Precocious signs of new physics: Are we eight now?
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Although the CKM-paradigm seems to work to an accuracy of about 15–20%, we emphasize that there are by now several indications that suggest the need for a beyond the Standard Model CP-odd phase. The value of $\sin 2\beta$ measured via the gold-plated (tree) mode, $B \rightarrow \psi K_{\text{s}}$ is smaller than the value deduced by using improved lattice matrix elements. The value of $\sin 2\beta$ measured via `penguin-dominated` (loop) decays tends to be even smaller still. There is also a rather large difference between the direct CP asymmetries in $\bar{B}^{0} \rightarrow K^{−} \pi^{+}$ and $B^{−} \rightarrow K^{−} \pi^{0}$ that is rather difficult to understand. More recently, CDF and D0 are finding about a $2\sigma$ signal in CP asymmetry in the corresponding gold-plated mode $B_{\text{s}} \rightarrow \psi \phi$. If true, this would be consistent with the indications of new CP-phase in penguin $b \rightarrow s$ transitions seen at 𝐵-factories. After describing these possible signs of trouble for the SM-CKM paradigm, we give a brief discussion of some of the BSM scenarios that could be the underlying cause of these deviations. In particular, we find that the data are quite suggestive of a fourth family with $m_{t}^{ˊ} in the range of 400–600 GeV as perhaps the simplest BSM candidate which `naturally' explains the data.
Amarjit Soni^{1} ^{}
Volume 94, 2020
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