Dark matter bound state formation in fermionic Z 2 DM model with light dark photon and dark Higgs boson
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Springer
Received: November 15, Revised: July 9, Accepted: September 7, Published: October 13,
2019 2020 2020 2020
Pyungwon Ko,b,c Toshinori Matsuib,d and Yi-Lei Tanga,c,1 a
School of Physics, Sun Yat-Sen University, No. 135 Xingang Xi Road, Guangzhou 510275, China b School of Physics, KIAS, 85 Hoegiro, Seoul 02455, Republic of Korea c Quantum Universe Center, KIAS, 85 Hoegiro, Seoul 02455, Republic of Korea d Department of Physics, KAIST, 291 Daehakro, Daejeon 34141, Republic of Korea
E-mail: [email protected], [email protected], [email protected] Abstract: If fermionic dark matter (DM) is stabilized by dark U(1) gauge symmetry that is spontaneously broken into its subgroup Z2 , the particle contents of the model becomes very rich: DM and excited DM, both of them are Majorana fermions, as well as two dark force mediators, dark photon and dark Higgs boson are naturally present due to the underlying dark gauge symmetry. In this paper, we study the DM bound state formation processes within this scenario, assuming both dark photon and dark Higgs are light mediators and including the effects of excited DM. The Goldstone boson contributions to the potential matrix in the Schr¨odinger equations are found to be important. The emissions of a longitudinal vector boson (or somehow equivalently a Goldstone boson) during the DM bound state formations are crucial to induce a significant reannihilation process, reducing the dark matter relic abundance. Most of the stringent constraints for this kind of dark matter considered in the literature are simply evaded. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM, Effective Field Theories, Discrete Symmetries ArXiv ePrint: 1910.04311 1
Corresponding author.
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP10(2020)082
JHEP10(2020)082
Dark matter bound state formation in fermionic Z2 DM model with light dark photon and dark Higgs boson
Contents 1 Introduction
1
2 Model setup
4 6 7 9 11
4 Bound state formation cross section and dissociation rate 4.1 Calculation of bound state formation cross section 4.2 Pair annihilations inside the bound state particles 4.3 Boltzmann equations
14 14 21 25
5 Numerical results and discussions 5.1 Numerical results 5.2 Constraints from the experiments 5.3 Comparison with other similar situations in the literature
29 29 33 36
6 Conclusions and future prospect
38
A A dark matter annihilation problem in the higgsless soft-breaking model 39 B Modified Ward identity in the broken phase
41
C Gauge dependence of the bound state
45
D Reasons for neglecting the emission from the mediators
48
E Quantum numbers of the DM bound states
50
1
Introduction
A number of cosmological observations through gravitational interaction indicate that about 25% of the energy budget of the current Universe consists of nonbaryonic dark matter (DM). So far almost nothing is known about the physical nature of DM: the number of DM species in the universe, their masses and spins, and their intera
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