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J-PET DETECTOR APPROACH FOR TESTING CP SYMMETRY IN THE ORTHO-POSITRONIUM ANNIHILATION

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Acta Physica Polonica B, Proceedings Supplement

Acta Physica Polonica B, Proceedings Supplement 2024年第1期17卷 1A11-1A111页

作者： Eliyan, Kavya V. Skurzok, Magdalena Moskal, Pawel Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Center for Theranostics Jagiellonian University Lojasiewicza 11 Kraków30-348 Poland

Positronium is a suitable leptonic system to test Charge-Parity (CP) discrete symmetry involving the correlations of photons momenta originating from ortho-positronium (o-Ps) annihilation. The photon–photon interaction in the final state due to the vacuum polarization may mimic CP symmetry violation of the order of 10−9, while weak interaction effects lead to a violation of the order of 10−14 according to the Standard Model prediction. So far, the experimental limits on CP symmetry violation in the o-Ps decay are set at the level of 10−4. One of the unique features of the J-PET detector is its ability to measure the polarization direction of the annihilation photons without the magnetic field. The J-PET detector can be used to explore discrete symmetry by looking for probable non-zero expectation values of the symmetry-odd operators, constructed from spin of ortho-Positronium and momentum, and polarization vectors of gamma (γ) quanta resulting from o-Ps annihilation. In this work, the J-PET detector experimental and analysis method to improve the sensitivity level at least by one order for CP discrete symmetry studies in the o-Ps decay via symmetry odd operator (ϵ⃗i·k⃗j), where ϵ⃗i and k⃗j are reconstructed polarization and momentum vectors of photons from the o-Ps decays, respectively, will be presented. © 2024 Jagiellonian University. All rights reserved.

关键词： Photons

Multiplicity fluctuations and rapidity correlations in ultracentral proton-nucleus collisions

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arXiv 2024年

作者： Samanta, Rupam Ollitrault, Jean-Yves AGH University of Science and Technology Faculty of Physics and Applied Computer Science aleja Mickiewicza 30 Cracow30-059 Poland Université Paris Saclay CNRS CEA Institut de physique théorique Gif-sur-Yvette91191 France

A collision between a proton and a heavy nucleus at ultrarelativistic energy creates particles whose rapidity distribution is asymmetric, with more particles emitted in the direction of the nucleus than in the direction of the proton. This asymmetry becomes more pronounced as the centrality estimator, defined from the energy deposited in a calorimeter, increases. We argue that for high-multiplicity collisions, the variation of the impact parameter plays a negligible role, and that the fluctuations of the multiplicity and of the centrality estimator are dominated by quantum fluctuations, whose probability distribution can be well approximated by a correlated gamma distribution. We show that this simple model reproduces existing data, and we make quantitative predictions for collisions in the 0−0.1% and 0−0.01% centrality windows. We argue that by repeating the same analysis with a different centrality estimator, one can obtain direct information about the rapidity decorrelation in particle production. Copyright © 2024, The Authors. All rights reserved.

关键词： Hadrons

Wigner molecules in phosphorene quantum dots

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arXiv 2022年

作者： Thakur, Tanmay Szafran, Bartlomiej AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 Kraków30-059 Poland

We study Wigner crystallization of electron systems in phosphorene quantum dots with confinement of an electrostatic origin with both circular and elongated geometry. The large effective masses in phosphorene promote the separation of the electron charges already for quantum dots of relatively small size. The anisotropy of the effective mass allows for the formation of Wigner molecules in the laboratory frame with a confined charge density that has lower symmetry than the confinement potential. We find that in circular quantum dots separate single-electron islands are formed for two and four confined electrons but not for three trapped carriers. The spectral signatures of the Wigner crystallization to be resolved by transport spectroscopy are discussed. Systems with Wigner molecule states are characterized by a nearly degenerate ground state at B = 0 and are easily spin-polarized by the external magnetic field. In electron systems for which the single-electron islands are not formed, a more even distribution of excited states at B = 0 is observed, and the confined system undergoes ground state symmetry transitions at magnetic fields of the order of 1 Tesla. The system of five electrons in a circular quantum dot is indicated as a special case with two charge configurations that appear in the ground-state as the magnetic field is changed: one with the single electron islands formed in the laboratory frame and the other where only the pair-correlation function in the inner coordinates of the system has a molecular form as for three electrons. The formation of Wigner molecules of quasi-1D form is easier for orientation of elongated quantum dots along the zigzag direction with heavier electron mass. The smaller electron effective mass along the armchair direction allows for freezing out the transverse degree of freedom in the electron motion. Calculations are performed with a version of the configuration interaction approach that uses a single-electron basis that is pre-

关键词： Ground state

Thermal properties of structurally balanced systems on classical random graphs

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arXiv 2022年

作者： Malarz, Krzysztof Woloszyn, Maciej AGH University Faculty of Physics and Applied Computer Science al. Mickiewicza 30 Kraków30-059 Poland

The dynamics of social relations and the possibility of reaching the state of structural balance (Heider balance) under the influence of the temperature modeling the social noise level are discussed for interacting actors occupying nodes of classical random graphs. Depending on the graph density D, either a smooth cross-over or a first-order phase transition from a balanced to an imbalanced state of the system is observed with an increase in the thermal noise level. The minimal graph density Dmin for which the first-order phase transition can be observed decreases with the system size N as Dmin ∝ N−0.58(1). For graph densities D > Dmin the reduced critical temperature Tc✶ = Tc/Tc(D = 1) increases with the graph density as Tc✶ ∝ D1.719(6) independently of the system size N. © 2022, CC BY.

关键词： Graph theory

Random site percolation on honeycomb lattices with complex neighborhoods

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arXiv 2022年

作者： Malarz, Krzysztof AGH University Faculty of Physics and Applied Computer Science al. Mickiewicza 30 Kraków30-059 Poland

We present a rough estimation—up to four significant digits, based on the scaling hypothesis and the probability of belonging to the largest cluster vs. the occupation probability—of the critical occupation probabilities for the random site percolation problem on a honeycomb lattice with complex neighborhoods containing sites up to the fifth coordination zone. There are 31 such neighborhoods with their radius ranging from one to three and containing from three to 24 sites. For two-dimensional regular lattices with compact extended-range neighborhoods, in the limit of the large number z of sites in the neighborhoods, the site percolation thresholds pc follow the dependency pc ∝ 1/z, as recently shown by Xun, Hao and Ziff [Physical Review E 105, 024105 (2022)]. On the contrary, noncompact neighborhoods (with holes) destroy this dependence due to the degeneracy of the percolation threshold (several values of pc corresponding to the same number z of sites in the neighborhoods). An example of a single-value index ζ = Pi ziri—where zi and ri are the number of sites and radius of the i-th coordination zone, respectively —-characterizing the neighborhood and allowing avoiding the above-mentioned degeneracy is presented. The percolation threshold obtained follows the inverse square root dependence pc ∝ 1/√ζ. The functions boundaries() (written in C) for basic neighborhoods (for the unique coordination zone) for the Newman and Ziff algorithm [Physical Review E 64, 016706 (2001)] are also presented. © 2022, CC BY-NC-SA.

关键词： Coordination reactions

Gravitational Wave Resonance in Ultra-Light Dark Matter Halos

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arXiv 2023年

作者： Delgado, Paola C.M. Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

Ultra-Light Dark Matter (ULDM) halos constituted by Ultra-Light Axions (ULAs) generate gravitational potentials that oscillate in time. In this paper I show these potentials interact with gravitational waves, resonantly amplifying them. For all ULA masses considered, the resonance in the solar region is currently negligible, while in a denser dark matter environment, which may arise in different scenarios, it might become significant. The frequency of the amplified gravitational wave is equal to the ULA mass in the case of first resonance band, which represents the most efficient scenario. Copyright © 2023, The Authors. All rights reserved.

关键词： Gravity waves

Introdução à Cosmologia Quântica

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arXiv 2023年

作者： Delgado, Paola C.M. Faculty of Physics Astronomy and Applied Computer Science Jagiellonian University Krakow30-348 Poland

This review presents an introduction to Quantum Cosmology, including the mathematical methods essential to the canonical approach, some of the existing conceptual problems and the connection of the models to possible ... 详细信息

关键词： Quantum theory

Scaled tight-binding model for a two-dimensional electron gas at the (001) LaAlO3/SrTiO3 interface

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Physical Review applied 2025年第5期23卷 054051-054051页

作者： Paweł Wójcik Roberta Citro Bartłomiej Szafran Faculty of Physics and Applied Computer Science AGH University of Krakow Al. Mickiewicza 30 Kraków 30-059 Poland Physics Department “E. R. Caianiello” and CNR-SPIN Universitá degli Studi di Salerno INFN Gruppo Collegato di Salerno 84084-Fisciano (Sa) Italy

Progress in the fabrication of nanoscale systems based on the two-dimensional electron gas (2DEG) at the interface between LaAlO3 and SrTiO3 (LAO/STO) has created increased demand for simulations of these nanostructures, which typically range in size from tens to hundreds of nanometers. Due to the low lattice constant of LAO/STO, approximately 0.39 nm, these calculations become extremely time-consuming. Here, we present a scaling procedure for the tight-binding approximation of the LAO/STO 2DEG, defined on a square lattice that can be several times larger than in the conventional approach. The scaled model is analyzed within the context of quantum transport simulations and electronic structure calculations. Our findings demonstrate that the scaled model closely aligns with the ordinary one up to a scaling factor of 8. The applicability of the scaled Hamiltonian for systems with interacting electrons is also discussed. These results pave the way for more efficient simulations of LAO/STO nanostructures with realistic sizes relevant to experimental applications.

关键词： Lattice constants

Vanishing opinions in Latané model of opinion formation

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arXiv 2022年

作者： Dworak, Maciej Malarz, Krzysztof AGH University of Science and Technology Faculty of Physics and Applied Computer Science al. Mickiewicza 30 Kraków30-059 Poland

In this paper, the results of computer simulations based on Nowak–Szamrej–Latané model with multiple (from two to five) opinions available in the system are presented. We introduce the noise discrimination level (which says how small the clusters of agents could be considered as negligible) as a quite useful quantity that allows qualitative characterization of the system. We show that depending on the introduced noise discrimination level, the range of actors’ interactions (controlled indirectly by an exponent in distance scaling function, the larger the exponent the more influential the nearest neighbors are) and the information noise level (modeled as social temperature, which increases results in increase of randomness in taking the opinion by the agents), the ultimate number of the opinions (measured as the number of clusters of actors sharing the same opinion in clusters greater than the noise discrimination level) may be smaller than the number of opinions available in the system. These are observed in small and large information noise limits but result in either unanimity, or polarization, or randomization of opinions. © 2022, CC BY.

关键词： Random processes