Search NASA⌕ Search

Engineering topics

Tobioka, Kohsaku (ORCID:0000000325409649)

Publications and source records attributed to Tobioka, Kohsaku (ORCID:0000000325409649).

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Energy growth in VLVL → VLVL, VLVLh scattering to probe Higgs cubic and HEFT interactions

Abstract We compute the energy scales of perturbative unitarity violation inV L V L →V L V L hprocesses and compare them toV L V L →hhhprocess, whereV L refers to a longitudinal mode ofZorWboson, andhthe Higgs boson. Using these energy scales, we determine which process is more sensitive to potential modifications in the Higgs sector at high-energy colliders. Within the Higgs Effective Field Theory (HEFT), we consider the Higgs cubic coupling and other interactions with and without derivatives. Any HEFT interactions predict the perturbative unitarity violation at a finite scale, and in a generic case, the minimalistic process is 2 → 3 scattering. Our analysis reveals that the energy scales for unitarity violation inV L V L →V L V L handV L V L →hhhprocesses are similar across all scenarios considered. If the backgrounds are similar,V L V L hfinal states are more feasible becauseV L V L hhas higher branching ratios in cleaner decay modes thanhhh. We also investigate HEFT derivative interactions derived from various UV models. In these cases, bothV L V L →V L V L andV L V L →hhprocesses exhibit unitarity violating behavior. We demonstrate that the energy scales for unitarity violation inV L V L final states are comparable to or even lower than those in thehhfinal state.

Physics↗
DOE OSTI2024

Decoding the B → K ν ν excess at Belle II: Kinematics, operators, and masses

An excess in the branching fraction for B + → K + ν ν recently measured at Belle II may be a hint of new physics. We perform thorough likelihood analyses for different new physics scenarios such as B → K X with a new invisible particle X , or B → K χ χ through a scalar, vector, or tensor current with χ being a new invisible particle or a neutrino. We find that vector-current three-body decay with m X ≃ 0.6 GeV—which may be dark matter—is most favored, while two-body decay with m X ≃ 2 GeV is also competitive. The best-fit branching fractions for the scalar and tensor cases are a few times larger than for the two-body and vector cases. Past measurements provide further discrimination, although the best-fit parameters stay similar. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Light dilaton in rare meson decays and extraction of its CP property

Abstract The dilatonϕis a pseudo-Nambu-Goldstone boson associated with the spontaneous breaking of scale invariance in a nearly conformal theory, and couples to the trace of the stress-energy tensor. We analyze experimental constraints on a light dilaton with mass in the MeV–GeV range from rare meson decays. New model-independent inclusive bounds for theb→sϕtransition largely exclude the parameter space of a light dilaton that could explain the muong− 2 anomaly. Despite similarities between a dilaton and a Higgs-portal scalar, the dilaton-photon coupling is enhanced compared to the Higgs-portal scalar due to contributions from loops of the conformal sector. Consequently, the shortened lifetime of the dilaton relaxes bounds fromK→π+ invisible searches at the NA62 experiment and constraints from the Big Bang Nucleosynthesis. We utilize this fact to search for the dilaton signature at a lepton collider such as the ongoing Belle II experiment. Further, we demonstrate how to extract the CP property of the dilaton using the variation of the differential cross-section ofe + e − →e + e − ϕwith the azimuthal angle between the outgoing leptons.

Physics↗