155 research outputs found

    Quark Dipole Operators in Extended Technicolor Models

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    We study diagonal and transition quark dipole operators in a class of extended technicolor (ETC) models, taking account of the multiscale nature of the ETC gauge symmetry breaking and of the mixing among ETC interaction eigenstates. Because of this mixing, terms involving the lowest ETC scale can play an important role in dipole operators, and we focus on these terms. We derive from experiment new correlated constraints on the quark mixing angles and phases. Our bounds yield information on mixing angles individually in the up- and down-sectors, for both left- and right-handed quark fields and thus constrain even quark mixing parameters that do not enter in the CKM matrix. With phases of order unity, we conclude that these mixing angles are small, constraining future ETC model building, but plausibly in the range suggested by the size of the CKM elements. These values still allow substantial deviations from the standard model predictions, in particular for several CP violating quantities, including the asymmetries in bsγb \to s \gamma and BdϕKSB_{d} \to \phi K_S, Re(ϵ/ϵ)Re(\epsilon^\prime/\epsilon), and the electric dipole moments of the neutron and the 199{}^{199}Hg atom.Comment: 9 pages, late

    Lepton Dipole Moments in Extended Technicolor Models

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    We analyze the diagonal and transition magnetic and electric dipole moments of charged leptons in extended technicolor (ETC) models, taking account of the multiscale nature of the ETC gauge symmetry breaking, conformal (walking) behavior of the technicolor theory, and mixing in the charged-lepton mass matrix. We show that mixing effects dominate the ETC contributions to charged lepton electric dipole moments and that these can yield a value of |d_e| comparable to the current limit. The rate for mu to e gamma can also be close to its limit. From these and other processes we derive constraints on the charged lepton mixing angles. The constraints are such that the ETC contribution to the muon anomalous magnetic moment, which includes a significant lepton mixing term, can approach, but does not exceed, the current sensitivity level.Comment: 4 pages, revte

    Neutrino Masses in Theories with Dynamical Electroweak Symmetry Breaking

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    We address the problem of accounting for light neutrino masses in theories with dynamical electroweak symmetry breaking. We discuss this in the context of a class of (extended) technicolor (ETC) models and analyze the full set of Dirac and Majorana masses that arise in such theories. As a possible solution, we propose a combination of suppressed Dirac masses and a seesaw involving dynamically generated ΔL=2|\Delta L|=2 condensates of standard-model singlet, ETC-nonsinglet fermions. We show how this can be realized in an explicit ETC model. An important feature of this proposal is that, because of the suppression of Dirac neutrino mass terms, a seesaw yielding realistic neutrino masses does not require superheavy Majorana masses; indeed, these Majorana masses are typically much smaller than the largest ETC scale.Comment: 13 pages, latex; simplified mode

    Phase Structure of Non-Compact QED3 and the Abelian Higgs Model

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    We review the phase structure of a three-dimensional, non-compact Abelian gauge theory (QED3) as a function of the number NN of 4-component massless fermions. There is a critical NcN_{c} up to which there is dynamical fermion mass generation and an associated global symmetry breaking. We discuss various approaches to the determination of NcN_c, which lead to estimates ranging from Nc=1N_c =1 to Nc=4N_c =4. This theory with N=2 has been employed as an effective continuum theory for the 2D quantum antiferromagnet where the observed Neel ordering corresponds to dynamical fermion mass generation. Thus the value of NcN_c is of some physical interest. We also consider the phase structure of the model with a finite gauge boson mass (the Abelian Higgs model).Comment: 14 pages, corrected the normalization of the fermion condensate in section V, corrected a typo in the reference

    A Light Dilaton in Walking Gauge Theories

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    We analyze the existence of a dilaton in gauge theories with approximate infrared conformal symmetry. To the extent that these theories are governed in the infrared by an approximate fixed point (walking), the explicit breaking of the conformal symmetry at these scales is vanishingly small. If confinement and spontaneous chiral-symmetry breaking set in at some infrared scale, the resultant breaking of the approximate conformal symmetry can lead to the existence of a dilaton with mass parametrically small compared to the confinement scale, and potentially observable at the LHC.Comment: 5 pages, references added, final version in PR

    Analyzing Chiral Symmetry Breaking in Supersymmetric Gauge Theories

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    We compare gap equation predictions for the spontaneous breaking of global symmetries in supersymmetric Yang-Mills theory to nonperturbative results from holomorphic effective action techniques. In the theory without matter fields, both approaches describe the formation of a gluino condensate. With NfN_f flavors of quark and squark fields, and with NfN_f below a certain critical value, the coupled gap equations have a solution for quark and gluino condensate formation, corresponding to breaking of global symmetries and of supersymmetry. This appears to disagree with the newer nonperturbative techniques, but the reliability of gap equations in this context and whether the solution represents the ground state remain unclear.Comment: LaTex, 14 pages, including 1 figure in EPS format. Revised to correct gluino anomalous dimension, with minor accompanying text change

    The Zero Temperature Chiral Phase Transition in SU(N) Gauge Theories

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    We investigate the zero temperature chiral phase transition in an SU(N) gauge theory as the number of fermions NfN_f is varied. We argue that there exists a critical number of fermions NfcN_f^c, above which there is no chiral symmetry breaking or confinement, and below which both chiral symmetry breaking and confinement set in. We estimate NfcN_f^c and discuss the nature of the phase transition.Comment: 13 pages, LaTeX, version published in PR
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