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A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair production ( ) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400 . The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138 . The differential production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of .

A search for long-lived heavy neutrinos (N) in the decays of B mesons produced in proton-proton collisions at$$ \\sqrt{s} $$s = 13 TeV is presented. The data sample corresponds to an integrated luminosity of 41.6 fb − 1 collected in 2018 by the CMS experiment at the CERN LHC, using a dedicated data stream that enhances the number of recorded events containing B mesons. The search probes heavy neutrinos with masses in the range 1 < m N < 3 GeV and decay lengths in the range 10 − 2 < c τ N < 10 4 mm, where τ N is the N proper mean lifetime. Signal events are defined by the signature B → ℓ B NX; N → ℓ ± π ∓ , where the leptons ℓ B and ℓ can be either a muon or an electron, provided that at least one of them is a muon. The hadronic recoil system, X, is treated inclusively and is not reconstructed. No significant excess of events over the standard model background is observed in any of the ℓ ± π ∓ invariant mass distributions. Limits at 95% confidence level on the sum of the squares of the mixing amplitudes between heavy and light neutrinos, | V N | 2 , and on c τ N are obtained in different mixing scenarios for both Majorana and Dirac-like N particles. The most stringent upper limit |V N | 2 < 2.0 × 10 − 5 is obtained at m N = 1.95 GeV for the Majorana case where N mixes exclusively with muon neutrinos. The limits on |V N | 2 for masses 1 < m N < 1.7 GeV are the most stringent from a collider experiment to date.

Using proton–proton collision data corresponding to an integrated luminosity of $$140\\hbox { fb}^{-1}$$ 140 fb - 1 collected by the CMS experiment at $$\\sqrt{s}= 13\\,\\text {Te}\\hspace{-.08em}\\text {V} $$ s = 13 Te V , the $${{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{\\text {J}/\\uppsi }} {{{\\Xi }} ^{{-}}} {{\\text {K}} ^{{+}}} $$ Λ b 0 → J / ψ Ξ - K + decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the $${{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{{\\uppsi }} ({2\\textrm{S}})} {{\\Lambda }} $$ Λ b 0 → ψ ( 2 S ) Λ decay, is measured to be $$\\mathcal {B}({{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{\\text {J}/\\uppsi }} {{{\\Xi }} ^{{-}}} {{\\text {K}} ^{{+}}} )/\\mathcal {B}({{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{{\\uppsi }} ({2\\textrm{S}})} {{\\Lambda }} ) = [3.38\\pm 1.02\\pm 0.61\\pm 0.03]\\%$$ B ( Λ b 0 → J / ψ Ξ - K + ) / B ( Λ b 0 → ψ ( 2 S ) Λ ) = [ 3.38 ± 1.02 ± 0.61 ± 0.03 ] % , where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in $$\\mathcal {B}({{{\\uppsi }} ({2\\textrm{S}})} \\rightarrow {{\\text {J}/\\uppsi }} {{{\\uppi }} ^{{+}}} {{{\\uppi }} ^{{-}}} )$$ B ( ψ ( 2 S ) → J / ψ π + π - ) and $$\\mathcal {B}({{{\\Xi }} ^{{-}}} \\rightarrow {{\\Lambda }} {{{\\uppi }} ^{{-}}} )$$ B ( Ξ - → Λ π - ) .

The production of prompt $$ {\\Lambda}_{\\textrm{c}}^{+} $$ Λ c + baryons is measured via the exclusive decay channel $$ {\\Lambda}_{\\textrm{c}}^{+}\\to p{\\textrm{K}}^{-}{\\pi}^{+} $$ Λ c + → p K − π + at a center-of-mass energy per nucleon pair of 5.02 TeV, using proton-proton (pp) and lead-lead (PbPb) collision data collected by the CMS experiment at the CERN LHC. The pp and PbPb data were obtained in 2017 and 2018 with integrated luminosities of 252 and 0.607 nb − 1 , respectively. The measurements are performed within the $$ {\\Lambda}_{\\textrm{c}}^{+} $$ Λ c + rapidity interval | y | < 1 with transverse momentum ( p T ) ranges of 3–30 and 6–40 GeV/ c for pp and PbPb collisions, respectively. Compared to the yields in pp collisions scaled by the expected number of nucleon-nucleon interactions, the observed yields of $$ {\\Lambda}_{\\textrm{c}}^{+} $$ Λ c + with p T > 10 GeV/ c are strongly suppressed in PbPb collisions. The level of suppression depends significantly on the collision centrality. The $$ {\\Lambda}_{\\textrm{c}}^{+} $$ Λ c + / D 0 production ratio is similar in PbPb and pp collisions at p T > 10 GeV/ c , suggesting that the coalescence process does not play a dominant role in prompt $$ {\\Lambda}_{\\textrm{c}}^{+} $$ Λ c + baryon production at higher p T .

A search for $${\\text {Z}{}{}} {\\text {Z}{}{}} $$ ZZ and $${\\text {Z}{}{}} {\\text {H}{}{}} $$ ZH production in the $${\\text {b}{}{}} {\\bar{{\\text {b}{}{}}}{}{}} {\\text {b}{}{}} {\\bar{{\\text {b}{}{}}}{}{}} $$ bb¯bb¯ final state is presented, where H is the standard model (SM) Higgs boson. The search uses an event sample of proton-proton collisions corresponding to an integrated luminosity of 133 $$\\,\\text {fb}^{-1}$$ fb-1 collected at a center-of-mass energy of 13 $$\\,\\text {Te}\\hspace{-.08em}\\text {V}$$ TeV with the CMS detector at the CERN LHC. The analysis introduces several novel techniques for deriving and validating a multi-dimensional background model based on control samples in data. A multiclass multivariate classifier customized for the $${\\text {b}{}{}} {\\bar{{\\text {b}{}{}}}{}{}} {\\text {b}{}{}} {\\bar{{\\text {b}{}{}}}{}{}} $$ bb¯bb¯ final state is developed to derive the background model and extract the signal. The data are found to be consistent, within uncertainties, with the SM predictions. The observed (expected) upper limits at 95% confidence level are found to be 3.8 (3.8) and 5.0 (2.9) times the SM prediction for the $${\\text {Z}{}{}} {\\text {Z}{}{}} $$ ZZ and $${\\text {Z}{}{}} {\\text {H}{}{}} $$ ZH production cross sections, respectively.

A search for exotic decays of the Higgs boson ( ) with a mass of 125 to a pair of light pseudoscalars is performed in final states where one pseudoscalar decays to two quarks and the other to a pair of muons or leptons. A data sample of proton-proton collisions at corresponding to an integrated luminosity of 138 recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level ( ) on the Higgs boson branching fraction to and to via a pair of s. The limits depend on the pseudoscalar mass and are observed to be in the range (0.17-3.3)  and (1.7-7.7)  in the and final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction at 95% , with being a muon or a lepton. For different types of 2HDM+S, upper bounds on the branching fraction are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, values above 0.23 are excluded at 95% for values between 15 and 60 .

A search for exotic decays of the Higgs boson ( $$\\text {H}$$ H) with a mass of 125 $$\\,\\text {Ge}\\hspace{-.08em}\\text {V}$$ GeV to a pair of light pseudoscalars $$\\text {a}_{1} $$ a1 is performed in final states where one pseudoscalar decays to two $${\\textrm{b}}$$ b quarks and the other to a pair of muons or $$\\tau $$ τ leptons. A data sample of proton–proton collisions at $$\\sqrt{s}=13\\,\\text {Te}\\hspace{-.08em}\\text {V} $$ s=13TeV corresponding to an integrated luminosity of 138 $$\\,\\text {fb}^{-1}$$ fb-1 recorded with the CMS detector is analyzed. No statistically significant excess is observed over the standard model backgrounds. Upper limits are set at 95% confidence level ( $$\\text {CL}$$ CL) on the Higgs boson branching fraction to $$\\upmu \\upmu \\text{ b } \\text{ b } $$ μμbb and to $$\\uptau \\uptau \\text{ b } \\text{ b },$$ ττbb, via a pair of $$\\text {a}_{1} $$ a1s. The limits depend on the pseudoscalar mass $$m_{\\text {a}_{1}}$$ ma1 and are observed to be in the range (0.17–3.3)  $$\\times 10^{-4}$$ ×10-4 and (1.7–7.7)  $$\\times 10^{-2}$$ ×10-2 in the $$\\upmu \\upmu \\text{ b } \\text{ b } $$ μμbb and $$\\uptau \\uptau \\text{ b } \\text{ b } $$ ττbb final states, respectively. In the framework of models with two Higgs doublets and a complex scalar singlet (2HDM+S), the results of the two final states are combined to determine upper limits on the branching fraction $${\\mathcal {B}}(\\text {H} \\rightarrow \\text {a}_{1} \\text {a}_{1} \\rightarrow \\ell \\ell \\text{ b } \\text{ b})$$ B(H→a1a1→ℓℓbb) at 95% $$\\text {CL}$$ CL, with $$\\ell $$ ℓ being a muon or a $$\\uptau $$ τ lepton. For different types of 2HDM+S, upper bounds on the branching fraction $${\\mathcal {B}}(\\text {H} \\rightarrow \\text {a}_{1} \\text {a}_{1} )$$ B(H→a1a1) are extracted from the combination of the two channels. In most of the Type II 2HDM+S parameter space, $${\\mathcal {B}}(\\text {H} \\rightarrow \\text {a}_{1} \\text {a}_{1} )$$ B(H→a1a1) values above 0.23 are excluded at 95% $$\\text {CL}$$ CL for $$m_{\\text {a}_{1}}$$ ma1 values between 15 and 60 $$\\,\\text {Ge}\\hspace{-.08em}\\text {V}$$ GeV.

A measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum $$p_{\\textrm{T}}$$ pT. This observable is measured in multijet events over the range of $$p_{\\textrm{T}} = 360$$ pT=360– $$3170\\,\\text {Ge}\\hspace{-.08em}\\text {V} $$ 3170GeV based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 $$\\,\\text {Te}\\hspace{-.08em}\\text {V}$$ TeV, corresponding to an integrated luminosity of 134 $$\\,\\text {fb}^{-1}$$ fb-1. The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is $$\\alpha _\\textrm{S} (m_{{\\textrm{Z}}}) =0.1177 \\pm 0.0013\\, \\text {(exp)} _{-0.0073}^{+0.0116} \\,\\text {(theo)} = 0.1177_{-0.0074}^{+0.0117}$$ αS(mZ)=0.1177±0.0013(exp)-0.0073+0.0116(theo)=0.1177-0.0074+0.0117, where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of $$\\alpha _\\textrm{S}$$ αS in the $$\\,\\text {Te}\\hspace{-.08em}\\text {V}$$ TeV region shows no deviation from the expected NLO pQCD behaviour.

Using proton–proton collision data corresponding to an integrated luminosity of $$140\\hbox { fb}^{-1}$$ 140fb-1 collected by the CMS experiment at $$\\sqrt{s}= 13\\,\\text {Te}\\hspace{-.08em}\\text {V} $$ s=13TeV, the $${{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{\\text {J}/\\uppsi }} {{{\\Xi }} ^{{-}}} {{\\text {K}} ^{{+}}} $$ Λb0→J/ψΞ-K+ decay is observed for the first time, with a statistical significance exceeding 5 standard deviations. The relative branching fraction, with respect to the $${{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{{\\uppsi }} ({2\\textrm{S}})} {{\\Lambda }} $$ Λb0→ψ(2S)Λ decay, is measured to be $$\\mathcal {B}({{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{\\text {J}/\\uppsi }} {{{\\Xi }} ^{{-}}} {{\\text {K}} ^{{+}}} )/\\mathcal {B}({{{\\Lambda }} _{\\text {b}}^{{0}}} \\rightarrow {{{\\uppsi }} ({2\\textrm{S}})} {{\\Lambda }} ) = [3.38\\pm 1.02\\pm 0.61\\pm 0.03]\\%$$ B(Λb0→J/ψΞ-K+)/B(Λb0→ψ(2S)Λ)=[3.38±1.02±0.61±0.03]%, where the first uncertainty is statistical, the second is systematic, and the third is related to the uncertainties in $$\\mathcal {B}({{{\\uppsi }} ({2\\textrm{S}})} \\rightarrow {{\\text {J}/\\uppsi }} {{{\\uppi }} ^{{+}}} {{{\\uppi }} ^{{-}}} )$$ B(ψ(2S)→J/ψπ+π-) and $$\\mathcal {B}({{{\\Xi }} ^{{-}}} \\rightarrow {{\\Lambda }} {{{\\uppi }} ^{{-}}} )$$ B(Ξ-→Λπ-).

A study of the anomalous couplings of the Higgs boson to vector bosons, including $${\\textit{CP}}$$ 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 $$\\,\\text {fb}^{-1}$$ fb-1. The different-flavor dilepton $$({\\textrm{e}} {{\\upmu }})$$ (eμ) 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.