Physics of Particles and Nuclei Letters最新文献

The samples employed in the investigation were semi-insulating GaAs wafers. Noble gas has been implanted using the UNIMAS ion implanter at energy 100 keV, fluence of 3 × 10¹⁵ ions/cm². Rutherford backscattering spectroscopy with nuclear reaction analysis (RBS/NR) method was used to determine the thickness and atomic composition of elements in the samples. The nuclear reaction ¹⁶O(α,α)¹⁶O exhibits elastic resonance at around energy 3.05 MeV. This resonance provides a useful method for expanding RBS techniques to investigate the concentration of oxygen present on sample surfaces. The RBS/NR approach’s conclusion indicates that the surface of GaAs samples contains an oxygen-enriched layer. It has also been shown that the thickness of native oxide layer influence by the type of ion.

The paper reports on search for heavy neutrinos ((N)) decays with masses ({{m}_{N}} < 493{kern 1pt} ,{text{MeV/}}{{c}^{2}}). Heavy neutrinos can be produced in decays: ({{K}^{ pm }},{{pi }^{ pm }} to {{l}^{ pm }}N), where ((l = e,mu )). Considered heavy neutrino decay modes are the following: (N to l_{alpha }^{ pm }{{pi }^{ mp }},) (N to l_{alpha }^{ + }l_{beta }^{ - }nu (bar {nu })), where ((alpha ,beta = e,mu )). Search for signal events is performed in Time Projection Chambers (TPCs) of ND280 detector of T2K experiment. Inclusion of more statistics, a new tracking method in TPCs and an updated Monte Carlo model aid in an increase of the sensitivity of the earlier analysis of 2019 and additionally helps to extend the studies into the lower mass region. Preliminary signal selection efficiencies, statistical and systematic uncertainties, expected number of background events and expected experiment sensitivity are presented.

The Straw Tracker of the SPD detector should provide track coordinate measurements and also should serve the Particle Identification of low momentum charged particles. This requires simultaneous precise measurement of the signal time and charge, so optimization of the readout electronics parameters is necessary. Different parameters, such as the preamplifier gain, shaper peaking time, discriminator threshold and electronics noise level are studies. Time and charge distributions are obtained. The drift time distributions for various discriminator threshold levels and shaper peaking times are analyzed in order to reach the best tracking performance. Influence of the peaking time on the precision of charge measurements is studied as well. Comparison between the experimental data and modeling results is presented.

We construct the coordinate-space wave function of a fermion–antifermion pair produced in two-body decays of a spin-zero parent. Starting from the S-matrix amplitude we derive a momentum-space wave function and its Fourier transform. For a scalar (({{0}^{ + }})) coupling we obtain a pure (L = 1) partial wave whose spin factors select definite orbital projections m for specific spin orientations of f and (bar {f}). For a pseudoscalar (({{0}^{ - }})) coupling the result is a pure (L = 0) wave with the usual singlet spin structure. We show explicitly why the back-to-back momenta of the final particles do not contradict nonzero orbital angular momentum: (L) is a property of the relative coordinate. We also discuss why OAM phases are generally invisible in standard HEP measurements that project onto momentum eigenstates, and point to spin-resolved angular correlations as the observable remnants.

Pentaquark states with hidden charm were discovered by the LHCb collaboration as a result of the analysis of (Lambda _{b}^{0} to J{kern 1pt} /{kern 1pt} psi p{{K}^{ - }}) decays in (pp) collision data with a center-of-mass energy of (sqrt s = 7,8) TeV. The study of the spectrum of these states was subsequently conducted both by the LHCb experiment using (pp) collision data with (sqrt s = 13) TeV and by the ATLAS experiment using (pp) collision data with (sqrt s = 7,8) TeV. Current and future studies of (Lambda _{b}^{0} to J{kern 1pt} /{kern 1pt} psi p{{K}^{ - }}) decays are aimed at further investigation of the properties of the narrow resonances ({{P}_{{cbar {c}}}}{{(4312)}^{ + }}), ({{P}_{{cbar {c}}}}{{(4440)}^{ + }}), ({{P}_{{cbar {c}}}}{{(4457)}^{ + }}). At the same time, the existence of the broad resonance ({{P}_{{cbar {c}}}}{{(4380)}^{ + }}) remains in question, as does the potential contribution to (Lambda _{b}^{0} to J{kern 1pt} /{kern 1pt} psi p{{K}^{ - }}) decays from the strange tetraquark states ({{T}_{{cbar {c}bar {s}1}}})(4000) and ({{T}_{{cbar {c}bar {s}1}}})(4220). This paper presents a review of modern experimental results, the general methodology for analyzing (Lambda _{b}^{0} to J{kern 1pt} /{kern 1pt} psi p{{K}^{ - }}) decays at the ATLAS setup, and discusses the prospects for further experimental studies of pentaquark states in (pp) collision data with a center-of-mass energy of (sqrt s = 13) TeV.

The leading systematic uncertainties of the T2K’s oscillation analysis stem from the modeling of neutrino-nucleus interactions and are largely constrained by the measurements with the near detector ND280. The recent completion of the ND280 upgrade in 2024 has significantly enhanced its tracking capabilities. This paper presents a novel event selection targeting muon neutrino charged-current interactions with single positively charged pion production in the new detector modules of ND280. The selection was designed to maximize the acceptance of the kinematic phase space, providing superior constraints for neutrino interaction models. This work is a critical step towards reducing the dominant systematic uncertainties for the next generation of high-precision oscillation measurements in T2K.

The SPD online filter is a crucial intermediate system that bridges the continuous data stream from the DAQ and the offline computing system. SPD Online Filter is designed for the initial high-throughput, multi-step primary processing of data from the SPD detector. It’s composed of several components: a dedicated compute cluster; applied software, and the middleware which is an intermediate software layer that connects both hardware resources and applied software. The middleware integrates three core components: data and storage management (DSM), workflow management system (WfMS), and workload management system (WMS). We describe the design principles, component interactions, that enable flexible workflow definition, and concurrent execution of multiple workflows.

The described R&D activity is based on the use of experience in the development and implementation of high-voltage power supplies for KRION-6T ion source which is a main part of NICA heavy ion injector at LHEP, JINR. The current state of development of a line of high-voltage power supplies is described in the paper, with power supplies including hardware, embedded and application software that is the product of work.

One of the subsystems of the SPD experiment (phase I) is the Beam Counter (BBC), designed as high-granularity scintillation detector with a segmented structure of ~800 channels. To ensure its reliability, a quick tool to check entire optoelectronic path is needed. We present an optical diagnostic method alternative to the use of ionizing radiation sources. The method, which is based on the use of side-glow fiber (SGF), allows for channel-by-channel testing. Results of research on the choice of interface configuration, optimization of light collection using reflective substrates, and testing of a multichannel optical cable prototype are presented. The developed approach is recommended for use in the BBC subsystem.

An analysis is presented concerning the search for the associated production of a Higgs boson with a single top quark (tH), a process highly sensitive to the complex phase of the top-quark Yukawa coupling. The analysis uses the full 140 fb^–1 of ATLAS data at (sqrt s = 13,,{text{TeV}}), targeting (H to bb), (WW), (ZZ), ττ decays. Advanced multivariate analysis techniques were employed to achieve optimal sensitivity and to separate the tiny tH signal from the large background. The measured signal strength is ({{mu }_{{tH}}} = 8.1 pm 2.6,{text{(stat}}{text{.)}} pm 2.0,{text{(syst}}{text{.)}}). The observed (expected) significance of the tH signal over the background-only hypothesis is 2.8(sigma ) (0.4(sigma )). The observed (expected) upper limit on the tH production cross-section is 13.9 (6.1) times the SM prediction at the 95% confidence level. Interpretations for both Standard Model and inverted top-quark Yukawa coupling scenarios also are presented.