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.
118795909
Singlet Majorana fermion dark matter, DAMA, CoGeNT, and CDMS-II
We propose a model where a sterile Majorana fermion with mass in the range of 10 GeV-1 TeV can account for the whole amount of dark matter in the Universe. The model involves a right-handed singlet Majorana fermion as a weakly interacting massive particle, a charged and a neutral scalar, and all singlets by the standard model symmetry and makes use of a discrete symmetry in order to guarantee the singlet fermion stability. Also, motivated by the recent results reported by CoGeNT and CDMS-II experiments concerning excess events of the expected background, and the intriguing annual modulation observed by DAMA, we look for a possible explanation to some of these experiments. Our results show that there is a lot of room in the parameter space to make this sterile Majorana fermion a viable dark matter candidate, and, if it is realized in nature, it is also capable of explaining DAMA annual modulation signal and/or CoGeNT excess events or CDMS-II excess event candidates. Besides, a light Higgs boson is preferred in this scenario.
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.
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
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.
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 $SU(10{)}_{\mathrm{TC}}$.
119480251
Generalized Chaplygin gas model, supernovae, and cosmic topology
In this work we study to which extent the knowledge of spatial topology may place constraints on the parameters of the generalized Chaplygin gas (GCG) model for unification of dark energy and dark matter. By using both the Poincar\'e dodecahedral and binary octahedral spaces as the observable spatial topologies, we examine the current type Ia supernovae (SNe Ia) constraints on the GCG model parameters. We show that the knowledge of spatial topology does provide additional constraints on the ${A}_{s}$ parameter of the GCG model but does not lift the degeneracy of the $\ensuremath{\alpha}$ parameter.
116966286
Search for a $W^\prime$ or Techni-$\rho$ Decaying into $WZ$ in $pp$ Collisions at $\sqrt{s}=7$ TeV
A search is performed in pp collisions at √s=7  TeV for exotic particles decaying via WZ to final states with electrons and muons. The data sample corresponds to an integrated luminosity of approximately 5  fb^(-1). No significant excess is observed in the data above the expected standard model background. Upper bounds at 95% confidence level are set on the production cross section of the W′ boson described by the sequential standard model and on the W′ WZ coupling. W′ bosons with masses below 1143 GeV are excluded. Limits are also set in the context of low-scale technicolor models, under a range of assumptions concerning the model parameters.
136967851
Design, Construction and Installation of the ATLAS Hadronic Barrel Scintillator-Tile Calorimeter
119113673
Better HMC integrators for dynamical simulations
We show how to improve the molecular dynamics step of Hybrid Monte Carlo, both by tuning the integrator using Poisson brackets measurements and by the use of force gradient integrators. We present results for moderate lattice sizes.
110352212
Energy reconstruction for a hadronic calorimeter using neural networks
Abstract Often calorimeters have a non-compensating response ( e / h ≠ 1 ) . Non-compensation degrades both resolution and linearity figures. To improve on this, weighting techniques are frequently applied. These techniques normally use linear combination of the energy deposited in the calorimeter cells or longitudinal samples. For the hadronic calorimeter of ATLAS, Tilecal, the use of a neural network is proposed to perform the energy reconstruction for pions, taking into account both linearity and energy resolution. Experimental data from testbeam periods were used to perform neural reconstruction.