arXiv subjects

Dongdong Ni

Publications and source records attributed to Dongdong Ni.

4 recordsLinked to original sources

arXiv2026

The capability of CSST in characterizing planetary atmospheres. I. transmission spectroscopy of hot Jupiters

Transmission spectroscopy has become a primary tool for probing exoplanetary atmospheres, enabling constraints on their chemical compositions and providing limited information on their thermal properties. We assess the potential of the upcoming Chinese Space Station Telescope (CSST) for exoplanet atmospheric characterization through transmission spectroscopy. Theoretical spectra of hot gas planets are generated and used to simulate slitless spectroscopic observations with the CSST across the ultraviolet-to-near-infrared range. Atmospheric retrievals performed on the simulated data are compared with the input models to assess the robustness and accuracy of parameter determinations. We find that multi-band observations across three wavelength channels, each with two transits can place meaningful constraints on key atmospheric parameters. For multi-band observations that account for correlated (red) noise, future CSST observations are expected to achieve constraints that are comparable to, or in some cases slightly weaker than, those of the Hubble Space Telescope (HST), depending on the noise level and observing strategy. We conclude that CSST will provide unique and complementary constraints on the chemical compositions and physical properties of exoplanetary atmospheres, particularly for atomic species, metal-bearing molecules, and scattering processes accessible in the UV and optical, thereby complementing JWST's infrared sensitivity to molecular species.

astro-ph.EP↗

arXiv2024

Baryon number violation accompanied by CP-violation as a quantum tunneling effect induced by superfluid pairing interactions

In this work, we explore a new picture of baryon number ($\mathcal{B}$) violation inspired by the formal analogies between the Brout-Englert-Higgs model and the Ginzburg-Landau model. A possible manifestation of this new picture could be the transition between a pair of neutrons and a pair of antineutrons (i.e. $nn \rightarrow \bar{n}\bar{n}$), which violates $\mathcal{B}$ by 4 units. In the presence of the superfluid pairing interactions, two neutrons can form a Cooper pair and can be modeled by a semi-classical complex scalar field, which carries two units of $\mathcal{B}$. In the presence of the $\mathcal{B}$-violating terms, the system does not possess a continuous $U(1)$ symmetry but instead it respect a discrete $Z_2$ symmetry. Before the spontaneous breaking of the $Z_2$ symmetry, the ground state (vacuum) of the neutron Cooper field and that of the antineutron Cooper field should have degenerate energy levels. After the spontaneous breaking of the $Z_2$ symmetry, the degeneracy of the ground states would be removed and a domain wall that interpolates between the two inequavalent ground states can emerge. If the vacuum energy of the neutron Cooper field is higher than that of the antineutron Cooper field, the false vacuum ($nn$) would decay into the true vacuum ($\bar{n}\bar{n}$) through a quantum tunneling process across the domain wall. Therefore, The $nn \rightarrow \bar{n}\bar{n}$ transition process can be considered as a false vacuum decay through a quantum tunneling process induced by the superfluid pairing interactions. Both the $\mathcal{B}$-violating and CP-violating effects can be quite naturally accommodated in the $nn \rightarrow \bar{n}\bar{n}$ transition process. The $\mathcal{B}$-violating process accompanied by CP-violation would open a promising avenue for exploring new physics beyond the Standard Model.

hep-ph↗

arXiv2022

Dineutron decay into sterile anti-neutrinos in neutron stars and its observable consequences

In some extensions of the Standard Model (SM), two neutrons are allowed to decay into two sterile anti-neutrinos ($nn \rightarrow \barχ\barχ$) via new scalar bosons. This process violates both the baryon number ($\mathcal{B}$) and the lepton number ($\mathcal{L}$) by two units but conserves their difference $(\mathcal{B}-\mathcal{L})$. Neutron stars contain a large number of neutrons and thus the $nn \rightarrow \barχ\barχ$ process can be greatly enhanced inside a neutron star. This process could result in non-trivial effects that are different from the SM predictions and can be explored through astrophysical and laboratory observations. Furthermore, a large number of sterile antineutrinos, which may be dark matter candidates, can be emitted from the interior of the neutron star. The properties of the emitted particles show a particular pattern that can be uniquely determined by the mass and radius of the neutron star. In addition, the dineutron decay may contribute to the orbital-period change of the binary systems containing neutron stars. We analyze the possibility to constrain the mass of the new scalar bosons using the observations of the binary's orbital-period changes. It is found that the mass of the new scalar bosons is roughly restricted in the range from 1 TeV to several TeV, which is possibly within the reach of direct searches at the LHC or future high-energy experiments. The joint analysis which combines the astrophysics and particle phenomenology could provide an excellent opportunity for the study of the new physical effects beyond the SM.

hep-ph↗

arXiv2022

Neutron-neutral particle mixing and its observable consequences

In this work, we explore the mixing between neutron ($n$) and elementary neutral particle ($η$), which violates both the baryon number ($\mathcal{B}$) and the lepton number ($\mathcal{L}$) by one unit but conserves their difference $(\mathcal{B}-\mathcal{L})$. Such mixing may give rise to non-trivial effects that are different from the Standard Model predictions. We organize our discussions based on two scenarios, roughly depending on whether an interference between oscillation and decay occurs, or whether the new-physics effects associated with the $n$-$η$ mixing contribute to the absorptive mixing amplitude. If an oscillation process is not accompanied by an interference between oscillation and decay, or the new-physics interactions do not contribute to the absorptive mixing amplitude, such a process can be classified as pure oscillation. Otherwise, it can be classified as impure oscillation. In the scenario of pure oscillation, CP-violation arising from the Majorana phase can manifest itself through the $n$-$\bar{n}$ oscillation process and may lead to observable effects. In the scenario of impure oscillation, we analyze the testable implications on the masses and lifetimes of the mass eigenstates formed as a result of the $n$-$\bar{n}$ oscillation mediated by $η$. In this scenario, we also suggest a unified interpretation of the neutron lifetime anomaly and the $n$-$\bar{n}$ oscillation measurements based on the $n$-$η$ mixing. In both scenarios, we present the lower bounds imposed by the experimental searches for $n$-$\bar{n}$ oscillations on the masses of the color multiplet bosons and point out that they could be within the reach of a direct detection at the LHC or future high-energy experiments.

hep-ph↗