Search results for " symmetry"
showing 10 items of 701 documents
Mirror symmetry at high spin in51Feand51Mn
2000
Gamma decays from excited states in the ${T}_{z}=\ensuremath{-}\frac{1}{2}$ nucleus ${}^{51}$Fe have been observed for the first time. The differences in excitation energies as compared with those of the mirror partner, ${}^{51}$Mn, have been interpreted in terms of Coulomb effects and the resulting Coulomb energy differences (CED) can be understood intuitively in terms of particle-alignment effects. A new CED effect has been observed, in which different CED trends have been measured for each signature of the rotational structures that characterize these mid-${f}_{7/2}$ shell nuclei. Large-scale $\mathrm{fp}$-shell model calculations have been used to compute the trends of the CED as a func…
Unifying left–right symmetry and 331 electroweak theories
2017
We propose a realistic theory based on the $\mathrm{SU(3)_c \otimes SU(3)_L \otimes SU(3)_R \otimes U(1)_{X}}$ gauge group which requires the number of families to match the number of colors. In the simplest realization neutrino masses arise from the canonical seesaw mechanism and their smallness correlates with the observed V-A nature of the weak force. Depending on the symmetry breaking path to the Standard Model one recovers either a left-right symmetric theory or one based on the $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)}$ symmetry as the "next" step towards new physics.
One-loop calculation of the oblique S parameter in higgsless electroweak models
2012
We present a one-loop calculation of the oblique S parameter within Higgsless models of electroweak symmetry breaking and analyze the phenomenological implications of the available electroweak precision data. We use the most general effective Lagrangian with at most two derivatives, implementing the chiral symmetry breaking SU(2)_L x SU(2)_R -> SU(2)_{L+R} with Goldstones, gauge bosons and one multiplet of vector and axial-vector massive resonance states. Using the dispersive representation of Peskin and Takeuchi and imposing the short-distance constraints dictated by the operator product expansion, we obtain S at the NLO in terms of a few resonance parameters. In asymptotically-free gauge …
Left-right symmetry breaking in NJL approach
1995
We study left-right symmetric models which contain only fermion and gauge boson fields and no elementary scalars. The Higgs bosons are generated dynamically through a set of gauge- and parity-invariant 4-fermion operators. It is shown that in a model with a composite bi-doublet and two triplet scalars there is no parity breaking at low energies, whereas in the model with two doublets instead of two triplets parity is broken automatically regardless of the choice of the parameters of the model. For phenomenologically allowed values of the right-handed scale a tumbling symmetry breaking mechanism is realized in which parity breaking at a high scale $\mu_R$ propagates down and eventually cause…
Measurement of trilinear gauge boson couplings fromWW+WZ→lνjjevents inpp¯collisions ats=1.96 TeV
2009
We present a direct measurement of trilinear gauge boson couplings at gamma WW and ZWW vertices inWW and WZ events produced in p (p) over bar collisions at root s = 1:96 TeV. We consider events with one electron or muon, missing transverse energy, and at least two jets. The data were collected using the D0 detector and correspond to 1:1 fb(-1) of integrated luminosity. Considering two different relations between the couplings at the gamma WW and ZWW vertices, we measure these couplings at 68% C.L. to be kappa(gamma) = 1.07(-0.29)(+0.26) lambda = 0.00(-0.06)(+0.00), and g(1)(Z) = 1.04(-0.09)(+0.09) in a scenario respecting SU(2)(L) circle times U(1)(Y) gauge symmetry and kappa = 1.04(-0.11)(…
Fading of symmetry nonrestoration at finite temperature
1998
The fate of symmetries at high temperature determines the dynamics of the very early universe. It is conceivable that temperature effects favor symmetry breaking instead of restoration. Concerning global symmetries, the non-linear sigma model is analyzed in detail. For spontaneously broken gauge symmetries, we propose the gauge boson magnetic mass as a ``flag'' for symmetry (non)-restoration. We consider several cases: the standard model with one and two Higgs doublets in the perturbative regime, and the case of a strongly interacting Higgs sector. The latter is done in a model independent way with the tools provided by chiral Lagrangians. Our results clearly point towards restoration, a pa…
GAUGE-HIGGS UNIFICATION MODELS WITH COSET SPACE DIMENSIONAL REDUCTION SCHEME
2009
We investigate the gauge-Higgs unification models within the scheme of the coset space dimensional reduction, beginning with two types of set up; fourteen-dimensional gauge theory with simple gauge groups and ten-dimensional gauge theory with direct product gauge groups. We found some phenomenologically acceptable models through an exhaustive search for the candidates of the coset spaces, the gauge group in higher dimension, and fermion representation.
Isospin-invariant Skyrme energy-density-functional approach with axial symmetry
2014
We develop the isospin-invariant Skyrme-EDF method by considering local densities in all possible isospin channels and proton-neutron (p-n) mixing terms as mandated by the isospin symmetry. The EDF employed has the most general form that depends quadratically on the isoscalar and isovector densities. We test and benchmark the resulting p-n EDF approach, and study the general properties of the new scheme by means of the cranking in the isospin space. We extend the existing axial DFT solver HFBTHO to the case of isospin-invariant EDF approach with all possible p-n mixing terms. Explicit expressions have been derived for all the densities and potentials that appear in the isospin representatio…
Probing new physics by comparing solar and KamLAND data
2004
We explore whether KamLAND and solar data may end up inconsistent when analyzed in terms of two-flavor neutrino oscillations. If this turned out to be the case, one would be led to conclude that there is more new physics, besides neutrino masses and mixing, in the leptonic sector. On the other hand, given that KamLAND and solar data currently agree when analyzed in terms of two-flavor neutrino oscillations, one is able to place nontrivial bounds on several manifestations of new physics. In particular, we compute how well a combined KamLAND and solar data analysis is able to constrain a specific form of violation of CPT invariance by placing a very stringent upper bound, |Delta m^2 - Delta b…
A theory for scotogenic dark matter stabilised by residual gauge symmetry
2020
Dark matter stability can result from a residual matter-parity symmetry, following naturally from the spontaneous breaking of the gauge symmetry. Here we explore this idea in the context of the $\mathrm{SU(3)_c \otimes SU(3)_L \otimes U(1)_X \otimes U(1)_{N}}$ electroweak extension of the standard model. The key feature of our new scotogenic dark matter theory is the use of a triplet scalar boson with anti-symmetric Yukawa couplings. This naturally implies that one of the light neutrinos is massless and, as a result, there is a lower bound for the $\rm 0\nu\beta\beta$ decay rate.