MACRO, a large-area detector at the Gran Sasso Laboratory

Summary MACRO is a large-area detector to be installed in hall B of the Gran Sasso Laboratory. Making use of scintillation counters, plastic streamer tubes, and track-etch detectors, it is designed to search for superheavy magnetic monopoles beyond the Parker bound, high-energy gamma and neutrino cosmic sourcs, and, more in general, exotic phenomena in the cosmic radiation. MACTO is an acronym for Monopole, Astrophysics and Cosmic Ray Observatory. The present collaboration: Bari(**)C. De Marzo, O. Erriquez, N. Giglietto andF. Posa. Bologna(**):M. Attolini, F. Baldetti, G. Giacomelli, F. Grianti, A. Margiotta andP. Serra. Caltech:B. Barish, C. Lane andG. Liu. CERN:P. Musset, G. Poulard andH. Sletten. Drexel:R. Steinberg. Laboratori Nazionali di Frascati dell'INFN:G. Battistoni, H. Bilokon, C. Bloise, P. Campana, V. Chiarella, A. Ciocio, A. Grillo, E. Iarocci, A. Marini, A. Rindi, F. Ronga, L. Satta, M. Spinetti, L. Trasatti andV. Valente. Indiana:S. Ahlen, B. Brabson, R. Heinz, S. Mufson, H. Ogren andP. Smith. Michigan:J. Musser, J. Stone, L. Sulak andG. Tarlé. Pisa(**):C. Angelini, A. Baldini, C. Bemporad, A. Cnops, V. Flaminio, G. Giannini, R. Pazzi andB. Saitta. Roma(**):G. Auriemma, M. De Vincenzi, E. Lamanna, G. Martellotti, S. Petrera, L. Petrillo, P. Pistilli, G. Rosa, A. Sciubba andM. Severi. Texas A&M:R. Webb. Torino:M. Arneodo, G. Borreani, P. Giubellino, F. Marchetto, A. Marzari, S. Palestini andL. Ramello.Virginia Tech:S. Torres andP. Trower. (**) Sezione INFN e Dipartimento di Fisica dell'Università.     

Nonlinear waves in a waveguide partially filled with a plasma

Nonlinear waves have been studied in a circular waveguide partially filled with a cold magnetized collisionless plasma. The solution obtained is periodical with the frequency increasing as a square root of the amplitude of the solution in the first approximation.The author is indebted to K.Jungwirth, R.Klíma and J.Preinhaelter for valuable discussions.     

On the electric conductivity of BaTiO3 thin films

Results are presented of tests on the conductivity of BaTiO₃ and Ba(Ti, Sn)O₃ films obtained by various techniques and thickness order 1–100 m. Studies on electrical photoconductivity were conducted using ultraviolet radiation.The author wishes to thank R.Dytry, J.Genbar, J.Pawlik and R.Skulski for help in the experiments.     

Very low temperature properties of bosons with repulsive core and attractive tails

The properties of a system of bosons interacting through a two body potential composed of a hard repulsive core followed by an attractive square well and having density of the order of that of liquid⁴He at the-point have been studied. The system is found to have a peculiar behaviour around 1 K and we assert that it may have undergone another phase transition around 1 K. Calculations on the effective mass show that them ^*/m values lie between 2 and 9 so that the interacting bosons may have a transition temperature below 1 K. We have also plottedE _k vs.k graph for temperatures below 1 K.The authors are thankful to Prof. F. C.Auluck, Dr. N. R.Ranganathan, Dr. H. G.Venkatesh and Dr. A. N.Phukan for helpful discussion. Authors thanks are due to Prof. B. R.Seth, D.Sc., F.N.A., Director, B.I.T., Mesra for constant encouragement. The authors thankfully acknowledge the financial assistance provided by the Indian National Science Academy, New Delhi.     

Studies of light-charged particle emission in fission at Trombay

Studies of prompt radiations emitted in fission were started at Trombay in the late 1950’s by Dr R Ramanna and over the years extensive investigations on the emission of prompt neutrons, gamma ray and K x-rays in fission were carried out with neutron beams fromapsara andcirus reactors. In the early 1960’s studies on the emission of light-charged particles in fission, which is a rare mode of fission, were also started. This paper reviews some of the recent studies on the emission of light-charged particles (lcp) in fission which were carried out with a view to investigate the mechanism oflcp emission, the scission configuration and the dynamics of the last stages of the fission process.     

Finite nuclei in many body theory

An exact method of solution of the Goldstone equation for reaction matrix for finite nuclei is presented. The method can be applied to any double-magic nucleus if the two-nucleon potential does not contain a hard core. The basic properties of the nucleus, i.e. binding energy, nucleon densities, r.m.s. and formfactor are expressed with the help of reaction matrix and certain auxiliary quantities and related to the centre of mass motion.The author would like to express his gratitude to the Rutherford High Energy Laboratory for the possibility to perform this study and especially to Dr G. H.Stafford, Dr G.Manning, Dr R. J. N.Phillips and Dr C. J.Batty for their encouraging interest.     

One- and two-nucleon emission following the nuclear radiative pion capture

Decay channels in the radiative pion capture reactions are discussed and their respective yields calculated. Specific consequences of a recently suggested quadrupole excitation mode in the ( ^–,) reaction are found and their experimental investigation is urged. A yield of about 19% of the total decay was estimated for the two-nucleon decay channel even for the light nuclei like¹⁶O.On leave of absence fromthe Institute of Nuclear Physics, Czechosl. Acad. Sci., 250 68 e, Czechoslovakia.We a re grateful to the members of Lausanne-Münich-Zürich collaboration, particularly to C.Joseph, G.Strassner and P.Trüol for supplying us with the experimental results prior to publication. M. G. also thanks them and R.Wünsch for interesting discussions. We are grateful to R. A.Sakaev for his help at an early stage of this work.     

On ferromagnetic resonance damping in metals

The Landau-Lifshitz damping coefficient is defined in terms of spin-orbital torque correlations in the one-electron model and estimated as a function of the orbital collision frequency. The formal results are compared with previous studies and the results of a numerical calculation for nickel are compared with known experimental data.I would like to thank Dr. L.Hodges for a copy of his thesis and Dr. A. V.Gold, Dr. J. R.Anderson, Dr. V.Dvoák, Dr. Z.Frait and Mr. M.Kolá for valuable discussions at various stages of this work.     

On the Borel structure ofC*-algebras

We provide a method of embedding aC*-algebra in aC*-algebra called its -envelope. is contained in the enveloping algebra of but is generally much smaller, and if is commutative with identity then can be identified with the algebra of bounded Baire functions on the spectrum of. The main result is to completely determine the structure of for all separable G. C. R. algebras. This provides a good basis for a non-commutative theory of probability.We should like to thankJ. T. Lewis, G. W. Mackey andR. J. Plymen, who have given us considerable encouragement and insight into the quantum mechanical relevance of the ideas developed here.     

Note on wave propagation through a periodic rectangular wave-guide containing ferrite slabs

Wave propagation through a rectangular wave-guide loaded with periodic ferrite slabs has been considered. Numerical computations for the ratio of amplitudes and the phase shift has been made for the first three harmonics only.I take this opportunity of thanking Dr. S. C.Dasgupta and Dr. S. S.Baral for suggesting this investigation and for their guidance in preparing this note. I also wish to express my gratitude to the C.S.I.R. for financial support as a Senior Research Fellow.     

Vertical sea level meson-neutrino spectrum derived from the Goddard Space Flight Center measured nucleon spectrum

The vertical sea level meson neutrino spectrum has been derived from the measured primary nucleon spectrum of Goddard Space Flight Centre Group by using the model of Pal and Peters. The calculated result agrees with the work of Osborne et al. at high energies.The author is thankful to Prof.Yash Pal and Prof. J. L.Osborne for sending their works. Thanks are due to C.S.I.R., Govt. of India for financial support.     

Treatment of bcc transition metals on a modified CGW model

The vibrational spectrum and specific heat of three bcc transition metals -iron, chromium and tungsten are computed on the basis of modified Clark-Gazis-Wallis angular force model which considers volume forces of Krebs' nature. The calculations are made using the Blackman's root sampling technique for a discrete subdivision in wave-vector space. The calculated lattice specific heats and the effective Debye temperatures are compared with the available experimental data. The results show a reasonably satisfactory agreement with the experimental observations.The authors are highly thankful to Dr.Jyoti Prakash, Dr. S.Chandra for helpful discussions. One of them (H. L. K.) is thankful to C. S. I. R. India for the award of J. R. F. The computational facilities received from the I. I. T. Kanpur are also acknowledged.     

Vavilov-Cherenkov radiation in the biaxial triglycine sulphate crystal

Some properties of the Vavilov-Cherenkov radiation in the biaxial triglycine sulphate crystal have been analysed. The radiation properties have been studied for the cases of protons moving along the main three dielectric axes. The measurements were performed with the 660 MeV proton beam.A quantitative agreement of experiment with Muziká's theoretical calculations on the directional properties was observed. In all the cases a qualitative agreement concerning azimuthal distribution of the radiation intensity of the extraordinary waves of both polarities as well as concerning the polarization properties predicted by Obdrálek's formulae has been obtained.Dedicated to the Memory of Professor . Muziká.On leave from Department of Nuclear Physics, Comenius University, Bratislava, Czechoslovakia.The authors are grateful to Prof. V. P.Dzhelepov, Director of the Laboratory of Nuclear Problems, to Prof. L. I.Lapidus for support of the experiment as well as to Prof. L. M.Belyaev and I. V.Gavrilova (the Institute of Crystallography of the USSR Academy of Sciences) for supplying triglycine sulphate crystals, to J.Obdrálek (Charles University, Prague) for fruitful discussions and helpful advice, to Dr. R.Pose for assistance in obtaining negative colour film, to E.Janikova and R.Janik for great assistance in the experiment.     

On the connection between analyticity and lorentz covariance of wightman functions

We prove a conjecture ofR. Streater [1] on the finite covariance of functions holomorphic in the extended tube which are Laplace transforms of two tempered distributions with supports in the future and past cones. A new, slightly more general proof is given for a theorem of analytic completion of [1].     

HF heating of a plasma column at frequencies below the electron cyclotron frequency

Dispersion of waves, excited by the helical structure in a plasma column and the heating of a tail of the electron distribution function is studied at frequencies below the electron plasma and the electron cyclotron frequency.We wish to thank Dr. R.Klíma for valuable discussions and Dr. J.Lacina and Mrs. P.Jaroová for the computational work. We also thank Dr. L.Bárdo, Dr. L.Kryka and Dr. G. L.Khorosanov from Sukhumi Institute, USSR, for their help during different stages of the experiment. We are indebted to Mr. J.Dvoák, Mr. F.Jiránek and Mr. B.usta for their expert technical assistance.     

Diffusion-elastic phenomena II. Experiments

Measurements of diffusion-induced elastic deformation during diffusion of hydrogen through the double-layer Cu-Ni are compared with the previously described theoretical model. Diffusivities of hydrogen in Ni and Cu found on the basis of diffusion-elastic phenomena are compared with those obtained by other methods. Importance of these phenomena is discussed.The authors are grateful to Ing. R.Moudrá for the generally applicable program (in Tesla Fortran) for least-squares refinement and express their thanks to J.Vrtílková for her skill in performing the experiments and to Z.Hemanová for all careful computations.     

On the effect of trapped particles in the regime of cyclotron resonance

The motion of particles in a finite amplitude wave, propagating obliquely to the homogeneous magnetostatic field is discussed. As follows from simple integral properties, in the neighbourhood of Doppler-shifted cyclotron resonance similar trapping effects appear as in a plasma without magnetostatic field. Consequences of this trapping are discussed, in particular, the possibility of a strong absorption of the wave, and the origin of stochastic instabilities caused by the perturbation of an effective trapping potential and leading to the acceleration of particles.The author is indebted to Dr. R.Klíma, Dr. J.Lacina and Dr. P.unka for interesting discussions and to Dr. .Körbel, Mrs. P.Jaroová and Mrs. A.Harmáková for numerical calculations.     

The Clebsch-Gordan coefficients of SU(4)

A set of recurrence relations connecting the matrix elements of finite transformation belonging to the same irreducible representation of SU(4) is used to obtain a wide class of matrix elements. An expression for the Clebsch-Gordan coefficient is obtained by integrating the product of three matrix elements belonging to three different irreducible representations of the group. The symmetry properties of the matrix elements and the Clebsch-Gordan coefficients are discussed.The author is grateful to Professors S.Datta Majumdar and G.Bandyopadhyay of the Department of Physics, I.I.T., Kharagpur, for many helpful discussions. This work was supported by the C.S.I.R., Government of India.     

Caged H atom and H2 molecule in relation to Monte Carlo study of molecular dissociation at constant volume

Summary Analytic results for electronic kinetic energy are first presented for a hydrogen atom in a spherical cage for two radii near to the corresponding densities employed in the path-integral Monte Carlo study of isochoric molecular dissociation in dense hydrogen by Magroet al. (Magro W. R., Ceperley D. M., Pierleoni C. andBernu B.,Phys. Rev. Lett.,76 (1996) 1240). The relevance of the ?cage? results to the behaviour of dense atomic hydrogen is pointed out. Attention is then shifted to the molecular regime, and the variation with density of electronic kinetic energy for a H₂ molecule in a rigid spheroidal cage is compared and contrasted with the Monte Carlo findings. The rigid-cage model mimics this, as well as bond length contraction, under compression.     

Estimation of bond energies from mulliken overlap populations

Estimations of the bond energies from Mulliken overlap populations are taken. The strength of a bond is undoubtedly connected with the density of electrons constituting this bond. In the present paper the electron densities _i ^bond belonging to the particular bonds are represented by the total overlap populations defined byMulliken. The heat of atomization of the molecule is subdivide in the ratio of these electron densities _i ^bond belonging to the individual bond.My thanks are due to Drs. S.erný, Z.Knor, J.Pancí and R.Zahradník for their interest and stimulating discussions.