Objective To evaluate the association of 2008-9 seasonal trivalent inactivated vaccine with cases of influenza A/H1N1 during the epidemic in Mexico.Design Frequency matched case-control study.Setting ...Specialty hospital in Mexico City, March to May 2009.Participants 60 patients with laboratory confirmed influenza A/H1N1 and 180 controls with other diseases (not influenza-like illness or pneumonia) living in Mexico City or the State of Mexico and matched for age and socioeconomic status.Main outcome measures Odds ratio and effectiveness of trivalent inactivated vaccine against influenza A/H1N1.Results Cases were more likely than controls to be admitted to hospital, undergo invasive mechanical ventilation, and die. Controls were more likely than cases to have chronic conditions that conferred a higher risk of influenza related complications. In the multivariate model, influenza A/H1N1 was independently associated with trivalent inactivated vaccine (odds ratio 0.27, 95% confidence interval 0.11 to 0.66) and underlying conditions (0.15, 0.08 to 0.30). Vaccine effectiveness was 73% (95% confidence interval 34% to 89%). None of the eight vaccinated cases died.Conclusions Preliminary evidence suggests some protection from the 2008-9 trivalent inactivated vaccine against pandemic influenza A/H1N1 2009, particularly severe forms of the disease, diagnosed in a specialty hospital during the influenza epidemic in Mexico City.
A
bstract
A search for heavy right-handed Majorana or Dirac neutrinos
N
R
and heavy right-handed gauge bosons
W
R
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.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The jet energy scale and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in ...proton-proton collision data at a centre-of-mass energy of ... corresponding to an integrated luminosity of 38 pb^sup -1^. Jets are reconstructed with the anti-k ^sub t^ algorithm with distance parameters R=0.4 or R=0.6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta p ^sub T^greater than or equal to20 GeV and pseudorapidities |eta|<4.5. The jet energy systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams, exploiting the transverse momentum balance between central and forward jets in events with dijet topologies and studying systematic variations in Monte Carlo simulations. The jet energy uncertainty is less than 2.5 % in the central calorimeter region (|eta|<0.8) for jets with 60less than or equal top ^sub T^<800 GeV, and is maximally 14 % for p ^sub T^<30 GeV in the most forward region 3.2less than or equal to|eta|<4.5. The jet energy is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon p ^sub T^, the sum of the transverse momenta of tracks associated to the jet, or a system of low-p ^sub T^ jets recoiling against a high-p ^sub T^ jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, aiming for an improved jet energy resolution and a reduced flavour dependence of the jet response. The systematic uncertainty of the jet energy determined from a combination of in situ techniques is consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-p ^sub T^ jets. Special cases such as event topologies with close-by jets, or selections of samples with an enhanced content of jets originating from light quarks, heavy quarks or gluons are also discussed and the corresponding uncertainties are determined.
A search for weakly interacting massive dark-matter particles produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and missing transverse ...momentum are considered. The analysis uses
36.1
fb
-
1
of proton–proton collision data recorded by the ATLAS experiment at
s
=
13
TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are interpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour-neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross-section of 300 times the predicted rate for mediators with masses between 10 and
50
GeV
and assuming a dark-matter mass of
1
GeV
and unitary coupling. Constraints on colour-charged scalar simplified models are also presented. Assuming a dark-matter particle mass of
35
GeV
, mediator particles with mass below
1.1
TeV
are excluded for couplings yielding a dark-matter relic density consistent with measurements.
A
bstract
This paper presents a measurement of
ZZ
production with the ATLAS detector at the Large Hadron Collider. The measurement is carried out in the final state with two charged leptons and two ...neutrinos, using data collected during 2015 and 2016 in
pp
collisions at
s
= 13 TeV, corresponding to an integrated luminosity of 36.1 fb
−
1
. The integrated cross-sections in the total and fiducial phase spaces are measured with an uncertainty of 7% and compared with Standard Model predictions, and differential measurements in the fiducial phase space are reported. No significant deviations from the Standard Model predictions are observed, and stringent constraints are placed on anomalous couplings corresponding to neutral triple gauge-boson interactions.
A
bstract
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 significant 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
θ
L
| = 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.
The standard model of particle physics
describes the known fundamental particles and forces that make up our Universe, with the exception of gravity. One of the central features of the standard model ...is a field that permeates all of space and interacts with fundamental particles
. The quantum excitation of this field, known as the Higgs field, manifests itself as the Higgs boson, the only fundamental particle with no spin. In 2012, a particle with properties consistent with the Higgs boson of the standard model was observed by the ATLAS and CMS experiments at the Large Hadron Collider at CERN
. Since then, more than 30 times as many Higgs bosons have been recorded by the ATLAS experiment, enabling much more precise measurements and new tests of the theory. Here, on the basis of this larger dataset, we combine an unprecedented number of production and decay processes of the Higgs boson to scrutinize its interactions with elementary particles. Interactions with gluons, photons, and W and Z bosons-the carriers of the strong, electromagnetic and weak forces-are studied in detail. Interactions with three third-generation matter particles (bottom (b) and top (t) quarks, and tau leptons (τ)) are well measured and indications of interactions with a second-generation particle (muons, μ) are emerging. These tests reveal that the Higgs boson discovered ten years ago is remarkably consistent with the predictions of the theory and provide stringent constraints on many models of new phenomena beyond the standard model.
A
bstract
A search for a narrow scalar resonance decaying into an opposite-sign muon pair produced in events with and without
b
-tagged jets is presented in this paper. The search uses 36.1 fb
−1
of
...s
=
13
TeV proton-proton collision data recorded by the ATLAS experiment at the LHC. No significant excess of events above the expected Standard Model background is observed in the investigated mass range of 0.2 to 1.0 TeV. The observed upper limits at 95% confidence level on the cross section times branching ratio for
b
-quark associated production and gluon-gluon fusion are between 1.9 and 41 fb and 1.6 and 44 fb respectively, which is consistent with expectations.
A
bstract
This paper describes a search for events with one top-quark and large missing transverse momentum in the final state. Data collected during 2015 and 2016 by the ATLAS experiment from 13 TeV ...proton–proton collisions at the LHC corresponding to an integrated luminosity of 36.1 fb
−1
are used. Two channels are considered, depending on the leptonic or the hadronic decays of the
W
boson from the top quark. The obtained results are interpreted in the context of simplified models for dark-matter production and for the single production of a vector-like
T
quark. In the absence of significant deviations from the Standard Model background expectation, 95% confidence-level upper limits on the corresponding production cross-sections are obtained and these limits are translated into constraints on the parameter space of the models considered.
The results of a search for new heavy
W
′
bosons decaying to an electron or muon and a neutrino using proton–proton collision data at a centre-of-mass energy of
s
=
13
TeV are presented. The dataset ...was collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1
fb
-
1
. As no excess of events above the Standard Model prediction is observed, the results are used to set upper limits on the
W
′
boson cross-section times branching ratio to an electron or muon and a neutrino as a function of the
W
′
mass. Assuming a
W
′
boson with the same couplings as the Standard Model
W
boson,
W
′
masses below 5.1 TeV are excluded at the 95% confidence level.
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