D* -> D + gamma BR calculation

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SUMMARY

The discussion focuses on the calculation of the decay process D* -> D + gamma, specifically addressing the factorized amplitude and the decomposition of matrix elements involved in this radiative decay. The amplitude is expressed as M ∝ [A1<γ|ūγμ(1-γ5)c|D*0> + A2<γ|ūiσμνpν(1+γ5)c|D*0>. The participants emphasize the importance of photon and D* polarizations, momenta, and constants that depend on p². The discussion also raises questions about the handling of D* matrices and the role of γ5 in the context of electromagnetic decay.

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Hepth
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Can anyone walk me through this calculation? I'm not completely sure how to do it (merely a student).

So is this considered a 1 body radiative decay? So the factorized amplitude would be something like
M \propto &lt;D^0|\bar{u}\gamma_\mu\left(1-\gamma_5\right)c|0&gt;[A_1 &lt;\gamma|\bar{u}\gamma_\mu\left(1-\gamma_5\right)c|D^{*0}&gt;+A_2&lt;\gamma|\bar{u}i \sigma_{\mu \nu} p_\nu \left(1+\gamma_5\right)c|D^{*0}&gt;

And each matrix can be decomposed into some constants/vectors/polarizations etc.

&lt;D^0|\bar{u}\gamma_\mu\left(1-\gamma_5\right)c|0&gt; = i f_{D^0} P_{D^{0}\mu}

and the second and third terms can be similarly decomposed into linear combinations of terms depending only on:
Photon Polarization \epsilon^{*}_{\gamma \alpha}
D^{*0} Polarization \epsilon^{*}_{D^{*0} \beta}
Momentums of the photon and D* (q and p respectively)
And the constants can depend on p^2.

So any sort of combination of these such that the end result yields one remaining index.

Now my first question, for those that do these sort of things, am I handling the D* matrices correctly? Am I missing any effective terms/form factors?
 
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This is over my head, because I am an experimenter, but what are all the gamma_5's doing there? This is an electromagnetic decay, so why are you projecting out the left handed state?
 

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