Manchester Particle Physics Seminars, Colloquia and Meetings

Shanzhen Chen & Kevin Maguire: Searching for CP Violation in Charm decays

Friday, 17 February 2017 from to (Europe/London)
at Schuster ( 54-6-6.40 - Niels Bohr Common Room )
While CP Violation has been observed in the kaon and beauty systems it has not been in an ‘up’ type quark system. The LHCb experiment has recorded the world’s largest sample of charmed meson decays. Two recent complementary searches for CP violation are discussed. 

A search for Indirect CP violation in two-body decays is presented. Two-body decays are of particular interest due to their large branching fractions and the abundance of Cabibbo favoured (CF) control modes, suppressed modes and CP eigenstates. The observable A_{\Gamma}, which is predominantly a measure of indirect CP violation, is accessed through the singly Cabibbo suppressed decays D0 → K+K− and D0 → π+π−. Measurements of A_{\Gamma} presented here prove the world’s most sensitive check for indirect CP violation. The results show no evidence of CP violation and improve on the precision of the previous measurements by nearly a factor of two.

A search for direct CP violation in a four-body decays is presented.  Searches in multi-body decays are interesting due to the rich past space of overlapping decays  In this presentation, a search for time-integrated CP violation in the Cabibbo-suppressed decay $D^0\rightarrow \pi^+\pi^-\pi^+\pi^-$ using an unbinned, model-independent technique known as the energy test is presented. This is the first application of the energy test in four-body decays. This search is performed for P-even CP asymmetries and, for the first time, is extended to probe the P-odd case. The result in the P-odd case is only marginally consistent with the hypothesis of CP symmetry, corresponding to a significance for CP non-conservation of 2.7 standard deviations.
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