1,721,022 research outputs found
Precise tests of a quark mass texture
No full textThe relations \V-ub/V-cb\ = (mu/mc)(1/2) and \V-td/Vts\ = (m(d)/m(s))(1/2) between the CKM matrix elements and the quark masses are shown to imply a remarkably precise determination of the CKM unitarity triangle or of the Wolfenstein parameters rho, eta consistent with the data so far, We view this as a clean test of a quark mass texture neatly arising from a hierarchical breaking of a U(2) flavour symmetry. (C) 1999 Elsevier Science B.V. All rights reserved
An SU(5)xU(2) theory of fermion masses and mixings
No full textA model of fermion masses and mixing parameters is described based on the SU(5) gauge group and on a U(2) flavour group. The model gives a qualitative understanding of the pattern of masses and mixings in terms of U(2) and SU(5) breakings and it reduces in a unique way the 13 physical parameters in the Yukawa sector of the Standard Model to 8 real parameters plus 2 phases, accounting for all observed data so far. Predictions for the B-s - <(B)over bar (s)> mixing parameter, a class of CP asymmetries in neutral B-decays and the branching ratio BR(K+ --> pi(+) <nu(nu)over bar>) are made
Flavour physics, flavour symmetries, supersymmetry and unification
No full textWhile solving the supersymmetric flavour problem, a U(2) flavour symmetry might be at the origin of the pattern of fermion masses and mixings. The consequences of this hypothesis are spelled out concerning the parameters of the CKM matrix and their observability in B- and K-physics. The relevance of searching for lepton flavour violation and for the electric dipole moments of the electron and the neutron is also emphasized
Unified theories with U(2) flavor symmetry
No full textA general operator expansion is presented for quark and lepton mass matrices in unified theories based on a U(2) flavor symmetry, with breaking parameter of order V-cb approximate to m(s)/m(b) approximate to root m(c)/m(t). While solving the supersymmetric flavor-changing problem, a general form for the Yukawa couplings follows, leading to nine relations among the fermion masses and mixings, five of which are precise. The combination of grand unified and U(2) symmetries provides a symmetry understanding for the anomalously small values of m(u)/m(c) and m(c)/m(t). A fit to the fermion mass data leads to a prediction for the angles of the CKM unitarity triangle, which will allow a significant test of these unified U(2) theories. A particular SO(10) model provides a simple realization of the general operator expansion. The lighter generation masses and the non-trivial structure of the CKM matrix are generated from the exchange of a single U(2) doublet of heavy vector generations. This model suggests that CP is spontaneously broken at the unification scale-in which case there is a further reduction in the number of free parameters. (C) 1997 Elsevier Science B.V
Dark energy and right-handed neutrinos
No full textWe explore the possibility that a CP violating phase of the neutrino mass matrix is promoted to a pseudo-Goldstone-boson field and is identified as the quintessence field for Dark Energy. By requiring that the quintessence potential be calculable from a Lagrangian, and that the extreme flatness of the potential be stable under radiative corrections, we are led to an essentially unique model. Lepton number is violated only by Majorana masses of light right-handed neutrinos, comparable to the Dirac masses that mix right- with left-handed neutrinos. We outline the rich and constrained neutrino phenomenology that results from this proposal. (c) 2005 Elsevier B.V. All rights reserved
Multi-muon events at the Tevatron: a hidden sector from hadronic collisions
No full textWe show an explicit attempt to interpret the multi-muon anomaly recently claimed by the CDF Collaboration in terms of a light scalar singlet phi which communicates with the standard quarks either through a heavy scalar or a heavy fermion exchange. Building on arXiv:0810.5730, that suggested a singlet phi with a chain decay into a final state made of four tau(tau) over bar pairs, we can simulate most of the muon properties of the selected sample of events. Some of these properties adhere rather well to the already published data; others should allow a decisive test of the proposed interpretation. Assuming that the test is positively passed, we show how the PAMELA excess can be fitted by the annihilation of a TeV dark matter particle that communicates with the Standard Model via the new light singlet(s)
Fermion masses and symmetry breaking of a U(2) flavour symmetry RID F-4311-2011
No full textWe show how a specific sequential breaking pattern of a U(2) flavour symmetry occurs automatically in a broad framework. The relative orientation in U(2) space of the spurion fields that breaks the U(2) symmetry is uniquely fixed, thus determining the form of the fermion mass matrices in a predictive way. (C) 1999 Elsevier Science B.V. All rights reserved
Consequences of a U(2) flavour symmetry
No full textWhile solving the supersymmetric flavour problem, a U(2) flavour symmetry might be at the origin of the pattern of fermion masses and mixings. The consequences of this hypothesis are spelled out concerning the parameters of the CKM matrix and their observability in B- and K-physics. The relevance of searching for lepton flavour violation and for the electric dipole moments of the electron and the neutron is also emphasized. (C) 1997 Elsevier Science B.V
Textures for atmospheric and solar neutrino oscillations
No full textA large theta(mu tau) mixing angle, together with hierarchies in the neutrino Delta m(2) and in the charged lepton masses, place a significant restriction on the textures of the lepton mass matrices. In theories with three light neutrinos, a simple hypothesis leads to a complete list of four zeroth-order textures for lepton mass matrices is found: three for neutrinos which naturally yield theta(mu tau) approximate to 1 with vanishing theta(e tau) and Delta m(.)(2), and one for charged leptons which naturally yields theta(mu tau) approximate to 1 with m(e) = m(mu) = theta(e tau) = 0. These textures provide suitable starting points for constructing theories which account for both atmospheric and solar neutrino fluxes. Using flavor symmetries, two schemes for such lepton masses are found, and example constructions exhibited. (C) 1999 Elsevier Science B.V. All rights reserved
- …
