Rapidity resummation for BB-meson wave functions

Transverse-momentum dependent (TMD) hadronic wave functions develop light-cone divergences under QCD corrections, which are commonly regularized by the rapidity $\zeta$ 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 $B$-meson wave functions which are the key ingredients of TMD factorization formulae for radiative-leptonic, semi-leptonic and non-leptonic $B$-meson decays. The crucial observation is that rapidity resummation induces a strong suppression of $B$-meson wave functions at small light-quark momentum, strengthening the applicability of TMD factorization in exclusive $B$-meson decays. The phenomenological consequence of rapidity-resummation improved $B$-meson wave functions is further discussed in the context of $B \to \pi$ 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

QCD corrections to B→πB \to \pi form factors from light-cone sum rules

We compute perturbative corrections to $B \to \pi$ form factors from QCD light-cone sum rules with $B$-meson distribution amplitudes. Applying the method of regions we demonstrate factorization of the vacuum-to-$B$-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 $f_{B \pi}^{+}(q^2)$ and $f_{B \pi}^{0}(q^2)$ 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 $B \to \pi$ form factors, paying attention to various sources of perturbative and systematic uncertainties, and extract $|V_{ub}|= \left(3.05^{+0.54}_{-0.38} |_{\rm th.} \pm 0.09 |_{\rm exp.}\right) \times 10^{-3}$ with the inverse moment of the $B$-meson distribution amplitude $\phi_B^{+}(\omega)$ determined by reproducing $f_{B \pi}^{+}(q^2=0)$ obtained from the light-cone sum rules with $\pi$ distribution amplitudes. Furthermore, we present the invariant-mass distributions of the lepton pair for $B \to \pi \ell \nu_{\ell}$ ($\ell= \mu \,, \tau$) in the whole kinematic region. Finally, we discuss non-valence Fock state contributions to the $B \to \pi$ form factors $f_{B \pi}^{+}(q^2)$ and $f_{B \pi}^{0}(q^2)$ in brief.Comment: 44 pages, 12 figure

Substitutability between Equity REITs and Mortgage REITs

This study extends Seck’s (1996) approach to investigate the degree of substitutability between equity real estate investment trusts (EREITs) and mortgage real estate investment trusts (MREITs). The variance ratio test and the variance decomposition of forecast errors yield results indicating the existence of informational commonality between EREITs and MREITs. The findings indicate that the two types of REITs are substitutable. A direct implication is that investors who believe they have superior forecasting ability will be indifferent to invest in either type of REIT. Another implication is that REITs can be treated as a single asset class in constructing a diversified multi-asset portfolio.