1,425 research outputs found
Possible duality violations in tau decay and their impact on the determination of alpha_s
We discuss the issue of duality violations in hadronic tau decay. After
introducing a physically motivated ansatz for duality violations, we estimate
their possible size by fitting this ansatz to the tau experimental data
provided by the ALEPH collaboration. Our conclusion is that these data do not
exclude significant duality violations in tau decay. This may imply an
additional systematic error in the value of alpha_s(m_tau), extracted from tau
decay, as large as \delta alpha_s(m_tau) \sim 0.003-0.010 .Comment: 20 pages, 4 figures. Minor fixes in the Appendi
String Loop Threshold Corrections for N=1 Generalized Coxeter Orbifolds
We discuss the calculation of threshold corrections to gauge coupling
constants for the, only, non-decomposable class of abelian (2, 2) symmetric N=1
four dimensional heterotic orbifold models, where the internal twist is
realized as a generalized Coxeter automorphism. The latter orbifold was singled
out in earlier work as the only N=1 heterotic orbifold that satisfy the
phenomenological criteria of correct minimal gauge coupling unification and
cancellation of target space modular anomalies.Comment: 10 pages, LaTe
The boundary state for a class of analytic solutions in open string field theory
We construct a boundary state for a class of analytic solutions in the
Witten's open string field theory. The result is consistent with the property
of the zero limit of a propagator's length, which was claimed in [19]. And we
show that our boundary state becomes expected one for the perturbative vacuum
solution and the tachyon vacuum solution. We also comment on possible presence
of multi-brane solutions and ghost brane solutions from our boundary state.Comment: 19 pages, 2 figure
Taming boundary condition changing operator anomalies with the tachyon vacuum
Motivated by the appearance of associativity anomalies in the context of superstring field theory, we give a generalized solution built from boundary condition changing operators which can be associated to a generic tachyon vacuum in the KBc subalgebra of the Okawa form. We articulate sufficient conditions on the choice of tachyon vacuum to ensure that ambiguous products do not appear in the equations of motion
On Gauge Equivalence of Tachyon Solutions in Cubic Neveu-Schwarz String Field Theory
Simple analytic solution to cubic Neveu-Schwarz String Field Theory including
the sector is presented. This solution is an analog of the
Erler-Schnabl solution for bosonic case and one of the authors solution for the
pure case. Gauge transformations of the new solution to others known
solutions for the string tachyon condensation are constructed explicitly.
This gauge equivalence manifestly supports the early observed fact that these
solutions have the same value of the action density.Comment: 8 pages, LaTe
The Prediction of Mass of Z'-Boson from Mixing
B_q^0-B_^0 bar mixing offers a profound probe into the effects of new
physics beyond the Standard Model. In this paper, and
mass differences are considered taking the effect of both
Z-and Z' -mediated flavour-changing neutral currents in the
mixing (q = d, s). Our estimated mass of Z' boson is accessible at the
experiments LHC and B-factories in near future.Comment: 11 pages, 02 Figure
Tachyon Vacuum in Cubic Superstring Field Theory
In this paper we give an exact analytic solution for tachyon condensation in
the modified (picture 0) cubic superstring field theory. We prove the absence
of cohomology and, crucially, reproduce the correct value for the D-brane
tension. The solution is surprising for two reasons: First, the existence of a
tachyon vacuum in this theory has not been definitively established in the
level expansion. Second, the solution {\it vanishes} in the GSO sector,
implying a ``tachyon vacuum'' solution exists even for a {\it BPS} D-brane.Comment: 16 pages, 2 figure
Relevant Deformations in Open String Field Theory: a Simple Solution for Lumps
We propose a remarkably simple solution of cubic open string field theory
which describes inhomogeneous tachyon condensation. The solution is in
one-to-one correspondence with the IR fixed point of the RG-flow generated in
the two--dimensional world-sheet theory by integrating a relevant operator with
mild enough OPE on the boundary. It is shown how the closed string overlap
correctly captures the shift in the closed string one point function between
the UV and the IR limits of the flow. Examples of lumps in non-compact and
compact transverse directions are given.Comment: 45 pages. v2: typos and minor improvements. v3: submitted to jhe
The and decays with the fourth generation
If the fourth generation fermions exist, the new quarks could influence the
branching ratios of the decays of and . We
obtain two solutions of the fourth generation CKM factor
from the decay of . We use these
two solutions to calculate the new contributions of the fourth generation quark
to Wilson coefficients of the decay of . The branching ratio
and the forward-backward asymmetry of the decay of in the two
cases are calculated. Our results are quite different from that of SM in one
case, almost same in another case. If Nature chooses the formmer, the meson
decays could provide a possible test of the forth generation existence.Comment: 10 pages, 5 figure
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