In this Letter, the first evidence of the ${}^4_{\bar{\Lambda}}\overline{\mathrm{He}}$ antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number $A=4$, specifically (anti)${}^4_{\Lambda}\mathrm{H}$ and (anti)${}^4_{\Lambda}\mathrm{He}$. In addition, the antiparticle-to-particle ratios for both hypernuclei (${}^4_{\bar{\Lambda}}\overline{\mathrm{H}}$ / ${}^4_{\Lambda}\mathrm{H}$~and ${}^4_{\bar{\Lambda}}\overline{\mathrm{He}}$ / ${}^4_{\Lambda}\mathrm{He}$) are shown, which are sensitive to the baryochemical potential of the strongly-interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb--Pb collisions, collected during the 2018 LHC data-taking at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}} = $ 5.02 TeV. The yields measured for the average of the charge-conjugated states are found to be $[0.78 \; \pm \; 0.19 \; \mathrm{(stat.)} \; \pm \; 0.17 \; \mathrm{(syst.)}] \times 10^{-6}$ for the (anti)${}^4_{\Lambda}\mathrm{H}$ and $[1.08 \; \pm \; 0.34 \; \mathrm{(stat.)} \; \pm \; 0.20 \; \mathrm{(syst.)}] \times 10^{-6}$ for the (anti)${}^4_{\Lambda}\mathrm{He}$, and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of (anti)${}^4_{\Lambda}\mathrm{H}$ and (anti)${}^4_{\Lambda}\mathrm{He}$ excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of 3.3$\sigma$ from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within 0.6$\sigma$ with the present measurements. Additionally, the measured (anti)${}^4_{\Lambda}\mathrm{H}$ and (anti)${}^4_{\Lambda}\mathrm{He}$ masses are compatible with the world-average values within the uncertainties.
average pT-integrated yield of particle and antiparticle of both analyzed (anti)hypernuclei in Pb-Pb collisions in 0-10% V0M centrality class
mass measurement of both analyzed (anti)hypernuclei in Pb-Pb collisions in 0-10% V0M centrality class
antiparticle-to-particle ratio of the analyzed (anti)hypernuclei in Pb-Pb collisions in 0-10% V0M centrality class
A search for heavy Higgs bosons produced in association with a vector boson and decaying into a pair of vector bosons is performed in final states with two leptons (electrons or muons) of the same electric charge, missing transverse momentum and jets. A data sample of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider between 2015 and 2018 is used. The data correspond to a total integrated luminosity of 139 fb$^{-1}$. The observed data are in agreement with Standard Model background expectations. The results are interpreted using higher-dimensional operators in an effective field theory. Upper limits on the production cross-section are calculated at 95% confidence level as a function of the heavy Higgs boson's mass and coupling strengths to vector bosons. Limits are set in the Higgs boson mass range from 300 to 1500 GeV, and depend on the assumed couplings. The highest excluded mass for a heavy Higgs boson with the coupling combinations explored is 900 GeV. Limits on coupling strengths are also provided.
Comparison between data and SM predictions for the meff distributions in the boosted SR. The background predictions are obtained through a background-only simultaneous fit and are shown as filled histograms. The entries in overflow are included in the last bin. The size of the combined statistical and systematic uncertainty for the sum of the fitted background is indicated by the hatched band. The ratio of the data to the sum of the fitted background is shown in the lower panel. Two benchmark signal samples, as indicated in the legend, are also shown as unstacked unfilled histograms normalised to the integrated luminosity of the data using the theoretical cross-sections.
Comparison between data and SM predictions for the meff distributions in the resolved SR. The background predictions are obtained through a background-only simultaneous fit and are shown as filled histograms. The entries in overflow are included in the last bin. The size of the combined statistical and systematic uncertainty for the sum of the fitted background is indicated by the hatched band. The ratio of the data to the sum of the fitted background is shown in the lower panel. Two benchmark signal samples, as indicated in the legend, are also shown as unstacked unfilled histograms normalised to the integrated luminosity of the data using the theoretical cross-sections.
Expected 95% CL upper limits on the production of a heavy Higgs boson as functions of fw and fww with mass equal to 300 GeV.
A search for the direct production of a pair of $\tau$ sleptons, the supersymmetric partners of $\tau$ leptons, is presented. Each $\tau$ slepton is assumed to decay to a $\tau$ lepton and the lightest supersymmetric particle (LSP), which is assumed to be stable and to not interact in the detector, leading to an imbalance in the total reconstructed transverse momentum. The search is carried out in events identified as containing two $\tau$ leptons, each decaying to one or more hadrons and a neutrino, and significant transverse momentum imbalance. In addition to scenarios in which the $\tau$ sleptons decay promptly, the search also addresses scenarios in which the $\tau$ sleptons have sufficiently long lifetimes to give rise to nonprompt $\tau$ leptons. The data were collected in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC with the CMS detector in 2016-2018, and correspond to an integrated luminosity of 138 fb$^{-1}$. No significant excess is seen with respect to standard model expectations. Upper limits on cross sections for the pair production of $\tau$ sleptons are obtained in the framework of simplified models. In a scenario in which the $\tau$ sleptons are superpartners of left-handed $\tau$ leptons, and each undergoes a prompt decay to a $\tau$ lepton and a nearly massless LSP, $\tau$ slepton masses between 115 and 340 GeV are excluded. In a scenario in which the lifetime of the $\tau$ sleptons corresponds to $c\tau_0$ = 0.1 mm, where $\tau_{0}$ represents the mean proper lifetime of the $\tau$ slepton, masses between 150 and 220 GeV are excluded.
Observed events and pre-fit background and signal yields for all 31 SRs
Observed events and pre-fit background and signal yields for all 31 SRs
Observed events and post-fit background yields for all 31 SRs
Signals consistent with the B$^+_\mathrm{c}$(2S) and B$^{*+}_\mathrm{c}$(2S) states are observed in proton-proton collisions at $\sqrt{s} =$ 13 TeV, in an event sample corresponding to an integrated luminosity of 140 fb$^{-1}$, collected by the CMS experiment during the 2016, 2017, and 2018 LHC running periods. These excited $\bar{\mathrm{b}}$c states are observed in the B$^+_\mathrm{c}\pi^+\pi^-$ invariant mass spectrum, with the ground state B$^+_\mathrm{c}$ reconstructed through its decay to J/$\psi\,\pi^+$. The two states are well resolved from each other and are observed with a significance exceeding five standard deviations. The mass of the B$^+_\mathrm{c}$(2S) meson is measured to be 6871.0 $\pm$ 1.2 (stat) $\pm$ 0.8 (syst) $\pm$ 0.8 (B$^+_\mathrm{c}$) MeV, where the last term corresponds to the uncertainty in the world-average B$^+_\mathrm{c}$ mass.
Observation of the Bc(2S) and Bc(2S)* states and measurement of the Bc(2S) mass.
Observation of the Bc(2S) and Bc(2S)* states and measurement of the Bc(2S) mass.
The $\chi_\mathrm{b1}$(3P) and $\chi_\mathrm{b2}$(3P) states are observed through their $\Upsilon$(3S) $\gamma$ decays, using an event sample of proton-proton collisions collected by the CMS experiment at the CERN LHC. The data were collected at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 80.0 fb$^{-1}$. The $\Upsilon$(3S) mesons are identified through their dimuon decay channel, while the low-energy photons are detected after converting to e$^+$e$^-$ pairs in the silicon tracker, leading to a $\chi_\mathrm{b}$(3P) mass resolution of 2.2 MeV. This is the first time that the $J =$ 1 and 2 states are well resolved and their masses individually measured: 10$\,$513.42 $\pm$ 0.41 (stat) $\pm$ 0.18 (syst) MeV and 10$\,$524.02 $\pm$ 0.57 (stat) $\pm$ 0.18 (syst) MeV; they are determined with respect to the world-average value of the $\Upsilon$(3S) mass, which has an uncertainty of 0.5 MeV. The mass splitting is measured to be 10.60 $\pm$ 0.64 (stat) $\pm$ 0.17 (syst) MeV.
Observation of the $\chi_{b1}(3P)$ and $\chi_{b2}(3P)$ and measurement of their masses.
Observation of the $\chi_{b1}(3P)$ and $\chi_{b2}(3P)$ and mass splitting measurement.
Measurements are presented of the lifetimes of the B$^0$, B$^0_\mathrm{s}$, $\Lambda^0_\mathrm{b}$, and B$_\mathrm{c}^+$ hadrons using the decay channels B$^0\to$ J/$\psi$K*(892)$^0$, B$^0\to$J/$\psi$K$^0_\mathrm{S}$, B$^0_\mathrm{s}\to$J/$\psi \pi^+\pi^-$, B$^0_\mathrm{s}\to$J/$\psi\phi$(1020), $\Lambda^0_\mathrm{b}\to$J/$\psi\Lambda^0$, and B$_\mathrm{c}\to$J/$\psi\pi^+$. The data sample, corresponding to an integrated luminosity of 19.7 fb$^{-1}$, was collected by the CMS detector at the LHC in proton-proton collisions at $\sqrt{s}=$ 8 TeV. The B$^0$ lifetime is measured to be 453.0 $\pm$ 1.6 (stat) $\pm$ 1.8 (syst) $\mu$m in J/$\psi$K*(892)$^0$ and 457.8 $\pm$ 2.7 (stat) $\pm$ 2.8 (syst) $\mu$m in J/$\psi$K$^0_\mathrm{S}$, which results in a combined measurement of $c\tau_{\mathrm{B}^0} =$ 454.1 $\pm$ 1.4 (stat) $\pm$ 1.7 (syst) $\mu$m. The effective lifetime of the B$^0_\mathrm{s}$ meson is measured in two decay modes, with contributions from different amounts of the heavy and light eigenstates. This results in two different measured lifetimes: $c\tau_{\mathrm{B}^0_\mathrm{s} \to \mathrm{J}/\psi \pi^+\pi^-} =$ 502.7 $\pm$ 10.2 (stat) $\pm$ 3.4 (syst) $\mu$m and $c\tau_{\mathrm{B}^0_\mathrm{s} \to \mathrm{J}/\psi\phi(1020)} =$ 443.9 $\pm$ 2.0 (stat) $\pm$ 1.5 (syst) $\mu$m. The $\Lambda^0_\mathrm{b}$ lifetime is found to be 443.9 $\pm$ 8.2 (stat) $\pm$ 2.8 (syst) $\mu$m. The precision from each of these channels is as good as or better than previous measurements. The B$_\mathrm{c}^+$ lifetime, measured with respect to the B$^+$ to reduce the systematic uncertainty, is 162.3 $\pm$ 7.8 (stat) $\pm$ 4.2 (syst) $\pm$ 0.1 $(\tau_{\mathrm{B}^+})$ $\mu$m. All results are in agreement with current world-average values.
Measurement of b hadron lifetimes in pp collisions at $\sqrt{s}=8$TeV.
Measurement of b hadron lifetimes ratios in pp collisions at $\sqrt{s}=8$TeV.
Estimate $\Gamma_\mathrm{d}$ and $\Delta \Gamma_\mathrm{d}$ in pp collisions at $\sqrt{s}=8$TeV.
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