arXiv · 2311.05224
Measurement of the $D^{*}$ longitudinal polarization in $B^0\to D^{*-}\tau^{+}\nu_{\tau}$ decays
Abstract
The longitudinal polarization fraction of the $D^{*}$ meson is measured in $B^0\to D^{*-}\tau^{+}\nu_{\tau}$ decays, where the $\tau$ lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of 5 fb$^{-1}$. The $D^{*}$ polarization fraction $F_{L}^{D^{*}}$ is measured in two $q^{2}$ regions, below and above 7 GeV$^{2}/c^{4}$, where $q^{2}$ is defined as the squared invariant mass of the $\tau\nu_{\tau}$ system. The $F_{L}^{D^{*}}$ values are measured to be $0.52 \pm 0.07 \pm 0.04$ and $0.34 \pm 0.08 \pm 0.02$ for the lower and higher $q^{2}$ regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole $q^{2}$ range is: $$F_{L}^{D^{*}} = 0.41 \pm 0.06 \pm 0.03.$$ These results are compatible with the Standard Model predictions.
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LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, B. Adeva, M. Adinolfi, P. Adlarson, H. Afsharnia, C. Agapopoulou, C. A. Aidala, Z. Ajaltouni, S. Akar, K. Akiba, P. Albicocco, J. Albrecht, F. Alessio, M. Alexander, A. Alfonso Albero, Z. Aliouche, P. Alvarez Cartelle, R. Amalric, S. Amato, J. L. Amey, Y. Amhis, L. An, L. Anderlini, M. Andersson, A. Andreianov, P. Andreola, M. Andreotti, D. Andreou, D. Ao, F. Archilli, S. Arguedas Cuendis, A. Artamonov, M. Artuso, E. Aslanides, M. Atzeni, B. Audurier, D. Bacher, I. Bachiller Perea, S. Bachmann, M. Bachmayer, J. J. Back, A. Bailly-reyre, P. Baladron Rodriguez, V. Balagura, W. Baldini, J. Baptista de Souza Leite, M. Barbetti, I. R. Barbosa, R. J. Barlow, S. Barsuk, W. Barter, M. Bartolini, F. Baryshnikov, J. M. Basels, G. Bassi, B. Batsukh, A. Battig, A. Bay, A. Beck, M. Becker, F. Bedeschi, I. B. Bediaga, A. Beiter, S. Belin, V. Bellee, K. Belous, I. Belov, I. Belyaev, G. Benane, G. Bencivenni, E. Ben-Haim, A. Berezhnoy, R. Bernet, S. Bernet Andres, D. Berninghoff, H. C. Bernstein, C. Bertella, A. Bertolin, C. Betancourt, F. Betti, J. Bex, Ia. Bezshyiko, J. Bhom, L. Bian, M. S. Bieker, N. V. Biesuz, P. Billoir, A. Biolchini, M. Birch, F. C. R. Bishop, A. Bitadze, A. Bizzeti, M. P. Blago, T. Blake, F. Blanc. 2023-11-09. Measurement of the $D^{*}$ longitudinal polarization in $B^0\to D^{*-}\tau^{+}\nu_{\tau}$ decays. https://doi.org/10.1103/physrevd.110.092007
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