5,430 research outputs found

### Lepton-number violation and right-handed neutrinos in Higgs-less effective theories

Following previous work, we identify a symmetry S_nat that generalizes the
concept of custodial symmetry, keeping under control deviations from the
Standard Model (SM). To realize S_nat linearly, the space of gauge fields has
to be extended. Covariant constraints formulated in terms of spurions reduce
S_nat back to SU(2)_L x U(1)_Y. This allows for a covariant introduction of
explicit S_nat-breaking parameters. We assume that S_nat is at play in a theory
of electroweak symmetry-breaking without a light Higgs particle. We describe
some consequences of this assumption, using a non-decoupling effective theory
in which the loop expansion procedure is based on both momentum and spurion
power counting, as in Chiral Perturbation Theory. A hierarchy of lepton-number
violating effects follows. Leading corrections to the SM are non-oblique. The
effective theory includes stable light right-handed neutrinos, with an unbroken
Z_2 symmetry forbidding neutrino Dirac masses. nu_R contribution to dark matter
places bounds on their masses.Comment: Corresponds to published version: added subsection VI-D about
order-of-magnitude estimate

### Classical trajectories and quantum supersymmetry

We analyze a supersymmetric system with four flat directions. We observe
several interesting properties, such as the coexistence of the discrete and
continuous spectrum in the same range of energies. We also solve numerically
the classical counterpart of this system. A similar analysis is then done for
an alike, but non-supersymmetric system. The comparison of theses classical and
quantum results may serve as a suggestion about classical manifestations of
supersymmetry.Comment: 16 pages, 12 figures, 5 tables, some misspellings correcte

### The flavor physics in unified gauge theory from an S_3*P discrete symmetry

We investigate the phenomenological implication of the discrete symmetry
S_3*P on flavor physics in SO(10) unified theory. We construct a minimal
renormalizable model which reproduces all the masses and mixing angle of both
quarks and leptons. As usually the SO(10) symmetry gives up to relations
between the down sector and the charged lepton masses. The underlining discrete
symmetry gives a contribution (from the charged lepton sector) to the PMNS
mixing matrix which is bimaximal. This gives a strong correlation between the
down quark and charged lepton masses, and the lepton mixing angles. We obtain
that the small entries V_{ub}, V_{cb}, V_{td}, and V_{ts} in the CKM matrix are
related to the small value of the ratio "dm^2_{sol}/dm^2_{atm}": they come from
both the S_2*P structure of our model and the small ratio of the other quark
masses with respect to m_t.Comment: 5 pages, revtex4. v2: published versio

### (De)Constructing Dimensions

We construct renormalizable, asymptotically free, four dimensional gauge
theories that dynamically generate a fifth dimension.Comment: 10 pages, late

### Evolution of Structure Functions And Their Moments In Chiral Field Theory

Evolution of structure functions and their moments at low and moderate $Q^2$
is studied in the chiral field theory. Evolution equations based on
perturbation expansion in the coupling constant of the effective theory are
derived and solved for the moments. The kernels of evolution arising from
different processes have been calculated with contributions from direct and
cross channels, the interference terms being non-negligible in the kinematic
regions under consideration. This is shown to lead to flavor-dependence of the
kernels which manifests in observable effects. The invalidity of the
probabilistic approach to the evolution process is also pointed out.Comment: 18 pages, LaTex, 5 figure

### Proton Decay and Fermion Masses in Supersymmetric SO(10) Model with Unified Higgs Sector

We make a detailed analysis on the proton decay in a supersymmetric SO(10)
model proposed by K.Babu, I.Gogoladze, P.Nath, and R. Syed. We introduce quark
mixing, and find that this model can generate fermion mass without breaking the
experimental bound on proton decay. We also predict large CKM unitarity
violations.Comment: 7 page

### Tri-N-ification

We consider a natural generalization of trinification to theories with 3N
SU(3) gauge groups. These theories have a simple moose representation and a
gauge boson spectrum that can be interpreted via the deconstruction of a 5D
theory with unified symmetry broken on a boundary. Although the matter and
Higgs sectors of the theory have no simple extra-dimensional analog, gauge
unification retains features characteristic of the 5D theory. We determine
possible assignments of the matter and Higgs fields to unified multiplets and
present theories that are viable alternatives to minimal trinified GUTs.Comment: 21 pages LaTeX, 6 eps figure

### Staggered Heavy Baryon Chiral Perturbation Theory

Although taste violations significantly affect the results of staggered
calculations of pseudoscalar and heavy-light mesonic quantities, those entering
staggered calculations of baryonic quantities have not been quantified. Here I
develop staggered chiral perturbation theory in the light-quark baryon sector
by mapping the Symanzik action into heavy baryon chiral perturbation theory.
For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are
calculated to third order in partially quenched and fully dynamical staggered
chiral perturbation theory. To this order the expansion includes the leading
chiral logarithms, which come from loops with virtual decuplet-like states, as
well as terms the order of the cubed pion mass, which come from loops with
virtual octet-like states. Taste violations enter through the meson propagators
in loops and tree-level terms the order of the squared lattice spacing. The
pattern of taste symmetry breaking and the resulting degeneracies and mixings
are discussed in detail. The resulting chiral forms are appropriate to lattice
results obtained with operators already in use and could be used to study the
restoration of taste symmetry in the continuum limit. I assume that the fourth
root of the fermion determinant can be incorporated in staggered chiral
perturbation theory using the replica method.Comment: 54 pages; v2: corrected discussion in Sec. III.C, conclusions
unchange

- â€¦