Search results for "SCALAR"
showing 10 items of 1002 documents
Charge Breaking Minima in the Broken R-parity Minimal Supersymmetric Standard Model
2005
We reconsider the possible presence of charge and colour breaking minima in the scalar potential of the minimal supersymmetric standard model (MSSM) and its minimal generalization with R-parity explicitly broken by bilinear terms (RMSSM). First we generalize some results previously derived for the MSSM case. Next we investigate how robust is the MSSM against its RMSSM extension. We examine the constraints on the RMSSM parameter space that follow from the required absence of charge breaking minima in the scalar potential. We point out the possibility of generating non--zero vacuum expectation values for the charged Higgs field which is not present in the MSSM. However, given the smallness of…
Possible lepton universality breaking in Upsilon decays: a light CP-odd Higgs interpretation and consequences
2011
A light CP-odd Higgs boson mixing with η b hadronic resonances can show up by inducing a slight but observable lepton universality breaking in Upsilon decays. Besides, hyperfine splittings m ϒ ( n S ) − m η b ( n S ) might also be sensitive to the mixing providing another hint of the existence of such a light pseudoscalar Higgs. On the other hand, recent findings from astroparticle and cosmology favouring a light dark matter constituent (with mass about 10 GeV or less) cast a new interest into the search for invisible decays of ϒ resonances performed at B factories.
5D perspective on Higgs production at the boundary of a warped extra dimension
2014
A comprehensive, five-dimensional calculation of Higgs-boson production in gluon fusion is performed for both the minimal and the custodially protected Randall-Sundrum (RS) model, with Standard Model fields propagating in the bulk and the scalar sector confined on or near the IR brane. For the first time, an exact expression for the gg->h amplitude in terms of the five-dimensional fermion propagator is derived, which includes the full dependence on the Higgs-boson mass. Various results in the literature are reconciled and shown to correspond to different incarnations of the RS model, in which the Higgs field is either localized on the IR brane or is described in terms of a narrow bulk st…
Bounds on a light scalar in two-Higgs-doublet models
1992
22 páginas, 4 figuras.
Yukawa unified supersymmetricSO(10)model: Cosmology, rare decays, and collider searches
2000
It has recently been pointed out that viable sparticle mass spectra can be generated in Yukawa unified SO(10) supersymmetric grand unified models consistent with radiative breaking of electroweak symmetry. Model solutions are obtained only if $\tan\beta \sim 50$, $\mu <0$ and positive $D$-term contributions to scalar masses from SO(10) gauge symmetry breaking are used. In this paper, we attempt to systematize the parameter space regions where solutions are obtained. We go on to calculate the relic density of neutralinos as a function of parameter space. No regions of the parameter space explored were actually cosmologically excluded, and very reasonable relic densities were found in much of…
SU(6) Extension of the Weinberg-Tomozawa Meson-Baryon Lagrangian
2005
A consistent SU(6) extension of the Weinberg-Tomozawa meson-baryon chiral Lagrangian is constructed which incorporates vector meson and baryon decuplet degrees of freedom. The corresponding Bethe-Salpeter approximation predicts the existence of an isoscalar spin-parity ${3/2}^-$ $K^*N$ bound state (strangeness +1) with a mass around 1.7--1.8$ $GeV. It is the highest hypercharge state of an antidecuplet SU(3) representation and it is unstable through $K^*$ decay. The estimated width of this state (neglecting d-wave $KN$ decay) turns out to be small ($\Gamma \le 15 $MeV). Clear signals of this resonance would be found in reactions like $\gamma p \to {\bar K}^0 p K^+ \pi^-$ by looking at the t…
Isoscalar Roper(N1440*)excitation in thepp→ppπ0reaction close to threshold
1999
A new mechanism for the $p\stackrel{\ensuremath{\rightarrow}}{p}\mathrm{pp}{\ensuremath{\pi}}^{0}$ reaction close to threshold is suggested coming from the isoscalar excitation of the Roper and its decay into $N(\ensuremath{\pi}\ensuremath{\pi}{)}_{s\ensuremath{-}\mathrm{w}\mathrm{a}\mathrm{v}\mathrm{e}},$ with one of the ${\ensuremath{\pi}}^{0}$ emitted and the other one reabsorbed on the second nucleon. We show that this new mechanism can lead to important interference with other mechanisms suggested so far.
Scalar isoscalar pion pairs in nuclei and theA(π,ππ)Xreaction
1999
The reaction A(pi,pi pi)X has been studied at low energies, paying particular attention to the interaction of the two final pions in the scalar isoscalar (I=J=0) channel. We have developed a microscopic model for the pion production, and then implemented the two pion final state interaction by using the results of a non-perturbative unitary coupled-channels method based in the standard chiral Lagrangians. The resulting model, describes well the reaction on the nucleon for all different isospin channels. Finally, we have considered the reaction in nuclei. Our calculation takes into account Fermi motion, Pauli blocking, pion absorption, and also the strong modification of the pi-pi interactio…
Chiral symmetry amplitudes in the s-wave isoscalar and isovector channels and the $\sigma, f_0(980), a_0 (980)$ scalar mesons
1996
We use a nonpertubative approach which combines coupled channel Lippmann Schwinger equations with meson-meson potentials provided by the lowest order chiral Lagrangian. By means of one parameter, a cut off in the momentum of the loop integrals, which results of the order of 1 GeV, we obtain singularities in the S-wave amplitudes corresponding to the $\sigma$, f_0 and a_0 resonances. The $\pi \pi \to \pi \pi, \pi \pi \to K \bar{K}$ phase shifts and inelasticities in the T = 0 scalar channel are well reproduced as well as the $\pi^0 \eta$ and $K \bar{K}$ mass distributions in the T = 1 channel. Furthermore, the total and partial decay widths of the f_0 and a_0 resonances are properly reproduc…
Search for invisible Higgs boson decays in vector boson fusion at s=13TeV with the ATLAS detector
2019
We report a search for Higgs bosons that are produced via vector boson fusion and subsequently decay into invisible particles. The experimental signature is an energetic jet pair with invariant mass of O(1)TeV and O(100)GeV missing transverse momentum. The analysis uses 36.1 fb −1 of pp collision data at s=13TeV recorded by the ATLAS detector at the LHC. In the signal region the 2252 observed events are consistent with the background estimation. Assuming a 125GeV scalar particle with Standard Model cross sections, the upper limit on the branching fraction of the Higgs boson decay into invisible particles is 0.37 at 95% confidence level where 0.28 was expected. This limit is interpreted in H…