סמינר ארצי בפיזיקה גרעינית
Zoom: https://us02web.zoom.us/j/81348832564?pwd=km3avb64d8IYJosbn1tubHZV9s5yCx.1
PROGRAM:
14:00 - 14:30 - Refreshments
14:30 - 15:30 - Tribute to Henry Primakoff: Tests of Chiral Perturbation Theory via Primakoff Reactions, Murray Moinester, Tel Aviv University
Abstract: I review experimental tests of three-flavor (u,d,s) chiral perturbation theory (ChPT). These include measurements of pion and kaon polarizabilities, the chiral anomaly amplitudes for processes such as γ→πππ, γ→ππη and γ→KKπ, as well as the lifetimes of the neutral pion and eta. These observables are extracted primarily through ultra-peripheral Primakoff scattering of high-energy particles from virtual photons in the Coulomb field of nuclei. Comparing data to two-flavor and three-flavor predictions allows us to evaluate how well ChPT describes light meson dynamics and the role of the strange quark in spontaneous chiral symmetry breaking.
15:30 - 16:00 - Coffee break
16:00 - 17:00 - Measurement of the 12C(p, 2p)11B Quasi-Elastic Knockout Reaction in Inverse Kinematics at High Momentum Transfer, Goran Johansson, Tel Aviv University
Abstract: In this talk, I will present two experiments performed at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia, investigating quasi-elastic proton knockout in inverse kinematics.
In the first experiment (2018), we demonstrated that tagging the residual (A-1) fragment, 11B in our case, strongly suppresses contributions from initial- and final-state interactions (ISI/FSI). Significant re-scattering of the incoming or outgoing protons typically leads to breakup of the residual fragment, making the detection of an intact residual nucleus an effective signature for clean quasi-elastic knockout events.
An open question in nuclear physics is the origin of the observed quenching of the spectroscopic strength relative to the Independent Particle Model (IPM) prediction. At low momentum transfer, both electron- and hadron-induced knockout measurements have consistently reported quenching values of approximately 60% across a broad range of nuclei. This reduction is commonly attributed to a combination of nuclear correlations — both short- and long-range — and reaction mechanism effects.
At higher momentum transfer, however, electron-scattering experiments have shown evidence for a substantial restoration of the single-particle strength, with extracted values approaching 90%. In a follow-up experiment (2022), we measured the absolute cross section of the same reaction and compared it to Independent Particle Model calculations. A quenching factor of 96±5% was extracted, consistent with the high-momentum-transfer electron-scattering results. This probe-independent behavior provides important constraints on the interpretation of spectroscopic strength and opens the door to improved theoretical descriptions of quasi-elastic knockout reactions.
