0000000000085837
AUTHOR
Azzurri P
showing 8 related works from this author
Three-prong τ decays with charged kaons
1998
Final states with charged kaons in three-prong τ decays are studied by exploiting the particle identification from the dE/dx measurement. The results are based on a sample of about 1.6 × 105 detected τ pairs collected with the ALEPH detector between 1991 and 1995 around the Z peak. The following branching ratios have been measured: B(τ- → K−K+π−ντ) = (1.63 ± 0.21 ± 0.17) × 10−3, B(τ− → K−π+π−ντ) = (2.14 ± 0.37 ± 0.29) × 10−3, B(τ− → K−K+π−π0ντ) = (0.75 ± 0.29 ± 0.15) × 10−3, and B(τ− → K−π+π−π0ντ) = (0.61 ± 0.39 ± 0.18) × 10−3. The first two measurements are more precise than the current world averages, while the last two channels are investigated for the first time. The 95% C.L. upper limi…
Study of the fragmentation of b quarks into B mesons at the Z peak
2001
The fragmentation of b quarks into B mesons is studied with four million hadronic Z decays collected by the ALEPH experiment during the years 1991-1995. A semi-exclusive reconstruction of B->l nu D(*) decays is performed, by combining lepton candidates with fully reconstructed D(*) mesons while the neutrino energy is estimated from the missing energy of the event. The mean value of xewd, the energy of the weakly-decaying B meson normalised to the beam energy, is found to be mxewd = 0.716 +- 0.006 (stat) +- 0.006 (syst) using a model-independent method; the corresponding value for the energy of the leading B meson is mxel = 0.736 +- 0.006 (stat) +- 0.006 (syst). The reconstructed spectra …
The forward-backward asymmetry for charm quarks at the Z pole
1995
From 1.4 million hadronic Z decays collected by the ALEPH detector at LEP, an enriched sample of Z --> c $$($) over bar c events is extracted by requiring the presence of a high momentum D*(+/-). The charm quark forward-backward charge asymmetry at the Z pole is measured to be A(FB)(0,c) = (8.0 +/- 2.4)% corresponding to an effective electroweak mixing angle of sin(2) theta(W)(eff) = 0.2302 +/- 0.0054.
A study of tau decays involving eta and omega mesons
1997
The 132 pb(-1) of data collected by ALEPH from 1991 to 1994 have been used to analyze eta and omega production in 7 decays. The following branching fractions have been measured: B(tau(-) --> nu(tau)omega h(-)) = (1.91 +/- 0.07 +/- 0.06) x 10(-2), B(tau(-) --> nu(tau)omega h(-)pi(0)) = (4.3 +/- 0.6 +/- 0.5) x 10(-3), B(tau(-) --> nu(tau)eta K-) = (2.9(-1.2)(+1.3) +/- 0.7) x 10(-4), B(tau(-) --> nu(tau)eta(h)(-)pi(0)) = (1.8 +/- 0.4 +/- 0.2) x 10(-3) and the 95% C.L. limit B(tau(-) --> nu(tau)eta pi(-)) < 6.2 x 10(-4) has been obtained. The omega pi(-) and eta pi(-)pi(0) rates and dynamics are found in agreement with the predictions made from e(+)e(-) annihilation data with the help of isospi…
Measurement of the Effective b quark Fragmentation Function At the Z resonance
1995
Using a sample of about 1.46 million hadronic Z decays collected between 1991 and 1993 with the ALEPH detector at LEP, the energy distribution of the B-0 and B-+/- mesons produced at the Z resonance is measured by reconstructing semileptonic decays B --> l nu(l)D(X) or B --> l nu(l)D*(+)(X). The charmed mesons are reconstructed through the decay modes D-0 --> K(-)pi(+), D-0, --> K(-)pi(+)pi(-)pi(+),D+ --> K(-)pi(+)pi(+), and D*(+) --> D-0 pi(+). The neutrino energy is estimated from the missing energy in the lepton hemisphere. Accounting for B* and B** production, the shape of the scaled energy distribution x(E)((b)) for mesons containing a b quark is compared to the predictions of differen…
Measurement of triple gauge WWγ couplings at LEP2 using photonic events
1998
A study of events with photons and missing energy has been performed with the data sample obtained with the ALEPH detector at centre-of-mass energies from 161 to 184 GeV,corresponding to a total integrated luminosity of about 80 pb**-1.The measured distributions are in agreement with Standard Model predictions, leading to constraints on W W gamma gauge coupling parameters Delta(kappa_gamma) and lambda_gamma. The results from the fit to the cross sectionsand to the energy and angular distributions of the photons are: Delta(kappa_gamma) = 0.05 +1.15/-1.10 (stat) +/- 0.25 (syst) lambda_gamma = 0.05 +1.55/-1.45 (stat) +/- 0.30 (syst) A study of events with photons and missing energy has been pe…
Search for Single Top Production in $e^{+} e^{-}$ Collisions at $\sqrt{s}$ up to 209 GeV
2002
Single top production via the flavour changing neutral current reactions e+e- -> \bar{t}c, \bar{t}u is searched for within the 214 pb-1 of data collected by ALEPH at centre-of-mass energies between 204 and 209 GeV. No deviation from the Standard Model expectation is observed and upper limits on the single top production cross sections are derived. The combination with data collected at lower centre-of-mass energies yields an upper limit on the branching ratio BR(t -> Zc)+BR(t -> Zu) 14%, for BR(t -> ��c)+BR(t -> ��u)= 0 and mt=174 GeV/c2.
Measurements of the b baryon lifetime
1995
Using about 1.5 million hadronic Z decays recorded with the ALEPH detector, the lifetime of the b baryons has been measured using two independent data samples. From a maximum likelihood fit to the impact parameter distribution of leptons in 519 Lambda l(-) combinations containing a b baryon sample of 290 decays, the measured b baryon lifetime is tau(b-baryon) = 1.05(-0.11)(+0.12)(stat) +/-0.09(syst) ps. The lifetime of the Lambda(b)(0) baryon from a maximum likelihood fit to the proper time distribution of 58 Lambda(c)(+)l(-) candidates containing a Lambda(b)(0) sample of 44 decays, is tau(Lambda b0) = 1.02(-0.18)(+0.23)(stat) +/- 0.06(syst) ps.