A search is presented for lepton-flavor violating decays of the Higgs boson to $\mu\tau$ and e$\tau$. The data set corresponds to an integrated luminosity of 137 fb$^{-1}$ collected at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV. No significant excess has been found, and the results are interpreted in terms of upper limits on lepton-flavor violating branching fractions of the Higgs boson. The observed (expected) upper limits on the branching fractions are, respectively, $\mathcal{B}($H $\to\mu\tau)$$\lt$ 0.15 (0.15)% and $\mathcal{B}($H$\to$e$\tau)$ $\lt$ 0.22 (0.16)% at 95% confidence level.
Observed (expected) 95% CL upper limits on $B(H\to\mu\tau)$ for each individual category and combined
Observed (expected) 95% CL upper limits on $B(H\to e\tau)$ for each individual category and combined
Summary of observed and expected upper limits at 95% CL, best fit branching fractions and corresponding constraints on Yukawa couplings for the $H\to\mu\tau$ and $H\to e\tau$ channels
Decays of the 125 GeV Higgs boson into a Z boson and a $\rho^0$(770) or $\phi$(1020) meson are searched for using proton-proton collision data collected by the CMS experiment at the LHC at $\sqrt{s} = $ 13 TeV. The analysed data set corresponds to an integrated luminosity of 137 fb$^{-1}$. Events are selected in which the Z boson decays into a pair of electrons or a pair of muons, and the $\rho$ and $\phi$ mesons decay into pairs of pions and kaons, respectively. No significant excess above the background model is observed. As different polarization states are possible for the decay products of the Z boson and $\rho$ or $\phi$ mesons, affecting the signal acceptance, scenarios in which the decays are longitudinally or transversely polarized are considered. Upper limits at the 95% confidence level on the Higgs boson branching fractions into Z$\rho$ and Z$\phi$ are determined to be 1.04-1.31% and 0.31-0.40%, respectively, where the ranges reflect the considered polarization scenarios; these values are 740-940 and 730-950 times larger than the respective standard model expectations. These results constitute the first experimental limits on the two decay channels.
Observed and expected 95% CL upper limits on B(H $\rightarrow$ Z$\rho$), for different polarizations.
Observed and expected 95% CL upper limits on B(H $\rightarrow$ Z$\phi$), for different polarizations.
This Letter presents a measurement of WZ production in 1.02 fb^-1 of pp collision data at sqrt(s) = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1 +/- 1.4(stat.) +4.1/-2.0(syst) events. The total cross section for WZ production for Z gamma^* masses within the range 66 GeV to 116 GeV is determined to be sigma_WZ^tot = 20.5 +3.1/-2.8(stat.) +1.4/-1.3(syst.) +0.9/-0.8(lumi.)pb, which is consistent with the Standard Model expectation of 17.3 +1.3/-0.8 pb. Limits on anomalous triple gauge boson couplings are extracted.
Total fiducial cross-section $WZ\to\ell\nu\ell\ell$.
A search is presented for decays of Z and Higgs bosons to a J$/\psi$ meson and a photon, with the subsequent decay of the J$/\psi$ to $\mu^+\mu^-$. The analysis uses data from proton-proton collisions with an integrated luminosity of 35.9 fb$^{-1}$ at $\sqrt{s} =$ 13 TeV collected with the CMS detector at the LHC. The observed limit on the Z $\to$ J$/\psi \gamma$ decay branching fraction, assuming that the J$/\psi$ meson is produced unpolarized, is 1.4 $\times$ 10$^{-6}$ at 95% confidence level, which corresponds to a rate higher than expected in the standard model by a factor of 15. For extreme-polarization scenarios, the observed limit changes from -13.6 to +8.6% with respect to the unpolarized scenario. The observed upper limit on the branching fraction for H $\to$ J$/\psi \gamma$ where the J$/\psi$ meson is assumed to be transversely polarized is 7.6 $\times$ 10$^{-4}$, a factor of 260 larger than the standard model prediction. The results for the Higgs boson are combined with previous data from proton-proton collisions at $\sqrt{s} =$ 8 TeV to produce an observed upper limit on the branching fraction for H $\to$ J$/\psi \gamma$ that is a factor of 220 larger than the standard model value.
Upper observed and expected limits on branching fraction of $Z (H)\rightarrow J/\psi\gamma$ decay of the $Z (H)$ boson.
A search for a Higgs boson decaying into a pair of electrons or muons and a photon is described. Higgs boson decays to a Z boson and a photon (H $\to$ Z$\gamma\to\ell\ell\gamma$, $\ell =$ e or $\mu$), or to two photons, one of which has an internal conversion into a muon pair (H $\to\gamma^{*}\gamma\to\mu\mu\gamma$) were considered. The analysis is performed using a data set recorded by the CMS experiment at the LHC from proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. No significant excess above the background prediction has been found. Limits are set on the cross section for a standard model Higgs boson decaying to opposite-sign electron or muon pairs and a photon. The observed limits on cross section times the corresponding branching fractions vary between 1.4 and 4.0 (6.1 and 11.4) times the standard model cross section for H $\to\gamma^{*}\gamma\to\mu\mu\gamma$ (H $\to$ Z$\gamma\to\ell\ell\gamma$) in the 120-130 GeV mass range of the $\ell\ell\gamma$ system. The H $\to\gamma^*\gamma\to\mu\mu\gamma$ and H $\to$ Z$\gamma\to\ell\ell\gamma$ analyses are combined for $m_\mathrm{H} =$ 125 GeV, obtaining an observed (expected) 95% confidence level upper limit of 3.9 (2.0) times the standard model cross section.
Exclusion limit, at 95% CL, on the cross section of the $H \rightarrow \gamma^{*}\gamma \rightarrow \mu\mu\gamma$ process relative to the SM prediction, as a function of the Higgs boson mass.
Exclusion limit, at 95% CL, on the cross section of the $H \rightarrow Z\gamma \rightarrow ll\gamma$ process relative to the SM prediction, as a function of the Higgs boson mass.
Exclusion limit, at 95% CL, on the cross section of the $H \rightarrow ll\gamma$ relative to the SM prediction, for an SM Higgs boson of $m_{H} = 125$ GeV. The upper limits of each analysis category, as well as their combinations, are shown.
The production of $W$ boson pairs in proton-proton collisions at $\sqrt{s}=$ 8 TeV is studied using data corresponding to 20.3 fb$^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The $W$ bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 $WW$ candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the $W$ branching fractions to leptons in order to obtain the total $WW$ production cross section, which is found to be 71.1$\pm1.1$(stat)$^{+5.7}_{-5.0}$(syst)$\pm1.4$ pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63.2$^{+1.6}_{-1.4}$(scale)$\pm1.2$(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.
Measured production cross sections of WW production in the fiducial region for different final states corresponding to different W decay channels: both W's decaying into electrons or both decaying to muon. The cross sections are defined for direct decays of the W bosons into prompt electrons or muons, intermediate decays into tau leptons are disregarded. The electrons are required to be contained within abs(eta)<2.47 and to lie outside of 1.37 < abs(eta) < 1.53, muons are required to lie within abs(eta)<2.4. The leading and subleading leptons in the events are required to have a transverse momentum above 25 and 20 GeV respectively. The transverse momentum of the vectorial sum of the neutrinos in the event should be larger than 45 GeV (PT(C=SUM(NU))). The transverse momentum of the vectorial sum of the neutrinos multiplied by the sine of azimuthal difference between lepton and the vectorial sum of the neutrinos in the event should be larger than 45 GeV if the azimuthal difference between lepton and the vectorial sum of the neutrinos is smaller than PI/2. The invariant mass of the leptons should exceed 15 GeV. The absolute difference between the invariant mass of the leptons and the mass of the Z boson should be larger than 15 GeV. Particle-level jets are defined using the anti-kT algorithm with radius of 0.4. No jets above 25 GeV and within abs(eta)<4.5 are allowed in the event. Both, resonant and non-resonant WW production processes, are included in the cross sections.
Measured production cross section of WW production in the fiducial region in case one W boson decays into a prompt electron and the other one into a prompt muon. The cross section is defined for direct decays of the W bosons into prompt electrons or muons, intermediate decays into tau leptons are disregarded. The electrons are required to be contained within abs(eta)<2.47 and to lie outside of 1.37 < abs(eta) < 1.53, muons are required to lie within abs(eta)<2.4. The leading and subleading leptons in the events are required to have a transverse momentum above 25 and 20 GeV respectively. The transverse momentum of the vectorial sum of the neutrinos in the event should be larger than 20 GeV (PT(C=SUM(NU))). The transverse momentum of the vectorial sum of the neutrinos is multiplied by the sine of the azimuthal difference between lepton and the vectorial sum of the neutrinos if their azimuthal difference is smaller than PI/2. It is required to be larger than 15 GeV. The invariant mass of the leptons should exceed 10 GeV. Particle-level jets are defined using the anti-kT algorithm with radius of 0.4. No jets above 25 GeV and within abs(eta)<4.5 are allowed in the event. Both, resonant and non-resonant WW production processes, are included in the cross sections.
Measured total production cross sections of WW production in the total phase space. Both, resonant and non-resonant WW, production are considered as signal.
A study of WZ production in proton-proton collisions at sqrt(s) = 7 TeV is presented using data corresponding to an integrated luminosity of 4.6 fb^-1 collected with the ATLAS detector at the Large Hadron Collider in 2011. In total, 317 candidates, with a background expectation of 68+/-10 events, are observed in double-leptonic decay final states with electrons, muons and missing transverse momentum. The total cross-section is determined to be sigma_WZ(tot) = 19.0+1.4/-1.3(stat.)+/-0.9(syst.)+/-0.4(lumi.) pb, consistent with the Standard Model expectation of 17.6+1.1/-1.0 pb. Limits on anomalous triple gauge boson couplings are derived using the transverse momentum spectrum of Z bosons in the selected events. The cross section is also presented as a function of Z boson transverse momentum and diboson invariant mass.
The measured fiducial cross section.
The measured total cross section.
Normalised fiducial cross section in bins of the PT of the Z0.
A search for the standard model Higgs boson produced in association with a W or a Z boson and decaying a pair of $\tau$ leptons is performed. A data sample of proton-proton collisions collected at $\sqrt{s} =$ 13 TeV by the CMS experiment at the CERN LHC is used, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. The signal strength is measured relative to the expectation for the standard model Higgs boson, yielding $\mu =$ 2.5 $^{+1.4} _{-1.3}$. These results are combined with earlier CMS measurements targeting Higgs boson decays to a pair of $\tau$ leptons, performed with the same data set in the gluon fusion and vector boson fusion production modes. The combined signal strength is $\mu =$ 1.24 $^{+0.29} _{-0.27}$ (1.00 $^{+0.24} _{-0.23}$ expected), and the observed significance is 5.5 standard deviations (4.8 expected) for a Higgs boson mass of 125 GeV.
Best fit signal strength per production mode, for mH = 125.09 GeV. The constraints from the global fit are used to extract each of the individual best fit signal strengths. The VH analyses are combined with the ggH and VBF analysis.
A search is presented for a singly produced third-generation scalar leptoquark decaying to a $\tau$ lepton and a bottom quark. Associated production of a leptoquark and a $\tau$ lepton is considered, leading to a final state with a bottom quark and two $\tau$ leptons. The search uses proton-proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector, corresponding to an integrated luminosity of 35.9 fb$^{-1}$. Upper limits are set at 95% confidence level on the production cross section of the third-generation scalar leptoquarks as a function of their mass. From a comparison of the results with the theoretical predictions, a third-generation scalar leptoquark decaying to a $\tau$ lepton and a bottom quark, assuming unit Yukawa coupling ($\lambda$), is excluded for masses below 740 GeV. Limits are also set on $\lambda$ of the hypothesized leptoquark as a function of its mass. Above $\lambda =$ 1.4, this result provides the best upper limit on the mass of a third-generation scalar leptoquark decaying to a $\tau$ lepton and a bottom quark.
The product of acceptance, efficiency, and branching fraction as a function of leptoquark (LQ) mass for the single production of LQs in each of the three channels considered: tau-tau (black solid line), mu-tau (red dashed line), and e-tau (blue dotted line). The efficiency is calculated with respect to all event selections mentioned in the paper. The uncertainty refers to statistical uncertainty only.
Observed ST distribution in the e-tau signal region, compared to the expected SM background contributions. The distribution labeled electroweak contains the contributions from W+jets, Z+jets, and diboson processes. The signal distributions for single-leptoquark (LQ) production with mass 700 GeV are overlaid to illustrate the sensitivity. For the signal normalization, lambda = 1 and beta = 1 are assumed. The background uncertainty bands represent the sum in quadrature of statistical and systematic uncertainties obtained from the fit. The lower panels show the ratio between the observed and expected events in each bin. In all plots, the horizontal and vertical error bars on the data points represent the bin widths and the Poisson uncertainties, respectively.
Observed ST distribution in the mu-tau signal region, compared to the expected SM background contributions. The distribution labeled electroweak contains the contributions from W+jets, Z+jets, and diboson processes. The signal distributions for single-leptoquark (LQ) production with mass 700 GeV are overlaid to illustrate the sensitivity. For the signal normalization, lambda = 1 and beta = 1 are assumed. The background uncertainty bands represent the sum in quadrature of statistical and systematic uncertainties obtained from the fit. The lower panels show the ratio between the observed and expected events in each bin. In all plots, the horizontal and vertical error bars on the data points represent the bin widths and the Poisson uncertainties, respectively.
Measurement of the fiducial inclusive and differential production cross sections of the Higgs boson in proton-proton collisions at $\sqrt{s} =$ 13 TeV are performed using events where the Higgs boson decays into a pair of W bosons that subsequently decay into a final state with an electron, a muon, and a pair of neutrinos. The analysis is based on data collected with the CMS detector at the LHC during 2016-2018, corresponding to an integrated luminosity of 137 fb$^{-1}$. Production cross sections are measured as a function of the transverse momentum of the Higgs boson and the associated jet multiplicity. The Higgs boson signal is extracted and simultaneously unfolded to correct for selection efficiency and resolution effects using maximum-likelihood fits to the observed distributions in data. The integrated fiducial cross section is measured to be 86.5 $\pm$ 9.5 fb, consistent with the Standard Model expectation of 82.5 $\pm$ 4.2 fb. No significant deviation from the Standard Model expectations is observed in the differential measurements.
The fiducial differential signal strength and cross section in each Higgs pT bin. Both the unregularized and regularized signal strengthes are given. For the regularized case the uncertainty breakdown is given in terms of statistical (stat), experimental (exp), theoretical uncertainties on the background (bkg) and on the signal (sig), and the luminosity uncertainty (lumi). The regularization estimated bias (bias) is also given. The fiducial cross section and its full uncertainty in each bin are also given. The last bin is inclusive.
The correlation matrix for the ptH measurements, both for the unregularized and regularized fits. The last bin is inclusive.
The fiducial differential signal strength and cross section in each njet bin. The uncertainty breakdown is given in terms of statistical (stat), experimental (exp), theoretical uncertainties on the background (bkg) and on the signal (sig), and the luminosity uncertainty (lumi). The fiducial cross section and its full uncertainty in each bin are also given. The last bin is inclusive.
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