53 research outputs found
Explaining the and anomalies with vector leptoquarks
Recently the factories BaBar and Belle as well as the LHCb experiment
have reported several anomalies in the semileptonic meson decays such as
and etc. We investigate these deviations by considering
the vector leptoquarks relevant for both and transitions. The leptoquark parameter space is constrained by using the
experimentally measured branching ratios of , and processes. Using the
constrained leptoquark couplings, we compute the branching ratios,
forward-backward asymmetries, and polarization parameters in the
processes. We find that the vector
leptoquarks can explain both and anomalies simultaneously.
Furthermore, we study the rare leptonic decay
processes in this model.Comment: 33 pages, 14 figures, typos correcte
Perturbative Bottom-up Approach for Neutrino Mass Matrix in Light of Large \theta_{13} and Role of Lightest Neutrino Mass
We discuss the role of lightest neutrino mass (m_0) in the neutrino mass
matrix, defined in a flavor basis, through a bottom-up approach using the
current neutrino oscillation data. We find that if m_0 < 10^{-3} eV, then the
deviation \delta M_\nu in the neutrino mass matrix from a tree-level, say
tribimaximal neutrino mass matrix, does not depend on m_0. As a result \delta
M_\nu's are exactly predicted in terms of the experimentally determined
quantities such as solar and atmospheric mass squared differences and the
mixing angles. On the other hand for m_0 \gsim 10^{-3} eV, \delta M_\nu
strongly depends on m_0 and hence can not be determined within the knowledge of
oscillation parameters alone. In this limit, we provide an exponential
parameterization for \delta M_\nu for all values of m_0 such that it can
factorize the m_0 dependency of \delta M_\nu from rest of the oscillation
parameters. This helps us in finding \delta M_\nu as a function of the solar
and atmospheric mass squared differences and the mixing angles for all values
of m_0. We use this information to build up a model of neutrino masses and
mixings in a top-down scenario which can predict large \theta_{13}
perturbatively.Comment: 26 pages, 42 eps figures, revtex (references are added, more
discussions are added in section-III
Implications of light Z′ on semileptonic B(Bs)→T{K2*(1430)(f2′(1525))}ℓ+ℓ− decays at large recoil
We probe the rare semileptonic decays B(s)→K2∗(1430)(f2′(1525))+- proceeding via b→s transition in the presence of a light Z′ boson. We employ the presence of an additional vector-type interaction and constrain the new physics coupling parameter using the existing experimental measurements on RK and RK∗ observables. To understand the sensitivity of the new physics coupling, we investigate the impact of this coupling on various physical observables such as differential branching ratio, the forward-backward asymmetry, the lepton polarization asymmetry, the angular observable P5′, and the lepton universality parameters such as the ratio of the branching ratio Rf2′(K2∗) and some important Q parameters of B(s)→K2∗(1430)(f2′(1525))+- processes at large recoil. We find some noticeable differences of the observables in the presence of light Z′ contribution. © 2021 authors. Published by the American Physical Society
Delving into the , processes
To shed light on the indirect search for new physics beyond the standard
model, the long standing discrepancies between the theory and experiment
mediated by FCNC quark level transitions set an ideal
testing ground. Though the very recent measurements of and are
consistent with the standard model, still the excitements remain on the
measurements of LHCb experiment with the observables which has deviations at the level of .
Additionally, standard deviation of and ,
respectively for in and the branching
ratio in processes are observed. Inspired by these
discrepancies, we work out the constraints on the new physics coupling
parameters in the presence of a non-universal model. We then probe the
exclusive leptonic decay channels , induced by the
neutral current transition . We find that the
variation of the observables, such as, branching ratio, forward-backward
asymmetry, lepton polarization asymmetry, and the very sensible observable, so
called non-universality observables for LFV decays display the sensitivity of
new physics. In this analysis. we estimate above mentioned observables that
could shed light on the window of new physics in the near future.Comment: I have updated the title of the paper. Also I have added few
references and changed the title of the image
Search for lepton-flavor-violating tau-lepton decays to ℓγ at Belle
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, B(τ± → μ±γ) ≤ 4.2 × 10−8 and B(τ± → e±γ) ≤ 5.6 × 10−8, are set at 90% confidence level. [Figure not available: see fulltext.]. © 2021, The Author(s)
An improved search for the electric dipole moment of the τ lepton
We report a measurement of the electric dipole moment of the τ lepton (dτ) using an 833 fb−1 data sample collected near the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e+e− collider. Using an optimal observable method, we obtain the real and imaginary parts of dτ as Re(dτ) = (−0.62 ± 0.63) × 10−17ecm and Im(dτ) = (−0.40 ± 0.32) × 10−17ecm, respectively. These results are consistent with null electric dipole moment at the present level of experimental sensitivity and improve the sensitivity by about a factor of three. [Figure not available: see fulltext.] © 2022, The Author(s)
Measurement of branching fractions and search for CP violation in D 0 → π + π − η, D 0 → K + K − η, and D 0 → ϕη at Belle
We measure the branching fractions and CP asymmetries for the singly Cabibbo-suppressed decays D0 → π+π−η, D0 → K+K−η, and D0 → ϕη, using 980 fb−1 of data from the Belle experiment at the KEKB e+e− collider. We obtainB(D0→π+π−η)=[1.22±0.02(stat)±0.02(syst)±0.03(Bref)]×10−3,B(D0→K+K−η)=[1.80−0.06+0.07(stat)±0.04(syst)±0.05(Bref)]×10−4,B(D0→ϕη)=[1.84±0.09(stat)±0.06(syst)±0.05(Bref)]×10−4, where the third uncertainty (Bref) is from the uncertainty in the branching fraction of the reference mode D0 → K−π+η. The color-suppressed decay D0 → ϕη is observed for the first time, with very high significance. The results for the CP asymmetries areACP(D0π+π−η)=[0.9±1.2(stat)±0.5(syst)]%,ACP(D0→K+K−η)=[−1.4±3.3(stat)±1.1(syst)]%,ACP(D0→ϕη)=[−1.9±4.4(stat)±0.6(syst)]%. The results for D0 → π+π−η are a significant improvement over previous results. The branching fraction and ACP results for D0 → K+K−η, and the ACP result for D0 → ϕη, are the first such measurements. No evidence for CP violation is found in any of these decays. [Figure not available: see fulltext.] © 2021, The Author(s)
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