Conclusions from CDF results on CP violation in D 0 → π + π -, K + K - and future tasks
Abstract
Within the Standard Model (SM) one predicts both direct and indirect CP violation in D 0 → π + π -, K + K - transitions, although the effects are tiny: Indirect CP asymmetry cannot exceed mathcal{O}left( {{{10}^{ - 4}}} right) , probably even mathcal{O}left( {{{10}^{ - 5}}} right) ; direct effects are estimated at not larger than 10-4. At B factories direct and indirect asymmetries have been studied with {{{left< t rightrangle }} left/ {{{tau_{{D^0}}}}} right.} ∼eq 1 ; no CP asymmetry was found with an upper bound of about 1%. CDF has shown intriguing data on CP violation in D 0 → π + π - [ K + K -] with {{{left< t rightrangle }} left/ {{{tau_{{D^0}}}}} right.} ∼eq 2.4 [2.65]. Also, CDF has not seen any CP violation. For direct CP asymmetry, CDF has a sensitivity similar to the combination of the B factories, yet for indirect CP violation it yields a significantly smaller sensitivity of a_{text{CP}}^{text{ind}} = left( { - 0.01± {{0.06}_{text{stat}}}± {{0.05}_{text{syst}}}} right)% due to it being based on longer decay times. New Physics models (NP) like Little Higgs Models with T-Parity (LHT) can produce an indirect CP asymmetry up to 1%; CDF's findings thus cover the upper range of realistic NP predictions 0.1- 1%. One hopes that LHCb and a Super-Flavour Factory will probe the lower range down to 0.01%. Such non-ad-hoc NP like LHT cannot enhance direct CP violation significantly over the SM level in D 0 → π + π -, K + K - and D ± → π ± K + K - transitions, but others might well do so.
- Publication:
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Journal of High Energy Physics
- Pub Date:
- June 2011
- DOI:
- 10.1007/JHEP06(2011)089
- arXiv:
- arXiv:1103.5785
- Bibcode:
- 2011JHEP...06..089B
- Keywords:
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- Rare Decays;
- Beyond Standard Model;
- CP violation;
- High Energy Physics - Phenomenology;
- High Energy Physics - Experiment
- E-Print:
- 11 pages, 1 figure. V2 has minor corrections and corresponds to the published version