Colloquium Calendar

Title: Theory precision for collider explorations

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Precision physics has played a crucial role in the history of particle physics, often providing indirect evidence for particles that have been later on discovered. Current experiments at the Large Hadron Collider (LHC) are stress testing the Standard Model and probing new physics with great precision through a multitude of measurements. Future colliders will extend the reach of the LHC either by higher luminosity or higher energy. To fully enable the discovery potential of current and future colliders, theoretical precision at an unprecedented level is essential. In this talk I will motivate this statement and discuss how precision collider phenomenology requires a comprehensive approach to the theoretical description of collider events.

Title: Scouting for light new physics

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The two most common ways particle physicists are searching for the existence of new forces or new degrees of freedom are either by producing heavy new particles directly, using collisions at the highest achievable energies, or by measuring precisely processes that are very rare. In the colloquium I will review the third possibility that is coming more and more to the fore: if we are lucky enough that light new particles can be produced in the very rare processes, this will open a window to physics at very small scales. Using intuition from condensed matter and atomic physics systems I will explain why in this case there is a parametrically enhanced sensitivity, and review experimental efforts under way to search for such particles. 

Title: Astronomy on the Hill: Federal Funding and Dark & Quiet Skies Policy

Abstract: The landscape of federal science policy has shifted dramatically over the past year. As the FY2026 federal funding cycle concludes, this talk will provide a brief overview of the current fiscal situation for the astronomical sciences, as well as an outlook for FY2027 and beyond. We will then examine the Dark & Quiet Skies initiative, a global effort to preserve the night sky from light pollution and radio frequency interference from satellites. We will review recent regulatory developments in the space environment and highlight how the astronomical community works with commercial space operators and the federal government to ensure a sustainable orbital environment. The talk concludes with a discussion of how scientists at all career stages can engage with policymakers to ensure astronomy and science remains a priority on Capitol Hill.

Title: Neutrino angle reconstruction in MicroBooNE for precision atmospheric neutrino oscillations 

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We investigate the expected precision of the reconstructed neutrino direction using a 𝜈𝜇-argon quasielasticlike event topology with one muon and one proton in the final state and the reconstruction capabilities of the MicroBooNE liquid argon time projection chamber. This direction is of importance in the context of DUNE sub-GeV atmospheric oscillation studies. MicroBooNE allows for a data-driven quantification of this resolution by investigating the deviation of the reconstructed muon-proton system orientation with respect to the well-known direction of neutrinos originating from the Booster Neutrino Beam with an exposure of 1.3 ×10^21 protons on target. Using simulation studies, we derive the expected sub-GeV DUNE atmospheric-neutrino reconstructed simulated spectrum by developing a reweighting scheme as a function of the true neutrino energy. We further report flux-integrated single- and double-differential cross section measurements of charged-current 𝜈𝜇 quasielasticlike scattering on argon as a function of the muon-proton system angle using the full MicroBooNE data sets. We also demonstrate the sensitivity of these results to nuclear effects and final state hadronic reinteraction modeling.

Short bio: Afroditi (Papadopoulou) got her undergrad degree at the University of Athens in 2016 while carrying out an analysis using 7 TeV CMS data. She then moved to MIT for her graduate school studies where she worked in collaboration with Prof. Or Hen. Her PhD included analyzing both neutrino data collected by the MicroBooNE detector at Fermilab in Illinois and electron scattering data at Jefferson Lab in Virginia. After her graduation in 2022, she joined Argonne National Lab as a Mayer Fellow where she is continuing her research as a member of the MicroBooNE, SBND, DUNE, and Electrons-For-Neutrinos collaborations, as well as testing performance of simulation predictions against existing and new neutrino and electron data sets. She is currently a Robert Oppenheimer fellow at LANL working on improving our understanding of neutrino interactions and will start as an assistant professor at Georgia Tech in August 2026.

Title: Do All Galaxies Form Stars the Same Way?

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Current techniques for analyzing distant galaxies are generally forced to assume a single, universal stellar initial mass function (IMF). However, the IMF is predicted to depend upon the sound speed in star-forming molecular clouds, and thus should be expected to vary depending upon conditions within a star-forming galaxy. The introduction of an additional parameter into photometric template fitting allows galaxies to be fit with a range of different IMFs. Three surprising new features appear: (1) most star-forming galaxies are best fit with a bottom-lighter IMF than the Milky Way; (2) most star-forming galaxies at fixed redshift are fit with a very similar, but non-Milky Way IMF; and (3) the lowest-mass star-forming galaxies appear to exhibit a distinct relationship between IMF and star formation rate, possibly hinting at distinct feedback mechanisms in the earliest stages of star formation. This also points to the possibility that most stars are made not in blue, luminous galaxies as previously thought, but in a previously undiscovered population of intrinsically red star-forming galaxies which are only capable of forming low-mass stars. Finally, I will show new, direct evidence for environmentally-driven IMF variation in the Milky Way.

Title:The Dynamic Lives of Radio AGN: New Insights from Modern Surveys

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Radio jets and lobes launched by active galactic nuclei (AGN) and quasars are thought to play a key role in shaping the evolution of galaxies.  To understand how quasar jets are triggered, grow, and interact with their environments, it is essential to identify them in the early stages of their evolution, when they are still compact and confined within their host galaxies.  Despite their significance, young quasar jets have historically been difficult to identify unambiguously due to observational limitations.  In this talk, I will present new strategies for identifying young and compact AGN jets using modern radio telescopes, instruments, and surveys that combine multi-epoch, broadband observations with wide-area sky coverage.  I will describe the recent discovery of a surprisingly high fraction of short-lived or intermittent jets revealed by the Very Large Array Sky Survey (VLASS) and highlight new insights from multiwavelength follow-up observations with facilities such as the Hubble Space Telescope.  Finally, I will discuss new and forthcoming opportunities to further advance our understanding of the life cycles of AGN and their jets.

Title: Knocking on the Nu Doors with LArTPCs

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The neutrino sector is a frontier of discovery in particle physics. With the origin of neutrino masses remaining a primary question, neutrino oscillation phenomena play a critical role in solving mysteries surrounding neutrino properties and bringing us closer to understanding the matter/anti-matter asymmetry of the universe. As multiple flagship neutrino oscillation experiments enter operation through the late 2020s and 2030s, Liquid Argon Time Projection Chamber (LArTPC) detector technology will play an essential role over the next couple of decades. This talk will cover the operating principles of the LArTPC, its current landscape in neutrino oscillation measurements, and the latest efforts to maximize its potential for future physics discoveries.

Title: Diamond Quantum Sensing Microscopy of van der Waals Magnets
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Diamond quantum sensing microscopy based on nitrogen vacancy (NV) centers in diamond has become a powerful tool to detect weak magnetic fields with unprecedented spatial resolution  (≤ 40 nm),  sensitivity (pT-T/Hz-1/2), and dynamic range (Hz-100 GHz), opening new doors to study nanoscale magnetic phenomena in low-dimensional materials [1-2]. First, I provide an overview of NV physics and describe some basic NV magnetometry protocols [1-2]. Then, I discuss recent results from my group in using NV-based magnetic microscopy to study van der Waals (vdW) magnets.

Tungsten disulfide (WS2), a member of the transition-metal dichalcogenides family, has primarily garnered attention for optoelectronic applications for its tunable bandgap, which changes from indirect to direct when transitioning from bulk to monolayer form [3]. Magnetic bulk measurements have indicated a weak ferromagnetic response in WS2 powder [4] and theoretical predictions suggested that the edges of such nanoflakes exhibit magnetization when at least one edge of a flake is partially hydrogenated [4]. In this study, we examine pristine and Fe-implanted WS2 flakes of 45 – 160 nm thickness, exfoliated from bulk WS2 and transferred to NV-doped diamond films. We provide the first direct evidence of edge-localized stray magnetic fields, growing linearly with the applied magnetic field [5]. Magnetic simulations using five alternative models favor the presence of edge magnetization aligned along an axis slightly tilted from the normal to the WS2 flake's plane, consistent with spin canting in antiferromagnetically coupled edge states [5]. These findings establish WS2 as a promising platform for edge-controlled 2D spintronics.

Chromium(III) chloride (CrCl3), a vdW magnet, consists of 2D layers of magnetically active Cr3+ arranged in a honeycomb lattice form, surrounded by octahedrally coordinated Cl ions [6-7]. CrCl3 exhibits two closely spaced magnetic phase transitions on cooling: paramagnetic-ferromagnetic (TC ~17 K) and ferromagnetic-antiferromagnetic (TN ~13 K) [6]. Here, we study the magnetic behavior of thin (thickness ~ 20 – 70 nm) CrCl3 flakes using NV magnetometry across these magnetic phase transitions. Within the ferromagnetic phase, the amplitude of NV Rabi oscillations collapsed, and spin-lattice relaxation time (T1) is reduced by approximately two orders of magnitudes, indicating a strong spin-wave bath dynamics spanning in the GHz frequency regime. NV relaxation rate (1/T1) versus temperature measurements show a lambda-like anomaly near the paramagnetic–ferromagnetic transition, evidence of enhanced GHz magnetic fluctuations near the Curie Temperature. In addition, temperature-dependent broadband ferromagnetic resonance measurements show a linewidth broadening in the ferromagnetic regime, further supporting the NV findings [8].

[1] F. Casola, et al.,  Nat. Rev. Mat. 3, 17088 (2018). [2] A. Laraoui, at al., App. Phys. Lett. 121, 060502 (2022). [3] J. Luo, et al., App. Phys. Lett. 124, 033104 (2024). [4] N. Huo, et al., Appl. Phys. Lett. 104, 202406 (2014). [5] I. Fescenko, A. Laraoui, et al., Adv. Fun. Mat. 35 (38), e71467 (2025). [6] A. Bedoya-Pinto, et al., Science 374, 616– 620 (2021). [7] J. Wang et al., Advanced Science 10 (3), 2203548 (2023). [8] B. Hammons, J. Kumar, A. Laraoui, et al., under preparation.

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