9 research outputs found
Effects of Lepton Flavour Violation on Chargino Production at the Linear Collider
We study the effects of lepton flavour violation (LFV) on the production
processes e+e- --> \chi+_i \chi-_j at a linear collider with longitudinal e+
and e- beam polarizations. In the case of LFV the sneutrino mass eigenstates
have no definite flavour, therefore, in the t-channel more than one sneutrino
mass eigenstate can contribute to the chargino production cross sections. Our
framework is the Minimal Supersymmetric Standard Model (MSSM) including LFV
terms. We show that in spite of the restrictions on the LFV parameters due to
the current limits on rare lepton decays, the cross section \sigma(e+e- -->
\chi+_1 \chi-_1) can change by a factor of 2 or more when varying the LFV
mixing angles. We point out that even if the present bound on BR(tau- --> e-
gamma) improves by a factor of thousand the influence of LFV on the chargino
production cross section can be significant. These results could have an
important impact on the strategies for determining the underlying model
parameters at the linear collider.Comment: 11pp; final version for JHE
CP asymmetries in scalar bottom quark decays
We propose CP asymmetries based on triple product correlations in the decays
sbottom_m -> top chargino_j with subsequent decays of top and chargino_j. For
the subsequent chargino_j decay into a leptonic final state l^- \nu
neutralino_1 we consider the three possible decay chains chargino_j -> l^-
sneutrino -> l^- \nu neutralino_1, chargino_j -> slepton_n \nu -> l^- \nu
neutralino_1 and chargino_j -> W^- neutralino_1 -> l^- \nu neutralino_1. We
consider two classes of CP asymmetries. In the first class it must be possible
to distinguish between different leptonic chargino_j decay chains, whereas in
the second class this is not necessary. We consider also the 2-body decay
chargino_j -> W^- neutralino_1, and we assume that the momentum of the W boson
can be measured. Our framework is the minimal supersymmetric standard model
with complex parameters. The proposed CP asymmetries are non-vanishing due to
non-zero phases for the parameters \mu and/or A_b. We present numerical results
and estimate the observability of these CP asymmetries.Comment: 27 page
CP-odd observables in neutralino production with transverse e+ and e- beam polarization
We consider neutralino production and decay e^+e^ --> chi^0_i chi^0_j,
chi^0_j --> chi^0_1 f \bar{f} at a linear collider with transverse e^+ and e^-
beam polarization. We propose CP asymmetries by means of the azimuthal
distribution of the produced neutralinos and of that of the final leptons,
while taking also into account the subsequent decays of the neutralinos. We
include the complete spin correlations between production and decay. Our
framework is the Minimal Supersymmetric Standard Model with complex parameters.
In a numerical study we show that there are good prospects to observe these CP
asymmetries at the International Linear Collider and estimate the accuracy
expected for the determination of the phases in the neutralino sector.Comment: 30 pages, minor changes in the introduction, references adde
CP asymmetries with Longitudinal and Transverse Beam Polarizations in Neutralino Production and Decay into the Z Boson at the ILC
We study neutralino production at the linear collider with the subsequent two-body decays (chi) over tilde (0)(i) -> (chi) over tilde (0)(n)Z(0) and Z(0) -> lar>, l = e, mu, tau, or Z(0)-> q (q) over bar with q = c,b. We show that transverse electron and positron beam polarizations allow the definition of unique CP observables. These are azimuthal asymmetries in the distributions of the final leptons or quarks. We calculate these CP asymmetries and the cross sections in the Minimal Supersymmetric Standard Model with complex higgsino and gaugino parameters mu and M-1. For final quark pairs, we find CP asymmetries as large as 30%. We discuss the significances for observing the CP asymmetries at the International Linear Collider (ILC). Finally we compare the CP asymmetries with those asymmetries which require unpolarized and/or longitudinally polarized beams only