Rubin-LSST

Abstract:

A search for the dimuon decay of the Higgs boson is presented based on $pp$ collision data recorded by ATLAS during Run 3 of the Large Hadron Collider, corresponding to an integrated luminosity of $165{\mathrm{fb}}^{-1}$ at $\sqrt{s}=13.6\mathrm{TeV}$ . To enhance the sensitivity, the results are combined with those from Run 2. An excess of events over the background is observed with a significance of $3.4\sigma$ ( $2.5\sigma$ expected). The best-fit signal strength is $\mu =1.4\pm 0.4$ . This result provides evidence for the $H\to \mu \mu$ decay with ATLAS data and offers a direct probe of the Higgs-boson Yukawa coupling to second-generation fermions.

Abstract:

A measurement of the top-quark pole mass mtpole$$ {m}_t^{\textrm{pole}} $$ is presented in tt¯$$ t\overline{t} $$ events with an additional jet, tt¯$$ t\overline{t} $$ + 1-jet, produced in pp collisions at s=13$$ \sqrt{s}=13 $$ TeV. The data sample, recorded with the ATLAS experiment during Run 2 of the LHC, corresponds to an integrated luminosity of 140 fb−1. Events with one electron and one muon of opposite electric charge in the final state are selected to measure the tt¯$$ t\overline{t} $$ + 1-jet differential cross-section as a function of the inverse of the invariant mass of the tt¯$$ t\overline{t} $$ + 1-jet system. Iterative Bayesian Unfolding is used to correct the data to enable comparison with fixed-order calculations at next-to-leading-order accuracy in the strong coupling. The process pp→tt¯j2→3$$ pp\to t\overline{t}j\left(2\to 3\right) $$, where top quarks are taken as stable particles, and the process pp→bb¯l+νl−ν¯j2→7$$ pp\to b\overline{b}{l}^{+}\nu {l}^{-}\overline{\nu}j\left(2\to 7\right) $$, which includes top-quark decays to the dilepton final state and off-shell effects, are considered. The top-quark mass is extracted using a χ2 fit of the unfolded normalized differential cross-section distribution. The results obtained with the 2 → 3 and 2 → 7 calculations are compatible within theoretical uncertainties, providing an important consistency check. The more precise determination is obtained for the 2 → 3 measurement: mtpole=170.7±0.3stat.±1.4syst.±0.3scale±0.2PDF⊕αS$$ {m}_t^{\textrm{pole}}=170.7\pm 0.3\left(\textrm{stat}.\right)\pm 1.4\left(\textrm{syst}.\right)\pm 0.3\left(\textrm{scale}\right)\pm 0.2\left(\textrm{PDF}\oplus {\alpha}_{\textrm{S}}\right) $$ GeV, which is in good agreement with other top-quark mass results.

Abstract:

A search for single production of a vector-like quark Q, which could be either a singlet T, with charge 23$$ \frac{2}{3} $$, or a Y from a (T, B, Y) triplet, with charge −43$$ -\frac{4}{3} $$, is performed using data from proton-proton collisions at a centre-of-mass energy of 13 TeV. The data correspond to the full integrated luminosity of 140 fb−1 recorded with the ATLAS detector during Run 2 of the Large Hadron Collider. The analysis targets Q → Wb decays where the W boson decays leptonically. The data are found to be consistent with the expected Standard Model background, so upper limits are set on the cross-section times branching ratio, and on the coupling of the Q to the Standard Model sector for these two benchmark models. Effects of interference with the Standard Model background are taken into account. For the singlet T, the 95% confidence level limit on the coupling strength κ ranges between 0.22 and 0.52 for masses from 1150 to 2300 GeV. For the (T, B, Y) triplet, the limits on κ vary from 0.14 to 0.46 for masses from 1150 to 2600 GeV.

Abstract:

Context. The H I mass function (HIMF) is a crucial tool for understanding the evolution of the H I content in galaxies over cosmic time and, hence, to constraining both the baryon cycle in galaxy evolution and the reionization history of the Universe. Aims. We aim to derive semiempirical constraints at z  ∼ 0.37 by combining literature results on the stellar mass function from optical surveys with recent findings on the M HI  −  M ⋆ scaling relation derived via spectral stacking analysis applied to 21 cm line interferometric data from the MIGHTEE and CHILES surveys, conducted with the MeerKAT and VLA radio telescopes, respectively. Methods. We drew synthetic stellar mass samples directly from the publicly available results underlying the analysis of the COSMOS2020 galaxy photometric sample. We then converted M ⋆ into M HI using analytical fitting functions to the data points from H I stacking. We next fit a Schechter function to the median HIMF from all the samples via Monte Carlo Markov chains. We finally derived the posterior distribution for Ω HI by integrating the models for the HIMF built from the posteriors samples of the Schechter parameters. Results. We find a deviation of the HIMF at z  ∼ 0.37 from the results at z  ∼ 0 from the ALFALFA survey and at z  ∼ 1 from uGMRT data. Our results for Ω HI are in broad agreement with other literature results and follow the overall trend on Ω HI as a function of redshift. The derived value Ω HI = (7.02 +0.59 −0.52 ) × 10 −4 at z  ∼ 0.37 from the combined analysis deviates by ∼2.9 σ from the ALFALFA result at z  ∼ 0. Conclusions. Our findings regarding the HIMF and Ω HI derived from deep, state-of-the-art interferometric surveys differ from previous literature results at z  ∼ 0 and z  ∼ 1. We are unable to confirm at this stage whether these differences are due to cosmic evolution consistent with a smooth transition of the H I content of galaxies over the last 8 Gyr or due to selection biases and systematics.