Masses and Mixings in a Grand Unified Toy Model

The generation of the fermion mass hierarchy in the standard model of particle physics is a long-standing puzzle. The recent discoveries from neutrino physics suggests that the mixing in the lepton sector is large compared to the quark mixings. To understand this asymmetry between the quark and lepton mixings is an important aim for particle physics. In this regard, two promising approaches from the theoretical side are grand unified theories and family symmetries. In this note we try to understand certain general features of grand unified theories with Abelian family symmetries by taking the simplest SU(5) grand unified theory as a prototype. We construct an SU(5) toy model with $U(1)_F \otimes Z'_2\otimes Z''_2 \otimes Z'''_2$ family symmetry that, in a natural way, duplicates the observed mass hierarchy and mixing matrices to lowest approximation. The system for generating the mass hierarchy is through a Froggatt-Nielsen type mechanism. One idea that we use in the model is that the quark and charged lepton sectors are hierarchical with small mixing angles while the light neutrino sector is democratic with larger mixing angles. We also discuss some of the difficulties in incorporating finer details into the model without making further assumptions or adding a large scalar sector.Comment: 21 pages, 2 figures, RevTeX, v2: references updated and typos corrected, v3: updated top quark mass, comments on MiniBooNE result, and typos correcte

Atomic Parity Violation and Precision Electroweak Physics - An Updated Analysis

A new analysis of parity violation in atomic cesium has led to the improved value of the weak charge, $Q_W({\rm Cs}) = -72.06 \pm 0.46$. The implications of this result for constraining the Peskin-Takeuchi parameters S and T and for guiding searches for new Z bosons are discussed.Comment: 8 pages, LaTeX, 3 figures, Submitted to Physical Review D. Updated experimental inputs and references; clarification of notatio

VtdV_{td} from Hadronic Two-Body BB Decays

Certain hadronic two-body decays of $B$ mesons are dominated by penguin diagrams. The ratios of rates for several such decays, including $\Gamma(B^0 \to \overline{K}^{*0} K^0)/\Gamma(B^0 \to \phi K^0)$, $\Gamma(B^0 \to \overline{K}^{*0} K^{*0})/\Gamma(B^0 \to \phi K^{*0})$, $\Gamma(B^+ \to \overline{K}^{*0} K^+)$ $/\Gamma(B^+ \to \phi K^+)$, and $\Gamma(B^+ \to \overline{K}^{*0} K^{*+})/\Gamma(B^+ \to \phi K^{*+})$, can provide information on the ratio of Cabibbo-Kobayashi-Maskawa (CKM) elements $|V_{td}/V_{ts}|$ in a manner complementary to other proposed determinations. SU(3) breaking effects cancel in some ratios. The cases of neutral $B$ decays are free of corrections from small annihilation terms.Comment: 11 pages, latex, no figure

Role of Present and Future Atomic Parity Violation Experiments in Precision Electroweak Tests

Recent reanalyses of the atomic physics effects on the weak charge in cesium have led to a value in much closer agreement with predictions of the Standard Model. We review precision electroweak tests, their implications for upper bounds on the mass of the Higgs boson, possible ways in which these bounds may be circumvented, and the requirements placed upon accuracy of future atomic parity violation experiments by these considerations.Comment: 10 pages, LaTeX, 1 figure, to be submitted to Physical Review D, new data on neutrino deep inelastic scattering include

Model of the Quark Mixing Matrix

The structure of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is analyzed from the standpoint of a composite model. A model is constructed with three families of quarks, by taking tensor products of sufficient numbers of spin-1/2 representations and imagining the dominant terms in the mass matrix to arise from spin-spin interactions. Generic results then obtained include the familiar relation $|V_{us}| = (m_d/m_s)^{1/2} - (m_u/m_c)^{1/2}$, and a less frequently seen relation $|V_{cb}| = \sqrt{2} [(m_s/m_b) - (m_c/m_t)]$. The magnitudes of $V_{ub}$ and $V_{td}$ come out naturally to be of the right order. The phase in the CKM matrix can be put in by hand, but its origin remains obscure.Comment: Presented by Mihir P. Worah at DPF 92 Meeting, Fermilab, November, 1992. 3 pages, LaTeX fil

CKM Matrix and Standard-Model CP Violation

The currently favored model of CP violation is based on phases in the Cabibbo-Kobayashi-Maskawa (CKM) matrix describing the weak charge-changing couplings of quarks. The present status of parameters of this matrix is described. Tests of the theory, with particular emphasis on the study of B meson decays, are then noted. Some remarks are made regarding the possible origin of the baryon asymmetry of the universe; the corresponding coupling pattern of the leptons could shed light on the question. Some possibilities for non-standard physics are discussed.Comment: 16 pages, latex, 8 figures. Invited talk at Fourth KEK Topical Conference on Flavour Physics, 29 -- 31 October 1996. To be published in Nucl. Phys. B (Proc. Suppl.

Measurement of the W-boson mass in pp collisions at √s=7 TeV with the ATLAS detector

A measurement of the mass of the W boson is presented based on proton–proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6 fb−1 of integrated luminosity. The selected data sample consists of 7.8×106 candidates in the W→μν channel and 5.9×106 candidates in the W→eν channel. The W-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the W boson transverse mass in the electron and muon decay channels, yielding mW=80370±7 (stat.)±11(exp. syst.) ±14(mod. syst.) MeV =80370±19MeV, where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the W+ and W−bosons yields mW+−mW−=−29±28 MeV