Left-handed Z′ and Z FCNC quark couplings facing new b → sμ+μ− data
By Andrzej Buras, J. Girrbach. 2013
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A bstractIn view of the recent improved data on Bs,d → μ+μ− and Bd → K*μ+μ− we revisit two simple New Physics (NP) scenarios analyzed by us last year in which new FCNC currents in b → sμ+μ− transitions are mediated either entirely by a neutral heavy gauge boson Z′ with purely left-handed complex couplings $ \Delta_L^{qb}\left( {{Z^{\prime }}} \right)\left( {q=d,s} \right) $ and real couplings to muons $ \Delta_A^{{\mu \overline{\mu}}}\left( {{Z^{\prime }}} \right) $ and $ \Delta_V^{{\mu \overline{\mu}}}\left( {Z\prime } \right) $ or the SM Z boson with left-handed complex couplings $ \Delta_L^{qb }(Z) $. We demonstrate how the reduced couplings, the couplings in question divided by MZ′ or MZ, can be determined by future ΔF = 2 and b → sμ+μ− observables up to sign ambiguities. The latter do not affect the correlations between various observables that can test these NP scenarios. We present the results as functions of $ {C_{{{B_q}}}}={{{\varDelta Mq}} \left/ {{{{{\left( {\varDelta Mq} \right)}}_{\mathrm{SM}}}}} \right.},{S_{{\psi \phi }}} $ and $ {S_{{\psi {K_S}}}} $ which should be precisely determined in this decade. We calculate the violation of the CMFV relation between $ \mathcal{B}\left( {{B_{s,d }}\to {\mu^{+}}{\mu^{-}}} \right) $ and ΔMs,d in these scenarios. We find that the data on Bs,d → μ+μ− from CMS and LHCb can be reproduced in both scenarios but in the case of Z, ΔMs and Sψϕ have to be very close to their SM values. As far as Bd → K*μ+μ− anomalies are concerned the Z′ scenario can significantly soften these anomalies while the Z boson fails badly because of the small vector coupling to muons. We also point out that recent proposals of explaining these anomalies with the help of a real Wilson coefficient $ C_9^{\mathrm{NP}} $ implies uniquely an enhancement of ΔMs with respect to its SM value, while a complex $ C_9^{\mathrm{NP}} $ allows for both enhancement and suppression of ΔMs and simultaneously novel CP-violating effects. Correlations between b → sμ+μ− and $ b\to s\nu \overline{\nu} $ observables in these scenarios are emphasized. We also discuss briefly scenarios in which the Z′ boson has right-handed FCNC couplings. In this context we point out a number of correlations between angular observables measured in Bd → K*μ+μ− that arise in the absence of new CP-violating phases in scenarios with only left-handed or right-handed couplings or scenarios in which left-handed and right-handed couplings are equal to each other or differ by sign.
Subfields: Artificial Intelligence, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/1f87257046adca7f853ce0d33ea1c7353ce7dfae
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Citations in the corpus
- An explicit Z′-boson explanation of the B → K∗μ+μ− anomaly (2013, background): “Since the SU(2)L relation (GdL)11 = (GuL)11 is broken by small mixing angles only, our expression for ∆CKM agrees with the result presented recently in [10].”
- Patterns of flavour violation in models with vector-like quarks (2016, background): “The choice of the particular symmetry group U(1)Lμ−Lτ [13, 14] is phenomenologically motivated by the fact that it allows in a simple manner to address successfully the LHCb anomalies [9, 15], while being anomaly-free and containing less parameters than general Z ′ models [16].”
- Resonances gone topsy turvy - the charm of QCD or new physics in b→sℓ+ℓ−? (2014, background): “The possibility of ∆C ′ 9 ' 1, driven by high q(2) and B → Kμμ, was suggested in [33] and later by [34, 40, 41].”