Revisiting big bang nucleosynthesis with a new particle species : effect of co-annihilation with nucleons
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arXiv
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| Formato: | Preprint |
| Publicado: |
2022
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| _version_ | 1866929392473604096 |
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| author | Ghosh, Deep |
| author_facet | Ghosh, Deep |
| contents | In big bang nucleosynthesis (BBN), the light matter abundance is dictated by the neutron-to-proton ($n/p$) ratio which is controlled by the standard weak processes in the early universe. Here, we study the effect of an extra particle species ($χ$) which \textit{co-annihilates} with neutron (proton), thereby potentially changing the ($n/p$) ratio in addition to the former processes. We find a novel interplay between the co-annihilation and the weak interaction in deciding the ($n/p$) ratio and the yield of $χ$. Large co-annihilation strength ($G_D$) in comparison to the weak coupling ($G_F$), potentially can alter the number of nucleons in the thermal bath modifying the ($n/p$) ratio from its standard evolution. We find that the standard BBN prediction is restored for $G_D/G_F \lesssim 10^{-2}$, while the mass of $χ$ being much smaller than the neutron mass. When the mass of $χ$ is comparable to the neutron mass, we can allow large $G_D/G_F ~(\gtrsim 10^2)$ values, as the thermal abundance of $χ$ becomes Boltzmann-suppressed. Therefore, the ($n/p$) ratio is restored to its standard value via dominant weak processes in later epochs. We also discuss the stability of the new particle in an effective theroy framework for co-annihilation. Further, the co-annihilation interaction generates elastic scattering of $χ$ and nucleons at the next-to-leading order. This provides a way to probe the scenario in direct detection experiments, if $χ$ is accidentally stable over cosmological timescale. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2207_10499 |
| institution | arXiv |
| publishDate | 2022 |
| record_format | arxiv |
| spellingShingle | Revisiting big bang nucleosynthesis with a new particle species : effect of co-annihilation with nucleons Ghosh, Deep High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics In big bang nucleosynthesis (BBN), the light matter abundance is dictated by the neutron-to-proton ($n/p$) ratio which is controlled by the standard weak processes in the early universe. Here, we study the effect of an extra particle species ($χ$) which \textit{co-annihilates} with neutron (proton), thereby potentially changing the ($n/p$) ratio in addition to the former processes. We find a novel interplay between the co-annihilation and the weak interaction in deciding the ($n/p$) ratio and the yield of $χ$. Large co-annihilation strength ($G_D$) in comparison to the weak coupling ($G_F$), potentially can alter the number of nucleons in the thermal bath modifying the ($n/p$) ratio from its standard evolution. We find that the standard BBN prediction is restored for $G_D/G_F \lesssim 10^{-2}$, while the mass of $χ$ being much smaller than the neutron mass. When the mass of $χ$ is comparable to the neutron mass, we can allow large $G_D/G_F ~(\gtrsim 10^2)$ values, as the thermal abundance of $χ$ becomes Boltzmann-suppressed. Therefore, the ($n/p$) ratio is restored to its standard value via dominant weak processes in later epochs. We also discuss the stability of the new particle in an effective theroy framework for co-annihilation. Further, the co-annihilation interaction generates elastic scattering of $χ$ and nucleons at the next-to-leading order. This provides a way to probe the scenario in direct detection experiments, if $χ$ is accidentally stable over cosmological timescale. |
| title | Revisiting big bang nucleosynthesis with a new particle species : effect of co-annihilation with nucleons |
| topic | High Energy Physics - Phenomenology Cosmology and Nongalactic Astrophysics |
| url | https://arxiv.org/abs/2207.10499 |