A search for exotic decays of the 125 GeV Higgs boson into a pair of new spin-0 particles, H → aa, where one decays into a photon pair and the other into a τ-lepton pair, is presented. Hadronic decays of the τ-lept...
A search for exotic decays of the 125 GeV Higgs boson into a pair of new spin-0 particles, H → aa, where one decays into a photon pair and the other into a τ-lepton pair, is presented. Hadronic decays of the τ-leptons are considered and reconstructed using a dedicated tagger for collimated τ-lepton pairs. The search uses 140 fb−1 of proton-proton collision data at a centre-of-mass energy of $$ \sqrt{s} $$ = 13 TeV recorded between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider. The search is performed in the mass range of the a boson between 10 GeV and 60 GeV. No significant excess of events is observed above the Standard Model background expectation. Model-independent upper limits at 95% confidence level are set on the branching ratio of the Higgs boson to the γγττ final state, $$ \mathcal{B} $$ (H → aa → γγττ), ranging from 0.2% to 2%, depending on the a-boson mass hypothesis.
This article reports on the inclusive production cross section of several quarkonium states, $$\textrm{J}/\psi $$ , $$\psi \mathrm{(2S)}$$ , $$\Upsilon \mathrm (1S)$$ , $$\Upsilon \mathrm{(2S)}$$ , and $$\Upsilon \mat...
This article reports on the inclusive production cross section of several quarkonium states, $$\textrm{J}/\psi $$ , $$\psi \mathrm{(2S)}$$ , $$\Upsilon \mathrm (1S)$$ , $$\Upsilon \mathrm{(2S)}$$ , and $$\Upsilon \mathrm{(3S)}$$ , measured with the ALICE detector at the LHC, in pp collisions at $$\sqrt{s} = 5.02$$ TeV. The analysis is performed in the dimuon decay channel at forward rapidity ( $$2.5< y < 4$$ ). The integrated cross sections and transverse-momentum ( $$p_{\textrm{T}}$$ ) and rapidity ( $$y$$ ) differential cross sections for $$\textrm{J}/\psi $$ , $$\psi \mathrm{(2S)}$$ , $$\Upsilon \mathrm (1S)$$ , and the $$\psi \mathrm{(2S)}$$ -to- $$\textrm{J}/\psi $$ cross section ratios are presented. The integrated cross sections, assuming unpolarized quarkonia, are: $$\sigma _{\textrm{J}/\psi }$$ ( $$p_{\textrm{T}} <20$$ GeV/c) = 5.88 ± 0.03 ± 0.34 $$ ~\mu $$ b, $$\sigma _{\psi \mathrm{(2S)}}$$ ( $$p_{\textrm{T}} <12$$ GeV/c) = 0.87 ± 0.06 ± 0.10 $$~\mu $$ b, $$\sigma _{\Upsilon \mathrm (1S)}$$ ( $$p_{\textrm{T}} <15$$ GeV/c) = 45.5 ± 3.9 ± 3.5 nb, $$\sigma _{\Upsilon \mathrm{(2S)}}$$ ( $$p_{\textrm{T}} <15$$ GeV/c) = 22.4 ± 3.2 ± 2.7 nb, and $$\sigma _{\Upsilon \mathrm{(3S)}}$$ ( $$p_{\textrm{T}} <15$$ GeV/c) = 4.9 ± 2.2 ± 1.0 nb, where the first (second) uncertainty is the statistical (systematic) one. For the first time, the cross sections of the three $$\Upsilon $$ states, as well as the $$\psi \mathrm{(2S)}$$ one as a function of $$p_{\textrm{T}}$$ and $$y$$ , are measured at $$\sqrt{s} = 5.02$$ TeV at forward rapidity. These measurements also significantly extend the $$\textrm{J}/\psi $$ $$p_{\textrm{T}}$$ reach and supersede previously published results. A comparison with ALICE measurements in pp collisions at $$\sqrt{s} = 2.76$$ , 7, 8, and 13 TeV is presented and the energy dependence of quarkonium production cross sections is discussed. F
Measurements of the differential production cross-sections of prompt and non-prompt J/ψ and ψ(2S) mesons with transverse momenta between 8 and 360 GeV and rapidity in the range |y|-1 of s=13 TeV pp collisi...
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This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb−1 of LHC proton-proton collision data recorded at √s = 13 TeV between 2015 and 2018. Methods for the measur...
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The inclusive Higgs boson production cross-section is measured in the di-photon and the ZZ∗→ 4 decay channels using 31.4 and 29.0 fb - 1 of pp collision data respectively, collected with the ATLAS detector at a ...
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Recently, several gamma-ray bursts (GRBs) have been detected in the very-high-energy (VHE) gamma-ray energy range by ground-based gamma-ray experiments such as MAGIC, H.E.S.S., and LHASSO. For some GRBs, the VHE emiss...
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The production of the ψ(2S) charmonium state was measured with ALICE in Pb-Pb collisions at sNN=5.02 TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zer...
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The production of the ψ(2S) charmonium state was measured with ALICE in Pb-Pb collisions at sNN=5.02 TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (2.5nuclear modification factor RAA was also obtained as a function of both centrality and pT. The results show that the ψ(2S) resonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up to ∼3 with respect to pp. Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and of RAA with higher-pT results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC.
The associated production of Higgs and W bosons via vector-boson fusion is highly sensitive to the relative sign of the Higgs boson couplings to W and Z bosons. In this Letter, two searches for this process are presen...
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The associated production of Higgs and W bosons via vector-boson fusion is highly sensitive to the relative sign of the Higgs boson couplings to W and Z bosons. In this Letter, two searches for this process are presented, using 140 fb−1 of proton-proton collision data at s=13 TeV recorded by the ATLAS detector at the LHC. The first search targets scenarios with opposite-sign couplings of the W and Z bosons to the Higgs boson, while the second targets standard model-like scenarios with same-sign couplings. Both analyses consider Higgs boson decays into a pair of b quarks and W boson decays with an electron or muon. The data exclude the opposite-sign coupling hypothesis with a significance beyond 5σ, and the observed (expected) upper limit set on the cross section for vector-boson fusion WH production is 9.0 (8.7) times the standard model value at 95% confidence level.
This article presents a search for a heavy charged Higgs boson produced in association with a top quark and a bottom quark, and decaying into a W boson and a 125 GeV Higgs boson h. The search is performed in final sta...
This article presents a search for a heavy charged Higgs boson produced in association with a top quark and a bottom quark, and decaying into a W boson and a 125 GeV Higgs boson h. The search is performed in final states with one charged lepton, missing transverse momentum, and jets using proton-proton collision data at $$ \sqrt{s} $$ = 13 TeV recorded with the ATLAS detector during Run 2 of the LHC at CERN. This data set corresponds to a total integrated luminosity of 140 fb−1. The search is conducted by examining the reconstructed invariant mass distribution of the Wh candidates for evidence of a localised excess in the charged Higgs boson mass range from 250 GeV to 3 TeV. No significant excess of data over the expected background is observed and 95% confidence-level upper limits between 2.8 pb and 1.2 fb are placed on the production cross-section times branching ratio for charged Higgs bosons decaying into Wh.
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