Nuclear Medium Research Articles

Nuclear medium effects on the properties of Λ(1405)

We study the Λ(1405) resonance with I(J P ) = 0(1/2−) in the context of the pentaquark hypothesis in the nuclear medium. To explore the influence of the nuclear medium on the physical parameters of Λ(1405), we propose a molecular-type structure involving admixtures of K − p and K¯0n , correlated with the nuclear matter density. Our analysis reveals a substantial shift in mass and residue, approximately 20% and 38%, respectively. These findings have significant implications for experimental researchers aiming to identify in-medium characteristics of hyperon resonances.

Transverse-momentum dependent model for hadronization in deep-inelastic lepton-nucleus scattering off heavy nuclei

Semi-inclusive deep inelastic scattering off nuclei is a unique process to study the parton propagation mechanism and its modification induced by the presence of the nuclear medium. It allows us to probe the medium properties, particularly the cold nuclear matter transport coefficient, which can be directly linked to the nuclear gluon density. We present here a model for hadron production in deep inelastic lepton-nucleus scattering, which takes into account the hadronic transverse momentum of final state particles via transverse-momentum dependent parton distributions and fragmentation functions. We implement parton energy loss and hadronic absorption with a geometrical model of the nucleus. The model is compared with the nuclear semi-inclusive deep-inelastic scattering multiplicity ratios and transverse-momentum broadening data from the CLAS, HERMES, and EMC collaborations, aiming for a simultaneous description of these data sets. We obtain a good agreement over the various nuclear targets and the wide kinematical range of those experiments. We best describe the data with a transport coefficient q̂=0.3GeV/fm2, and we highlight the importance and the role of correlations in extracting this quantity. Published by the American Physical Society 2024

Event generator for jet tomography in electron-ion collisions

We develop the first event generator, the electron-heavy-ion-jet-interaction-generator (eHIJING), for the jet tomography study of electron-ion collisions. In this generator, energetic jet partons produced from the initial hard scattering undergo multiple collisions with the nuclear target. The collision rate is proportional to the transverse-momentum-dependent (TMD) gluon density in the nucleus, which is given by a simple model inspired by the physics of gluon saturation. Medium-modified QCD splitting functions within the higher-twist (HT) and generalized higher-twist (GHT) frameworks are utilized to simulate parton showering in the nuclear medium that takes into account the non-Abelian Landau-Pomeranchuck-Midgal interference effect. Employing eHIJING, we revisit hadron production in semi-inclusive deep inelastic scattering (SIDIS) as measured by EMC, HERMES, and recent CLAS experiments. eHIJING with both GT and GHT frameworks gives reasonably good descriptions of these experimental data. Predictions for experiments at the future electron-ion colliders are also provided. It is demonstrated that future measurements of the transverse momentum broadening of single hadron spectra can be used to map out the two-dimensional kinematic (Q2, xB) dependence of the jet transport coefficient q^ in cold nuclear matter. Published by the American Physical Society 2024

Nuclear medium meson structures from the Schwinger proper-time Nambu–Jona-Lasinio model

In this paper, we report the results of our study on the nuclear medium modifications of the meson electromagnetic form factors in the framework of the Nambu–Jona-Lasinio model with the help of the Schwinger proper-time regularization scheme to tame the loop divergence and simulate the effect of QCD confinement. In our current approach, the meson structure and nuclear medium are constructed in the same Nambu–Jona-Lasinio model at the quark level. We examine the free-space and in-medium charge radii of kaon and pion, the spacelike elastic electromagnetic form factors of kaon and pion, and their quark-sector form factors, which reflect their internal structures. By comparing our result to experimental data, we found that the free-space elastic electromagnetic form factors of the mesons are consistent with the data, while the in-medium elastic electromagnetic form factors of the mesons are found to decrease as the nuclear matter density increases, leading to a rise of meson charge radius, which is consistent with the prediction of other theoretical calculations. We also predict the axial nucleon coupling constant gA in nuclear medium computed via the Goldberger-Treiman relation, which is crucial for searching the neutrinoless double beta decay (0νββ). Published by the American Physical Society 2024

One-jettiness DIS event shape at N3LL+O(αs2)

We present results for the τ1 and τ1a 1-jettiness global event shape distributions, for deep inelastic scattering (DIS), at the N3LL+O(αs2) level of accuracy. These event-shape distributions quantify and characterize the pattern of final state radiation in electron-nucleus collisions. They can be used as a probe of nuclear structure functions, as nuclear medium effects in jet production, and for a precision extraction of the QCD strong coupling. The results presented here, along with the corresponding numerical codes, can be used for analyses with HERA data, in Electron-Ion Collider (EIC) simulation studies, and for eventual comparison with real EIC data. Published by the American Physical Society 2024

Charmonium production in hot magnetized hyperonic matter: Effects of the baryonic Dirac sea and pseudoscalar-vector mixing

We investigate the medium modifications of the masses of pseudoscalar open charm (D and D¯) mesons and the charmonium state [ψ(3770)] in hot isospin asymmetric strange hadronic medium in the presence of an external magnetic field within a chiral effective model. The in-medium partial decay widths of ψ(3770) to charged and neutral DD¯ mesons are computed from the medium modifications of the masses of the initial and final state mesons. These are computed using two light quark pair creation models—(I) the P03 model and (II) a field theoretical (FT) model of composite hadrons with quark (and antiquark) constituents. The production cross sections of ψ(3770), arising from scattering of the D and D¯ mesons, are computed from the relativistic Breit-Wigner spectral function expressed in terms of the in-medium masses and the decay widths of the charmonium state. The effects of the magnetic field are considered due to the Dirac sea (DS) of the baryons, the mixing of the pseudoscalar (S=0) and vector (S=1) meson (PV mixing), the Landau level contributions for the charged hadrons. The anomalous magnetic moments (AMMs) of the baryons are also taken into account in the present study. For magnetized nuclear matter, at ρB=ρ0, the effect of Dirac sea leads to inverse magnetic catalysis (IMC), which is drop of the magnitude of the light quark condensates (proportional to the scalar fields) with increase in the magnetic field, contrary to the opposite effect of magnetic catalysis (MC) at ρB=0. The inclusion of hyperons to the nuclear medium is observed to lead to magnetic catalysis. There are observed to be significant effects from the DS and PV mixing on the properties of the charm mesons. The production cross sections of ψ(3770) arising due to scattering of D+D−(D0D¯0) mesons in the hot magnetized strange hadronic matter are observed to have distinct peak positions, when the magnetic field is large. This is because the production cross sections have contributions from the transverse as well as longitudinal components of ψ(3770), which have nondegenerate masses due to PV [ψ(3770)−ηc′] mixing. These can have observable consequences on the dilepton spectra as well as on the production of the charm mesons in ultrarelativistic peripheral heavy ion collision experiments, where the produced magnetic field is huge. Published by the American Physical Society 2024

Nuclear clustering-manifestations of non-uniformity in nuclei.

Well-developed [Formula: see text] clusters are known to exist in light [Formula: see text] nuclei, and their properties are reasonably well described with modern nuclear structure theories. However, 'modestly' developed clusters in medium to heavy nuclei remain little understood, both theoretically and experimentally. Extension of the focus to include modestly developed clusters leads us to a concept of 'generalized clusters' and 'cluster ubiquitousness'. The former includes clusters more weakly bound than an [Formula: see text] cluster, such as deuteron, triton and [Formula: see text], and even clusters partially broken owing to nuclear medium effects. The latter means the existence of clusters in any nuclei, where cluster development was not previously discussed. Effects of the tensor and the spin-orbit interactions on the coexistence of clusters with independent nucleons are discussed using recent nuclear theoretical models. A mixture of the clusters with shell-like components plays an essential role in the synthesis of elements in the universe and the origin of life, together with an [Formula: see text] decay. It is also pointed out that clustering in heavy nuclei may accelerate fission and fusion processes. Future experimental plans using cluster knockout reactions, which have the potential to extract information of 'generalized clusters' in a variety of nuclei including stable and unstable nuclei, are also discussed. This article is part of the theme issue 'The liminal position of Nuclear Physics: from hadrons to neutron stars'.

Modification of χc1(3872) and ψ(2S) Production in pPb Collisions at sNN=8.16 TeV

The LHCb Collaboration measures production of the exotic hadron χc1(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state ψ(2S) suggests that the exotic χc1(3872) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify χc1(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Understanding the Origins of Quark Charges, Quantum of Magnetic Flux, Planck’s Radiation Constant and Celestial Magnetic Moments with the 4G Model of Nuclear Charge

Introduction: In our previous published papers, considering 3 large atomic gravitational constants assumed to be associated with weak, strong and electromagnetic interactions, we have proposed the existence of a nuclear charge of magnitude, en=2.95e and developed a nuclear mass formula associated with strong and weak interactions having 4 simple terms and only one energy coefficient. Methods: Two important assumptions are that there exists a weak fermion of rest energy 585 GeV and a strong coupling constant is the squared ratio of electromagnetic charge and nuclear charge. The aim of this paper is associated with understanding the mystery of the quantum of magnetic flux, Planck’s quantum radiation constant and Reduced Planck’s constant. Proceeding further, quark charges, strong coupling constant, nuclear stability, nuclear binding energy, medium and heavy atomic X-ray levels and celestial magnetic moments can be understood in a unified approach. It may also be noted that, by considering the integral nature of elementary particle masses, it seems possible to understand the discreteness of angular momentum. Results: Considering our proposed en=2.95e=3e as a characteristic nuclear charge, it seems possible to understand the integral nature of quarks electromagnetic charge. With this idea, neutron, proton and pion decay can be understood very easily. Conclusion: In all the cases, the up quark of charge (±2e) seems to play a crucial role in the internal transformation of the down quark of charge (±e) and external observable elementary basic elementary particles. It needs further study at the fundamental level.

Medium-induced photon bremsstrahlung in neutrino-nucleus, antineutrino-nucleus, and electron-nucleus scattering from multiple QED interactions

Interactions of charged leptons with nuclei and the naive tree-level kinematics of these processes are affected by radiation of photons induced by the QED nuclear medium. We evaluate cross section modifications at leading orders of the number of correlated interactions inside the nucleus, known as the opacity expansion. We derive results for soft and collinear types of the bremsstrahlung at the first three orders in opacity and generalize them to higher orders. We present the leading in opacity energy spectra of soft and collinear photons and radiative energy loss inside the nucleus for experiments with lepton kinematics in the GeV energy range. At leading power of the Glauber soft-collinear effective field theory, the soft radiation is further resummed to all orders both in opacity and in the electromagnetic coupling constant. We find that the soft and collinear medium-induced radiation is vacuumlike, and additional corrections are power suppressed. Despite the negligible modification to the induced photon spectra, the nuclear medium-induced radiation sizably affects the broadening of charged leptons in the direction orthogonal to their propagation. Published by the American Physical Society 2024

A direct probe of Λ potential in nuclear medium

Using the Liège intranuclear-cascade model together with the ablation model ABLA, an investigation is conducted into the effects of Λ potential in Λ-nucleus and Λ-hypernucleus-nucleus collisions across various beam energies. The findings show that the angle and transverse-momentum distributions of scattered Λ hyperon, the scattering cross section of the Λ hyperon in Λ-nucleus collisions as well as the rapidity distribution of Λ hyperon in Λ-hypernucleus-nucleus collisions are significantly influenced by the strength of the Λ potential in these scattering reactions across various beam energies. These demonstrations, unhindered by the uncertainties of Λ and hypernuclei productions in nuclear medium, allow for a direct investigation of the Λ potential, especially its momentum dependence. The criticality of probing the Λ potential is closely associated with the resolution of the “hyperon puzzle” in neutron stars.

Charge-conjugation asymmetry and molecular content: The [formula omitted] in matter

We analyze the modifications that a dense nuclear medium induces in the Ds0⁎(2317)± and Ds1(2460)±. In the vacuum, we consider them as isoscalar D(⁎)K and ▪S-wave bound states, which are dynamically generated from effective interactions that lead to different Weinberg compositeness scenarios. Matter effects are incorporated through the two-meson loop functions, taking into account the self energies that the D(⁎), ▪, K, and ▪ develop when embedded in a nuclear medium. Although particle-antiparticle [Ds0,s1(⁎)(2317,2460)+versusDs0,s1(⁎)(2317,2460)−] lineshapes are the same in vacuum, we find extremely different density patterns in matter. This charge-conjugation asymmetry mainly stems from the very different kaon and antikaon interaction with the nucleons of the dense medium. We show that the in-medium lineshapes found for these resonances strongly depend on their D(⁎)K/▪ molecular content, and discuss how this novel feature can be used to better determine/constrain the inner structure of these exotic states.

Kaon structure in the nuclear medium within the light front approach

We study the properties of the charged kaon in symmetric nuclear matter using a Bethe-Salpeter amplitude to model the quark-antiquark bound state, which is well constrained by previous studies of its vacuum properties. The electromagnetic form factor, charge radius, decay constant, and the light-front valence component probability are investigated in symmetric nuclear matter. In order to describe the constituent up and antistrange quarks in nuclear matter, we adopt the “quark-meson coupling (QMC) model,” which has been widely applied to various hadronic and nuclear phenomena in the nuclear medium. Published by the American Physical Society 2024

Pore-space characterisation of Tamusu mudstone based on FIB-SEM

This study focuses on characterising the pore space in Tamusu mudstone, a preferred nuclear waste disposal host medium in China, using focused ion beam/scanning electron microscopy (FIB-SEM). The investigation is conducted at the mesoscale, with a sample volume of 7·96 × 9·16 × 10·00 μm3 and voxel sizes of 5 × 5 × 10 nm3. The findings reveal that the pores in Tamusu mudstone primarily exist at the nanoscale, typically within its mineral matrix or at interfaces with non-porous minerals. At the FIB/SEM-imaged scale, the pore space in the Tamusu mudstone is mainly unconnected, with an analysed porosity of approximately 3·5%. Pore characteristics within the specimen exhibit relative consistency within a box size of 6–8 μm. Furthermore, the pore paths in Tamusu mudstone exhibit a preferred orientation within the bedding plane, suggesting anisotropy in pore space, possibly attributed to changes in pore path orientation and tortuosity.

How macroscopic limits on neutron-star baryon loss yield microscopic limits on non-standard-model baryon decay

We investigate how our baryon-loss limits from anomalous binary-pulsar period lengthening can be interpreted microscopically to yield specific constraints on the particle physics of baryon number violation within a neutron star. We focus on the possibility of anomalous baryon disappearance via dark baryon processes and on scenarios in which the produced dark-sector particles do not survive to influence the response of the star to baryon-number-violating effects. We flesh out the conditions for which this may occur, as well as other key assumptions. We then turn to the analysis of particle processes in the dense nuclear medium found at the core of a neutron star, employing the techniques of relativistic mean-field theory. Using our study of in-medium effects and limits on macroscopic baryon number violation, we extract limits on in-vacuum baryon-number-violating processes, and we determine them for various equations of state. We conclude by noting the implications of our results for models of dark-sector-enabled baryogenesis. Published by the American Physical Society 2024

Bulk flow and correlation measurements at LHCb

Particle correlations are a powerful tool to study the properties of the bulk nuclear matter produced in relativistic heavy ion collisions. The momentum correlations between identical particles originating from the same particleemitting source, referred to as the Bose-Einstein correlations, measure scales that are related to the geometrical size of the source. The two-particle azimuthal angular correlations measure the spatial anisotropy of produced particles, providing information on collective phenomena arising in the dense nuclear medium. This contribution will discuss new LHCb measurements of Bose- Einstein correlations and, for the first time, the collective flow coefficients in the far forward rapidity region.

Measurement of in-medium modification of energy-space structure of jets via γ and π0 triggered hadrons in Au+Au collisions at RHIC

Since the discovery of the jet quenching at RHIC, the in-medium interaction of hard scattered partons with the nuclear medium created by highenergy heavy-ion collisions has been an excellent tool to understand not only the transport properties of the medium but also its time evolution towards hadronization. The multi-differential measurement of the high momentum twoparticle correlations can probe a particular space-time window as a function of energy transfer. Comparing the correlations with the prompt photon-triggered hadron spectra, one can extract the property of the medium from various aspects and contribute to distinct models. The PHENIX experiment at RHIC has collected its highest statistics of the γ and π0 triggered hadron events in Au+Au collisions at √SNN = 200 GeV in the RHIC Year-2014 run, and measured not only the inclusive spectra of the triggered hadrons but also the angle and energy dependent IAA and DAA. We will discuss the in-medium modification of the energy-space structure of the jets at the RHIC energies with the results obtained.

Properties of the Tcc(3875)+ and the Tcc (3875)− states in nuclear matter

Abstract. Since its first detection, the interesting properties of the Tcc(3875)+ have made it to be one of the most prominent tetraquark-like states up to date. In this work we present a joint analysis of the T+cc and its charge-conjugated partner in a dense nuclear medium. We start by considering both states as purely isoscalar D* D and D¯*D¯ S -wave bound states, respectively. We use previous results for the in-medium D, D¯*D¯, D* and D* spectral functions to determine the modified two-meson amplitudes. We find important changes in the in-medium mass and width of both tetraquark-like resonances, which become more visible when increasing the nuclear density and molecular probabilities. The experimental confirmation of the found distinctive patterns will support the existence of molecular components in the T+cc and T-c¯c¯ wave functions.

Phi meson in nuclear medium

I will report on the progress in theoretical studies of the ϕ meson mass shift in a nuclear medium and provide an overview of the current experimental status for observing such an effect. Additionally, I will discuss how the distinct momentum dependencies of the transverse and longitudinal modes can be experimentally distinguished, particularly through the e+e− and K+K− decay modes of the ϕ meson as it decays within the medium.

The Gerasimov-Drell-Hearn sum rule with nuclear targets

Hadron properties are modified when the hadron is embedded in a nuclear medium. Here we discuss the Gerasimov-Drell-Hearn, GDH, sum rule for polarised photoproduction from a polarised nucleon within a polarised nuclear target. Strong enhancement is expected with the suppression of the proton and nucleon resonance masses and enhancement of the proton’s anomalous magnetic moment in medium. This could be tested in polarised photoproduction experiments with interesting targets being polarised deuterons, ^3He, ^6Li and ^7Li. The largest contribution to the GDH sum rule comes from the Delta resonance excitation. In existing data with polarised deuterons and ^3He the Delta excitation is shifted to slightly lower energy when compared to model predictions where the Delta is treated with its free mass.