Session C01: Charm and Neutrino Physics

Charm lifetime measurements and other first results from Belle II

Upgrades at the Belle II experiment and the SuperKEKB asymmetric-energy electron-positron collider enable precise measurements of particle decays. Even with early data, Belle II has made several world-leading measurements of particle lifetimes, which are useful as tests of effective models that are used in searches for physics beyond the standard model. Especially for charm hadrons, these effective models depend on careful consideration of non-perturbative effects to give an adequate description of lifetimes. I will review recent measurements of charm baryon lifetimes that will improve the world-average values, provide refined tests for effective models, and serve as benchmarks for future measurements. I will also detail other first measurements with early Belle II data and explore some future prospects.   

CP asymmetry measurement in charm baryon decay $Xi_c^+ o Sigma^+ h^+ h^-$ with Belle II simulation.

A necessary condition for the observed matter/antimatter imbalance in our universe is violation of Charge Parity (CP) symmetry. However, the observed amount of CP violation is insufficient by orders of magnitude. Searches for new sources of CP violation are currently ongoing in different sectors, but primarily in meson decays. There are few studies of CP asymmetry in the baryon sector. We will present one such measurement of CP asymmetries in the singly-Cabibbo-suppressed charm baryon decay $Xi_c^+ o Sigma^+ h^+ h^-$ with Belle II simulations.   

Amplitude analysis of Ξ0c → Λ0 K− π+

The Belle II experiment at the SuperKEKB asymmetric e⁺e⁻ collider in Tsukuba Japan is designed to make precision measurements in flavor physics at the “intensity frontier”. Low backgrounds with a known collision energy gives Belle II unique opportunities over other collider experiments.

The Belle experiment performed many measurements using baryon decays including Λ, Ξ⁰_c , Ξ⁺_c , and ?_c, but few have been subjected to an amplitude analysis. Since the excited Ξ spectrum is not well understood and contains potentially exotic states, an amplitude analysis of Ξ⁰_c decays has the potential to expose the presence of new states and measure their quantum numbers and other properties. This Ξ⁰_c → Λ⁰  K⁻  π⁺ decay mode has a reasonably large branching fraction (1.45%) and includes potential resonant substructure including the potentially exotic states Ξ(1690)⁻ and Ξ(1820)⁻. I will present an ongoing amplitude analysis on Ξ⁰_c → Λ⁰  K⁻  π⁺  to measure the branching fraction and spin-parity of resonant substructures using Belle II simulations.   

Recent Results from NOvA

NOvA is a long-baseline neutrino oscillation experiment that measures neutrinos originating from Fermilab's NuMI beamline. NOvA uses a combination of a near detector located at Fermilab and a far detector located in Ash River, MN. Neutrino oscillation is detected at NOvA by observing a combination of electron neutrino appearance and muon neutrino disappearance in the far detector. Neutrino oscillation is proof that neutrinos have mass that is not predicted by the Standard Model. Therefore, understanding neutrino oscillation is a key to understanding the universe, and NOvA has been instrumental in the rapid progress toward understanding. Discussed are some of the new analysis techniques the experiment has innovated with to evaluate its data in new ways. In the age of high-precision measurements, extensions of standard oscillation can be considered. One such extension involves a search for a 4th so-called sterile neutrino flavor which is otherwise undetectable. Another extension is the search for non-standard interactions of neutrinos as they pass through matter, which would change the oscillation spectrum and affect the measurement of standard oscillation parameters.   

Search for Non-Standard Interactions with Neutrino Oscillations at the NOvA Experiment

The phenomenon of neutrino oscillations provided us with hints for the so-called Physics Beyond the Standard Model, and opened a window for several and interesting new investigations in the field of neutrino physics. Among the possibilities, Non-standard interactions (NSI) are an extension of the neutrino matter effect leading to a rich phenomenology, and are expected to modify the propagation of neutrinos through matter. The current open questions in the neutrino oscillation model rely heavily on how neutrinos interact with matter, to an extent that NSI could induce possible effects. The NOvA Experiment presents its first preliminary search for flavor-changing NSI in neutrino oscillations in the 810 km baseline as neutrinos cross the Earth's crust between the Near and Far Detectors.   

Affleck-Dine Leptogenesis with One Loop Neutrino Mass and strong CP

We present a unified model that solves four major problems of the standard model i.e. neutrino masses, the origin of matter, strong CP problem, and dark matter using the framework of the Affleck-Dine (AD) mechanism. The AD field is responsible for inflation, the origin of matter, and neutrino masses which arise at the one-loop level. Neutrino masses are therefore intimately connected to the baryon to photon ratio of the universe. The dark matter in the model is the axion field used to solve the strong CP problem. The model has a near massless Majorana fermion which contributes to ΔNeff∼0.1 in the early universe, which can be tested in the upcoming CMB-S4 experiment.