Shape and soft functions of HQET and SCET in the 't Hooft Model

The main application of Heavy Quark Effective Theory (HQET) and of Soft Collinear Effective Theory (SCET) is in establishing factorization theorems for exclusive and semi-inclusive decays of heavy mesons. However, the calculation of the soft factors from the HQET or SCET factorization relations is, as usual, impeded by the non-perturbative aspect of the strong interactions. In the hope of gaining some insights into some of these quantities we compute them in the 't Hooft model. We find that the B-meson shape function is exactly given by the square of the B-meson light-cone wave-function. The structure of the B-pi structure function is more complicated: it is given by the product of wave-functions or by a resonant sum depending on the kinematics. The result simplifies dramatically in the chiral limit, where it can be compared with general arguments based on Heavy Meson-Chiral Perturbation theory. No attempt is made to use these results for applications to phenomenology.Comment: 17 pages, 5 figure

Strong Electroweak Symmetry Breaking

Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor, that technivector mesons are light, narrow and decay readily into electroweak vector mesons and photons. While walking technicolor is popular among practitioners, alternatives exist and the Straw Man may not lead to their discovery.Comment: Talk given at the XXIInd Rencontres de Blois, Loire, France, 16-20 July 201

Exact Heavy To Light Meson Form Factors In The Chiral Limit Of Planar 1+1 QCD

The form factors of the flavor changing vector current between a $\bar q Q$-meson and the lightest $\bar q q$ (pseudoscalar-)meson are computed exactly and explicitly in the 't~Hooft model (planar QCD in $1+1$ dimensions) in the limit that the mass of $q$-quark vanishes.Comment: 8p (uuencoded, includes 4 eps figs, LaTeX & epsf), SMU-HEP/94-11 and UCSD/PTH 94-0

Lectures on Flavor Physics and CP Violation

Two short introductory lectures on Flavor Physics delivered at CLASHEP 2015. Among included topics: The KM matrix and the KM model of CP-violation, Determination of KM Elements, FCNC and GIM, New Physics and Flavor, Neutral Meson Mixing and CP Asymmetries. Many problems for the student, and solutions to selected problems, included.Comment: Presented at the 2015 CERN-Latin-American School of High-Energy Physics, Ibarra, Ecuador, 5 - 17 March 2015. arXiv admin note: substantial text overlap with arXiv:1501.0528

Factorization in B -> K pi e+e- decays

We derive factorization relations for the transverse helicity amplitudes in the rare decays B-> K\pi l+l- at leading order in Lambda/m_b, in the kinematical region with an energetic kaon and a soft pion. We identify and compute a new contribution of leading order in Lambda/m_b to the B->K\pi l+l- amplitude, which is not present in the one-body decay B-> K*l+l-. As an application we study the forward-backward asymmetry (FBA) of the lepton momentum angular distribution in B-> K\pi l+l- decays away from the K* resonance. The FBA in these decays has a zero at q0^2 = q0^2(M_{Kpi}), which can be used, in principle, for determining the Wilson coefficients C_{7,9} and testing the Standard Model. We point out that the slope of the q0^2(M_{Kpi}^2) curve contains the same information about the Wilson coefficients as the location of the zero, but is less sensitive to unknown nonperturbative dynamics. We estimate the location of the zero at leading order in factorization, and using a resonant model for the B -> K\pi l+l- nonfactorizable amplitude.Comment: 16 pages, 5 figures. Version to appear in Physical Review D. One new observable introduced and considered - the slope of the zero of the forward-backward asymmetry as function of the K\pi invariant mas