Evidence for an excited hyperon state in pp --> pK+Y0*

Indications for the production of a neutral excited hyperon in the reaction pp --> pK+Y0* are observed in an experiment performed with the ANKE spectrometer at COSY-Jülich at p(beam) = 3.65 GeV/c. Two final states were investigated simultaneously, viz. Y0* --> pi+X- and pi-X+, and consistent results were obtained in spite of the quite different experimental conditions. The parameters of the hyperon state are M(Y0*) = (1480 +/-15) MeV/c2 and gamma(Y0*) = (60 +/- 15) MeV/c2. The production cross section for Y0* decaying through these channels is of the order of few hundred nanobarns. Since the isospin of the Y0* has not been determined here, it could either be an observation of the sigma(1480), a one-star resonance of the Particle Data Group tables, or, alternatively, a lambda hyperon. Relativistic quark models for the baryon spectrum do not predict any excited hyperon in this mass range and so the Y0* may be of exotic nature.     

Compensation for coarticulation, /u/-fronting, and sound change in standard southern British: an acoustic and perceptual study

The aim of the study was to establish whether /u/-fronting, a sound change in progress in standard southern British, could be linked synchronically to the fronting effects of a preceding anterior consonant both in speech production and speech perception. For the production study, which consisted of acoustic analyses of isolated monosyllables produced by two different age groups, it was shown for younger speakers that /u/ was phonetically fronted and that the coarticulatory influence of consonants on /u/ was less than in older speakers. For the perception study, responses were elicited from the same subjects to two minimal word-pair continua that differed in the direction of the consonants' coarticulatory fronting effects on /u/. Consistent with their speech production, young listeners' /u/ category boundary was shifted toward /i/ and they compensated perceptually less for the fronting effects of the consonants on /u/ than older listeners. The findings support Ohala's model in which certain sound changes can be linked to the listener's failure to compensate for coarticulation. The results are also shown to be consistent with episodic models of speech perception in which phonological frequency effects bring about a realignment of the variants of a phonological category in speech production and perception.     

Population of muonic 3He states following the μ-catalysed fusion pμd → μ3He

Recoil due to emission of the 5.5 MeV γ-ray in the fusion reaction $\text{pμd → μ}{}^3\text{He}$ and dynamical corrections to the Born-Oppenheimer approximation lead to excited muonic states in the final $\text{μ}{}^3\text{He}$ atom. The branching ratios for the lowest excitations are calculated.     

On the adiabaticity of continum states: tunnelling through a time-dependent barrier

The problem of tunnelling through a time-dependent delta-function barrier,V(x, t) =λτ/tδ(x), has been solved analytically fort≧0. The Massey parameter α=γτk/? controls the tunnel process: For α?1, a continuum electron with momentum ?k will adjust its wavefunction to the variable barrier; for α?1 the change of the barrier is too sudden to allow for adjustment. The characteristic time τ is used to clarify the concept of a tunnelling time.     

On the convergence of Marumori's boson expansion for pairing vibrations

It is demonstrated analytically for a two-level model with pairing force that Marumori's method converges rapidly if one uses the idea of pairing vibrations. The approximation of Sørensen and the broken-pair approximation are compared with Marumori's boson expansion.     

Exclusive measurement of coherent η-photoproduction from the deuteron

Coherent photoproduction of η-mesons from the deuteron has been measured from threshold up to E _γ≈ 750 MeV using the photon spectrometer TAPS at the tagged photon facility at the Mainz microtron MAMI. For the first time, differential coherent cross-sections have been deduced from the coincident detection of the η-meson and the recoil deuteron. A missing-energy analysis was used for the suppression of background events so that a very clean identification of coherent η-photoproduction was achieved. The resulting cross-sections agree with previous experimental results except for angles around 90^° in the γd c.m. system where they are smaller. They are compared to various model calculations. Received: 5 April 2001 / Accepted: 3 September 2001     

Thermostability and physicochemical properties of two macauba oils and their derivatives related to their use as a lubricant base

Journal of Thermal Analysis and Calorimetry - Nowadays, the search for enforcement actions that are aligned with the concept of sustainable development is noted in various areas of knowledge. In...