Motivated by the long-lasting 3.5σ discrepancy in the anomalous magnetic moment of muon, we consider a new muon-specific force mediated by a light gauge boson, X, with mass m X < 2m µ and the coupling constant g X ∼ (10 −4 , 10 −3 ). We show that the Belle II experiment has a robust chance to probe such a light boson in e + e − → µ + µ − + X channel and cover the most interesting parameter space explaining the discrepancy with the planned target luminosity, dt L = 50 ab −1 . The clean signal of muon-pair plus missing energy at Belle II can be a smoking gun for the new gauge boson. We expect that the (invisibly decaying) muon-philic light (m X ∼ < 2m µ ) gauge boson can be probed down to g X ∼ > 1.5 × 10 −4 (4.6 × 10 −4 , 2.3 × 10 −4 ) for 50 (1, 10) ab −1 search.
High energy collisions at the High-Luminosity Large Hadron Collider (LHC) produce a large number of particles along the beam collision axis, outside of the acceptance of existing LHC experiments. The proposed Forward Physics Facility (FPF), to be located several hundred meters from the ATLAS interaction point and shielded by concrete and rock, will host a suite of experiments to probe standard model (SM) processes and search for physics beyond the standard model (BSM). In this report, we review the status of the civil engineering plans and the experiments to explore the diverse physics signals that can be uniquely probed in the forward region. FPF experiments will be sensitive to a broad range of BSM physics through searches for new particle scattering or decay signatures and deviations from SM expectations in high statistics analyses with TeV neutrinos in this low-background environment. High statistics neutrino detection will also provide valuable data for fundamental topics in perturbative and non-perturbative QCD and in weak interactions. Experiments at the FPF will enable synergies between forward particle production at the LHC and astroparticle physics to be exploited. We report here on these physics topics, on infrastructure, detector, and simulation studies, and on future directions to realize the FPF’s physics potential.
We discuss a list of possible light gauge boson interpretations for the longstanding experimental anomaly in (g − 2) µ and also recent anomalous excess in K L → π 0 + (invisible) events at the J-PARC KOTO experiment. We consider two models: i) L µ − L τ gauge boson with heavy vector-like quarks and ii) (L µ − L τ ) + (B 3 − L τ ) gauge boson in the presence of right-handed neutrinos. When the light gauge boson has mass close to the neutral pion in order to satisfy the Grossman-Nir bound, the models successfully explain the anomalies simultaneously while satisfying all known experimental constraints. We extensively provide the future prospect of suggested models.
A novel mechanism of boosting dark matter by cosmic neutrinos is proposed. The new mechanism is so significant that the arriving flux of dark matter in the mass window 1 keV mDM 1 MeV on Earth can be enhanced by two to four orders of magnitude compared to one only by cosmic electrons. Thereby we firstly derive conservative but still stringent bounds and future sensitivity limits for such cosmic-neutrino-boosted dark matter (νBDM) from advanced underground experiments such as Borexino, PandaX, XENON1T, and JUNO.
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