1,321 research outputs found
Proposing "b-Parity" - a New Approximate Quantum Number in Inclusive b-jet Production - as an Efficient Probe of New Flavor Physics
We consider the inclusive reaction \ell^+ \ell^- -> nb +X (n = number of
b-jets) in lepton colliders for which we propose a useful approximately
conserved quantum number b_P=(-1)^n that we call b-Parity (b_P). We make the
observation that the Standard Model (SM) is essentially b_P-even since SM
b_P-violating signals are necessarily CKM suppressed. In contrast new flavor
physics can produce b_P=-1 signals whose only significant SM background is due
to b-jet misidentification. Thus, we show that b-jet counting, which relies
primarily on b-tagging, becomes a very simple and sensitive probe of new flavor
physics (i.e., of b_P-violation).Comment: 5 pages using revtex, 2 figures embadded in the text using epsfig. As
will appear in Phys.Rev.Lett.. Considerable improvement was made in the
background calculation as compared to version 1, by including purity
parameters, QCD effects and 4-jets processe
A Configurationally-Resolved-Super-Transition-Arrays method for calculation of the spectral absorption coefficient in hot plasmas
A new method, 'Configurationally-Resolved-Super-Transition-Arrays', for
calculation of the spectral absorption coefficient in hot plasmas is presented.
In the new method, the spectrum of each Super-Transition-Array is evaluated as
the Fourier transform of a single Complex Pseudo Partition Function, which
represents the exact analytical sum of the contributions of all constituting
unresolved transition arrays sharing the same set of one-electron solutions.
Thus, in the new method, the spectrum of each Super-Transition-Array is
resolved down to the level of the (unresolved) transition arrays. It is shown
that the corresponding spectrum, evaluated by the traditional
Super-Transition-Arrays (STA) method [A. Bar Shalom, J. Oreg, W.H. Goldstein,
D. Shvarts and A. Zigler, Phys. Rev. A 40, 3183 (1989)], is just the coarse
grained Gaussian approximation of the
Configurationally-Resolved-Super-Transition-Array. A new computer program is
presented, capable of evaluating the absorption coefficient by both the new
configurationally resolved and the traditional Gaussian Super-Transition-Arrays
methods. A numerical example of gold at temperature 1keV and density 0.5
gr/cm^{3}, is presented, demonstrating the simplicity, efficiency and accuracy
of the new method
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
Production and decay of the neutral top-pion in high energy colliders
We study the production and decay of the neutral top-pion
predicted by topcolor-assisted technicolor(TC2) theory. Our results show that,
except the dominant decay modes , and , the
can also decay into and modes. It can
be significantly produced at high energy collider(LC) experiments
via the processes and . We further calculate the production cross sections of the
processes and . We find that the signatures of the neutral top-pion
can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.
CP Nonconservation in at the Tevatron
The reaction is found to be rather rich in exhibiting
several different types of CP asymmetries. The spin of the top quark plays an
important role. Asymmetries are related to form factors arising from radiative
corrections of the production vertex due to non-standard physics. As
illustrations, effects are studied in two Higgs Doublet Models and in
Supersymmetric Models; asymmetries up to a few percent may be possible.Comment: 14 pages, 3 figures. Note: replaced due to minor problems that
appeared on some postscript previewers. No change in conten
The flavor changing top decay t-->c+sneutrino or sneutrino-->t+c(bar) in the MSSM without R-parity
Widths for the new flavor changing top quark decay t-->c+sneutrino or for the
reversed sneutrino decay sneutrino-->t+c(bar) are calculated in the MSSM
without R-parity conservation. For large \tan\beta, e.g., \tan\beta ~ m_t/m_b ~
40, Br(t-->c+sneutrino) > 10^{-5} or Br(sneutrino-->t+c(bar)) > 10^{-6} in a
relatively wide range of the supersymmetric parameter space as long as there is
more than one non-zero R-parity violating coupling. In the best cases, with a
typical squark mass around 100 GeV, we find that Br(t-->c+sneutrino) ~ 10^{-4}
- 10^{-3} or Br(sneutrino-->t+c(bar)) ~ 10^{-5} - 10^{-4}. For \tan\beta ~ O(1)
the corresponding branching ratios for both top or sneutrino decays are too
small to be measured at the LHC. Therefore, the decays t-->c+sneutrino or
sneutrino-->t+c(bar) appear to be sensitive to \tan\beta and may be detected at
the LHC. The branching ratios of the corresponding decays to an up quark
instead of a charm quark, e.g., t-->u+sneutrino or sneutrino-->t+u(bar), may
also be similar.Comment: 23 pages, plain latex, 8 figures embadded in the text using epsfi
Low-temperature dependence of the thermo-magnetic transport properties of the SrTiO3/LaAlO3 interface
We report transport measurements, including: Hall, Seebeck and Nernst Effect.
All these transport properties exhibit anomalous field and temperature
dependences, with a change of behavior observed at about H 1.5T and T 15K. We
were able to reconcile the low-temperature-low-field behavior of all transport
properties using a simple two band analysis. A more detailed model is required
in order to explain the high magnetic field regime.Comment: 6 pages, 7 figure
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