Investigation of exclusive final states with two neutral pions in COMPASS 2009 hadron beam data

by Bastian Kugler (TUM)

Thursday 25 Jun 2026, 14:30 → 15:30 Europe/Berlin

E18/ENE Seminar Room 3268 (TUM PH)

To study the low-energy regime of the strong interaction, Chiral Perturbation Theory can be used. One of the predictions of the chiral anomaly and $\chi$PT is the $\gamma\pi \rightarrow \pi\pi$ amplitude at low interaction energies, described by the $F_{3\pi}$ coupling constant. In the COMPASS experiment at CERN, this is done via the Primakoff method. In this analysis, we take a look at interactions of the form $\pi^-(\pi^+)^* \rightarrow \pi^0\pi^0$ to find kinematic distributions to estimate the $\pi^-(\pi^0)^* \rightarrow \pi^-\pi^0$ background of the anomalous process $\pi^- \gamma^{(*)}\rightarrow \pi^-\pi^0$ under investigation at COMPASS. Here we find strong evidence of charged-pion exchange. Furthermore, we find evidence for an intermediate state containing a $f_2(1270)$, $K^0_S$, and $f_0(500)$. We further examine the angle and momentum-transfer distributions for the different mass regions of the intermediate states.