15370402
Minimal 3-3-1 model, lepton mixing and muonium-antimuonium conversion
The recent experimental results on neutrino oscillation and on muonium–antimuonium conversion require extension of the minimal 3-3-1 model. We review the constraints imposed on the model by these measurements and suggest a pattern of leptonic mixing, with charged leptons in a non-diagonal basis, which accounts for the neutrino physics and circumvents the tight muonium–antimuonium bounds on the model. We also illustrate a scenario where this pattern could be realized.
15081043
Fixed points and vacuum energy of dynamically broken gauge theories
We show that if a gauge theory with dynamical symmetry breaking has nontrivial fixed points, they will correspond to extrema of the vacuum energy. This relationship provides a different method to determine fixed points.
17425135
Scalar Bilepton Dark Matter
In this work we show that 3-3-1 model with right-handed neutrinos has a natural weakly interacting massive particle (WIMP) dark matter candidate. It is a complex scalar with mass of order of some hundreds of GeV which carries two units of lepton number, a scalar bilepton. This makes it a very peculiar WIMP, very distinct from supersymmetric or extra-dimension candidates. Besides, although we have to make some reasonable assumptions concerning the several parameters in the model, no fine tuning is required in order to get the correct dark matter abundance. We also analyze the prospects for WIMP direct detection by considering recent and projected sensitivities for WIMP–nucleon elastic cross section from CDMS and XENON collaborations.
14228967
Bounds on the simplest little Higgs model mass spectrum through Z leptonic decay
We derive the leptonic neutral current in the simplest little Higgs model and compute the contribution of the model to the decay width $Z\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$. Using the precision electroweak data we obtain a strong lower bound $f\ensuremath{\ge}5.6\text{ }\text{ }\mathrm{TeV}$ at 95% C.L. on the characteristic energy scale of the model. It results in a lower bound for the new gauge bosons ${W}^{\ensuremath{'}\ifmmode\pm\else\textpm\fi{}}$ and ${Z}^{\ensuremath{'}}$ as being ${M}_{{W}^{\ensuremath{'}\ifmmode\pm\else\textpm\fi{}}}\ensuremath{\ge}2.6\text{ }\text{ }\mathrm{TeV}$ and ${M}_{{Z}^{\ensuremath{'}}}\ensuremath{\ge}3.1\text{ }\text{ }\mathrm{TeV}$, respectively. We also present the allowed values of the $k={f}_{1}/{f}_{2}$ which is the parameter relating the two vacuum expectation values of the scalar triplets in the model, and the $\ensuremath{\mu}$ parameter of a quadratic term, involving the triplets, necessary to provide an acceptable mass range for the standard Higgs boson.
119039027
Spontaneous CP violation in the 3-3-1 model with right-handed neutrinos
complex VEV's in the respective model. Obtain the con- straint equations on the phases which come from the minimum condition of the scalar potential. Check how many phases the gauge transformation can eliminate. Finally, wherever it is possible, redefine the fields as to absorb the remaining phases. If, in the end, at least one phase survives, then the SCPV mechanism works in the model considered. In this work we implement the SCPV mechanism in the SU� 3� CSU� 3� LU� 1� N (3-3-1) gauge model for the electroweak and strong interactions that possess right- handed neutrinos composing the fundamental representa- tion (6). The SCPV was already considered in other ver- sions of the 3-3-1 models (7,8). In general all the 3-3-1 models require at least three scalar triplets in order to generate the correct particle masses of the model. Considering that each scalar triplet involves at least one neutral scalar, we are going to have at least three phases when no complex coupling is assumed. Nevertheless, the SU� 3� LU� 1� N symmetry allows us to eliminate two of these phases and, certainly, the minimum condition of the scalar potential of the model will provide an additional constraint over the phases. Thus, it is expected that, in the case of three triplets and three phases, the gauge symmetry and the minimum constraint lead to a trivial solution, i.e., that these three phases can be washed out of the model. It was shown in Ref. (7) that this kind of 3-3-1 model requires three triplets and one scalar sextet in order for SCPV to be implemented. The minimal 3-3-1 model with right-handed neutrinos also requires only three scalar triplets to generate the needed masses. What motivates our investigation of the SCPV in this model is that its scalar sector differs from the other models in a subtle aspect. Two of its three scalar triplets possess each one two neutral scalars. Thus, in this model, we dispose from the beginning of a total of five neutral scalars. When we assume that all of them develop complex VEV's, five phases appear in the model. We will show that in this scenario one phase still survives the gauge transformation, the constraints for the minimum of the
56306636
Light composite Higgs from an effective action for technicolor
We compute an effective action for a composite Higgs boson formed by new fermions belonging to a general technicolor non-Abelian gauge theory, using a quite general expression for the fermionic self-energy that depends on a certain parameter ($\ensuremath{\alpha}$), that defines the technicolor theory from the extreme walking behavior up to the one with a standard operator product expansion behavior. We discuss the values of the trilinear and quadrilinear scalar couplings. Our calculation spans all the possible physical possibilities for mass and couplings of the composite system. In the case of extreme walking technicolor theories we verify that it is possible to have a composite Higgs boson with a mass as light as the present experimental limit, contrary to the usual expectation of a heavy mass for the composite Higgs boson. In this case we obtain an upper limit for the Higgs boson mass, (${M}_{H}\ensuremath{\le}\mathcal{O}(700)\text{ }\text{ }\mathrm{GeV}$ for $SU(2{)}_{\mathrm{TC}}$), and the experimental data on the Higgs boson mass constrain $SU(N{)}_{\mathrm{TC}}$ technicolor gauge groups to be smaller than $SU(10{)}_{\mathrm{TC}}$.
118857116
Recent results on Top quark Physics with the ATLAS and CMS experiments
An overview of the most recent results on top quark physics obtained using proton-proton collision data collected with the ATLAS and the CMS experiments at 7 TeV center-of-mass energy is given. Measurements for inclusive and differential top quark pair or single top quark production in different final states are reviewed. Top properties such as W helicity in top decays, electric charge, charge asymmetry and spin correlations of top quark pairs, among others have also been measured by the LHC experiments. All the measurements are found to be consistent with the Standard Model predictions with a good level of accuracy. The latest results in the measurement of the top quark mass at the LHC are also presented and discussed.
209835691
Search for pair production of first- and second-generation scalar leptoquarks in pp collisions at sqrt(s)= 7 TeV
Results are presented from a search for the pair production of first- and second-generation scalar leptoquarks in proton-proton collisions at sqrt(s)= 7 TeV. The data sample corresponds to an integrated luminosity of 5.0 inverse femtobarns, collected by the CMS detector at the LHC. The search signatures involve either two charged leptons of the same-flavour (electrons or muons) and at least two jets, or a single charged lepton (electron or muon), missing transverse energy, and at least two jets. If the branching fraction of the leptoquark decay into a charged lepton and a quark is assumed to be beta=1, leptoquark pair production is excluded at the 95% confidence level for masses below 830 GeV and 840 GeV for the first and second generations, respectively. For beta = 0.5, masses below 640 GeV and 650 GeV are excluded. These limits are the most stringent to date.
124334218
Search for new physics in final states with a lepton and missing transverse energy in pp collisions at the LHC
This Letter describes the search for an enhanced production rate of events with a charged lepton and a neutrino in high-energy pp collisions at the LHC. The analysis uses data collected with the CMS detector, with an integrated luminosity of 5.0  fb-1 at √s=7  TeV, and a further 3.7  fb-1 at √s=8  TeV. No evidence is found for an excess. The results are interpreted in terms of limits on a heavy charged gauge boson (W′) in the sequential standard model, a split universal extra dimension model, and contact interactions in the helicity-nonconserving model. For the last, values of the binding energy below 10.5 (8.8) TeV in the electron (muon) channel are excluded at a 95% confidence level. Interpreting the lν final state in terms of a heavy W′ with standard model couplings, masses below 2.90 TeV are excluded.
209999944
Just how different are SU(2) and SU(3) Landau propagators in the IR regime
The infrared behavior of gluon and ghost propagators in Yang-Mills theories is of central importance for understanding quark and gluon confinement in QCD. While simulations of pure SU(3) gauge theory correspond to the physical case in the limit of infinite quark mass, the SU(2) case (i.e. pure two-color QCD) is usually employed as a simplification, in the hope that qualitative features be the same as for the SU(3) case. Here we carry out the first comparative study of lattice (Landau) propagators for these two gauge groups. Our data were especially produced with equivalent lattice parameters in order to allow a careful comparison of the two cases. We find very good agreement between SU(2) ans SU(3) propagators, showing that in the IR limit the equivalence of the two cases is quantitative. Our results seem to confirm the prediction from Schwinger-Dyson equations that the infrared exponents are independent of the gauge group SU(N_c).
119020741
Studying the infrared behaviour of gluon and ghost propagators using large asymmetric lattices
We report on the infrared limit of the quenched lattice Landau gauge gluon propagator computed from large asymmetric lattices. In particular, the compatibility of the pure power law infrared solution (q2)2κ of the Dyson‐Schwinger equations is investigated and the exponent κ is measured. Some results for the ghost propagator and for the running coupling constant will also be shown.