Speaker
Description
One of the leading sources of uncertainty in the Hadronic Light-by-Light (HLbL) contribution to the muon $g-2$ is the tower of spin-2 resonances, beginning with the $f_2(1270)$. We present progress in evaluating these effects within a new dispersive framework in triangle kinematics, which permits a description of higher-spin states with reduced model dependence by representing the muon anomaly as a sum of two unitarity cuts. A key ingredient is the analysis of the $\gamma^*T\to\pi^+\pi^-$ subprocess in the $P$ wave, identifying $T$ with the $f_2(1270)$. We derive its dispersive solution using the Muskhelishvili–Omnès (MO) representation and discuss its role in the construction of the tensor $T\to\gamma^*\gamma^*$ transition form factors (TFFs), previously measured by Belle only in the singly-virtual region. We show how the MO solution, in conjunction with the TFFs, can yield a robust estimate of the HLbL spin-2 contribution to the muon $g-2$.
| Are you an early career researcher? | Yes, a PhD student |
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