Speaker
Prof.
Lianrong Dai
(Liaoning Normal University)
Description
First I will present an novel approach on tau decay recently developed, using the basic weak interaction and angular momentum algebra to relate the different processes. The formalism also leads to a different interpretation of the role played by G-parity in these decays. We compare our results with experiment and other theoretical approaches for rates and invariant mass distributions and make predictions for unmeasured decays [1].
Then some interesting applications will be presented, including the polarization amplitudes and final state interaction on different decays:
a) We applied the above novel approach to investigate the different polarization amplitudes on tau decay within the Standard Model. We also extend the formalism to a case that can account for different models beyond the Standard Model. We find one magnitude sensitive and useful to test different models beyond the Standard Model[2].
b) The above developed novel approach was further applied to study the final state interaction:
(1) The triangle mechanism for the decay $\tau^- \to \nu_\tau \pi^- f_0(980)$ was studied with $f_0(980)$ decaying into $\pi^+ \pi^- $ and find a narrow peak in the $\pi^+ \pi^-$ invariant mass distribution, in which we explicitly filters $G$-parity states. Similarly, we also study the triangle mechanism for the decay
$\tau \to \nu \pi^- a_0(980)$, with the $a_0(980)$ decaying into $\pi^0 \eta $.
Our prediction of find final branching ratios for $\pi^- f_0(980)$ and $\pi^- a_0(980)$ of the order of $4 \times 10^{-4}$ and $7 \times 10^{-5}$, respectively, which are within present measurable range. Experimental verification of these predictions will shed light on the nature of the scalar mesons and on the origin of the ``$a_1(1420)$" peak observed in other reactions [3].
(2) We further make some predictions for the decay $\tau \to \nu_\tau P A$, with $P$ a $\pi$ or $K$ and $A$ an axial-vector resonance $b_1(1235)$, $h_1(1170)$, $h_1(1380)$, $a_1(1260)$, $f_1(1285)$ or any of the two poles of the $K_1(1270)$, in which explicitly filtering different $G$-parity states. we evaluate the vector-pseudoscalar amplitudes within the chiral unitary theory, where the axial-vector resonances were obtained as dynamically generated from the VP interaction. We make predictions for invariant mass distribution and branching ratios for the channels considered [4].
Experimental verification of these predictions will shed light on the nature of these scalar mesons and axial-vector resonance states.
References
[1]L. R. Dai, R. Pavao, S. Sakai and E. Oset, $\tau^- \to \nu_{\tau} M_1 M_2$, with $M_1, M_2$ pseudoscalar or vector mesons, Eur. Phys. J. A 55 (2019) 20
[2]L. R. Dai and E.Oset, Polarization amplitudes in $\tau^- \to \nu_{\tau} V P$ decay beyond the standard model, Eur. Phys. J. A 54 (2018) 219
[3]L. R.Dai, Q. X. Yu and E. Oset, Triangle singularity in $\tau^- \to \nu_\tau \pi^- f_0(980)$ ($a_0(980)$) decays, Phys. Rev. D 99 (2019) 016021
[4]L. R .Dai, L. Roca and E. Oset, $\tau$ decay into a pseudoscalar and an axial-vector meson, Phys. Rev. D 99 (2019) 096003
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Primary author
Prof.
Lianrong Dai
(Liaoning Normal University)
