text: 45,105,1273418141243228161,20703003,Peter B Denton,"New neutrino paper, this time with Rebekah Pestes a @VTPhysics grad student visiting BNL on the SCGSR program. We discuss what deltaCP for neutrino oscillations really means and highlight the impact of how it's not actually a fundamental parameter. <LINK> 1/7 If we do the rotations in the PMNS matrix in a different order, what changes? This figure shows that even if deltaPDG in the usual parameterization is constrained (that is, we ignore the T2K app data), delta in other parameterizations is constrained to within 150-210 degrees! 2/7 <LINK> (The shaded regions show the effect of varying the osc params within their 3 σ regions.) While the premise might have been expected by some neutrino theorists, how tightly delta in other parameterizations is constrained was surprising to me anyway. 3/7 The reason is because |Ue3| is small (that is, theta13 is small). In other parameterizations this looks like sqrt(A+B*cos(delta)) so cos(delta) has to be near -1 for the cancellation to work. It's a bit subtle but we have useful approximations in the paper. 4/7 The above figure also implies that precision in delta doesn't mean much of anything fundamental. We show that here where we plot what a precision on deltaPDG of 15deg looks like in different parameterizations; it could be as small as 1deg! 5/7 <LINK> So what's the right answer? Within the context of oscillations it's always the Jarlskog (pictured here). This quantity is the closest to what is measured and doesn't require as much input from solar parameters to extract unlike using delta. 6/7 <LINK> While some aspect of these concepts has been discussed in the past, we focus on the situation in light of current measurements. As we zero in on the remaining parameters, keeping straight what is/isn't fundamental is more important than ever! 7/7 *this should say ""in the usual parameterization is UNconstrained""",https://arxiv.org/abs/2006.09384,"CP violation in the lepton mass matrix will be probed with good precision in upcoming experiments. The amount of CP violation present in oscillations can be quantified in numerous ways and is typically parameterized by the complex phase $\delta_{\rm PDG}$ in the standard PDG definition of the lepton mixing matrix. There are additional parameterizations of the lepton mixing matrix as well. Through various examples, we explore how, given the current data, different parameterizations can lead to different conclusions when working with parameterization dependent variables, such as $\delta$. We demonstrate how the smallness of $|U_{e3}|$ governs the scale of these results. We then demonstrate how $\delta$ can be misleading and argue that the Jarlskog is the cleanest means of presenting the amount of CP violation in the lepton sector. We also confirm that, among the different parameterizations considered, the standard PDG parameterization has a number of convenient features. ","The Impact of Different Parameterizations on the Interpretation of CP