Test of lepton flavor universality and search for lepton flavor violation in $B \rightarrow K\ell \ell$ decays

Choudhury, S.; Sandilya, S.; Trabelsi, K.; Giri, A.; Aihara, H.; Al Said, S.; Asner, D.M.; Atmacan, H.; Aulchenko, V.; Aushev, T.

doi:10.1007/JHEP03(2021)105

Test of lepton flavor universality and search for lepton flavor violation in $B \rightarrow K\ell \ell$ decays

BELLE

Collaboration

•

S. Choudhury
(
- Indian Inst. Tech., Hyderabad
)

Aug 5, 2019

24 pages

Published in:

JHEP 03 (2021) 105

Published: Mar 10, 2021

e-Print:

1908.01848 [hep-ex]

DOI:

10.1007/JHEP03(2021)105

PDG:

{{\mathit B}^{+}}

\rightarrow

{{\mathit K}^{+}}{{\mathit \mu}^{+}}{{\mathit \mu}^{-}}

Report number:

BELLE-CONF-1904,
Belle Preprint 2020-11,
KEK Preprint 2020-12

Experiments:

KEK-BF-BELLE

View in:

reference search282 citations

Citations per year

Abstract: (Springer)

We present measurements of the branching fractions for the decays B → Kμ

^{+}

μ

^{−}

and B → Ke

^{+}

e

^{−}

, and their ratio (R

_{K}

), using a data sample of 711 fb

^{−1}

that contains 772 × 10

^{6} B\overline{B}

events. The data were collected at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e

^{+}

e

^{−}

collider. The ratio R

_{K}

is measured in five bins of dilepton invariant-mass-squared (q

^{2}

): q

^{2}

∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV

^{2}

/c

^{4}

, along with the whole q

^{2}

region. The R

_{K}

value for q

^{2}

∈ (1.0, 6.0) GeV

^{2}

/c

^{4}

is

{1.03}_{-0.24}^{+0.28}

± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for R

_{K}

are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q

^{2}

bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q

^{2}

∈ (1.0, 6.0) GeV

^{2}

/c

^{4}

bin in the mode with muon final states. The measured differential branching fractions,

d\mathrm{\mathcal{B}}

/dq

^{2}

, are consistent with theoretical predictions for charged B decays, while the corresponding values are below the expectations for neutral B decays. We have also searched for lepton-flavor-violating B → Kμ

^{±}

e

^{∓}

decays and set 90% confidence-level upper limits on the branching fraction in the range of 10

^{−8}

for B

^{+}

→ K

^{+}

μ

^{±}

e

^{∓}

, and B

^{0}

→ K

^{0}

μ

^{±}

e

^{∓}

modes.[graphic not available: see fulltext]

Note:

18 pages, 7 figures

FCNC Interaction
Flavor physics
Flavour Changing Neutral Currents
B physics
e+-e− Experiments
electron positron: annihilation
electron positron: colliding beams
B: pair production
B: semileptonic decay
muon: pair production

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Test of lepton flavor universality and search for lepton flavor violation in B→KℓℓB \rightarrow K\ell \ellB→Kℓℓ decays

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Test of lepton flavor universality and search for lepton flavor violation in $B \rightarrow K\ell \ell$ decays