Towards a precision calculation of $N_{\rm eff}$ in the Standard Model III: Improved estimate of NLO contributions to the collision integral
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866910486862233600 |
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| author | Drewes, Marco Georis, Yannis Klasen, Michael Wiggering, Luca Paolo Wong, Yvonne Y. Y. |
| author_facet | Drewes, Marco Georis, Yannis Klasen, Michael Wiggering, Luca Paolo Wong, Yvonne Y. Y. |
| contents | We compute the dominant QED correction to the neutrino-electron interaction rate in the vicinity of neutrino decoupling in the early universe, and estimate its impact on the effective number of neutrino species $N_{\rm eff}$ in cosmic microwave background anisotropy observations. We find that the correction to the interaction rate is at the sub-percent level, consistent with a recent estimate by Jackson and Laine. Relative to that work we include the electron mass in our computations, but restrict our analysis to the enhanced $t$-channel contributions. The fractional change in $N_{\rm eff}^{\rm SM}$ due to the rate correction is of order $10^{-5}$ or below, i.e., about a factor of 30 smaller than that recently claimed by Cielo {\it et al.}, and below the nominal computational uncertainties of the current benchmark value of $N_{\rm eff}^{\rm SM} = 3.0440 \pm 0.0002$. We therefore conclude that aforementioned number remains to be the state-of-the-art benchmark for $N_{\rm eff}^{\rm SM}$ in the standard model of particle physics. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2402_18481 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Towards a precision calculation of $N_{\rm eff}$ in the Standard Model III: Improved estimate of NLO contributions to the collision integral Drewes, Marco Georis, Yannis Klasen, Michael Wiggering, Luca Paolo Wong, Yvonne Y. Y. High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics We compute the dominant QED correction to the neutrino-electron interaction rate in the vicinity of neutrino decoupling in the early universe, and estimate its impact on the effective number of neutrino species $N_{\rm eff}$ in cosmic microwave background anisotropy observations. We find that the correction to the interaction rate is at the sub-percent level, consistent with a recent estimate by Jackson and Laine. Relative to that work we include the electron mass in our computations, but restrict our analysis to the enhanced $t$-channel contributions. The fractional change in $N_{\rm eff}^{\rm SM}$ due to the rate correction is of order $10^{-5}$ or below, i.e., about a factor of 30 smaller than that recently claimed by Cielo {\it et al.}, and below the nominal computational uncertainties of the current benchmark value of $N_{\rm eff}^{\rm SM} = 3.0440 \pm 0.0002$. We therefore conclude that aforementioned number remains to be the state-of-the-art benchmark for $N_{\rm eff}^{\rm SM}$ in the standard model of particle physics. |
| title | Towards a precision calculation of $N_{\rm eff}$ in the Standard Model III: Improved estimate of NLO contributions to the collision integral |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2402.18481 |