136 research outputs found
B->pi,K,eta Decay Formfactors from Light-Cone Sum Rules
We present an improved calculation of all B -> light pseudoscalar formfactors
from light-cone sum rules, including one-loop radiative corrections to twist-2
and twist-3 contributions, and leading order twist-4 corrections. The total
theoretical uncertainty of our results at zero momentum transfer is 10 to 13%.
The dependence of the formfactors on the momentum transfer q^2 is parametrized
in a simple way that is consistent with their analytical properties and is
valid for all physical q^2. The uncertainty of the extrapolation in q^2 on the
semileptonic decay rate Gamma(B -> pi e nu) is estimated to be 5%.Comment: 10 pages; talk given at Continuous Advances in QCD 2004, Minneapolis,
May 200
Explicit and spontaneous breaking of SU(3) into its finite subgroups
We investigate the breaking of SU(3) into its subgroups from the viewpoints
of explicit and spontaneous breaking. A one-to-one link between these two
approaches is given by the complex spherical harmonics, which form a complete
set of SU(3)-representation functions. An invariant of degrees p and q in
complex conjugate variables corresponds to a singlet, or vacuum expectation
value, in a (p,q)-representation of SU(3). We review the formalism of the
Molien function, which contains information on primary and secondary
invariants. Generalizations of the Molien function to the tensor generating
functions are discussed. The latter allows all branching rules to be deduced.
We have computed all primary and secondary invariants for all proper finite
subgroups of order smaller than 512, for the entire series of groups
\Delta(3n^2), \Delta(6n^2), and for all crystallographic groups. Examples of
sufficient conditions for breaking into a subgroup are worked out for the
entire T_{n[a]}-, \Delta(3n^2)-, \Delta(6n^2)-series and for all
crystallographic groups \Sigma(X). The corresponding invariants provide an
alternative definition of these groups. A Mathematica package, SUtree, is
provided which allows the extraction of the invariants, Molien and generating
functions, syzygies, VEVs, branching rules, character tables, matrix
(p,q)_{SU(3)}-representations, Kronecker products, etc. for the groups
discussed above.Comment: 62 pages, 5 figures; the corresponding software package SUtree can be
downloaded from http://theophys.kth.se/~amerle/SUtree/SUtree.html New in v2:
Nice figure added, references added, explicit transformation matrices between
different embeddings calculated, software package update
B -> K* gamma vs B -> rho gamma and |V_td/V_ts|
We determine |V_{\rm td}/V_{\rm ts}| = 0.192 \pm 0.016_ exp \pm 0.014_th from
B -> (K^*,rho) gamma as measured by the B-factories Babar and Belle.
This version differs from the original proceedings by the inclusion of the
new BaBar measurement of B -> rho(omega) gamma presented at ICHEP 2006, which
significantly shifts the results for |V_{td}/V_{ts}|.Comment: Proceedings for QAQCD 06, Minneapolis Including new BaBar measurement
B->rho gamma presented at ICHEP 2006, which significantly shifts the result
of |V_td/V_ts
Scaling relations for the entire spectrum in mass-deformed conformal gauge theories
We consider mass-deformed conformal gauge theories (mCGT) and investigate the
scaling behaviour of hadronic observables as a function of the fermion mass.
Applying renormalization group arguments directly to matrix elements, we find
m_H ~ m^{1/(1+gamma*)} and F ~ m^{\eta_F(gamma*)} for the decay constants,
thereby generalizing our results from a previous paper to the entire spectrum.
We derive the scaling law m_H \~m^{1/(1+gamma*)} using the Hellmann-Feynman
theorem, and thus provide a derivation which does not rely on renormalization
group arguments. Using the new results we reiterate, on the phenomenologically
important, S-parameter. Finally, we discuss how spectral representations can be
used to relate the mass and decay constant trajectories.Comment: 11 pages; typos removed, additional comments, version to appear in
PL
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