Prospects for discovering new physics in charm sector through low-energy scattering processes $e^-p\to e^- (μ^-)Λ_c$

Abstract

We investigate the potential for discovering new physics through the low-energy scattering processes e − p → e − (µ − )Λc, which could be accessible in the forthcoming ep scattering experiments once adapted to our proposed setups. In the framework of low-energy effective Lagrangian, we demonstrate that, compared with the conventional flavor-changing-neutral-current weak decays of charmed hadrons and the dilepton productions at high-energy colliders, the low-energy scattering processes can provide more competitive potentials for hunting the underlying new physics. In some specific leptoquark models, we also show that promising event rates can be expected for both the scattering processes, and point out a possible way to distinguish the experimental signals due to the scalar leptoquarks from those of the vector ones.

Searching and identifying leptoquarks through low-energy polarized scattering processes $e^-p\to e^-Λ_c$

“…where L SM eff and L LQ eff represent the SM and the LQ contribution, respectively. Since the SM long-distance effects do not contribute to the scattering processes [82], while the short-distance effects are strongly GIM suppressed [59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75], here we can safely neglect the contribution from L SM eff . The most general low-energy effective Lagrangian L LQ eff induced by tree-level exchanges of LQs is given by [53]…”

“…where, as done in Ref. [82], we have coincided the masseigenstate basis of the left-handed up-type quarks and charged leptons with their flavor basis, and uniformly denoted the LQ masses by M , but bearing in mind that…”

“…[82], where we have demonstrated that a combined analysis of the experimental signals of the low-energy scattering processes and the semileptonic D-meson decays can distinguish certain scalar LQs from the vector ones. Unfortunately, only the LQs that would not induce tree-level proton decays have been considered there, and the vector LQs are found to be unable to be disentangled from each other [82]. Such a deficiency, as will be shown in this work, can be amended by considering the low-energy polarized scattering processes e − p → e − Λ c .…”

“…Among the various processes used to probe the LQ interactions, the flavor-changing neutral-current (FCNC) ones in the charm sector are the ideal searching ground, due to their absence at tree level and being strongly suppressed by the Glashow-Iliopoulos-Maiani (GIM) [58] mechanism at one loop in the SM. The known FCNC processes in the charm sector consist of the rare weak decays of the charmed hadrons , the high-p T dilepton invariant mass tails of the processes pp → ( ) at high-energy colliders [80,81], as well as the low-energy scattering processes e − p → e − (µ − )Λ c proposed recently by us [82]. Interestingly enough, we found that, based on a set of high-intensity electron beam and liquid hydrogen target-both have been used to search for sub-GeV dark vector bosons [83][84][85][86]-and taking into account the most stringent constraints on the corresponding LQ interactions from other processes, very promising event rates can be expected for both the scattering processes in some specific LQ models [82].…”

“…The known FCNC processes in the charm sector consist of the rare weak decays of the charmed hadrons , the high-p T dilepton invariant mass tails of the processes pp → ( ) at high-energy colliders [80,81], as well as the low-energy scattering processes e − p → e − (µ − )Λ c proposed recently by us [82]. Interestingly enough, we found that, based on a set of high-intensity electron beam and liquid hydrogen target-both have been used to search for sub-GeV dark vector bosons [83][84][85][86]-and taking into account the most stringent constraints on the corresponding LQ interactions from other processes, very promising event rates can be expected for both the scattering processes in some specific LQ models [82]. Motivated by such a promising prospect of the LQ searches at the low-energy scattering processes (as well as the tenacious hunting for the LQs at the Large Hadron Collider (LHC) [87][88][89][90][91][92][93][94] and other future facilities [95,96]), we will address another interesting question: can the different LQs be systematically disentangled from each other through the low-energy FCNC scattering processes?…”