATLAS detector at the Large Hadron Collider in 2015 and 2016, corresponding to integrated lumino ...
Measurement of the suppression and azimuthal anisotropy of muons from heavy-flavor decays in Pb+Pb collisions at sNN=2.76 TeV with the ATLAS detector
ATLAS measurements of the production of muons from heavy-flavor decays in root s(NN) = 2.76 TeV Pb+Pb collisions and root s = 2.76 TeV pp collisions at the LHC are presented. Integrated luminositie ...
Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at s=13 TeV with the ATLAS Detector
A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T -> Zt/Wb/Ht, B -> Zb/Wt/Hb) is performed using 36.1 fb(-1) of pp ...
Study of ordered hadron chains with the ATLAS detector
The analysis of the momentum difference between charged hadrons in high-energy proton-proton collisions is performed in order to study coherent particle production. The observed correlation pattern agrees with a model of a helical QCD string fragmenting into a chain of ground-state hadrons. A threshold momentum difference in the production of adjacent pairs of charged hadrons is observed, in agreement with model predictions. The presence of low-mass hadron chains also explains the emergence of charge-combination-dependent two-particle correlations commonly attributed to Bose-Einstein interference. The data sample consists of 190 μb-1 of minimum-bias events collected with proton-proton colli…
Search for supersymmetry in events with four or more leptons in s=13 TeV pp collisions with ATLAS
Results from a search for supersymmetry in events with four or more charged leptons (electrons, muons and taus) are presented. The analysis uses a data sample corresponding to 36.1 fb-1 of proton-proton collisions delivered by the Large Hadron Collider at s=13 TeV and recorded by the ATLAS detector. Four-lepton signal regions with up to two hadronically decaying taus are designed to target a range of supersymmetric scenarios that can be either enriched in or depleted of events involving the production and decay of a Z boson. Data yields are consistent with Standard Model expectations and results are used to set upper limits on the event yields from processes beyond the Standard Model. Exclu…
Observation of Centrality-Dependent Acoplanarity for Muon Pairs Produced via Two-Photon Scattering in Pb+Pb Collisions at sNN=5.02 TeV with the ATLAS Detector
This Letter presents a measurement of γγ→μ^{+}μ^{-} production in Pb+Pb collisions recorded by the ATLAS detector at the Large Hadron Collider at sqrt[s_{NN}]=5.02 TeV with an integrated luminosity of 0.49 nb^{-1}. The azimuthal angle and transverse momentum correlations between the muons are measured as a function of collision centrality. The muon pairs are produced from γγ through the interaction of the large electromagnetic fields of the nuclei. The contribution from background sources of muon pairs is removed using a template fit method. In peripheral collisions, the muons exhibit a strong back-to-back correlation consistent with previous measurements of muon pair production in ultrap…
Search for photonic signatures of gauge-mediated supersymmetry in 8TeV pp collisions with the ATLAS detector
A search is presented for photonic signatures motivated by generalized models of gauge-mediated supersymmetry breaking. This search makes use of 20.3 fb[superscript −1] of proton-proton collision data at √s = 8 TeV recorded by the ATLAS detector at the LHC, and explores models dominated by both strong and electroweak production of supersymmetric partner states. Four experimental signatures incorporating an isolated photon and significant missing transverse momentum are explored. These signatures include events with an additional photon, lepton, b-quark jet, or jet activity not associated with any specific underlying quark flavor. No significant excess of events is observed above the Stand…
Search for invisible Higgs boson decays in vector boson fusion at s=13TeV with the ATLAS detector
We report a search for Higgs bosons that are produced via vector boson fusion and subsequently decay into invisible particles. The experimental signature is an energetic jet pair with invariant mass of O(1)TeV and O(100)GeV missing transverse momentum. The analysis uses 36.1 fb −1 of pp collision data at s=13TeV recorded by the ATLAS detector at the LHC. In the signal region the 2252 observed events are consistent with the background estimation. Assuming a 125GeV scalar particle with Standard Model cross sections, the upper limit on the branching fraction of the Higgs boson decay into invisible particles is 0.37 at 95% confidence level where 0.28 was expected. This limit is interpreted in H…
Measurement of the tt¯ production cross section in the τ+jets final state in pp collisions at s=8 TeV using the ATLAS detector
A measurement of the inclusive pp -> t (t) over bar + X production cross section in the tau + jets final state using only the hadronic decays of the tau lepton is presented. The measurement is p ...
Observation of Electroweak Production of a Same-Sign W Boson Pair in Association with Two Jets in pp Collisions at s=13 TeV with the ATLAS Detector
This Letter presents the observation and measurement of electroweak production of a same-sign W boson pair in association with two jets using 36.1 fb^{-1} of proton-proton collision data recorded at a center-of-mass energy of sqrt[s]=13 TeV by the ATLAS detector at the Large Hadron Collider. The analysis is performed in the detector fiducial phase-space region, defined by the presence of two same-sign leptons, electron or muon, and at least two jets with a large invariant mass and rapidity difference. A total of 122 candidate events are observed for a background expectation of 69±7 events, corresponding to an observed signal significance of 6.5 standard deviations. The measured fiducial s…
Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36 fb−1 of proton-proton collision data at s=13 TeV with the ATLAS detector
Searches for new heavy resonances decaying into different pairings of W, Z, or Higgs bosons, as well as dirffiffiffiectly into leptons, are presented using a data sample corresponding to 36.1 fb(-1 ...
Measurements of tt¯ differential cross-sections of highly boosted top quarks decaying to all-hadronic final states in pp collisions at s=13 TeV using the ATLAS detector
Measurements are made of differential cross-sections of highly boosted pair-produced top quarks as a function of top-quark and t (t) over bar system kinematic observables using proton-proton collis ...
Two-particle azimuthal correlations in photonuclear ultraperipheral Pb+Pb collisions at 5.02 TeV with ATLAS
We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina, YerPhI, Armenia, ARC, Australia, BMWFW and FWF, Austria, ANAS, Azerbaijan, SSTC, Belarus, CNPq and FAPESP, Brazil, NSERC, NRC, and CFI, Canada, CERN and ANID, Chile, CAS, MOST, and NSFC, China, COLCIENCIAS, Colombia, MSMT CR, MPO CR, and VSC CR, Czech Republic, DNRF and DNSRC, Denmark, IN2P3-CNRS and CEA-DRF/IRFU, France, SRNSFG, Georgia, BMBF, HGF, and MPG, Germany, GSRT, Greece, RGC and Hong Kong SAR, China, ISF and Benoziyo Center, Israel, INFN, Italy, MEXT and JSPS, Japan, CNR…
Measurement of prompt photon production in sNN=8.16 TeV p + Pb collisions with ATLAS
The inclusive production rates of isolated, prompt photons in p+Pb collisions at sNN=8.16 TeV are studied with the ATLAS detector at the Large Hadron Collider using a dataset with an integrated luminosity of 165 nb −1 recorded in 2016. The cross-section and nuclear modification factor RpPb are measured as a function of photon transverse energy from 20 GeV to 550 GeV and in three nucleon–nucleon centre-of-mass pseudorapidity regions, (−2.83,−2.02) , (−1.84,0.91) , and (1.09,1.90) . The cross-section and RpPb values are compared with the results of a next-to-leading-order perturbative QCD calculation, with and without nuclear parton distribution function modifications, and with expectations b…
Measurement of the production cross section for a Higgs boson in association with a vector boson in the H → WW⁎ → ℓνℓν channel in pp collisions at s=13 TeV with the ATLAS detector
A measurement of the Higgs boson production cross sections via associated WH and ZH production using H -> WW* -> l nu l nu decays, where l stands for either an electron or a muon, is presente ...
Search for the Decay of the Higgs Boson to Charm Quarks with the ATLAS Experiment
A direct search for the standard model Higgs boson decaying to a pair of charm quarks is presented. Associated production of the Higgs and Z bosons, in the decay mode ZH→ℓ+ℓ−c¯c is studied. A data set with an integrated luminosity of 36.1 fb−1 of pp collisions at √s=13TeV recorded by the ATLAS experiment at the LHC is used. The H→c¯c signature is identified using charm-tagging algorithms. The observed (expected) upper limit on σ(pp→ZH)×B(H→c¯c) is 2.7 (3.9+2.1−1.1) pb at the 95% confidence level for a Higgs boson mass of 125 GeV, while the standard model value is 26 fb.
Study of the material of the ATLAS inner detector for Run 2 of the LHC
The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable B-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity root s = 13 TeV pp collision sample corresponding to around 2.0 nb(-1) collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic in…
Femtoscopy with identified charged pions in proton-lead collisions at sNN=5.02 TeV with ATLAS
Bose-Einstein correlations between identified charged pions are measured for $p$+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV using data recorded by the ATLAS detector at the LHC corresponding to a total integrated luminosity of $28$ $\mathrm{nb}^{-1}$. Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum ($k_{\mathrm{T}}$) and rapidity ($y^{\star}_{\pi\pi}$) of the pair. Pairs are selected with a rapidity $-2 < y^{\star}_{\pi\pi} < 1$ and with an average transverse momentum $0.1 < k_{\mathrm{T}} <…
Measurements of Higgs boson properties in the diphoton decay channel with 36 fb−1 of pp collision data at s=13 TeV with the ATLAS detector
Properties of the Higgs boson are measured in the two-photon final state using 36.1 fb-1 of proton? proton collision data recorded at ffiffi √s = 13 TeV by the ATLAS experiment at the Large Hadron Collider. Cross-section measurements for the production of a Higgs boson through gluon-gluon fusion, vectorboson fusion, and in association with a vector boson or a top-quark pair are reported. The signal strength, defined as the ratio of the observed to the expected signal yield, is measured for each of these production processes as well as inclusively. The global signal strength measurement of 0.99 ± 0.14 improves on the precision of the ATLAS measurement at √s = 7 and 8 TeV by a factor of two. …