Large off-shell effects in the 
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 contribution to 
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Yaouanc, A. Le; Leroy, J. P.; Roudeau, P.

doi:10.1103/physrevd.99.073010

“…[ results on light-lepton decays, Light-Cone Sum Rules, and lattice inputs show very little dispersion in the predictions for R D and R D * [94]. These predictions do not take into account the width of the D * -meson, whose effect is currently under investigation and could have a noticeable impact of a few percent on the measurement of R D * [95,96].…”

Section: Standard Model Predictionsmentioning

confidence: 93%

Review of lepton universality tests in B decays

Bifani

¹

,

Descotes-Genon

²

,

Vidal

³

et al. 2018

J. Phys. G: Nucl. Part. Phys.

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Several measurements of tree-and loop-level b-hadron decays performed in the recent years hint at a possible violation of Lepton Universality. This article presents an experimental and theoretical overview of the current status of the field. References 47ii t bDespite its tremendous success in describing all present measurements, the SM can only be regarded as the low-energy, effective, incarnation of a more global theory. For example, the SM cannot account for the matter-antimatter asymmetry currently present in the Universe, it does not provide a Dark Matter candidate and it does not explain its own gauge group structure, the charge assignment of the fermions or the mass hierarchy between the different families. A more global theory that extends the SM at higher energies and shorter distances could provide an answer to some of these questions, which are at the core of modern particle physics.Searches for signs of New Physics (NP) existing beyond the SM are performed in two ways. The first one looks for the direct production of new particles. The key ingredient for this so-called "relativistic path" is the amount of energy available in the collision, which drives the maximum mass range that can be probed. For this reason, the vast majority of the most stringent limits on the mass of NP particles have been obtained at the Large Hadron Collider (LHC) by the ATLAS and CMS experiments, as shown for example in Ref. [1]. The second method, the so-called "quantum path", exploits the presence of virtual states in the decays of SM particles. Due to quantum mechanics, these intermediate states can be much heavier than the initial and final particles, and can affect the rate of specific decay modes as well as their angular distributions. The most evident example is the β decay of the neutron that probes physics at the W -boson scale. Flavour physics, which studies the properties of s-, c-and b-hadrons, has been extremely successful in providing information on the virtual particles involved in the processes examined. A famous example is the observation of CP violation in K decays [2] that could be interpreted as a sign of the existence of three quark families in the SM [3], several years before the discovery of the third generation [4,5]. Similarly, the first observation of the B 0 -B 0 mixing phenomenon [6] revealed that the t-quark mass was much larger than anticipated, eight years before its direct measurement [7,8]. The investigation of the effects induced by virtual particles on SM decays requires very large data samples, since (for a given coupling to NP) the larger the NP scale, the smaller the influence on the process. While the relativistic path probes the scale of potential NP contributions in a direct way through specific signatures, the quantum path provides constraints correlating the scale and the coupling to NP.In the SM, the leptonic parts of the three families of fermions are identical, except for the different masses of the constituent particles. In particular, the photon, the W and the Z bosons couple in ...

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“…That is, theoretical calculations predict that semi-leptonic B decays should have a substantially smaller rate to the 1 1,2 ν ) and inspires a lot of research interests [7][8][9][10][11][12]. Many efforts have been made to overcome this difficulty [13][14][15][16][17], and part of the theoretical-experimental differences, for example, the B → D 0 ν decay could be improved a e-mail: wgl@hbu.edu.cn (corresponding author) by adding relativistic corrections [18,19], while the puzzle regarding the two 1 + states D 1 and D 1 remains to this day.…”

Section: Introductionmentioning

confidence: 99%

The solution to the ‘1/2 vs 3/2’ puzzle

Wang

¹

,

Li

²

,

Wang

³

et al. 2022

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Using an almost complete relativistic method based on the Bethe–Salpeter equation, we study the mixing angle $$\theta $$ θ , the mass splitting $$\bigtriangleup M$$ △ M , the strong decay widths $$\Gamma (D^{({\prime })}_1)$$ Γ ( D 1 ( ′ ) ) and the weak production rates $$Br(B\rightarrow D^{({\prime })}_1\ell \nu _{\ell })$$ B r ( B → D 1 ( ′ ) ℓ ν ℓ ) of the $$D_1(2420)$$ D 1 ( 2420 ) and $$D_1^{\prime }(2430)$$ D 1 ′ ( 2430 ) . We find there is the strong cancellation between the $$^1P_1$$ 1 P 1 and $$^3P_1$$ 3 P 1 partial waves in $$D_1^{\prime }(2430)$$ D 1 ′ ( 2430 ) with $$\theta \sim -\,35.3^{\circ }$$ θ ∼ - 35 . 3 ∘ , which leads to the ‘1/2 vs 3/2’ puzzle. The puzzle can not be overcome by adding only relativistic corrections since in a large parameter range where $$\bigtriangleup M$$ △ M is linear varying and not small, the $$\theta $$ θ , $$\Gamma (D^{({\prime })}_1)$$ Γ ( D 1 ( ′ ) ) and $$Br(B\rightarrow D^{({\prime })}_1\ell \nu _{\ell })$$ B r ( B → D 1 ( ′ ) ℓ ν ℓ ) remain almost unchanged but conflict with data. While in a special range around the mass inverse point where $$\bigtriangleup M=0$$ △ M = 0 and $$\theta =\pm \, 90^{\circ }$$ θ = ± 90 ∘ , they change rapidly but we find the windows where $$\bigtriangleup M$$ △ M , $$\Gamma (D^{({\prime })}_1)$$ Γ ( D 1 ( ′ ) ) and $$Br(B\rightarrow D^{({\prime })}_1\ell \nu _{\ell })$$ B r ( B → D 1 ( ′ ) ℓ ν ℓ ) are all consistent with data. The small $$\bigtriangleup M$$ △ M confirmed by experiment, is crucial to solve the ‘1/2 vs 3/2’ puzzle.

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“…The off-shell effect, also called the Breit-Wigner-tail (BWT) effect, is the contribution when the pole mass of D * (s) is smaller than the invariant mass of D (s) P 1 or, in the other case, the contribution with the on-shell effect excluded by a cut on the invariant mass of D (s) P 1 . Recently, motivated by the experimental measurements on the off-shell effects of D * meson in B → Dππ(K) decays, theoretical attention is paid to these virtual effects [14,33]. A new systematic research on the three-body charmed B meson decays including D * (s) resonant states have been done subsequently in the PQCD approach [16].…”

Section: Introductionmentioning

confidence: 99%

Analysis of three-body charmed B meson decays under the factorization-assisted topological-amplitude approach

Zhou,

Li,

Wei

et al. 2021

Preprint

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We analyze the quasi-two-body charmed B decays B +,0 (s) → D * (s) P 2 → D (s) P 1 P 2 with P 1,2 as a pion or kaon. The intermediate processes B (s) → D * (s) P 2 are calculated with the factorizationassisted topological-amplitude approach and the resonant effects are calculated with the Breit-Wigner formalism. Taking all p-wave resonance states D * (s) into consideration, we present the related branching fractions, calculate the Breit-Wigner-Tail effects, and investigate the flavor SU (3) breaking effects. Most of our branching fractions are consistent with the perturbative QCD approach's predictions as well as the current experimental data. With more precision calculation of the intermediate two body charmed B meson decays, our quasi-two-body B decays calculation has significantly less theoretical uncertainty than the perturbative QCD approach. Many of those channels without any experimental data will be confronted with the future more accurate experiment measurements. Our results of the Breit-Wigner-tail effects also agree with the experimental very well. In B 0 decays this effect can reach approximately to 5%. It is also found that the Breit-Wigner-tail effects are not sensitive to the widths of their corresponding resonances. The flavor SU (3) symmetry breaking effect is also investigated.

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Large off-shell effects in the D¯* contribution to B→D¯ππ

Cited by 10 publications

References 39 publications

Review of lepton universality tests in B decays

Review of lepton universality tests in B decays

The solution to the ‘1/2 vs 3/2’ puzzle

Analysis of three-body charmed B meson decays under the factorization-assisted topological-amplitude approach

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