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arXiv 1507.08672hep-phhep-exhep-lat
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简化新物理模型中的$K\toπν\barν$和$ε'/ε$

$K\toπν\barν$ and $ε'/ε$ in Simplified New Physics Models

Andrzej J. Buras, Dario Buttazzo, Robert Knegjens

备注：
32 pages, 6 figures, 1 table. v2: updated analysis in section 4, matches version published in JHEP
发表信息：
JHEP 1511 (2015) 166
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摘要：

衰变$K^+\toπ^+ν\barν$和$K_L\toπ^0ν\barν$是理论上最干净的稀有介子衰变，是新物理学中非常敏感的探测器。鉴于良好的前景，达到标准模型的灵敏度$K^+\toπ^+ν\barν$的NA 62实验在欧洲核子研究中心和$K_L\toπ^0ν\barν$的KOTO实验在J-PARC，我们研究他们在最简单的扩展SM中，这两个衰变和其他味观测之间的严格相关性。我们首先考虑简单的模型与树级Z和Z'的贡献，在MFV或$U(2)^3$对称性强加在夸克的味道破坏耦合。然后，我们将得到的相关性与通用模型中存在的那些，后者的耦合是任意的，受到限制，从$ΔF=2$过程，电弱和对撞机数据。特别令人感兴趣的是与$ε'/ε$和$K_L\toμ^+μ^-$的相关性，这限制了NP对$K^+\toπ^+ν\barν$和$K_L\toπ^0ν\barν$贡献的大小，这取决于耦合的狄拉克结构和相关算子。但在MFV中，来自$B_s\toμ^+μ^-$的约束也很重要。我们考虑到最近的结果从晶格QCD和大N的方法，表明$ε'/ε$在SM显着低于数据。虽然在许多模型中，$ε'/ε$的增强意味着$K_L\toπ^0ν\barν$的抑制，我们提出了两个模型，这些观测值可以同时增强相对于SM预测。我们在这里考虑的简单模型中发现的$K^+\toπ^+ν\barν$和$B\to K(K^*)μ^+μ^-$之间的相关性，应该是欧洲核子研究中心的NA 62和LHCb实验学家在未来几年感兴趣的。带有$B\to K(K^*)ν\barν$的产品将在Belle II进行测试。

英文摘要：

The decays $K^+\toπ^+ν\barν$ and $K_L\toπ^0ν\barν$, being the theoretically cleanest rare decays of mesons, are very sensitive probes of New Physics. In view of the excellent prospects of reaching the Standard Model sensitivity for $K^+\toπ^+ν\barν$ by the NA62 experiment at CERN and for $K_L\toπ^0ν\barν$ by the KOTO experiment at J-PARC, we study them in the simplest extensions of the SM in which stringent correlations between these two decays and other flavour observables are present. We first consider simple models with tree-level Z and Z' contributions in which either MFV or a $U(2)^3$ symmetry is imposed on the quark flavour-violating couplings. We then compare the resulting correlations with those present in generic models in which the latter couplings are arbitrary, subject to constraints from $ΔF=2$ processes, electroweak and collider data. Of particular interest are the correlations with $ε'/ε$ and $K_L\toμ^+μ^-$ which limit the size of NP contributions to $K^+\toπ^+ν\barν$ and $K_L\toπ^0ν\barν$, depending on the Dirac structure of couplings and the relevant operators. But in MFV also the constraint from $B_s\toμ^+μ^-$ turns out to be important. We take into account the recent results from lattice QCD and large N approach that indicate $ε'/ε$ in the SM to be significantly below the data. While in many models the enhancement of $ε'/ε$ implies a suppression of $K_L\toπ^0ν\barν$, we present two models in which these observables can be simultaneously enhanced relative to SM predictions. A correlation between $K^+\toπ^+ν\barν$ and $B\to K(K^*)μ^+μ^-$, found by us in the simple models considered here, should be of interest for NA62 and LHCb experimentalists at CERN in the coming years. The one with $B\to K(K^*)ν\barν$ will be tested at Belle II.

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