How to search for pentaquarks in high energy hadronic interactions

The strange-anticharmed Pentaquark is a uud $\bar c$ ;s or udd $\bar c$ s five-quark baryon that is expected to be either a narrow resonance, or possibly even stable against strong and electromagnetic decay. We describe this hyperon here, its structure, binding energy and lifetime, resonance width, production mechanisms, production cross sections, and decay modes. We describe techniques to reduce backgrounds in search experiments and to optimize the conditions for Pentaquark observation. Possibilities for enhancing the signal over background in Pentaquark searches are investigated by examining predictions for detailed momentum and angular distributions in multiparticle final states. We consider a loosely boundD _s ^? N molecule and also a strongly-bound five-quark system. Fermilab E791 data, currently being analyzed, may have marginal statistics for showing definitive signals. Future experiments in the spirit of the recent CHARM2000 workshop, such as FNAL E781 and CERN COMPASS with 10⁶–10⁷ reconstructed charmed baryon events, should have sensitivity to determine whether or not the Pentaquark exists.     

Mechanical properties of 6061 Al-Mg-Si alloy after very rapid heating

The effects of time, temperature and strain rate on the yield strength determined at elevated temperature have been investigated for 6061-T6 Al-Mg-Si alloy. To achieve very short times-at-temperature, nanosecond pulse heating produced by electron beam energy deposition was used along with one-dimensional stress-wave loading. When a relatively thick sample is heated in this way it cannot expand on the same time scale as the temperature increase. As a result, stress relief waves propagate in the material after energy deposition, and this deformation occurring at high strain-rates and elevated temperatures produces microstructural changes that reduce the strength of the alloy on the time scale of a few μs. This strength reduction occurs in addition to that due to the lowered shear modulus at-temperature, and is an essentially permanent change reflected in the greatly reduced room temperature strength of the material following nanosecond pulse heating.If the material is heated slowly enough so that the sample can expand as the temperature increases, and if the soaking time at temperature is less than required for microstructural changes in the alloy (e.g. approximately 3 s at 260°C), the yield strength measured at-temperature under wave propagation conditions drops in proportion to the shear modulus. In addition, the yield strength measurement is sensitive to the rate of deformation at elevated temperatures even for short times-at-temperature. The nature of this sensitivity is discussed in terms of thermally-activated dislocation motion.     

Mössbauer sum rules for use with synchrotron sources

The concentration dependence study of the formation rate of the muon molecules dtμ in equilibrium double D/T and triple H/D/T liquid mixtures of hydrogen isotopes requires an installation consisting of a target of volume 30 cm³ with helium cooling and a thermostabilization system. The temperature of the target, close to 22 K is fixed with an accuracy of 0.1 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

Some implications of the observed decay ψ → f + γ

Describing the ψ → f+γ decay via an intermediate one-photon state avoids difficulties encountered in strong OZI- violating transitions. The ψ → γ →f+γ transition is enhanced an order of magnitude because amplitudes for the u$\text{u}$ and d$\text{d}$ components of the f are proportional to squares of quark charges and add constructively. A rough dynamical estimate agrees with the experimental decay rate. Branching ratios for f+γ,A₂+γ and f′ + γ decays are shown to be very different for electromagnetic and strong transitions and can test models. Tests of the Han-Nambu model and contributions from the weak neutral current are discussed.     

Restoration of Cu-selective electrodes

Russian Journal of Applied Chemistry - Donor-acceptor interaction of a Cu-selective electrode screening layer with salicylalaniline in N,N-dimethyl formamide resulting in a membrane sensitization...     

Investigation of some nitrogen compounds of 2,2′-bithienyl

The formylation of 5-(quinolin-2-yl)-2,2′-bithienyl leads to the 5′-formyl derivative, and from this a number of azomethines has been obtained.     

Mirror transitions and second class currents

Theoretical implications of observed mirror asymmetry in nuclear beta decay are examined, taking into account CP violation and internal symmetries. The second class induced tensor current is shown not to be responsible for the observed asymmetry, which must be the result of multinucleon or meson exchange effects. The result is general and holds for all values of momentum transfer. Possible two nucleon transitions are discussed. Mirror asymmetry in the Σ−Λ decay cannot be produced by SU(3) octet currents or single quark currents in the quark model even if such second class currents exist.