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Investigating CP Violation in the MSSM

Investigating CP Violation in the MSSM. Jamie Tattersall. Introduction. In the SM the only source of CP violation comes from the complex phase within the CKM matrix. Not sufficient amount of CP for Cosmological constraints on Baryogenesis.

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Investigating CP Violation in the MSSM

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  1. Investigating CP Violation in the MSSM Jamie Tattersall

  2. Introduction • In the SM the only source of CP violation comes from the complex phase within the CKM matrix. • Not sufficient amount of CP for Cosmological constraints on Baryogenesis. • MSSM (Minimal Supersymmetric Model) however can contain several complex parameters that can all contribute. • In Neutralino sector these are U(1) gaugino mass parameter, M1,and Higgsino mass parameter, μ. (The SU(2) gaugino mass parameter M2 can be made real by redefining the fields.) • Physical phases φM1 and φμimply CP odd observables that can in principle be large as they are already present at tree level. • Constraints are present from Electric Dipole Moments but with cancellations between different contributions we find |φμ| < 0.1π and M1 unconstrained (very model dependent).

  3. Triple Product Correlations • Useful Tool for studying CP odd observables are Triple Product Correlations. • Construct the two observables: • Note that under CP: • If we cannot distinguish the two reactions but we know that they occur with equal probability, CP invariance requires we see no correlation of the form: • Sign of observable will also give sign of CP phase (not true of CP even observables). → Asymmetry will vanish under CP

  4. CP Odd Observables • Require at least a three body decay mediated by a particle that is not a scalar (allow spin correlations) and a complex phase. • Possible contribution of the form: • In the rest frame of the decaying particle, • this is given by the expectation value of the triple product: • A non zero expectation value, <T>, implies T violation and assuming CPT is satisfied, T violation is equivalent to non-conservation of CP.

  5. Embodying CP asymmetry • Look at full process: • Choose triple product from decay: • Momentum conservation forces l+, l-, χ0j to define a plane • A non-zero expectation value of T, implies a non-zero average angle between the plane and the z-axis. • Define asymmetry parameter: • where:

  6. My Work (so far) • Calculate all tree level processes including spin correlations for following: • Calculate analytical expression for phase space at each point in the decay. • Implement in a computer program along with extra production modes and Parton Density Functions to allow a scan of possible asymmetry over parameter space (on its way). Thank you for listening and please ask any questions

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