22,314 research outputs found
Non-dipolar gauge links for transverse-momentum-dependent pion wave functions
I discuss the factorization-compatible definitions of
transverse-momentum-dependent (TMD) pion wave functions which are fundamental
theory inputs entering QCD factorization formulae for many hard exclusive
processes. I will first demonstrate that the soft subtraction factor introduced
to remove both rapidity and pinch singularities can be greatly reduced by
making the maximal use of the freedom to construct the Wilson-line paths when
defining the TMD wave functions. I will then turn to show that the newly
proposed TMD definition with non-dipolar Wilson lines is equivalent to the one
with dipolar gauge links and with a complicated soft function, to all orders of
the perturbative expansion in the strong coupling, as far as the infrared
behavior is concerned.Comment: 7 pages, 3 figure
Factorization, resummation and sum rules for heavy-to-light form factors
Precision calculations of heavy-to-light form factors are essential to
sharpen our understanding towards the strong interaction dynamics of the
heavy-quark system and to shed light on a coherent solution of flavor
anomalies. We briefly review factorization properties of heavy-to-light form
factors in the framework of QCD factorization in the heavy quark limit and
discuss the recent progress on the QCD calculation of form factors
from the light-cone sum rules with the -meson distribution amplitudes.
Demonstration of QCD factorization for the vacuum-to--meson correlation
function used in the sum-rule construction and resummation of large logarithms
in the short-distance functions entering the factorization theorem are
presented in detail. Phenomenological implications of the newly derived sum
rules for form factors are further addressed with a particular
attention to the extraction of the CKM matrix element .Comment: 6 pages, 3 figures, proceedings prepared for the "QCD@work 2016",
(27-30 June 2016, Martina Franca, Italy
Rapidity resummation for -meson wave functions
Transverse-momentum dependent (TMD) hadronic wave functions develop
light-cone divergences under QCD corrections, which are commonly regularized by
the rapidity of gauge vector defining the non-light-like Wilson lines.
The yielding rapidity logarithms from infrared enhancement need to be resummed
for both hadronic wave functions and short-distance functions, to achieve
scheme-independent calculations of physical quantities. We briefly review the
recent progress on the rapidity resummation for -meson wave functions which
are the key ingredients of TMD factorization formulae for radiative-leptonic,
semi-leptonic and non-leptonic -meson decays. The crucial observation is
that rapidity resummation induces a strong suppression of -meson wave
functions at small light-quark momentum, strengthening the applicability of TMD
factorization in exclusive -meson decays. The phenomenological consequence
of rapidity-resummation improved -meson wave functions is further discussed
in the context of transition form factors at large hadronic recoil.Comment: 6 pages, 2 figures, Conference proceedings for the workshop of
QCD@work, Giovinazzo (Italy), June 16-19, 201
Lepton flavor violating processes in unparticle physics
We study the virtual effects of unparticle physics in the lepton flavor
violating processes and scattering, where
denotes the pseudoscalar mesons: and
denote two different lepton flavors. For the decay of , there
is no constraint from the current experimental upper bounds on the vector
unparticle coupling with leptons. The constraint on the coupling constant
between scalar unparticle field and leptons is sensitive to the scaling
dimension of the unparticle . For the scattering process , there is only constraint from experiments on the vector unparticle
couplings with leptons but no constraint on the scalar unparticle. We study the
dependence of the cross section of with different values of
. If , the cross section is independent on the
center mass energy. For , the cross section increases with
.Comment: 8 pages, revtex4,with 2 figures, to appear in Phys. Rev.
QCD corrections to form factors from light-cone sum rules
We compute perturbative corrections to form factors from QCD
light-cone sum rules with -meson distribution amplitudes. Applying the
method of regions we demonstrate factorization of the vacuum-to--meson
correlation function defined with an interpolating current for pion, at
one-loop level, explicitly in the heavy quark limit. The short-distance
functions in the factorization formulae of the correlation function involves
both hard and hard-collinear scales; and these functions can be further
factorized into hard coefficients by integrating out the hard fluctuations and
jet functions encoding the hard-collinear information. Resummation of large
logarithms in the short-distance functions is then achieved via the standard
renormalization-group approach. We further show that structures of the
factorization formulae for and at
large hadronic recoil from QCD light-cone sum rules match that derived in QCD
factorization. In particular, we perform an exploratory phenomenological
analysis of form factors, paying attention to various sources of
perturbative and systematic uncertainties, and extract with the inverse moment of the -meson distribution amplitude
determined by reproducing obtained
from the light-cone sum rules with distribution amplitudes. Furthermore,
we present the invariant-mass distributions of the lepton pair for () in the whole kinematic region. Finally,
we discuss non-valence Fock state contributions to the form factors
and in brief.Comment: 44 pages, 12 figure
- …