RESONANCE PRODUCTION AND DECAY IN PROTON-PROTON COLLISIONS AT T = 1.25 GeV MEASURED WITH HADES SPECTROMETER

In this paper we report on the investigation of baryonic resonance production in proton-proton collisions at kinetic energy 1.25 GeV measured with HADES. Exclusive channels ppe+e- and ppe+e-γ as well as ppπ0 and npπ+ were studied. The resonance cross section was determined from hadronic channels in the framework of a one boson exchange model with the accuracy of 15%. The dilepton analysis proved the resonance origin of e+e- pairs and the Δ Dalitz decay was identified experimentally (in the pe+e- channel) for the first time. Investigation of hadronic reaction channels by means of the Partial Wave Analysis revealed a dominant contribution of P33(1232) but also sizeable non-resonant terms and interference effects.

LINAC-BASED PHOTONUCLEAR APPLICATIONS AT THE IDAHO ACCELERATOR CENTER

In this paper, current Idaho Accelerator Center (IAC) activities based on the exploitation of high energy bremsstrahlung photons generated by linear electron accelerators will be reviewed. These beams are used to induce photonuclear interactions for a wide variety of applications in materials science, activation analysis, medical research, and nuclear technology. Most of the exploited phenomena are governed by the familiar giant dipole resonance cross section in nuclei. By proper target and converter design, optimization of photon and photoneutron production can be achieved, allowing radiation fields produced with both photons and neutrons to be used for medical isotope production and for fission product transmutation. The latter provides a specific application example that supports long-term fission product waste management. Using high-energy, highpower electron accelerators, we can demonstrate transmutation of radio-toxic, long-lived fission products (LLFP) such as 99Tc and 129I into short lived species. The latest experimental and simulation results will be presented.

Investigations on the Impact of Heavy Nuclides Resonance Elastic Scattering Models on Resonance Integrals

In today’s cross section data processing process, asymptotic scattering model is employed by NJOY for the neutron/nucleus elastic scattering interactions in the epithermal energy region, which means that the energy of a scattered neutron is always lower than its incident energy and it falls evenly within the interval of [αE, E]. This model has recently been proved to have non-ignorable errors at some resonances of heavy nuclides. In this study, to investigate the impact of heavy nuclides resonance elastic scattering models to the resonance integrals, exact scattering kernel is employed and a deterministic code Estuary is developed to efficiently solve the neutron slowing down problem. Numerical results demonstrate that with the use of Estuary, results given in the literature obtained by the Monte Carlo method can be reproduced. With the resonance cross section approximately represented by the single-level Breit-Wigner formulation, investigations are made for different resonance parameters for both asymptotic and exact scattering models. Relations between errors and these related parameters are summarized.

REVIEW OF TAU LEPTON STUDIES AT LEP

In little more than two years of operation the four LEP experiments have produced a wealth of results on τ lepton production and decay at the Z0 resonance. Cross section and forward-backward charge asymmetry measurements agree well with Standard Model expectations and, along with similar measurements from hadronic and other leptonic Z0 decays, permit extraction of electroweak parameters such as sin2 θW and constrain the value of the top quark mass in the Standard Model. New measurements of the τ lifetime and of the branching ratios for inclusive and many exclusive decays equal or better the precision of previous measurements. Measurements from LEP also confirm nonzero values for the average τ polarization and for the forward/backward τ polarization asymmetry, providing independent determinations of electroweak parameters. In addition, searches have been carried out for new phenomena in tau production and decay, such as lepton flavor violation and CP violation, but so far no evidence for such effects has emerged.