Generalized elastic positivity bounds on interacting massive spin-2 theories

We use generalized elastic positivity bounds to constrain the parameter space of multi-field spin-2 effective field theories. These generalized bounds involve inelastic scattering amplitudes between particles with different masses, which contain kinematic singularities even in the t = 0 limit. We apply these bounds to the pseudo-linear spin-2 theory, the cycle spin-2 theory and the line spin-2 theory respectively. For the pseudo-linear theory, we exclude the remaining operators that are unconstrained by the usual elastic positivity bounds, thus excluding all the leading (or highest cutoff) interacting operators in the theory. For the cycle and line theory, our approach also provides new bounds on the Wilson coefficients previously unconstrained, bounding the parameter space in both theories to be a finite region (i.e., every Wilson coefficient being constrained from both sides). To help visualize these finite regions, we sample various cross sections of them and estimate the total volumes.

Shift-type SMEFT effects in dileptons at the LHC

We explore the constraints which can be derived on Wilson coefficients in the Standard Model Effective Field Theory from dilepton production, notably including the constraints on operators which do not lead to cross sections growing with energy relative to the Standard Model rate, i.e. shifts. We incorporate essential theory error estimates from higher EFT orders in the analysis in order to provide robust bounds. We find that constraints on four-fermion operator contributions which do grow with energy are not materially weakened by the inclusion of these shifts, and that a constraint on the shifts can also be derived, with a characteristic strength comparable to, and a directionality in parameter space complementary to, those from LEP data. This completes the study of hadronically-quiet dilepton production in the SMEFT, and provides two new constraints which are linearly independent from others arising at the LHC and also rotated in Wilson coefficient space relative to, though not completely independent from, the LEP bounds.

NLO gravitational quartic-in-spin interaction

In this paper we derive for the first time the complete gravitational quartic-in-spin interaction of generic compact binaries at the next-to-leading order in the post-Newtonian (PN) expansion. The derivation builds on the effective field theory for gravitating spinning objects, and its recent extensions, in which new type of worldline couplings should be considered, as well as on the extension of the effective action of a spinning particle to quadratic order in the curvature. The latter extension entails a new Wilson coefficient that appears in this sector. This work pushes the precision frontier with spins at the fifth PN (5PN) order for maximally-spinning compact objects, and at the same time informs us of the gravitational Compton scattering with higher spins.

CP violating hW+W− coupling in the Standard Model and beyond

Inspired by the recent development in determining the property of the observed Higgs boson, we explore the CP-violating (CPV) $$ -{c}_{\mathrm{CPV}}{hW}^{+\mu \nu}{\tilde{W}}_{\mu \nu}^{-}/\upsilon $$ − c CPV hW + μν W ˜ μν − / υ coupling in the Standard Model (SM) and beyond, where W±μν and $$ {\tilde{W}}^{\pm \mu \nu} $$ W ˜ ± μν denote the W-boson field strength and its dual. To begin with, we show that the leading-order SM contribution to this CPV vertex appears at two-loop level. By summing over the quark flavor indices in the two loop integrals analytically, we can estimate the order of the corresponding Wilson coefficient to be $$ {c}_{\mathrm{CPV}}^{\mathrm{SM}}\sim \mathcal{O}\left({10}^{-23}\right) $$ c CPV SM ∼ O 10 − 23 , which is obviously too small to be probed at the LHC and planned future colliders. Then we investigate this CPV hW+W− interaction in two Beyond the Standard Model benchmark models: the left-right model and the complex 2-Higgs doublet model (C2HDM). Unlike what happens for the SM, the dominant contributions in both models arise at the one-loop level, and the corresponding Wilson coefficient can be as large as of $$ \mathcal{O} $$ O (10−9) in the former model and of $$ \mathcal{O} $$ O (10−3) for the latter. In light of such a large CPV effect in the hW+W− coupling, we also give the formulae for the leading one-loop contribution to the related CPV hZZ effective operator in the complex 2-Higgs doublet model. The order of magnitude of the Wilson coefficients in the C2HDM may be within reach of the high-luminosity LHC or planned future colliders.

Predictions for $$B_s \rightarrow {\bar{K}}^* \ell \,\ell $$ in non-universal $$Z'$$ models

The lepton flavor universality violating (LFUV) measurements $$R_K$$RK and $$R_{K^*}$$RK∗ in B meson decays can be accounted for in non-universal $$Z'$$Z′ models. We constrain the couplings of these $$Z'$$Z′ models by performing a global fit to correlated $$b \rightarrow s \ell \ell $$b→sℓℓ and $$b \rightarrow d \ell \ell $$b→dℓℓ processes, and calculate their possible implications for $$B_s \rightarrow {\bar{K}}^*\ell \ell $$Bs→K¯∗ℓℓ observables. For real new physics (NP) couplings, the 1$$\sigma $$σ favored parameters allow the corresponding LFUV ratio $$R_{K^*}^{(s)}$$RK∗(s) in $$B_s \rightarrow {\bar{K}}^*\ell \ell $$Bs→K¯∗ℓℓ to range between 0.8 and 1.2 at low $$q^2$$q2. Complex NP couplings improve the best fit only marginally, however they allow a significant enhancement of the branching ratio, while increasing the range of $$R_{K^*}^{(s)}\ $$RK∗(s)at low $$q^2$$q2 to 0.8–1.8. We find that NP could cause zero-crossing in the forward–backward asymmetry $$A_{FB}$$AFB to shift towards lower $$q^2$$q2 values, and enhancement in the magnitude of integrated $$A_{FB}$$AFB. The CP asymmetry $$A_{CP}$$ACP may be suppressed and even change sign. The simultaneous measurements of integrated $$R_{K^*}^{(s)}\ $$RK∗(s)and $$A_{CP}$$ACP values to 0.1 and 1% respectively, would help in constraining the effective NP Wilson coefficient $$C_9$$C9 in $$ b \rightarrow d \mu \mu $$b→dμμ interactions.