CP violating angular asymmetries of b and bbar quarks in e+e- -> t tbar

We obtain analytical formulae for the cross section and the angular distributions of the b(bbar) quarks in the process e+e- -> t tbar, with t -> W+ b (tbar -> W- bbar) assuming CP violation in the \gamma t tbar and Z t tbar vertices. We present CP violating asymmetries, which measure separately the real and imaginary parts of the electroweak dipole moment form factors of the top, d^{\gamma}(s) and d^{Z}(s). We give a numerical analysis of these asymmetries within the Minimal Supersymmetric Standard Model with complex parameters. They turn out to be of order <= 10^{-3}.Comment: 22 pages LaTeX with 3x3 figures included; some definitions for polarization asymmetries and some notations are changed and some references adde

Flavour violating bosonic squark decays at LHC

We study quark flavour violation (QFV) in the squark sector of the Minimal Supersymmetric Standard Model (MSSM). We assume mixing between the second and the third squark generations, i.e. sc_R-st_{L,R} mixing mixing. We focus on QFV effects in bosonic squark decays, in particular on the decay into the lightest Higgs boson h0, su_2 -> su_1 h0, where su_{1,2} are the lightest up-type squarks. We show that the branching ratio of this QFV decay can be quite large (up to 50 %) due to large QFV trilinear couplings, and large sc_R-st_{L, R} and st_L-st_R mixing, despite the strong constraints on QFV from B meson data. This can result in characteristic QFV final states with significant rates at LHC (14 TeV), such as pp -> gluino gluino X -> t + h0 + 3jets + Etmiss + X and pp -> gluino gluino X -> t t (or tbar tbar) + h0 + 2jets + Etmiss + X. The QFV bosonic squark decays can have an influence on the squark and gluino searches at LHC.Comment: Figure 3 replaced, Section 4 revise

Flavour violating squark and gluino decays at LHC

We study the effects of squark generation mixing on squark and gluino production and decays at LHC in the Minimal Supersymmetric Standard Model (MSSM) with focus on the mixing between second and third generation squarks. Taking into account the constraints from B-physics experiments we show that various regions in parameter space exist where decays of squarks and/or gluinos into quark flavour violating (QFV) final states can have large branching ratios. Here we consider both fermionic and bosonic decays of squarks. Rates of the corresponding QFV signals, e.g. pp -> t t bar{c} bar{c} missing-E_T X, can be significant at LHC(14 TeV). We find that the inclusion of flavour mixing effects can be important for the search of squarks and gluinos and the determination of the underlying model parameters of the MSSM at LHC.Comment: 7 pages, 4 figures, a reference updated, Proceedings of The 36th International Conference on High Energy Physics (ICHEP2012), Melbourne, Australia, July 4-11, 201

CP sensitive observables in chargino production and decay into a W boson

We study CP sensitive observables in chargino production in electron-positron collisions with subsequent two-body decay of one chargino into a W boson. We identify the CP odd elements of the W boson density matrix and propose CP sensitive triple-product asymmetries of the chargino decay products. We calculate the density-matrix elements, the CP asymmetries and the cross sections in the Minimal Supersymmetric Standard Model with complex parameters \mu and M_1 for an e+ e- linear collider with \sqrt{s} = 800 GeV and longitudinally polarized beams. The asymmetries can reach 7% and we discuss the feasibility of measuring these asymmetries.Comment: 23 pages, 7 figure

CP violation in charged Higgs decays in the MSSM

In the MSSM with complex parameters loop corrections to the decays $H^+ \to t \bar{b}$ and $H^- \to \bar{t} b$ with $t \to b W$ and $W \to l \nu$ lead to CP-violating asymmetries: a decay rate asymmetry, a forward-backward asymmetry and an energy asymmetry. We derive explicit formulas for them and perform a detailed numerical analysis. We study the dependence on the parameters and the phases involved. In particular, the influence of the running Yukawa coupling is taken into account. The decay rate asymmetry can go up to 25%, the forward-backward and the energy asymmetry up to 10%.Comment: 18 pages, 13 postscript figures, JHEP style, Feynman graphs replaced, one reference adde

Statistical and systematic errors in redshift-space distortion measurements from large surveys

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2012 RAS © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We investigate the impact of statistical and systematic errors on measurements of linear redshift-space distortions (RSD) in future cosmological surveys by analysing large catalogues of dark matter haloes from the baryonic acoustic oscillation simulations at the Institute for Computational Cosmology. These allow us to estimate the dependence of errors on typical survey properties, as volume, galaxy density and mass (i.e. bias factor) of the adopted tracer. We find that measures of the specific growth rate β = f/b using the Hamilton/Kaiser harmonic expansion of the redshift-space correlation function ξ(r p, π) on scales larger than 3h -1 Mpc are typically underestimated by up to 10 per cent for galaxy-sized haloes. This is significantly larger than the corresponding statistical errors, which amount to a few per cent, indicating the importance of non-linear improvements to the Kaiser model, to obtain accurate measurements of the growth rate. The systematic error shows a diminishing trend with increasing bias value (i.e. mass) of the haloes considered. We compare the amplitude and trends of statistical errors as a function of survey parameters to predictions obtained with the Fisher information matrix technique. This is what is usually adopted to produce RSD forecasts, based on the Feldman-Kaiser-Peacock prescription for the errors on the power spectrum. We show that this produces parameter errors fairly similar to the standard deviations from the halo catalogues, provided it is applied to strictly linear scales in Fourier space (k<0.2 h Mpc -1). Finally, we combine our measurements to define and calibrate an accurate scaling formula for the relative error on β as a function of the same parameters, which closely matches the simulation results in all explored regimes. This provides a handy and plausibly more realistic alternative to the Fisher matrix approach, to quickly and accurately predict statistical errors on RSD expected from future surveysEM is supported by the Spanish MICINNs Juan de la Cierva programme (JCI-2010-08112), by CICYT through the project FPA-2009 09017 and by the Community of Madrid through the project HEPHACOS (S2009/ESP-1473) under grant P-ESP-00346. Financial support of PRIN-INAF 2007, PRIN-MIUR 2008 and ASI Contracts I/023/05/0, I/088/06/0, I/016/07/0, I/064/08/0 and I/039/10/0 is gratefully acknowledged. LG is partly supported by ERC Advanced Grant #291521 ‘DARKLIGHT’