Physics seminars

Jan 1, 2026, 3:00 PM → Dec 31, 2026, 5:00 PM Europe/Rome

Room 412 C - Ferrara

Tue, January 27

3:00 PM → 4:00 PM A Roadmap to Strong-Field QED: Concepts, Experiments, and the LUXE Program

Strong-field QED describes the interaction of charged particles and photons with electromagnetic fields so intense that non-linear and non-perturbative effects become experimentally accessible, enabling phenomena such as non-linear Compton scattering and non-linear Breit–Wheeler pair production. These effects are not only of fundamental interest in the laboratory but are also relevant to extreme astrophysical environments, such as the magnetospheres of neutron stars. This talk provides a roadmap of strong-field QED, introducing the key concepts and physical regimes and reviewing the main experimental approaches pursued today, including crystals, beam–beam interactions, and collisions between electrons or photons and high-intensity laser pulses. Particular emphasis is placed on the LUXE experiment at DESY, which will probe this regime with high precision using the 16.5 GeV electron beam of the European XFEL and an ultra-intense optical laser. Finally, the potential of high-energy photons from strong-field interactions for beam-dump–type new physics searches is discussed.

Speaker: Ivo Schulthess (ETH Zurich)

Wed, February 4

11:00 AM → 12:00 PM Euclid Q1 galaxy clustering and its cross-correlations with CMB lensing

Combining Cosmic Microwave Background (CMB) and large-scale structure (LSS) observations provides a powerful way to probe the evolution of the Universe from recombination to the present day, test gravity on cosmological scales, and constrain the nature of dark matter and dark energy. In this talk, I present the first measurements of galaxy clustering from the Euclid Q1 data release and its cross-correlation with CMB lensing convergence maps from Planck and the Atacama Cosmology Telescope. We detect the signal at high significance and find excellent agreement with expectations from simulations and the Planck 2018 cosmological model. I will discuss robustness tests against observational systematics, tomographic measurements, and early constraints on galaxy bias and redshift uncertainties. These results demonstrate the strong potential of Euclid–CMB cross-correlations to deliver robust cosmological constraints and to mitigate systematics in future Euclid data releases.

zoom: https://cern.zoom.us/j/65644266180?pwd=xdfyl67pQ0zfWjyFui5klxnsSRb8WZ.1

Speaker: Margherita Lembo (IAP, Paris, France)

Fri, February 6

10:00 AM → 11:00 AM Cosmic strings and domain walls: CMB constraints and the role of B-modes

Cosmic strings and domain walls are topological defects arising from the spontaneous breaking of new symmetries in the early Universe, as predicted in several beyond the Standard Model scenarios. In this talk, I will briefly introduce the physics of defect networks and discuss their impact on cosmological observables, with particular emphasis on their signatures in the Cosmic Microwave Background. I will then present constraints derived from current CMB data, highlighting in particular the role of B-mode polarization. Finally, I will outline prospects for upcoming CMB experiments and their potential to significantly improve sensitivity to topological defects.

zoom: https://cern.zoom.us/j/64532006687?pwd=Bj4hXXbb2t6MZnFlXq0vCTE4EPXrPu.1

Speaker: Luca Caloni (Universidade de Coimbra, Coimbra, Portugal)

Fri, February 13

2:30 PM → 3:30 PM Coincidence and anti-coincidence gamma ray spectroscopy in radionuclide identification

The two most challenging aspects of gamma ray spectrometry are to achieve spectral free interferences and to attain the lowest possible detection limits and ultimately low uncertainties. In nuclear forensics isotopic ratios or elemental ratios in environmental analyses need to have the individual results at low uncertainties for meaningful interpretations. Over the last decades gamma-gamma coincidence and anti-coincidence (Compton suppression) methods have been used for variety radionuclide identifications for passive counting of naturally occurring radioactive material (NORM), special nuclear materials (239Pu), fission products and neutron activation analysis (NAA) for environmental, geological, and biological samples. One real major advantage of these methods is that spectral interferences can be significantly reduced as in the case of Compton suppression or be eliminated as in gamma-gamma coincidence, while also reducing the Compton continuum and decreasing detection limits. For instance, the determination of 137Cs in soil with Compton suppression can be determined at less than 1 Bq/kg for only a twenty-gram sample. In neutron activation analysis elements such as arsenic and cadmium in biological specimens can be determined with detection limits at the ng/g level, which cannot be determined using traditional NAA methods. There are a host of elements determined by NAA that have benefitted using gamma-gamma coincidence and anti-coincidence methods. And in many cases, elements that are seldom or never reported, can now be effectively determined incorporating epithermal neutrons where the resonance integrals for several elements are high. An overview of these methods will be delineated with specific examples.

Zoom: https://cern.zoom.us/j/68713119184?pwd=HbCsVLUEbBC7JtpriZza6iUr5OylYN.1

Speaker: Prof. Sheldon Landsberger (Nuclear and Radiation Engineering Program Walker Department of Mechanical Engineering University of Texas at Austin, USA)

Fri, March 6

11:00 AM → 12:00 PM CHRONOS: A Cryogenic Sub-Hz Torsion-Bar Speed-Meter for Stochastic Gravitational-Wave Background Searches

Abstract: The sub-Hz frequency band represents one of the last unexplored frontiers in gravitational-wave (GW) astronomy. Access to this regime opens a unique observational window onto cosmological stochastic gravitational-wave backgrounds (SGWB), early-Universe phase transitions, cosmic strings, and low-frequency compact binaries beyond the reach of current ground-based interferometers.
In this talk, I will present CHRONOS (Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter), a novel interferometric concept designed to probe the 0.1–10 Hz band from the ground. CHRONOS combines a cross torsion-bar topology with a Sagnac speed-meter configuration, implementing quantum non-demolition (QND) measurement principles to suppress radiation-pressure noise at low frequencies. In contrast to conventional position-meter Michelson interferometers, the rotational speed-meter observable intrinsically modifies the quantum noise coupling, enabling stable low-frequency performance. By operating cryogenic sapphire test masses, the detector further reduces thermal noise and aims to achieve quantum-noise-limited sensitivity in the sub-Hz regime. I will first outline the interferometer topology and the associated quantum-noise behavior that distinguish rotational speed-meter measurements from traditional configurations. I will then present the projected sensitivity and noise budget of CHRONOS, highlighting the achievable performance in the sub-Hz band.
Finally, I will discuss the prospects for stochastic gravitational-wave background searches, including sensitivity projections to cosmological models. CHRONOS provides a complementary path toward extending terrestrial gravitational-wave detection into the sub-Hz domain, bridging the frequency gap between existing ground-based detectors and future space missions, and opening new opportunities for probing fundamental physics and cosmology.

zoom: https://cern.zoom.us/j/63349754507?pwd=TbxHYvQV1jCX5YIHHDYYfua1DdEwpP.1

Speaker: Yuki Inoue (National Central University, Taiwan)

Tue, March 10

3:00 PM → 4:00 PM Fundamental Physics with Cosmic Microwave Background Observations

Particle cosmology aims to uncover the fundamental laws of physics that govern the Universe. Our research today is driven by five outstanding mysteries: cosmic inflation, baryon asymmetry, neutrino properties, dark matter, and dark energy. In addition, two recent observational hints—possible parity violation in cosmological signals and indications of dynamical dark energy—suggest that new physics may be within reach. Resolving any of these questions would profoundly transform particle physics and our understanding of the Universe.
Among the many observational probes, measurements of the cosmic microwave background (CMB) play a key role. After reviewing past CMB observations, I will introduce the projects I am currently involved in, with particular emphasis on the Simons Observatory and LiteBIRD. I will conclude by discussing the emerging synergy between CMB measurements and gravitational-wave observations, and how their combination may open new windows onto fundamental physics.

Zoom: https://cern.zoom.us/j/67644485998?pwd=xWBE2XzKEioRiXMwMCnaAxGMXJ7LXG.1

Speaker: Masashi Hazumi (INFN Visiting Scientist on leave from KEK/IPNS Tsukuba)