Particle and Nuclear Physics

Experimental particle and nuclear physics research has expanded significantly in recent years at our department.

In the CMS experiment at the Large Hadron Collider (LHC) of the European Organization for Nuclear Research (CERN) near Geneva, we search for signs of the fundamental theory behind the Standard Model of particle physics, focusing primarily on the precise measurements of the production of two electroweak vector bosons and the direct search for supersymmetric particles in the record energy proton-proton collisions. In addition, we study the properties of the strong interaction under extreme conditions, including LHC lead ion collisions. Our goal is to characterize the quark-gluon plasma, the hot and dense quark matter that filled up the Universe a few millionths of a second after its birth. Our researchers participate in the development and operation of the trigger system for real-time event selection and the Zero Degree Calorimeter (ZDC) used for centrality measurement in heavy ion collisions. We have a leading role in high-precision luminosity measurements and in the Beam Radiation, Instrumentation and Luminosity (BRIL) detector system both for the operation the optimal exploitation of its data and for the upgrade of the system for the High Luminosity LHC (HL-LHC) phase starting in 2029. More details about the work of the MTA-ELTE Lendület CMS Particle and Nuclear Physics Research Group, which was established in our department in 2015, can be read here.

Our colleagues participate in the STAR and PHENIX experiments at the Relativistic Heavy Ion Collider (RHIC) of the Brookhaven National Laboratory, and they coordinate the Hungarian efforts in these collaborations. Our research focuses on the properties of the Quark-Gluon Plasma created in high energy heavy ion collisions, with results ranging from experiment to phenomenology. Our tools include quantum-statistical correlations, femtoscopy and the azimuthal anisotropies of the particle distributions, created by the flow profile of the Quark-Gluon Plasma. We also investigate the the phenomenology of this matter, in particular we achieved important results in modeling it with exact solutions of relativistic hydrodynamics. More information about the work and results of the team working on RHIC physics and experiments is available at here and here.

Our neutrino physics research group investigates hadron production in the heavy ion and neutrino experiment NA61 / SHINE at CERN's SPS particle collider. The NA61/SHINE results are used to predict the beam flux for the T2K experiment in Japan. In parallel, we conduct studies for the design optimisation of the next-generation experiment, the Deep Underground Neutrino Experiment (DUNE) in the United States, for which we work on the development of the near detector for more accurate measurement of the neutrino interaction cross section.

Our research at CERN's LHCb experiment focuses on the investigation of new phenomena beyond the standard model of particle physics. We search for heavy new particles that contribute to quantum mechanical loop processes involving the heavy b-quark. Lighter but weakly interacting new particles that travel long distances before decaying into standard model particles will be searched for with the LHCb's dedicated subdetector, CODEX-b, in the design and construction of which our group takes a leading role. We also study new exotic states of matter, pentaquarks and tetraquarks with LHCb, and we participate in the research and development of an improved electromagnetic calorimeter for the HL-LHC post-2030 operational phase.

We study the structure and reactions of light, neutron-rich nuclei far from stability at accelerators producing radioactive nuclear beams (MoNA@NSCL, NeuLand@GSI, Nebula@Riken), and we also participate in the development of related detectors. We investigate the neutron halo phenomenon on nuclei with low atomic numbers and the possibility of measuring neutron capture processes important in astrophysical reactions using inverse methods. More information can be found here.

Theoretical investigations of quantum many body systems are not only important from the point of view of particle physics, but also that of statistical and condensed matter applications. Physical systems showing strong correlations between its constituents can typically described by strongly interacting quantum field theories. Such models cannot be solved by using conventional mathematical approaches, however, functional methods based on Feynman's path integral formulation are promising candidates. In our research we focus on such techniques applied to strongly coupled systems. Our main line of investigations is the theoretical description of the strongly interacting quark matter, its phase structure, and the related phase transitions. On top of that, we also carry out research related to quantum statistical mechanical systems, such as superconductors, topological phase transitions, active matter.

Astrophysics

We are mainly interested in Extragalactic Astrophysics. Astronomy has advanced as the technology of observation (telescopes) advanced. 400 years ago, bodies in the Solar System were the focus of interest, but since the beginning of the 20th century, extragalactic objects could be studied and there are many questions to be answered, and there are many new frontiers in Extragalactic Astronomy.

Sky surveys and galaxy catalogs: We developed the first digital galaxy catalog back in the 1990's. There were only 113 galaxies in the catalog, data came from Palomar and Lowell Observatories (“A Catalog of Digital Images of 113 Nearby Galaxies”, 1996, AJ, 111, 174). To aid this work, we have developed a method to convert photometric information among different photometric systems (“Generating Colors and k-corrections from Existing Catalog Data”, 1994, AJ, 108, 1476). We have also developed an automatic morphological classification system to analyze images of large galaxies. We have been official members of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS I) project. Pan-STARRS extended survey operations to the southern sky, and we have discovered a huge void in the survey data (“Detection of a supervoid aligned with the cold spot of the cosmic microwave background”, 2015, MNRAS, 450, 288). In 2012 we joined the LSST as a foreign members. Within the Rubin Observatory “Legacy Survey of Space and Time” (Rubin-LSST) we are mostly interested in the “Galaxies” Science Collaboration. Since we are building a large galaxy catalog for LIGO to aid the localization of gravitational wave sources – see below – Rubin-LSST membership will help us to further develop this galaxy catalog.

LIGO: We have joined the LIGO Scientific Collaboration (LSC) in 2017. We have developed an infrasound microphone to be part of the physical environmental monitoring system. Six units were installed (corner station and end stations at both sites, in Livingston and Hanford). We have also installed five of these microphones at the DUGL in South Dakota to study the infrasound background in those long underground tunnels that will play key roles in future Earth-based gravitational-wave observatories like the Einstein Telescope and the Cosmic Explorer. For LIGO we have developed several algorithms to search for unknown types of signals (as part of the “Burst” group). An important aspect of multi-messenger astronomy we lead within the LSC is to localize gravitational wave (GW) sources in the sky to aid follow-up EM observations. For this purpose, we have developed a galaxy catalog that covers the region of the sky LIGO is sensitive to (we have improved the previous LIGO galaxy catalog that had 50,000 galaxies to about 3 million galaxies by now). This catalog is called the Galaxy List for the Advanced Detector Era, GLADE (GLADE+: an Extended Galaxy Catalogue for Multimessenger Searches with Advanced Gravitational-wave Detectors, 2022, MNRAS, 514, 1403). 

CubeSats: The next step in the endeavor is to develop and build a fleet of CubeSats with gamma-ray detectors. Merging binary neutron stars produce EM signals that could be observed by LIGO EM partners, and these include gamma rays. A simple Cesium Iodide scintillator serves as our gamma-ray detector. We calculated that 9 of these 3U CubeSats, distributed evenly on low Earth orbits (LEOs) could pinpoint the location of GW sources with high accuracy. We have built and launched two 1U prototypes, they work perfectly, and detected gamma-ray bursts, these detections prove to be the first “real” science return from a CubeSat (GRBAlpha: the Smallest Astrophysical Space Observatory - Part 1: Detector Design, System Description and Satellite Operations, arXiv:2302.10048). 

LISA: We are interested in what LISA could do in the future in terms of measuring merger rates of galaxies in the early Universe. We have published several papers about the possibility of localizing LISA GW sources and observing these locations in various EM bands (Finding the Electromagnetic Counterparts of Cosmological Standard Sirens, 2006, ApJ, 63, 27), even predicting mergers a week before it happens in case of a strong signal (Premerger localization of gravitational-wave standard sirens with LISA: Harmonic mode decomposition, 2007, PRD, 76, 2003) and came up with a possible process that could actually produce EM observable signals from these supermassive black hole mergers (Prompt Shocks in the Gas Disk around a Recoiling Supermassive Black Hole Binary,  2008, ApJL, 676, 5L). 

The first research group in Astrophysics at the department was formed in 2007 to participate in LIGO. The Hungarian Academy of Sciences supported the “Momentum” research group in Extragalactic Astrophysics in 2012, that was used to extend our participation in Pan-SATARRS and LSST. Upon the completion of the “Momentum” program, in 2017, the Hungarian Academy of Sciences decided to make this group permanent at Eötvös (now the ELKH-ELTE Research Group in Extragalactic Astrophysics). We have received support through the so-called “Institutional Excellence Program in Particle- and Astrophysics” in 2018. Our current contract with the Hungarian funding agency (NKFIH) is till the end of 2025. Within this program, we oversee the work of about 50 colleagues, hired more than 10 foreign postdocs, and 2 assistant professors, also from abroad (Japan and India), and joined new international collaborations to boost our output (these are mainly particle physics experiments like the NA61/SPS Heavy Ion and Neutrino Experiment, and the LHCb experiment at CERN).