Current dates

04. Week 2021


Wednesday, 01.27.

Gentner Colloquium for Astroparticle Physics

Time, Place:

16:00 ,https://zoom.us/j/99917364979?pwd=ejR5dXFjWmhZNWE2YmJlbVBTL2RFUT09

Speaker:

Associate Prof. Dr. Abigail Vieregg (University of Chicago, USA)

Title:

Discovering the Highest Energy Neutrinos With Radio Phased Arrays

The detection of high energy astrophysical neutrinos is an important step toward understanding the most energetic cosmic accelerators. IceCube, a large optical detector at the South Pole, has observed the first astrophysical neutrinos and identified at least one potential source. However, the best sensitivity at the highest energies comes from detectors that look for coherent radio Cherenkov emission from neutrino interactions. I will give an overview of the state of current experimental efforts, including recent results, and then discuss a suite of new experiments designed to discover neutrinos at the highest energies and push the energy threshold for radio detection down to overlap with the energy range probed by IceCube, thus covering the full astrophysical energy range out to the highest energies, and opening up new phase space for discovery. These include ground-based experiments such as RNO-G and IceCube-Gen2, as well as the balloon-borne experiment PUEO.

Thursday, 01.28.

Teekolloquium

Time, Place:

11:15 ,https://zoom.us/j/97726408385?pwd=SG1odkprSC91T01HRFl0amtEa1QxZz09

Speaker:

Dr. Anna Nelles, FAU Erlangen/DESY Zeuthen

Title:

Radio Detection of Astrophysical Neutrinos

Meeting-ID: 977 2640 8385Kenncode: 291628Abstract:The past years have shaped multi-messenger astronomy. Coincidences between all messengers from the universe have advanced our understanding of explosive events and the sources of ultra-high energy (UHE) cosmic rays. However, the number of detected astrophysical neutrinos remains small and the energy range restricted to less than 100 PeV. At higher energies, neutrinos are expected to be direct products of the interaction of UHE cosmic rays either in the sources directly or from interactions with the various photon backgrounds. To reach these energies detectors with effective volumes of several 100 km3 are needed. Optical detection methods are limited by the attenuation length, so a change in technology is needed. I will describe how radio detection of neutrinos works, how it can reach these effective volumes and how we plan to construct detectors that will allow us to add more and higher-energy neutrinos to the multi-messenger mix.

05. Week 2021


Monday, 02. 1.

Seminar Dynamik und Struktur von Atomen und Molekülen

Time, Place:

09:30 ,https://zoom.us/j/93333632840?pwd=dFAyYVo3VFVpcHFpZzA0R2pFeXh6QT09

Speaker:

Gergana D. Borisova, Excited atoms and molecules in strong fields, MPIK

Title:

Strong-field ionization of FEL-prepared doubly excited states in the helium atom

Meeting-ID: 933 3363 2840Kenncode: 003580

Particle and Astroparticle Theory Seminar

Time, Place:

16:30 ,https://zoom.us/j/94379329096?pwd=MEYxRit5aXBkMU1ZcFVuUVhyMGt4Zz09

Speaker:

Dr. Manibrata Sen (UC, Berkeley)

Title:

Fundamental physics with the diffuse supernova background neutrinos

Wednesday, 02. 3.

Bothe-Kolloquium

Time, Place:

16:15 ,https://zoom.us/j/92548552219?pwd=UCs5RFVlcGpzZWdpb0ZhYUUxUWdkZz09

Speaker:

Prof. Daniel Fischer, Missouri University of Science and Technology

Title:

Controlling and analyzing dynamics in atomic few-photon ionization

Achtung: Geänderte Zeit!Meeting-ID: 925 4855 2219Kenncode: 505342Understanding the dynamics in systems of several interacting particles is one of the key challenges of physics. Such systems generally cannot be described in closed analytical form as soon as more than two particles are involved. This dilemma is well-known as the "few-body problem" which sets us close limits to accurately predicting a many-particle system's state. Therefore, the advancement of our knowledge of phenomena that emerge due to the complex interplay of several particles requires the joined theoretical and experimental exploration for a wide range of situations. The fragmentation of atoms due to the interaction with intense light fields represent an ideal test ground of few-body physics for several reasons: First, few-body effects in these systems are ubiquitous and relevant to many research fields and numerous technical applications, particularly in areas such as materials science, quantum chemistry, biological science, and information processing. Second, advanced experimental techniques are available which allow manipulation of the parameters of the few-particle quantum state with a high degree of control and accuracy. Momentum Spectrometers enable snapshots to be taken of the state's change over time, providing access to the details of the atomic dynamics. In this talk, I will report on experiments that combine some of the most advanced experimental methods for the control and analysis of atomic few-body systems: We prepare an atomic lithium target a spherically symmetric s or in a polarized p state using laser cooling and manipulation techniques. A versatile femtosecond light source with a wavelength tunable between about 350 and 1000 nm ionizes the atomic target by the absorption of one or few photons. A Reaction Microscope is employed allowing the coincident measurements of the momentum vectors of the atomic fragments after the ionization. In a first series of experiments, we addressed fundamental questions about light-matter interaction, e.g., how can the electron emission characteristics be controlled by the laser pulse properties? How to extract phase and amplitude information on the ejected electrons' wave functions? How does the ionization dynamics depend on the relative orientation (or helicity) of the target and a projectile ion or ionizing laser field? Such experiments do not only help to understand fundamental symmetries, which play a crucial role in many processes occurring in nature, but they provide versatile tools, which enable e.g., to create spin-polarized electron pulses with a reversible switch on a femtosecond timescale at an energy resolution of a few meV.