B* production in Z decays

The decayB ^*B has been observed with the DELPHI detector at LEP, where theB ^* meson is produced inZ boson decays. The combination of inclusively reconstructedB mesons with well-measured converted photons yields a measurement of the flavour-averagedB ^*-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 ⁺-B ⁰) and theB _s -B _ud splitting of the mass difference. The production ratio ofB ^* toB mesons inZ decays is measured to be 0.72±0.03 (stat.) ±0.06 (syst.). Limits on the production cross-section of other hypothetical excitedB hadron states decaying radiatively are established. The differentialB ^* cross section has been measured to be in good agreement with the averageb fragmentation, yielding an average fractionalB ^* energy of x _E =0.695±0.009 (stat.) ±0.013 (syst.). From the decay angular distribution the relative contribution of longitudinalB ^* polarisation states is measured to be _L/(_L + _T) = 0.32 ± 0.04 (stat.) ±0.03 (syst.).CICYT_AEN93-0832     

The set of mapsF_{a,b} :x \mapsto x + a + \tfrac{b}{{2\pi }} sin(2πx) with any given rotation interval is contractiblewith any given rotation interval is contractible

Consider the two-parameter family of real analytic maps $F_{a,b} :x \mapsto x + a + \tfrac{b}{{2\pi }}$ sin(2πx) which are lifts of degree one endomorphisms of the circle. The purpose of this paper is to provide a proof that for any closed intervalI, the set of mapsF _a,b whose rotation interval isI, form a contractible set.     

Instantons and vacuum expectation values in the Schwinger model

Vacuum expectation values for the Schwinger model are computed within the path integral formalism for an instanton vacuum. The calculations are done in flat Euclidean space and use the wellknown anomaly result. It can be demonstrated that the instanton vacuum is absolutely necessary to obtain a consistent quantization. At last the results are compared to a similar treatment on the sphere and to the operator solution of the Schwinger model.Supported by Fonds zur Förderung der wissenschaftlichen Forschung in Österreich, Projekt Nr. P8444-TEC     

A precision measurement of the average lifetime ofB hadrons

The average lifetime ofB hadrons was measured using data collected with the DELPHI detector at the LEP collider during 1991 and 1992. The measurement was performed using two different anayses. The first method was an improvement on a previous technique, which used charged particle impact parameter distributions. This analysis measured an average lifetime forB hadrons of