Measurement of the B-d(0) oscillation frequency using kaons, leptons and jet charge

A measurement of the mass difference, Delta m(d), be tween the two physical B-d(0) states has been obtained from the analysis of the impact parameter distribution of a lepton emitted at large transverse momentum (p(t)) relative to the jet axis and from the analysis of the flight distance distribution of secondary vertices tagged by either a high p(t) lepton or an identified kaon. In the opposite hemisphere of the event, the charge of the initial quark has been evaluated using a high p(t) lepton, a charged kaon or the mean jet charge, With 1.7 million hadronic Z(0) decays recorded by DELPHI between 1991 and 1993, Delta m(d) is found to be: Delta m(d) = 0.531 (+0.050)(-0.046) (stat.) +/- 0.078 (syst.) ps(-1)

Determination of vertical bar V-cb vertical bar from the semileptonic decay B-0->D*(-)l(+)nu

Semileptonic decays B --> D*(-)l(+)nu X were selected from a sample of 3.1 million hadronic Z decays collected by the DELPHI detector at LEP. A topological search for semileptonic B decays to resonant and non-resonant D*(-)pi(+) states was performed and the ratio of the branching fractions: Br(B --> D*(-)l(+)nu X)/Br(B --> D*(-)l(+)nu X) + Br(B-0 --> D*(-)l(+)nu) = 0.19 +/- 0.10(stat) +/- 0.06(syst) was determined. Taking into account this contribution, the differential decay width of B-0 --> D*(-)l(+)nu was measured as a function of the momentum transfer from the B to the D*(-) in two separate analyses, using exclusive and inclusive methods of D*(-) reconstruction. The distributions were fitted over the full momentum transfer range to extract the product of /V-cb/ times the normalization of the decay form factor F(q(max)(2)): F(q(max)(2))/V-cb/ = (35.4 +/- 1.9(stat) +/- 2.4(syst)) . 10(-3). The value of /V-cb/ was computed using theoretical calculations of F(q(max?2), giving: /V-cb/ = (38.9 +/- 2.0(stat) +/- 2.6(syst) +/- 1.7(theory)) . 10(-3). The total branching fraction Br(B-0 --> D*(-)l(-)nu) was determined to be: Br(B-0 --> D*(-)l(+)nu) = (5.52 +/- 0.17(stat) +/- 0.68(syst))%

Production of Strange B-baryons Decaying Into Xi-/+-l-/+ Pairs At Lep

An excess of events containing, in a jet, a same-sign Xi(-/+) - l(-/+) pair as compared to those with an opposite-sign Xi(-/+) - l(-/+) pair has been observed in an analysis of 1.7 million hadronic Z(o) decays collected by the DELPHI detector at LEP between 1991 and 1993 inclusive. The probability for this signal to come from non B-baryon decays is less than 5 x 10(-4). The measured production fraction corresponds to: P(b --> B - baryon) x BR(B - baryon --> Xi(-) l(-) X) = (5.9 +/- 2.1 +/- 1.0) x 10(-4), per lepton species, averaged for electrons and muons and assuming the two channels have an equal contribution. Semileptonic decays of Lambda(b) baryons can account for less than 10% of these events and the major part of the signal has to originate from Xi(b) semileptonic decays, Using the subsample of these events where the Xi(-/+) trajectory has been measured in the Vertex Detector, the lifetime of B-baryons producing a Xi(-/+) in their semileptonic decay final state is found to be: tau(B - baryon --> Xi(-) l(-) X) = 1.5(-0.4)(+0.7) +/- 0.3 ps

Study of hadronic decays of the ZO boson

Hadronic decays of Z0 bosons are studied in the Delphi detector. Global event variables and single particle inclusive distributions are compared with QCD-based predictions. The mean charged multiplicity is found to be 20.6±1.0 (stat+syst). The mean values of the sphericity, aplanarity, thrust, minor value, pin T and pout T are compared with values found at lower energy e+e- colliders.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Determination of |Vcb_{cb}| from the semileptonic decay B0^{0} --> D∗−*^{-}l+ν^{+}\nu

Semileptonic decays B \rightarrow D^{*-} \ell^+ \nu X were selected from a sample of 3.1 million hadronic Z decays collected by the DELPHI detector at LEP. A topological search for semileptonic B decays to resonant %(D^{**}) and non-resonant D^{*-} \pi^{+} states was performed and the ratio of the branching fractions: \frac {Br ({\mathrm{B} \rightarrow {\mathrm D}^{*-}} \ell^+ \nu X)} {Br({\mathrm{B} \rightarrow {\mathrm D}^{*-}} \ell^+ \nu X) + Br( {\mathrm{B}^0 \rightarrow \mathrm{D}^{*-}} \ell^+ \nu)} = 0.19 \pm 0.10({\mathrm{stat}}) \pm 0.06({\mathrm{syst}}) was determined. Taking into account this contribution, %DB the differential production fraction of the decay the differential decay width of {\mathrm{B}^{0} \rightarrow \mathrm{D}^{*-}} \ell^+ \nu was measured as a function of the momentum transfer from the B to the D^{*-} in two separate analyses, using exclusive and inclusive methods of D^{*-} reconstruction. The distributions were fitted %DB with a linear function over the full momentum transfer range to extract the product of \mathrm{|V_{cb}|} times the normalization of the decay form factor F(q^2_{max}): F(q^2_{max})\mathrm{|V_{cb}|} = (35.0 \pm 1.9({\mathrm{stat}}) \pm 2.3({\mathrm{syst}}) )~\cdot~10^{-3}. The value of \mathrm|V_{cb}| was computed using theoretical calculations of F(q^2_{max}), giving: {\mathrm{|V_{cb}|}} = (38.5 \pm 2.1({\mathrm{stat}}) \pm 2.5({\mathrm{syst}}) \pm 1.7({\mathrm{theory}}))~\cdot~10^{-3}. The total branching fraction Br(\mathrm{B}^{0} \rightarrow D^{*-} \ell^+ \nu) was determined to be: Br ({\mathrm{B}^0 \rightarrow \mathrm{D}^{*-}} \ell^+ \nu) = (5.47 \pm 0.16({\mathrm{stat}}) \pm 0.67({\mathrm{syst}})) \%

Production of Sigma(0) and Omega(-) in Z decays

Reconstructed \lam\ baryon decays and photon conversions in DELPHI are used to measure the \sig\ production rate from hadronic Z^0 decays at LEP. The number of \sig\ decays per hadronic Z decay is found to be: \begin{center} \sig + \sigb = \wffe{0.070}{0.010}{0.010 }{}. \end{center} \bigskip The \Omega^- production rate is similarly measured to be: \begin{center} \Omega^- + \overline{\Omega}^+ = \wffe{0.0014}{0.0002}{0.0004}