4,161 research outputs found

    More on Symmetries in Heavy Quark Effective Theory

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    We present a general classification of all normal and ``chiral" symmetries of heavy quark effective theories. Some peculiarities and conondrums associated with the ``chiral" symmetries are discussed.Comment: 15 pages, preprint UR-1320, ER40685-77

    Anthropic tuning of the weak scale and of m_u/m_d in two-Higgs-doublet models

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    It is shown that in a model in which up-type and down-type fermions acquire mass from different Higgs doublets, the anthropic tuning of the Higgs mass parameters can explain the fact that the observed masses of the dd and uu quarks are nearly the same with dd slightly heavier. If Yukawa couplings are assumed not to "scan" (vary among domains), this would also help explain why the t quark is much heavier than the b quark. It is also pointed out that the existence of dark matter invalidates some earlier anthropic arguments against the viability of domains where the Standard Model Higgs has positive μ2\mu^2, but makes other even stronger arguments possible.Comment: 31 pages, 7 figure

    A Truly Minimal Left-Right Symmetric Extension of the Standard Model

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    By invoking the existence of a general custodial O(2) symmetry, a minimal Left-Right symmetric model based on the gauge group G=SU(2)L SU(2)R U(1)BL is shown to require the existence of only two physical Higgs bosons. The lighter Higgs is predicted to have a small mass which could be evaluated by standard perturbation theory. The fermionic mass matrices are recovered by insertion of ad hoc fermion-Higgs interactions. The model is shown to be undistinguishable from the standard model at the currently reachable energies.Comment: 1 figure in a separate ps fil

    B Meson Transitions into Higher Mass Charmed Resonances

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    We use QCD sum rules to estimate the universal form factors describing the semileptonic B decays into excited charmed resonances, such as the 11^- and 22^- states D1D_1^{*} and D2D_2^{*} belonging to the sP=3/2s_\ell^P={3/2}^- heavy quark doublet, and the 22^- and 33^- states D2D_2^{*\prime} and D3D_3 belonging to the s_\ell^P={5\2}^- doublet.Comment: LaTex, 14 pages, 1 figur

    A Traceable Ground to On-Orbit Radiometric Calibration System for the Solar Reflective Wavelength Region

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    This paper describes the combination of a Mie scattering spectral BSDF and BTDF albedo standard whose calibration is traceable to the NIST SIRCUS Facility or the NIST STARR II Facility. The Space-based Calibration Transfer Spectroradiometer (SCATS) sensor uses a simple, invariant optical configuration and dedicated narrow band spectral channel modules to provide very accurate, polarization-insensitive, stable measurements of earth albedo and lunar disk albedo. Optical degradation effects on calibration stability are eliminated through use of a common optical system for observations of the Sun, Earth, and Moon. The measurements from space would be traceable to SI units through preflight calibrations of radiance and irradiance at NIST's SIRCUS facility and the invariant optical system used in the sensor. Simultaneous measurements are made in multiple spectral channels covering the solar reflective wavelength range of 300 nm to 2.4 microns. The large dynamic range of signals is handled by use of single-element, highly-linear detectors, stable discrete electronic components, and a non imaging optical configuration. Up to 19 spectral modules can be mounted on a single-axis drive to give direct pointing at the Earth and at least once per orbit view of the Sun and Moon. By observing the Sun on every orbit, the most stringent stability requirements of the system are limited to short time periods. The invariant optical system for both radiance and irradiance measurements also give excellent transfer to-orbit SI traceability. Emerging instrumental requirements for remotely sensing tropospheric trace species have led to a rethinking by some of the paradigm for Systeme International d'Unites (SI) traceability of the spectral irradiance and radiance radiometric calibrations to spectral albedo (sr(exp -1)) which is not a SI unit. In the solar reflective wavelength region the spectral albedo calibrations are tied often to either the spectral albedo of a solar diffuser or the Moon. This new type of Mie scattering diffuser (MSD) is capable of withstanding high temperatures, and is more Lambertian than Spectralon(tm). It has the potential of covering the entire solar reflective wavelength region. Laboratory measurements have shown that the specular reflectance component is negligible, and indicate that internal absorption by multiple scattering is small. This MSD, a true volume diffuser, exhibits a high degree of radiometric stability which suggests that measurements at the National Institute of Standards and Technology (NIST) could provide a spectral albedo standard. Measurements have been made of its radiometric stability under a simulated space environment of high energy gamma rays, high energy protons, and UV radiation from ambient down to the vacuum ultraviolet H Lyman alpha at 121.6 nm for its eventual use in space as a solar diffuser

    Three Jet Events and New Strong Couplings at LEP and NLC

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    We study the effects of new dimension--6 operators, resulting from a general SU(3)CSU(2)LU(1)YSU(3)_C \otimes SU(2)_L \otimes U(1)_Y invariant effective Lagrangian, on three jet production at LEP and at the Next Linear Collider. Contributions to the total event rate and to some event shape variables are analysed in order to establish bounds on these operators.Comment: 5 pages, LaTeX, 1 Figur

    Baryon Masses at Second Order in Chiral Perturbation Theory

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    We analyze the baryon mass differences up to second order in chiral perturbation theory, including the effects of decuplet intermediate states. We show that the Coleman--Glashow relation has computable corrections of order (mdmu)ms(m_d - m_u) m_s. These corrections are numerically small, and in agreement with the data. We also show that corrections to the Σ\Sigma equal-spacing rule are dominated by electromagnetic contributions, and that the Gell-Mann--Okubo formula has non-analytic corrections of order ms2lnmsm_s^2 \ln m_s which cannot be computed from known matrix elements. We also show that the baryon masses cannot be used to extract model-independent information about the current quark masses.Comment: 11 pages, 1 uu-encoded figure, LBL-34779, UCB-PTH-93/2

    Systematic Low-Energy Effective Field Theory for Magnons and Holes in an Antiferromagnet on the Honeycomb Lattice

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    Based on a symmetry analysis of the microscopic Hubbard and t-J models, a systematic low-energy effective field theory is constructed for hole-doped antiferromagnets on the honeycomb lattice. In the antiferromagnetic phase, doped holes are massive due to the spontaneous breakdown of the SU(2)sSU(2)_s symmetry, just as nucleons in QCD pick up their mass from spontaneous chiral symmetry breaking. In the broken phase the effective action contains a single-derivative term, similar to the Shraiman-Siggia term in the square lattice case. Interestingly, an accidental continuous spatial rotation symmetry arises at leading order. As an application of the effective field theory we consider one-magnon exchange between two holes and the formation of two-hole bound states. As an unambiguous prediction of the effective theory, the wave function for the ground state of two holes bound by magnon exchange exhibits ff-wave symmetry.Comment: 33 pages, 6 figure

    Gravity-Yang-Mills-Higgs unification by enlarging the gauge group

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    We revisit an old idea that gravity can be unified with Yang-Mills theory by enlarging the gauge group of gravity formulated as gauge theory. Our starting point is an action that describes a generally covariant gauge theory for a group G. The Minkowski background breaks the gauge group by selecting in it a preferred gravitational SU(2) subgroup. We expand the action around this background and find the spectrum of linearized theory to consist of the usual gravitons plus Yang-Mills fields charged under the centralizer of the SU(2) in G. In addition, there is a set of Higgs fields that are charged both under the gravitational and Yang-Mills subgroups. These fields are generically massive and interact with both gravity and Yang-Mills sector in the standard way. The arising interaction of the Yang-Mills sector with gravity is also standard. Parameters such as the Yang-Mills coupling constant and Higgs mass arise from the potential function defining the theory. Both are realistic in the sense explained in the paper.Comment: 61 pages, no figures (v2) some typos correcte

    Vector Meson Exchanges and CP Asymmetry in K±π±π0K^{\pm}\rightarrow\pi^{\pm}\pi^0

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    Using a current algebra framework, we discuss the contribution of vector meson exchanges to the CP violating asymmetry in the decay K±π±π0K^{\pm}\rightarrow\pi^{\pm}\pi^0, resulting from the interference of the KππK\rightarrow\pi\pi amplitude with the radiative correction KππγK\rightarrow\pi\pi\gamma.Comment: 9 pages (plain-TEX), IC/93/186, UTS-DFT-93-18, (two figures not included
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