Ion beam physics

Research in the field of physics of ion beam interactions with materials is based on the capabilities of the RBI accelerator complex, the largest experimental research facility in Croatia. Processes that take place on the levels of nuclei (elastic scattering and nuclear reactions), atoms (ionization), molecules (desorption) and crystal lattice (defects) are being investigated, among others, to develop ion beam characterisation techniques with focus on nano-structures and surfaces. Since the ion beam transfers its energy to the stopping medium, it can be also considered as a powerful nano-structuring tool, which is in especially the case for heavy ions. This research is important for novel advanced materials and devices for which the nature of ion beam interactions is not yet known. Materials of particular interest are those related to energy storage and conversion as well as those related to future fusion energy reactors.

Nuclear physics

The Zagreb nuclear physics group has a long tradition in experimental studies of light neutron-rich nuclei, initiated in early 60’s by experiments with neutron generator at RBI. Nowadays, the members of the group are active in several European collaborations engaged at top accelerator facilities where they are leading many international collaborative experiments. The main effort of the group is oriented towards the understanding of exotic phenomena in nuclear structure, as well as in the reaction mechanisms at low energy, where the strong mechanism-structure interplay occurs. The experimental study of key nuclei far from stability line in the neutron-rich region is crucial to advance current understanding of nuclear interaction and its isospin component. These results have an important impact on astrophysical phenomena, since such nuclei participate in different astrophysical scenarios of nucleosynthesis. This line of research is in agreement with the research strategy of NuPECC, the Expert Committee of the European Science Foundation and in particular with the project NuSTAR at FAIR facility currently under construction in Darmstadt, a world leading project for this kind of research.

The RBI Tandem accelerator has been used in last 20 years for many experiments on light nuclei research in collaboration with the European partners. Such measurements are essential in many aspects, primarily in improvement of the facility international reputation and the education of young group members.

Particle physics

IRB participates in the CMS experiment at the Large Hadron Collider (LHC) at CERN. The goal of the CMS experiment is to explore the validity of the Standard Model and to search for manifestations of new physics at the highest energy available in the laboratory today, as the LHC defines the current energy frontier in particle physics among accelerators. The IRB group in CMS has participated actively in the preparation of the CMS physics program and in the measurements based on the data of the first LHC run (2010-2012), with a focus on the study of electroweak interactions and the search for manifestations of new physics in the context of several extensions of the Standard Model. These studies will be continued and extended in the upcoming LHC runs, which will deliver collisions at even higher energies. These measurements will be of special importance for the accurate measurement of the properties of the newly discovered boson at the LHC in 2012. In collaboration with theorists, the group plans to extend its program of searches for manifestations of physics beyond the Standard Model. In continuation of its current activities, the group also intends to contribute further to the operation and future upgrades of the CMS by participating in the daily operation of the CMS pixel detector and by working on the development and commissioning of the next generation of silicon pixel detectors for CMS.

The main goal of the experiments at the intensity frontier is to investigate possible existence of some particles proposed in different theoretical models beyond the Standard Model, especially for the sake of resolving the strong CP problem, dark matter, and unification of particle physics and gravity. In the CAST experiment at CERN and the future IAXO experiment, RBI participates in a search for solar axions and similar axion-like particles (ALPs). Axion is a hypothetical pseudoscalar associated with the absence of CP violation in the strong interactions, and a candidate for the dark matter. Also, RBI participates in the OPERA experiment designed to search for the first direct observation of muon neutrino to tau neutrino oscillations, and in the future NESSIE experiment at CERN proposed to prove or disprove the existence of additional sterile neutrino states. In astroparticle experiments at RBI we are developing new approaches to search for hypothetical bosons (for example, hidden-sector photons and ALPs) which may account for a dark matter component in the Universe. This includes also R&D of photon detectors for ultra-precise measurements to search for quantum effects of new particles in rare processes.

The experimental program of Crystal Ball Collaboration at Mainz (CB@MAMI) is focused on investigating the fundamental problems of physics: the basic properties of the strong interaction, the determination of quark masses, as well as the determination of symmetry violation in certain rare decays (eta i eta' decays). As such, they could significantly contribute to our understanding of these problems, as well as constrain certain aspects of physics beyond the present Standard Model. Very important is work on experimental equipment, primarily on design and testing of the frozen spin polarized target.

Astroparticle physics

A fascinating interconnection between particle physics, cosmology and astrophysical observations forms a basis for the research topic of astroparticle physics. In this regard astrophysical observations allow not only invaluable information to be drawn about the intrinsic properties of the elementary particles (neutrinos, axions, dark matter, cosmic rays, etc.), but using the already known properties of photons and neutrinos to probe the distant universe as well. The fast growth of astroparticle physics has resulted recently in opening a new window for observation of distant astrophysical objects like pulsars, Active Galactic Nuclei and Gamma Ray Bursts - the high-energy gamma astronomy. Much of the Department's activities in astroparticle physics go into observing of high-energy photons from distant astrophysical sites within the collaboration MAGIC, managing the two IACT (Imaging Atmospheric Cherenkov Telescope) gamma-ray telescopes. The rest of the activities is the involvement in the collaboration CTA (Cherenkov Telescope Array), whose main concern at present is to build a new generation infrastructure for the high-energy gamma astronomy based on the IACT technique. An important part of the Department's activities also involves theoretical investigations in the area of high-energy physics and cosmology, with particular regard to noncommutative quantum field theories as well as to the holographic description of the very early and the late-time universe.

Isotope methods

Natural radioactive isotope ¹⁴C has an important application in dating various archaeological, geological and paleontological samples. By using composition of radioactive (¹⁴C and ³H) and stable isotopes (¹³C and ¹⁸O) in environmental samples we can investigate geochemical processes of isotope exchange in nature (atmosphere – water – sediment – biosphere) as well as (paleo) climatic changes and their influence on the environment, such as the sea-level change. Isotopes ³H, ¹⁴C, ²H, ¹⁸O in water are used in hydrogeological studies of drinking water and in monitoring of atmosphere and biosphere. Special attention is paid to the development and improvement of measurement techniques, including the implementation of the accelerator mass spectrometry (AMS) that significantly increases experimental possibilities of various applied studies based on the radiocarbon ¹⁴C.

Development of detectors and related instrumentation

Radiation detectors and associated electronics are basic instrumentation, which is important for almost all research subjects of the Division. Considering that detector testing and development infrastructure has been significantly upgraded through the previous FP6 and FP7 projects (in particular Particle detectors), its impact to basic and applied research within the Division is significantly improved. In order to increase the recognition of research and impact in international collaborations, R&D in the field of development and testing of radiation hard detectors is particularly stimulated. Present activities include development of diamond detectors, fast timing detection systems, detectors based on the emission of light and secondary electrons, as well as applications of radiation in optoelectronics and quantum computing.

Nuclear analytical techniques

Development of nuclear analytical techniques based on excitations by photons, neutrons and ions from accelerator is traditionally within RBI connected to interdisciplinary research subjects and applications. This includes development of techniques for explosive detection using neutrons at RBI site as well as in the environment including underwater. In addition to environmental monitoring, nuclear techniques are also competitive in analysis of cultural heritage objects, biomedical applications as well as in collaboration with industry.

Medical applications

The availability of deoxyglucose labelled with positron emitter ¹⁸F which is produced at RMC cyclotron within the RBI site, and installation of microPET camera in the RBI organizational system, the possibility has been opened for the research of static and dynamic follow-up of isotopically marked bioactive substances. This non-invasive method is of great importance for medical applications done at RBI and in the wider region as well, in particular to study metabolic dysfunctions connected with tumour growth, diabetes, states of oxidative stress, appearance, development and recovery of artificially produced ischemic acute myocardial infarctions and brain insults.