Naturally Degenerate Neutrinos

The solar neutrino problem, atmospheric neutrino problem, and the existence of hot dark matter can all be economically accounted for using only the three known neutrinos if these neutrinos all have nearly degenerate masses of a few eV. We show how to generate this pattern of neutrino masses in a natural way within a `see-saw' framework.Comment: 10 pages, plain TeX, McGill-94/07, NEIP-94-003 (This is the version which is to appear in the journal. We have cleaned up typos, added references, and slightly expanded our treatment of radiative corrections.

Shifting RbR_b with AFBbA^b_{FB}

Precision measurements at the $Z$ resonance agree well with the standard model. However, there is still a hint of a discrepancy, not so much in $R_b$ by itself (which has received a great deal of attention in the past several years) but in the forward-backward asymmetry $A^b_{FB}$ together with $R_b$. The two are of course correlated. We explore the possibilty that these and other effects are due to the mixing of $b_L$ and $b_R$ with one or more heavy quarks.Comment: 11 pages, 1 Figure, LaTex fil

Regional wall stiffness during acute myocardial ischaemia in the canine left ventricle

In eight anaesthetized closed-chest dogs, acute myocardial ischaemia was produced for 30 to 90 s by inflating a small balloon-catheter, which had been advanced transaortically into the periphery of the left anterior descending coronary artery. Left ventricular high-fidelity pressure measurements and simultaneous angiocardiography were carried out at control and during ischaemia. Left ventricular systolic function was assessed by the left ventricular ejection fraction (EF) as well as by regional shortening in a basal (SH M1), middle (SH M2 and apical (SH M3) segment. Diastolic function was evaluated by the stress-strain relationship using a viscoelastic model. Regional wall stiffness (Kn) was determined in the same three segments (basal, middle and apical), which were used for the evaluation of regional systolic function. For the interindividual comparison of the diastolic stiffness parameters normalization of the strain data was performed by calculating a reference wall circumference (I0) at a common wall stress of 1000 dynes/cm2. During localized myocardial ischaemia left ventricular end-diastolic pressure remained essentially unchanged (7.2 v. 8.3 mm Hg: NS). Left ventricular EF (47 v. 31% P < 0.001), SH M2 (27 v. 14 % P < 0.005) and SH M3 (22 v. 2% P < 0.02) decreased during ischaemia. Kn in the middle (10.0 v. 14.2; P < 0.02) and the apical (9.8 v. 12.7, P < 0.005) segment increased during ischaemia whereas Kn in the non-ischaemic basal segment remained unchanged (9.6 v. 11.8; NS). During ischaemia I0 increased in the middle segment (15.7 v. 17.3 cm; P < 0.005). Our data indicate that during acute ischaemia regional myocardial wall stiffness is increased in the ischaemic segment, but is normal in the non-ischaemic segment. Reference midwall circumference at a common wall stress of 1000 dynes/cm2 is enhanced during acute ischaemia (creep) and corresponds with the increased sarcomere length reported in ischaemic myocardium. Thus, it is suggested that the changes in regional myocardial wall stiffness are related to changes in reference midwall circumference with cree

Extra quark-lepton generations and precision measurements

The existence of extra chiral generations with all fermions heavier than M_Z is strongly disfavoured by the precision electroweak data. However the data are fitted nicely even by a few extra generations, if one allows neutral leptons to have masses close to 50 GeV. The data allow inclusion of one additional generation of heavy fermions in SUSY extension of Standard Model if chargino and neutralino have masses close to 60 GeV with \Delta m =~ 1 GeV.Comment: 14 pages, 5 figure

Isotopic Composition of the Solar Wind Inferred from In-Situ Spacecraft Measurements

The Sun is the largest reservoir of matter in the solar system, which formed 4.6Gyr ago from the protosolar nebula. Data from space missions and theoretical models indicate that the solar wind carries a nearly unfractionated sample of heavy isotopes at energies of about 1keV/amu from the Sun into interplanetary space. In anticipation of results from the Genesis mission's solar-wind implanted samples, we revisit solar wind isotopic abundance data from the high-resolution CELIAS/MTOF spectrometer on board SOHO. In particular, we evaluate the isotopic abundance ratios 15N/14N, 17O/16O, and 18O/16O in the solar wind, which are reference values for isotopic fractionation processes during the formation of terrestrial planets as well as for the Galactic chemical evolution. We also give isotopic abundance ratios for He, Ne, Ar, Mg, Si, Ca, and Fe measured in situ in the solar win

THE SENSITIVITY TO NEW PHYSICS OF A LEP SCAN IN 1995

We study the implications of possible off-peak measurements in the 1995 LEP run, in regard to probing physics beyond the Standard Model. To do so, we determine the accuracy with which various nonstandard couplings can be expected to be measured in the three different scan scenarios recently discussed by Clarke and Wyatt. We find that each scan scenario allows greater sensitivity to a different set of new physics couplings. Oblique parameters are best measured with the longest scan, while nonstandard fermion couplings to the Z tend to be better constrained (albeit only marginally) if all of the 1995 LEP measurements are taken on the Z peak.Comment: Plain TeX, 9 pages, no figures. We have streamlined our presentation by omitting observables of our Class B. All else is completely unchanged

An Elusive Z' Coupled to Beauty

By extending the standard gauge group to SU(3)_c \times SU(2)_L \times U(1)_Y \times U(1)_X with X charges carried only by the third family we accommodate the LEP measurement of R_b and predict a potentially measurable discrepancy in A_{FB}^{b} in e^+e^- scattering and that D^0\bar{D}^0 mixing may be near its experimental limit. The Z', which explicitly violates the GIM mechanism, can nevertheless be naturally consistent with FCNC constraints. Direct detection of the Z' is possible but challenging.Comment: 12 pages, plus 1 Postscript figure, uses revtex, Discussion of FCNC extende

Competition between standard and exotic double beta decays

We discuss the contributions of higher order terms in weak Hamiltonian to the standard two-neutrino double beta decay. The formalism for the unique first forbidden transitions has been developed, and it is shown that they can alter the two-electron energy spectrum. Yet, their effect is too small to screen the detection of exotic neutrinoless double beta decays, which are candidates for testing the physics beyond the standard model.Comment: 9 pages, latex, 1ps figures, minor changes, to appear in Phys. Lett.

NEW PHYSICS AND RECENT HIGH PRECISION ELECTROWEAK MEASUREMENTS

We analyze LEP and SLC data from the 1995 Winter Conferences for signals of new physics. We compare the data with the Standard Model (SM) as well as a number of test hypotheses concerning the nature of new physics: (i) nonstandard Zbb couplings, (ii) nonstandard Zff couplings for the entire third generation, (iii) nonstandard oblique corrections, (iv) nonstandard lepton couplings, (v) general nonstandard W and Z couplings to all fermions, as well as combinations of the above. In most of our analyses, we leave the SM variables $\alpha_s$ and $m_t$ as free parameters to see how the various types of new physics can affect their inferred values. We find that the best fit ($\chi^2/d.o.f. = 8.4/10$) is obtained for the nonstandard Zbb couplings, which also give a `low' value (0.112) for $\alpha_s$. The SM also gives a good description of the Z data, having $\chi^2/d.o.f. = 12.4/12$. If $\alpha_s$ is held fixed to the low-energy value 0.112, then we find that a combination of the nonstandard Zbb couplings is fit to lie more than four standard deviations away from zero.Comment: Plain TeX, 9 pages, one figure (uuencoded), and 8 table