Journal of Physics G: Nuclear and Particle Physics

A secondary electron emission (SEE) model for 0.1–10 keV x-ray-induced photoelectric emission (PE) from semiconductors and insulators (SIs) was developed here. Based on this model, theories of thermal emission and the characteristics of electron-induced SEE and x-ray-induced PE, the methods of obtaining B_PE, and the mean escape depth of 0.1–10 keV x-ray-induced true secondary electrons λ_PE from SI and ε_PE are presented, respectively, where B_PE denotes the mean probability that an internal true secondary electron excited by x-ray escapes into a vacuum upon reaching the emission surface of the SI, and ε_PE denotes the average energy required to produce a true secondary electron in the SI by x-ray. Based on the parameters of vacuum-evaporated alkali halides, existing theories on the propagation of secondary electrons from SI and the theories developed here, the universal formula for λ_PE of vacuum-evaporated alkali halides in the photon energy range of 0.1–10 keV was obtained, and the methods of calculating the spectra of x-ray-induced true secondary electrons, x-ray attenuation cross-sections and x-ray penetration depth are presented.

In this study, we analyze the influence of non-standard interaction (NSI) on steering in three-flavor neutrino oscillations, with a focus on the NOνA and DUNE experimental setups. DUNE, having a longer baseline, exhibits a more pronounced deviation towards NSI in steering compared to NOνA. Within the energy range where DUNE's maximum flux appears, the steering value for DUNE shows a 21% deviation from the standard model (SM) to NSI for normal ordering (NO), while for inverted ordering (IO), the steering value increases by approximately 15% relative to the SM. We conduct a comparative analysis of nonlocality, steering, and entanglement. Additionally, we express steering in terms of three-flavor neutrino oscillation probabilities and explore the relationship between steering inequality and concurrence.

Quantum chromodynamics admits a CP violating contribution to the action, the θ term, which is expected to give rise to a nonvanishing electric dipole moment of the neutron. Despite intensive search, no CP violations have been found in the strong interaction. This puzzle is referred to as the strong CP problem. There is evidence that CP is conserved in the confining theory, to the extent that color charges are totally screened for θ > 0 at large distances. It is not immediately obvious that this implies a vanishing dipole moment though. With this Letter I will close the gap. It is shown that in the infinite volume hadron correlation functions decouple from the topological charge, expressed in terms of the zero modes. The reason is that hadrons have a limited range of interaction, while the density of zero modes vanishes with the inverse root of the volume, thus reducing the probability of finding a zero mode in the vicinity to zero. This implies that CP is conserved in the strong interaction.

It is well known that the coupling of an axion-like particle with a photon modifies the Maxwell equations. One of the main consequences of these modifications is the conversion of axions into photons. Little has been said about other possible effects. In this paper we show that the trajectory of an electron can be significantly altered because of the emergence of an electric field due to the dark matter background of the axion-like particles in this modified axion-electrodynamics. Different dark matter densities and magnetic field strengths are considered and it is shown that an axion-like particle with a mass m_a ∼ 10⁻²² eV generates an electric field that can significantly change the trajectory of an electron in these scenarios.

Using the ab initio symmetry-adapted no-core–shell model, we compute sum rules and response functions for light to medium-mass nuclei, starting from interactions that are derived in the chiral effective field theory. Specifically, we investigate electromagnetic transitions of monopole, dipole and quadrupole nature for ⁴He, and explore dominant features of giant monopole resonances in symmetric nuclei such as the closed-shell ⁴He and ¹⁶O light nuclei, the intermediate-mass open-shell ²⁰Ne and the medium-mass closed-shell ⁴⁰Ca. Furthermore, for the NNLO_opt chiral potential, we determine parameter-free monopole sum rules, which can provide information on the incompressibility of symmetric nuclear matter. We report 213(10) MeV as an estimate for the compression modulus for infinite nuclear matter, which overlaps with the lower range of values often used in current astrophysical applications.

Collective modes emerge as the relevant degrees of freedom that govern low-energy excitations of atomic nuclei. These modes—rotations, pairing rotations, and vibrations—are separated in energy from non-collective excitations, making it possible to describe them in the framework of effective field theory. Rotations and pairing rotations are the remnants of Nambu–Goldstone modes from the emergent breaking of rotational symmetry and phase symmetries in finite deformed and finite superfluid nuclei, respectively. The symmetry breaking severely constrains the structure of low-energy Lagrangians and thereby clarifies what is essential and simplifies the description. The approach via effective field theories exposes the essence of nuclear collective excitations and is defined with a breakdown scale in mind. This permits one to make systematic improvements and to estimate and quantify uncertainties. Effective field theories of collective excitations have been used to compute spectra, transition rates, and other matrix elements of interest. In particular, predictions of the nuclear matrix element for neutrinoless double beta decay then come with quantified uncertainties. This review summarizes these results and also compares the approach via effective field theories to well-known models and ab initio computations.

In modern high energy physics (HEP) experiments, triggers perform the important task of selecting, in real time, the data to be recorded and saved for physics analyses. As a result, trigger strategies play a key role in extracting relevant information from the vast streams of data produced at facilities like the large hadron collider (LHC). As the energy and luminosity of the collisions increase, these strategies must be upgraded and maintained to suit the experimental needs. This whitepaper presents a high-level overview and reviews recent developments of triggering practices employed at the LHC. The general trigger principles applied at modern HEP experiments are highlighted, with specific reference to the current trigger state-of-the-art within the ALICE, ATLAS, CMS and LHCb collaborations. Furthermore, a brief synopsis of the new trigger paradigm required by the upcoming high-luminosity upgrade of the LHC is provided. This whitepaper, compiled by Early Stage Researchers of the SMARTHEP network, is not meant to provide an exhaustive review or substitute documentation and papers from the collaborations themselves, but rather offer general considerations and examples from the literature that are relevant to the SMARTHEP network.

Collective anisotropic flow, where particles are correlated over the entire event, is a prominent phenomenon in relativistic heavy-ion collisions and is sensitive to the properties of the matter created in those collisions. It is often measured by two- and multi-particle correlations and is therefore contaminated by nonflow, those genuine few-body correlations unrelated to the global event-wise correlations. Many methods have been devised to estimate nonflow contamination with various degrees of successes and difficulties. Here, we review those methods pedagogically, discussing the pros and cons of each method, and give examples of ballpark estimate of nonflow contamination and associated uncertainties in relativistic heavy-ion collisions. We hope such a review of the various nonflow estimation methods in a single place would prove helpful to future researches.

Heavy-ion collisions provide a window into the properties of many-body systems of deconfined quarks and gluons. Understanding the collective properties of quarks and gluons is possible by comparing models of heavy-ion collisions to measurements of the distribution of particles produced at the end of the collisions. These model-to-data comparisons are extremely challenging, however, because of the complexity of the models, the large amount of experimental data, and their uncertainties. Bayesian inference provides a rigorous statistical framework to constrain the properties of nuclear matter by systematically comparing models and measurements. This review covers model emulation and Bayesian methods as applied to model-to-data comparisons in heavy-ion collisions. Replacing the model outputs (observables) with Gaussian process emulators is key to the Bayesian approach currently used in the field, and both current uses of emulators and related recent developments are reviewed. The general principles of Bayesian inference are then discussed along with other Bayesian methods, followed by a systematic comparison of seven recent Bayesian analyses that studied quark-gluon plasma properties, such as the shear and bulk viscosities. The latter comparison is used to illustrate sources of differences in analyses, and what it can teach us for future studies.

Baryon number conservation is not guaranteed by any fundamental symmetry within the standard model, and therefore has been a subject of experimental and theoretical scrutiny for decades. So far, no evidence for baryon number violation has been observed. Large underground detectors have long been used for both neutrino detection and searches for baryon number violating processes. The next generation of large neutrino detectors will seek to improve upon the limits set by past and current experiments and will cover a range of lifetimes predicted by several Grand Unified Theories. In this White Paper, we summarize theoretical motivations and experimental aspects of searches for baryon number violation in neutrino experiments.

We present a systematic study of the PYTHIA 8.311 model under various hadronization mechanisms to investigate proton, charged pion, and charged kaon production in inelastic proton-proton collisions at CERN SPS energies ranging from 20 to 158 GeV/c. Specifically, we compare four hadronization scenarios: (i) the default popcorn mechanism, which permits extended string configurations with intermediate meson formation between baryon-antibaryon pairs; (ii) a diquark scenario utilizing a QCD-based color reconnection scheme (CR1) designed to minimize string lengths, thereby restricting baryon production exclusively to baryon-antibaryon pairs; (iii) a junction-based scenario where baryon number is carried by non-perturbative QCD string junctions; and (iv) a thermal model featuring string tension fluctuations, leading to a thermal-like transverse momentum distribution. Our results indicate that the default popcorn approach inadequately describes proton stopping and hadron distributions at mid-rapidity, especially at lower collision energies. In contrast, the diquark scenario significantly enhances the accuracy of proton rapidity distributions, while the thermal model further improves the reproduction of pion spectra at lower transverse momenta and captures essential features of strangeness production, specifically suppressing $K^-$ at central rapidity ($y < 1$) and enhancing $K^+$ yields. Conversely, the junction-based scenario provides no substantial improvement at higher SPS energies. These findings underscore the necessity of refined hadronization descriptions for accurately modeling particle production at SPS energies.

The European Spallation Source (ESS) will be the world's brightest neutron source and will open a new intensity frontier in particle physics. The HIBEAM collaboration aims to exploit the unique potential of the ESS with a dedicated ESS instrument for particle physics which offers world-leading capability in a number of areas. The HIBEAM program includes the first search in thirty years for free neutrons converting to antineutrons and searches for sterile neutrons, ultralight axion dark matter and nonzero neutron electric charge. This paper outlines the capabilities, design, infrastructure, and scientific potential of the HIBEAM program, including its dedicated beamline, neutron optical system, magnetic shielding and control, and detectors for neutrons and antineutrons. Additionally, we discuss the long-term scientific exploitation of HIBEAM, which may include measurements of the neutron electric dipole moment and precision studies of neutron decays.

Lattice QCD calculations of the 2s radial excitation of the nucleon place the state at an&#xD;energy of approximately 1.9 GeV, raising the possibility that it is associated with the N1/2⁺(1880)&#xD;and N1/2⁺(1710) resonances through mixing with two-particle meson-baryon states. The discovery&#xD;of the N1/2⁺(1880) resonance in pion photoproduction but not in πN scattering and the small&#xD;width of the N1/2⁺(1710) resonance suggest that a state associated with these resonances would&#xD;be insensitive to the manner in which pions are permitted to dress it. To explore this possibility,&#xD;we examine the spectrum of nucleon radial excitations in both 2+1 flavour QCD and in simulations&#xD;where the coupling to meson-baryon states is significantly modified through quenching. We find the&#xD;energy of the 2s radial excitation to be insensitive to this modification for quark masses close to the&#xD;physical point. This invariance provides further evidence that the 2s radial excitation of the nucleon&#xD;is associated with the N1/2⁺(1880) and N1/2⁺(1710) resonances.

Inspired by the discrepancies observed in the b → s ℓ⁺ℓ^- neutral current decays, we study the decay channel B_c → D_s^(∗) ℓ⁺ℓ^- (ℓ=μ,τ), which is based on the same flavor changing neutral current (FCNC) transition at the quark level. The current study shows that this decay channel can provide a useful probe for physics beyond the standard model. We use the helicity formalism while employing the effective theory approach where we include the effects of vector and axial vector `new' physics (NP) operators. In this study, we have computed the branching ratio B_r, the D^∗ helicity fraction f_L , the lepton forward-backward asymmetry A_FB , and the lepton flavor universality ratio (LFU) R^μτ_Ds^∗. In addition, as a complementary check on the LFU, we also calculate the various other LFU observables, R_i^μτ where i=A_AB, f_L . We assume that the NP universal coupling is present for both muons and tauons, while the non-universal coupling is only present for muons. Regarding these couplings, we employ the latest global fit to the b → s ℓ⁺ℓ^- data, which is recently computed in \cite{Alguero:2023jeh}. We give predictions of some of the mentioned observables within the SM and the various NP scenarios. We have found that not only are the considered observables sensitive to NP but are also helpful in distinguishing among the different NP scenarios. These results can be tested at the LHCb, HL-LHC, and FCC-ee, and therefore, a precise measurements of these observables not only deepens our understanding of the b → s ℓ⁺ℓ^- process but also provides a window of opportunity to possibly study various NP scenarios.

We consider the electromagnetic form factors ratio in the Rosenbluth and polarization methods. We explore the impact of adding new particles as the mediators in the electron-proton scattering on these ratios. We show that such new particles can compensate the difference between the two methods and potentially solve this paradox. Consequently, we find some bound on the scalar coupling as $\alpha_{sc}\sim 10^{-5}$ for $m_{sc}\sim$ 5 MeV-2 GeV and $\alpha_{sc}\sim 10^{-4}-10^{-3}$ for $m_{sc}\sim$ 2-10 GeV. Meanwhile, the vector coupling is bounded as $\alpha_v\sim 10^{-5}$ for $m_v\sim$ 5 MeV-1.1 GeV and $\alpha_v\sim 10^{-4}-10^{-3}$ for $m_v\sim$ 1.2-10 GeV. These constraints are in complete agreement with those which is found from other independent terrestrial experiments.

The European Spallation Source (ESS) will be the world's brightest neutron source and will open a new intensity frontier in particle physics. The HIBEAM collaboration aims to exploit the unique potential of the ESS with a dedicated ESS instrument for particle physics which offers world-leading capability in a number of areas. The HIBEAM program includes the first search in thirty years for free neutrons converting to antineutrons and searches for sterile neutrons, ultralight axion dark matter and nonzero neutron electric charge. This paper outlines the capabilities, design, infrastructure, and scientific potential of the HIBEAM program, including its dedicated beamline, neutron optical system, magnetic shielding and control, and detectors for neutrons and antineutrons. Additionally, we discuss the long-term scientific exploitation of HIBEAM, which may include measurements of the neutron electric dipole moment and precision studies of neutron decays.

It is well known that the coupling of an axion-like particle with a photon modifies the Maxwell equations. One of the main consequences of these modifications is the conversion of axions into photons. Little has been said about other possible effects. In this paper we show that the trajectory of an electron can be significantly altered because of the emergence of an electric field due to the dark matter background of the axion-like particles in this modified axion-electrodynamics. Different dark matter densities and magnetic field strengths are considered and it is shown that an axion-like particle with a mass m_a ∼ 10⁻²² eV generates an electric field that can significantly change the trajectory of an electron in these scenarios.

Lattice QCD calculations of the 2s radial excitation of the nucleon place the state at an&#xD;energy of approximately 1.9 GeV, raising the possibility that it is associated with the N1/2⁺(1880)&#xD;and N1/2⁺(1710) resonances through mixing with two-particle meson-baryon states. The discovery&#xD;of the N1/2⁺(1880) resonance in pion photoproduction but not in πN scattering and the small&#xD;width of the N1/2⁺(1710) resonance suggest that a state associated with these resonances would&#xD;be insensitive to the manner in which pions are permitted to dress it. To explore this possibility,&#xD;we examine the spectrum of nucleon radial excitations in both 2+1 flavour QCD and in simulations&#xD;where the coupling to meson-baryon states is significantly modified through quenching. We find the&#xD;energy of the 2s radial excitation to be insensitive to this modification for quark masses close to the&#xD;physical point. This invariance provides further evidence that the 2s radial excitation of the nucleon&#xD;is associated with the N1/2⁺(1880) and N1/2⁺(1710) resonances.

Collective modes emerge as the relevant degrees of freedom that govern low-energy excitations of atomic nuclei. These modes—rotations, pairing rotations, and vibrations—are separated in energy from non-collective excitations, making it possible to describe them in the framework of effective field theory. Rotations and pairing rotations are the remnants of Nambu–Goldstone modes from the emergent breaking of rotational symmetry and phase symmetries in finite deformed and finite superfluid nuclei, respectively. The symmetry breaking severely constrains the structure of low-energy Lagrangians and thereby clarifies what is essential and simplifies the description. The approach via effective field theories exposes the essence of nuclear collective excitations and is defined with a breakdown scale in mind. This permits one to make systematic improvements and to estimate and quantify uncertainties. Effective field theories of collective excitations have been used to compute spectra, transition rates, and other matrix elements of interest. In particular, predictions of the nuclear matrix element for neutrinoless double beta decay then come with quantified uncertainties. This review summarizes these results and also compares the approach via effective field theories to well-known models and ab initio computations.

Starting from the measurements conducted in 2004 with the ADAMO silicon spectrometer, we have performed a 2D fit procedure to diverse combinations of muon flux datasets documented in the literature. The fit employed three different formulas describing the energy and angular distribution of atmospheric muons at the Earth's surface. The analysis revealed that some measurements showed discrepancies in their compatibility with the expected results or between them with variations greater than a few sigmas. For example, vertical measurements expand over a wide range of flux values even for similar setup experiments. However, we have identified a formula capable of furnishing comprehensive spectrum coverage utilizing a singular set of parameters. Despite inherent limitations, we have achieved a satisfactory agreement with the Guan parameterization. Subsequently, we have integrated this optimized parameterization into the EcoMug library and a Geant4-based muon generator. The model's predictive capabilities have been validated by comparing it with experimental flux measurements and against other measurements in the literature. Through this process, we have shown and tested the reliability and accuracy of different muon flux modelling, facilitating advancements in domains reliant on the precise characterization of atmospheric muon phenomena.

Transverse momentum correlations were recently measured by the ALICE collaboration at the LHC [Acharya etal (2020 Phys. Lett. B804 135375)]. A long-range structure in terms of relative pseudorapidity of particle pairs is observed. This may imply some signal of the initial state owing to the sheer spread of the correlation. However, the fluctuations inside a thermally equilibrated medium have to be taken into account, serving as motivation for this paper. Using lattice Quantum Chromodynamics constraints, we predicted the development and spread of balancing correlations caused by energy-momentum conservation. At the same time, we propagated the Gaussian-shaped initial correlation using hydrodynamics to estimate its effects. Our findings suggest that the resulting correlation, known as 'the ridge,' is sensitive both to flucutations seeded in the pre-equilibrium stage and to those seeded in the equilibrated medium. This can provide important insight into the early stages of the collision.

In modern high energy physics (HEP) experiments, triggers perform the important task of selecting, in real time, the data to be recorded and saved for physics analyses. As a result, trigger strategies play a key role in extracting relevant information from the vast streams of data produced at facilities like the large hadron collider (LHC). As the energy and luminosity of the collisions increase, these strategies must be upgraded and maintained to suit the experimental needs. This whitepaper presents a high-level overview and reviews recent developments of triggering practices employed at the LHC. The general trigger principles applied at modern HEP experiments are highlighted, with specific reference to the current trigger state-of-the-art within the ALICE, ATLAS, CMS and LHCb collaborations. Furthermore, a brief synopsis of the new trigger paradigm required by the upcoming high-luminosity upgrade of the LHC is provided. This whitepaper, compiled by Early Stage Researchers of the SMARTHEP network, is not meant to provide an exhaustive review or substitute documentation and papers from the collaborations themselves, but rather offer general considerations and examples from the literature that are relevant to the SMARTHEP network.

We consider a general model for a quasi-spherical explosion in which a part of the explosion energy is thermalized, forming an expanding photosphere around a compact object, and the second part of energy is taken by the expanding shell of material which forms a shock wave in the surrounding medium. Different types of particles (electrons, hadrons) can, in principle, be accelerated at the shock. They interact with the thermal radiation from the photosphere and also with the material at the shell. We determine the equilibrium spectra of particles in the shell as a function of time after explosion and calculate the time-dependent γ-ray spectra by taking into account the effects which are due to the anisotropy of the photo-spheric radiation field on the Inverse Compton (IC) process; we also include the absorption of IC γ-rays in the photosphere radiation. We conclude that, in principle, both leptonic and hadronic models can explain the GeV-TeV gamma-ray emission recently detected from the Nova RS Oph. However, the hadronic model, in comparison to the leptonic model, is more energetically demanding and requires much stronger magnetization of the nova shell.

We present progress towards the first unpolarized gluon quasi-parton distribution function (PDF) from lattice quantum chromodynamics using high-statistics measurements for hadrons at two valence pion masses M_π ≈ 310 and 690 MeV computed on an a ≈ 0.12 fm ensemble with 2 + 1 + 1-flavors of highly improved staggered quark generated by the MILC collaboration. In this study, we consider two gluon operators for which the hybrid-ratio renormalization matching kernels have been recently derived and a third operator that has been used in prior pseudo-PDF studies of the gluon PDFs. We compare the matrix elements for each operator for both the nucleon and pion, at both pion masses, and using two gauge-smearing techniques. Focusing on the more phenomenologically studied nucleon gluon PDF, we compare the ratio and hybrid-ratio renormalized matrix elements at both pion masses and both smearings to those reconstructed from the nucleon gluon PDF from the CT18 global analysis. We identify the best choice of operator to study the gluon PDF and present the first gluon quasi-PDF under some caveats. Additionally, we explore the recent idea of Coulomb gauge fixing to improve signal at large Wilson-line displacement and find it could be a major help in improving the signal in the gluon matrix elements. This work helps identify the best operator for studying the gluon quasi-PDF, shows higher hadron boost momentum is needed to implement hybrid-ratio renormalization reliably, and suggests the need to study more diverse set of operators with their corresponding perturbative calculations for hybrid-ratio renormalization to further gluon quasi-PDF study.

The quantum molecular dynamics (QMD) part of the UrQMD model is extended to allow implementation of momentum dependent potentials from a parity doubling chiral mean field (CMF) model. Important aspects like energy conservation and effects on particle production and flow are discussed. It is shown, that this new implementation reproduces qualitatively and quantitatively available data over a wide range of beam energies and improves the description of observables without exception. In particular the description of hyperon and pion production at SIS18 energies is improved. From a comparison with HADES data one could conclude that the present parametrization of the CMF model leads to a slightly too weak momentum dependence. However, a more firm conclusion will require a systematic comparison with flow and multiplicity data over a range of beam energies and system sizes. Our work serves as an important step towards such future studies where the properties of dense QCD matter, through parameters of the CMF model, can be constraint using a comparison of the UrQMD model with high precision heavy ion data, finally also allowing direct comparisons with neutron star and neutron star merger observables.