18290847
Electric charge quantization and the muon anomalous magnetic moment
We investigate some proposals to solve the electric charge quantization puzzle that simultaneously explain the recent measured deviation on the muon anomalous magnetic moment. For this we assess extensions of the electro-weak standard model spanning modifications on the scalar sector only. It is interesting to verify that one can have modest extensions which easily account for the solution for both problems.
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.
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 $SU(10{)}_{\mathrm{TC}}$.
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.
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.
4687303
Measurement of pion and proton response and longitudinal shower profiles up to 20 nuclear interaction lengths with the ATLAS Tile calorimeter
The response of pions and protons in the energy range of 20–180 GeV, produced at CERN's SPS H8 test-beam line in the ATLAS iron–scintillator Tile hadron calorimeter, has been measured. The test-beam configuration allowed the measurement of the longitudinal shower development for pions and protons up to 20 nuclear interaction lengths. It was found that pions penetrate deeper in the calorimeter than protons. However, protons induce showers that are wider laterally to the direction of the impinging particle. Including the measured total energy response, the pion-to-proton energy ratio and the resolution, all observations are consistent with a higher electromagnetic energy fraction in pion-induced showers. The data are compared with GEANT4 simulations using several hadronic physics lists. The measured longitudinal shower profiles are described by an analytical shower parametrization within an accuracy of 5–10%. The amount of energy leaking out behind the calorimeter is determined and parametrized as a function of the beam energy and the calorimeter depth. This allows for a leakage correction of test-beam results in the standard projective geometry.
120562248
Test beam operation of the CMS calorimeter trigger synchronization boards
The CMS experiment uses information from its electromagnetic and hadronic calorimeters and muon detectors to decide whether to read out the whole detector. For such a task to be successful, all trigger primitives pushed through the trigger decision tree must be flawlessly aligned in time for operation at 40 MHz. Both calorimeters in CMS use the Synchronization Link Board for this purpose. In this article we report on the test results of this board using the bunched beams available in the H4 electron beam line at CERN.
209834712
Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the standard model with the ATLAS detector
An inclusive search for anomalous production of two prompt, isolated muons with the same electric charge is presented. The search is performed in a data sample corresponding to 1.6 fb(-1) of integr ...
53471633
Kallen-Lehmann spectroscopy for (un)physical degrees of freedom
We consider the problem of "measuring" the Kallen-Lehmann spectral density of a particle (be it elementary or bound state) propagator by means of 4D lattice data. As the latter are obtained from operations at (Euclidean momentum squared) p(2) >= 0, we are facing the generically ill-posed problem of converting a limited data set over the positive real axis to an integral representation, extending over the whole complex p2 plane. We employ a linear regularization strategy, commonly known as the Tikhonov method with the Morozov discrepancy principle, with suitable adaptations to realistic data, e. g. with an unknown threshold. An important virtue over the (standard) maximum entropy method is the possibility to also probe unphysical spectral densities, for example, of a confined gluon. We apply our proposal here to "physical" mock spectral data as a litmus test and then to the lattice SU(3) Landau gauge gluon at zero temperature.
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.