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arXiv · 1609.08280

Measurement of Michel Parameters ($\bar\eta$, $\xi\kappa$) in the radiative leptonic decay of tau at Belle

The Belle Collaboration·A. Abdesselam·I. Adachi·K. Adamczyk·H. Aihara·S. Al Said·K. Arinstein·Y. Arita·D. M. Asner·T. Aso·H. Atmacan·V. Aulchenko·T. Aushev·R. Ayad·T. Aziz·V. Babu·I. Badhrees·S. Bahinipati·A. M. Bakich·A. Bala·Y. Ban·V. Bansal·E. Barberio·M. Barrett·W. Bartel·A. Bay·P. Behera·M. Belhorn·K. Belous·M. Berger·D. Besson·V. Bhardwaj·B. Bhuyan·J. Biswal·T. Bloomfield·S. Blyth·A. Bobrov·A. Bondar·G. Bonvicini·C. Bookwalter·C. Boulahouache·A. Bozek·M. Bračko·F. Breibeck·J. Brodzicka·T. E. Browder·E. Waheed·D. Červenkov·M. -C. Chang·P. Chang·Y. Chao·V. Chekelian·A. Chen·K. -F. Chen·P. Chen·B. G. Cheon·K. Chilikin·R. Chistov·K. Cho·V. Chobanova·S. -K. Choi·Y. Choi·D. Cinabro·J. Crnkovic·J. Dalseno·M. Danilov·N. Dash·S. Di Carlo·J. Dingfelder·Z. Doležal·D. Dossett·Z. Drásal·A. Drutskoy·S. Dubey·D. Dutta·K. Dutta·S. Eidelman·D. Epifanov·H. Farhat·J. E. Fast·M. Feindt·T. Ferber·A. Frey·O. Frost·B. G. Fulsom·V. Gaur·N. Gabyshev·S. Ganguly·A. Garmash·D. Getzkow·R. Gillard·F. Giordano·R. Glattauer·Y. M. Goh·P. Goldenzweig·B. Golob·D. Greenwald·M. Grosse Perdekamp·J. Grygier·O. Grzymkowska
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Abstract

We present the first measurement of the Michel parameters $\bar{\eta}$ and $\xi\kappa$ in the radiative leptonic decay of the $\tau$ lepton using 703 f$\mathrm{b}^{-1}$ of data collected with the Belle detector at the KEKB $e^+e^-$ collider. The Michel parameters are measured by an unbinned maximum likelihood fit to the kinematic information of $e^+e^-\rightarrow\tau^+\tau^-\rightarrow (\pi^+\pi^0 \bar{\nu})(l^-\nu\bar{\nu}\gamma)$ $(l=e$ or $\mu)$. The preliminary values of the measured Michel parameters are $\bar{\eta} = -2.0 \pm 1.5 \pm 0.8$ and $\xi\kappa = 0.6 \pm 0.4 \pm 0.2$, where the first error is statistical and the second is systematic.

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The Belle Collaboration, A. Abdesselam, I. Adachi, K. Adamczyk, H. Aihara, S. Al Said, K. Arinstein, Y. Arita, D. M. Asner, T. Aso, H. Atmacan, V. Aulchenko, T. Aushev, R. Ayad, T. Aziz, V. Babu, I. Badhrees, S. Bahinipati, A. M. Bakich, A. Bala, Y. Ban, V. Bansal, E. Barberio, M. Barrett, W. Bartel, A. Bay, P. Behera, M. Belhorn, K. Belous, M. Berger, D. Besson, V. Bhardwaj, B. Bhuyan, J. Biswal, T. Bloomfield, S. Blyth, A. Bobrov, A. Bondar, G. Bonvicini, C. Bookwalter, C. Boulahouache, A. Bozek, M. Bračko, F. Breibeck, J. Brodzicka, T. E. Browder, E. Waheed, D. Červenkov, M. -C. Chang, P. Chang, Y. Chao, V. Chekelian, A. Chen, K. -F. Chen, P. Chen, B. G. Cheon, K. Chilikin, R. Chistov, K. Cho, V. Chobanova, S. -K. Choi, Y. Choi, D. Cinabro, J. Crnkovic, J. Dalseno, M. Danilov, N. Dash, S. Di Carlo, J. Dingfelder, Z. Doležal, D. Dossett, Z. Drásal, A. Drutskoy, S. Dubey, D. Dutta, K. Dutta, S. Eidelman, D. Epifanov, H. Farhat, J. E. Fast, M. Feindt, T. Ferber, A. Frey, O. Frost, B. G. Fulsom, V. Gaur, N. Gabyshev, S. Ganguly, A. Garmash, D. Getzkow, R. Gillard, F. Giordano, R. Glattauer, Y. M. Goh, P. Goldenzweig, B. Golob, D. Greenwald, M. Grosse Perdekamp, J. Grygier, O. Grzymkowska. 2016-09-27. Measurement of Michel Parameters ($\bar\eta$, $\xi\kappa$) in the radiative leptonic decay of tau at Belle. https://arxiv.org/abs/1609.08280

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