Search for pair-produced vector-like top quarks decaying into Lorentz-boosted top quarks and scalar bosons in proton-proton collisions at $\sqrt{s}$ = 13 TeV
A search for pair-produced vector-like top quarks, T, decaying into a new scalar boson $\phi$ and a standard model (SM) top quark is presented. The search targets events containing a photon pair originating from the decay of one of the scalar bosons, accompanied by all-hadronic decays of the SM top quark pair. The analysis is optimized for boosted top quark signatures in which the decay products of the top quarks are reconstructed as large-radius jets. The search is based on proton-proton collision data at $\sqrt{s}$ = 13 TeV, collected by the CMS experiment at the CERN LHC during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The search is performed for an array of T and $\phi$ masses. No significant deviation from the predicted background is observed. The largest local excess has a significance of 2.7 standard deviations, reduced to 1.5 standard deviations after accounting for the look-elsewhere effect. Upper limits at 95% confidence level are set on the product of $\mathrm{T\bar{T}}$ production cross section and the branching fraction.
The first single-experiment observation of single top-quark production in the $s$-channel is presented. Measurements of this process are essential to fully characterize the electroweak interactions of the top quark and probe for new physics, however its highly suppressed cross-section has so far caused it to evade dire...
A search for a new top-philic vector boson ($Z'$) produced in association with a top-quark or a pair of top quarks, and decaying into a top quark pair is presented. The search uses $pp$ collision data collected by the ATLAS detector at the Large Hadron Collider at centre-of-mass energies of $\sqrt{s} =$ 13 TeV and 13.6...
A search is presented for a light pseudoscalar Higgs boson, a, using LHC proton-proton data at $\sqrt{s}$ = 13 TeV collected by the CMS experiment from 2016 to 2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis targets the process H $\to$ aa $\to \mu\mu\tau\tau$, where the scalar H can be ei...
A search for charged-lepton-flavour violation (cLFV) in top-quark production and decay is presented. The data analysed correspond to 140 fb$^{-1}$ of proton-proton collisions recorded at a centre-of-mass energy of $\sqrt{s}= 13$ TeV by the ATLAS detector at the Large Hadron Collider. The possible cLFV contribution is s...
We investigate theoretical uncertainties arising from the choice of the top-quark mass scheme in Higgs boson pair production via gluon fusion. First, we implement the resummation of the top-quark mass logarithms obtained for the $gg\to HH$ amplitude at high energy and study its phenomenological impact on cross sections...
C. Del Pio, S. Jaskiewicz, Rebecca von Kuk et al.· 0 citations
A search for the electroweak production of a Higgs boson in association with a same-sign $W$ boson pair and two forward jets ($W^{\pm}W^{\pm}Hjj$) is presented. The full Run 2 proton-proton collision dataset recorded at a center-of-mass energy of $\sqrt{s}=13$ TeV by the ATLAS detector at the Large Hadron Collider is u...
A. Collaboration· 0 citations
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