Speaker: John Terning
Title: Abelian Instantons
Room: 3024
Host: John Terning
Abstract: It is usually assumed that 4D instantons can only arise in non-Abelian theories. One can, however, explicitly construct instantons for QED in the background of a Dirac monopole. This is the low-energy effective field theory for fermions interacting with a 't Hooft-Polyakov monopole. This theory posesses both a topological instanton number and 't Hooft zero modes. I will show how such instantons provide the underlying mechanism for the Callan-Rubakov process: monopole-catalyzed baryon decay with a cross section that saturates the unitarity bound.
User:
High-Energy Seminars
Time:
4:00pm - 6:00pm
Location:
PHY 285
Send Reminder:
Yes - 20241122
Description:
Title: Grand Challenges for Next-Generation Accelerators in Discovery Science
Abstract: Particle accelerators have driven scientific discovery for over a century, revolutionizing fields ranging from sub-atomic physics to transformative technologies. The quest for future discoveries is now pushing the next generation of accelerators and their beam parameters to unprecedented levels. These evolving demands present grand challenges in beam physics, acceleration methods, beam detection, and manipulation. Moreover, the need for cost-effective and environmentally sustainable facilities adds further complexity to accelerator design and implementation.
This presentation will explore the grand challenges that lie ahead in designing and implementing these advanced scientific instruments. Drawing from insights gained in recent long-term strategic planning efforts, we will examine innovative proposals and emerging concepts—from next-generation energy frontier colliders to future light sources. The talk will also provide a brief overview of the history of particle accelerators and their wide-ranging applications.
Title:
New constraints on WIMP dark matter from the LUX-ZEPLIN (LZ) experiment
Abstract:
Dark matter detection experiments based on liquid xenon time projection chambers have been steadily increasing in sensitivity to the weakly interacting massive particle (WIMP) over the past two decades. The LZ experiment, employing a two-phase xenon time projection chamber (TPC) containing 7 tonnes of liquid xenon, leads the way. Recently, the collaboration released new results from a combined analysis using data from the 2022 and 2024 science campaigns, amounting to a live exposure of 4.2 tonne-years. No evidence for an excess over expected backgrounds was found across all the test WIMP masses. The resulting limit on the spin-independent WIMP-nucleon cross, world-leading for masses above 9 GeV/c2, surpasses previous best limits by about a factor of four. In this talk, I will describe the new results---including a new technique to actively tag background electronic recoils from Pb-214 beta decays, the observation of charge-suppressed two-neutrino double electron capture events from Xe-124 decays, and the bias mitigation technique called "salting"---and sketch out what is in the horizon for liquid xenon TPC searches.
