Measurement of the Ratio of Branching Fractions B([bar over B][superscript 0] → D[superscript *+]τ[superscript -][bar over ν][subscript τ])/B([bar over B][superscript 0] → D[superscript *+]μ[superscript -][bar over ν][subscript μ])
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PhysRevLett.115.111803.pdf
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Author(s)
Aaij, R.
Adeva, B.
Adinolfi, M.
Affolder, A.
Ajaltouni, Z.
Akar, S.
Albrecht, J.
Alessio, F.
Alexander, M.
Ali, S.
Date Issued
September 2015
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Aaij, R., et al. "Measurement of the Ratio of Branching Fractions B([bar over B][superscript 0] → D[superscript *+]τ[superscript -][bar over ν][subscript τ])/B([bar over B][superscript 0] → D[superscript *+]μ[superscript -][bar over ν][subscript μ])." Phys. Rev. Lett. 115, 111803 (September 2015). © 2015 CERN, for the LHCb Collaboration
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Final published version
Abstract
The branching fraction ratio R(D*) ≡ B([bar over B][superscript 0] → D[superscript *+]τ[superscript -][bar over ν][subscript τ])/B([bar over B][superscript 0] → D[superscript *+]μ[superscript -][bar over ν][subscript μ]) is measured using a sample of proton-proton collision data corresponding to 3.0 fb[superscript -1] of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ[superscript -] → μ[superscript -][bar over ν][subscript μ]ν[subscript τ]. The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate [bar over B][superscript 0] decays gives R(D*) = 0.336 ± 0.027(stat) ± 0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the standard model.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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DOI of Published Version
http://dx.doi.org/10.1103/PhysRevLett.115.111803
