Propagation of ultra-short waves in the atmosphere of Venus

Decimeter and centimeter radio wave propagation in atmosphere of Venu

Final state interaction in the production of heavy unstable particles

We make an attempt to discuss in detail the effects originating from the final state interaction in the processes involving production of unstable elementary particles and their subsequent decay. Two complementary scenarios are considered: the single resonance production and the production of two resonances. We argue that part of the corrections due to the final state interaction can be connected with the Coulomb phases of the involved charge particles; the presence of the unstable particle in the problem makes the Coulomb phase ``visible''. It is shown how corrections due to the final state interaction disappear when one proceeds to the total cross-sections. We derive one-loop non-factorizable radiative corrections to the lowest order matrix element of both single and double resonance production. We discuss how the infrared limit of the theories with the unstable particles is modified. In conclusion we briefly discuss our results in the context of the forthcoming experiments on the $W^+W^-$ and the $t\bar t$ production at LEP $2$ and NLC.Comment: 33 pages, latex, 6 figures (added), version accepted for publication in Nuc. Phys. B, substantial revisio

Couplings of heavy hadrons with soft pions from QCD sum rules

We estimate the couplings in the Heavy Hadron Chiral Theory (HHCT) lagrangian from the QCD sum rules in an external axial field. We take into account the perturbative correction to the meson correlator in the infinite mass limit. With the perturbative correction and three successive power corrections, the meson correlator in an axial field becomes one of the best known correlators. In spite of this, the corresponding sum rule is not very stable. It yields the result g_1 F^2/(380MeV)^3 = 0.1 - 0.2, where F^2 = f_M^2 m/4 = (380MeV)^3 is the central value of the heavy meson decay constant with the perturbative correction. This result is surprisingly low as compared with the constituent quark model estimate g_1 = 0.75. The sum rules for g_{2,3} following from nondiagonal Sigma-Sigma and diagonal Lambda-Sigma baryon correlators in an external axial field suggest g_{2,3} = 0.4 - 0.7, while diagonal Sigma-Sigma and nondiagonal Lambda-Sigma baryon sum rules have too large uncertainties.Comment: 15 pages, LaTeX2e, 6 ps figures include

QCD Sum Rules for Heavy Flavors

We give a short review of QCD sum rule results for B and D mesons and Lambda_Q and Sigma_Q baryons. We focus mainly on recent developments concerning semileptonic B->pion and D->pion transitions, pion couplings to heavy hadrons, decay constants and estimates of the b quark mass from a baryonic sum rule, and the extraction of the pion distribution amplitude from CLEO data.Comment: 12 pages, LaTeX, Talk given by O.Yakovlev at the 4th Workshop on Continuous Advances in QCD, Minneapolis, May 12-14, 2000; to appear in the Proceeding

QCD Radiative Correction to Zero Recoil Sum Rules for Heavy Flavor Transitions in the Small Velocity Limit.

We consider the small velocity sum rules for heavy flavour semileptonic transitions that are used to estimate the zero recoil values of semileptonic heavy flavour form factors. We analyze the complete O($\alpha _S$) radiative correction to these sum rules. The corrections are universal and influence all "model-independent" bounds previously derived for semileptonic form factors at zero recoil.Comment: 13 pages, LaTeX, 3 figures

Direct Urca Process in a Neutron Star Mantle

We show that the direct Urca process of neutrino emission is allowed in two possible phases of nonspherical nuclei (inverse cylinders and inverse spheres) in the mantle of a neutron star near the crust-core interface. The process is open because neutrons and protons move in a periodic potential created by inhomogeneous nuclear structures. In this way the nucleons acquire large quasimomenta needed to satisfy momentum-conservation in the neutrino reaction. The appropriate neutrino emissivity in a nonsuperfluid matter is about 2--3 orders of magnitude higher than the emissivity of the modified Urca process in the stellar core. The process may noticeably accelerate the cooling of low-mass neutron stars.Comment: 7 pages, 3 figures, submitted to A&