Light-Cone Sum Rules for the Form Factors of the NγΔN\gamma\Delta transition at Q^2=0

The radiative $\Delta \to \gamma N$ transition is examined at the real photon point $Q^2=0$ using the framework of light-cone QCD sum rules. In particular, we determine the sum rules for the transition form factors $G_M(0)$ and $R_{EM}$ up to twist 4.Comment: Talk given at the Workshop on Exclusive Reactions at High Momentum Transfer 200

Bˉ→Xsγ\bar B\to X_s \gamma with a warped bulk Higgs

We study the decay $\bar B\to X_s\gamma$ in Randall-Sundrum models with an IR-localised bulk Higgs. The two models under consideration are a minimal model as well as a model with a custodial protection mechanism. We include the effects of tree- and one-loop diagrams involving 5D gluon and Higgs exchanges as well as QCD corrections arising from the evolution from the Kaluza-Klein scale to the typical scale of the decay. We find the RS corrections to the branching fraction can be sizeable for large Yukawas and moderate KK scales $T$; for small Yukawas the RS contribution is small enough to be invisible in current experimental data.Comment: 20 pages, 5 figures(V2: references added, matches version published in Nuclear Physics B

Lepton flavour violation in RS models with a brane- or nearly brane-localized Higgs

We perform a comprehensive study of charged lepton flavour violation in Randall-Sundrum (RS) models in a fully 5D quantum-field-theoretical framework. We consider the RS model with minimal field content and a "custodially protected" extension as well as three implementations of the IR-brane localized Higgs field, including the non-decoupling effect of the Kaluza-Klein (KK) excitations of a narrow bulk Higgs. Our calculation provides the first complete result for the flavour-violating electromagnetic dipole operator in Randall-Sundrum models. It contains three contributions with different dependence on the magnitude of the anarchic 5D Yukawa matrix, which can all be important in certain parameter regions. We study the typical range for the branching fractions of mu -> e gamma, mu -> 3e, mu N -> e N as well as tau -> mu gamma, tau -> 3 mu and the electron electric dipole moment by a numerical scan in both the minimal and the custodial RS model. The combination of mu -> e gamma and mu N -> e N currently provides the most stringent constraint on the parameter space of the model. A typical lower limit on the KK scale T is around 2 TeV in the minimal model (up to 4 TeV in the bulk Higgs case with large Yukawa couplings), and around 4 TeV in the custodially protected model, which corresponds to a mass of about 10 TeV for the first KK excitations, far beyond the lower limit from the non-observation of direct production at the LHC.Comment: 64 pages, 21 figures, LaTeX, v2: electron EDM analysis added, matches published versio

B meson distribution amplitude from B --> \gamma l \nu

We reconsider the utility of the radiative decay $B \to \gamma \ell \nu$ with an energetic photon in the final state for determining parameters of the $B$-meson light-cone distribution amplitude. Including $1/m_b$ power corrections and radiative corrections at next-to-leading logarithmic order, we perform an improved analysis of the existing BABAR data. We find a provisional lower limit on the inverse moment of the $B$ meson distribution amplitude, $\lambda_B$, which, due to the inclusion of radiative and power corrections, is significantly lower than the previous result. More data with large photon energy is, however, required to obtain reliable results, as should become available in the future from SuperB factories.Comment: 15 pages, 5 figure

Light-cone sum rules for the NγΔN\gamma\Delta transitions for real photons

We examine the radiative $\Delta \to \gamma N$ transition at the real photon point $Q^2=0$ using the framework of light-cone QCD sum rules. In particular, the sum rules for the transition form factors $G_M(0)$ and $R_{EM}$ are determined up to twist 4. The result for $G_M(0)$ agrees with experiment within 10% accuracy. The agreement for $R_{EM}$ is also reasonable. In addition, we derive new light-cone sum rules for the magnetic moments of nucleons, with a complete account of twist-4 corrections based on a recent reanalysis of photon distribution amplitudes.Comment: 34 pages, 9 figures, revised version, published in Phys. Rev. D, one misplaced reference correcte

Phenomenology of the Heavy Flavored spin 3/2 Baryons in Light Cone QCD

Motivated by the results of the recent experimental discoveries for charm and bottom baryons, the masses and magnetic moments of the heavy baryons with $J^P=3/2^+$ containing a single heavy quark are studied within light cone QCD sum rules method. Our results on the masses of heavy baryons are in good agreement with predictions of other approaches, as well as with the existing experimental data.Comment: 12 Pages, 18 Figures and 3 Tables. Based on: arXiv:0807.3481v2 [hep-ph](Nucl.Phys.B808:137-154,2009). To be Published in the Proceeding of the International Conference on New Trends in High Energy Physics, 27 Sept.-4 Oct. 2008, Yalta, Crimea, Ukrain

Hadronic light-by-light scattering contribution to the muon g-2

We review recent developments concerning the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. We first discuss why fully off-shell hadronic form factors should be used for the evaluation of this contribution to the g-2. We then reevaluate the numerically dominant pion-exchange contribution in the framework of large-N_C QCD, using an off-shell pion-photon-photon form factor which fulfills all QCD short-distance constraints, in particular, a new short-distance constraint on the off-shell form factor at the external vertex in g-2, which relates the form factor to the quark condensate magnetic susceptibility in QCD. Combined with available evaluations of the other contributions to hadronic light-by-light scattering this leads to the new result a_{\mu}(LbyL; had) = (116 \pm 40) x 10^{-11}, with a conservative error estimate in view of the many still unsolved problems. Some potential ways for further improvements are briefly discussed as well. For the electron we obtain the new estimate a_{e}(LbyL; had) = (3.9 \pm 1.3) x 10^{-14}.Comment: 6 pages, 1 figure, to be published in the proceedings of the PhiPsi09 workshop, Oct. 13-16, 2009, Beijing, Chin

Chirality violating condensates in QCD and their connection with zero mode solutions of quark Dirac equations

It is demonstrated, that chirality violating condensates in massless QCD arise entirely from zero mode solutions of Dirac equations in arbitrary gluon fields. The model is suggested, where the zero mode solutions are the ones for quarks, moving in the instanton field. Basing on this model were calculated the quark condensate magnetic susceptibilities of dimensions $3(\chi)$ and 5 ($\kappa$ and $\xi$). The good considence of the values $\chi,\kappa$ and $\xi$, obtained in this approach with ones, found from the hadronic spectrum ia a serious argument in favour, that instantons are the only source of chirality violating condensates in QCD. The temperature dependence of the quark condensate is discussed. It is shown that the phase transition, corresponding to the $T$-dependence of the quark condensate $\alpha(T)$ as an order parameter, is of the type of crossover.Comment: The talk presented of Gribov-80 Workshop, May 28-30, 2010, Trieste, 8 pages, minor change