scholarly journals QCD factorization of the four-lepton decay $$B^-\rightarrow \ell \bar{\nu }_\ell \ell ^{(\prime )} \bar{\ell }^{(\prime )}$$

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Martin Beneke ◽  
Philipp Böer ◽  
Panagiotis Rigatos ◽  
K. Keri Vos
Keyword(s):  
Branching Fraction ◽  
Branching Fractions ◽  
Decay Amplitude ◽  
Form Factors ◽  
Lepton Pairs ◽  
Intermediate Resonance ◽  
Lepton Decay ◽  
Four Leptons ◽  
Added Uncertainty ◽  
Inverse Moment

AbstractMotivated by the first search for the rare charged-current B decay to four leptons, $$\ell \bar{\nu }_\ell \ell ^{(\prime )} \bar{\ell }^{(\prime )}$$ ℓ ν ¯ ℓ ℓ ( ′ ) ℓ ¯ ( ′ ) , we calculate the decay amplitude with factorization methods. We obtain the $$B\rightarrow \gamma ^*$$ B → γ ∗ form factors, which depend on the invariant masses of the two lepton pairs, at leading power in an expansion in $$\Lambda _\mathrm{QCD}/m_b$$ Λ QCD / m b to next-to-leading order in $$\alpha _s$$ α s , and at $$\mathcal {O}(\alpha _s^0)$$ O ( α s 0 ) at next-to-leading power. Our calculations predict branching fractions of a few times $$10^{-8}$$ 10 - 8 in the $$\ell ^{(\prime )} \bar{\ell }^{(\prime )}$$ ℓ ( ′ ) ℓ ¯ ( ′ ) mass-squared bin up to $$q^2=1~$$ q 2 = 1 GeV$$^2$$ 2 with $$n_+q>3~$$ n + q > 3 GeV. The branching fraction rapidly drops with increasing $$q^2$$ q 2 . An important further motivation for this investigation has been to explore the sensitivity of the decay rate to the inverse moment $$\lambda _B$$ λ B of the leading-twist B meson light-cone distribution amplitude. We find that in the small-$$q^2$$ q 2 bin, the sensitivity to $$\lambda _B$$ λ B is almost comparable to $$B^- \rightarrow \mathrm {\ell }^- \bar{\nu }_{\mathrm {\ell }}\gamma $$ B - → ℓ - ν ¯ ℓ γ when $$\lambda _B$$ λ B is small, but with an added uncertainty from the light-meson intermediate resonance contribution. The sensitivity degrades with larger $$q^2$$ q 2 .

scholarly journals Rare Λb → nl+l− decays in the relativistic quark–diquark picture

2017 ◽  
Vol 32 (24) ◽  
pp. 1750125 ◽  
Author(s):  
R. N. Faustov ◽  
V. O. Galkin
Keyword(s):  
Momentum Transfer ◽  
Branching Fraction ◽  
Branching Fractions ◽  
Form Factors ◽  
Relativistic Effects

The form factors of the rare [Formula: see text] decays are calculated in the framework of the relativistic quark–diquark picture of baryons with the consistent account of the relativistic effects. Their momentum transfer squared dependence is determined explicitly in the whole accessible kinematical range. The decay branching fractions, forward–backward asymmetries and the fractions of longitudinally polarized dileptons are determined. The branching fraction of the rare [Formula: see text] decay are found to be [Formula: see text] and thus could be measured at the LHC. Prediction for the branching fraction of the rare radiative [Formula: see text] decay is also given.

The branching fraction calculations of Bc+ → ψ(2S)π+, Bc+ → J/ψK+ and Bc+ → J/ψDs+ decays relative to that of the Bc+ → J/ψπ+ mode

2018 ◽  
Vol 33 (08) ◽  
pp. 1850044
Author(s):  
Behnam Mohammadi
Keyword(s):  
Branching Fraction ◽  
Branching Fractions ◽  
Decay Amplitude ◽  
Weak Decay ◽  
Lhcb Collaboration ◽  
Tree Level ◽  
Final State ◽  
Factorization Approximation ◽  
Weak Annihilation ◽  
First Time

The weak decay of [Formula: see text] into [Formula: see text], [Formula: see text] and [Formula: see text] mesons, observed by LHCb collaboration for the first time, are calculated in the model which takes into account the “factorizable” contributions and “nonfactorizable” corrections. The decays of [Formula: see text] mesons into charmonia and light hadrons are expected to be well described by the factorization approximation. In the standard model, [Formula: see text], [Formula: see text] decays occur through only the tree-level diagrams and so there are no CP violation in these channels. The decay [Formula: see text] is expected to proceed mainly via a [Formula: see text] transition because the [Formula: see text] decay has identical final state and similar event topology, where it is chosen as the relative branching fraction channel. The ratio of branching fractions [Formula: see text] is of particular interest since the CKM matrix element is suppressed by a factor [Formula: see text], in which the [Formula: see text] occur through [Formula: see text] transition, but the dominant amplitude of the decay [Formula: see text] is a [Formula: see text] transition. The decay [Formula: see text] is examined by color-allowed, color-suppressed spectator and weak annihilation diagrams. The weak annihilation topology, in contrast to decays of other beauty hadrons, is not suppressed and can contribute significantly to the decay amplitude. Because of the [Formula: see text], [Formula: see text] and [Formula: see text] branching fractions are calculated relative to the [Formula: see text] decay, this decay mode is estimated separately, the ratio between them are [Formula: see text], [Formula: see text] and [Formula: see text], respectively, that are compatible with the experimental data.

scholarly journals Study of nonleptonic B(s)∗→ M1M2 (M = D,Ds,π,K) weak decays with factorization approach

2015 ◽  
Vol 30 (27) ◽  
pp. 1550162 ◽  
Author(s):  
Qin Chang ◽  
Pan-Pan Li ◽  
Xiao-Hui Hu ◽  
Lin Han
Keyword(s):  
Flavor Physics ◽  
Branching Fractions ◽  
Form Factors ◽  
Approximation Formula ◽  
Heavy Flavor ◽  
Transition Form ◽  
Factorization Approach ◽  
Decay Modes ◽  
Weak Decays ◽  
Belle Ii

Motivated by the experiments of heavy flavor physics at running LHC and upgrading SuperKEKB/Belle-II in the future, the nonleptonic [Formula: see text] [Formula: see text] weak decays are studied in this paper. The amplitudes are calculated with factorization approach, and the transition form factors [Formula: see text] are evaluated within BSW model. With the reasonable approximation [Formula: see text], our predictions of branching fractions are presented. Numerically, the CKM-favored tree-dominated [Formula: see text] and [Formula: see text] decays have the largest branching fractions of the order [Formula: see text], and hence will be firstly observed by forthcoming Belle-II experiment. However, most of the other decay modes have the branching fractions [Formula: see text] and thus are hardly to be observed soon. Besides, for the possible detectable [Formula: see text] decays with branching fractions [Formula: see text], some useful ratios, such as [Formula: see text], etc. are presented and discussed in detail.

scholarly journals Model-independent investigation of the RJ/ψ,ηc and ratios of decay widths of semileptonic Bc decays into a P-wave charmonium

2019 ◽  
Vol 34 (31) ◽  
pp. 1950195 ◽  
Author(s):  
Wei Wang ◽  
Ruilin Zhu
Keyword(s):  
Branching Fractions ◽  
Form Factors ◽  
P Wave ◽  
Experimental Measurements ◽  
Complementary Information ◽  
Independent Investigation ◽  
Lepton Flavor ◽  
Decay Widths ◽  
Model Independent ◽  
Standard Models

Experimental measurements of decay branching fractions of semitaunic and semimuonic [Formula: see text] into [Formula: see text] have challenged the lepton flavor universality in standard models with about two standard deviations. In this paper, we first investigate the unitary constraint on form factors of [Formula: see text] meson into [Formula: see text]-wave and [Formula: see text]-wave charmonium. Such constraint leads to the exploration of the [Formula: see text] and other ratios [Formula: see text], [Formula: see text], and [Formula: see text] in a model-independent way. These results together with future experimental measurements can be used to explore the lepton flavor universality in a more systematic way. In addition, we point out that the helicity-dependent ratios [Formula: see text] and [Formula: see text] can also provide complementary information.

scholarly journals ANALYSIS OF THE $B_q\to D_q(D_q^*)P$ AND $B_q\to D_q(D_q^*)V$ DECAYS WITHIN THE FACTORIZATION APPROACH IN QCD

2009 ◽  
Vol 24 (31) ◽  
pp. 5845-5860 ◽  
Author(s):  
K. AZIZI ◽  
R. KHOSRAVI ◽  
F. FALAHATI
Keyword(s):  
Experimental Data ◽  
Perturbative Qcd ◽  
Sum Rules ◽  
Branching Fraction ◽  
Form Factors ◽  
Transition Form ◽  
Qcd Sum Rules ◽  
Factorization Approach ◽  
Electroweak Penguin ◽  
Decay Widths

Using the factorization approach and considering the contributions of the current–current, QCD penguin and electroweak penguin operators at the leading approximation, the decay amplitudes and decay widths of [Formula: see text] and [Formula: see text] transitions, where q = u, d, s and P and V are pseudoscalar and vector mesons, are calculated in terms of the transition form factors of the Bq→Dq and [Formula: see text]. Having computed those form factors in three-point QCD sum rules, the branching fraction for these decays are also evaluated. A comparison of our results with the predictions of the perturbative QCD as well as the existing experimental data is presented.

Initial charm program on direct measurements of weak decay constant fDs and branching fraction B(Ds → μνμ) and prospect with high-precision

2020 ◽  
Vol 35 (35) ◽  
pp. 2030018
Author(s):  
C. C. Zhang
Keyword(s):  
High Precision ◽  
Decay Constant ◽  
Branching Fraction ◽  
Branching Fractions ◽  
Weak Decay ◽  
Precision Measurements ◽  
Direct Measurements

First direct measurements of the weak decay constant [Formula: see text] and the [Formula: see text] branching fractions to [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] at the BES experiments in 1990s are reviewed. Referring to the BESIII results of [Formula: see text] and branching fraction [Formula: see text] with best precision1 to date, prospect for challenge on precision measurements of [Formula: see text] and [Formula: see text] at BESIII is presented.

scholarly journals D * Polarization as an Additional Constraint on New Physics in the b → cτ ν ¯ τ Transition

Particles ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 193-207
Author(s):  
Mikhail A. Ivanov ◽  
Jürgen G. Körner ◽  
Pietro Santorelli ◽  
Chien-Thang Tran
Keyword(s):  
Experimental Data ◽  
Standard Model ◽  
Branching Fractions ◽  
Experimental Studies ◽  
Form Factors ◽  
Unknown Origin ◽  
New Physics ◽  
Constituent Quark Model ◽  
Tensor Operator ◽  
The Standard Model

Measurements of the branching fractions of the semileptonic decays B → D ( * ) τ ν ¯ τ and B c → J / ψ τ ν ¯ τ systematically exceed the Standard Model predictions, pointing to possible signals of new physics that can violate lepton flavor universality. The unknown origin of new physics realized in these channels can be probed using a general effective Hamiltonian constructed from four-fermion operators and the corresponding Wilson coefficients. Previously, constraints on these Wilson coefficients were obtained mainly from the experimental data for the branching fractions. Meanwhile, polarization observables were only theoretically studied. The situation has changed with more experimental data having become available, particularly those regarding the polarization of the tau and the D * meson. In this study, we discuss the implications of the new data on the overall picture. We then include them in an updated fit of the Wilson coefficients using all hadronic form factors from our covariant constituent quark model. The use of our form factors provides an analysis independent of those in the literature. Several new-physics scenarios are studied with the corresponding theoretical predictions provided, which are useful for future experimental studies. In particular, we find that under the one-dominant-operator assumption, no operator survives at 1 σ . Moreover, the scalar operators O S L and O S R are ruled out at 2 σ if one uses the constraint B ( B c → τ ν τ ) ≤ 10 % , while the more relaxed constraint B ( B c → τ ν τ ) ≤ 30 % still allows these operators at 2 σ , but only minimally. The inclusion of the new data for the D * polarization fraction F L D * reduces the likelihood of the right-handed vector operator O V R and significantly constrains the tensor operator O T L . Specifically, the F L D * alone rules out O T L at 1 σ . Finally, we show that the longitudinal polarization P L τ of the tau in the decays B → D * τ ν ¯ τ and B c → J / ψ τ ν ¯ τ is extremely sensitive to the tensor operator. Within the 2 σ allowed region, the best-fit value T L = 0.04 + i 0.17 predicts P L τ ( D * ) = − 0.33 and P L τ ( J / ψ ) = − 0.34 , which are at about 33% larger than the Standard Model (SM) prediction P L τ ( D * ) = − 0.50 and P L τ ( J / ψ ) = − 0.51 .

scholarly journals Charmed $$\Omega _c$$ weak decays into $$\Omega $$ in the light-front quark model

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Yu-Kuo Hsiao ◽  
Ling Yang ◽  
Chong-Chung Lih ◽  
Shang-Yuu Tsai
Keyword(s):  
Quark Model ◽  
Recent Observation ◽  
Branching Fractions ◽  
Form Factors ◽  
Weak Decay ◽  
Current Data ◽  
Light Front ◽  
Transition Form ◽  
Decay Modes ◽  
Weak Decays

AbstractMore than ten $$\Omega _c^0$$ Ω c 0 weak decay modes have been measured with the branching fractions relative to that of $$\Omega ^0_c\rightarrow \Omega ^-\pi ^+$$ Ω c 0 → Ω - π + . In order to extract the absolute branching fractions, the study of $$\Omega ^0_c\rightarrow \Omega ^-\pi ^+$$ Ω c 0 → Ω - π + is needed. In this work, we predict $${{\mathcal {B}}}_\pi \equiv {{\mathcal {B}}}(\Omega _c^0\rightarrow \Omega ^-\pi ^+)=(5.1\pm 0.7)\times 10^{-3}$$ B π ≡ B ( Ω c 0 → Ω - π + ) = ( 5.1 ± 0.7 ) × 10 - 3 with the $$\Omega _c^0\rightarrow \Omega ^-$$ Ω c 0 → Ω - transition form factors calculated in the light-front quark model. We also predict $${{\mathcal {B}}}_\rho \equiv {{\mathcal {B}}}(\Omega _c^0\rightarrow \Omega ^-\rho ^+)=(14.4\pm 0.4)\times 10^{-3}$$ B ρ ≡ B ( Ω c 0 → Ω - ρ + ) = ( 14.4 ± 0.4 ) × 10 - 3 and $${{\mathcal {B}}}_e\equiv {{\mathcal {B}}}(\Omega _c^0\rightarrow \Omega ^-e^+\nu _e)=(5.4\pm 0.2)\times 10^{-3}$$ B e ≡ B ( Ω c 0 → Ω - e + ν e ) = ( 5.4 ± 0.2 ) × 10 - 3 . The previous values for $${{\mathcal {B}}}_\rho /{{\mathcal {B}}}_\pi $$ B ρ / B π have been found to deviate from the most recent observation. Nonetheless, our $${{\mathcal {B}}}_\rho /{{\mathcal {B}}}_\pi =2.8\pm 0.4$$ B ρ / B π = 2.8 ± 0.4 is able to alleviate the deviation. Moreover, we obtain $${{\mathcal {B}}}_e/{{\mathcal {B}}}_\pi =1.1\pm 0.2$$ B e / B π = 1.1 ± 0.2 , which is consistent with the current data.

scholarly journals Recent results from BABAR

2020 ◽  
Vol 235 ◽  
pp. 04001
Author(s):  
J. William Gary
Keyword(s):  
Data Collection ◽  
Direct Measurement ◽  
Decay Channel ◽  
Branching Fraction ◽  
Branching Fractions ◽  
Babar Collaboration ◽  
Lepton Number ◽  
Lepton Flavor ◽  
The Third

The BABAR Collaboration at SLAC continues to produce a wide variety of publications on interesting and unique topics despite having ceased data-collection operations more than 10 years ago. Presented here are the results of three recent studies. The first is on the direct measurement of the B± → K± X(3872) branching fraction, allowing the first determination of the branching fractions of the exotic X(3872) charmonium state. The second is a publication on the first observation of the D0 → K−π+e+e− branching fraction. The third is on searches for lepton flavor and lepton number violating decays in D0 meson decays, resulting in improvements over existing limits by factors that vary from 20 to almost 800 depending on the D0 decay channel.

Sign in / Sign up

Export Citation Format

Share Document