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Closing the gap on RD* by including longitudinal effects

机译：通过包括纵向效应来缩小RD *上的差距

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摘要

Measurements of the R D * ≡ Br ( B → τ ν D * ) / Br ( B → e ν D * ) parameter remain in tension with the standard model prediction, despite recent results helping to close the gap. The standard model prediction it is compared with considers the D * as an external particle, even though what is detected in experiments is a D π pair it decays into, from which it is reconstructed. We argue that the experimental result must be compared with the theoretical prediction considering the full four-body decay ( B → l ν D * → l ν D π ). We show that the longitudinal degree of freedom of the off shell D * helps to further close the disagreement gap with experimental data. We find values for the ratio R D π l ≡ Br ( B → τ ν τ D π ) / Br ( B → l ν l D π ) of R D π e = 0.274 ± 0.003 and R D π μ = 0.275 ± 0.003 , where the uncertainty comes from the uncertainty of the form factors parameters. Comparing against R D π reduces the gap with the latest LHCb result from 1.1 σ to 0.48 σ , while the gap with the latest Belle result is reduced from 0.42 σ to just 0.10 σ and with the world average results from 3.7 σ to 2.1 σ .
机译：尽管最近的结果有助于弥合差距，但R D *≡Br（B→τνD *）/ Br（B→eνD *）参数的测量仍然保持标准模型的预测。与之比较的标准模型预测将D *视为外部粒子，即使在实验中检测到的是Dπ对衰减并从中进行重构。我们认为，必须将考虑全四体衰变（B→lνD *→lνDπ）的理论结果与实验结果进行比较。我们表明，脱壳D *的纵向自由度有助于进一步缩小与实验数据之间的分歧。我们找到RDπe = 0.274±0.003和RDπμ= 0.275±0.003的RDπl≡Br（B→τντDπ）/ Br（B→lνl Dπ）的值。不确定性来自形状因子参数的不确定性。与R Dπ的比较将与最新LHCb结果的差距从1.1σ减小到0.48σ，而与最新Belle结果的差距从0.42σ减小到仅0.10σ，并且世界平均结果从3.7σ减小到2.1σ。

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