Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with the data recorded by the DELPHI detector at LEP. From measurements of the ...inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been used to determine parameters which enter into the extraction of |Vcb| from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are:\(\begin{array}{*{20}l}{{m_{b} {\left( {1\;{\text{GeV}}} \right)}} \hfill} & { = \hfill} & {{4.591 \pm 0.062 \pm 0.039 \pm 0.005\;{\text{GeV/c}}^{2} ,} \hfill} \\{{m_{c} {\left( {1\;{\text{GeV}}} \right)}} \hfill} & { = \hfill} & {{1.170 \pm 0.093 \pm 0.055 \pm 0.005\;{\text{GeV/c}}^{{\text{2}}} {\text{,}}} \hfill} \\{{\mu ^{2}_{\pi } {\left( {1\;{\text{GeV}}} \right)}} \hfill} & { = \hfill} & {{0.399 \pm 0.048 \pm 0.034 \pm 0.087\;{\text{GeV}}^{{\text{2}}} {\text{,}}} \hfill} \\{{ \ifmmode\expandafter\tilde\else\expandafter\~\fi{\rho }^{3}_{D} } \hfill} & { = \hfill} & {{0.053 \pm 0.017 \pm 0.011 \pm 0.026\;{\text{GeV}}^{{\text{3}}} ,} \hfill} \\\end{array} \)and include corrections at order 1/mb3. Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of |Vcb| is obtained: \({\left| {V_{{cb}} } \right|} = 0.0421 \times {\left( {1 \pm 0.014_{{{\text{meas}}{\text{.}}} \pm 0.014_{{{\text{fit}}} \pm 0.015_{{{\text{th}}{\text{.}}} } \right)}\)
The data taken by
Delphi
at centre-of-mass energies between 189 and 209 GeV are used to place limits on the
CP
-conserving trilinear gauge boson couplings
,
λ
γ
and Δ
κ
γ
associated to
W
+
W
−
and ...single
W
production at
Lep2
. Using data from the
jj
ℓ
ν
,
jjjj
,
jjX
and
ℓ
X
final states, where
j
,
ℓ
and
X
represent a jet, a lepton and missing four-momentum, respectively, the following limits are set on the couplings when one parameter is allowed to vary and the others are set to their Standard Model values of zero:
Results are also presented when two or three parameters are allowed to vary. All observations are consistent with the predictions of the Standard Model and supersede the previous results on these gauge coupling parameters published by
Delphi
.
An analysis of the direct soft photon production rate as a function of the parent jet characteristics is presented, based on hadronic events collected by the DELPHI experiment at LEP1. The ...dependences of the photon rates on the jet kinematic characteristics (momentum, mass, etc.) and on the jet charged, neutral and total hadron multiplicities are reported. Up to a scale factor of about four, which characterizes the overall value of the soft photon excess, a similarity of the observed soft photon behavior to that of the inner hadronic bremsstrahlung predictions is found for the momentum, mass, and jet charged multiplicity dependences. However for the dependence of the soft photon rate on the jet neutral and total hadron multiplicities a prominent difference is found for the observed soft photon signal as compared to the expected bremsstrahlung from final state hadrons. The observed linear increase of the soft photon production rate with the jet total hadron multiplicity and its strong dependence on the jet neutral multiplicity suggest that the rate is proportional to the number of quark pairs produced in the fragmentation process, with the neutral pairs being more effectively radiating than the charged ones.
Neutral triple-gauge-boson couplings ZZZ, ZZγ and Zγγ have been studied with the DELPHI detector using data at energies between 183 and 208 GeV. Limits are derived on these couplings from an analysis ...of the reactions e+e-→Zγ, using data from the final states γff̄, with f=q or ν, from e+e-→ZZ, using data from the four-fermion final states qq̄qq̄, qq̄μ+μ-, qq̄e+e-, qq̄νν̄, μ+μ-νν̄ and e+e-νν̄, and from e+e-→Zγ*, in which the final state γ is off mass-shell, using data from the four-fermion final states qq̄e+e- and qq̄μ+μ-. No evidence for the presence of such couplings is observed, in agreement with the predictions of the Standard Model.
Fully reconstructed tt¯→W+bW−b¯→ℓνqq¯′bb¯ events are used to determine the fractions of right-handed (f+) and longitudinally polarized (f0) W bosons produced in top-quark decays. The helicity ...fractions are sensitive to the couplings and the Dirac structure of the Wtb vertex. This Letter reports measurements of the W-boson helicity fractions from two different methods using data corresponding to an integrated luminosity of 1.9fb−1 of pp¯ collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector operating at the Fermilab Tevatron. Combining the results from the two methods, we find f0=0.62±0.10(stat)±0.05(syst) under the assumption that f+=0, and f+=−0.04±0.04(stat)±0.03(syst) with f0 fixed to the theoretically expected value of 0.70. Model-independent fits are also performed and simultaneously determine f0=0.66±0.16(stat)±0.05(syst) and f+=−0.03±0.06(stat)±0.03(syst). All these results are consistent with standard model expectations.
Soft photons inside hadronic jets converted in front of the DELPHI main tracker (TPC) in events of qq disintegrations of the Z(0) were studied in the kinematic range 0.2 < E-y < I GeV and ...transverse momentum with respect to the closest jet direction P-T < 80 MeV/c. A clear excess of photons in the experimental data as compared to the Monte Carlo predictions is observed. This excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/- 0.27) x 10(-3) gamma/jet in the specified kinematic region, while the expected level of the inner hadronic bremsstrahlung (which is not included in the Monte Carlo) is (0.340 +/- 0.001 +/- 0.038) X 10(-3) gamma/jet. The ratio of the excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8), which is similar in strength to the anomalous soft photon signal observed in fixed target experiments with hadronic beams.
Single top quark production via four-fermion contact interactions associated to flavour-changing neutral currents was searched for in data taken by the DELPHI detector at LEP2. The data were ...accumulated at centre-of-mass energies ranging from 189 to 209 GeV, with an integrated luminosity of 598.1 pb
−1
. No evidence for a signal was found. Limits on the energy scale
Λ
, were set for scalar-, vector- and tensor-like coupling scenarios.
We present one additional study of multi-muon events produced at the Fermilab Tevatron collider and recorded by the CDF II detector. We use a data set acquired with a dedicated dimuon trigger and ...corresponding to an integrated luminosity of 3.9 fb−1. We investigate the distribution of the azimuthal angle between the two trigger muons in events containing at least four additional muon candidates to test the compatibility of these events with originating from known QCD processes. We find that this distribution is markedly different from what is expected from such QCD processes and this observation strongly disfavors the possibility that multi-muon events result from an underestimate of the rate of misidentified muons in ordinary QCD events.
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