Dijet production in PbPb collisions at a nucleon–nucleon center-of-mass energy of 2.76 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 150 ...μb−1 is analyzed. Jets are reconstructed using combined information from tracking and calorimetry, using the anti-kT algorithm with R=0.3. The dijet momentum balance and angular correlations are studied as a function of collision centrality and leading jet transverse momentum. For the most peripheral PbPb collisions, good agreement of the dijet momentum balance distributions with pp data and reference calculations at the same collision energy is found, while more central collisions show a strong imbalance of leading and subleading jet transverse momenta attributed to the jet-quenching effect. The dijets in central collisions are found to be more unbalanced than the reference, for leading jet transverse momenta up to the highest values studied.
A search for heavy, right-handed neutrinos,
N
ℓ
(
ℓ
=
e
,
μ
), and right-handed
W
R
bosons, which arise in the left-right symmetric extensions of the standard model, has been performed by the CMS ...experiment. The search was based on a sample of two lepton plus two jet events collected in proton–proton collisions at a center-of-mass energy of 8
TeV
corresponding to an integrated luminosity of 19.7
fb
-
1
. For models with strict left-right symmetry, and assuming only one
N
ℓ
flavor contributes significantly to the
W
R
decay width, the region in the two-dimensional
(
M
W
R
,
M
N
ℓ
)
mass plane excluded at a 95 % confidence level extends to approximately
M
W
R
=
3.0
TeV
and covers a large range of neutrino masses below the
W
R
boson mass, depending on the value of
M
W
R
. This search significantly extends the
(
M
W
R
,
M
N
ℓ
)
exclusion region beyond previous results.
A search for new phenomena is performed using events with jets and significant transverse momentum imbalance, as inferred through the
M
T
2
variable. The results are based on a sample of ...proton–proton collisions collected in 2016 at a center-of-mass energy of 13
TeV
with the CMS detector and corresponding to an integrated luminosity of 35.9
fb
-1
. No excess event yield is observed above the predicted standard model background, and the results are interpreted as exclusion limits at 95% confidence level on the masses of predicted particles in a variety of simplified models of
R
-parity conserving supersymmetry. Depending on the details of the model, 95% confidence level lower limits on the gluino (light-flavor squark) masses are placed up to 2025 (1550)
GeV
. Mass limits as high as 1070 (1175)
GeV
are set on the masses of top (bottom) squarks. Information is provided to enable re-interpretation of these results, including model-independent limits on the number of non-standard model events for a set of simplified, inclusive search regions.
A measurement is presented of the cross section for the electroweak production of a Z boson and a photon in association with two jets in proton–proton collisions at s=8 TeV. The Z bosons are ...identified through their decays to electron or muon pairs. The measurement is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 fb−1. The electroweak contribution has a significance of 3.0 standard deviations, and the measured fiducial cross section is 1.86−0.75+0.90(stat)−0.26+0.34(syst)±0.05(lumi) fb, while the summed electroweak and quantum chromodynamic total cross section in the same region is observed to be 5.94−1.35+1.53(stat)−0.37+0.43(syst)±0.13(lumi) fb. Both measurements are consistent with the leading-order standard model predictions. Limits on anomalous quartic gauge couplings are set based on the Zγ mass distribution.
A statistical combination of searches is presented for massive resonances decaying to WW, WZ, ZZ, WH, and ZH boson pairs in proton–proton collision data collected by the CMS experiment at the LHC. ...The data were taken at centre-of-mass energies of 8 and 13 TeV, corresponding to respective integrated luminosities of 19.7 and up to 2.7 fb−1. The results are interpreted in the context of heavy vector triplet and singlet models that mimic properties of composite-Higgs models predicting W′ and Z′ bosons decaying to WZ, WW, WH, and ZH bosons. A model with a bulk graviton that decays into WW and ZZ is also considered. This is the first combined search for WW, WZ, WH, and ZH resonances and yields lower limits on masses at 95% confidence level for W′ and Z′ singlets at 2.3 TeV, and for a triplet at 2.4 TeV. The limits on the production cross section of a narrow bulk graviton resonance with the curvature scale of the warped extra dimension k˜=0.5, in the mass range of 0.6 to 4.0 TeV, are the most stringent published to date.
A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks is performed in proton–proton collisions at a center-of-mass energy of 13
Te
collected with the ...CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 35.9
fb
-
1
. The signal is characterized by a large missing transverse momentum recoiling against a bottom quark–antiquark system that has a large Lorentz boost. The number of events observed in the data is consistent with the standard model background prediction. Results are interpreted in terms of limits both on parameters of the type-2 two-Higgs doublet model extended by an additional light pseudoscalar boson
a
(2HDM+
a
) and on parameters of a baryonic
Z
′
simplified model. The 2HDM+
a
model is tested experimentally for the first time. For the baryonic
Z
′
model, the presented results constitute the most stringent constraints to date.
A search is presented for the single production of vector-like quarks in proton–proton collisions at
s
=
13
TeV
. The data, corresponding to an integrated luminosity of 35.9
fb
-
1
, were recorded ...with the CMS experiment at the LHC. The analysis focuses on the vector-like quark decay into a top quark and a
W
boson, with one muon or electron in the final state. The mass of the vector-like quark candidate is reconstructed from hadronic jets, the lepton, and the missing transverse momentum. Methods for the identification of
b
quarks and of highly Lorentz boosted hadronically decaying top quarks and
W
bosons are exploited in this search. No significant deviation from the standard model background expectation is observed. Exclusion limits at 95% confidence level are set on the product of the production cross section and branching fraction as a function of the vector-like quark mass, which range from 0.3 to 0.03
pb
for vector-like quark masses of 700 to 2000
GeV
. Mass exclusion limits up to 1660
GeV
are obtained, depending on the vector-like quark type, coupling, and decay width. These represent the most stringent exclusion limits for the single production of vector-like quarks in this channel.
A
bstract
A search is reported for massive resonances decaying into a quark and a vector boson (W or Z), or two vector bosons (WW, WZ, or ZZ). The analysis is performed on an inclusive sample of ...multijet events corresponding to an integrated luminosity of 19.7 fb
−1
, collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. The search uses novel jet-substructure identification techniques that provide sensitivity to the presence of highly boosted vector bosons decaying into a pair of quarks. Exclusion limits are set at a confidence level of 95% on the production of: (i) excited quark resonances q
*
decaying to qW and qZ for masses less than 3.2 TeV and 2.9 TeV, respectively, (ii) a Randall-Sundrum graviton G
RS
decaying into WW for masses below 1.2 TeV, and (iii) a heavy partner of the W boson W
′
decaying into WZ for masses less than 1.7 TeV. For the first time mass limits are set on W
′
→ WZ and G
RS
→ WW in the all-jets final state. The mass limits on q
*
→ qW, q
*
→ qZ, W
′
→ WZ, G
RS
→ WW are the most stringent to date. A model with a “bulk” graviton G
bulk
that decays into WW or ZZ bosons is also studied.
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