3,780 research outputs found
Search for a CP-odd Higgs boson decaying to Zh in pp collisions at root s=8 TeV with the ATLAS detector
No full textSee paper for full list of authors – 13 pages plus author list + cover pages (30 pages total), 5 figures, 2 tables, submitted to Phys. Lett. B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2013-06/International audienceA search for a heavy, CP-odd Higgs boson, , decaying into a boson and a 125 GeV Higgs boson, , with the ATLAS detector at the LHC is presented. The search uses proton--proton collision data at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb. Decays of CP-even bosons to or pairs with the boson decaying to electron or muon pairs are considered, as well as decays with the boson decaying to neutrinos. No evidence for the production of an boson in these channels is found and the 95% confidence level upper limits derived for \sigma (gg\rightarrow A) \times \mbox{BR}(A \rightarrow Zh) \times \mbox{BR}(h \rightarrow f\bar{f}) are 0.098--0.013 pb for and 0.57--0.014 pb for in a range of 220--1000 GeV. The results are combined and interpreted in the context of two-Higgs doublet models
Search for W ' -> t(b)over-bar in the lepton plus jets final state in proton-proton collisions at a centre-of-mass energy of root s=8 TeV with the ATLAS detector
No full textA search for new charged massive gauge bosons, called W', is performed with the ATLAS detector at the LHC, in proton-proton collisions at a centre-of-mass energy of root s = 8 TeV, using a dataset corresponding to an integrated luminosity of 20.3 fb(-1). This analysis searches for W' bosons in the W' -> t (b) over tilde decay channel in final states with electrons or muons, using a multivariate method based on boosted decision trees. The search covers masses between 0.5 and 3.0 TeV, for right-handed or left-handed W' bosons. No significant deviation from the Standard Model expectation is observed and limits are set on the W' -> t (b) over bar cross-section times branching ratio and on the W'-boson effective couplings as a function of the W'-boson mass using the CLs procedure. For a left-handed (right-handed) W' boson, masses below 1.70 (1.92) TeV are excluded at 95% confidence level.ATLAS Collaboration, for complete list of authors see http://dx.doi.org/10.1016/j.physletb.2015.02.051</p
Search for single production of a vector-like quark via a heavy gluon in the 4b final state with the ATLAS detector in pp collisions at root s=8 TeV
No full textA search is performed for the process pp -> G* -> B-H(b) over bar/(B) over bar (H)b -> Hb (b) over bar -> b (b) over barb (b) over bar, predicted in composite Higgs scenarios, where G* is a heavy colour octet vector resonance and B-H a vector-like quark of charge -1/3. The data were obtained from pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.5 fb(-1), recorded by the ATLAS detector at the LHC. The largest background, multijet production, is estimated using a data-driven method. No significant excess of events with respect to Standard Model predictions is observed, and upper limits on the production cross section times branching ratio are set. Comparisons to the predictions from a specific benchmark model are made, resulting in lower mass limits in the two-dimensional mass plane of m(G*) vs. m(BH). (c) 2016 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license
Search for single vector-like quark production and decay via in collisions at TeV with the ATLAS detector
No full textA search is presented for single production of a vector-like B quark decaying into a Standard Model b-quark and a Standard Model Higgs boson, which decays into a pair. The search is carried out in 139 fb of = 13 TeV proton-proton collision data collected by the ATLAS detector at the LHC between 2015 and 2018. No significant deviation from the Standard Model background prediction is observed, and mass-dependent exclusion limits at the 95% confidence level are set on the resonance production cross-section in several theoretical scenarios determined by the couplings c, c and c between the B quark and the Standard Model W, Z and Higgs bosons, respectively. For a vector-like B occurring as an isospin singlet, the search excludes values of c greater than 0.45 for a B resonance mass (m) between 1.0 and 1.2 TeV. For 1.2 TeV < m< 2.0 TeV, c values larger than 0.50–0.65 are excluded. If the B occurs as part of a (B, Y) doublet, the smallest excluded c coupling values range between 0.3 and 0.5 across the investigated resonance mass range 1.0 TeV < m< 2.0 TeV.[graphic not available: see fulltext]A search is presented for single production of a vector-like quark decaying into a Standard Model -quark and a Standard Model Higgs boson, which decays into a pair. The search is carried out in 139 fb of TeV proton-proton collision data collected by the ATLAS detector at the LHC between 2015 and 2018. No significant deviation from the Standard Model background prediction is observed, and mass-dependent exclusion limits at the 95% confidence level are set on the resonance production cross-section in several theoretical scenarios determined by the couplings , and between the quark and the Standard Model , and Higgs bosons, respectively. For a vector-like occurring as an isospin singlet, the search excludes values of greater than 0.45 for a resonance mass () between 1.0 and 1.2 TeV. For 1.2 TeV < < 2.0 TeV, values larger than 0.50-0.65 are excluded. If the occurs as part of a doublet, the smallest excluded coupling values range between 0.3 and 0.5 across the investigated resonance mass range 1.0 TeV < < 2.0 TeV
Search for new resonances decaying to a or boson and a Higgs boson in the , , and channels with collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors, 18 pages (plus author list + cover pages: 36 pages total), 13 figures, 1 table. Submitted to PLB. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2015-18/International audienceA search is presented for new resonances decaying to a or boson and a Higgs boson in the , , and channels in collisions at TeV with the ATLAS detector at the Large Hadron Collider using a total integrated luminosity of 3.2 fb. The search is conducted by looking for a localized excess in the / invariant or transverse mass distribution. No significant excess is observed, and the results are interpreted in terms of constraints on a simplified model based on a phenomenological Lagrangian of heavy vector triplets
Search for pair production of Higgs bosons in the final state using proton--proton collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors - 25 pages plus author list + cover pages (43 pages total), 10 figures, 7 tables, submitted to Phys. Rev. D, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2015-11International audienceA search for Higgs-boson pair production in the final state is carried out with 3.2 fb of proton--proton collision data collected at TeV with the ATLAS detector. The data are consistent with the estimated background and are used to set upper limits on the production cross section of Higgs-boson pairs times branching ratio to for both nonresonant and resonant production. In the case of resonant production of Kaluza--Klein gravitons within the Randall--Sundrum model, upper limits in the 24 to 91 fb range are obtained for masses between 600 and 3000 GeV, at the 95% confidence level. The production cross section times branching ratio for nonresonant Higgs-boson pairs is also constrained to be less than 1.22 pb, at the 95% confidence level
Search for new phenomena in final states with large jet multiplicities and missing transverse momentum at s√=8 TeV proton-proton collisions using the ATLAS experiment
No full textA search is presented for new particles decaying to large numbers (7 or more) of jets, with missing transverse momentum and no isolated electrons or muons. This analysis uses 20.3 fb−1 of pp collision data at s√=8 TeV collected by the ATLAS experiment at the Large Hadron Collider. The sensitivity of the search is enhanced by considering the number of b-tagged jets and the scalar sum of masses of large-radius jets in an event. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of various simplified supersymmetry-inspired models where gluinos are pair produced, as well as an mSUGRA/CMSSM model
Observation of H -> b(b)over-bar decays and V H production with the ATLAS detector
No full textA search for the decay of the Standard Model Higgs boson into a b (b) over bar pair when produced in association with a W or Z boson is performed with the ATLAS detector. The data, corresponding to an integrated luminosity of 79.8 fb(-1) were collected in proton-proton collisions during Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV. For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.9 (4.3) standard deviations. A combination with the results from other searches in Run 1 and in Run 2 for the Higgs boson in the bb decay mode is performed, which yields an observed (expected) significance of 5.4 (5.5) standard deviations, thus providing direct observation of the Higgs boson decay into b-quarks. The ratio of the measured event yield for a Higgs boson decaying into b (b) over bar to the Standard Model expectation is 1.01 +/- 0.12(stat.) (-0.15) (+0.16)(syst.). Additionally, a combination of Run 2 results searching for the Higgs boson produced in association with a vector boson yields an observed (expected) significance of 5.3 (4.8) standard deviations. (C) 2018 The Author(s). Published by Elsevier B.V
Search for pairs of highly collimated photon-jets in pp collisions at √s = 13 TeV with the ATLAS detector
No full textResults of a search for the pair production of photon-jets—collimated groupings of photons—in the ATLAS detector at the Large Hadron Collider are reported. Highly collimated photon-jets can arise from the decay of new, highly boosted particles that can decay to multiple photons collimated enough to be identified in the electromagnetic calorimeter as a single, photonlike energy cluster. Data from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of
36.7
fb
−
1
, were collected in 2015 and 2016. Candidate photon-jet pair production events are selected from those containing two reconstructed photons using a set of identification criteria much less stringent than that typically used for the selection of photons, with additional criteria applied to provide improved sensitivity to photon-jets. Narrow excesses in the reconstructed diphoton mass spectra are searched for. The observed mass spectra are consistent with the Standard Model background expectation. The results are interpreted in the context of a model containing a new, high-mass scalar particle with narrow width,
X
, that decays into pairs of photon-jets via new, light particles,
a
. Upper limits are placed on the cross section times the product of branching ratios
σ
×
B
(
X
→
a
a
)
×
B
(
a
→
γ
γ
)
2
for
200
GeV
<
m
X
<
2
TeV
and for ranges of
m
a
from a lower mass of 100 MeV up to between 2 and 10 GeV, depending upon
m
X
. Upper limits are also placed on
σ
×
B
(
X
→
a
a
)
×
B
(
a
→
3
π
0
)
2
for the same range of
m
X
and for ranges of
m
a
from a lower mass of 500 MeV up to between 2 and 10 GeV
- …
