论文标题
$ d^+\toπ^+\ ell^+\ ell^ - $中的QCD和新物理
Disentangling QCD and New Physics in $D^+\toπ^+\ell^+\ell^-$
论文作者
论文摘要
在本文中，我们考虑了衰减$ d^+\toπ^+\ ell^+\ ell^ - $，特别是解决共振贡献以及弱歼灭图的相对较大的贡献。对于薄弱的歼灭图，我们在低$ q^2 $和高$ q^2 $时包括QCD分解的已知结果，调整了操作员产品扩展中$ b $衰减的现有计算。正如Shifman所建议的那样，通过分散关系，通过分散关系来实现光谱的功能，将光谱的功能作为雷格样共振的塔而建模，并在深欧几里德强加了党派行为。该模型的参数是使用$ e^+e^ - \ to {\ rm（hadrons）} $和$τ\ to {\ rm（hadrons）}+ν_τ$ data以及共振衰减的分支比率的$ d^+d^+d^+toπ^+\ el^ell^el^el^el^el^el^el^el^el^el^el^ $ r =ρ$，$ω$和$ ϕ $。我们执行彻底的错误分析，并为标准模型差异分支比率介绍了$ Q^2 $的函数。然后将重点放在观察到的$ f_h $和$ a _ {\ rm fb} $上，我们考虑了此通道对以外的标准模型的影响的敏感性，无论是以模型独立的方式和leptoquarks而言。
In this paper we consider the decay $D^+\toπ^+\ell^+\ell^-$, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low $q^2$ and at high $q^2$, adapting the existing calculation for $B$ decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using $e^+e^-\to{\rm (hadrons)}$ and $τ\to {\rm (hadrons)}+ν_τ$ data as well as the branching ratios for the resonant decays $D^+\toπ^+\,R\,(R\to\ell^+\ell^-)$, with $R=ρ$, $ω$, and $ϕ$. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of $q^2$. Focusing then on the observables $F_H$ and $A_{\rm FB}$, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.
