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CMS Collaboration

Publications and source records attributed to CMS Collaboration.

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arXiv2022

Search for charged-lepton flavor violation in top quark production and decay in pp collisions at $\sqrt{s} =$ 13 TeV

Results are presented from a search for charged-lepton flavor violating (CLFV) interactions in top quark production and decay in pp collisions at a center-of-mass energy of 13 TeV. The events are required to contain one oppositely charged electron-muon pair in the final state, along with at least one jet identified as originating from a bottom quark. The data correspond to an integrated luminosity of 138 fb$^{-1}$, collected by the CMS experiment at the LHC. This analysis includes both the production (q $\to$ e$μ$t) and decay (t $\to$ e$μ$q) modes of the top quark through CLFV interactions, with q referring to a u or c quark. These interactions are parametrized using an effective field theory approach. With no significant excess over the standard model expectation, the results are interpreted in terms of vector-, scalar-, and tensor-like CLFV four-fermion effective interactions. Finally, observed exclusion limits are set at 95% confidence levels on the respective branching fractions of a top quark to an e$μ$ pair and an up (charm) quark of 0.13 $\times$ 10$^{-6}$ (1.31 $\times$ 10$^{-6}$), 0.07 $\times$ 10$^{-6}$ (0.89 $\times$ 10$^{-6}$), and 0.25 $\times$ 10$^{-6}$ (2.59 $\times$ 10$^{-6}$) for vector, scalar, and tensor CLFV interactions, respectively.

hep-ex↗

arXiv2022

Strategies and performance of the CMS silicon tracker alignment during LHC Run 2

The strategies for and the performance of the CMS silicon tracking system alignment during the 2015-2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios.

physics.ins-det↗

arXiv2022

Analysis of the CP structure of the Yukawa coupling between the Higgs boson and $τ$ leptons in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and $τ$ leptons is presented. The measurement is based on data collected in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$. The analysis uses the angular correlation between the decay planes of $τ$ leptons produced in Higgs boson decays. The effective mixing angle between CP-even and CP-odd $τ$ Yukawa couplings is found to be $-$1 $\pm$ 19$^\circ$, compared to an expected value of 0 $\pm$ 21$^\circ$ at the 68.3% confidence level. The data disfavour the pure CP-odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson.

hep-ex↗

arXiv2022

Measurement of the production cross section for Z + b jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The measurement of the cross section for the production of a Z boson, decaying to dielectrons or dimuons, in association with at least one bottom quark jet are performed with proton-proton collision data at $\sqrt{s} =$ 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb$^{-1}$, collected by the CMS experiment at the LHC during 2016-2018. The integrated cross sections for Z + $\ge$ 1 b jet and Z + $\ge$ 2 b jets are reported for the electron, muon, and combined channels. The fiducial cross sections in the combined channel are 6.52 $\pm$ 0.04 (stat) $\pm$ 0.40 (syst) $\pm$ 0.14 (theo) pb for Z + $\ge$ 1 b jet and 0.65 $\pm$ 0.03 (stat) $\pm$ 0.07 (syst) $\pm$ 0.02 (theo) pb for Z + $\ge$ 2 b jets. The differential cross section distributions are measured as functions of various kinematic observables that are useful for precision tests of perturbative quantum chromodynamics predictions. The ratios of integrated and differential cross sections for Z + $\ge$ 2 b jets and Z + $\ge$ 1 b jet processes are also determined. The value of the integrated cross section ratio measured in the combined channel is 0.100 $\pm$ 0.005 (stat) $\pm$ 0.007 (syst) $\pm$ 0.003 (theo). All measurements are compared with predictions from various event generators.

hep-ex↗

arXiv2022

Observation of B$^0$ $\to$ $ψ$(2S)K$^0_\mathrm{S}π^+π^-$ and B$^0_\mathrm{S}$ $\to$ $ψ$(2S)K$^0_\mathrm{S}$ decays

Using a data sample of $\sqrt{s} =$ 13 TeV proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of 103 fb$^{-1}$, the B$^0$ $\to$ $ψ$(2S)K$^0_\mathrm{S}$ and B$^0_\mathrm{S}$ $\to$ $ψ$(2S)K$^0_\mathrm{S}π^+π^-$ decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to $\mathcal{B}$(B$^0_\mathrm{S}$ $\to$ $ψ$(2S)K$^0_\mathrm{S}$) / $\mathcal{B}$(B$^0$ $\to$ $ψ$(2S)K$^0_\mathrm{S}$) = (3.33 $\pm$ 0.69 (stat) $\pm$ 0.11 (syst) $\pm$ 0.34 ($f_\mathrm{s} / f_\mathrm{d}$)) $\times$ 10$^{-2}$ and $\mathcal{B}$(B$^0$ $\to$ $ψ$(2S)K$^0_\mathrm{S}π^+π^-$) / $\mathcal{B}$(B$^0$ $\to$ $ψ$(2S)K$^0_\mathrm{S}$) = 0.480 $\pm$ 0.013 (stat) $\pm$ 0.032 (syst), where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of B$^0_\mathrm{s}$ and B$^0$ mesons, $f_\mathrm{s} / f_\mathrm{d}$.

hep-ex↗

arXiv2022

Search for electroweak production of charginos and neutralinos in all hadronic final states at the CMS experiment

The results from a search for chargino-neutralino or chargino pair production via electroweak interactions are summarized. The results are based on a sample of $\sqrt{s}=13~\mathrm{TeV}$ proton-proton collisions from the LHC, recorded with the CMS detector~\cite{cms} and corresponding to an integrated luminosity of $137~\mathrm{fb}^{-1}$. The search considers final states with large missing transverse momentum and pairs of hadronically decaying bosons WW, WZ, and WH, which are identified using novel algorithms. No significant excess of events is observed relative to the expectation from the standard model. Limits at the $95\%$ confidence level are placed on the cross-section for production of mass-degenerate wino-like superpartners of SU(2) gauge bosons, $\widetildeχ_{1}^{\pm}$/$\widetildeχ_{2}^{0}$. In the limit of nearly-massless neutralinos $\widetildeχ_{1}^{0}$, $\widetildeχ_{1}^{\pm}$ and $\widetildeχ_{2}^{0}$ with masses up to 870 and $960~\mathrm{GeV}$ are excluded for $\widetildeχ_{2}^{0}\to\mathrm{Z}\widetildeχ_{1}^{0}$ and $\widetildeχ_{2}^{0}\to\mathrm{H}\widetildeχ_{1}^{0}$, respectively. Interpretations for other models are also presented.

hep-ex↗

arXiv2022

Search for invisible decays of the Higgs boson produced via vector boson fusion in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A search for invisible decays of the Higgs boson produced via vector boson fusion (VBF) has been performed with 101 fb$^{-1}$ of proton-proton collisions delivered by the LHC at $\sqrt{s} =$ 13 TeV and collected by the CMS detector in 2017 and 2018. The sensitivity to the VBF production mechanism is enhanced by constructing two analysis categories, one based on missing transverse momentum, and a second based on the properties of jets. In addition to control regions with Z and W boson candidate events, a highly populated control region, based on the production of a photon in association with jets, is used to constrain the dominant irreducible background from the invisible decay of a Z boson produced in association with jets. The results of this search are combined with all previous measurements in the VBF topology, based on data collected in 2012 (at $\sqrt{s} =$ 8 TeV), 2015, and 2016, corresponding to integrated luminosities of 19.7, 2.3, and 36.3 fb$^{-1}$, respectively. The observed (expected) upper limit on the invisible branching fraction of the Higgs boson is found to be 0.18 (0.10) at the 95% confidence level, assuming the standard model production cross section. The results are also interpreted in the context of Higgs-portal models.

hep-ex↗

arXiv2022

Search for single production of a vector-like T quark decaying to a top quark and a Z boson in the final state with jets and missing transverse momentum at $\sqrt{s} =$ 13 TeV

A search is presented for single production of a vector-like T quark with charge 2/3 $e$, in the decay channel featuring a top quark and a Z boson, with the top quark decaying hadronically and the Z boson decaying to neutrinos. The search uses data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$ recorded at the CERN LHC in 2016-2018. The search is sensitive to a T quark mass between 0.6 and 1.8 TeV with decay widths ranging from negligibly small up to 30% of the T quark mass. Reconstruction strategies for the top quark are based on the degree of Lorentz boosting of its final state. At 95% confidence level, the upper limit on the product of the cross section and branching fraction for a T quark of small decay width varies between 15 and 602 fb, depending on its mass. For a T quark with decay widths between 10 and 30% of its mass, this upper limit ranges between 16 and 836 fb. For most of the studied range, the results provide the best limits to date. This is the first search for single T quark production based on the full Run 2 data set of the LHC.

hep-ex↗

arXiv2022

Measurement of the inclusive and differential $\mathrm{t\bar{t}}γ$ cross sections in the dilepton channel and effective field theory interpretation in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions in the decay channel with two oppositely charged leptons (e$^\pmμ^\mp$, e$^+$e$^-$, or $μ^+μ^-$). The measurement is performed using 138 fb$^{-1}$ of proton-proton collision data recorded by the CMS experiment at $\sqrt{s} =$ 13 TeV during the 2016-2018 data-taking period of the CERN LHC. A fiducial phase space is defined such that photons radiated by initial-state particles, top quarks, or any of their decay products are included. An inclusive cross section of 175.2 $\pm$ 2.5 (stat) $\pm$ 6.3 (syst) fb is measured in a signal region with at least one jet coming from the hadronization of a bottom quark and exactly one photon with transverse momentum above 20 GeV. Differential cross sections are measured as functions of several kinematic observables of the photon, leptons, and jets, and compared to standard model predictions. The measurements are also interpreted in the standard model effective field theory framework, and limits are found on the relevant Wilson coefficients from these results alone and in combination with a previous CMS measurement of the $\mathrm{t\bar{t}}γ$ production process using the lepton+jets final state.

hep-ex↗

arXiv2022

Search for heavy resonances decaying to a pair of Lorentz-boosted Higgs bosons in final states with leptons and a bottom quark pair at $\sqrt{s} =$ 13 TeV

A search for new heavy resonances decaying to a pair of Higgs bosons (HH) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. Data were collected with the CMS detector at the LHC in 2016-2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. Resonances with a mass between 0.8 and 4.5 TeV are considered using events in which one Higgs boson decays into a bottom quark pair and the other into final states with either one or two charged leptons. Specifically, the single-lepton decay channel HH $\to$ $\mathrm{b\bar{b}}$WW$^*$ $\to$ $\mathrm{b\bar{b}}\ellνq\bar{q}'$ and the dilepton decay channels HH $\to$ $\mathrm{b\bar{b}}$WW$^*$ $\to$ $\mathrm{b\bar{b}}\ellν\ellν$ and HH $\to$ $\mathrm{b\bar{b}}ττ$ $\to$ $\mathrm{b\bar{b}}\ellνν\ellνν$ are examined, where $\ell$ in the final state corresponds to an electron or muon. The signal is extracted using a two-dimensional maximum likelihood fit of the H $\to$ $\mathrm{b\bar{b}}$ jet mass and HH invariant mass distributions. No significant excess above the standard model expectation is observed in data. Model-independent exclusion limits are placed on the product of the cross section and branching fraction for narrow spin-0 and spin-2 massive bosons decaying to HH. The results are also interpreted in the context of radion and bulk graviton production in models with a warped extra spatial dimension. The results provide the most stringent limits to date for X $\to$ HH signatures with final-state leptons and at some masses provide the most sensitive limits of all X $\to$ HH searches.

hep-ex↗

arXiv2022

Search for higgsinos decaying to two Higgs bosons and missing transverse momentum in proton-proton collisions at $\sqrt{s} =$ 13 TeV

Results are presented from a search for physics beyond the standard model in proton-proton collisions at $\sqrt{s} =$ 13 TeV in channels with two Higgs bosons, each decaying via the process H $\to$ $\mathrm{b\bar{b}}$, and large missing transverse momentum. The search uses a data sample corresponding to an integrated luminosity of 137 fb$^{-1}$ collected by the CMS experiment at the CERN LHC. The search is motivated by models of supersymmetry that predict the production of neutralinos, the neutral partners of the electroweak gauge and Higgs bosons. The observed event yields in the signal regions are found to be consistent with the standard model background expectations. The results are interpreted using simplified models of supersymmetry. For the electroweak production of nearly mass-degenerate higgsinos, each of whose decay chains yields a neutralino ($\tildeχ^0_1$) that in turn decays to a massless goldstino and a Higgs boson, $\tildeχ^0_1$ masses in the range 175 to 1025 GeV are excluded at 95% confidence level. For the strong production of gluino pairs decaying via a slightly lighter $\tildeχ^0_2$ to H and a light $\tildeχ^0_1$, gluino masses below 2330 GeV are excluded.

hep-ex↗

arXiv2022

Search for a right-handed W boson and a heavy neutrino in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A search is presented for a right-handed W boson (W$_\mathrm{R}$) and a heavy neutrino (N), in a final state consisting of two same-flavor leptons (ee or $μμ$) and two quarks. The search is performed with the CMS experiment at the CERN LHC using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 138 fb$^{-1}$. The search covers two regions of phase space, one where the decay products of the heavy neutrino are merged into a single large-area jet, and one where the decay products are well separated. The expected signal is characterized by an excess in the invariant mass distribution of the final-state objects. No significant excess over the standard model background expectations is observed. The observations are interpreted as upper limits on the product of W$_\mathrm{R}$ production cross sections and branching fractions assuming that couplings are identical to those of the standard model W boson. For N masses $m_\mathrm{N}$ equal to half the W$_\mathrm{R}$ mass $m_\mathrm{W_R}$ ($m_\mathrm{N}$ = 0.2 TeV), $m_\mathrm{W_R}$ is excluded at 95% confidence level up to 4.7 (4.8) and 5.0 (5.4) TeV for the electron and muon channels, respectively. This analysis provides the most stringent limits on the W$_\mathrm{R}$ mass to date.

hep-ex↗

arXiv2022

Measurement of the inclusive $\mathrm{t\bar{t}}$ production cross section in proton-proton collisions at $\sqrt{s} =$ 5.02 TeV

The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb$^{-1}$. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 $\pm$ 5.0 (stat) $\pm$ 2.8 (syst) $\pm$ 1.1 (lumi) pb. To reduce the statistical uncertainty, a combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb$^{-1}$, is then performed. The resulting measured value is 63.0 $\pm$ 4.1 (stat) $\pm$ 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8 $^{+2.9}_{-3.1}$ pb.

hep-ex↗

arXiv2022

Search for electroweak production of charginos and neutralinos in proton-proton collisions at $\sqrt{s} = $ 13 TeV

A direct search for electroweak production of charginos and neutralinos is presented. Events with three or four leptons, with up to two hadronically decaying $τ$ leptons, or two same-sign light leptons are analyzed. The data sample consists of 137 fb$^{-1}$ of proton-proton collisions with a center of mass energy of 13 TeV, recorded with the CMS detector at the LHC. The results are interpreted in terms of several simplified models. These represent a broad range of production and decay scenarios for charginos and neutralinos. A parametric neural network is used to target several of the models with large backgrounds. In addition, results using orthogonal search regions are provided for all the models, simplifying alternative theoretical interpretations of the results. Depending on the model hypotheses, charginos and neutralinos with masses up to values between 300 and 1450 GeV are excluded at 95% confidence level.

hep-ex↗

arXiv2022

Precision measurement of the W boson decay branching fractions in proton-proton collisions at $\sqrt{s} =$ 13 TeV

The leptonic and inclusive hadronic decay branching fractions of the W boson are measured using proton-proton collision data collected at $\sqrt{s} =$ 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Events characterized by the production of one or two W bosons are selected and categorized based on the multiplicity and flavor of reconstructed leptons, the number of jets, and the number of jets identified as originating from the hadronization of b quarks. A binned maximum likelihood estimate of the W boson branching fractions is performed simultaneously in each event category. The measured branching fractions of the W boson decaying into electron, muon, and tau lepton final states are (10.83 $\pm$ 0.10)%, (10.94 $\pm$ 0.08)%, and (10.77 $\pm$ 0.21)%, respectively, consistent with lepton flavor universality for the weak interaction. The average leptonic and inclusive hadronic decay branching fractions are estimated to be (10.89 $\pm$ 0.08)% and (67.32 $\pm$ 0.23)%, respectively. Based on the hadronic branching fraction, three standard model quantities are subsequently derived: the sum of squared elements in the first two rows of the Cabibbo-Kobayashi-Maskawa (CKM) matrix $\sum_{ij}\vert V_{ij}\vert^{2}$ = 1.984 $\pm$ 0.021, the CKM element $\vert V_\mathrm{cs}\vert$ = 0.967 $\pm$ 0.011, and the strong coupling constant at the W boson mass scale, $α_\mathrm{S}(m^2_\mathrm{W})$ = 0.095 $\pm$ 0.033.

hep-ex↗

arXiv2022

Study of dijet events with large rapidity separation in proton-proton collisions at $\sqrt{s} =$ 2.76 TeV

The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at $\sqrt{s} =$ 2.76 TeV for jets with transverse momentum $p_\mathrm{T}$ $\gt$ 35 GeV and rapidity $\vert y\vert$ $\lt$ 4.7. Various dijet production cross section ratios are also measured. A veto on additional jets with $p_\mathrm{T}$ $\gt$ 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation.

hep-ex↗

arXiv2022

Search for heavy resonances decaying to ZZ or ZW and axion-like particles mediating nonresonant ZZ or ZH production at $\sqrt{s} =$ 13 TeV

A search has been performed for heavy resonances decaying to ZZ or ZW and for axion-like particles (ALPs) mediating nonresonant ZZ or ZH production, in final states with two charged leptons ($\ell$ = e, $μ$) produced by the decay of a Z boson, and two quarks produced by the decay of a Z, W, or Higgs boson H. The analysis is sensitive to resonances with masses in the range 450 to 2000 GeV. Two categories are defined corresponding to the merged or resolved reconstruction of the hadronically decaying boson. The search is based on data collected during 2016-2018 by the CMS experiment at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. No significant excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-2 and spin-1 resonances are derived as functions of the resonance mass, and exclusion limits on the production of bulk graviton particles and W$'$ bosons are calculated in the framework of the warped extra dimensions and heavy vector triplet models, respectively. In addition, upper limits on the ALP-mediated diboson production cross section and ALP couplings to standard model particles are obtained in the framework of linear and chiral effective field theories. These are the first limits on nonresonant ALP-mediated ZZ and ZH production obtained by the LHC experiments.

hep-ex↗

arXiv2022

Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at $\sqrt{s} =$ 13 TeV collected in the three-year period 2016-2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb$^{-1}$. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on $\widetildeχ^0_2 / \widetildeχ^\pm_1$ masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205 (150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter $μ$ up to 180 GeV with the bino mass parameter $M_1$ at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.

hep-ex↗