Journal of Physics G: Nuclear and Particle Physics

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.

In this study, we present a detailed approach for detecting reactor neutrinos by employing gadolinium-doped plastic scintillators combined with machine learning techniques. The proposed detector design was simulated using the Geant4 framework, featuring segmented modules of plastic scintillators doped with gadolinium to enhance neutron capture efficiency. Inverse beta decay (IBD) events generated by ERNIE and background events produced by cosmic ray simulations were used to train and test an Extreme Gradient Boosting (XGBoost) model for signal-background discrimination. The model demonstrated high discrimination accuracy for prompt IBD events but encountered challenges with delayed neutron background discrimination due to similarities in neutron capture. Performance comparisons with traditional cut-based analyses highlighted the improved accuracy achieved through machine learning, particularly when utilizing additional event features. This work establishes the potential of gadolinium-doped plastic scintillators and machine learning in enhancing neutrino detection and lays the groundwork for future experimental validation and detector optimization.

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.

In this study, we analyze the influence of Non-Standard Interaction (NSI) on steering in three-flavor neutrino oscillations, with a focus on the NO$\nu$A and DUNE experimental setups. DUNE, having a longer baseline, exhibits a more pronounced deviation towards NSI in steering compared to NO$\nu$A. 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.

It is well known that the coupling of the axion-like particle with the photon modifies 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 note, we show that the trajectory of an electron can be significantly altered because of the emergence of an electric field by the axion-like particles dark matter background 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^-22eV generates an electric field that can change the trajectory of an electron significantly in these scenarios.

We investigate the chiral phase diagram in the NJL model with a modified coupling strength. Moreover, we delve deeply into the fluctuations of baryon numbers. A temperature damping factor for the coupling strength is introduced to mimic the temperature dependence of QCD in the low and middle temperature ranges. This novel parameter is fitted by using the quark condensate from lattice QCD at finite temperature. Remarkably, the chiral phase diagram is greatly enhanced in the crossover region. The quark condensate is used to ascertain the location of the phase transition, and we find an area where both phases coexist. The chiral susceptibility is employed to identify the pseudo-critical line in the crossover region. The skewness ratios and the kurtosis ratios varying with $T$ at several different $\mu_B$ are calculated meticulously, and the results demonstrate that they experience a significant change around the pseudo-critical line. Additionally, the skewness ratios and the kurtosis ratios along the pseudo-critical line ($T_c(\mu_B)$) and the lines deviating from $T_c(\mu_B)$ are computed to gain a better understanding of the experimental results. This implies that the freeze-out line is relatively far from the critical end point.

Using the \textit{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 $^4$He, and explore dominant features of giant monopole resonances in symmetric nuclei such as the closed-shell $^4$He and $^{16}$O light nuclei, the intermediate-mass open-shell $^{20}$Ne and the medium-mass closed-shell $^{40}$Ca. Furthermore, for the NNLO$_{\rm opt}$ 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.

We investigate the relative yields of various like and unlike mass hadrons in ultra-relativistic heavy-ion collisions (URHIC). In the framework of thermal model a strong evidence of strangeness imbalance is observed in the experiments at lower collision energies relative to non-strange particles, particularly pions. The study indicates that like mass particle ratios in the system at the chemical freeze-out in URHIC can be described effectively by considering baryons (antibaryons) as point like as well as finite size particles which imitates hard-core repulsive interactions leading to an excluded volume type effect. In this analysis, we employ the statistical Hadron Resonance Gas (HRG) model for both cases. A comparison between the two cases is provided. However, the importance of considering baryons (antibaryons) as finite size particles is revealed in the description of baryon to meson ratios. Best fits to particle ratios are obtained using $\chi^{2}$-minimization procedure. For the case of finite-size baryons (antibaryons), we find that considering their hard-core radii allows us to fit the available antibaryon-to-baryon and baryon (antibaryon)-to-pion ratio experimental data simultaneously quite well with the same model parameter values. Moreover, our results align well with the proton radius puzzle observed in the muonic hydrogen measurement data. Furthermore, the study reveals two distinct chemical freeze-out stages in both cases, where the earlier one corresponds to baryonic (hyperonic) and antibaryonic (antihyperonic) states and a later one to mesonic degrees of freedom. A comparison of freeze-out lines obtained from both the cases is made along with the results of some earlier studies.

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.

It is well known that the coupling of the axion-like particle with the photon modifies 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 note, we show that the trajectory of an electron can be significantly altered because of the emergence of an electric field by the axion-like particles dark matter background 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^-22eV generates an electric field that can change the trajectory of an electron significantly in these scenarios.

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.

The cross sections for the production of medically significant radioisotopes, including ⁶⁸Ge, ⁶⁹Ge, ⁶⁶Ga, ⁶⁷Ga, ⁷²As and various radioimpurities produced in pure germanium crystal irradiated with 60 MeV protons, were measured. The experiment utilized germanium targets with natural isotopic composition. Irradiation of the targets was performed using a proton beam from the AIC-144 accelerator at the Institute of Nuclear Physics, Polish Academy of Sciences, Krakow. Gamma spectroscopy was conducted with high-purity germanium detectors to measure the gamma-ray emissions from the irradiated targets. This enabled the determination of reaction cross-sections of the produced radionuclides. Additionally, our results were compared with existing literature and TALYS data to validate our findings. Generally, our experimental results align with previous studies, although discrepancies were observed in certain aspects. Specifically, nuclear model calculations and some literature data indicate slightly higher values compared to our findings.

In this work we present to our knowledge the most precise measurement of the ⁷Be electron capture decay half-life in a host material. A silicon carbide sample with ~8.62 × 10⁹⁷Be atoms was measured for 83.5 d on an ultra-low background high purity Ge detector located deep underground in the Laboratori Nazionali del Gran Sasso, Italy. The result obtained for the decay half-life is T_1/2 = 53.284 ± 0.016 d, which corresponds to an uncertainty of 0.3‰. Thanks to the high sensitivity achieved, this measurement is paving the way to further investigations on this process aiming to understand how environmental conditions may affect the decay half-life.