40594950
On the use of the reciprocal basis in neutral meson mixing
In the presence of CP violation, the effective Hamiltonian matrix describing a neutral meson anti-meson system does not commute with its hermitian conjugate. As a result, this matrix cannot be diagonalized by a unitary transformation and one needs to introduce a reciprocal basis. Although known, this fact is seldom discussed and almost never used. Here, we use this concept to highlight a parameterization of the Hamiltonian matrix in terms of physical observables, and we show that using it reduces a number of long and tedious derivations into simple matrix multiplications. These results have a straightforward application for propagation in matter. We also comment on the (mathematical) relation with neutrino oscillations.
119445110
The Use of early data on $B \to \rho \pi$ decays
This paper reviews the Dalitz plot analysis for the decays $B^0(\bar B^0) \to \rho \pi \to \pi^+ \pi^- \pi^0$. We discuss what can be learned about the ten parameters in this analysis from untagged and from tagged time-integrated data. We find that, with the important exception of the interesting CP violating quantity $\alpha$, the parameters can be determined from this data sample -- and, hence, they can be measured at CLEO as well as at the asymmetric $B$ factories. This suggests that the extraction of $\alpha$ from the time-dependent data sample can be accomplished with a smaller data sample (and, therefore, sooner) than would be required if all ten parameters were to be obtained from that time-dependent data sample alone. We also explore bounds on the shift of the true angle $\alpha$ from the angle measured from charged $\rho$ final states alone. These may be obtained prior to measurements of the parameters describing the neutral $\rho$ channel, which are expected to be small.
14931156
ProbingCPviolation with time integrated decay rates into non-CPeigenstates
Many of the experiments proposed to look for interference CP violation in neutral B mesons concentrate on tagged decay into CP eigenstates. Aleksan, Dunietz, Kayser and Le Diberder have shown that one can also look for interference CP violation using tagged decays into non-CP eigenstates. In all these methods, one must trace the time dependence of the decays. In this article we discuss a new method to search for interference CP violation by using only time integrated rates into non-CP eigenstates. The method hinges on the comparison between the decays of $\Upsilon(4S)$ into $f f$, $\bar{f} \bar{f}$, and $f \bar{f}$, and also uses the rates for $l^+ f$ and $l^- f$. This method does not depend on how the $\Upsilon(4S)$ is produced; provided enough statistics, one can use both symmetric and asymmetric colliders.
10678678
Decoupling or nondecoupling: Is that the R($b$) question?
The top quark is well known for the nondecoupling effects it implies in ρ and Rb. The recent experimental Rb data exhibits a disagreement with the SM prediction at more than the 3σ level. It is tempting to explore whether this might be due to nondecoupling New Physics effects, opposite to those of the top. We investigate this issue in the context of models with an extra family of right or left handed, singlet or doublet quarks. It is shown that, contrary to what
118851665
Implications of the Possibility that sin(2 beta) is Small
Recently, the Babar and Belle collaborations have reported their first measurements of the CP-violating asymmetry in B{sub d} {yields} {psi}K{sub S}, and more precise results will follow soon. We discuss what a future evidence for small sin2{beta} could mean, contrasting the usual possibility of new physics in the B{sub d} system, with the interesting alternative that the new physics effects are confined to the kaon system.
119183302
CP properties of symmetry-constrained two-Higgs-doublet models
The two-Higgs-doublet model can be constrained by imposing Higgs-family symmetries and/or generalized CP symmetries. It is known that there are only six independent classes of such symmetry-constrained models. We study the CP properties of all cases in the bilinear formalism. An exact symmetry implies CP conservation. We show that soft breaking of the symmetry can lead to spontaneous CP violation (CPV) in three of the classes.
119160891
Black string corrections in variable tension braneworld scenarios
Braneworld models with variable tension are investigated, and the corrections on the black string horizon along the extra dimension are provided. Such corrections are encrypted in additional terms involving the covariant derivatives of the variable tension on the brane, providing profound consequences concerning the black string horizon variation along the extra dimension, near the brane. The black string horizon behavior is shown to be drastically modified by the terms corrected by the brane variable tension. In particular, a model motivated by the phenomenological interesting case regarding Eotvos branes is investigated. It forthwith provides further physical features regarding variable tension braneworld scenarios, heretofore concealed in all previous analysis in the literature. All precedent analysis considered uniquely the expansion of the metric up to the second order along the extra dimension, which is able to evince solely the brane variable tension absolute value. Notwithstanding, the expansion terms aftermath, further accomplished in this paper from the third order on, elicits the successive covariant derivatives of the brane variable tension, and their respective coupling with the extrinsic curvature, the Weyl tensor, and the Riemann and Ricci tensors, as well as the scalar curvature. Such additional terms are shown to provide sudden modifications in the black string horizon in a variable tension braneworld scenario. Braneworld models perform a distinct branch of high- energy physics. Several of the main ideas concerning such models were inspired in formal advances in string theory (1). It is possible to delineate the precursory works dealing with the possibility of a braneworld universe (2), and nowadays there is a great variety of alternative models dealing with several aspects regarding braneworlds. Motivated by a comprehensive program regarding gravity and black strings on braneworld scenarios, and subsequent generalizations probing extra-dimensional features (3-10), some gravitational aspects concerning black strings, aris- ing from braneworld models with variable brane tension, are introduced and widely investigated. In order to analyze a conceivable gravitational effect, arising genuinely from the brane variable tension, we analyze the corrections on the black string time-dependent horizon, in such a sce- nario. This formalism provides manageable models and their possible ramifications into some aspects of gravity in this context, cognizable corrections, and physical effects as well. Besides the black string behavior being sharply modified by the variable tension brane localized at y ¼ 0 (the extra dimension is denoted by y), unexpected addi- tional terms in a Taylor expansion of the metric along the extra dimension are elicited. This Taylor expansion regards the black string horizon behavior along the extra dimen- sion. Taking into account a variable tension brane, this expansion involves the covariant derivatives of the brane tension—besides its Lie derivative along the extra dimen- sion likewise. Such expansion, for instance, was used in (11) to investigate the gravitational collapse of compact objects in braneworld scenarios.
119241024
PAMELA and FERMI limits on the neutralino-chargino mass degeneracy
Searches for Dark Matter (DM) particles with indirect detection techniques have reached important milestones with the precise measurements of the anti-proton () and gamma-ray spectra, notably by the PAMELA and FERMI-LAT experiments. While the γ-ray results have been used to test the thermal Dark Matter hypothesis and constrain the Dark Matter annihilation cross section into Standard Model (SM) particles, the anti-proton flux measured by the PAMELA experiment remains relatively unexploited. Here we show that the latter can be used to set a constraint on the neutralino-chargino mass difference. To illustrate our point we use a Supersymmetric model in which the gauginos are light, the sfermions are heavy and the Lightest Supersymmetric Particle (LSP) is the neutralino. In this framework the W+W− production is expected to be significant, thus leading to large and γ-ray fluxes. After determining a generic limit on the Dark Matter pair annihilation cross section into W+W− from the data only, we show that one can constrain scenarios in which the neutralino-chargino mass difference is as large as 20 GeV for a mixed neutralino (and intermediate choices of the propagation scheme). This result is consistent with the limit obtained by using the FERMI-LAT data. As a result, we can safely rule out the pure wino neutralino hypothesis if it is lighter than 450 GeV and constitutes all the Dark Matter.
119136375
Unfolding physics from the algebraic classification of spinor fields
Abstract After reviewing the Lounesto spinor field classification, according to the bilinear covariants associated to a spinor field, we call attention and unravel some prominent features involving unexpected properties about spinor fields under such classification. In particular, we pithily focus on the new aspects — as well as current concrete possibilities. They mainly arise when we deal with some non-standard spinor fields concerning, in particular, their applications in physics.
119200911
Braneworld remarks in Riemann-Cartan manifolds
We analyze the projected effective Einstein equation in a four-dimensional arbitrary manifold embedded in a five-dimensional Riemann–Cartan manifold. The Israel–Darmois matching conditions are investigated, in the context where the torsion discontinuity is orthogonal to the brane. Unexpectedly, the presence of torsion terms in the connection does not modify such conditions whatsoever, despite the modification in the extrinsic curvature and the connection. Then, by imposing the -symmetry, the Einstein equation obtained via Gauss–Codazzi formalism is extended in order to now encompass the torsion terms. We also show that the factors involving contorsion change drastically the effective Einstein equation on the brane, as well as the effective cosmological constant.
56078295
Towards a hybrid compactification with a scalar–tensor global cosmic string
We derive a solution of the gravitational equations which leads to a braneworld scenario in six dimensions, using a global cosmic string solution in a low energy effective string theory framework. The final spacetime is composed by one warped brane with topology and a power law warp factor, and one non-compact extra dimension transverse to the brane; by looking at the current experimental bounds, we find a range of parameters in which, if the on-brane dimension has an acceptable size, it does not solve the hierarchy problem. In another example, this problem is smoothed by means of the Brans–Dicke parameter.