180 research outputs found
A new spectrophotometric method for determining the extraction constant of quaternary complexes
No full textFirst measurement of f'(2)(1525) production in Z(0) hadronic decays
No full textThe inclusive production of the f(2)’(1525) in hadronic Z(0) decays has been studied in data collected by the DELPHI detector at LEP. The Ring Imaging Cherenkov detectors were important tools in the identification of the decay f(2)’(1525) –> K+K-. The average number of f(2)(’)(1525) produced per hadronic Z decay, [f(2)’] = 0.020 +/- 0.005 (stat) +/- 0.006 (syst), and the momentum distribution of the f(2)’(1525) have both been measured. The mass and width of the f(2)’(1525) are found to be [M(f2)’] = 1535 +/- 5 (stat) +/- 4 (syst) MeV/c(2). [Gamma(f2)’] = 60 +/- 20 (stat) +/- 19 (syst) MeV/c(2
A measurement of the photon structure function F-2(gamma) at an average Q(2) of 12 GeV2/c(4)
No full textThe hadronic photon structure function F-2(gamma) has been measured in the Q(2) range from 4 to 30 GeV2/c(4) and down to x values of order 0.001, using data taken with the DELPHI detector at LEP between 1991 and 1993. A comparison is made with several F-2(gamma) parameterizations with special emphasis on their low rr: behaviour. A result on the Q(2) evolution of F-2(gamma) is presented
First measurement of f2-prime (1525) production in Z0 hadronic decays
No full text\newcommand{\zz}{Z^{0}} Inclusive production of the f'_{2}(1525) in hadronic \zz\ decays has been studied in data collected by the DELPHI detector at LEP. The Ring Imaging Cherenkov detectors were important tools in the identification of the decay f'_{2}(1525)\rightarrow K^+K^-. The average number of f'_{2}(1525) produced per hadronic Z decay, = 0.020 \pm 0.005\mbox{ (stat)} \pm 0.006\mbox{ (syst)}, and the momentum distribution of the f'_{2}(1525) have both been measured
PRODUCTION CHARACTERISTICS OF K-0 AND LIGHT MESON RESONANCES IN HADRONIC DECAYS OF THE Z(0)
No full textAn analysis of inclusive production of KO and the meson resonances K*(+/-)(892), rho(0)(770), f(0)(975) and f(2)(1270) in hadronic decays of the Z(0) is presented, based on about 973,000 multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. Overall multiplicities have been determined as 1.962 +/- 0.060 K-0 mesons, 0.712 +/- 0.067 K*(+/-)(892) and 1.21 +/- 0.15 rho(0)(770) per hadronic Z(0) decay. The average multiplicities of f(0)(975) for scaled momentum, x(p) = p/p(beam), in the range 0.05 less than or equal to x(p) less than or equal to 0.6 and of f(2)(1270) for 0.05 less than or equal to x(p) less than or equal to 1.0 are 0.098 +/- 0.016 and 0.170 +/- 0.043 respectively. The f(0)(975) and rho(0)(770) x(p)-spectra have p similar shapes. The f(2)(1270)/rho(0)(770) ratio increases with x(p). The average multiplicities and the differential cross sections are compared with the JETSET Parton Shower model. The model with default parameters fails to reproduce the experimental K-0 momentum spectrum at low momentum, describes the K*(+/-)(892) and rho(0)(770) x(p)-spectrum shapes, but significantly overestimates their production rates
Determination of vertical bar V-cb vertical bar from the semileptonic decay B-0->D*(-)l(+)nu
No full textSemileptonic 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))%
Lifetime and production rate of beauty baryons from Z decays
No full textThe production and decay of beauty baryons (b-baryons) have been studied using 1.7 x 10(6) Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a Lambda and a lepton to tag the b-baryon decay. The second method associated fully reconstructed Lambda(c) baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured: f(b --> b-baryon) x BR(b-baryon --> Lambda l nu(l)X) = (0.30 +/- 0.06 +/- 0.04)%, f(b --> b-baryon) x BR(b-baryon --> Lambda(c)l nu(l)X) = (1.18 +/- 0.26(-0.21)(+0.31)%, f(b --> b-baryon) x BR(b-baryon --> p mu nu(mu)X) = (0.49 +/- 0.11 +/- (+0.15)(-0.11)%. The average b-baryon lifetime was determined to be: tau = 1.21(-0.18)(+.21)(stat.) +/- 0.04(exp.syst.)(-.07)(+.02)(th.syst,) ps
Lifetime and production rate of beauty baryons from Z decays
No full textThe production and decay of beauty baryons (b-baryons) have been studied using 1.7 \times 10^6 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a \Lambda and a lepton to tag the b-baryon decay. The second method associated fully reconstructed \Lambda_c baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured: \begin{eqnarray*} f(\qb \ra \Bb) \times \BR(\Bb \ra \mLs \ell\bar{\nu}_{\ell}\X) & = & (0.30 \pm 0.06 \pm0.04)\% , \\ f(\qb \ra \Bb) \times \BR(\Bb \ra \mLc \ell\bar{\nu}_{\ell}\X) & = & (1.18 \pm 0.26^{+0.31}_{-0.21})\% , \\ f(\qb \ra \Bb) \times \BR(\Bb \ra \prot\mu\bar{\nu}_{\mu}\X) & = & (0.49\pm0.11\pm^{+0.15}_{ -0.11})\% . \end{eqnarray*} The average b-baryon lifetime was determined to be:\par \vspace{0.4cm} \centerline {\tau = 1.21 ^{+.21}_{-.18}(stat.)\pm0.04(exp.syst.) ^{+.02}_{-.07}(th.syst.) ps.
Determination of |V| from the semileptonic decay B --> Dl
No full textSemileptonic 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}})) \%
Determination of vertical bar V-cb vertical bar from the semileptonic decay B-0->D*(-)l(+)nu
No full textSemileptonic 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))%
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