Spring 2025

February 5, 2025 (Wednesday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker: Holly Szumila-Vance
Host: Justin Stevens

Title: Nucleons in nuclei as the roadmap across scales

Abstract: Physicists seek to answer the fundamental question: How is the nucleus of an atom held together to build the matter we see? In the lower energy picture, we describe the nucleus in terms of its protons and neutrons and their exchange of mesons. In the higher energy picture, composite protons and neutrons (composed of quarks and gluons) interact through quantum chromodynamics (QCD). This residual interaction is the strong nuclear force. Through QCD we can describe the proton as a superposition of quark-gluon states that can include states of different sizes. This description naturally implies that bound protons can be different from free protons and allows for color transparency phenomena (whereby the constituent quarks are in a smaller-sized configuration). Using the high intensity electron beam at Jefferson Lab, we study the connection between these descriptions in order to understand how the strong force binds the nucleus together.

In this talk, I will present insights from recent electron scattering results as well as future experiments that directly search for evidence of color transparency and that explore the interactions and modifications that occur for bound nucleons in nuclei as complementary approaches to understanding the strong force across scales.  

February 10, 2025 (Monday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker: Devi Adhikari
Host: Justin Stevens

Title: Probing Nuclear Structure and Testing the Standard Model of Particle Physics throughParity-Violating Electron Scattering

Abstract: Parity-violating electron scattering (PVES), which measures the asymmetry in the scattering of longitudinally polarized electrons off fixed targets, has seen significant improvements in precision over the past three decades. These asymmetries are sensitive to weak neutral current interactions, mediated by the Z boson, between electrons and quarks or between two electrons. PVES has been extensively used to explore the structure of atomic nuclei and test the limits of electroweak theory (the Standard Model of Particle Physics), providing complementary insightsto direct searches for new physics at high energy colliders.

 In this talk, I will discuss parity violation in weak interactions, introduce the concept of PVES, provide a brief history of its development, and give an overview of its application in determining the neutron skin thickness of 208Pb and 48Ca nuclei. Additionally, I will discuss its use in the MOLLER experiment, which aims to explore new physics beyond the Standard Model with unprecedented precision.

February 12, 2025 (Monday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  Shujie Li
Host: Justin Stevens

Title: Probing high momentum nucleons at Jefferson Lab

Abstract: : At Jefferson Lab, we use high-energy electron beams to knock nucleons out of nuclear targets and study their momentum distributions in the initial state. A significant fraction of these knocked-out nucleons (up to 20% in heavy nuclei) have initial momenta exceeding the Fermi level. This phenomenon is primarily explained by short-range nucleon-nucleon interactions, which generate high-momentum nucleon pairs with low center-of-mass momentum within the nucleus.

Decades of experiments at SLAC and JLab have identified and quantified the contribution of 2-nucleon short-range correlations (2N SRCs) in various nuclei, revealing the dominance of deuteron-like np pairs. With the 12 GeV beam upgrade, JLab has further expanded our understanding of the abundance and isospin dependence of 2N SRCs and their connections to nuclear structure, and also become the leading facility in the search of 3N SRCs

 This talk will cover recent advancements in the study of 2-nucleon and 3-nucleon SRCs through inclusive quasi-elastic scattering experiments at JLab, and discuss how these studies provide unique insights into the modifications of quarks and gluons in the nuclear medium. 

February 17, 2025 (Monday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  Meike Kuessner
Host: Todd Averett

Title: Exploring Exotic Matter Across Experiments - An Experimentalists View

Abstract:The field of non-perturbative QCD continues to pose intriguing challenges, particularly in understanding the complex spectrum of light mesons. Among these, the search and identification of so-called exotic states exceeding the simple quark picture —such as glueballs, hybrids, and tetraquarks—remains a priority. These states hide themselves in the spectrum of broad, interfering and overlapping resonances, populating the light hadron spectrum or appear among the zoo of exotic charmonium resonances. 

As an experimentalist, it is obvious to me that advancing our understanding of the hadron spectrum requires not only superior facilities and detectors but also an approach utilizing different beams and production processes to tackle the open problems of understanding the strong interaction. Addressing this challenge requires actually a collaborative approach, combining different experimental data with advanced analysis techniques, called coupled channel analyses. 

The talk will discuss these, thereby integrating information from different production mechanisms. New software advancements complement this effort. A brief overview of the recent experimental indications of exotic hadrons will be provided in the talk. Special focus is put on specific ideas to study and hopefully pin down exotic matter. In conclusion, an outlook will be given towards unique possibilities at future and upgraded facilities.

February 24, 2025 (Monday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  Farah Afzal
Hosts: Todd Averett & Seth Aubin

Title: Light hadron spectroscopy with  photoproduction experiments

Abstract: The strong force is one of the four fundamental forces in nature and is responsible for the binding of protons and neutrons inside the atomic nu- cleus. Although in principle, the underlying dynamics of the constituents inside the nucleons, i.e. the quarks and gluons is described by quantum chromodynamics (QCD), the generation of confined states i.e. hadrons, which are classified as baryons and mesons, is not well understood. Ac- cording to the constituent-quark model, a conventional baryon is com- posed of three quarks and a conventional meson consists of one quark- antiquark pair. One way to shed light on the non-perturbative regime of QCD is to investigate the hadron excitation spectrum.

Predictions from first principles in lattice QCD or from quark models ex- pect a dense light baryon spectrum which is not observed in experimental data. Experimenal facilities like the A2 experiment in Mainz and the CBELSA/TAPS experiment in Bonn use photon beams with energies of up to 3 GeV to explore the light-baryon spectrum. 

Higher photon beam energies of up to 12 GeV are used at the GlueX experiment located in Hall D of Jefferson Lab, which allows to study the spectrum of light-quark mesons and in particular to look for more com- plicated meson configurations like hybrid mesons, where gluonic degrees of freedom contribute to the quantum numbers of the meson, resulting in exotic quantum numbers for some of them. Mapping out the spectrum of hybrid mesons is especially important in understanding the role gluons play in the hadron spectrum. I will give an overview of the on-going ex- perimental efforts in the field of light hadron spectroscopy with different photoproduction experiments.

March 7, 2025 (Monday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  David Ehrenstein
Host: Jozef Dudek

Title: How to Communicate Science to Non-Scientists

Abstract: The number one mistake physicists make when speaking with non-scientists is saying too much. We know not to use technical terms, but we can get caught up in our excitement over the topic and find ourselves getting into too many details. Or we forget how much background is needed to understand the "interesting" part. I will give my tips on how to avoid the glazed eyes we have all experienced in our audiences at one time or another—either in formal lectures or in conversations. I will also discuss how we at Physics Magazine choose which physics papers to cover and how we explain them in simple terms. Finally, I will talk about careers in science communication and how to start in the field. 

March 28, 2025 (Friday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  Daniel Kaplan
Host: Enrico Rossi 

Title: The Quantum Geometric Revolution in Condensed Matter Transport

Abstract: A fundamental probe of electrons in solids is charge transport: the motion of particles under the influence of external fields. For over a century, transport measurements have served as an indispensable tool for examining quantum effects in condensed matter. Among transport triumphs are superconductivity, magnetism, ferroelectricity and topological properties of materials.

Recently, theoretical and experimental efforts have been focused on understanding transport phenomena and by extension collective electronic behavior through the lens of geometry: reintroducing concepts familiar from general relativity and other areas of physics and mathematics to the study of coherent electron propagation in solids. This is now broadly termed "quantum geometry".

Here, I will review the strides made in this direction. I will show how geometric objects (such as metrics and curvatures) naturally appear in observables such as charge conductivities, electron-lattice coupling and the capacitance of insulators. I will then present recent breakthrough in understanding quantum geometry through particular emphasis on nonlinear charge current response. I will survey new materials that have challenged our prevailing understanding of transport: flat-band Moir\'e materials, topological antiferromagnetic metals and superconductivity in transition-metal dichalcogenides. 

Fundamentally, I will explain how optical responses and light-matter interaction are connected with the (non-trivial) metric and curvature of electronic wavefunctions in periodic systems. This allows using optical probes for sensitive examination of the symmetry of correlated states of matter — such as superconductors. I will present an example in which photocurrents directly sense the order parameter of high-temperature superconductors.

As an outlook, I will show practical and conceptual advances that are enabled by quantum geometry: sliding ferroelectricity, vibrational anharmonicity in solids and gravity analogues realized in materials. I will conclude by demonstrating a novel measure of distances (a metric) in neural networks which has been used to predict two novel superconductors using AI.

 April 4, 2025 (Friday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  Marianna Safronova
Host: Seth Aubin

Title: Quantum Technologies for New-physics Searches in the Laboratory and in Space

Abstract: The extraordinary advances in quantum control of matter and light have been transformative for atomic and molecular precision measurements enabling probes of the most basic laws of Nature to gain a fundamental understanding of the physical Universe. Exceptional versatility, inventiveness, and rapid development of precision experiments supported by continuous technological advances and improved atomic and molecular theory led to rapid development of many avenues to explore new physics. I will give an overview of atomic physics searches for physics beyond the standard model (BSM) and focus on dark matter searches with atomic and nuclear clocks and new ideas for BSM searches with quantum sensors in space.  

In conclusion, I will describe new efforts in developing a roadmap for terrestrial very-long-baseline (km-scale) atom interferometry for gravitational wave and dark matter detection.

April 11, 2025 (Friday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker:  Rachel Hyneman
Host: Patricia Vahle

Title: Probing Higgs Boson Self-Interactions at the ATLAS Experiment

Abstract: As the most recently discovered fundamental particle, the Higgs Boson offers many promising avenues towards further understanding our universe. One special avenue of study is in measuring the Higgs Boson's interactions with itself, which have significant implications for both the microscopic and macroscopic nature of the universe we inhabit. In this talk, I will discuss how we study the Higgs self-interaction through measurements of the production of pairs of Higgs Bosons at the ATLAS experiment at the Large Hadron Collider. I’ll focus on how we can use machine learning to measure the “impossible” final state in which both Higgs bosons decay to two b-quarks. I’ll then discuss prospects for improving future Higgs Boson self-interaction studies in ATLAS. 

April 18, 2025 (Friday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker: Ruixing Zhang
Host: Enrico Rossi  

Title: Majorana Quasiparticles in Superconducting Vortices

Abstract: Type-II superconductors respond to an applied magnetic field by generating quantized Abrikosov vortices. Recently, it has been realized that, under special conditions, these vortices can trap non-Abelian fractionalized quasiparticles known as Majorana zero modes (MZMs), offering a promising platform for topological qubits. In this talk, I will explore how vortex-trapped MZMs can emerge in superconductors with conventional s-wave pairing symmetry. In particular, I will discuss recent experimental advances in high-Tc​ iron-based superconductors such as Fe(Te,Se) and LiFeAs, along with our theoretical efforts to resolve puzzling observations in LiFeAs. If time permits, I will also discuss key challenges and future directions in this rapidly evolving field.

April 25, 2025 (Friday) 4:00-5:00 p.m.
Location: Small Hall 111 
Speaker: Antonino Di Piazza
Host: David Stark 

Title: Modern Tests of Quantum Electrodynamics in the Strong-field Regime

Abstract: Quantum electrodynamics (QED) is a well-established physical theory and its predictions have been confirmed experimentally in various regimes and with extremely high accuracy. However, there are still areas of QED that deserve theoretical and experimental investigation, especially when physical processes occur in the presence of intense background electromagnetic fields, i.e., of the order of the so-called “critical” field of QED .

After a broad introduction on strong-field QED and I focus on two prominent theoretical examples of currently open problems in the field: The problems of radiation reaction and that of vacuum polarization . Then, I will show how a newly-developed technology, “flying focus laser beams” (FFBs), can be employed as a tool to test QED in the strong-field regime and, in particular, its predictions on radiation reaction and vacuum polarization. In FFBs, in fact, the velocity of the focus can be “programmed” and it is independent of the group and the phase velocity of the beam itself. Specifically, by considering either an ultrarelativistic electron beam or a high-energy photon beamcounterpropagating with respect to a FFB, whose focus copropagates with the electrons/photonsat the speed of light, we show that radiation-reaction and vacuum-polarization effects can be rendered measurable at much lower intensities than conventionally required in a similar setup.

In the last part of the talk, I will describe the main features of a multipetawatt laser facility
which is currently under design in Rochester: NSF OPAL