155 research outputs found

### Quark Dipole Operators in Extended Technicolor Models

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 $b \to s \gamma$ and $B_{d} \to \phi
K_S$, $Re(\epsilon^\prime/\epsilon)$, and the electric dipole moments of the
neutron and the ${}^{199}$Hg atom.Comment: 9 pages, late

### Lepton Dipole Moments in Extended Technicolor Models

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

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 $|\Delta L|=2$ 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

We review the phase structure of a three-dimensional, non-compact Abelian
gauge theory (QED3) as a function of the number $N$ of 4-component massless
fermions. There is a critical $N_{c}$ up to which there is dynamical fermion
mass generation and an associated global symmetry breaking. We discuss various
approaches to the determination of $N_c$, which lead to estimates ranging from
$N_c =1$ to $N_c =4$. 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
$N_c$ 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

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

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 $N_f$
flavors of quark and squark fields, and with $N_f$ 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

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

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