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Register a new userNew Physics Constraints from Atomic Parity Violation in $^{133}$Cs
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Our improved calculation of the nuclear spin-independent parity violating electric dipole transition amplitude ($E1_{PV}$) for $6s ~ ^2S_{1/2} - 7s ~ ^2S_{1/2}$ in $^{133}$Cs in combination with the most accurate (0.3%) measurement of this quantity yields a new value for the nuclear weak charge $Q_W=-73.71(26)_{ex} (23)_{th}$ against the Standard Model (SM) prediction $Q_W^{text{SM}}=-73.23(1)$. The advances in our calculation of $E1_{PV}$ have been achieved by using a variant of the perturbed relativistic coupled-cluster theory which treats the contributions of the core, valence and excited states to $E1_{PV}$ on the same footing unlike the previous high precision calculations. Furthermore, this approach resolves the controversy regarding the sign of the core correlation effects. We discuss the implications of the deviation of our result for $Q_W$ from the SM value by considering different scenarios of new physics.
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Atomic Parity Violation (APV) is usually quantified in terms of the weak nuclear charge $Q_W$ of a nucleus, which depends on the coupling strength between the atomic electrons and quarks. In this work, we review the importance of APV to probing new physics using effective field theory. Furthermore, using $SU(2)$ invariance, we correlate our findings with those from neutrino-nucleus coherent scattering. Moreover, we investigate signs of parity violation in polarized electron scattering and show how precise measurements on the Weinberg angle, $sin theta_W$, will give rise to competitive bounds on light mediators over a wide range of masses and interactions strength. Lastly, apply our bounds to several models namely, Dark Z, Two Higgs Doublet Model-$U(1)_X$ and 3-3-1, considering both light and heavy mediator regimes.
New-physics (NP) constraints on first-generation quark-lepton interactions are particularly interesting given the large number of complementary processes and observables that have been measured. Recently, first hints for such NP effects have been observed as an apparent deficit in first-row CKM unitarity, known as the Cabibbo angle anomaly, and the CMS excess in $qbar qto e^+e^-$. Since the same NP would inevitably enter in searches for low-energy parity violation, such as atomic parity violation, parity-violating electron scattering, and coherent neutrino-nucleus scattering, as well as electroweak precision observables, a combined analysis is required to assess the viability of potential NP interpretations. In this article we investigate the interplay between LHC searches, the Cabibbo angle anomaly, electroweak precision observables, and low-energy parity violation by studying all simplified models that give rise to tree-level effects related to interactions between first-generation quarks and leptons. Matching these models onto Standard Model effective field theory, we derive master formulae in terms of the respective Wilson coefficients, perform a complete phenomenological analysis of all available constraints, point out how parity violation can in the future be used to disentangle different NP scenarios, and project the constraints achievable with forthcoming experiments.
A concise review of atomic parity violation with a focus on the measurement and interpretation of parity violation in cesium.
We consider the implications of low-energy precision tests of parity violation on t-channel mediator models explaining the top AFB excess measured by CDF and D0. Flavor-violating u-t or d-t couplings of new scalar or vector mediators generate at one-loop an anomalous contribution to the nuclear weak charge. As a result, atomic parity violation constraints disfavor at >3 sigma t-channel models that give rise to a greater than 20% AFB at the parton level for M_tt > 450 GeV while not producing too large a top cross-section. Even stronger constraints are expected through future measurements of the proton weak charge by the Q-Weak experiment.
These proceedings review the status of New Physics contributions to flavour violating $B$ decays. The anomalies in charged and neutral current $B$ decays related to lepton flavour universality violation have received a substantial amount of attention over the past years, and we discuss the current status in light of the new data presented earlier this year. We also recall a tension in the neutral $B$ meson mixing observables $Delta M_d$ and $Delta M_s$ and in particular their ratio, when compared with their SM predictions obtained using tree-level determinations of the CKM matrix and the recent lattice QCD results for the relevant hadronic matrix elements. Last but not least, we advocate kaon physics as a unique probe of very high energy scales and briefly discuss the current status of $varepsilon/varepsilon$ and $Ktopi ubar u$.
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