Dr. Shoji Hashimoto, KEK
Where: Sessler Conference Room (50A-5132) and Zoom (link to come)
When: 3:30pm, Coffee, Tea and cookies
4:00, Colloquium
Zoom link - https://lbnl.zoom.us/j/91213527904?pwd=clB4eFUzcURNMGx2K2ZsQTlrT0l0UT09
and info: Meeting ID - 912 1352 7904 password 940256
It's been almost 50 years since Quantum Chromodynamics (QCD), or its asymptotic freedom, was found. Yet, the quantitative understanding of quark-hadron duality, an underlying assumption in the connection between perturbative QCD and experiments, is lacking. The duality implies that the QCD processes summed over all final hadronic states can be calculated with quarks (and gluons) as fundamental degrees of freedom. But, what is the associated systematic uncertainty? That should be able to be answered using lattice QCD, which allows us to perform fully non-perturbative computation. We discuss how this can be done taking a few examples including the inclusive semi-leptonic B meson decays.
Dr. Shujie Li, LBNL
Where: Sessler Conference Room (50A-5132) and Zoom (link to come)
When: 3:30pm, Coffee, Tea and cookies
4:00, Colloquium
Nucleons being close together causes hard interactions due to the short (repulsive) and medium (tensor) range forces, creating energetic nucleon pairs. Understanding these high momentum nucleon pairs is important for both the realistic description of nuclear structures and for studying the transition between partonic to nucleonic degrees of freedom. In electron scattering experiments, the nucleon-nucleon short-range correlation (SRC) pairs are identified by their large initial momentums. Previous measurements at Jefferson Lab had observed a strong isospin-dependence of those pair configurations in light and heavy nuclei and found strong np dominance, i.e. almost entirely neutron-proton SRCs. I will present the results from a recent Jefferson Lab measurement on the mirror nuclei tritium and helium-3 which finds a much smaller np enhancement with high precision. This indicates the strong nucleon-nucleon interaction is sensitive to the nuclear environment. In this talk I will give an overview of the tritium SRC experiment setup, present it’s unexpected results, and discuss their implications and some future experiments to study nucleon-nucleon interactions and in-medium modifications.
Dr. Bjoern Lehnert, LBNL
https://scholar.google.com/citations?user=2DpYg28AAAAJ&hl=en
Where: Pers-Hall (Cafeteria Building) 54-1-130 - zoom link
When:
3:30, Coffee, Tea and cookies on the Pers-Hall Balcony
4:00, Colloquium
Since the Nobel prize-winning discovery of neutrino oscillation, we know that neutrinos have a non-zero mass. However, the absolute mass scale of the most abundant matter particle in the Universe remains unknown. Three fundamentally different approaches aim to determine the neutrino mass: Global fits to cosmological data, neutrinoless double beta decay, and kinematic measurements. The latter is the most direct way to determine the mass of the neutrino and is investigated with tritium beta decays in the Karlsruhe Tritium Neutrino (KATRIN) experiment.
KATRIN performs spectroscopy of beta-electrons near the tritium endpoint at 18.6 keV by employing a high intensity windowless gaseous tritium source and a high-precision electrostatic spectrometer. The required sensitivity demands novel hardware operating with unprecedented stability and a precise understanding of all systematic effects and their correlations. KATRIN started data taking in 2019 and continues to run through 2024. I will present the measurement strategy and the latest results. In the end I will give an outlook on future data from KATRIN and neutrino mass measurements beyond.
Dr. Tetsuo Hatsuda, RIKEN
https://ithems.riken.jp/en/members/tetsuo-hatsuda
Where: Pers-Hall (Cafeteria Building) 54-1-130 - zoom link
When:
3:30, Coffee, Tea and cookies on the Pers-Hall Balcony
4:00, Colloquium
Recent progress in hadron-hadron interactions with lattice QCD simulations close to the physical pion mass opens the door for quantitative studies of the poorly understood hyperon-nucleon and hyperon-hyperon interactions at low energies. It also allows comparison with femtoscopic studies in pp, pA, and AA collisions at RHIC and LHC. After an overview of the basic theoretical concepts of the HAL QCD method for extracting hadronic interactions from lattice QCD, interplay between theoretical and experimental studies will be presented, taking hyperon interactions such as Lambda-Lambda, N -Xi, N - Omega, and Omega -Omega as examples. The ongoing program of physical point lattice QCD simulations using RIKEN's FUGAKI, the world's fastest computer, will also be mentioned.
Dr. John Arrington, Physics Division, Argonne National Laboratory
Nuclei form the core of matter, but their description in terms of their fundamental constituents - quarks and gluons - remains elusive. The Jefferson Lab program has provided key insight into nuclear structure at extreme energy and density scales. A connection between high-density configurations and the quark structure of nuclei has raised significant questions about the modification of protons and neutrons within nuclei with potential impact on our understanding of neutron stars, neutron structure, and a range of high-energy e-A, nu-A, and A-A scattering measurements.
I will summarize our current understanding based on electron scattering measurements, highlight the impact of these studies and key outstanding questions, and discuss future measurements making use of the Jefferson Lab energy upgrade and the future Electron-Ion Collider.
Prof. Laura Baudis, University of Zürich, visiting UC Berkeley
One of the major challenges of modern physics is to decipher the nature of dark matter. Astrophysical observations provide ample evidence for the existence of an invisible and dominant mass component in the observable universe. The dark matter could be made of new, yet undiscovered elementary particles, with allowed masses and interaction strengths with normal matter spanning an enormous range. Among these, particles with masses in the MeV-TeV range could be directly observed via elastic or inelastic scatters with atomic nuclei or with electrons in ultra-low background detectors operated deep underground. After an introduction to the dark matter problem and the phenomenology of direct dark matter detection, I will discuss the most promising direct detection techniques, addressing their current and future science reach, as well as their complementarity.
