Study and design of multiple or stacked detectors and a single fixed detector bimonthly progress report no. 1
Radiation detector design using X-ray diffraction camera and multichannel Geiger counter
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Surveyor ejecta detector model ML 256-1 and 185-1 and Surveyor ejecta detector ground support equipment model ML 260-1 Final engineering report
Engineering analyses on Surveyor lunar dust particle detector instrumentation, and ground support equipment
DETECTOR↗
Search for heavy Majorana or Dirac neutrinos and right-handed W gauge bosons in final states with two charged leptons and two jets at $\sqrt{s}=13 $ TeV with the ATLAS detector
A search for heavy right-handed Majorana or Dirac neutrinos NR and heavy right-handed gauge bosons WR is performed in events with a pair of energetic electrons or muons, with the same or opposite electric charge, and two energetic jets. The events are selected from pp collision data with an integrated luminosity of 36.1 fb -1 collected by the ATLAS detector at s√=13 TeV. No significant deviations from the Standard Model are observed. The results are interpreted within the theoretical framework of a left-right symmetric model and lower limits are set on masses in the heavy right-handed W boson and neutrino mass plane. The excluded region extends to m$_{R_R}$=4.7 TeV for both Majorana and Dirac N R neutrinos.
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Measurement of the Z(-> l(+)l(-))gamma production cross-section in pp collisions at root s=13 TeV with the ATLAS detector
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Search for new resonances in mass distributions of jet pairs using 139 fb(-1) of pp collisions at root s=13TeV with the ATLAS detector
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Measurement of isolated-photon plus two-jet production in pp collisions at root s=13 TeV with the ATLAS detector
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Search for top-quark decays t → Hq with 36 fb ₋1 of pp collision data at $\sqrt{s}$= 13 TeV with the ATLAS detector
A search for flavour-changing neutral current decays of a top quark into an up-type quark ( q = u, c ) and the Standard Model Higgs boson, t → Hq , is introduced. The search is based on a dataset of pp collisions at $\sqrt{s}$= 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb ₋1 . Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target the H→$b\bar{b}$ and H → τ + τ ₋ decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are used to separate the signal from the background, which is dominated by top-quark pair production. No significant excess of events above the background expectation is found, and 95% CL upper limits on the t → Hq branching ratios are derived. The combination of these searches with ATLAS searches in diphoton and multilepton final states yields observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 1.1 × 10 ₋3 (8.3 × 10 ₋4 ) and 1.2 × 10 ₋3 (8.3 × 10 ₋4 ), respectively. The corresponding combined observed (expected) upper limits on the |λ tcH | and |λ tuH | couplings are 0.064 (0.055) and 0.066 (0.055), respectively.
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Measurement of VH, H → $b\bar{b}$ production as a function of the vector-boson transverse momentum in 13 TeV pp collisions with the ATLAS detector
Cross-sections of associated production of a Higgs boson decaying into bottomquark pairs and an electroweak gauge boson, W or Z , decaying into leptons are measured as a function of the gauge boson transverse momentum. The measurements are performed in kinematic fiducial volumes defined in the ‘simplified template cross-section’ framework. The results are found using 79.8 fb ₋1 of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of 13 TeV. All measurements are found to be in agreement with the Standard Model predictions, and limits are set on the parameters of an effective Lagrangian sensitive to modifications of the Higgs boson couplings to the electroweak gauge bosons.
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Constraints on mediator-based dark matter and scalar dark energy models using $\sqrt{s}$ = 13 TeV pp collision data collected by the ATLAS detector
Constraints on selected mediator-based dark matter models and a scalar dark energy model using up to 37 fb ₋1 $\sqrt{s}$ = 13 TeV pp collision data collected by the ATLAS detector at the LHC during 2015-2016 are summarised in this paper. The conclusions of experimental searches in a variety of final states are interpreted in terms of a set of spin-1 and spin-0 single-mediator dark matter simplified models and a second set of models involving an extended Higgs sector plus an additional vector or pseudo-scalar mediator. The searches considered in this paper constrain spin-1 leptophobic and leptophilic mediators, spin-0 colour-neutral and colour-charged mediators and vector or pseudo-scalar mediators embedded in extended Higgs sector models. In this case, also $\sqrt{s}$ = 8 TeV pp collision data are used for the interpretation of the results. The results are also interpreted for the first time in terms of light scalar particles that could contribute to the accelerating expansion of the universe (dark energy).
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Search for single production of vector-like quarks decaying into Wb in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
A search for singly produced vector-like quarks Q , where Q can be either a T quark with charge +2/3 or a Y quark with charge ₋4/3, is performed in proton–proton collision data at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 36.1 fb ₋1 , recorded with the ATLAS detector at the LHC in 2015 and 2016. The analysis targets Q → Wb decays where the W boson decays leptonically. No crtical deviation from the expected Standard Model background is observed. Upper limits are set on the QWb coupling strength and the mixing between the Standard Model sector and a singlet T quark or a Y quark from a ( B, Y ) doublet or a ( T, B, Y ) triplet, taking into account the interference effects with the Standard Model background. The upper limits set on the mixing angle are as small as |sin θ L | = 0.18 for a singlet T quark of mass 800 GeV, |sin θ R | = 0.17 for a Y quark of mass 800 GeV in a ( B, Y ) doublet model and |sin θL| = 0.16 for a Y quark of mass 800 GeV in a ( T, B, Y ) triplet model. Within a ( B, Y ) doublet model, the limits set on the mixing parameter |sin θ R | are comparable with the exclusion limits from electroweak precision observables in the mass range between about 900 GeV and 1250 GeV.
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Measurement of the angular coefficients in Z-boson events using electron and muon pairs from data taken at $ \sqrt{s}=8 $ TeV with the ATLAS detector
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 A 0–7 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(α2s)) 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(α 2 s )) predictions is observed for A 0 – A 2 . In conclusion, evidence is found for non-zero A 5,6,7 , consistent with expectations.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Search for direct top squark pair production in events with a Higgs or Z boson, and missing transverse momentum in $ \sqrt{s}=13 $ TeV pp collisions with the ATLAS detector
A search for direct top squark pair production resulting in events with either a same-flavour opposite-sign dilepton pair with invariant mass compatible with a Z boson or a pair of jets compatible with a Standard Model (SM) Higgs boson (h) is presented. Requirements on the missing transverse momentum, together with additional selections on leptons, jets, jets identified as originating from b-quarks are imposed to target the other decay products of the top squark pair. The analysis is performed using proton-proton collision data at √s = 13 TeV collected with the ATLAS detector at the LHC in 2015–2016, corresponding to an integrated luminosity of 36.1 fb –1 . No excess is observed in the data with respect to the SM predictions. The results are interpreted in two sets of models. In the first set, direct production of pairs of lighter top squarks (t ~ 1 ) with long decay chains involving Z or Higgs bosons is considered. The second set includes direct pair production of the heavier top squark pairs (t ~ 2 ) decaying via t ~ 2 → Zt ~ 1 or t ~ 2 → ht ~ 1 . Here, the results exclude at 95% confidence level t ~ 2 and t ~ 1 masses up to about 800 GeV, extending the exclusion region of supersymmetric parameter space covered by previous LHC searches.
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Measurement of the k t splitting scales in Z → ℓℓ events in pp collisions at $\sqrt{s}=8 $ TeV with the ATLAS detector
A measurement of the splitting scales occuring in the k t jet-clustering algorithm is presented for final states containing a Z boson. The measurement is done using 20.2 fb -1 of proton-proton collision data collected at a centre-of-mass energy of s=8 TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on chargedparticle track information, which is measured with excellent precision in the p T region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables.
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Search for pair production of vector-like top quarks in events with one lepton, jets, and missing transverse momentum in $ \sqrt{s}=13 $ TeV $pp$ collisions with the ATLAS detector
The results of a search for vector-like top quarks using events with exactly one lepton, at least four jets, and large missing transverse momentum are reported. The search is optimised for pair production of vector-like top quarks in the Z(→vv) t + X decay channel. LHC pp collision data at a centre-of-mass energy of √s=13 TeV recorded by the ATLAS detector in 2015 and 2016 are used, corresponding to an integrated luminosity of 36.1 fb -1 . No significant excess over the Standard Model expectation is seen and upper limits on the production cross-section of a vector-like T quark pair as a function of the T quark mass are derived. The observed (expected) 95% CL lower limits on the T mass are 870 GeV (890 GeV) for the weak-isospin singlet model, 1.05 TeV (1.06 TeV) for the weak-isospin doublet model and 1.16 TeV (1.17 TeV) for the pure Zt decay mode. Limits are also set on the mass as a function of the decay branching ratios, excluding large parts of the parameter space for masses below 1 TeV.
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Erratum to: Search for supersymmetry in final states with two same-sign or three leptons and jets using 36 fb -1 of $ \sqrt{s} $ = 13 TeV pp collision data with the ATLAS detector
One correction is made to the figure 4e of the paper. The reported cross-sections, both the experimental upper limits and the theoretical prediction, corresponded only to a fiducial region of the phase space with at least two prompt same-sign electrons or muons before detector simulation (p T > 10 GeV, |η| < 2.8). The updated figure 4e instead presents the results without this requirement, i.e. in the full phase space as it should, given the y-axis label of the plot. The reported sensitivity of the analysis, i.e. the ability to exclude top squark masses below 700 GeV in this scenario, is however unchanged since the same requirements were applied to the analysis and to the theory predictions.
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Measurement of jet activity in top quark events using the eμ final state with two b-tagged jets in pp collisions at $\sqrt{s}=8 $ TeV with the ATLAS detector
Measurements of the jet activity in tt¯ events produced in proton-proton collisions at √s=8 TeV are presented, using 20.3 fb –1 of data collected by the ATLAS experiment at the Large Hadron Collider. The events were selected in the dilepton eμ decay channel with two identified b-jets. The numbers of additional jets for various jet transverse momentum (p T ) thresholds, and the normalised differential cross-sections as a function of p T for the five highest-p T additional jets, were measured in the jet pseudo-rapidity range |η| < 4.5. The gap fraction, the fraction of events which do not contain an additional jet in a central rapidity region, was measured for several rapidity intervals as a function of the minimum p T of a single jet or the scalar sum of p T of all additional jets. These fractions were also measured in different intervals of the invariant mass of the eμbb¯ system. All measurements were corrected for detector effects, and found to be mostly well-described by predictions from next-to-leading-order and leading-order tt¯ event generators with appropriate parameter choices. Lastly, the results can be used to further optimise the parameters used in such generators.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Searches for heavy diboson resonances in pp collisions at $ \sqrt{s}=13 $ TeV with the ATLAS detector
Searches for new heavy resonances decaying to WW, WZ, and ZZ bosons are presented, using a data sample corresponding to 3.2 fb -1 of pp collisions at s=13 TeV colle cted with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting ννqq, ℓνqq, ℓℓqq and qqqq final states are combined, searching for an arrow-width resonance with mass between 500 and 3000 GeV. The discriminating variable is either an invariant mass or a transverse mass. No significant deviations from the Standard Model predictions are observed. Three benchmark models are tested: a model predicting the existence of a new heavy scalar singlet, a simplified model predicting a heavy vector-boson triplet, and a bulk Randall-Sundrum model with a heavy spin-2 graviton. Cross-section limits are set at the 95% confidence level and are compared to theoretical cross-section predictions for a variety of models. The data exclude a scalar singlet with mass below 2650 GeV, a heavy vector-boson triplet with mass below 2600 GeV, and a graviton with mass below 1100 GeV. These results significantly extend the previous limits set using pp collisions at √s=8 TeV.
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