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The Pixel Luminosity Telescope is a silicon pixel detector dedicated to luminosity measurement at the CMS experiment at the LHC. It is located approximately 1.75 m from the interaction point and arranged into 16 “telescopes”, with eight telescopes installed around the beam pipe at either end of the detector and each telescope composed of three individual silicon sensor planes. The per-bunch instantaneous luminosity is measured by counting events where all three planes in the telescope register a hit, using a special readout at the full LHC bunch-crossing rate of 40 MHz. The full pixel information is read out at a lower rate and can be used to determine calibrations, corrections, and systematic uncertainties for the online and offline measurements. This paper details the commissioning, operational history, and performance of the detector during Run 2 (2015–18) of the LHC, as well as preparations for Run 3, which will begin in 2022.

A study of the anomalous couplings of the Higgs boson to vector bosons, including$${\textit{CP}}$$$\mathrm{CP}$-violation effects, has been conducted using its production and decay in the WW channel. This analysis is performed on proton–proton collision data collected with the CMS detector at the CERN LHC during 2016–2018 at a center-of-mass energy of 13 TeV, and corresponds to an integrated luminosity of 138$$\,\text {fb}^{-1}$$${\text{fb}}^{-1}$. The different-flavor dilepton$$({\textrm{e}} {{\upmu }})$$$\left(\text{e}\mu \right)$final state is analyzed, with dedicated categories targeting gluon fusion, electroweak vector boson fusion, and associated production with a W or Z boson. Kinematic information from associated jets is combined using matrix element techniques to increase the sensitivity to anomalous effects at the production vertex. A simultaneous measurement of four Higgs boson couplings to electroweak vector bosons is performed in the framework of a standard model effective field theory. All measurements are consistent with the expectations for the standard model Higgs boson and constraints are set on the fractional contribution of the anomalous couplings to the Higgs boson production cross section.

The first observation of the decay${\mathrm{\Xi }}_b^{-}\to \psi (2S){\mathrm{\Xi }}^{-}$and measurement of the branching ratio of${\mathrm{\Xi }}_b^{-}\to \psi (2S){\mathrm{\Xi }}^{-}$to${\mathrm{\Xi }}_b^{-}\to J/\psi {\mathrm{\Xi }}^{-}$are presented. The$J/\psi$and$\psi (2S)$mesons are reconstructed using their dimuon decay modes. The results are based on proton-proton colliding beam data from the LHC collected by the CMS experiment at$\sqrt{s}=13\mathrm{TeV}$in 2016–2018, corresponding to an integrated luminosity of$140{\mathrm{fb}}^{-1}$. The branching fraction ratio is measured to be$\mathcal{B}({\mathrm{\Xi }}_b^{-}\to \psi (2S){\mathrm{\Xi }}^{-})/\mathcal{B}({\mathrm{\Xi }}_b^{-}\to J/\psi {\mathrm{\Xi }}^{-})=0.84_{-0.19}^{+0.21}(\mathrm{stat})\pm 0.10(\mathrm{syst})\pm 0.02(\mathcal{B})$, where the last uncertainty comes from the uncertainties in the branching fractions of the charmonium states. New measurements of the${\mathrm{\Xi }}_b(5945{)}^0$baryon mass and natural width are also presented, using the${\mathrm{\Xi }}_b^{-}{\pi }^{+}$final state, where the${\mathrm{\Xi }}_b^{-}$baryon is reconstructed through the decays$J/\psi {\mathrm{\Xi }}^{-}$,$\psi (2S){\mathrm{\Xi }}^{-}$,$J/\psi \mathrm{\Lambda }{K}^{-}$, and$J/\psi {\mathrm{\Sigma }}^0{K}^{-}$. Finally, the fraction of${\mathrm{\Xi }}_b^{-}$baryons produced from${\mathrm{\Xi }}_b(5945{)}^0$decays is determined.

A search for heavy neutral leptons (HNLs) decaying in the CMS muon system is presented. A data sample is used corresponding to an integrated luminosity of$138{\mathrm{fb}}^{-1}$of proton-proton collisions at$\sqrt{s}=13\mathrm{TeV}$, recorded at the CERN LHC in 2016–2018. Decay products of long-lived HNLs could interact with the shielding materials in the CMS muon system and create hadronic and electromagnetic showers detected in the muon chambers. This distinctive signature provides a unique handle to search for HNLs with masses below 4 GeV and proper decay lengths of the order of meters. The signature is sensitive to HNL couplings to all three generations of leptons. Candidate events are required to contain a prompt electron or muon originating from a vertex on the beam axis and a displaced shower in the muon chambers. No significant deviations from the standard model background expectation are observed. In the electron (muon) channel, the most stringent limits to date are set for HNLs in the mass range of 2.1–3.0 (1.9–3.3) GeV, reaching mixing matrix element squared values as low as$8.6(4.6)\times {10}^{-6}$.

A search for Higgs boson pair (HH) production with one Higgs boson decaying to two bottom quarks and the other to two W bosons are presented. The search is done using proton-proton collisions data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb⁻¹recorded by the CMS detector at the LHC from 2016 to 2018. The final states considered include at least one leptonically decaying W boson. No evidence for the presence of a signal is observed and corresponding upper limits on the HH production cross section are derived. The limit on the inclusive cross section of the nonresonant HH production, assuming that the distributions of kinematic observables are as expected in the standard model (SM), is observed (expected) to be 14 (18) times the value predicted by the SM, at 95% confidence level. The limits on the cross section are also presented as functions of various Higgs boson coupling modifiers, and anomalous Higgs boson coupling scenarios. In addition, limits are set on the resonant HH production via spin-0 and spin-2 resonances within the mass range 250–900 GeV.

A search for pair production of scalar and vector leptoquarks (LQs) each decaying to a muon and a bottom quark is performed using proton-proton collision data collected at$\sqrt{s}=13\mathrm{TeV}$with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of$138{\mathrm{fb}}^{-1}$. No excess above standard model expectation is observed. Scalar (vector) LQs with masses less than 1810 (2120) GeV are excluded at 95% confidence level, assuming a 100% branching fraction of the LQ decaying to a muon and a bottom quark. These limits represent the most stringent to date.