Hierarchical chiral symmetry breaking and quark mass matrices revisited

We demonstrate how the assumption of hierarchical chiral symmetry breaking can be systematically used to create phenomenologically satisfactory mass matrices. In place of postulating a particular set of mass matrices at the outset, we emphasize that once a particular basis for the first stage of chiral symmetry breaking is selected, the following steps are determined by the known information on quark masses and mixings. We illustrate this procedure for the basis originally chosen by Fritzsch and find a modified set of quark mass matrices, corresponding to equal final-stage nondiagonal radiative contributions, which fits the data much better in the minimal Higgs framework, providedm _t ?88 GeV and the mixing ratio |V _ub |/|V _cb |?0.15.     

Union of chiral and heavy quark symmetries

We describe the chiral symmetric couplings of pions to heavy mesons (B or D), valid in the portion of phase space where the pions have low momentum. In order to include consistently all low energy excitations, the vector mesons (B^* or D^*) must appear explicitly in the effective lagrangian. The result is then invariant under both the chiral and heavy quark symmetries. We include matrix elements relevant for various weak decays.     

Effective meson lagrangian with chiral and heavy quark symmetries from quark flavor dynamics

By bosonization of an extended NJL model we derive an effective meson theory which describes the interplay between chiral symmetry and heavy quark dynamics. This effective theory is worked out in the low-energy regime using the gradient expansion. The resulting effective lagrangian describes strong and weak interactions of heavy B and D mesons with pseudoscalar Goldstone bosons and light vector and axial-vector mesons. Heavy meson weak decay constants, coupling constants and the Isgur-Wise function are predicted in terms of the model parameters partially fixed from the light quark sector. Explicit SU(3)_F symmetry breaking effects are estimated and, if possible, confronted with experiment.     

Predictive flavor symmetries of the neutrino mass matrix

Here we propose an A(4) flavor symmetry model that implies a lower bound on the neutrinoless double beta decay rate, corresponding to an effective mass parameter M{ee} > or similar to 0.03 eV, and a direct correlation between the expected magnitude of CP violation in neutrino oscillations and the value of sin{2}theta{13}, as well as a nearly maximal CP phase delta.     

Can the quark mass matrix be real?

We study the possibility of solving the strong CP problem in a theory where CP is broken spontaneously and the quark mass matrix, M_ij, not just its determinant, remains real to one part in 10⁸. We find that it is difficult to build natural models consistent with the known CP violation phenomenology. We find that such models require new fermions and possess a hierarchy problem. We present an SO(10) example which succeeds at the one-loop level, however, two-loop effects will introduce phases into M_ij.     

Charm diffusion in a pion gas implementing unitarity, chiral and heavy quark symmetries

We compute the charm drag and diffusion coefficients in a hot pion gas, such as is formed in a heavy ion collision after the system cools sufficiently to transit into the hadron phase. We fully exploit heavy quark effective theory (with both D and D^∗ mesons as elementary degrees of freedom during the collision) and chiral perturbation theory, and employ standard unitarization to reach higher temperatures. We find that a certain friction and shear diffusion coefficients are almost p²-independent at a fixed temperature which simplifies phenomenological analysis.At the higher end of reliability of our calculation, , we report a charm relaxation length , in agreement with the model estimate of He, Fries and Rapp.The momentum of a 1 GeV charm quark decreases about 50 MeV per fermi when crossing the hadron phase.     

Pion mass dependence of the nucleon mass in the chiral quark soliton model

The dependence of the nucleon mass on the mass of the pion is studied in the framework of the chiral quark-soliton model. A remarkable agreement is observed with lattice data from recent full dynamical simulations. The possibility and limitations to use the results from the chiral quark soliton model as a guideline for the chiral extrapolation of lattice data are discussed.     

Nailing Down the KM matrix and the top quark mass

We present a determination of the KM matrix elements and a prediction of the top quark mass, based on available experimental information and the only theoretical framework, known to us, that is free of experimental and/or theoretical difficulties.     

Top-quark-mass enhancement in a seesaw-type quark mass matrix

We investigate the implications of a seesawtype mass matrix, i.e.,M _f?m _LM _F ^?1 m _R, for quarks and leptonsf under the assumption that the matricesm _L andm _R are common to all flavors (up-/down- and quark-/lepton-sectors) and the matricesM _F characterizing the heavy fermion sectors have the form [(unit matrix)+b _f (a democratic matrix)] whereb _f is a flavor parameter. We find that by adjusting the complex parameterb _f, the model can provide thatm _t?m _b while at the same time keepingm _u～m _d without assuming any parameter with hierarchically different values betweenM _U andM _D. The model with three adjustable parameters under the “maximal” top-quark-mass enhancement can give reasonable values of five quark-mass ratios and four KM matrix parameters.     

Top-quark-mass enhancement in a seesaw-type quark mass matrix

We investigate the implications of a seesawtype mass matrix, i.e.,M _f?m _LM _F ^?1 m _R, for quarks and leptonsf under the assumption that the matricesm _L andm _R are common to all flavors (up-/down- and quark-/lepton-sectors) and the matricesM _F characterizing the heavy fermion sectors have the form [(unit matrix)+b _f (a democratic matrix)] whereb _f is a flavor parameter. We find that by adjusting the complex parameterb _f, the model can provide thatm _t?m _b while at the same time keepingm _u??m _d without assuming any parameter with hierarchically different values betweenM _U andM _D. The model with three adjustable parameters under the ??maximal?? top-quark-mass enhancement can give reasonable values of five quark-mass ratios and four KM matrix parameters.     

The Fritzsch mass matrix and geometrical scaling of quark masses

It is shown by numerical calculation that the best fit of the Fritzsch matrix to present data is found for values of the top-quark mass between 30 and 60 GeV, depending on the value adopted for the strange-quark mass. The value of m_t that produces the best fit is very close to the geometrical scaling prediction of m_t = m_b(m_c/m_s) for current-quark masses. The residuals of the fit obey a surprising scaling rule, being functions of m_sm_t rather than of m_s and m_t separately.