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
Measurements are presented of the differential cross sections for Z bosons produced in proton-proton collisions at
s
= 13 TeV and decaying to muons and electrons. The data analyzed were ...collected in 2016 with the CMS detector at the LHC and correspond to an integrated luminosity of 35
.
9 fb
−
1
. The measured fiducial inclusive product of cross section and branching fraction agrees with next-to-next-to-leading order quantum chromodynamics calculations. Differential cross sections of the transverse momentum
p
T
, the optimized angular variable
ϕ
η
∗
, and the rapidity of lepton pairs are measured. The data are corrected for detector effects and compared to theoretical predictions using fixed order, resummed, and parton shower calculations. The uncertainties of the measured normalized cross sections are smaller than 0.5% for
ϕ
η
∗
<
0
.
5 and for
p
T
Z
<
50 GeV.
A
bstract
A search is presented for pair production of heavy vector-like T and B quarks in proton-proton collisions at
s
=
13
TeV. The data sample corresponds to an integrated luminosity of 35.9 fb
...−1
, collected with the CMS detector at the CERN LHC in 2016. Pair production of T quarks would result in a wide range of final states, since vector-like T quarks of charge 2
e
/3 are predicted to decay to bW, tZ, and tH. Likewise, vector-like B quarks are predicted to decay to tW, bZ, and bH. Three channels are considered, corresponding to final states with a single lepton, two leptons with the same sign of the electric charge, or at least three leptons. The results exclude T quarks with masses below 1140–1300 GeV and B quarks with masses below 910–1240 GeV for various branching fraction combinations, extending the reach of previous CMS searches by 200–600 GeV.
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.
A
bstract
A measurement is performed of the cross section of top quark pair production in association with a W or Z boson using proton-proton collisions at a center-of-mass energy of 13 TeV at the ...LHC. The data sample corresponds to an integrated luminosity of 35.9 fb
−1
, collected by the CMS experiment in 2016. The measurement is performed in the same-sign dilepton, three- and four-lepton final states. The production cross sections are measured to be
σ
t
t
¯
W
=
0.77
−
0.11
+
0.12
stat
−
0.12
+
0.13
syst
p
b
and
σ
t
t
¯
Z
=
0.99
−
0.08
+
0.09
stat
−
0.10
+
0.12
syst
p
b
. The expected (observed) signal significance for the
t
t
¯
W
production in same-sign dilepton channel is found to be 4.5 (5.3) standard deviations, while for the
t
t
¯
Z
production in three- and four-lepton channels both the expected and the observed significances are found to be in excess of 5 standard deviations. The results are in agreement with the standard model predictions and are used to constrain the Wilson coefficients for eight dimension-six operators describing new interactions that would modify
t
t
¯
W
and
t
t
¯
Z
production.
The nuclear modification factors of
and
mesons are measured in
collisions at a centre-of-mass energy per nucleon pair of
. The analysis is based on
and
data samples collected by CMS at the LHC in ...2015, corresponding to integrated luminosities of 464
and 28
, respectively. The measurements are performed in the dimuon rapidity range of
as a function of centrality, rapidity, and transverse momentum (
) from
in the most forward region and up to 50
. Both prompt and nonprompt (coming from b hadron decays)
mesons are observed to be increasingly suppressed with centrality, with a magnitude similar to the one observed at
for the two
meson components. No dependence on rapidity is observed for either prompt or nonprompt
mesons. An indication of a lower prompt
meson suppression at
is seen with respect to that observed at intermediate
. The prompt
meson yield is found to be more suppressed than that of the prompt
mesons in the entire
range.
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