Beyond Minimal Lepton Flavored Dark Matter

We consider a class of flavored dark matter (DM) theories where dark matter interacts with the Standard Model lepton fields at the renormalizable level. We allow for a general coupling matrix between the dark matter and leptons whose structure is beyond the one permitted by the minimal flavor violation (MFV) assumption. It is assumed that this is the only new source of flavor violation in addition to the Standard Model (SM) Yukawa interactions. The setup can be described by augmenting the SM flavor symmetry by an additional $\mathrm{SU}(3)_{\chi}$, under which the dark matter $\chi$ transforms. This framework is especially phenomenologically rich, due to possible novel flavor-changing interactions which are not present within the more restrictive MFV framework. As a representative case study of this setting, which we call "beyond MFV" (BMFV), we consider Dirac fermion dark matter which transforms as a singlet under the SM gauge group and a triplet under $\mathrm{SU}(3)_{\chi}$. The DM fermion couples to the SM lepton sector through a scalar mediator $\phi$. Unlike the case of quark-flavored DM, we show that there is no $\mathbb{Z}_3$ symmetry within either the MFV or BMFV settings which automatically stabilizes the lepton-flavored DM. We discuss constraints on this setup from flavor-changing processes, DM relic abundance as well as direct and indirect detections. We find that relatively large flavor-changing couplings are possible, while the dark matter mass is still within the phenomenologically interesting region below the TeV scale. Collider signatures which can be potentially searched for at the lepton and hadron colliders are discussed. Finally, we discuss the implications for decaying dark matter, which can appear if an additional stabilizing symmetry is not imposed.Comment: 30 pages, 12 figures; minor corrections, added references and discussion on decaying dark matter, matches published versio

Decreases in Core Temperature and Sweating Onset During Whole-body Heating in Individuals with Multiple Sclerosis Following Administration of 4-aminopyridine

Multiple sclerosis (MS) is a progressive neurological disease of the central nervous system that can result in impairments in thermoregulatory function. 4-aminopyridine (4AP), a voltage-gated K+ channel blocker, has been postulated to improve conduction in demyelinated axons and improve MS related disabilities. The aim of this study was to test the hypothesis that administration of 4AP would improve sudomotor function in individuals with MS during passive whole-body heating (WBH). Eleven subjects (8 females, 3 males; 39±7 years; 78.6±24.0 kg; 170±9 cm; 8±4 years since diagnosis) with relapsing-remitting MS participated in this study. A randomized single-blinded 2-week crossover design was utilized with 4AP and placebo (PBO) including a 1-week washout period between drugs. Subjects were outfitted in a tube-lined water perfusion suit and exposed to a normothermic (NT) baseline (34 °C water) and WBH (48 °C water; increase in internal temperature of ~0.8 °C) condition. Core body temperature (telemetric pill) and sweat rate at the dorsal forearm (capacitance hygrometry) were continuously measured. Baseline NT core body temperature while on 4AP was lower compared to placebo (4AP: 37.3±0.2 °C vs. PBO: 37.5±0.2 °C, p=0.002). Core body temperature at the onset of sweat was also lower while on 4AP compared to placebo (4AP: 37.4±0.2 °C vs. PBO: 37.6±0.3 °C, p=0.0006). However, sweat rate (Δ from NT) on 4AP was similar compared to placebo during WBH (4AP: 0.7±0.3 mg/cm2/min vs. PBO: 0.8±0.4 mg/cm2/min, p=0.49). These initial findings suggest K+ channel blockers may have protective benefits for people living with MS by lowering resting core temperature and the sweat onset core temperature threshold. Thus, administration of 4AP may improve heat sensitivity in MS by expanding the range for core temperatures increases prior to symptom worsening