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We introduce the CP violating scalar leptoquark $S_3$ to explain the measured values of the lepton universality ratios $R_{K^{(*)}}$. We derive constraints on the CP-even and CP-odd components of the leptoquark Yukawa couplings stemming from effects in $b to s mu mu$ and $B_s$ mixing. For the $b to s mu mu$ processes we impose $R_{K^{(*)}}$, $mathcal{B}(B_s to mu^+ mu^-)$, as well as CP-sensitive angular asymmetries $A_{7,8,9}$, whereas in the $B_s$ mixing sector $Delta M_s$ and $S_{psiphi}$ are considered. Combining the constraints within the $S_3$ model reveals that a large CP phase with a definite sign is perfectly viable for a leptoquark of mass below a few TeV. For larger mass of the $S_3$ leptoquark the CP phase is suppressed due to the observables pertaining to the $B_s$ system. We provide predictions of direct and mixing-induced CP asymmetries in $B to K mu mu$ that could reveal the presence of the novel CP phase.
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Within the Standard model with the 4th generation quarks b and t we have analyzed CP-violating flavor changing neutral current processes t -> cX; b-> sX, b-> bX,t-> cX, and t-> tX, with X=Z,H,gamma,g, by constructing and employing global, unique fit for the 4th generation mass mixing matrix CKM4 at 300 < m_t < 700 GeV. All quantities appearing in the CKM4 were subject to our fitting procedure. We have found that our fit produces the following CP partial rate asymmetry dominance: a_CP(b-> s(Z,H,gamma,g))= (90,73,52,30)%, at m_t ~ 300,300,380,400 GeV, respectively. From the experimental point of view the best decay mode, out of the above four, is certainly b-> s gamma, because of the presence of a clean high energy single final state photon. We have also obtained relatively large a_CP(t -> c g) ~ 15 (10)% for t running in the loops with the mass m_t= 650(500) GeV. There are fair chances that the 4th generation quarks will be discovered at Tevatron or LHC and that some of their decay rates shall be measured. If b and t exist at energies we assumed, with well executed tagging, large a_CP could be found too.
Precision tests of the Kobayashi-Maskawa model of CP violation are discussed, pointing out possible signatures for other sources of CP violation and for new flavor-changing operators. The current status of the most accurate tests is summarized.
The existence of CP-violation in the leptonic sector is one of the most important issues for modern science. Neutrino physics is a key to the solution of this problem. JUNO (under construction) is the near future of neutrino physics. However CP-violation is not a priority for the current scientific program. We estimate the capability of $delta_{rm CP}$ measurement, assuming a combination of the JUNO detector and a superconductive cyclotron as the antineutrino source. This method of measuring CP-violation is an alternative to conventional beam experiments. A significance level of 3$sigma$ can be reached for 22% of the $delta_{rm CP}$ range. The accuracy of measurement lies between 8$^{rm o}$ and 22$^{rm o}$. It is shown that the dominant influence on the result is the uncertainty in the mixing angle $Theta_{23}$.
We propose to use the unique event topology and reconstruction capabilities of liquid argon time projection chambers to study sub-GeV atmospheric neutrinos. The detection of low energy recoiled protons in DUNE allows for a determination of the leptonic $CP$-violating phase independent from the accelerator neutrino measurement. Our findings indicate that this analysis can exclude several values of $delta_{CP}$ beyond the $3sigma$ level. Moreover, the determination of the sub-GeV atmospheric neutrino flux will have important consequences in the detection of diffuse supernova neutrinos and in dark matter experiments.
We revisit the topic of triple-product asymmetries which probe CP violation through differential distributions. We construct distributions with well-defined discrete symmetry properties and characterize the asymmetries formed upon them. It is stressed that the simplest asymmetries may not be optimal. We explore systematic generalizations having limited reliance on the process dynamics and phase-space parametrization. They exploit larger fractions of the information contained in differential distributions and may lead to increased sensitivities to CP violation. Our detailed treatment of the case of spinless four-body decays paves the way for further experimental studies.
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