Electroweak Precision Measurements of a Nearly-Degenerate $Z^\prime$-$Z$ System
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arXiv
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| Format: | Preprint |
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2023
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| _version_ | 1866914803544489984 |
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| author | Qiu, Dayun Tang, Yi-Lei |
| author_facet | Qiu, Dayun Tang, Yi-Lei |
| contents | In this paper, we discuss the possibility to probe a nearly-degenerate $Z^{\prime}$-$Z$ system by analyzing the $Z$-lineshape at an electron-positron collider. Compared with the usual $Z^{\prime}$ in the literature well separated with the standard model (SM) $Z$ boson in mass, the nearly-degenerate $Z^{\prime}$-$Z$ mixing affects the observed effective ``oblique parameters'' $\tilde{S}$, $\tilde{T}$, $\tilde{U}$, and the effective deviation of ``number of neutrino species'' $δ\tilde{N}_ν$ in a more complicated way and cannot be simply computed perturbatively up to a particular order. Aiming at solving this problem, we write down a general simplified effective Lagrangian and enumerate some parameter spaces corresponding to some typical models, and suggest a method to extract the constraints by looking into the line-shape of the $Z$-like resonance at an electron-positron collider. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2309_16794 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Electroweak Precision Measurements of a Nearly-Degenerate $Z^\prime$-$Z$ System Qiu, Dayun Tang, Yi-Lei High Energy Physics - Phenomenology In this paper, we discuss the possibility to probe a nearly-degenerate $Z^{\prime}$-$Z$ system by analyzing the $Z$-lineshape at an electron-positron collider. Compared with the usual $Z^{\prime}$ in the literature well separated with the standard model (SM) $Z$ boson in mass, the nearly-degenerate $Z^{\prime}$-$Z$ mixing affects the observed effective ``oblique parameters'' $\tilde{S}$, $\tilde{T}$, $\tilde{U}$, and the effective deviation of ``number of neutrino species'' $δ\tilde{N}_ν$ in a more complicated way and cannot be simply computed perturbatively up to a particular order. Aiming at solving this problem, we write down a general simplified effective Lagrangian and enumerate some parameter spaces corresponding to some typical models, and suggest a method to extract the constraints by looking into the line-shape of the $Z$-like resonance at an electron-positron collider. |
| title | Electroweak Precision Measurements of a Nearly-Degenerate $Z^\prime$-$Z$ System |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2309.16794 |