We calculate the masses of the low-lying states with quantum numbers
J
PC
= 0
++, 1
−− in the Higgs and confinement regions of the three-dimensional SU(2) Higgs model, which plays an important rôle ...in the description of the thermodynamic properties of the standard model at finite temperatures. We extract the masses from correlation functions of gauge-invariant operators which are calculated by means of a lattice Monte Carlo simulation. The projection properties of our lattice operators onto the lowest states are greatly improved by the use of smearing techniques. We also consider cross correlations between various operators with the same quantum numbers. From these the mass eigenstates are determined by means of a variational calculation. In the symmetric phase, we find that some of the ground-state masses are about 30% lighter than those reported from previous simulations. We also obtain the masses of the first few excited states in the symmetric phase. Remarkable among these is the occurrence of a 0
++ state composed almost entirely of gauge degrees of freedom. The mass of this state, as well as that of its first excitations, is nearly identical to the corresponding glueball states in three-dimensional SU(2) pure gauge theory, indicating an approximate decoupling of the pure gauge sector from the Higgs sector of the model. We perform a detailed study of finite-size effects and extrapolate the lattice mass spectrum to the continuum.
Following the Schwinger boson representation for the su(M+1)- and the su(N,1)-algebra presented by two of the present authors (J. da P. and M. Y.) and Kuriyama, a possible counterpart of the Lipkin ...model in the su(M+1)-algebra formulated in the fermion space is presented. The free vacuum, which plays a fundamental role in the conventional treatment of the Lipkin model, is generalized in a quite natural way, and further, the excited state generating operators such as the particle-hole pairs are also given in a natural scheme. As concrete examples, the cases of the su(2)-, su(3)- and the su(4)-algebra are discussed. Especially, the case of the su(4)-algebra is investigated in detail in relation to the nucleon pairing correlations and the high temperature superconductivity.
.
We study the phenomenology of the
Z′
resonance as well as of the light and heavy Higg boson production and decay in the framework of the
S
U
(
3
)
L
⊗
U
(
1
)
N
electroweak model at future
e
+
e
-
...linear colliders, such as the ILC and CLIC. For our study we consider the processes Higgs-strahlung
e
+
e
-
→
(
Z
,
Z
)
→
Z
h
and
e
+
e
-
→
Z
→
Z
H
with both the resonant and non-resonant effects. We find that for center-of-mass energies of
s
=
500
-3000 GeV and integrated luminosities of
=
500
-2000 fb
-1
, the total number of expected
Zh
and
ZH
events can reach 76176 and 3, respectively, in the future
e
+
e
-
linear colliders. The first process is very optimistic and thus it would be possible to perform precision measurements for both the
Z′
resonance and the Higgs boson
h
. Our study complements other studies on the associated production
Zh
and
ZH
in the context of a
S
U
(
3
)
L
⊗
U
(
1
)
N
electroweak model at hadron and
e
+
e
-
colliders.
We study sterile neutrinos in an extension of the standard model, based on
the gauge group $SU(3)_C\otimes SU(3)_L\otimes SU(3)_R\otimes U(1)_N$, and use
this model to illustrate how to apply ...cosmological limits to thermalized
particles that decouple while relativistic. These neutrinos, $N_{aL}$, can be
dark matter candidates, with a keV mass range arising rather naturally in this
model. We analyse the cosmological limits imposed by $N_{eff}$ and dark matter
abundance on these neutrinos. Assuming that these neutrinos have roughly equal
masses and are not CDM, we conclude that the $N_{eff}$ experimental value can
be satisfied in some cases and the abundance constraint implies that these
neutrinos are hot dark matter. With this information, we give upper bounds on
the Yukawa coupling between the sterile neutrinos and a scalar field, the
possible values of the VEV of this scalar field and lower bounds to the mass of
one gauge boson of the model.
We consider generalizations of the standard model (SM) which are based on the
gauge symmetry $SU(n)_c\otimes SU(m)_L\otimes U(1)_N$. Although the most
interesting possibilities occur when $n=3$, we ...will consider also the cases
$n=4,5$ both with $m=3,4$. Models with left-right symmetry, horizontal
symmetries and the possible embedding in a larger group (grand unification
scenarios) are briefly discussed.
JHEP 1612 (2016) 059 We investigate a gauge extension of the Standard Model in light of the
observed hints of lepton universality violation in $b \to c \ell \nu$ and $b
\to s \ell^+ \ell^-$ decays at ...BaBar, Belle and LHCb. The model consists of an
extended gauge group $\mathrm{SU(2)}_{1} \times \mathrm{SU(2)}_{2} \times
\mathrm{U(1)}_Y$ which breaks spontaneously around the TeV scale to the
electroweak gauge group. Fermion mixing effects with vector-like fermions give
rise to potentially large new physics contributions in flavour transitions
mediated by $W^{\prime}$ and $Z^{\prime}$ bosons. This model can ease tensions
in $B$-physics data while satisfying stringent bounds from flavour physics, tau
decays, and electroweak precision data. Possible ways to test the proposed new
physics scenario with upcoming experimental measurements are discussed. Among
other predictions, the lepton flavour violating ratios $R_M$, with $M = K^*,
\phi$, are found to be reduced with respect to the Standard Model expectation
$R_M \simeq 1$.
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