182 research outputs found
Chiral sum rules to second order in quark mass
A new calculation of the isospin and hypercharge axialvector current
propagators ( and ) to
two loops in SU(3) x SU(3) chiral perturbation theory is used to derive chiral
spectral function sum rules valid to second order in the light quark masses.
Explicit forms are given for the three-pion isospin axialvector spectral
functions at low energy and application of the sum rules to the determination
of counterterms of the chiral lagrangian is discussed.Comment: Figures extended down to threshold; Eq. (19) expressed in simplified
for
Two-point function of strangeness-carrying vector-currents in two-loop Chiral Perturbation Theory
We calculate the correlator between two external vector-currents having the
quantum-numbers of a charged kaon. We give the renormalized expression to two
loops in standard chiral perturbation theory in the isospin limit, which, as a
physical result, is finite and scale-independent. Applications include a low
energy theorem, valid at two loop order, of a flavor breaking combination of
vector current correlators as well as a determination of the phenomenologically
relevant finite -counterterm combination by means of inverse
moment finite energy sum rules. This determination is less sensitive to
isospin-breaking effects than previous attempts.Comment: 24 pages, revtex, 4 figures, 2 tables, revised version, one ref.
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Enhanced spin orbit interaction of light in highly confining optical fibers for mode division multiplexing
Light carries both orbital angular momentum (OAM) and spin angular momentum (SAM), related to wavefront rotation and polarization, respectively. These are usually approximately independent quantities, but they become coupled by light's spin-orbit interaction (SOI) in certain exotic geometries and at the nanoscale. Here we reveal a manifestation of strong SOI in fibers engineered at the micro-scale and supporting the only known example of propagating light modes with non-integer mean OAM. This enables propagation of a record number (24) of states in a single optical fiber with low cross-talk (purity > 93%), even as tens-of-meters long fibers are bent, twisted or otherwise handled, as fibers are practically deployed. In addition to enabling the investigation of novel SOI effects, these light states represent the first ensemble with which mode count can be potentially arbitrarily scaled to satisfy the exponentially growing demands of high-performance data centers and supercomputers, or telecommunications network nodes
Relating B_s Mixing and B_s -> mu+mu- with New Physics
We perform a study of the Standard Model (SM) fit to the mixing quantities
, and in order to bound
contributions of New Physics to mixing. We then use this to explore the
branching fraction of in certain models of New Physics
(NP). In most cases, this constrains NP amplitudes for
to lie below the SM component.Comment: 27 pages, 5 figures; corrected misprints, updated numerical inputs
and new reference
Partial Derivation of Transformation Properties of Quarks and Leptons
Under the assumptions that with
simple is a local symmetry group at high energies, that color is
parity-conserving, and the Y-charges are irreducible, we show that anomaly
constraints imply the minimal set of fermions is fifteen in number. Given this
minimal set, we further show that must be and the unbroken
gauge symmetry is {\it either} color {\it or} the product of color with
electric charge.Comment: 9 pages, UMDHEP 94-72 and IFP-487-UN
Corrections to Sirlin's Theorem in Chiral Perturbation Theory
We present the results of the first two-loop calculation of a form factor in
full Chiral Perturbation Theory. We choose a specific
linear combination of and form factors (the one
appearing in Sirlin's theorem) which does not get contributions from order
operators with unknown constants. For the charge radii, the correction to
the previous one-loop result turns out to be significant, but still there is no
agreement with the present data due to large experimental uncertainties in the
kaon charge radii.Comment: 6 pages, Latex, 2 LaTeX figure
Two-Point Functions and S-Parameter in QCD-like Theories
We calculated the vector, axial-vector, scalar and pseudo-scalar two-point
functions up to two-loop level in the low-energy effective field theory for
three different QCD-like theories. In addition we also calculated the
pseudo-scalar decay constant . The QCD-like theories we used are those
with fermions in a complex, real or pseudo-real representation with in general
n flavours. These case correspond to global symmetry breaking pattern of
, or .
We also estimated the S parameter for those different theories.Comment: 29 page
The Extraction of Light Quark Masses From Sum Rule Analyses of Axial and Vector Current Ward Identities
We re-examine the use of sum rules in the extraction of light quark masses
and discuss a number of potential problems with existing analyses. The most
important issue is that of the overall normalization of the hadronic spectral
functions should not be fixed by assuming complete resonance dominance of the
continuum threshold region as it can overestimate the resonance contributions
to spectral integrals by factors as large as . The second important
uncertainty comes from the assumed location, , of the onset of duality
with perturbative QCD, as the extracted quark masses depend very sensitively on
this parameter. The assumption of duality and the requirement of positivity of
imposes very severe constraints on the shape of the relevant
spectral function in the dual region, and leads to rigorous lower bounds for
as a function of . In the extractions of we find that the
conventional choice of the value of is not physical. For a more
reasonable choice of we are not able to find a solution that is stable
with respect to variations of the Borel transform parameter. This problem can
be overcome only if the hadronic spectral function is determined up to
significantly larger values of than is currently possible. Finally, we also
estimate the error associated with the convergence of perturbative QCD
expressions used in the sum rule analyses. Our conclusion is that, taking all
of these issues into account, the resulting sum rule estimates for both
and could easily have uncertainties as large as a factor of 2.Comment: 28 pages. Published version. Modified "axis" source for figures also
include
Double Penguins and the Contribution of Vector Meson--like States to the Decays
Using perturbative QCD, the contribution at the leading twist, leading
level, of charm and up quark loops to the decays and is presented. In the case of , the relative importance of these contributions depend
upon the unknown CKM matrix elements and .
Assuming that the ratio is bounded
between as is suggested by the Particle Data Group, the
error in extracting by these decays is estimated.Comment: 4 double column pages, revtex, 3 figures attached, 2 figures added
indicating less optimism concerning the accuracy at which
can be extracted: to appear in PR
Examination of the Resonance Contributions to Dileptonic Rare B-Decays
We analyse the long-distance contribution to
differential decay rate when the momentum dependence of and
- conversion strength is taken into account. The results
indicate that the resonance to nonresonance interference in the dilepton
invariant mass distribution is substantially reduced.Comment: 10 pages, Latex, one figure (included
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