279 research outputs found
Tau Lepton Physics: Theory Overview
The pure leptonic or semileptonic character of tau decays makes them a good
laboratory to test the structure of the weak currents and the universality of
their couplings to the gauge bosons. The hadronic tau decay modes constitute an
ideal tool for studying low-energy effects of the strong interactions in very
clean conditions; a well-known example is the precise determination of the QCD
coupling from tau-decay data. New physics phenomena, such as a non-zero
tau-neutrino mass or violations of (flavour / CP) conservation laws can also be
searched for with tau decays.Comment: 20 pages, latex, 5 Postscript figures, uses espcrc2.sty, Invited Talk
at the Fourth International Workshop on Tau Lepton Physics (TAU96), Colorado,
September 199
Generalized screening theorem for Higgs decay processes in the two-doublet model
The radiative corrections to the decay processes of the neutral (-even)
Higgs boson () into a longitudinal gauge boson pair, {\it i.e.}, and are analyzed in
the two-Higgs doublet model by assuming that all of the Higgs boson masses are
much greater than the and bosons'. These calculations are motivated to
see if one could see potentially large virtual effects to these decay rates due
to the charged and -odd neutral Higgs boson masses ( and ,
respectively) which are supposed to be larger than . It is pointed out
that, although the radiative corrections to the decay width depend sensitively in general on and
, there occurs a screening effect, {\it i.e.,} cancellation in leading
terms once we set , so that the radiative corrections tend to be
minimized. It is also pointed out that the decay rate is fairly insensitive to the other heavier Higgs masses and is
possibly a good measuring tool of the Higgs mixing angle. The mechanism of
these screening phenomena in the Higgs decays is explained on the basis of a
new screening theorem, which we postulate with reference to the custodial
symmetry in the Higgs potential.Comment: 42 pages, latex, 9 figure
Distances walked in the six-minute walk test: suggestion of defining characteristic for the nursing diagnosis Ineffective Peripheral Tissue Perfusion
Distâncias percorridas em testes de marcha são importantes marcadores funcionais, porém, não são aceitos como características definidoras de Perfusão Tissular Periférica Ineficaz. Os objetivos foram verificar as distâncias percorridas no teste de caminhada de seis minutos, por participantes com e sem esse diagnóstico de enfermagem, e se tais medidas podem ser consideradas características definidoras desse fenômeno. A amostra foi composta por sujeitos com (grupo A, n=65) e sem (grupo B, n=17) Perfusão Tissular Periférica Ineficaz, avaliados quanto ao exame físico, à função vascular periférica e à capacidade funcional. Os participantes do grupo A apresentaram pior função vascular e capacidade funcional do que os do grupo B. Verificou-se que a distância percorrida livre de dor foi preditiva para a ocorrência do diagnóstico de enfermagem. Os resultados deste estudo são importantes para o refinamento desse diagnóstico. Conclui-se que as distâncias percorridas no teste de caminhada de seis minutos podem ser características definidoras de Perfusão Tissular Periférica Ineficaz.Las distancias en pruebas de marcha son importantes marcadores funcionales, pero no son aceptados como características de definición de la Perfusión Tisular Periférica Inefectiva. Los objetivos fueron determinar las distancias recorridas en la prueba de caminata de los seis minutos por los participantes con e sin el diagnóstico de enfermería y si esas medidas se pueden considerar características de definición de este fenómeno. Los participantes con (grupo A, n=65) y sin (grupo B, n=17) el diagnóstico fueron evaluados mediante examen físico, función vascular periférica y capacidad funcional. Los participantes del grupo A ha presentado peor función vascular y desempeño en la prueba de marcha do que aquellos del grupo B. La distancia recorrida libre de dolor fue predictiva del diagnóstico de enfermería. Los resultados de este estudio pueden contribuir para el refinamiento de este diagnóstico. Las distancias recorridas en la prueba de marcha se pueden considerar características de definición de este diagnóstico.Distances walked in walking tests are important functional markers, although they are not accepted as defining characteristics of Ineffective Peripheral Tissue Perfusion. The aims of this study were to verify the distances participants with and without this nursing diagnosis walked in the six-minute walk test and if these measures may be considered defining characteristics of this phenomenon. Participants with (group A; n=65) and without (group B; n=17) this nursing diagnosis were evaluated regarding physical examination, vascular function and functional capacity. Participants of group A seemed to have worse vascular function and functional capacity compared with those of group B. Pain-free travelled distance was predictive of the nursing diagnosis. These results are important for the refinement of this diagnosis. In conclusion, this study provides evidences that the distances walked in the six-minute walk test may be considered defining characteristics of Ineffective Peripheral Tissue Perfusion
Parity-Violating Excitation of the \Delta(1232): Hadron Structure and New Physics
We consider prospects for studying the parity-violating (PV) electroweak
excitation of the \Delta(1232) resonance with polarized electron scattering.
Given present knowledge of Standard Model parameters, such PV experiments could
allow a determination of the N -> \Delta electroweak helicity amplitudes. We
discuss the experimental feasibility and theoretical interpretability of such a
determination as well as the prospective implications for hadron structure
theory. We also analyze the extent to which a PV N -> \Delta measurement could
constrain various extensions of the Standard Model.Comment: 43 pages, RevTex, 8 PS figures, uses epsf.sty, rotate.sty, version to
appear in Nucl. Phys. A, main points emphasized, some typos correcte
Magnetic Monopoles As a New Solution to Strong CP Problem
A non-perturbative solution to strong CP problem is proposed. It is shown
that the gauge orbit space with gauge potentials and gauge tranformations
restricted on the space boundary in non-abelian gauge theories with a
term has a magnetic monopole structure if there is a magnetic monopole in the
ordinary space. The Dirac's quantization condition in the corresponding quantum
theories ensures that the vacuum angle in the gauge theories must be
quantized. The quantization rule is derived as with n
being the topological charge of the magnetic monopole. Therefore, we conclude
that the strong CP problem is automatically solved non-perturbatively with the
existence of a magnetic monopole of charge with . This
is also true when the total magnetic charge of monopoles are very large
() if it is consistent with the abundance of magnetic
monopoles. This implies that the fact that the strong CP violation can be only
so small or vanishing may be a signal for the existence of magnetic monopoles.Comment: LBL-32491, June, 199
T Violation Induced by Supersymmetry in t\bar{t} and W^+W^- Physics
T-odd correlations of polarizations and momenta provide a promising testing
ground for new physics beyond the standard model. We estimate the contribution
of the minimal supersymmetric extension of the standard model to two such
observables: in the production of , we look for a term proportional
to \mbox{}-where {\bf J} is
the polarization of the quark and {\bf p} are the momenta of the
initial and final particles-and find that it is of the order of . In the production of , we look for a term proportional
to \mbox{}-where {\bf E} is the transverse polarization of W- to find that it
can be as large as .Comment: 16 pages (8 figures, not included
Quantisation of Monopoles with Non-abelian Magnetic Charge
Magnetic monopoles in Yang-Mills-Higgs theory with a non-abelian unbroken
gauge group are classified by holomorphic charges in addition to the
topological charges familiar from the abelian case. As a result the moduli
spaces of monopoles of given topological charge are stratified according to the
holomorphic charges. Here the physical consequences of the stratification are
explored in the case where the gauge group SU(3) is broken to U(2). The
description due to A. Dancer of the moduli space of charge two monopoles is
reviewed and interpreted physically in terms of non-abelian magnetic dipole
moments. Semi-classical quantisation leads to dyonic states which are labelled
by a magnetic charge and a representation of the subgroup of U(2) which leaves
the magnetic charge invariant (centraliser subgroup). A key result of this
paper is that these states fall into representations of the semi-direct product
U(2) \semidir R^4. The combination rules (Clebsch-Gordan coefficients) of
dyonic states can thus be deduced. Electric-magnetic duality properties of the
theory are discussed in the light of our results, and supersymmetric dyonic BPS
states which fill the SL(2,Z)-orbit of the basic massive W-bosons are found.Comment: 57 pages, harvmac, amssym, two eps figures, minor mistakes and typos
corrected, references added; to appear in Nucl. Phys.
Unitarity of Little Higgs Models Signals New Physics of UV Completion
The ``Little Higgs'' opens up a new avenue for natural electroweak symmetry
breaking in which the standard model Higgs particle is realized as a
pseudo-Goldstone boson and thus is generically light. The symmetry breaking
structure of the Little Higgs models predicts a large multiplet of
(pseudo-)Goldstone bosons and their low energy interactions below the
ultraviolet (UV) completion scale TeV, where
is the Goldstone decay constant. We study unitarity of the Little Higgs
models by systematically analyzing the high energy scatterings of these
(pseudo-)Goldstone bosons. We reveal that the collective effect of the
Goldstone scatterings via coupled channel analysis tends to push the unitarity
violation scale significantly below the conventional UV scale
as estimated by naive dimensional analysis (NDA).
Specifically, , lying in the multi-TeV range for TeV. We interpret this as an encouraging sign that the upcoming LHC may
explore aspects of Little Higgs UV completions, and we discuss some potential
signatures. The meanings of the two estimated UV scales (from
unitarity violation) and (from NDA) together with their implications
for an effective field theory analysis of the Little Higgs models are also
discussed.Comment: To match Phys.Lett.B version (9pp, only minor rewording
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