Joint particle seminar 
TYPE  Joint Particle Physics Seminar 
Speaker:  Tobioka/Pimentel 
Affiliation:  Florida S./SNS Pisa 
Organizer:  Yotam Soreq 
Date:  28.12.2022 
Time:  10:30  14:30 
Location:  Lidow Asher Peres (502) 
Abstract:  10:30  Coffee
11:00  Kohsaku Tobioka (Florida state)
“MeV Sterile Neutrinos in light of the CabibboAngle Anomaly”
The mixing angle of the quark sectors are constrained by the unitarity in the standard model. However, the recent data indicates about 3 sigma deviation from the unitarity in the mixing angle between 1st and 2nd generation downtype quarks, which is known as the Cabibbo angle anomaly. The observations include the chargedcurrent weak decays of neutron, nuclei, kaon, and the hadronic decay of taulepton. Although this seems to be an anomaly in the quark sector, the modification of the neutrino sector may ameliorate the tension because all the observations involve neutrinos. We find a reasonable solution expects a sterile neutrino of MeV mass that mixes the electrontype neutrino. The current bounds and future prospect of this scenario are also discussed.
12:00  Lunch
13:00  Guilherme L. Pimentel (SNS Pisa)
“Differential Equations for Cosmological Correlators”
I will review the “bootstrap” approach to compute primordial correlation functions in cosmology (which control the initial conditions for structure formation in the universe). This bootstrap relies on the existence of differential equations in terms of boundary momenta. I
will describe a new method to efficiently characterize and (in some sense) explain the existence of these differential equations. The method is general—in fact, it is heavily inspired by technology used in loop computations in flat space, but I will focus on cosmological correlation functions of a light scalar in power law FLRW cosmologies. It recasts the differential equation in terms of a new (somewhat magical) object, a flat connection in the boundary kinematic space. The mathematical theory of this flat connection is beautiful on its own right, and not fully developed yet. The physical information it carries — in particular, locality of the correlator — is encoded in its structure in a way that I don’t fully understand.
