B* production in Z decays
Zeitschrift für Physik C Particles and Fields 68:3 (1995) 353-362
Abstract:
The decay B*→Bγ has been observed with the DELPHI detector at LEP, where the B* meson is produced in Z boson decays. The combination of inclusively reconstructed B mesons with well-measured converted photons yields a measurement of the flavour-averaged B*-B mass difference of 45.5±0.3 (stat.) ±0.8 (syst.) MeV/c2. 95% confidence level upper limits at 6 MeV/c2 are placed on both the isospin (i.e. B+-B0) and the Bs-Bud splitting of the mass difference. The production ratio of B* to B mesons in Z decays is measured to be 0.72±0.03 (stat.) ±0.06 (syst.). Limits on the production cross-section of other hypothetical excited B hadron states decaying radiatively are established. The differential B* cross section has been measured to be in good agreement with the average b fragmentation, yielding an average fractional B* energy of 〈xE〉=0.695±0.009 (stat.) ±0.013 (syst.). From the decay angular distribution the relative contribution of longitudinal B* polarisation states is measured to be σL/(σL + σT) = 0.32 ± 0.04 (stat.) ±0.03 (syst.). © 1995 Springer-Verlag.Lifetime and production rate of beauty baryons from Z decays
Zeitschrift für Physik C Particles and Fields 68:3 (1995) 375-390
Abstract:
The production and decay of beauty baryons (b-baryons) have been studied using 1.7×106 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 Λ and a lepton to tag the b-baryon decay. The second method associated fully reconstructed ΛC 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:[Figure not available: see fulltext.] The average b-baryon lifetime was determined to be:[Figure not available: see fulltext.] © 1995 Springer-Verlag.Lifetime of charged and neutral B hadrons using event topology
Zeitschrift für Physik C Particles and Fields 68:3 (1995) 363-374
Abstract:
The lifetimes of charged and neutral B hadrons have been measured using data collected by the DELPHI experiment at LEP between 1991 and 1993. B hadrons are tagged as jets with a secondary vertex and the charge of the B candidate is taken to be the sum of the charges of the particles in the secondary vertex. Approximately 1,434,000 multihadronic Z0 decays yielded 1817 B hadron candidates. The B purity was estimated to be around 99.1±0.3%, and 83% (70%) of the events measured as neutral (charged) came from neutral (charged) B's. The mean lifetimes of charged and neutral B hadrons were found to be 1.72±0.08 (stat.) ±0.06 (syst.) ps and 1.58±0.11 (stat.)±0.09 (syst.) ps respectively. The ratio of their lifertimes, τcharged/τneutral, was 1.09-0.10+0.11 (stat.)±0.08 (syst.). By making assumptions about the Bs0 and Λb0 states, the B+ and B0 meson lifetimes were determined to be τB+ = 1.72 ± 0.08 (stat.) ±0.06 (syst.) ps and τB+ = 1.63 ± 0.14 (stat.)±0.13 (syst.) ps and the ratio of their lifetimes was: τB+/τB0 = 1.06-0.11+0.13 ±0.10. The mean B lifetime was also deduced to be < τ > = 1.64 ±0.06 (stat.)±0.04 (syst.) ps. © 1995 Springer-Verlag.Measurement of the proton structure function F2 from the 1993 HERA data
Zeitschrift für Physik C Particles and Fields 65:3 (1995) 379-398
Abstract:
The ZEUS detector has been used to measure the proton structure function F2. During 1993 HERA collided 26.7 GeV electrons on 820 GeV protons. The data sample corresponds to an integrated luminosity of 0.54 pb-1, representing a twenty fold increase in statistics compared to that of 1992. Results are presented for 7Measurement of {Mathematical expression} using impact parameter measurements and lepton identification
Zeitschrift für Physik C Particles and Fields 66:3 (1995) 323-339