5,767 research outputs found
Leptonic Flavor and CP Violation
We discuss how neutrino oscillation experiments can probe new sources of
leptonic flavor and CP violation.Comment: 8 pages, latex, no figures. Invited talk given at KAON 2001, Pisa,
Italy, June 12 - 17, 200
Bottleneck effects in turbulence: Scaling phenomena in r- versus p-space
We (analytically) calculate the energy spectrum corresponding to various
experimental and numerical turbulence data analyzed by Benzi et al.. We find
two bottleneck phenomena: While the local scaling exponent of the
structure function decreases monotonically, the local scaling exponent
of the corresponding spectrum has a minimum of
at and a maximum
of at . A physical
argument starting from the constant energy flux in p--space reveals the general
mechanism underlying the energy pileups at both ends of the p--space scaling
range. In the case studied here, they are induced by viscous dissipation and
the reduced spectral strength on the scale of the system size, respectively.Comment: 9 pages, 3figures on reques
Constraining Models of New Physics in Light of Recent Experimental Results on
We study extensions of the Standard Model where the charged current weak
interactions are governed by the CKM matrix and where all tree-level decays are
dominated by their Standard Model contribution. We constrain both analytically
and numerically the ratio and the phase difference between the New Physics and
the Standard Model contributions to the mixing amplitude of the neutral
system using the experimental results on , ,
and . We present new results concerning models with minimal
flavor violation and update the relevant parameter space. We also study the
left-right symmetric model with spontaneously broken CP, probing the viability
of this model in view of the recent results for and other
observables.Comment: 32 pages, including 9 figures, typos and error in fig. 1 corrected,
minor modificiation in the text, conclusions unchanged, to appear in PR
Tau Polarization in and
We discuss the longitudinal and transverse -polarization in inclusive
decays of hadrons containing -quarks. The calculation is performed by means
of an OPE in HQET. Some mathematical difficulties in calculating transverse
polarizations are explained. Numerical results are presented for longitudinal
and for transverse polarizations, both in and perpendicular to the decay plane.Comment: LATEX, 20 pages, 5 Postscript figure
Light Lepton Number Violating Sneutrinos and the Baryon Number of the Universe
Recent results of neutrino oscillation experiments point to a nonvanishing
neutrino mass. Neutrino mass models favour Majorana-type neutrinos. In such
circumstances it is natural that the supersymmetric counterpart of the
neutrino, the sneutrino, bears also lepton number violating properties. On the
other hand, the fact that the universe exhibits an asymmetry in the baryon and
antibaryon numbers poses constraints on the extent of lepton number violation
in the light sneutrino sector if the electroweak phase transition is second or
weak first order. From the requirement that the Baryon Asymmetry of the
Universe should not be washed out by sneutrino induced lepton number violating
interactions and sphalerons below the critical temperature of the electroweak
phase transition we find that the mass splitting of the light sneutrino mass
states is compatible with the sneutrino Cold Dark Matter hypothesis only for
heavy gauginos and opposite sign gaugino mass parameters.Comment: 13 pages, 4 figure
New scalar resonances from sneutrino-Higgs mixing in supersymmetry with small lepton number (R-parity) violation
We consider new s-channel scalar exchanges in top quark and massive
gauge-bosons pair production in e+e- collisions, in supersymmetry with a small
lepton number violation. We show that a soft bilinear lepton number violating
term in the scalar potential which mixes the Higgs and the slepton fields can
give rise to a significant scalar resonance enhancement in e+e- -> ZZ, W+W- and
in e+e- -> t t(bar). The sneutrino-Higgs mixed state couples to the incoming
light leptons through its sneutrino component and to either the top quark or
the massive gauge bosons through its Higgs component. Such a scalar resonance
in these specific production channels cannot result from trilinear Yukawa-like
R-parity violation alone, and may, therefore, stand as strong evidence for the
existence of R-parity violating bilinears in the supersymmetric scalar
potential. We use the LEP2 measurements of the WW and ZZ cross-sections to
place useful constrains on this scenario, and investigate the expectations for
the sensitivity of a future linear collider to these signals. We find that
signals of these scalar resonances, in particular in top-pair production, are
well within the reach of linear colliders in the small lepton number violation
scenario.Comment: 22 pages in revtex, 10 figures embadded in the text using epsfi
Some Remarks on the Neutrino Oscillation Phase in a Gravitational Field
The weak gravitational field expansion method to account for the
gravitationally induced neutrino oscillation effect is critically examined. It
is shown that the splitting of the neutrino phase into a ``kinematic'' and a
``gravitational'' phase is not always possible because the relativistic factor
modifies the particle interference phase splitting condition in a gravitational
field.Comment: 4 pages, no figure
Two-Loop Large- Electroweak Corrections to for Arbitrary Higgs Boson Mass
We consider for the first time the leading large top mass corrections,
arising at higher order in electroweak interactions, to the rare decays
and the related modes and . Higher order effects of similar type have previously been calculated
in the large- limit for key observables of precision electroweak physics
at Z-factories. Here we obtain the corresponding corrections of order at the amplitude level for short-distance dominated rare meson
decays. This allows us to quantify the importance of higher order electroweak
effects for these processes, which can be reliably computed and have very small
uncertainties from strong interactions. Simultaneously it becomes possible to
remove, to some extent, ambiguities in the definition of electroweak parameters
describing the strength of FCNC interactions. The corrections we discuss are at
the level of a few percent.Comment: 11 pages, LaTeX, 1 eps-figur
Anomalous Thermal Stability of Metastable C_20 Fullerene
The results of computer simulation of the dynamics of fullerene C_20 at
different temperatures are presented. It is shown that, although it is
metastable, this isomer is very stable with respect to the transition to a
lower energy configuration and retains its chemical structure under heating to
very high temperatures, T ~ 3000 K. Its decay activation energy is found to be
E_a ~ 7 eV. Possible decay channels are studied, and the height of the minimum
potential barrier to decay is determined to be U = 5.0 eV. The results obtained
make it possible to understand the reasons for the anomalous stability of
fullerene C_20 under normal conditions.Comment: Slightly corrected version of the paper submitted to Phys. Solid
Stat
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