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CP Violation in SUSY Particle Production and Decay

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 Added by Stefan Hesselbach
 Publication date 2007
  fields
and research's language is English
 Authors S. Hesselbach




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Recent studies about CP violation in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters are reviewed. In order to unambiguously identify the CP-violating phenomena it is necessary to study CP-odd or T-odd observables. In chargino and neutralino production and decay at the International Linear Collider (ILC) triple product asymmetries and asymmetries defined via transverse beam polarization have been analyzed. It has been found that these asymmetries can be measured at the ILC in a large region of the MSSM parameter space and are thus an important tool to establish CP violation in supersymmetry.



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216 - S. Hesselbach 2007
Physical Higgs particles in the Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation are CP mixed states. The decay of these Higgs particles can be analysed to study the CP properties of the MSSM. In the present work we consider the di-photon channel of the lightest neutral Higgs boson for this purpose. Compared to earlier studies on effects of scalar/pseudo-scalar mixing, our analysis also investigates the effect due to Higgs-sfermion-sfermion couplings along with that of mixing. We find that a light stop may have a strong impact on the width and Branching Ratio (BR) of the decay process H1 --> gamma.gamma, whereas other light sparticles have only little influence. In some regions of the MSSM parameter space with large CP-violating phase phi-mu ~ 90 deg a light (~ 200 GeV) stop can change the di-photon BR by more than 50 % compared to the case with heavy (~ 1 TeV) stop and otherwise same MSSM parameters.
We discuss the potential to observe effects of CP violation in squark decay chains at the LHC. As the CP-violating observable we use the asymmetry composed by triple products of final state momenta. Extending methods for momentum reconstruction we show that there are good prospects for observation of these effects at the LHC. Finally, we include the main experimental factors and discuss the expected sensitivity.
We discuss the formalism of two Higgs doublet model type III with CP violation from CP-even CP-odd mixing in the neutral Higgs bosons. The flavor changing interactions among neutral Higgs bosons and fermions are presented at tree level in this type of model. These assumptions allow the study rare top decays mediated by neutral Higgs bosons, particularly we are interested in $trightarrow c l^+l^-$. For this process we estimated upper bounds of the branching ratios $textrm{Br}(trightarrow c tau^+tau^-)$ of the order of $10^{-9}sim 10^{-7}$ for a neutral Higgs boson mass of 125 GeV and $tanbeta=1$, 1.5, 2, 2.5. For the case of $trightarrow c tau^+tau^-$ the number of possible events is estimated from 1 to 10 events which could be observed in future experiments at LHC with a luminosity of 300 $textrm{fb}^{-1}$ and 14 GeV for the energy of the center of mass. Also we estimate that the number of events for the process $trightarrow c l^+l^-$ in different scenarios is of order of $2500$.
The radiative decay of neutral fermions has been studied for decades but $CP$ violation induced within such a paradigm has evaded attention. $CP$ violation in these processes can produce an asymmetry between circularly polarised directions of the radiated photons and produces an important source of net circular polarisation in particle and astroparticle physics observables. The results presented in this work outlines the general connection between $CP$ violation and circular polarisation for both Dirac and Majorana fermions and can be used for any class of models that produce such radiative decays. The total $CP$ violation is calculated based on a widely studied Yukawa interaction considered in both active and sterile neutrino radiative decay scenarios as well as searches for dark matter via direct detection and collider signatures. Finally, the phenomenological implications of the formalism on keV sterile neutrino decay, leptogenesis-induced right-handed neutrino radiative decay and IceCube-driven heavy dark matter decay are discussed.
440 - D.Delepine 2007
We analyze the CP violation in the semileptonic | Delta S|=1 tau-decays in supersymmetric extensions of the standard model (SM) with R parity violating term. We show that the CP asymmetry of tau-decay is enhanced significantly and the current experimental limits obtained by CLEO collaborations can be easily accommodated. We argue that observing CP violation in semi leptonic tau-decay would be a clear evidence for R-parity violating SUSY extension of the SM.
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