Tens Of MeV Research Articles

Measurement of cross section of proton-induced reactions on oxygen with silicon dioxide target

Oxygen is one of the most common elements in the human body. Proton beams used in therapy induce nuclear reactions that cause a loss of fluence along the beam path. These reactions often lead to production of β+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta ^+$$\\end{document} emitters with relatively short half-lives (less than 20 min). Cross sections for reactions on oxygen are not sufficiently known, particularly at proton energies above few tens of MeV. This contribution presents the results of an experiment, where silicon dioxide targets were used to study nuclear reactions induced by protons with energy below 60 MeV on oxygen. The proton beam was delivered by the AIC-144 cyclotron of the Institute of Nuclear Physics in Kraków. Cross sections of reactions leading to production of 11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ ^{11}$$\\end{document}C, 13\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ ^{13}$$\\end{document}N and 15\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ ^{15}$$\\end{document}O were obtained. They agree well with the measurements using Cherenkov radiation in bulk SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}. The recent measurements performed with a PET scanner provided similar results, except in the case of 16\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ ^{16}$$\\end{document}O(p,x)11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ ^{11}$$\\end{document}C reaction studied in the energy of up to 200 MeV, where our results are 30% lower.

Air stability of monolayer WSi2N4 in dark and bright conditions

Two-dimensional materials with chemical formula MA2Z4 are a promising class of materials for optoelectronic applications. To exploit their potential, their stability with respect to air pollution has to be analyzed under different conditions. In a first-principle study based on density functional theory, we investigate the adsorption of three common environmental gas molecules (O2, H2O, and CO2) on monolayer WSi2N4, an established representative of the MA2Z4 family. The computed adsorption energies, charge transfer, and projected density of states of the polluted monolayer indicate a relatively weak interaction between substrate and molecules resulting in an ultrashort recovery time of the order of nanoseconds. O2 and water introduce localized states in the upper valence region but do not alter the semiconducting nature of WSi2N4 nor its band-gap size apart from a minor variation of a few tens of meV. Exploring the same scenario in the presence of photogenerated electrons and holes, we do not notice any substantial difference except for O2 chemisorption when negative charge carriers are in the system. In this case, monolayer WSi2N4 exhibits signs of irreversible oxidation, testified by an adsorption energy of -5.5 eV leading to an infinitely long recovery time, a rearrangement of the outermost atomic layer bonding with the pollutant, and n-doping of the system. Our results indicate stability of WSi2N4 against H2O and CO2 in both dark and bright conditions, suggesting the potential of this material in nanodevice applications.

Strong decays of the isovector-scalar D*D¯* hadronic molecule

We adopt the effective Lagrangian approach to study the strong decays of the 1−(0++)D*D¯* molecular state [denoted as Tψ0a(4010) according to the LHCb naming convention] through triangle diagrams. The decay channels include the open-charm DD¯, and the hidden-charm ηcπ, J/ψρ, and χc1π. The coupling between the Tψ0a(4010) and its constituents D*D¯* is obtained by solving for the residue of the scattering T-matrix at the pole. Our calculations yield a total width of few tens MeV for the Tψ0a(4010) state using three different form factors, with its main decay channels being ηcπ and χc1π. The X(4100) and X(4050) have similar masses and widths, with both masses being close to the D*D¯* threshold. Additionally, their decay final states are consistent with those of the Tψ0a(4010). Therefore, it is likely that they represent the same state and both potentially correspond to the Tψ0a(4010). We suggest that future experiments focus on searching for the Tψ0a(4010) signal in the final states ηcπ−, χc1π−, and D0D− of the B0→ηcπ−K+, χc1π−K+, and D0D−K+ processes, respectively, as well as further investigating its resonance parameters with Flatté-like formula. Published by the American Physical Society 2024

Achieving ultra-low contact barriers in MX2/SiH (M = Nb, Ta; X = S, Se) metal-semiconductor heterostructures: first-principles prediction.

Minimizing the contact barriers at the interface, forming between two different two-dimensional metals and semiconductors, is essential for designing high-performance optoelectronic devices. In this work, we design different types of metal-semiconductor heterostructures by combining 2D metallic MX2 (M = Nb, Hf; X = S, Se) and 2D semiconductor SiH and investigate systematically their electronic properties and contact characteristics using first principles calculations. We find that all the MX2/SiH (M = Nb, Ta; X = S, Se) heterostructures are energetically stable, suggesting that they could potentially be synthesized in the future. Furthermore, the generation of the MX2/SiH metal-semiconductor heterostructures leads to the formation of the Schottky contact with ultra-low Schottky barriers of a few tens of meV. This finding suggests that all the 2D MX2 (M = Nb, Ta; X = S, Se) metals act as effective electrical contact 2D materials to contact with the SiH semiconductor, enabling electronic devices with high charge injection efficiency. Furthermore, the tunneling resistivity of all the MX2/SiH (M = Nb, Ta; X = S, Se) MSHs is low, confirming that they exhibit high electron injection efficiency. Our findings underscore fundamental insights for the design of high-performance multifunctional Schottky devices based on the metal-semiconductor MX2/SiH heterostructures with ultra-low contact barriers and high electron injection efficiency.

Minimal mass of thermal dark matter and the viability of millicharged particles affecting 21-cm cosmology

Thermal freeze-out offers an attractive explanation of the dark matter density free from fine-tuning of initial conditions. For dark matter with a mass below tens of MeV, photons, electrons, and neutrinos are the only available direct Standard Model annihilation products. Using a full three-sector abundance calculation, we determine the minimal mass of dark matter, allowing for an arbitrary branching into electrons/photons and neutrinos that is compatible with current cosmological observations. The analysis takes into account the heat transfer between the various sectors from annihilation elastic scattering, representing the first fully self-consistent analysis that tracks the respective sectors’ temperatures. We thereby provide accurate thermal annihilation cross sections, particularly for velocity-dependent cases, and deduce the sensitivity of current and upcoming CMB experiments to MeV thermal dark matter. In the latter context, we also establish the fine-tuned parameter region where a tiny admixture of neutrinos in the final states rules in MeV-scale p-wave annihilating DM into electrons. Finally, we show that a sub-% millicharged dark matter with an interaction strength that interferes with 21-cm cosmology is still allowed when freeze-out is supplemented with annihilation into neutrinos. For all cases considered, we provide concrete particle physics models and supplement our findings with a discussion of other relevant experimental results. Published by the American Physical Society 2024

New experimental measurements of X-ray emissions induced by protons of several tens of MeV on elements with Z=22 to Z=79: Toward quantitative high-energy PIXE

K-shell X-ray production cross-sections measurement campaigns were carried out at the ARRONAX cyclotron with titanium, chromium, copper, molybdenum, silver and gold targets for different energies from 15 to 68 MeV. These measurements, carried out using three detectors (SDD, CdTe and HPGe), complete the database with 66 new values. Our different measurements agree with previously published data and are consistent for all three detectors, confirming the absence of experimental bias. The universal ionisation cross-section representation allows an optimisation of the data using a 3rd-order polynomial function. This function can be used for HE-PIXE quantification for elements with atomic numbers between 22 (Ti) and 79 (Au) in the studied energy region.

Resonant Tunnelling and Intersubband Optical Properties of ZnO/ZnMgO Semiconductor Heterostructures: Impact of Doping and Layer Structure Variation.

ZnO-based heterostructures are up-and-coming candidates for terahertz (THz) optoelectronic devices, largely owing to their innate material attributes. The significant ZnO LO-phonon energy plays a pivotal role in mitigating thermally induced LO-phonon scattering, potentially significantly elevating the temperature performance of quantum cascade lasers (QCLs). In this work, we calculate the electronic structure and absorption of ZnO/ZnMgO multiple semiconductor quantum wells (MQWs) and the current density-voltage characteristics of nonpolar m-plane ZnO/ZnMgO double-barrier resonant tunnelling diodes (RTDs). Both MQWs and RTDs are considered here as two building blocks of a QCL. We show how the doping, Mg percentage and layer thickness affect the absorption of MQWs at room temperature. We confirm that in the high doping concentrations regime, a full quantum treatment that includes the depolarisation shift effect must be considered, as it shifts mid-infrared absorption peak energy for several tens of meV. Furthermore, we also focus on the performance of RTDs for various parameter changes and conclude that, to maximise the peak-to-valley ratio (PVR), the optimal doping density of the analysed ZnO/Zn88Mg12O double-barrier RTD should be approximately 1018 cm-3, whilst the optimal barrier thickness should be 1.3 nm, with a Mg mole fraction of ~9%.

How can we simulate ionizing radiation at aviation altitudes from TGFs?

So-called thunderclouds, which are large dark clouds that are able to generate thunder and lightning, can act as natural particle accelerators, producing complex high-energy phenomena such as terrestrial gamma-ray flashes (TGFs) and gamma-ray glows. These events are often described through the mechanism of relativistic runaway electron avalanches (RREAs), cascades of high-energy electrons accelerated by atmospheric electric fields. Since the energies of the RREAs are up to several tens of MeV, they can also trigger nuclear reactions with atoms of the air and in the soil while entering the ground. Although these phenomena are intriguing, their lack of precise measurement and still not completely understood origins pose a significant challenge for assessing their impact on aviation safety. This paper introduces the project Research Centre of Cosmic Rays and Radiation Events in Atmosphere (CRREAT), aimed at providing measurements of TGFs, thunderstorm ground enhancements (TGEs), and other ionizing radiation phenomena during thunderstorms, as well as at aviation altitudes, stratosphere, and low Earth orbits (LEO). The paper argues that without accurate data on the origins and physical characteristics of TGEs and TGFs, it is impossible to reliably simulate their impact on aircraft crews and passengers. The paper also mentions how the general-purpose 3D Monte Carlo (MC) code PHITS can be used for future simulations and comparisons with measurements related to ionizing radiation phenomena in the atmosphere.

Charmoniumlike resonant explanation on the newly observed X(3960)

Motivated by the recent observation of X(3960) by the LHCb collaboration, we adopt the one-boson-exchange model to study the DsD¯s/D⁎D¯⁎/Ds⁎D¯s⁎ interactions with I(JPC)=0(0++) after considering both the S−D wave mixing effects and the coupled channel effects. Our analysis yields the phase shifts for these coupled channel systems, and indicate the existence of a charmoniumlike resonance, whose mass and width align well with the experimental data for the newly discovered X(3960). Furthermore, our investigation reveals the significant role played by the D⁎D¯⁎ system in the formation of the X(3960) resonance, and the Ds⁎D¯s⁎ system notably contributes to the resonance's width. As a byproduct, we perform a coupled channel analysis on the D⁎D¯⁎/DsD¯s⁎/Ds⁎D¯s⁎ interactions with I(JPC)=0(1+−), our results can predict the existence of a DsD¯s⁎ molecule with 1+− and another Ds⁎D¯s⁎ molecule with 1+−. Their widths are around several and several to several tens MeV, respectively. We encourage experimental investigations to search for these two possible charmoniumlike molecular candidates, as such findings would serve to validate our research findings and proposals.

Biexciton and Singlet Trion Upconvert Exciton Photoluminescence in a MoSe2 Monolayer Supported by Acoustic and Optical K-Valley Phonons.

Transition metal dichalcogenide monolayers represent unique platforms for studying both electronic and phononic interactions as well as intra- and intervalley exciton complexes. Here, we investigate the upconversion of exciton photoluminescence in MoSe2 monolayers. Within the nominal transparency window of MoSe2 the exciton emission is enhanced for resonantly addressing the spin-singlet negative trion and neutral biexciton at a few tens of meV below the neutral exciton transition. We identify that the A'1 optical phonon at the K valley provides the energy gain in the upconversion process at the trion resonance, while ZA(K) phonons with their spin- and valley-switching properties support the biexciton driven upconversion of the exciton emission. Interestingly, the latter upconversion process yields unpolarized exciton photoluminescence, while the former also leads to circularly polarized emission. Our study highlights high-order exciton complexes interacting with optical and acoustic K-valley phonons and upconverting light into the bright exciton.

Exploring the Interaction of Cosmic Rays with Water by Using an Old-Style Detector and Rossi’s Method

Cosmic ray air showers are a phenomenon that can be observed on Earth when high-energy particles from outer space collide with the Earth’s atmosphere. These energetic particles in space are called primary cosmic rays and consist mainly of protons (about 89%), along with nuclei of helium (10%) and heavier nuclei (1%). Particles resulting from interactions in the atmosphere are called secondary cosmic rays. The composition of air showers in the atmosphere can include several high-energy particles such as mesons, electrons, muons, photons, and others, depending on the energy and type of the primary cosmic ray. Other than air, primary cosmic rays can also produce showers of particles when they interact with any type of matter; for instance, particle showers are also produced within the soil of planets without an atmosphere. In the same way, secondary cosmic particles can start showers of tertiary particles in any substance. In the 1930s, Bruno Rossi conducted an experiment to measure the energy loss of secondary cosmic rays passing through thin metal sheets. Surprisingly, he observed that as the thickness of the metal sheets increased, the number of particles emerging from the metal also increased. However, by adding more metal sheets, the number of particles eventually decreased. This was consistent with the expectation that cosmic rays were interacting with the atoms in the metals and losing energy to produce multiple secondary particles. In this paper, we describe a new–old approach for measuring particle showers in water using a cosmic ray telescope and Rossi’s method. Our instrument consists of four Geiger–Müller tubes (GMT) arranged to detect muons and particle showers. GMT sensors are highly sensitive devices capable of detecting electrons and gamma rays with energies ranging from a few tens of keV up to several tens of MeV. Since Rossi studied the effects caused by cosmic rays as they pass through metals, we wondered if the same process could also happen in water. We present results from a series of experiments conducted with this instrument, demonstrating its ability to detect and measure particle showers produced by the interaction of cosmic rays in water with good confidence. To the best of our knowledge, this experiment has never been conducted before. Our approach offers a low-cost and easy-to-use alternative to more sophisticated cosmic ray detectors, making it accessible to a wider range of researchers and students.

Free electron laser stochastic spectroscopy revealing silicon bond softening dynamics

Time-resolved x-ray emission/absorption spectroscopy (Tr-XES/XAS) is an informative experimental tool sensitive to electronic dynamics in materials, widely exploited in diverse research fields. Typically, Tr-XES/XAS requires x-ray pulses with both a narrow bandwidth and subpicosecond pulse duration, a combination that in principle finds its optimum with Fourier transform-limited pulses. In this work, we explore an alternative experimental approach, capable of simultaneously retrieving information about unoccupied (XAS) and occupied (XES) states from the stochastic fluctuations of broadband extreme ultraviolet pulses of a free electron laser. We used this method, in combination with singular-value decomposition and Tikhonov regularization procedures, to determine the XAS/XES response from a crystalline silicon sample at the ${L}_{2,3}$ edge, with an energy resolution of a few tens of meV. Finally, we combined this spectroscopic method with a pump-probe approach to measure structural and electronic dynamics of a silicon membrane. Tr-XAS/XES data obtained after photoexcitation with an optical laser pulse at 390 nm allowed us to observe perturbations of the band structure, which are compatible with the formation of the predicted precursor state of a nonthermal solid-liquid phase transition associated with a bond softening phenomenon.

Neutron emission in ultraperipheral Pb-Pb collisions at sNN=5.02 TeV

In ultraperipheral collisions (UPCs) of relativistic nuclei without overlap of nuclear densities, the two nuclei are excited by the Lorentz-contracted Coulomb fields of their collision partners. In these UPCs, the typical nuclear excitation energy is below a few tens of MeV, and a small number of nucleons are emitted in electromagnetic dissociation (EMD) of primary nuclei, in contrast to complete nuclear fragmentation in hadronic interactions. The cross sections of emission of given numbers of neutrons in UPCs of $^{208}$Pb nuclei at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV were measured with the neutron zero degree calorimeters (ZDCs) of the ALICE detector at the LHC, exploiting a similar technique to that used in previous studies performed at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. In addition, the cross sections for the exclusive emission of one, two, three, four, and five forward neutrons in the EMD, not accompanied by the emission of forward protons, and thus mostly corresponding to the production of $^{207,206,205,204,203}$Pb, respectively, were measured for the first time. The predictions from the available models describe the measured cross sections well. These cross sections can be used for evaluating the impact of secondary nuclei on the LHC components, in particular, on superconducting magnets, and also provide useful input for the design of the Future Circular Collider (FCC-hh).

An Experimental Study of Dislocation Dynamics in GaN.

The dynamics of dislocations introduced through indentation or scratching at room temperature into a few GaN layers that were grown using the HVPE, MOCVD and ELOG methods and had different dislocation densities were studied via the electron-beam-induced current and cathodoluminescence methods. The effects of thermal annealing and electron beam irradiation on dislocation generation and multiplication were investigated. It is shown that the Peierls barrier for dislocation glide in GaN is essentially lower than 1 eV; thus, it is mobile even at room temperature. It is shown that the mobility of a dislocation in the state-of-the-art GaN is not entirely determined by its intrinsic properties. Rather, two mechanisms may work simultaneously: overcoming the Peierls barrier and overcoming localized obstacles. The role of threading dislocations as effective obstacles for basal plane dislocation glide is demonstrated. It is shown that under low-energy electron beam irradiation, the activation energy for the dislocation glide decreases to a few tens of meV. Therefore, under e-beam irradiation, the dislocation movement is mainly controlled by overcoming localized obstacles.

The van der Waals Hexaquark Chemical Potential in Dense Stellar Matter

We explore the chemical potential of a QCD-motivated van der Waals (VDW) phase change model for the six-quark color-singlet, strangeness S = −2 particle known as the hexaquark with quark content (uuddss). The hexaquark may have internal structure, indicated by short range correlations that allow for non-color-singlet diquark and triquark configurations whose interactions will change the magnitude of the chemical potential. In the multicomponent VDW Equation of State (EoS), the quark-quark particle interaction terms are sensitive to the QCD color factor, causing the pairing of these terms to give different interaction strengths for their respective contributions to the chemical potential. This results in a critical temperature near 163 MeV for the color-singlet states and tens of MeV below this for various mixed diquark and triquark states. The VDW chemical potential is also sensitive to the number density, leading to chemical potential isotherms that exhibit spinodal extrema, which also depend upon the internal hexaquark configurations. These extrema determine regions of metastability for the mixed states near the critical point. We use this chemical potential with the chemical potential-modified TOV equations to investigate the properties of hexaquark formation in cold compact stellar cores in beta equilibrium. We find thresholds for hexaquark layers and changes in maximum mass values that are consistent with observations from high mass compact stellar objects such as PSR 09043 + 10 and GW 190814. In general, we find that the VDW-TOV model has an upper stability mass and radius bound for a chemical potential of 1340 MeV with a compactness of C~0.2.

Interface engineering of charge-transfer excitons in 2D lateral heterostructures

The existence of bound charge transfer (CT) excitons at the interface of monolayer lateral heterojunctions has been debated in literature, but contrary to the case of interlayer excitons in vertical heterostructure their observation still has to be confirmed. Here, we present a microscopic study investigating signatures of bound CT excitons in photoluminescence spectra at the interface of hBN-encapsulated lateral MoSe2-WSe2 heterostructures. Based on a fully microscopic and material-specific theory, we reveal the many-particle processes behind the formation of CT excitons and how they can be tuned via interface- and dielectric engineering. For junction widths smaller than the Coulomb-induced Bohr radius we predict the appearance of a low-energy CT exciton. The theoretical prediction is compared with experimental low-temperature photoluminescence measurements showing emission in the bound CT excitons energy range. We show that for hBN-encapsulated heterostructures, CT excitons exhibit small binding energies of just a few tens meV and at the same time large dipole moments, making them promising materials for optoelectronic applications (benefiting from an efficient exciton dissociation and fast dipole-driven exciton propagation). Our joint theory-experiment study presents a significant step towards a microscopic understanding of optical properties of technologically promising 2D lateral heterostructures.

Simulation of self-modulated laser wakefield acceleration using few TW in downramp injection and ionization injection regimes.

Simulations of transitional self-modulated laser wakefield acceleration driven by laser pulses of a few terawatts are discussed, comparing a downramp-based injection regime with an ionization injection regime. We demonstrate that a configuration using an N 2 gas target and a laser pulse of ∼75m J with ∼2T W peak power is a good alternative as a high repetition rate system that produces electrons of many tens of MeV, pC charge, and emittance of the order of 1mm mrad.

CNOK: A C++ Glauber model code for single-nucleon knockout reactions

A C++ program package was developed to calculate parallel momentum distributions (including the stripping mechanism and the diffractive dissociation mechanism) of the heavy residue (core) in single-nucleon knockout reactions induced by intermediate-energy (around and more than tens of MeV per nucleon) beams of stable and radioactive atomic nuclei. The program implements the Glauber reaction model that is based on the eikonal approximation and the sudden approximation when dealing with the scattering process, and uses a t-ρ-ρ method to build the projectile-target scattering optical potential, where the nucleonic densities of the core and the target are needed as input. The radial wavefunction of the valence nucleon is solved by a built-in bound-wave solver driven by a globally convergent search engine for optimized potential parameters of the valence nucleon to reproduce user-specified separation energies and root-mean-square (rms) radii of the valence nucleon. The YAML file format is adopted to facilitate user input. The program is expected to especially serve the interpretation of data analysis results of single-nucleon knockout from radioactive ion beams (RIBs), where the experimental practitioners may be more conversant with C++. Program summaryProgram Title: CNOKCPC Library link to program files:https://doi.org/10.17632/dmffpbjhsh.1Developer's repository link:https://gitee.com/asiarabbit/cnokLicensing provisions: GPLv3Programming language: C++Nature of problem: This program calculates the single-particle reaction cross sections of single-nucleon removal from stable and radioactive nuclei impinging on a light composite (i.e. non-hydrogen, e.g. carbon and beryllium) target at intermediate energies (around and more than tens of MeV per nucleon), and the parallel momentum (stripping+diffractive dissociation) distributions of the core, for a pure valence configuration (bound core state+valence nucleon single-particle orbit).Solution method: The bound radial wavefunction of the valence nucleon in a Woods-Saxon (WS) potential is solved following the method of shooting to a fitting point, where the wavefunction is integrated with Runge-Kutta method from 0 and some large distance r∞ to a matching point rm near the nuclear surface. The process is iterated to optimize the eigenvalue Enlj by joining the two waves at rm “smoothly”. Most integrals are evaluated with Simpson's rules, while some with Romberg integration. Searching in the (V0,r0) space of the central WS potential to reproduce the user-specified separation energy and rms radius of the valence nucleon is done via a globally convergent Newton-Raphson root-finding routine for nonlinear systems of equations.Additional comments including restrictions and unusual features: User input is read in with YAML parser (yaml-cpp). Global parameters are readily accessed and uniformly modified in a singleton class. General algorithms (integration, interpolation, minimization, and root-finding routines) are implemented with C++ template class or functors, which adapt to different data types and/or function types. Various batch modes are wrapped in the program package to save user time. For instance, in one run, with the batch mode, one can calculate inclusive single-nucleon removal cross section involving many valence configurations, the relevant inclusive core momentum distribution, and similarly for a series of projectile+target combinations in study of systematics, as is frequently encountered in the study of quenching of single-particle-orbit occupancies (spectroscopic factors) in single-nucleon knockout reactions. Unit tests with Catch are widely deployed to facilitate debugging. C++11 support is required for compilers.

Spectral function of the η′ meson in nuclear medium based on phenomenological models

The in-medium modification of the spectral function of the $\eta'$ meson with and without the spatial momentum is studied with the $T\rho$ approximation by employing two phenomenological models for the $\eta'N$ scattering; one is called coupled channels model and the other the $N(1895)$-dominance model. In the former model, the $\eta'N$ scattering amplitude is calculated in the unitarized coupled-channel approach involving the $\eta'N$ channel, while in the latter model the $\eta'N$ scattering process is dominated by the $N(1895)$ resonance with the spin and parity $J^P=1/2^-$. In the \com{coupled channels model}, one single peak of the in-medium $\eta'$ mode appears in the spectral function and the peak position shifts to higher energies along with the increase of the nuclear density reflecting the repulsive $\eta'N$ scattering length of the unitarized coupled-channel amplitude. On the other hand, two branches related to the $\eta'$ and $N(1895)$-hole modes appear in the $N(1895)$-dominance model. In both models, the shift of the peak position and the width in the spectral function are a few tens of MeV at the normal nuclear density for the $\eta'$ meson at rest in the nuclear medium. Once the spatial momentum is turned on, the peak positions in the spectral function approach the energies without the nuclear medium effect. Particularly, in the $N(1895)$-dominance model, the peak strength of the $N(1895)$-hole mode gets smaller with the finite momentum and the spectral function comes to have one single peak.

Radiative Reconnection-powered TeV Flares from the Black Hole Magnetosphere in M87

Active galactic nuclei in general, and the supermassive black hole in M87 in particular, show bright and rapid gamma-ray flares up to energies of 100 GeV and above. For M87, the flares show multiwavelength components, and the variability timescale is comparable to the dynamical time of the event horizon, suggesting that the emission may come from a compact region near the nucleus. However, the emission mechanism for these flares is not well understood. Recent high-resolution general-relativistic magnetohydrodynamic simulations show the occurrence of episodic magnetic reconnection events that can power flares near the black hole event horizon. In this work, we analyze the radiative properties of the reconnecting current layer under the extreme plasma conditions applicable to the black hole in M87 from first principles. We show that abundant pair production is expected in the vicinity of the reconnection layer, to the extent that the produced secondary pair plasma dominates the reconnection dynamics. Using analytic estimates backed by two-dimensional particle-in-cell simulations, we demonstrate that in the presence of strong synchrotron cooling, reconnection can produce a hard power-law distribution of pair plasma imprinted in the outgoing synchrotron (up to a few tens of MeV) and the inverse-Compton signal (up to TeV). We produce synthetic radiation spectra from our simulations, which can be directly compared with the results of future multiwavelength observations of M87* flares.