- #1
andrex904
- 15
- 1
Hi, I'm trying to compute the differential decay of W boson at rest
$$W^+ \rightarrow e^+ \nu_e$$
where the boson has fixed spin along z axis, and so specific cirular polarization. Using Feynman rules i get
$$M=\frac{ig_w}{\sqrt{2}}\bar{u}(q)\gamma^\mu(\frac{1-\gamma_5}{2})v(k)\epsilon_\mu^\lambda(p)$$
and I'm in trouble with a term coming from trace
## \varepsilon^{\alpha \mu \beta \nu} q_\alpha k_\beta ## ## \epsilon^\lambda_\mu ## ## \epsilon^{*\lambda}_\nu ##
where ##\varepsilon## is the Levi-Civita symbol.
$$W^+ \rightarrow e^+ \nu_e$$
where the boson has fixed spin along z axis, and so specific cirular polarization. Using Feynman rules i get
$$M=\frac{ig_w}{\sqrt{2}}\bar{u}(q)\gamma^\mu(\frac{1-\gamma_5}{2})v(k)\epsilon_\mu^\lambda(p)$$
and I'm in trouble with a term coming from trace
## \varepsilon^{\alpha \mu \beta \nu} q_\alpha k_\beta ## ## \epsilon^\lambda_\mu ## ## \epsilon^{*\lambda}_\nu ##
where ##\varepsilon## is the Levi-Civita symbol.