2,340 research outputs found
Use of W-Boson Longitudinal-Transverse Interference in Top Quark Spin-Correlation Functions: II
This continuation of the derivation of general beam-referenced stage-two
spin-correlation functions is for the analysis of top-antitop pair-production
at the Tevatron and at the Large Hadron Collider. Both the gluon-production and
the quark-production contributions are included for the
charged-lepton-plus-jets reaction p p or p bar{p} --> t bar{t} --> (W^+ b)(W^-
bar{b}) --> (l^{+} nu b)(W^- bar{b}). There is a simple 4-angle beam-referenced
spin-correlation function for determination of the relative sign of, or for
measurement of a possible non-trivial phase between the two dominant helicity
amplitudes for t --> W^{+} b decay. There is an analogous function and tests
for bar{t} --> W^{-} bar{b} decay. This signature requires use of the (t
bar{t}) c.m.-energy of the hadronically decaying W-boson, or the kinematically
equivalent cosine of the polar-angle of W-boson emission in the anti-top (top)
decay frame. Spinors and their outer-products are constructed so that the
helicity-amplitude phase convention of Jacob & Wick can be used throughout for
the fixing of the signs associated with this large W-boson
longitudinal-transverse interference effect.Comment: Continuation of hep-ph/0506240 to include gluon-production
contribution; 3 "postscript" figures. Equation numbers as in
published-on-line EPJ
On the Spontaneous CP Breaking in the Higgs Sector of the Minimal Supersymmetric Standard Model
We revise a recently proposed mechanism for spontaneous CP breaking at finite
temperature in the Higgs sector of the Minimal Supersymmetric Standard Model,
based on the contribution of squarks, charginos and neutralinos to the one-loop
effective potential. We have included plasma effects for all bosons and added
the contribution of neutral scalar and charged Higgses. While the former have
little effect, the latter provides very strong extra constraints on the
parameter space and change drastically the previous results. We find that CP
can be spontaneously broken at the critical temperature of the electroweak
phase transition without any fine-tuning in the parameter space.Comment: 9 pages, LATEX, 3 appended postscript figures, IEM-FT-76/9
Fluctuations and Intrinsic Pinning in Layered Superconductors
A flux liquid can condense into a smectic crystal in a pure layered
superconductors with the magnetic field oriented nearly parallel to the layers.
If the smectic order is commensurate with the layering, this crystal is {\sl
stable} to point disorder. By tilting and adjusting the magnitude of the
applied field, both incommensurate and tilted smectic and crystalline phases
are found. We discuss transport near the second order smectic freezing
transition, and show that permeation modes lead to a small non--zero
resistivity and large but finite tilt modulus in the smectic crystal.Comment: 4 pages + 1 style file + 1 figure (as uufile) appended, REVTEX 3.
Mechanism of Fluoride Uptake by Hydroxyapatite from Acidic Fluoride Solutions: I. Theoretical Considerations
A mathematical model for the mechanism of calcium fluoride formation on hydroxyapatite in buffered fluoride solutions is proposed. It takes into account the physical and chemical processes that occur during the reaction. With the model it is possible to evaluate a priori the fluoride uptake potential of fluoride solutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67263/2/10.1177_00220345700490066601.pd
Properties of the Bose glass phase in irradiated superconductors near the matching field
Structural and transport properties of interacting localized flux lines in
the Bose glass phase of irradiated superconductors are studied by means of
Monte Carlo simulations near the matching field B_Phi, where the densities of
vortices and columnar defects are equal. For a completely random columnar pin
distribution in the xy-plane transverse to the magnetic field, our results show
that the repulsive vortex interactions destroy the Mott insulator phase which
was predicted to occur at B = B_Phi. On the other hand, for ratios of the
penetration depth to average defect distance lambda/d <= 1, characteristic
remnants of the Mott insulator singularities remain visible in experimentally
accessible quantities as the magnetization, the bulk modulus, and the
magnetization relaxation, when B is varied near B_Phi. For spatially more
regular disorder, e.g., a nearly triangular defect distribution, we find that
the Mott insulator phase can survive up to considerably large interaction range
\lambda/d, and may thus be observable in experiments.Comment: RevTex, 17 pages, eps files for 12 figures include
CP--odd Correlation in the Decay of Neutral Higgs Boson into , , or
We investigate the possibility of detecting CP--odd angular correlations in
the various decay modes of the neutral Higgs boson including the modes of a
pair, a pair, or a heavy quark pair. It is a natural way to probe
the CP character of the Higgs boson once it is identified. Final state
interactions (i.e. the absorptive decay amplitude) is not required in such
correlations. As an illustrative example we take the fundamental source of the
CP nonconservation to be in the Yukawa couplings of the Higgs boson to the
heavy fermions. A similar correlation in the process is
also proposed. Our analysis of these correlations will be useful for
experiments in future colliders such as LEP II, SSC, LHC or NLC.Comment: 16 pages, plus 8 postscript graphs not posted befor
D-term Inflation in Superstring Theories
An inflationary stage dominated by a -term avoids the slow-roll problem of
inflation in supergravity and may emerge in theories with a non-anomalous or
anomalous U(1) gauge symmetry. The most intriguing and commonly invoked
possibility is that the Fayet-Iliopoulos -term triggering inflation is the
one emerging in superstring theories. We discuss the complications one has to
face when trying to build up a successful -term inflationary scenario in
superstring models. In particular, we show that the ``vacuum shifting''
phenomenon of string theories is usually very efficient even in the early
Universe, thus preventing inflation from taking place. On the other hand, when
-term inflation is free to occur, the presence of a plethora of fields and
several non-anomalous additional abelian symmetries in string theories may help
in reconciling the value of the Fayet-Iliopoulos -term required by the COBE
normalization with the value predicted by string theories. We also show that in
superstring -term inflation gravitinos are likely to pose no cosmological
problem.Comment: 19 pages, LaTeX fil
On the phase transition in the scalar theory
The basic tool for the study of the electroweak phase transition is , the one-loop finite-temperature effective potential, improved by
all-loop resummations of the most important infrared contributions. In this
paper we perform, as a first step towards a full analysis of the Standard Model
case, a detailed study of the effective potential of the scalar theory. We show
that subleading corrections to the self-energies lead to spurious terms, linear
in the field-dependent mass , in the daisy-improved effective
potential. Consistency at subleading order requires the introduction of
superdaisy diagrams, which prevent the appearance of linear terms. The
resulting for the scalar theory hints at a phase transition
which is either second-order or very weakly first-order.Comment: 10 A4 pages, table and figures not included and available (by
ordinary mail) upon request, plain LATEX, CERN-TH.6451/92, IEM-FT-56/9
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Measurement of process-induced strains in composite materials using embedded fiber optic sensors
This paper presents the results of experiments to measure the internal strains and temperatures that are generated in graphite/epoxy composite specimens during processing using embedded fiber optic strain sensors and thermocouples. Measurements of strain and temperature, combined with a computational model, offer the potential for non-destructive, real-time determination of residual stress in composites, and may be useful for process monitoring and control. Extrinsic Fabry-Perot interferometer, Bragg grating strain sensors, and thermocouples were embedded in graphite/epoxy composite laminates prior to cure. The specimens were cured in a press, and the internal strains and temperatures developed during processing were monitored and recorded. The results are compared with expected values, and limitations of the experimental technique are discussed
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