Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 1996"

On a new method to measure the gravitomagnetic field using two orbiting satellites

Abstract: We describe a new method to obtain the first direct measurement of the Lense-Thirring effect, or dragging of inertial frames, and the first direct detection of the gravitomagnetic field. This method is based on the observations of the orbits of the laser-ranged satellites LAGEOS and LAGEOS II. By this new approach one achieves a measurement of the gravitomagnetic field with accuracy of about 25%, or less, of the Lense-Thirring effect in general relativity.

The helicity of the free electromagnetic field and its physical meaning

Abstract: The notion of helicity for the free electromagnetic field is analysed. The generalized helicity is introduced which is a conserved quantity coinciding with the difference of the right and left circularly polarized photons composing the electromagnetic field. It seems that it completes the list of the zilch-type invariants found by Lipkin and Ragusa. The gauge-invariant expression for the energy of the free gravitational field is obtained which strongly resembles the well-known bilinear expression for the total number of photons composing the electromagnetic field.

Investigation of the baryon electromagnetic structure by polarization effects in e+e−→B $$\overline B $$ processesprocesses

Abstract: Polarization effects in e+e−→B\(\overline B \) processes are investigated from various aspects. The explicit form of vector polarization components of the created baryon B and components of the tensor of polarization correlations of B and\(\overline B \) in the annihilation of unpolarized and polarized e+e− colliding beams is presented. The sensitivity in the behaviour of the vector polarization components of the nucleon is demonstrated graphically by using two recent formulations of the unitary and analytic VMD model of the nucleon electromagnetic structure.

Measurement of dragging of inertial frames and gravitomagnetic field using laser-ranged satellites

Abstract: By analysing the observations of the orbits of the laser-ranged satellites LAGEOS and LAGEOS II, using the program GEODYN, we have obtained the first direct measurement of the Lense-Thirring effect, or dragging of inertial frames, and the first direct experimental evidence for the gravitomagnetic field. The accuracy of our measurement is of about 30%.

Calibration with relativistic and low-velocity ions of a CR39 nuclear track detector

Abstract: We present experimental results on the calibration of the CR39 nuclear track detector, manufactured by the Intercast Europe Co., of Parma (Italy). The calibration was performed with several ions of different kinetic energies: from 50 keV protons to 11.3A GeV gold ions; β=v/c ranges from about 4·10−3 to about 1. We find that a single curve of the reduced etch ratep vs. restricted energy loss is able to describe all data. Furthermore the data are consistent with about 100% contribution of the nuclear energy loss to the CR39 response. This type of CR39 is used in the MACRO experiment at the Gran Sasso Laboratory.

On gauge invariance of Yang-Mills theories with matter fields

Abstract: We continue the investigation of quantied Yang-Mills theories coupled to matter fields in the framework of causal perturbation theory. In this approach, which goes back to Epstein and Glaser, one works with free fields throughout, so that all expressions are mathematically well defined. The general proof of theCg-identities (C-number identities expressing gauge invariance) is completed. We attach importance to the correct treatment of the degenerate terms and to theCg-identities with external matter legs. Moreover, the compatibility of allCg-identities withP-, T-, C-invariance and pseudo-unitarity is shown.

On the hierarchy of quark mixings

Abstract: We point out that the structure of the 3×3 quark mixing matrixV is characterized by its two off-diagonal asymmetries: one about theV11–V22–V33 axis (Open image in new window) and the other about theV13−V22−V31 axis (Open image in new window). By use of current experimental data, we obtainOpen image in new window∼10−5−10−4 andOpen image in new window⩾400Open image in new window. We find a definite hierarchy for the magnitudes of quark mixings: |V33|>|V11|>|V22|≫|V12|>|V21|≫≫|V23|>|V32|≫|V31|>|V13|>0. The useful relations between the off-diagonal asymmetriesOpen image in new window and the unitarity triangles ofV are also explored.

Multichannel approach to studying scalar resonances

Abstract: TheN-channel formalism (in more detail, 2- and 3-channel) is presented which is based on such general principles, as analyticity and unitarity, and realizes an idea of the consistent account of the nearest (to the considered physical region) singularities on all sheets of the Riemann surface of theS-matrix, thus giving a chance to obtain model-independent information on multichannel resonances from the analysis of data on the coupled processes. The resonance representations by pairs of complex-conjugate clusters of poles and zeros on the Riemann surface and the conception of standard clusters as a model-independent test of the resonance presence are discussed. The role of closed channels in forming resonances and fictitious states is investigated. The method is exemplified with the isoscalars-wave channel of coupled processes ππ→ππ, K\(\overline K \), ππ and with analysing ππ scattering up to 1.9 GeV and scalar resonances.

On the broken gauge, conformal and discrete symmetries in particle physics

Abstract: Relationships between gauge, conformal and discrete symmetries in particle physics are analysed. We study also the effect of the electroweak mixing on the cancellation ofSU(2) anomalous actions. It is shown that the relation {ie1535-1} between the Weinberg angle and the Cabibbo-Kobayashi-Maskawa angles should be satisfied and this effect is completely defined by the mixing of Dirac fermions. We compare two mechanisms of the spontaneous breaking of gauge symmetry, discuss the renormalizability of theories, and argue for the existence of the Majorana fermions necessary to remove theSU(2) anomalous action. The fate of the majoron and the spontaneously broken lepton number is discussed. We also show the compatibility of the boson and fermion mixings with Dyson-Schwinger equations.

Instanton-induced soft-pion wave function and hard-pion form factor

Abstract: An instanton-induced pion wave function is constructed. It provides an intrinsick⊥-dependence which suppresses soft virtual one-gluon exchanges and thus legitimates the perturbative QCD (pQCD) calculations of the pion electromagnetic form factor in the region of momentum transfers above the scaleQc>(√3/(2√f))(1/ϱc)∼1 GeV, wheref=(2nc)(π2πc4/2) is a packing fraction parameter, ϱc is an effective instanton size andnc is an effective density of instantons in the instanton vacuum of QCD.

External electron pair production in high-energy collisions

Abstract: External electron pair production is studied in the interaction of high-energy heavy ions with nuclear emulsions. The possibility of the production of neutral bosons is examined at the two energies 3.6A GeV and 200A GeV. The data seem to suggest the production and subsequent decay of short-lived neutral bosons with lifetimes of the order of 10−16–10−15s and with masses consistent with the theoretically predicted resonances.

Lifetimes of heavy-flavour hadrons—whence and whither?

Abstract: A theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology as it applies to total lifetimes and the underlying theoretical issues are sketched. Predictions are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than expected. The ramifications of those findings are analyzed in detail.

Vacuum stability in quantum field theory

Abstract: It is shown that the adiabatic (infrared) limit of vacuum diagrams does not exist in theories with self-interacting massless fields (QCD) or massless interacting particles (massless QED), if the theory is renormalizable. It does exist in quantum gravity.

Exponential and Wolfenstein parametrizations of the CKM matrix

Abstract: The derivation of the Wolfenstein form of the Cabibbo-Kobayashi-Maskawa matrix\(\hat V\) from exponential parametrization is discussed. It is proved that at orderλ3 a one-to-one correspondence exists between the Wolfenstein parameters and the entries of matrix\(\hat A\) that generates\(\hat V\). The importance of exponential parametrization in generating mass matrices is analysed. The usefulness of the entries of\(\hat A\) in analysing the experimental data is also discussed.

A Revised Proof of the Existence of Negative Energy Density in Quantum Field Theory

Abstract: Negative energy density is unavoidable in the quantum theory of field. We give a revised proof of the existence of negative energy density unambiguously for a massless scalar field. 03.65.Sq, 03.70.+k, 05.40.+j Typeset using REVTEX 1

Real part of the scattering amplitude and model analysis

Abstract: The real part of the forward-scattering amplitude is analytically evaluated by means of dispersion relations. Applications to phenomenological model analysis are discussed.

Defect kinetics in silicon detector material

Abstract: A numerical model based on experimental data has been used to investigate the evolution of atomic defects in high-resistivity dtector material during neutron irradiation to levels expected at the CERN LHC. The complexes V2O and V3O have been identified as candidates for deep-level acceptor states which give rise to experimentally observed changes in the effective doping concentration. The phosphorus dopant is removed by production of VP centres but at a rate lower than previously hypothesised and not fully, even after heavy irradiation. The importance of initial oxygen and carbon impurity concentrations is demonstrated in determining the radiation tolerance of the detectors. A hypothesis for the long-term annealing behaviour via the thermal annealing of a trivacancy (V3) state during heavy-particle irradiation is modelled and shown to be a possible explanation of experimental observations.

Investigation of thermoluminescent properties of synthetic (CVD) diamond

Abstract: Thermoluminescent properties of three samples of synthetic diamond obtained by chemical vapor deposition (CVD) were investigated. The thermoluminescent response of the three samples was observed increasing linearly with radiation exposure over a wide range of doses (from 60 mGy up to 3 Gy). The measurement of their activation energies and frequency factors are reported. First-order kinetics was observed in the three cases.

Twistors, torsion and quantization of space-time

Abstract: The analogies between twistors and torsion are developed. TheSL(2,C) group of transformations is used to suggest a unified link between the approaches. The role of space-time defects in the quantization of space-time is clarified and commutation relations between conjugate twistor variables suggested. Finally the incorporation of mass and charge as well as supersymmetry in the formalism is considered.

CP Violation and Flavour Mixing in the Standard Model

Abstract: We review and update the constraints on the parameters of the quark flavour mixing matrixV CKM in the Standard Model and estimate the resultingCP asymmetries in B decays, taking into account recent experimental and theoretical developments. In performing our fits, we use inputs from the measurements of the following quantities: i) |e|, theCP-violating parameter in K decays, ii) ΔM d, the mass difference due to the $$B_{d^ - }^0 \bar B_d^0 $$ mixing, iii) the matrix elements |V cb| and |V ub|, iv)-v) has improved compared to our previous fits. With the updated CKM matrix we present the currently-allowed range of the ratios |V td/V ts| and |V td/V ub|, as well as the Standard Model predictions for the $$B_{s^ - }^0 \bar B_s^0 $$ mixing parameterx s (or, equivalently, ΔM s) and the quantities sin2α, sin2β and sin2γ, which characterize theCP-asymmetries in B decays. Various theoretical issues related to the so-called «penguin-pollution», which are of importance for the determination of the phases α and γ from theCP-asymmetries in B decays, are also discussed.

Heavy-flavour phenomenology from lattice QCD (*)

Abstract: The latest results on several weak hadronic amplitudes that have been computed in numerical simulations are reviewed. Many of these results have already had, or are expected to have, a significant impact on the phenomenology of weak interactions, and in particular on our understanding ofCP violation. The main topics discussed in this review are: leptonic decay constants of pseudoscalar heavy-light mesons, B-\(\bar B\) mixing amplitudes, semi-leptonic decays of D and B mesons, radiative decays of B mesons and the Isgur-Wise function.

Investigation of anomalous heat production in Ni−H systems

Abstract: Anomalous heat production in a nickel rod loaded with hydrogen has been reported by Focardiet al. (Nuovo Cimento A,107 (1994) 163). We have investigated this phenomenon by repeating the experiment. We found the results previously published to be consistent with our observations; namely we measured higher temperatures for the same input power when hydrogen is absorbed during a heating cycle. Nevertheless this temperature rise does not appear to correspond to an increase in heat production. We have added a temperature sensor to the container of the experiment. The temperature of the container follows the same temperature with input power curve irrespective of whether there is an anomalous absorption of hydrogen or not; therefore we have no evidence that this temperature increase corresponds to another source of heat. In conclusion, we have observed all the effects discovered by Focardiet al., but our results imply that there is no production of power associated with the absorption of hydrogen by nickel.

State of the art of wide-bandgap semiconductor nuclear radiation detectors

Abstract: The leading materials which operate as room temperature nuclear radiation detectors are HgI2, CdTe, and Cd1−xZnxTe (0.05>x>0.25). However, additional materials have also been developed, such as semi-insulating GaAs and PbI2. A comparison of the charge transport properties of all these materials will be made, followed by a discussion of each of the materials separately. Crystal growth methods of spectrometer-grade materials will be mentioned, and defects which limit their performance will be discussed. Nuclear spectra measurements with detectors fabricated from these materials, for low X-ray energies as well as for high-energy gamma-rays, will be shown. Polarization effects which occur in some detectors such as HgI2 will also be discussed. Correlation between crystalline perfection and detector performance will be shown. Results of quantitative chemical analysis of various detector materials and problems encountered in determining accurate values ofx in Cd1−xZnxTe and its homogeneity in the bulk will be presented. Finally, the present state of the art and developments for the near future will be discussed.

Model-independent semi-leptonic form factors using dispersion relations (*)

Abstract: We present a method for parametrizing heavy-meson semi-leptonic form factors using dispersion relations, and from it produce a two-parameter description of the B→B elastic form factor. We use heavy-quark symmetry to relate this function to $$\bar B \to D*\ell \bar v$$ form factors, and extract |V cb|=0.0355 −0.0025 +0.0029 from experimental data with a least-squares fit. Our method eliminates model-dependent uncertainties inherent in choosing a parametrization for the extrapolation of the differential decay rate to threshold.

New developments on silicon drift detectors

Abstract: In the frame of the project to develop large-area linear drift detectors few prototypes have been designed and produced. The function of these prototypes is to allow the evaluation of the solutions chosen for the geometry of the an-board electrodes and the production process. On these prototypes we have studied the static characteristics and measured time-of-flight and charge collection injecting charges with an IR laser source. We report the results from one of the prototypes.

Radiation effects on breakdown in silicon multiguarded diodes

Abstract: We have investigated the current-voltage characteristics of silicon PIN diodes with a number of different multiguard structures. These structures were designed to increase the overall device breakdown voltage. The same measurements were carried out after gamma irradiation at different doses and neutron irradiation at fluences beyond type-inversion. This study is a first step towards defining guard structures optimized for operation in high-radiation environments such as those expected at the LHC.

Some characteristics of produced particles in16O-emulsion collisions at different relativistic energies

Abstract: The charged-particle multiplicities produced in inelastic interactions of16O ions at 3.7 and 60A GeV with emulsion nuclei are investigated and compared with theoretical predictions. Results from the interaction with CNO and AgBr target nuclei are analysed in terms of negative binomial (NB) distribution. Data from other nucleus-emulsion collision experiments have been used to fit an empirically proposed relationship for the average value of total charged multiplicity as a function of the geometrically determined number of interacting nucleons.

Low-lying negative-parity bands in heavy nuclei: A phenomenological approach

Abstract: A phenomenological analysis of theKπ=0−, 1−, 2− band spectra in actinides and few rare-earth nuclei is carried out within the coherent state model using an interacting boson Hamiltonian which includes quadrupole and octupole bosons. The bands are described as octupole boson excitations of intrinsic coherent wave functions associated to the model ground, beta and gamma bands. The calculation reproduces all available experimental energy spectra up to high angular momenta. Also theE1 branching ratios are fairly well reproduced. Different signatures of static octupole deformation are discussed.

Feasibility of extractingV td from radiative B(Bs) decays

Abstract: We use experimental information on D-→K*0ϱ- and B→ψ+K*, coupled with flavor independence of QCD, and with vector meson dominance to show that long-distance contributions to B→ϱ+γ, especially B-→ϱ-+γ, are potentially very serious. Estimates based on the annihilation graph are shown to lead to similar conclusions. We emphasize that long-distance (LD) contributions can be appreciably different in B-→ϱ-+γ and B0→ϱ0(ω)+γ. All radiative decays of B, Bs are shown to be governed essentially by two LD and two short-distance (SD) hadronic entities. Despite the presence of considerable LD contributions, we show how separate measurements of B-→ϱ-+γ, B0→ϱ0(ω)+γ, along with the B→K*+γ can be used for a systematic extraction ofV td. Measurements of Bs→ϕ+γ and K*0+γ could also provide very useful consistency checks.

Singular Minkowski and Euclidean solutions forSU(2) Yang-Mills theory

Abstract: In this paper we examine a solution to theSU(2) Yang-Mills-Higgs system, which is a trivial mathematical extension of recently dicovered Schwarzschild-like solutions (Singleton D.,Phys. Rev. D,51 (1955) 5911). Physically, however, this new solution has drastically different properties from the Schwarzschild-like solutions. We also study a new classical solution for EuclideanSU(2) Yang-Mills theory. Again this new solution is a mathematically trivial extension of the Belavin-Polyakov-Schwartz-Tyupkin (BPST) (Belavin A. A.et al., Phys. Lett. B,59 (1975) 85) instanton, but is physically very different. Unlike the usual instanton solution, the present solution is singular on a sphere of arbitrary radius in Euclidean space. Both of these solutions are infinite-energy solutions, so their practical value is somewhat unclear. However, they may be useful in exploring some of the mathematical aspects of classical Yang-Mills theory.