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弱电精密数据与Lee-Wick标准模型

Electroweak Precision Data and the Lee-Wick Standard Model

Thomas E. J. Underwood, Roman Zwicky

备注：
32 pages, 4 figures, version to appear in PRD; includes extensive addendum with comments on the applicability of the original Peskin & Takeuchi formalism to the LWSM
发表信息：
Phys.Rev.D79:035016,2009
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摘要：

本文研究了最近提出的Lee-Wick标准模型在树层次上的电弱精度约束。我们分别分析了低能、Z极（LEP 1/SLC）和LEP 2数据。我们从辅助场和高阶导数理论推导出精确的树级低能和Z极有效拉格朗日量。对于LEP 2数据，我们使用的事实是，Lee-Wick标准模型属于所谓的“通用类”，可以通过m_W^2/ M_{1,2}中领先顺序的七个倾斜参数来描述。在树的层次上，我们发现唯一的非零斜参数是Y = -m_W^2/M_1^2和W = -m_W^2/M_2^2，其中负号是由于负范数态的存在。Lee-Wick算子在树水平上不违反SU（2）L或保管对称性，S=0，T=0.在这方面，我们的结果与先前的分析有很大不同。我们展示了一个包含所有三个约束的图。LEP 1/SLC约束比LEP 2稍强，比低能约束强得多。LEP 1/SLC结果在99%置信水平上排除了M_1 ~ M_2 ~ 3 TeV的规范玻色子质量。当其中一个质量取较大值时，可能会有较小的质量。对电弱观测量的环路修正被标准的~1/（4 π）^2因子所抑制，因此预计不会改变对M_1和M_2的约束。这一论断在理论的高阶导数表述中最为明显。

英文摘要：

We investigate the electroweak precision constraints on the recently proposed Lee-Wick Standard Model at tree level. We analyze low energy, Z-pole (LEP1/SLC) and LEP2 data separately. We derive the exact tree level low energy and Z-pole effective Lagrangians from both the auxiliary field and higher derivative formulation of the theory. For the LEP2 data we use the fact that the Lee-Wick Standard Model belongs to the so-called 'universal class' which can be described by seven oblique parameters at leading order in m_W^2/M_{1,2}^2. At tree level we find that the only non-zero oblique parameters are Y = -m_W^2/M_1^2 and W = -m_W^2/M_2^2, where the negative sign is due to the presence of the negative norm states. The Lee-Wick operators do not violate the SU(2)_L or custodial symmetry at tree level implying S=0 and T=0 respectively. Our results differ substantially from a prior analysis in this respect. We show a plot including all three constraints. The LEP1/SLC constraints are slightly stronger than LEP2 and much stronger than the low energy ones. The LEP1/SLC results exclude gauge boson masses of M_1 ~ M_2 ~ 3 TeV at the 99% confidence level. Somewhat lower masses are possible when one of the masses assumes a large value. Loop corrections to the electroweak observables are suppressed by the standard ~1/(4 π)^2 factor and are therefore not expected to change the constraints on M_1 and M_2. This assertion is most transparent from the higher derivative formulation of the theory.

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