Semesterübersicht – nächstes Semester

Metastable antiprotonic helium is an exotic atom composed of a helium nucleus, electron, and an antiproton. It is among the hadron-antihadron systems with the longest known lifetimes. Laser light can be used to excite atomic transitions involving the antiproton orbital. By utilizing sub-Doppler two-photon laser spectroscopy and buffer gas cooling, its atomic transition frequencies were measured to ppb-scale precision. Comparisons with the results of QED calculations allowed the antiproton-to-electron mass ratio to be determined as 1836.1526734(15). The results were used to set upper limits on fifth forces between antiprotons and nucleons at atomic length scales, and on forces that may arise between an electron and antiproton mediated by hypothetical bosons. Efforts are currently underway to improve the experimental precision using CERN’s ELENA facility. We also observed narrow spectral lines of these atoms formed in superfluid helium with a surprisingly high spectral resolution of 2 parts per million. This revealed the hyperfine structure arising from the spin interaction between the antiproton and electron, despite the atom being surrounded by a dense matrix of normal atoms. Metastable pionic helium (πHe+) contains a negative pion occupying a state of n≈l-1≈17, and retains a 7 ns average lifetime. We recently used the 590 MeV ring cyclotron facility of Paul Scherrer Institute to synthesize the atoms, and irradiated them with infrared laser pulses. This induced a pionic transition within the atom and the π- being absorbed into the helium nucleus. This constitutes the first laser excitation and spectroscopy of an atom containing a meson. By improving the experimental precision, the pion mass may be determined to a high precision as in the antiproton case.

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High performance computing, many-body methods with polynomial scaling, and ideas from effective-field-theory is pushing the frontier of ab-initio computations of nuclei. Here I report on advances in coupled-cluster computations of nuclei starting from chiral Hamiltonians with two- and three-nucleon forces. The ab-initio approach can now be used to address fundamental questions related to the nature of the neutrino by accurate computations of neutrino-less double beta decay and making first steps towards neutrino-nucleus scattering on relevant nuclei. Global surveys of bulk properties of medium-mass and neutron- rich nuclei from ab-initio approaches are now possible by using reference states that break rotational symmetry. These calculations have revealed systematic trends of charge radii in various isotopic chains, questioned the existence of certain magic shell closures in neutron-rich nuclei, and confrontation with data have exposed challenges for ab- initio theory. By restoring rotational symmetry, we have made predictions for the rotational structure of neutron-rich neon isotopes including 32,34Ne. In addition to entire regions of the nuclear chart now being targeted by ab-initio computations, entirely new ways to make quantified predictions are becoming possible by the development of accurate emulators of ab-initio calculations. These emulators reduce the computational cost by many orders of magnitude allowing for billions of simulations of nuclei using modest computing resources. This allows us to perform global sensitivity analysis, quantify uncertainties, and use novel statistical tools in predicting properties of nuclei. Recently we used these tools to make a quantified prediction of the neutron skin in 208Pb, and found that the neutron-skin is smaller and more precise than a recent extraction from parity-violating electron scattering but in agreement with other experimental probes. We have also used these tools to address the questions of what drives deformation in atomic nuclei and whether 28O is a bound nucleus. These developments demonstrate how realistic two- and three-nucleon forces act in atomic nuclei and allow us to make quantitative predictions across the nuclear landscape.

Using the idea of a field guide as a template, the referent will briefly review the rapidly expanding catalog of known mesons, which are strongly interacting subatomic particles made from equal numbers of quarks and antiquarks. While most mesons can be successfully described as one quark bound to one antiquark, recent discoveries point towards the existence of new meson families. These discoveries, made at experiments such as the BESIII e+e- experiment in Beijing and the LHCb pp experiment at the LHC, offer new contexts in which to study the strong force of particle physics.

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The development of atomic quantum simulation platforms has led to the creation of a new generation of programmable quantum simulators that can be scaled to large particle numbers while maintaining a certain degree of programmability. This talk reports on theory-experiment collaborative work using trapped ion platforms with up to fifty-one qubits/spins, where we develop and demonstrate quantum protocols that can address questions ranging from fundamental to practical. Examples include first observation of area law vs. volume law entanglement in ground and excited states of many-body systems, and quantum simulators acting as programable quantum sensors implementing near “optimal” entanglement-enhanced quantum metrology.

A conformal field theory is a physical theory which is invariant under changes in its length or energy scale. It describes the physics of boiling of water. In this talk, the referent will present how conformal field theory is used as a powerful tool to study quantum gravity. She will discuss how conformal field theories describe quantum properties of a family of black holes, just as quantum mechanics describes the Hydrogen atom.

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SND@LHC is a compact and stand-alone experiment to perform measurements with neutrinos produced at the LHC in a hitherto unexplored pseudo-rapidity region of 7.2 < 𝜂 < 8.4, complementary to all the other experiments at the LHC. The experiment is located 480 m downstream of IP1 in the unused TI18 tunnel. The detector is composed of a hybrid system based on an 800 kg target mass of tungsten plates, interleaved with emulsion and electronic trackers, followed downstream by a calorimeter and a muon system. The configuration allows efficiently distinguishing between all three neutrino flavours, opening a unique opportunity to probe physics of heavy flavour production at the LHC in the region that is not accessible to ATLAS, CMS and LHCb. This region is of particular interest also for future circular colliders and for predictions of very high-energy atmospheric neutrinos. The detector concept is also well suited to searching for Feebly Interacting Particles via signatures of scattering in the detector target. The first phase aims at operating the detector throughout LHC Run 3 to collect a total of 250 fb−1. The experiment has been taking data successfully during the proton physics run of 2022. We show the detector concept, design and performance as well as the first physics results.

The groundbreaking discovery of the neutron star merger event GW170817 ushered in a new era of multimessenger astrophysics. One key observation was the optical signal that accompanied GW170817, which provided the first firm proof that neutron star mergers produce heavy elements. Still, it is not known exactly which elements are produced by mergers and in what proportions. Are neutron star mergers the sole astrophysical source of the heaviest elements or do other extreme events contribute? A full understanding of neutron star mergers and their role in galactic chemical evolution requires progress in a number of areas including nuclear physics. Thousands of exotic nuclear species participate in neutron star merger nucleosynthesis, and their properties shape abundance patterns and kilonova signals. Here we discuss how nuclear physics uncertainties influence predictions of nucleosynthesis observables. We then explore the promise of experimental campaigns at rare isotope beam facilities to both reduce these uncertainties and provide insight into astrophysical environments of heavy element production.

Indirect high-precision searches for possible deviations from Standard Model predictions at low energies are an important tool for finding signatures of new physics. Ab-initio theoretical predictions involving the strong nuclear force at small energies are only possible using Monte Carlo methods in a numerical approach known as Lattice QCD. In recent years lattice calculations of several quantities, such as the pion decay constant, have reached a precision of O(1%), where electromagnetic effects can no longer be neglected. In this talk Vera Gülpers will discuss how electromagnetic effects can be included in lattice calculations and present results of our recent calculation of electromagnetic corrections to leptonic pion and kaon decays.

Plasmonics is commonly used to confine electromagnetic waves into subwavelength noble metal structures for photonic applications. As an unwanted side effect, heat is generated locally, which is the foundation of thermoplasmonics. Besides numerous very interdisciplinary applications, such local heat generation provides unique dynamic control over microscopic objects in liquids with non-equilibrium physics. I will give two examples. First, I discuss experiments on active colloidal particles that are self-propelled by thermoplasmonic effects. Such active particles mimic the motility of living species like bacteria but lack the feedback loops that control their behavior. The optical control of plasmonic heating allows us to implement feedback loops, behavior and even learning for active particles. Using this technique, we can show that perception-reaction delays as omnipresent in living systems can be the origin of a variety of dynamical collective states that even display signatures of criticality. In a second example, I will briefly report on experiments using plasmonic heat generation to enable the control of liquids and macromolecules. Dynamic temperature fields thereby help us to study elementary processes of peptide aggregation as relevant for neurodegenerative diseases over extremely long periods of time.

The referent will overview the problem of baryon asymmetry of the Universe and the theoretical framework within which the baryogenesis, i.e. the dynamical generation of a matter–antimatter asymmetry, can occur. He will discuss different mechanisms for baryogenesis with special emphasis to those of them that can be experimentally tested.

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Controlled manipulation of a system allows for systematic investigation of the underlying interactions and phenomena. Simultaneously, tunability also enables the development of novel materials systems and devices customized for specific applications. Here, we will focus on materials systems that conventionally have not been used as active components in spintronic devices. We will explore the impact of strain on the antiferromagnetic domain structure via magneto-elastic coupling1. Furthermore, we will delve into hybrid molecule-magnetic interfaces. Molecules offer a unique way of controlling and varying the structure at the interface making it possible to precisely tune the spin injection and diffusion by molecular design2. In particular, chirality has gained recent interest in the context of the chiral-induced spin selectivity effect3. Here, we will explore signatures of spin filtering at a non-magnetic chiral molecule-metal interface paving the path toward novel hybrid spintronics.

Forty years ago as an undergraduate contemplating graduate school in high energy physics, the referent declined a research assistantship to work on a neutrino experiment because neutrinos weren’t interesting … they were massless and weakly interacting so produced frustratingly few events to analyze even in massive detectors. How things have changed! The more we learn, the more we realize the importance of the most abundant known matter particle in the universe. In the decades since my naïve snubbing of this intriguing particle we have developed a well-established three-flavor paradigm that may help explain the matter-antimatter asymmetry of the universe. Yet beyond that, a few intriguing measurement “anomalies” hint at the existence of something stranger still, a neutrino that does not interact via any known forces except gravity, a sterile neutrino. Robert Wilson will give a brief overview of the results that motivated a definitive search for sterile neutrinos with a mass in the 1 eV/c2 range – the Short-Baseline Neutrino program at Fermi National Accelerator Laboratory. He will describe the physics sensitivity and the detectors that will measure the appearance of electron-type neutrinos in a muon-type neutrino beam using massive liquid argon time-projection chambers with an emphasis on the 760-ton far detector developed by the ICARUS collaboration. Operating both in Italy’s Gran Sasso underground laboratory and now at Fermilab, this detector demonstrated the viability of the technology for large-scale experiments such as the international Deep Underground Neutrino Experiment (DUNE).

The presentation covers the aspects of the use the accelerators for the hadron therapy. It includes the summary of the advantages of hadron use for radiation treatment of cancer, the technological solutions used for the beam acceleration, dose delivery and application, and an overview over the types of commercially available systems. Following that, the presentation concludes by describing the newly established the PARticle Therapy REsearch Center (PARTREC) in Groningen. Using the superconducting cyclotron AGOR and being embedded within the University Medical Center Groningen, providing proton beams of up to 190 MeV and ion beams (up to Pb) with energies up to 90 MeV/nucleon for pre-clinical research in medical physics and radiobiology.

Magnetic fields of planets, stars and galaxies are generated by the homogeneous dynamo effect, or self-excitation, in moving electrically conducting fluids, such as liquid metals or plasmas. Once generated, magnetic fields can promote cosmic structure formation by destabilizing, via the magnetorotational instability (MRI), rotational flows that would be otherwise hydrodynamically stable. Closely related instabilities, such as the current-driven Tayler instability might be at work in the solar tachocline. For a long time, these topics had been the subject of purely theoretical and numerical research. This situation changed in 1999 when the threshold of magnetic-field self-excitation was exceeded in the two liquid sodium experiments in Riga and Karlsruhe. Since 2006, the VKS dynamo experiment in Cadarache has successfully reproduced many features of geophysical interest such as reversals and excursions. MRI related experiments were partly successful with the observation of the helical MRI and the azimuthal MRI at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), where first evidence of the current-driven Tayler instability in a liquid metal was obtained, too. In another liquid metal experiment at the Dresden High Magnetic Field laboratory (HLD) the “magic point” of coinciding Alfvén and sound speeds was reached, which is thought to play a key role for the heating of the solar corona. The lecture gives an overview about previous and future liquid metal experiments on dynamo action and magnetically triggered flow instabilities, with special focus on the precession driven liquid sodium experiment and the large-scale MRI experiment that are under construction in the framework of the DRESDYN project at HZDR. Particular emphasis is placed on generic questions such as the reversal mechanism of the geodynamo and the possibility of a planetary synchronization of the solar dynamo, on which those experiments might shed some fresh light.

Small satellites are nowadays extremely powerful, flexible and sustainable platforms that can be used to complement the missions usually assigned to larger spacecrafts. Modularity, standardization, intensive use of state-of-the art COTS technologies consent to prepare cheaper missions in shorter timeframes, thus allowing a more frequent access to space environment, including Cislunar and Interplanetary. The Italian Space Agency – ASI promotes, funds and coordinates the national initiatives also in this promising sector, both for national missions and within international cooperation. The first products of this effort are ArgoMoon and LICIACube, both 6U cubesats which operated during 2022 as first Italian spacecrafts beyond the Low Earth Orbit. The Light Italian Cubesat for Imaging of Asteroids - LICIACube participated in the NASA Double Asteroid Redirection Test - DART mission, the first active Planetary Defense mission; on September 26th 2022, few minutes after DART’s impact on asteroid Dimorphos, LICIACube captured unique images of the impact effects, primarily the plume of ejecta, and the not visible side of the secondary asteroid. The operations have been conducted by a national team coordinated by ASI. The design, manufacturing, testing and operations of the space and ground segment elements have been performed by the Italian firm Argotec under ASI management, while a wide scientific team supported the investigation preparation with impact modelling simulation and data analysis and interpretation, under the coordination of the National Institute of Astrophysics INAF. The engineering teams of Polytechnic of Milan and University of Bologna were in charge of trajectory design and optimization and the orbit determination and navigation, respectively. Captured images during the challenging fly-by confirmed the DART success as Planetary Defense initiative and provided scientists with highly valuable data, that allowed a first set of results to be confirmed and are currently under further analysis for scientific investigations. In fact, on October 11th 2022, NASA announced the complete success of the DART mission, confirming that the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes. Moreover, The LICIACube images show that the DART impact on Dimorphos generated a cone of ejected surface material with a large aperture angle. This plume has a complex and inhomogeneous structure, characterized by non-radial filaments, dust grains, and single and clustered boulders that allows us to deeply investigate the nature of the ejecta and the structure of Dimorphos.

Quantum electrodynamics (QED) is part of the standard model and the best understood quantum field theory. Many tests exist, from free particles (electron and muon anomalous magnetic moment) to bound states. From the historical measurement of the Lamb-shift which lead to the advent of QED and field theories, many systems have been studied and compared to the most advanced calculations. One can cite hydrogen, positronium, muonium, highly charged, few electron ions[1] and exotic atoms (atoms in which the electron is replaced by a heavier particle like a muon, a pion or an antiproton). In this talk I will present a few cases of highly charged ions high-precision results (few ppm accuracy) obtained with our Double Crystal Spectrometer in Paris[2-4] for medium-Z elements, and preliminary results obtained at GSI on few-electron uranium. I will then present new ideas [5] and first demonstration results on QED tests using muonic atoms and transition-edge sensor micro-calorimeter at JPARC [6, 7], and their extension to antiprotonic atoms at ELENA in the future. Detailed comparison with QED and relativistic many-body calculations when relevant will be made. [1]Topical Review: QED tests with highly-charged ions, P. Indelicato. J. Phys. B 52, 232001 (2019). [2]High-precision measurements of n=2->n=1 transition energies and level widths in He- and Be-like Argon Ions, J. Machado, C.I. Szabo, J.P. Santos et al. Phys. Rev. A 97, 032517 (2018). [3]Reference-free measurements of the 1s 2s 2p 2P1/2,3/2 → 1s2 2s 2S1/2 and 1s 2s 2p 4P5/2 → 1s2 2s 2S1/2 transition energies and widths in lithiumlike sulfur and argon ions, J. Machado, G. Bian, N. Paul et al. Phys. Rev. A 101, 062505 (2020). [4]Absolute measurement of the relativistic magnetic dipole transition in He-like sulfur, J. Machado, N. Paul, G. Soum-Sidikov et al. Phys. Rev. A in press, (2023). [5]Testing Quantum Electrodynamics with Exotic Atoms, N. Paul, G. Bian, T. Azuma et al. Phys. Rev. Lett. 126, 173001 (2021). [6]Deexcitation Dynamics of Muonic Atoms Revealed by High-Precision Spectroscopy of Electronic K X Rays, T. Okumura, T. Azuma, D.A. Bennett et al. Phys. Rev. Lett. 127, 053001 (2021). [7]Proof-of-Principle Experiment for Testing Strong-Field Quantum Electrodynamics with Exotic Atoms: High Precision X-ray Spectroscopy of Muonic Neon, T. Okumura, T. Azuma, D.A. Bennett et al. Phys. Rev. Lett. in press, (2023).

Magnetic field sensors have a mature and transversal level of implementation in the market, from automotive to biomedical domains. The impressive technological progress in thin film preparation and characterization, combined with nano-microfabrication tools offer presently large spectra for device design. The materials discussed include several varieties of thin film materials combined onto multilayer stacks. In addition, the noise mechanisms (the “killing factor” that limits the MR sensor performance) will be discussed, and I will show successful strategies for improving the signal-to-noise ratio, improving the ultimate field detectable by an MR sensor. Examples where spintronic sensors are useful tools for precision sensing will be provided, including integration with microfluidics, optical and MEMS micromachined actuators. During my talk, I will show how challenging applications have identified creative solutions, requiring joint skills in transversal areas as physics, materials, electronics and mechanical engineering.