A
bstract
Properties of the Higgs boson are measured in the H → ZZ → 4ℓ (ℓ = e,
μ
) decay channel. A data sample of proton-proton collisions at
s
=
13
TeV, collected with the CMS detector at the LHC ...and corresponding to an integrated luminosity of 35.9 fb
−1
is used. The signal strength modifier
μ
, defined as the ratio of the observed Higgs boson rate in the H → ZZ → 4ℓ decay channel to the standard model expectation, is measured to be
μ
= 1.05
− 0.17
+ 0.19
at
m
H
= 125.09 GeV, the combined ATLAS and CMS measurement of the Higgs boson mass. The signal strength modifiers for the individual Higgs boson production modes are also measured. The cross section in the fiducial phase space defined by the requirements on lepton kinematics and event topology is measured to be 2. 92
− 0.44
+ 0.48
(stat)
− 0.24
+ 0.28
(syst)fb, which is compatible with the standard model prediction of 2.76 ± 0.14 fb. Differential cross sections are reported as a function of the transverse momentum of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet. The Higgs boson mass is measured to be
m
H
= 125.26 ± 0.21 GeV and the width is constrained using the on-shell invariant mass distribution to be Γ
H
< 1.10 GeV, at 95% confidence level.
A
bstract
A search is presented for additional neutral Higgs bosons in the
τ τ
final state in proton-proton collisions at the LHC. The search is performed in the context of the minimal supersymmetric ...extension of the standard model (MSSM), using the data collected with the CMS detector in 2016 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb
−1
. To enhance the sensitivity to neutral MSSM Higgs bosons, the search includes production of the Higgs boson in association with b quarks. No significant deviation above the expected background is observed. Model-independent limits at 95% confidence level (CL) are set on the product of the branching fraction for the decay into τ leptons and the cross section for the production via gluon fusion or in association with b quarks. These limits range from 18 pb at 90 GeV to 3.5 fb at 3.2 TeV for gluon fusion and from 15 pb (at 90 GeV) to 2.5 fb (at 3.2 TeV) for production in association with b quarks, assuming a narrow width resonance. In the
m
h
hod +
scenario these limits translate into a 95% CL exclusion of tan
β >
6 for neutral Higgs boson masses below 250 GeV, where tan
β
is the ratio of the vacuum expectation values of the neutral components of the two Higgs doublets. The 95% CL exclusion contour reaches 1.6 TeV for tan
β
= 60.
The standard model (SM) production of four top quarks (
t
t
¯
t
t
¯
) in proton–proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016–2018 data taking of ...the LHC, corresponds to an integrated luminosity of 137
fb
-
1
at a center-of-mass energy of 13
TeV
. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the
t
t
¯
t
t
¯
signal are respectively 2.6 and 2.7 standard deviations, and the
t
t
¯
t
t
¯
cross section is measured to be
12
.
6
-
5.2
+
5.8
fb
. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson,
y
t
, yielding a limit of
|
y
t
/
y
t
SM
|
<
1.7
at
95
%
confidence level, where
y
t
SM
is the SM value of
y
t
. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework,
H
^
<
0.12
. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350–470
GeV
and 350–550
GeV
for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.
A search for leptoquarks produced singly and in pairs in proton-proton collisions is presented. We consider the leptoquark (LQ) to be a scalar particle of charge −1/3e coupling to a top quark plus a ...tau lepton (tτ) or a bottom quark plus a neutrino (bν), or a vector particle of charge +2/3e, coupling to tν or bτ. These choices are motivated by models that can explain a series of anomalies observed in the measurement of B meson decays. In this analysis the signatures tτνb and tτν are probed, using data recorded by the CMS experiment at the CERN LHC at s=13 TeV and that correspond to an integrated luminosity of 137 fb−1. These signatures have not been previously explored in a dedicated search. The data are found to be in agreement with the standard model prediction. Lower limits at 95% confidence level are set on the LQ mass in the range 0.98–1.73 TeV, depending on the LQ spin and its coupling λ to a lepton and a quark, and assuming equal couplings for the two LQ decay modes considered. These are the most stringent constraints to date on the existence of leptoquarks in this scenario.
A
bstract
Results are presented from a search for the direct electroweak production of charginos and neutralinos in signatures with either two or more leptons (electrons or muons) of the same ...electric charge, or with three or more leptons, which can include up to two hadronically decaying tau leptons. The results are based on a sample of proton-proton collision data collected at
s
=
13
TeV, recorded with the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb
−1
. The observed event yields are consistent with the expectations based on the standard model. The results are interpreted in simplified models of supersymmetry describing various scenarios for the production and decay of charginos and neutralinos. Depending on the model parameters chosen, mass values between 180 GeV and 1150 GeV are excluded at 95% CL. These results significantly extend the parameter space probed for these particles in searches at the LHC. In addition, results are presented in a form suitable for alternative theoretical interpretations.
A
bstract
Measurements of Higgs boson properties in the H →
γγ
decay channel are reported. The analysis is based on data collected by the CMS experiment in proton-proton collisions at
s
=
13
TeV ...during the 2016 LHC running period, corresponding to an integrated luminosity of 35.9 fb
−1
. Allowing the Higgs mass to float, the measurement yields a signal strength relative to the standard model prediction of 1.18
− 0.14
+ 0.17
= 1.18
− 0.11
+ 0.12
(stat)
− 0.07
+ 0.09
(syst)
− 0.06
+ 0.07
(theo), which is largely insensitive to the exact Higgs mass around 125 GeV. Signal strengths associated with the different Higgs boson production mechanisms, couplings to bosons and fermions, and effective couplings to photons and gluons are also measured.
A
bstract
A search is presented for new high-mass resonances decaying into electron or muon pairs. The search uses proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the ...CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 36 fb
−1
. Observations are in agreement with standard model expectations. Upper limits on the product of a new resonance production cross section and branching fraction to dileptons are calculated in a model-independent manner. This permits the interpretation of the limits in models predicting a narrow dielectron or dimuon resonance. A scan of different intrinsic width hypotheses is performed. Limits are set on the masses of various hypothetical particles. For the
Z
S
S
M
′
Z
ψ
′
particle, which arises in the sequential standard model (superstring-inspired model), a lower mass limit of 4.50 (3.90) TeV is set at 95% confidence level. The lightest Kaluza-Klein graviton arising in the Randall-Sundrum model of extra dimensions, with coupling parameters
k
/
M
Pl
of 0.01, 0.05, and 0.10, is excluded at 95% confidence level below 2.10, 3.65, and 4.25 TeV, respectively. In a simplified model of dark matter production via a vector or axial vector mediator, limits at 95% confidence level are obtained on the masses of the dark matter particle and its mediator.
A
bstract
A statistical combination of several searches for the electroweak production of charginos and neutralinos is presented. All searches use proton-proton collision data at
s
=
13
TeV, recorded ...with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb
−1
. In addition to the combination of previous searches, a targeted analysis requiring three or more charged leptons (electrons or muons) is presented, focusing on the challenging scenario in which the difference in mass between the two least massive neutralinos is approximately equal to the mass of the Z boson. The results are interpreted in simplified models of chargino-neutralino or neutralino pair production. For chargino-neutralino production, in the case when the lightest neutralino is massless, the combination yields an observed (expected) limit at the 95% confidence level on the chargino mass of up to 650 (570) GeV, improving upon the individual analysis limits by up to 40 GeV. If the mass difference between the two least massive neutralinos is approximately equal to the mass of the Z boson in the chargino-neutralino model, the targeted search requiring three or more leptons obtains observed and expected exclusion limits of around 225 GeV on the second neutralino mass and 125 GeV on the lightest neutralino mass, improving the observed limit by about 60 GeV in both masses compared to the previous CMS result. In the neutralino pair production model, the combined observed (expected) exclusion limit on the neutralino mass extends up to 650–750 (550–750) GeV, depending on the branching fraction assumed. This extends the observed exclusion achieved in the individual analyses by up to 200 GeV. The combined result additionally excludes some intermediate gaps in the mass coverage of the individual analyses.
Differential Higgs boson (H) production cross sections are sensitive probes for physics beyond the standard model. New physics may contribute in the gluon-gluon fusion loop, the dominant Higgs boson ...production mechanism at the LHC, and manifest itself through deviations from the distributions predicted by the standard model. Combined spectra for the H→γγ, H→ZZ, and H→bb‾ decay channels and the inclusive Higgs boson production cross section are presented, based on proton-proton collision data recorded with the CMS detector at s=13TeV corresponding to an integrated luminosity of 35.9fb−1. The transverse momentum spectrum is used to place limits on the Higgs boson couplings to the top, bottom, and charm quarks, as well as its direct coupling to the gluon field. No significant deviations from the standard model are observed in any differential distribution. The measured total cross section is 61.1±6.0(stat)±3.7(syst)pb, and the precision of the measurement of the differential cross section of the Higgs boson transverse momentum is improved by about 15% with respect to the H→γγ channel alone.
Measurements of differential top quark pair tt¯\ \mathrm{t}\overline{\mathrm{t}} \ cross sections using events produced in proton-proton collisions at a centre-of-mass energy of 13 TeV containing two ...oppositely charged leptons are presented. The data were recorded by the CMS experiment at the CERN LHC in 2016 and correspond to an integrated luminosity of 35.9 fb−1. The differential cross sections are presented as functions of kinematic observables of the top quarks and their decay products, the tt¯\ \mathrm{t}\overline{\mathrm{t}} \ system, and the total number of jets in the event. The differential cross sections are defined both with particle-level objects in a fiducial phase space close to that of the detector acceptance and with parton-level top quarks in the full phase space. All results are compared with standard model predictions from Monte Carlo simulations with next-to-leading-order (NLO) accuracy in quantum chromodynamics (QCD) at matrix-element level interfaced to parton-shower simulations. Where possible, parton-level results are compared to calculations with beyond-NLO precision in QCD. Significant disagreement is observed between data and all predictions for several observables. The measurements are used to constrain the top quark chromomagnetic dipole moment in an effective field theory framework at NLO in QCD and to extract tt¯\ \mathrm{t}\overline{\mathrm{t}} \ and leptonic charge asymmetries.
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