35 research outputs found
LEP Indications for Two Light Higgs Bosons and U(1)' Model
Reanalyses of LEP data have shown preference to two light CP-even Higgs
bosons. We discuss implications of such a Higgs boson spectrum for the minimal
supersymmetric model extended by a Standard Model singlet chiral superfield and
an additional Abelian gauge invariance (the U(1)' model). We, in particular,
determine parameter regions that lead to two light CP-even Higgs bosons while
satisfying existing bounds on the mass and mixings of the extra vector boson.
In these parameter regions, the pseudoscalar Higgs is found to be nearly
degenerate in mass with either the lightest or next-to-lightest Higgs boson.
Certain parameters of the U(1)' model such as the effective mu parameter are
found to be significantly bounded by the LEP two-light-Higgs signal.Comment: 20 pp, 7 figs, 2 table
Dirac Neutrino Masses from Generalized Supersymmetry Breaking
We demonstrate that Dirac neutrino masses in the experimentally preferred
range are generated within supersymmetric gauge extensions of the Standard
Model with a generalized supersymmetry breaking sector. If the usual
superpotential Yukawa couplings are forbidden by the additional gauge symmetry
(such as a U(1)'), effective Dirac mass terms involving the "wrong Higgs" field
can arise either at tree level due to hard supersymmetry breaking fermion
Yukawa couplings, or at one-loop due to nonanalytic or "nonholomorphic" soft
supersymmetry breaking trilinear scalar couplings. As both of these operators
are naturally suppressed in generic models of supersymmetry breaking, the
resulting neutrino masses are naturally in the sub-eV range. The neutrino
magnetic and electric dipole moments resulting from the radiative mechanism
also vanish at one-loop order.Comment: 5 pages, 1 figure, references added, note added on effective
superpotential mass terms generated upon U(1)' breakin
Sneutrino Dark Matter: Symmetry Protection and Cosmic Ray Anomalies
We present an R-parity conserving model of sneutrino dark matter within a
Higgs-philic U(1)' extension of the minimal supersymmetric standard model. In
this theory, the mu parameter and light Dirac neutrino masses are generated
naturally upon the breaking of the U(1)' gauge symmetry. The leptonic and
hadronic decays of sneutrinos in this model, taken to be the lightest and
next-to-lightest superpartners, allow for a natural fit to the recent results
reported by the PAMELA experiment.Comment: Revised to match the published version; 11 pages (2 column format), 1
table, 6 figures, to appear in PR
Tevatron Higgs Mass Bounds: Projecting U(1)' Models to LHC Domain
We study Higgs boson masses in supersymmetric models with an extra U(1)
symmetry to be called U(1). Such extra gauge symmetries are urged by
the problem of the MSSM, and they also arise frequently in low-energy
supersymmetric models stemming from GUTs and strings. We analyze mass of the
lightest Higgs boson and various other particle masses and couplings by taking
into account the LEP bounds as well as the recent bounds from Tevatron
experiments. We find that the -problem motivated generic low-energy
U(1) model yields Higgs masses as large as and
violate the Tevatron bounds for certain ranges of parameters. We analyze
correlations among various model parameters, and determine excluded regions by
both scanning the parameter space and by examining certain likely parameter
values. We also make educated projections for LHC measurements in light of the
Tevatron restrictions on the parameter space. We further analyze certain
benchmark models stemming from E(6) breaking, and find that they elevate Higgs
boson mass into Tevatron's forbidden band when U(1) gauge coupling
takes larger values than the one corresponding to one-step GUT breaking.Comment: 11 pages, 3 figure
Scalars, Vectors and Tensors from Metric-Affine Gravity
The metric-affine gravity provides a useful framework for analyzing
gravitational dynamics since it treats metric tensor and affine connection as
fundamentally independent variables. In this work, we show that, a
metric-affine gravity theory composed of the invariants formed from
non-metricity, torsion and curvature tensors can be decomposed into a theory of
scalar, vector and tensor fields. These fields are natural candidates for the
ones needed by various cosmological and other phenomena. Indeed, we show that
the model accommodates TeVeS gravity (relativistic modified gravity theory),
vector inflation, and aether-like models. Detailed analyses of these and other
phenomena can lead to a standard metric-affine gravity model encoding scalars,
vectors and tensors.Comment: 13 p
Higher Curvature Quantum Gravity and Large Extra Dimensions
We discuss effective interactions among brane matter induced by modifications
of higher dimensional Einstein gravity via the replacement of Einstein-Hilbert
term with a generic function f(R) of the curvature scalar R. After deriving the
graviton propagator, we analyze impact of virtual graviton exchanges on
particle interactions, and conclude that f(R) gravity effects are best probed
by high-energy processes involving massive gauge bosons, heavy fermions or the
Higgs boson. We perform a comparative analysis of the predictions of f(R)
gravity and of Arkani-Hamed-Dvali-Dimopoulos (ADD) scenario, and find that the
former competes with the latter when f''(0) is positive and comparable to the
fundamental scale of gravity in higher dimensions. In addition, we briefly
discuss graviton emission from the brane as well as its decays into
brane-localized matter, and find that they hardly compete with the ADD
expectations. Possible existence of higher-curvature gravitational interactions
in large extra spatial dimensions opens up various signatures to be confronted
with existing and future collider experiments.Comment: 19 pp, 2 figs. Added references, corrected typo
Nonlinearly Realized Local Scale Invariance: Gravity and Matter
That the scalar field theories with no dimensional couplings possess local
scale invariance (LSI) via the curvature gauging is utilized to show that the
Goldstone boson, released by the spontaneous LSI breakdown, is swallowed by the
spacetime curvature in order to generate Newton's constant in the same spirit
as the induction of vector boson masses via spontaneous gauge symmetry
breaking. For Einstein gravity to be reproduced correctly, the Goldstone boson
of spontaneous LSI breaking must be endowed with ghost dynamics. The matter
sector, taken to be the standard model spectrum, gains full LSI with the
physical Higgs boson acting as the Goldstone boson released by LSI breakdown at
the weak scale. The pattern of particle masses is identical to that of the
standard model. There are unitary LSI gauges in which either the Goldstone
ghost from gravity sector or the Higgs boson from matter sector is eliminated
from the spectrum. The heavy right-handed neutrinos as well as softly broken
supersymmetry naturally fit into the nonlinearly realized LSI framework.Comment: 12pp, added a referenc
Non-Gravitating Scalars and Spacetime Compactification
We discuss role of partially gravitating scalar fields, scalar fields whose
energy-momentum tensors vanish for a subset of dimensions, in dynamical
compactification of a given set of dimensions. We show that the resulting
spacetime exhibits a factorizable geometry consisting of usual four-dimensional
spacetime with full Poincare invariance times a manifold of extra dimensions
whose size and shape are determined by the scalar field dynamics. Depending on
the strength of its coupling to the curvature scalar, the vacuum expectation
value (VEV) of the scalar field may or may not vanish. When its VEV is zero the
higher dimensional spacetime is completely flat and there is no
compactification effect at all. On the other hand, when its VEV is nonzero the
extra dimensions get spontaneously compactified. The compactification process
is such that a bulk cosmological constant is utilized for curving the extra
dimensions.Comment: 18 pp, 1 fi
Higgs boson couplings to quarks with supersymmetric CP and flavor violations
In minimal supersymmetric model (SUSY) with a light Higgs sector, explicit CP
violation and most general flavor mixings in the sfermion sector, integration
of the superpartners out of the spectrum induces potentially large
contributions to the Yukawa couplings of light quarks via those of the heavier
ones. These corrections can be sizeable even for moderate values of tan(beta),
and remain nonvanishing even if all superpartners decouple. When the SUSY
breaking scale is close to the electroweak scale, the Higgs exchange effects
can compete with the gauge boson and box diagram contributions to rare
processes, and their partial cancellations can lead to relaxation of the
existing bounds on flavor violation sources. In this case there exist sizeable
enhancements in flavor-changing Higgs decays. When the superpartners completely
decouple, however, the Higgs mediation becomes the dominant SUSY contribution
to rare processes the saturation of which, without a strong suppression of the
flavor mixings, prefers large tan(beta) and certain ranges for the CP-odd
phases. The decay rate of the lightest Higgs into light down quarks become
comparable with that into the bottom quark. Moreover, the Higgs decay into the
up quark is significantly enhanced. There are observable implications for rare
processes, atomic electric dipole moments, and collider searches for Higgs
bosons.Comment: 20 pp. Added references, improved the discussion of FCNC
constraints;journal versio
General Tensor Lagrangians from Gravitational Higgs Mechanism
The gravitational Higgs mechanism proposed by 't Hooft in arXiv:0708.3184
involves the spacetime metric g_{mu nu} as well as the induced metric
\bar{g}_{mu nu} proportional to \eta_{a b} \partial_{mu} \phi^a \partial_{nu}
\phi^b where \phi^{a} (a=0,...,3), as we call it, break all four
diffeomorphisms spontaneously via the vacuum expectation values
proportional to x^a. In this framework, we construct and analyze the most
general action density in terms of various invariants involving the curvature
tensors, connexion coefficients, and the contractions and the determinants of
the two metric fields. We show that this action admits a consistent expansion
about the flat background such that the resulting Lagrangian possesses several
novel features not found in the linearized Einstein-Hilbert Lagrangian with
Fierz-Pauli mass term (LELHL-FP): (i) its kinetic part generalizes that of
LELHL-FP by weighing the corresponding structures with certain coefficients
generated by invariants, (ii) the entire Lagrangian is ghost-- and
tachyon--free for mass terms not necessarily in the Fierz-Pauli form, and,
(iii) a consistent mass term is generated with no apparent need to higher
derivative couplings.Comment: 20 pp; added a referenc