Exclusive
photoproduction is measured for the first time in ultraperipheral pPb collisions at
with the CMS detector. The cross section
is
b at
for photon-proton centre-of-mass energies
between 29 and
.... The differential cross section
is measured in the interval
as a function of
, where
is the squared four-momentum transfer at the proton vertex. The results are compared with previous measurements and theoretical predictions. The measured cross section
has a power-law dependence on the photon-proton centre-of-mass, consistent with electron-proton collision measurements performed at HERA. The
dependence of the exponential slope of the differential cross section
is also measured.
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Observation of tt[over ¯]H Production Adam, W; D'Hondt, J; Brun, H ...
Physical review letters,
2018-Jun-08, 20180608, Letnik:
120, Številka:
23
Journal Article
Recenzirano
The observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of ...sqrts=7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9 fb^{-1}, respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26_{-0.26}^{+0.31}.
A measurement of the top quark-antiquark pair production cross section Formula omitted in proton-proton collisions at a centre-of-mass energy of 13 Formula omitted is presented. The data correspond ...to an integrated luminosity of Formula omitted, recorded by the CMS experiment at the CERN LHC in 2016. Dilepton events ( Formula omitted Formula omitted Formula omitted Formula omitted, Formula omitted, Formula omitted) are selected and the cross section is measured from a likelihood fit. For a top quark mass parameter in the simulation of Formula omitted the fit yields a measured cross section Formula omitted, in agreement with the expectation from the standard model calculation at next-to-next-to-leading order. A simultaneous fit of the cross section and the top quark mass parameter in the powheg simulation is performed. The measured value of Formula omitted is in good agreement with previous measurements. The resulting cross section is used, together with the theoretical prediction, to determine the top quark mass and to extract a value of the strong coupling constant with different sets of parton distribution functions.
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A search for the pair production of heavy vector-like partners Formula omitted and Formula omitted of the top and bottom quarks has been performed by the CMS experiment at the CERN LHC using ...proton-proton collisions at Formula omitted. The data sample was collected in 2016 and corresponds to an integrated luminosity of 35.9 Formula omitted. Final states studied for Formula omitted production include those where one of the Formula omitted quarks decays via Formula omitted and the other via Formula omitted, Formula omitted, or Formula omitted, where Formula omitted is a Higgs boson. For the Formula omitted case, final states include those where one of the Formula omitted quarks decays via Formula omitted and the other Formula omitted, Formula omitted, or Formula omitted. Events with two oppositely charged electrons or muons, consistent with coming from the decay of a Formula omitted boson, and jets are investigated. The number of observed events is consistent with standard model background estimations. Lower limits at 95% confidence level are placed on the masses of the Formula omitted and Formula omitted quarks for a range of branching fractions. Assuming 100% branching fractions for Formula omitted, and Formula omitted, Formula omitted and Formula omitted quark mass values below 1280 and 1130 Formula omitted, respectively, are excluded.
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The first observation of the production of a W boson with a single charm quark (c) jet in ppover ¯ collisions at √s=1.96 TeV is reported. The analysis uses data corresponding to 4.3 fb(-1), ...recorded with the CDF II detector at the Fermilab Tevatron. Charm quark candidates are selected through the identification of an electron or muon from charm-hadron semileptonic decay within a hadronic jet, and a Wc signal is observed with a significance of 5.7 standard deviations. The production cross section σ(Wc)(p(Tc)>20 GeV/c,|η(c)|<1.5)×B(W→ℓν) is measured to be 13.6(-3.1)(+3.4) pb and is in agreement with theoretical expectations. From this result the magnitude of the quark-mixing matrix element V(cs) is derived, |V(cs)|=1.08±0.16 along with a lower limit of |V(cs)|>0.71 at the 95% confidence level, assuming that the Wc production through c to s quark coupling is dominant.
We present a search for the standard model Higgs boson produced in association with a Z boson in data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of ...9.45 fb(-1). In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electron or muon pairs, we set 95% credibility level upper limits on the ZH production cross section times the H→bb branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125 GeV/c(2), we observe (expect) a limit of 7.1 (3.9) times the standard model value.
Measurements are presented of associated production of a
boson and a charm quark (
) in proton-proton collisions at a center-of-mass energy of 13
. The data correspond to an integrated luminosity of ...35.7
collected by the CMS experiment at the CERN LHC. The
bosons are identified by their decay into a muon and a neutrino. The charm quarks are tagged via the full reconstruction of
mesons that decay via
. A cross section is measured in the fiducial region defined by the muon transverse momentum
, muon pseudorapidity
, and charm quark transverse momentum
. The inclusive cross section for this kinematic range is
. The cross section is also measured differentially as a function of the pseudorapidity of the muon from the
boson decay. These measurements are compared with theoretical predictions and are used to probe the strange quark content of the proton.
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This Letter reports a measurement of the cross section for producing pairs of central prompt isolated photons in proton-antiproton collisions at a total energy sqrts = 1.96 TeV using data ...corresponding to 9.5 fb(-1) integrated luminosity collected with the CDF II detector at the Fermilab Tevatron. The measured differential cross section is compared to three calculations derived from the theory of strong interactions. These include a prediction based on a leading order matrix element calculation merged with a parton shower model, a next-to-leading order calculation, and a next-to-next-to-leading order calculation. The first and last calculations reproduce most aspects of the data, thus showing the importance of higher-order contributions for understanding the theory of strong interaction and improving measurements of the Higgs boson and searches for new phenomena in diphoton final states.
A top quark mass measurement is performed using Formula omitted of LHC proton-proton collision data collected with the CMS detector at Formula omitted. The measurement uses the Formula omitted ...all-jets final state. A kinematic fit is performed to reconstruct the decay of the Formula omitted system and suppress the multijet background. Using the ideogram method, the top quark mass ( Formula omitted) is determined, simultaneously constraining an additional jet energy scale factor ( Formula omitted). The resulting value of Formula omitted is in good agreement with previous measurements. In addition, a combined measurement that uses the Formula omitted lepton+jets and all-jets final states is presented, using the same mass extraction method, and provides an Formula omitted measurement of Formula omitted. This is the first combined Formula omitted extraction from the lepton+jets and all-jets channels through a single likelihood function.
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