% IMPORTANT: The following is UTF-8 encoded. This means that in the presence % of non-ASCII characters, it will not work with BibTeX 0.99 or older. % Instead, you should use an up-to-date BibTeX implementation like “bibtex8” or % “biber”. @INPROCEEDINGS{Krner:292120, author = {Körner, J. G.}, title = {{H}elicity {A}mplitudes and {A}ngular {D}ecay {D}istributions}, address = {Hamburg}, publisher = {Deutsches Elektronen-Synchrotron, DESY}, reportid = {PUBDB-2015-05833, MITP-14-004. arXiv:1402.2787}, pages = {169-184}, year = {2014}, abstract = {I discuss how to obtain angular decay distributions for sequentialcascade decays using helicity methods. The angular decay distributionsfollow from a reasonably simple master formula involving bilinearforms of helicity amplitudes and Wigner's $d$ functions. I discussin some detail the issue of gauge invariance for off-shell gauge bosons.As a technical exercise I calculate the linear relation between thehelicity amplitudes and the invariant amplitudes of semileptonic andrare baryon decays. I discuss two explicit examples of angular decaydistributions for (i) the decay $t\to b+W^+(\to \ell^+\nu_\ell)$ (whichleads to the notion of the helicity fractions of the $W^+$), and (ii)the sequential decay $\Lambda_b\to\Lambda(\to p\pi^-)+J/\psi(\to \ell^+\ell^-)$.T = Helicity Amplitudes and Angular Decay Distributions}, month = {Jul}, date = {2013-07-15}, organization = {Helmholtz International School on Physics of Heavy Quarks and Hadrons, Dubna (Russia), 15 Jul 2013 - 28 Jul 2013}, keywords = {helicity: amplitude analysis (INSPIRE) / baryon: decay (INSPIRE) / gauge boson: off-shell (INSPIRE) / invariance: gauge (INSPIRE) / cascade decay (INSPIRE)}, cin = {L}, cid = {I:(DE-H253)L-20120731}, pnm = {899 - ohne Topic (POF3-899)}, pid = {G:(DE-HGF)POF3-899}, experiment = {EXP:(DE-H253)HERA(machine)-20150101}, typ = {PUB:(DE-HGF)8 / PUB:(DE-HGF)15}, eprint = {1402.2787}, howpublished = {arXiv:1402.2787}, archivePrefix = {arXiv}, SLACcitation = {$\%\%CITATION$ = $arXiv:1402.2787;\%\%$}, doi = {10.3204/DESY-PROC-2013-03/Koerner}, url = {https://bib-pubdb1.desy.de/record/292120}, }