Improved white dwarves constraints on inelastic dark matter and left-right symmetric models

Abstract

Weakly interacting massive particles (WIMPs) can be captured in compact stars such as white dwarves (WDs) if they are in a dark matter (DM)-rich environment, leading to an increase in the star luminosity through their annihilation process. N -body simulations suggest that the core of the Messier 4 globular cluster (where plenty of WDs are observed) is rich of DM. Assuming this is the case, we use a recent improvement in the calculation of the WD equation of state to show that when the WIMP interacts with the nuclear targets within the WD through inelastic scattering, and its mass exceeds a few tens of GeV, the data on low-temperature large-mass WDs in M4 can probe values of the mass splitting as large as δ ≲40 MeV . Such value largely exceeds those ensuing from direct detection and from solar neutrino searches. We apply such improved constraint to the specific DM scenario of a self-conjugate bidoublet in the left-right symmetric model (LRSM), where the standard S U (2 )_L group with coupling g_L is extended by an additional S U (2 )_R with coupling g_R in order to explain maximal parity violation in weak interactions. We show that bounds from WDs significantly reduce the cosmologically viable parameter space of such scenario, in particular requiring g_R>g_L. For instance, for g_R/g_L=1.8 we find the two viable mass ranges 1.2 TeV ≲m_χ≲3 TeV and 5 TeV ≲m_χ≲10 TeV , when the charged S U (2 )_R gauge boson mass M_W2is lighter than ≃12 TeV . We also discuss the ultraviolet completion of the LRSM model, when the latter is embedded in a grand unified theory. We show that such low-energy parameter space and compatibility to proton-decay bounds require a nontrivial extension of the particle content of the minimal model. We provide a specific example where M_{W 2}≲10 TeV is achieved by extending the LRSM at high energy with color triplets that are singlets under all other groups, and g_R/g_L>1 is obtained by introducing S U (2 )_L triplets with no S U (2 )_R counterparts, i.e., by breaking the symmetry between the multiplets of S U (2 )_L and S U (2 )_R.