ZBORNIK POVZETKOV - Soft Matter Laboratory

Search for new physics in B → D ∗ τ ¯ντ decay
Svjetlana Fajfer a,b1 , Jernej F. Kamenik a,b2 and Ivan Niˇsandˇzić a3
a J. Stefan Institute, Jamova 39, P. O. Box 3000, 1001 Ljubljana, Slovenia
b Department of Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
Abstract
B physics offers important tests of the Standard Model at low energies. Recently, BaBar
observed significant deviations from the Standard Model expectations in the semileptonic B →
D (∗) τ ¯ντ decays. Also, the measured leptonic B → τν branching fraction also deviates from CKM
unitarity predictions. Motivated by these results we investigate the most general set of lowest
dimensional effective operators leading to modifications of b → c(u)τν transitions. Allowing for
general flavor violation, we find that among possible higher dimensional operators,the new contributions
from right-right vector and right-left scalar quark currents provide viable explanations
of the measured anomalies. In addition, we identify a number of B → D ∗ τ ¯ντ transition observables
that can discriminate among the various effective operators contributions. They are the
differential decay rate, longitudinal D ∗ polarization fraction, D ∗ opening angle asymmetry and
the τ helicity asymmetry.
References
[1] S.Fajfer, J.F.Kamenik and I.Nisandzic, arXiv:1203.2654 [hep-ph], Phys.Rev. D85 (2012) 094025
[2] S.Fajfer, J.F.Kamenik, I.Nisandzic and J.Zupan, arXiv:1206.1872 [hep-ph].
[3] BaBar Collaboration (J.P. Lees et al.), arXiv:1205.5442 [hep-ex], Phys. Rev. Lett. 109, 101802
(2012)
1 svjetlana.fajfer@ijs.si
2 jernej.kamenik@ijs.si
3 ivan.nisandzic@ijs.si
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