ERC FUNDED PROJECTS

The active target and time projection chamber (ACTAR TPC) is a novel gas-filled detection system that will permit new studies into the structure and decays of the most exotic nuclei. The use of a gas volume that acts as a sensitive detection medium and as the reaction target itself (an “active target”) offers considerable advantages over traditional nuclear physics detectors and techniques. In high-energy physics, TPC detectors have found profitable applications but their use in nuclear physics has been limited. With the ACTAR TPC design, individual detection pad sizes of 2 mm are the smallest ever attempted in either discipline but is a requirement for high-efficiency and high-resolution nuclear spectroscopy. The corresponding large number of electronic channels (16000 from a surface of only 25×25 cm) requires new developments in high-density electronics and data-acquisition systems that are not yet available in the nuclear physics domain. New experiments in regions of the nuclear chart that cannot be presently contemplated will become feasible with ACTAR TPC.

1 290 000 €

Start date: 2014-02-01, End date: 2019-01-31

This project enters the experimental investigation of anyonic quantum gases. We will study anyons – conjectured particles with a statistical exchange phase anywhere between 0 and π – in different many-body systems. This progress will be enabled by a unique approach of bringing together artificial gauge fields and quantum gas microscopes for ultracold atoms. Specifically, we will implement the 1D anyon Hubbard model via a lattice shaking protocol that imprints density-dependent Peierls phases. By engineering the statistical exchange phase, we can continuously tune between bosons and fermions and explore a statistically-induced quantum phase transition. We will monitor the continuous fermionization via the build-up of Friedel oscillations. Using state-of-the-art cold atom technology, we will thus open the physics of anyons to experimental research and address open questions related to their fractional exclusion statistics. Secondly, we will create fractional quantum Hall systems in rapidly rotating microtraps. Using the quantum gas microscope, we will i) control the optical potentials at a level which allows approaching the centrifugal limit and ii) use small atom numbers equal to the inserted angular momentum quantum number. The strongly-correlated ground states such as the Laughlin state can be identified via their characteristic density correlations. Of particular interest are the quasihole excitations, whose predicted anyonic exchange statistics have not been directly observed to date. We will probe and test their statistics via the characteristic counting sequence in the excitation spectrum. Furthermore, we will test ideas to transfer anyonic properties of the excitations to a second tracer species. This approach will enable us to both probe the fractional exclusion statistics of the excitations and to create a 2D anyonic quantum gas. In the long run, these techniques open a path to also study non-Abelian anyons with ultracold atoms.

1 497 500 €

Start date: 2019-01-01, End date: 2023-12-31

"In the comprehension of fundamental laws of nature, particle physics is now facing two important questions: 1) What is the nature of the neutrino, is it a standard (Dirac) particle or a Majorana particle? The nature of the neutrino plays a crucial role in the global framework of particle interactions and in cosmology. The only practicable way to answer this question is to search for a nuclear process called ""neutrinoless double beta decay"" (0nuDBD). 2) What is the so called ""dark matter"" made of? Astrophysical observations suggest that the largest part of the mass of the Universe is composed by a form of matter other than atoms and known matter constituents. We still do not know what dark matter is made of because its rate of interaction with ordinary matter is really low, thus making the direct experimental detection extremely difficult. Both 0nuDBD and dark matter interactions are rare processes and can be detected using the same experimental technique. Bolometers are promising devices and their combination with light detectors provides the identification of interacting particles, a powerful tool to reduce the background. 
 The goal of CALDER is to realize a new type of light detectors to improve the upcoming generation of bolometric experiments. The detectors will be designed to feature unprecedented energy resolution and reliability, to ensure an almost complete particle identification. In case of success, CUORE, a 0nuDBD experiment in construction, would gain in sensitivity by up to a factor 6. LUCIFER, a 0nuDBD experiment already implementing the light detection, could be sensitive also to dark matter interactions, thus increasing its research potential. The light detectors will be based on Kinetic Inductance Detectors (KIDs), a new technology that proved its potential in astrophysical applications but that is still new in the field of particle physics and rare event searches."

1 176 758 €

Start date: 2014-03-01, End date: 2019-02-28

In collisions of heavy nuclei at collider energies, for instance at the Large Hadron Collider (LHC) at CERN, the energy density is so high that an equilibrated Quark-Gluon Plasma (QGP), an exotic state of matter consisting of deconfined quarks and gluons, is formed. In proton-proton (p+p) collisions, on the other hand, the density of produced particles is low. The traditional view on such reactions is that final state particles are free and do not rescatter. This picture is challenged by recent LHC data, which found features in p+p collisions that are indicative of collective behaviour and/or the formation of a hot and dense system. These findings have been taken as signs of QGP formation in p+p reactions. Such an interpretation is complicated by the fact that jets, which are the manifestation of very energetic quarks and gluons, are quenched in heavy ion collisions, but appear to be unmodified in p+p reactions. This is puzzling because collectivity and jet quenching are caused by the same processes. So far there is no consensus about the interpretation of these results, which is also due to a lack of suitable tools. It is the objective of this proposal to address the question whether there are collective effects in p+p collisions. To this end two models capable of describing all relevant aspects of p+p and heavy ion collisions will be developed. They will be obtained by extending a successful description of p+p to heavy ion reactions and vice versa. The answer to these questions will either clarify the long-standing problem how collectivity emerges from fundamental interactions, or it will necessitate qualitative changes to our interpretation of collective phenomena in p+p and/or heavy ion collisions. The PI is in a unique position to accomplish this goal, as she has spent her entire career working on different aspects of p+p and heavy ion collisions. The group in Lund is the ideal host, as it is very active in developing alternative interpretations of the data.

1 500 000 €

Start date: 2019-02-01, End date: 2024-01-31