Abstract
We revisit the scalar singlet dark matter (DM) scenario with a pair of dark lepton partners which form a vectorlike Dirac fermionic doublet. The extra doublet couples with the Standard Model (SM) leptonic doublet and the scalar singlet via a non-SM-like Yukawa structure. As a result, (i) since the extra fermionic states interact with other dark sector particles as well as the SM via gauge and Yukawa interactions, it gives rise to new DM annihilation processes including pair annihilation as well as coannihilation channels, and (ii) such a Yukawa structure opens up new production channels for leptonic final states giving much enhancement in cross sections to search for dark matter in the LHC. Using suitable kinematic observables, we train a {\em boosted decision tree} (BDT) classifier to separate enhanced but still feeble light leptonic signals from the background in an effective manner. On the other hand, the same technique is applied to study $\tau$-tagged jets in the search for DM signals.
Highlights
Cosmological considerations and astrophysical observations have established beyond any reasonable doubt the existence of the dark matter (DM)
Since the mass splitting parameters defined in Eq (6) between DM and other dark sector particles play an important role in freeze-out of φ, we will use them as independent parameters along with DM mass
The minuscule Higgs-portal coupling with scalar DM keeps the direct detection cross section below the experimental bound, which is an important handle in reviving the scenario of scalar singlet DM models
Summary
Cosmological considerations and astrophysical observations have established beyond any reasonable doubt the existence of the dark matter (DM). We assume them to be very heavy so that their effect is negligible apart from generating sufficient mass splitting between the dark leptons which will play an important role in our study This dark sector doublet couples with the SM leptonic doublet and the scalar singlet via a novel Yukawa interaction which is less explored in the literature. Our model discusses a leptophilic context, and the coannihilation channels play an important role here due to the gauge interaction in the dark sector in addition to the new Yukawa coupling This feature is significantly different from the cases explored in the literature where the leptophilic Yukawa structure involves singlet dark sector partners with the DM candidate [38,39].
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