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 Searching for charged lepton flavor violation at ep colliders

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Stefan Antusch ◽  
A. Hammad ◽  
Ahmed Rashed
Keyword(s):  
Standard Model ◽  
Charged Lepton ◽  
Neutral Current ◽  
Effective Theory ◽  
Theory Approach ◽  
Lepton Flavor Violation ◽  
Lepton Flavor ◽  
Flavor Violation ◽  
The Standard Model ◽  
Order Of Magnitude

Abstract We investigate the sensitivity of electron-proton (ep) colliders for charged lepton flavor violation (cLFV) in an effective theory approach, considering a general effective Lagrangian for the conversion of an electron into a muon or a tau via the effective coupling to a neutral gauge boson or a neutral scalar field. For the photon, the Z boson and the Higgs particle of the Standard Model, we present the sensitivities of the LHeC for the coefficients of the effective operators, calculated from an analysis at the reconstructed level. As an example model where such flavor changing neutral current (FCNC) operators are generated at loop level, we consider the extension of the Standard Model by sterile neutrinos. We show that the LHeC could already probe the LFV conversion of an electron into a muon beyond the current experimental bounds, and could reach more than an order of magnitude higher sensitivity than the present limits for LFV conversion of an electron into a tau. We discuss that the high sensitivities are possible because the converted charged lepton is dominantly emitted in the backward direction, enabling an efficient separation of the signal from the background.

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 Search for lepton flavor violation in the Higgs boson decay at a linear collider

2004 ◽  
Vol 599 (1-2) ◽  
pp. 83-91 ◽  
Author(s):  
Shinya Kanemura ◽  
Koichi Matsuda ◽  
Toshihiko Ota ◽  
Tetsuo Shindou ◽  
Eiichi Takasugi ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Linear Collider ◽  
Lepton Flavor Violation ◽  
Lepton Flavor ◽  
Flavor Violation

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 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.

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