scholarly journals Test of lepton flavor universality and search for lepton flavor violation in B → Kℓℓ decays

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
S. Choudhury ◽  
◽  
S. Sandilya ◽  
K. Trabelsi ◽  
A. Giri ◽  
...  
Keyword(s):  
Branching Fraction ◽  
Branching Fractions ◽  
Final States ◽  
Lepton Flavor Violation ◽  
Dilepton Invariant Mass ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Belle Detector ◽  
Upper Limits ◽  
Theoretical Predictions

Abstract We present measurements of the branching fractions for the decays B → Kμ+μ− and B → Ke+e−, and their ratio (RK), using a data sample of 711 fb−1 that contains 772 × 106$$ B\overline{B} $$ B 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 RK is measured in five bins of dilepton invariant-mass-squared (q2): q2 ∈ (0.1, 4.0), (4.00, 8.12), (1.0, 6.0), (10.2, 12.8) and (> 14.18) GeV2/c4, along with the whole q2 region. The RK value for q2 ∈ (1.0, 6.0) GeV2/c4 is $$ {1.03}_{-0.24}^{+0.28} $$ 1.03 − 0.24 + 0.28 ± 0.01. The first and second uncertainties listed are statistical and systematic, respectively. All results for RK are consistent with Standard Model predictions. We also measure CP-averaged isospin asymmetries in the same q2 bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the q2 ∈ (1.0, 6.0) GeV2/c4 bin in the mode with muon final states. The measured differential branching fractions, $$ d\mathrm{\mathcal{B}} $$ d ℬ /dq2, 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 B0 → K0μ±e∓ modes.

scholarly journals LEPTON FLAVOR VIOLATION IN INVERSE SEESAW MODEL

2013 ◽  
Vol 28 (38) ◽  
pp. 1350151 ◽  
Author(s):  
KE-SHENG SUN ◽  
TAI-FU FENG ◽  
GUO-HUI LUO ◽  
XIU-YI YANG ◽  
JIAN-BIN CHEN
Keyword(s):  
Large Scale ◽  
Branching Ratio ◽  
Mass Term ◽  
Lepton Flavor Violation ◽  
Neutrino Mixing ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Conversion Rates ◽  
Upper Limits ◽  
Wide Range

We analyze the lepton flavor violation processes μ-e conversion, li→ljγ and li→3lj in framework of the Standard Model (SM) extended with inverse seesaw mechanism, as a function of [Formula: see text] that parametrizes the departure from unitary of the light neutrino mixing sub-matrix [Formula: see text]. In a wide range of [Formula: see text], the predictions on the μ-e conversion rates and the branching ratio of μ→eγ are sizeable to be compatible with the experimental upper limits or future experimental sensitivities. For large scale of [Formula: see text], the predictions on branching ratios of other lepton flavor processes can also reach the experimental upper limits or future experimental sensitivities. The value of [Formula: see text] depends on the determinant of the Majorana mass term Mμ. Finally, searching for lepton flavor violation processes in experiment provides us more opportunities for the searches of seesaw nature of the neutrino masses.

scholarly journals lα → 3lβ in minimal R-symmetric supersymmetric Standard Model

2019 ◽  
Vol 35 (04) ◽  
pp. 1950359
Author(s):  
Ke-Sheng Sun ◽  
Jian-Bin Chen ◽  
Hai-Bin Zhang ◽  
Sheng-Kai Cui
Keyword(s):  
Standard Model ◽  
Supersymmetric Standard Model ◽  
Mass Matrix ◽  
Research Field ◽  
Beyond The Standard Model ◽  
Lepton Flavor Violation ◽  
Decay Channels ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Theoretical Predictions

Lepton flavor violation decays are channels which may lead to fundamental discoveries in the forthcoming years and this makes it an exciting research field for beyond the Standard Model (SM) searches. In this work, we present an analysis of the lepton flavor violation decays [Formula: see text] in Minimal R-symmetric Supersymmetric Standard Model. The prediction for [Formula: see text] depends on the off-diagonal entries of the slepton mass matrix. The contributions to Wilson coefficients can be classified into Higgs penguins, photon penguins, Z penguins and box diagrams. It shows the contribution from Z penguins dominates the predictions for [Formula: see text], and the contributions from Higgs penguins and box diagrams play different roles in different decay channels. The theoretical predictions for [Formula: see text] can reach the future experimental limits, and the channels are very promising to be observed in near future experiment.

scholarly journals Two-loop radiative seesaw, muon g − 2, and τ-lepton-flavor violation with DM constraints

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Chuan-Hung Chen ◽  
Takaaki Nomura
Keyword(s):  
Cross Sections ◽  
Branching Ratio ◽  
Scalar Coupling ◽  
Lepton Flavor Violation ◽  
Gauge Bosons ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Upper Limits ◽  
Relic Density ◽  
Scattering Cross Sections

Abstract The quartic scalar coupling λ5 term, which violates the lepton-number by two units in the Ma-model, is phenomenologically small when the model is applied to the lepton-flavor violation (LFV) processes. In order to dynamically generate the λ5 parameter through quantum loop effects and retain the dark matter (DM) candidate, we extend the Ma-model by adding a Z2-odd vector-like lepton doublet and a Z2-even Majorana singlet. With the new couplings to the Higgs and gauge bosons, the observed DM relic density can be explained when the upper limits from the DM-nucleon scattering cross sections are satisfied. In addition to the neutrino data and LFV constraints, it is found that the DM relic density can significantly exclude the free parameter space. Nevertheless, the resulting muon g − 2 mediated by the inert charged-Higgs can fit the 4.2σ deviation between the experimental measurement and the SM result, and the branching ratio for τ → μγ can be as large as the current upper limit when the rare μ → (eγ, 3e) decays are suppressed. In addition, it is found that the resulting BR(τ → μρ) can reach the sensitivity of Belle II with an integrated luminosity of 50 ab−1.

scholarly journals Probing charged lepton flavor violation with axion-like particles at Belle II

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Kingman Cheung ◽  
Abner Soffer ◽  
Zeren Simon Wang ◽  
Yu-Heng Wu
Keyword(s):  
Charged Lepton ◽  
Branching Fractions ◽  
Coupling Constants ◽  
Decay Length ◽  
Lepton Flavor Violation ◽  
Tau Decays ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Belle Ii ◽  
Displaced Vertex

Abstract We study charged lepton flavor violation associated with a light leptophilic axion-like particle (ALP), X, at the B-factory experiment Belle II. We focus on production of the ALP in the tau decays τ → Xl with l = e, μ, followed by its decay via X → l−l+. The ALP can be either promptly decaying or long-lived. We perform Monte-Carlo simulations, recasting a prompt search at Belle for lepton-flavor-violating τ decays, and propose a displaced-vertex (DV) search. For both types of searches, we derive the Belle II sensitivity reaches in both the product of branching fractions and the ALP coupling constants, as functions of the ALP mass and lifetime. The results show that the DV search exceeds the sensitivity reach of the prompt search to the relevant branching fractions by up to about a factor of 40 in the long decay length regime.

scholarly journals Search for lepton flavor violation at future lepton colliders

2017 ◽  
Vol 32 (24) ◽  
pp. 1750127 ◽  
Author(s):  
Gi-Chol Cho ◽  
Hanako Shimo
Keyword(s):  
Electron Beam ◽  
Linear Collider ◽  
International Linear Collider ◽  
Lepton Flavor Violation ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Upper Limits ◽  
Lepton Colliders ◽  
Order Of Magnitude ◽  
Fermi Contact

Lepton flavor violating (LFV) processes, [Formula: see text] and [Formula: see text] ([Formula: see text] or [Formula: see text]), via four-Fermi contact interactions at future International Linear Collider (ILC) are studied. Taking account of previous experimental results of LFV processes [Formula: see text] and [Formula: see text], we find that the upper limits on the LFV parameters for [Formula: see text] could be improved at the ILC experiment using the polarized electron beam. The improvement of the upper limits could be nearly an order of magnitude as compared to previous ones.

scholarly journals BES RESULTS ON J/ψ DECAYS AND CHARMONIUM TRANSITIONS

2005 ◽  
Vol 20 (02n03) ◽  
pp. 445-454 ◽  
Author(s):  
◽  
FREDERICK A. HARRIS
Keyword(s):  
Mass Spectrum ◽  
Invariant Mass ◽  
Branching Fraction ◽  
Branching Fractions ◽  
Invariant Mass Spectrum ◽  
Pole Position ◽  
Hadronic Decays ◽  
Final States ◽  
S Wave ◽  
Upper Limits

Results are reported based on samples of 58 million J/ψ and 14 million ψ(2S) decays obtained by the BESII experiment. Improved branching fraction measurements are determined, including branching fractions for J/ψ→π+π-π0, ψ(2S)→π0J/ψ, ηJ/ψ, π0π0J/ψ, anything J/ψ, and ψ(2S)→γχc1, γχc2→γγJ/ψ. The decay J/ψ→ωπ+π- is studied. At low ππ mass, a large, broad peak due to the σ is observed, and its pole position is determined. Results are presented on ψ(2S) and J/ψ hadronic decays to [Formula: see text] and [Formula: see text] final states. No significant Θ(1540) signal, the pentaquark candidate, is observed, and upper limits are set. An enhancement near the mp+MΛ mass threshold is observed in the [Formula: see text] invariant mass spectrum from [Formula: see text] decays. It can be fit with an S-wave Breit-Wigner resonance with a mass m=2075±12 ( stat )±5 ( syst ) MeV and a width of Γ=90±35 ( stat )±9 ( syst ) MeV .

scholarly journals A SEARCH FOR LEPTON FLAVOR VIOLATION IN TAU DECAYS ATBABAR

2005 ◽  
Vol 20 (15) ◽  
pp. 3343-3345
Author(s):  
◽  
OLGA IGONKINA
Keyword(s):  
Background Level ◽  
Lepton Flavor Violation ◽  
Tau Decays ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
Upper Limit ◽  
Upper Limits

We present a recent BABAR search for lepton flavor violation in tau decays. The search for τ → ℓℓℓ(ℓ = e, μ) decays is based on a data sample of 91.6 fb-1. No signal is found in any of six channels and 90% CL upper limits are set in the range of (1 - 3) × 10-7. The search for τ → μγ decay is done with a 63 fb-1data sample. The number of observed events is consistent with expected background level and a preliminary upper limit is set at 2 × 10-6at 90% CL.

scholarly journals Search for lepton-flavor-violating tau-lepton decays to ℓγ at Belle

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
◽  
K. Uno ◽  
K. Hayasaka ◽  
K. Inami ◽  
I. Adachi ◽  
...  
Keyword(s):  
Standard Model ◽  
Charged Lepton ◽  
Branching Fractions ◽  
New Physics ◽  
Lepton Flavor Violation ◽  
Full Data ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
The Standard Model ◽  
Lepton Decays

Abstract Charged lepton flavor violation is forbidden in the Standard Model but possible in several new physics scenarios. In many of these models, the radiative decays τ± → ℓ±γ (ℓ = e, μ) are predicted to have a sizeable probability, making them particularly interesting channels to search at various experiments. An updated search via τ± → ℓ±γ using full data of the Belle experiment, corresponding to an integrated luminosity of 988 fb−1, is reported for charged lepton flavor violation. No significant excess over background predictions from the Standard Model is observed, and the upper limits on the branching fractions, $$ \mathcal{B} $$ B (τ± → μ±γ) ≤ 4.2 × 10−8 and $$ \mathcal{B} $$ B (τ± → e±γ) ≤ 5.6 × 10−8, are set at 90% confidence level.

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