Measurement of the polarization of positive muons produced in high-energy antineutrino interactions

The question whether scalar-type interactions contribute to weak interactions at large momentum transfer has been investigated by a measurement of the longitudinal polarization of positive muons produced in charged-current interactions of high-energy antineutrinos with iron. At an average momentum transfer <Q ²>=4 GeV² the muon spin is found to be oriented forward with respect to the muon momentum vector, with an average polarization of 1.10±0.24, consistent with positive helicity. A limit on scalar contributions of σ_{s, p}/σ_tot <7% at the 95% confidence level can be deduced. A search for violation of time reversal invariance which could manifest itself by a polarization component perpendicular to the muon production plane gave a limit of σ_tv/σ_tot <16% (95% c.l.). It is concluded that the weak leptonic charged current retains its dominant vector and axial vector structure at large momentum transfers.     

The effect of LH wave on the peripheral plasma of TM-1-MH tokamak

The work is devoted to the study of the LH wave effect on the peripheral plasma of the TM-1-MH tokamak. The observed enhancement of the ion saturated current in the limiter shadow is interpreted as heating of the peripheral ions by absorption of decay waves generated in this region due to the nonlinear wave-plasma interaction.     

Low-temperature spin-lattice relaxation of8Li in the glass Li2O·2SiO2

Nuclear spin-lattice relaxation in Li₂0·2Si0₂ glass below 200 K has been studied using the asymmetric Β-decay radiation of polarized⁸Li (T_1/2=0.Bs) nuclei produced by capture of polarized neutrons. Transients of the⁸Li polarization follow an exp(?√E/T₁) law. The dependence of the spin-lattice relaxation rate ⊥_¯1 ¹ on temperature T and magnetic field B can roughly be described by T_¯1 ¹～T/B. The interpretation is based on the assumption that for⁸Li, contrary to⁷Li in the same glass, spin-diffusion is absent and that each probe nucleus is coupled by quadrupolar interaction to an individual distribution of nearby centres typical of glasses. The fluctuation of these centres causing relaxation may be induced by either a multi-phonon or a thermally activated motional process.     

The effect of dissipation on coherent quantum tunnelling in a double-well system: Two-level model using an adjoint equation approach

We examine the effect of dissipation on coherent quantum tunnelling between the two lowest levels of a double-well system using an adjoint equation approach developed previously in the treatment of quantum-optical problems. Dissipation is modelled by a linear coupling to a bath of harmonic oscillators. The high frequency portion of the bath is adiabatically eliminated using a cumulant expansion technique, which generates frequency renormalisation terms. Making a low temperature assumption, an approximate two-level model is developed in the form of three coupled stochastic differential equations. With a decorrelation approximation, the two-level equations can be solved to yield familiar results. However, the adjoint equation also permits the use of direct stochastic simulation as a means of solution, and simulations are carried out for a range of parameters. A comparison with the decorrelation approximation is made.     

Upper limit for thermal direct photon production in heavy-ion collisions at 60 and 200A·GeV

The production of direct photons has been investigated in reactions ofp and¹⁶O projectiles at 60 and 200A·GeV with C and Au nuclei. Photon and ⁰ spectra have been measured in the pseudorapidity range 1.52.1 for the transverse momentum region 0.4 GeV/cp _T 2.8 GeV/c employing the lead-glass spectrometer SAPHIR. An upper limit of 15% at the 90% confidence level for the direct photon signal relative to the neutral pion production is obtained from the comparison of measured photon spectra with Monte Carlo simulations of the hadronic background based on the reconstructed yield of ⁰ and mesons. Consequences for a possible phase transition to a quark-gluon plasma are discussed.     

Pulsed-field gradient nuclear magnetic resonance study of transport properties of fluid catalytic cracking catalysts

Pulsed-field gradient nuclear magnetic resonance (PFG NMR) has been applied to study molecular diffusion in industrial fluid catalytic cracking (FCC) catalysts and in USY zeolite for a broad range of molecular displacements and temperatures. The results of this study have been used to elucidate the relevance of molecular transport on various displacements for the rate of molecular exchange between catalyst particles and their surroundings. It turned out that this rate, which may determine the overall rate and selectivity of FCC process, is primarily related to the diffusion mode associated with displacements larger than the size of zeolite crystals located in the particles but smaller than the size of the particles. This conclusion has been confirmed by comparative studies of the catalytic performance of different FCC catalysts.     

A reanalysis of branching fractions of charmed mesonsD 0,D + andD s +

We combine highly complementary information on branching fractions of charmed mesonsD ⁰,D ⁺ andD _s ⁺ coming from two experiments both yielding doublecharm samples. The NA 32 experiment provided exclusive branching fractions for channels with at least two charged decay products while a recent Mark III paper provides results on inclusive charm decay properties. The knowledge of channels withK ⁰'s in the former is used to recalculate the charged multiplicity distribution in the latter. We obtain 〈n _ch〉=2.25±0.08 forD ⁰, 〈n _ch〉=1.96±0.08 forD ⁺ and 〈n _ch〉=2.41±0.38 forD _s ⁺ . In turn the knowledge of the charged multiplicity improves the overall normalization of exclusive branching fractions. This reanalysis yields model-independent results for charmed mesons. In particular we obtain branching fractions for 16D _s ⁺ decay channels including $$BF(D_s^ + \to \phi \pi ^ + ) = \left( {4.4\begin{array}{*{20}c} { + 2.3} \\ { - 1.8} \\ \end{array} } \right)\% .$$ .