241 research outputs found
Charged bilepton pair production at LHC including exotic quark contribution
AbstractThe production of W+Wâ pair in hadron colliders was calculated up to loop corrections by some authors in the Electroweak Standard Model (SM) framework. This production was also calculated, at the tree level, in some extensions of the SM such as the vector singlet, the fermion mirror fermion and the vector doublet models by considering the contributions of new neutral gauge bosons and exotic fermions. The obtained results for e+eâ and pp collisions pointed out that the new physics contributions are quite important. This motivates us to calculate the production of a more massive charged gauge boson predicted by the SU(3)CĂSU(3)LĂU(1)X model (3-3-1 model). Thus, the aim of the present paper is to analyze the role played by of the extra gauge boson ZâČ and of the exotic quarks, predicted in the minimal version of the 3-3-1 model, by considering the inclusive production of a pair of bileptons (V±) in the reaction p+pâV++Vâ+X, at the Large Hadron Collider (LHC) energies.Our results show that the correct energy behavior of the elementary cross section follows from the balance between the contributions of the extra neutral gauge boson with those from the exotic quarks. The extra neutral gauge boson induces flavor-changing neutral currents (FCNC) at tree level, and we have introduced the ordinary quark mixing matrices for the model when the first family transforms differently to the other two with respect to SU(3)L. We obtain a huge number of heavy bilepton pairs produced for two different values of the center of mass energy of the LHC
Single neutral heavy lepton production at electron-muon colliders
New heavy Majorana and Dirac neutrinos production at future electron-muon
colliders are investigated. The production of a single heavy neutrino is shown
to be more relevant than pair production when comparing cross sections and
neutrino mass ranges. The process is studied including on-shell and off-shell heavy neutrino
effects. Distributions are calculated including hadronization effects and
experimental cuts that suppress background, in order to have a clear signal for
heavy neutral leptons.Comment: 4 pages, 14 jpg figures, Published Phys.Lett B494 (2000) 273-27
Searching for an Extra Neutral Gauge Boson from Muon Pair Production at LHC
We search for signatures of the extra neutral gauge boson ,
predicted in some extensions of the Standard Model, from the analysis of some
distributions for , where the only
exotic particle involved is . In addition to the invariant mass and
charge asymmetry distributions, we propose in our search to use the transverse
momentum distribution () as an observable. We do our calculation for two
values of the LHC center of mass energy (7 and 14 TeV), corresponding to 1 and
100 fb of luminosity, in order to compare our findings from some models
with the distributions following from the Standard Model. By applying
convenient cuts in the invariant mass, we show that the final particles
distributions can reveal the presence of an extra neutral gauge boson
contribution. We also claim that it is possible to disentangle the models
considered here and we emphasize that the minimal version of the model, based
on symmetry, presents the more
clear signatures for existence.Comment: 13 pages, 15 figures, 3 tables
Spontaneous parity violation and minimal Higgs models
In this paper we present a model for the spontaneous breaking of parity with
two Higgs doublets and two neutral Higgs singlets which are even and odd under
D-parity. The condition can be satisfied without introducing
bidoublets and it is induced by the breaking of D-parity through the vacuum
expectation value of the odd Higgs singlet. Examples of left-right symmetric
and mirror fermions models in grand unified theories are presented.Comment: Revised version. Accepted in Eur. Phys. Journal
Pair production of the heavy leptons in future high energy linear e^{+}e^{-} colliders
The littlest Higgs model with T-parity predicts the existence of the T-odd
particles, which can only be produced in pair. We consider pair production of
the T-odd leptons in future high energy linear collider ().
Our numerical results show that, as long as the T-odd leptons are not too
heavy, they can be copiously produced and their possible signals might be
detected via the processes in future
experiments.Comment: Discussions added, typos and references correcte
Same-sign dileptons as a signature for heavy Majorana neutrinos in hadron-hadron collisions
We discuss the possibility of same-sign dileptons as a signature for Majorana
neutrinos. The production mechanism is given by a single heavy neutrino
production and decay proton-proton -> l^{\pm} N X -> l^{\pm} l^{\pm} X'. Cross
section and distributions are presented for the LHC energies.Comment: 07 pages, LaTeX; to be published in Physics Letters
Generating Neutrino Mass in the 331 Model
A mechanism for generating small tree-level Majorana mass for neutrinos is
implemented in the 331 Model. No additional fermions or scalars need to be
added, and no mass scale greater than a few TeV is invoked.Comment: LaTex, 7 pages, no figures. Revised version to appear in Phys. Rev.
Seesaw tau lepton mass and calculable neutrino masses in a 3-3-1 model
In a version of the 3-3-1 model proposed by Duong and Ma the introduction of
the scalar sextet for giving mass to the charged leptons is avoided by adding a
singlet charged lepton. We show that in this case the lepton gains mass
through a seesaw--like mechanism. Besides we show how to generate neutrino
masses at the tree and at the 1-loop level with the respective
Maki-Nakagawa-Sakata leptonic mixing matrices.Comment: revtex, 5 pages and one eps figure. Published versio
Input of sugarcane post-harvest residues into the soil
Sugarcane (Saccharum spp.) crops provide carbon (C) for soil through straw and root system decomposition. Recently, however, sugarcane producers are considering straw to be removed for electricity or second generation ethanol production. To elucidate the role of straw and root system on the carbon supply into the soil, the biomass inputs from sugarcane straw (tops and dry leaves) and from root system (rhizomes and roots) were quantified, and its contribution to provide C to the soil was estimated. Three trials were carried out in the State of Sao Paulo, Brazil, from 2006 to 2009. All sites were cultivated with the variety SP81 3250 under the green sugarcane harvest. Yearly, post-harvest sugarcane residues (tops, dry leaves, roots and rhizomes) were sampled; weighted and dried for the dry mass (DM) production to be estimated. On average, DM root system production was 4.6 Mg ha-1 year-1 (1.5 Mg C ha-1 year-1) and 11.5 Mg ha-1 year-1 (5.1 Mg C ha-1 year-1) of straw. In plant cane, 35 % of the total sugarcane DM was allocated into the root system, declining to 20 % in the third ratoon. The estimate of potential allocation of sugarcane residues to soil organic C was 1.1 t ha-1 year-1; out of which 33 % was from root system and 67 % from straw. The participation of root system should be higher if soil layer is evaluated, a deeper soil layer, if root exudates are accounted and if the period of higher production of roots is considered
Search for new phenomena in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in âs=13 TeV pp collisions with the ATLAS detector
Two searches for new phenomena in final states containing a same-flavour opposite-sign lepton (electron or muon) pair, jets, and large missing transverse momentum are presented. These searches make use of protonâproton collision data, collected during 2015 and 2016 at a centre-of-mass energy s=13 TeV by the ATLAS detector at the large hadron collider, which correspond to an integrated luminosity of 14.7fb-1. Both searches target the pair production of supersymmetric particles, squarks or gluinos, which decay to final states containing a same-flavour opposite-sign lepton pair via one of two mechanisms: a leptonically decaying Z boson in the final state, leading to a peak in the dilepton invariant-mass distribution around the Z boson mass; and decays of neutralinos (e.g. Ï~20ââ+â-Ï~10), yielding a kinematic endpoint in the dilepton invariant-mass spectrum. The data are found to be consistent with the Standard Model expectation. Results are interpreted in simplified models of gluino-pair (squark-pair) production, and provide sensitivity to gluinos (squarks) with masses as large as 1.70 TeV (980 GeV)
- âŠ