600 research outputs found
First evidence for a charm radial excitation, D*-prime
No full textUsing D mesons exclusively reconstructed in the DELPHI detector at LEP, an excess of 66\pm14(\mbox{stat.}) events is observed in the D final state with a mass of 2637\pm2(\mbox{stat.})\pm6(\mbox{syst.})~MeV/ and a full width smaller than 15~MeV/ (95\% C.L.). This signal is compatible with the expected decay of a radially excited D () meson
J / psi and psi-prime production at the CERN p anti-p collider
No full textWe have measured the production cross-section times branching ratio for J/PSI --> mu+ mu- in ppBAR interactions at square-root s = 630 GeV in the kinematic range /y/ 5 GeV/c, BR (J/PSI --> mu+ mu-)sigma(ppBAR --> J/PSI) = 6.18 +/- 0.24 +/- 0.81 nb. The data sample collected in 1988 and 1989 for an integrated luminosity of 4.7 pb-1 represents a fivefold improvement over the statistics in our earlier study of the J/PSI production process, and the P(T) distribution which is measured extends to 28 GeV/c. Using event topology we show that the rate for the direct production of J/PSI, via radiative decays of chi-states, is larger than that for production via B-hadrons. Production of PSI' is also studied using the decay modes PSI' --> mu+ mu- and PSI' --> J/PSI-pi+pi-
J/PSI AND PSI' PRODUCTION AT THE CERN P-BARP COLLIDER
No full textWe have measured the production cross-section times branching ratio for J/PSI --> mu+ mu- in ppBAR interactions at square-root s = 630 GeV in the kinematic range /y/ 5 GeV/c, BR (J/PSI --> mu+ mu-)sigma(ppBAR --> J/PSI) = 6.18 +/- 0.24 +/- 0.81 nb. The data sample collected in 1988 and 1989 for an integrated luminosity of 4.7 pb-1 represents a fivefold improvement over the statistics in our earlier study of the J/PSI production process, and the P(T) distribution which is measured extends to 28 GeV/c. Using event topology we show that the rate for the direct production of J/PSI, via radiative decays of chi-states, is larger than that for production via B-hadrons. Production of PSI' is also studied using the decay modes PSI' --> mu+ mu- and PSI' --> J/PSI-pi+pi-
Search for systematic errors in a stopping anti-proton experiment in the Saclay 81 cm chamber
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First observation of the beauty baryon LAMBDA(b) in the decay channel LAMBDA(b) ---> J / psi LAMBDA at the CERN proton - anti-proton collider
No full textWe report on the first observation of the beauty baryon LAMBDA(b) in an exclusive decay channel at the CERN ppBAR collider. Using 4.7 pb-1 of muon data collected in the 1988/89 collider runs we reconstruct 16 +/- 5 LAMBDA(b)'s in the decay mode LAMBA(b) --> J/psi-LAMBDA above a background of 9 +/- 1 events, corresponding to a significance of about five standard deviations. We measure the LAMBDA(b) mass to be m(LAMBDA(b)) = 5640 +/- 50 +/- 30 MeV/c2. Using the beauty cross-section measured by UA1 we deduce for the product of the production fraction and branching ratio f(LAMBDA(b)) Br(LAMBDA(b) --> J/psi-LAMBDA) = (1.8 +/- 1.0) X 10(-3). Our sample contains a three-muon event in which the beauty particle opposite to the LAMBDA(b)BAR is tagged by the third muon. We also observe an indication of a signal in the decay channel B0 --> J/psi-K0* with a significance of three standard deviations
J / psi production in the hadronic decays of the Z
No full textJ/ψ mesons have been reconstructed from their decay to μ+μ- and e+e-, using the data collected by the DELPHI experiment during 1991 and 1992 at the LEP collider. From about 1 million hadronic Z decays 153 ± 17 J/ψ were found, 5.4 ± 2.3 ψ′ were obtained in the channel J/ψ (→μ+μ-)π+π- and 6.4 ± 2.7 χc in the channel J/ψ ( → μ+μ-)γ. As the dominant source of Jψ mesons is from bquarks, the following branching ratios: Br(b → J/ψ X) = (1.12 ± 0.12 (stat) ± 0.10 (syst.))%, Br(b → ψ′ X) = (0.48 ± 0.22 (stat.± 0.10 (syst.))%, Br(b → χc1 X) = (1.4 ± 0.6 (stat.)-0.2+0.4 (syst.))% were measured. From the proper time distribution of the J/ψ sample, the average lifetime of b-hadrons decaying into J/ψ was found to be: τB = 1.50-0.21+0.24 (stat.) ± 0.03 (syst.) ps. A search for completely reconstructed B meson decays to final states including a J/ψ gave a signal of 15 ± 5 events.0info:eu-repo/semantics/publishe
Measurement of B(d)0 - anti-B(d)0 oscillations
No full textBd 0meson oscillations are measured in hadronic Z0decays using the charge of a lepton or the mean charge of an event hemisphere to sign the presence of a b or a b quark when it is produced, and using the charge of a lepton emitted at large ptor of a D∗±to sign the presence of a B or a B meson when it decays. With 3.2 million hadronic Z0decays registered by DELPHI between 1991 and 1994, the mass difference Δmdbetween the two physical Bd 0states is measured in four channels: Δmd= 0.523 ± 0.072 ± 0.043 ps-1(D∗±- Qhem) Δmd= 0.493 ± 0.042 ± 0.027 ps-1(ℓ - Qhem) Δmd= 0.499 ± 0.053 ± 0.015 ps-1((π∗- ℓ) - Qhem) Δmd= 0.480 ± 0.040 ± 0.051 ps-1(ℓ - ℓ). Taking into account the statistical overlap between these measurements and the common systematic uncertainties, the combined result is: Δmd= 0.497 ± 0.035 ps-1.0info:eu-repo/semantics/publishe
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