CyberSec Research

Neutron-transmission measurements through samples of magnesium fluoride (MgF$_2$) and pure magnesium were performed to obtain the (n, tot) cross section for all isotopes involved, $^{19}$F and $^{24-26}$Mg. Lithium-glass detectors were used in conjunction with the neutron time-of-flight technique. The measurement campaign was performed at the MONNET fast-neutron source of the European Commission Joint Research Centre (JRC-Geel, Belgium). Highly precise corrections for multiple scattering were calculated using a sophisticated iterative method based on Monte Carlo simulations with the MCNP6.3 code, accounting for the effects of the experimental setup. With the SAMMY code, an R-Matrix analysis of the experimental data was performed. The extracted cross-sections, resonance spin and parity as well as the limitations of the method are carefully discussed.

The isotopic ratios measured in meteoritic presolar grains are a crucial tool for tracing the nucleosynthetic origin of isotopes. In the case of silicon isotopes, two important indicators to establish the origin of presolar grains are the ratios 29Si/28Si and 30Si/28Si. To constrain theoretical predictions, the rates of key nuclear reactions influencing the abundances of 29Si and 30Si must be well known. One such reaction is 29Si(p,gamma)30P which plays a role in classical nova explosions. The aim of the present work is to determine the nonresonant cross section of the 29Si(p,gamma)30P reaction, which has not been previously measured. The activation method was employed to measure the total cross section at four proton energies between Ep = 1000 and 1430 keV. The measured cross sections were found to be significantly (a factor of 4.3+-0.6) higher than those predicted by theoretical direct capture calculations, thereby impacting the reaction rates at low astrophysical temperatures, below about 30 MK. This higher nonresonant cross section - now based on experimental data - can be used in forthcoming nucleosynthesis calculations of classical novae. As a secondary result, the 16O(p,gamma)17F cross section was also obtained and found to be in good agreement with existing literature data.

We present an overview of theoretical and phenomenological studies on the partonic structure of nuclei and small-$x$ QCD dynamics using photon-nucleus $(\gamma A$) scattering in heavy ion ultraperipheral collisions (UPCs). Focusing on nuclear shadowing, we review implications of coherent charmonium and inclusive dijet production in Pb-Pb UPCs at the LHC and discuss the potential of inelastic $\gamma A$ scattering accompanied by forward neutrons in a zero degree calorimeter (ZDC).

We report measurements of charmonium sequential suppression in $^{96}_{44}\rm{Ru}$+$^{96}_{44}\rm{Ru}$ and $^{96}_{40}\rm{Zr}$+$^{96}_{40}\rm{Zr}$ collisions at \sqrtsnn\ = 200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The inclusive yield ratio of $\psi$(2S) to J/$\psi$ as a function of transverse momentum is reported, along with the centrality dependence of the double ratio, defined as the $\psi$(2S) to J/$\psi$ ratio in heavy-ion collisions relative to that in $p$+$p$ collisions. In the 0-80\% centrality class, the double ratio is found to be 0.41 $\pm$ 0.10 (stat) $\pm$ 0.03 (syst) $\pm$ 0.02 (ref), lower than unity with a significance of 5.6 standard deviations. This provides experimental evidence that $\psi$(2S) is significantly more suppressed than J/$\psi$ in heavy-ion collisions at RHIC. It is also observed that this sequential suppression pattern is more pronounced at lower transverse momentum.

The ground-state properties and shape evolution of even-even hafnium isotopes ranging from $N=80$ to the neutron dripline are thoroughly examined using Covariant Density Functional Theory (CDFT) with density-dependent effective interactions, specifically the parameter sets DD-ME1, DD-ME2, DD-PC1, and DD-PCX. Key nuclear properties, including binding energies, two-neutron separation energies ($S_{2n}$), two-neutron shell gaps ($\delta S_{2n}$), neutron pairing energies ($E_{pair,n}$), quadrupole deformation parameters ($\beta_2$), root-mean-square (RMS) charge and matter radii, and neutron skin thickness ($\Delta r_{np}$), are systematically computed and compared with available experimental results and predictions from various theoretical models. These include the Hartree-Fock-Bogoliubov (HFB) framework employing the Skyrme SLy4 interaction, the Finite Range Droplet Model (FRDM), the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) using the PC-PK1 functional, and the relativistic mean-field (RMF) approach with NL3 parameterization. Shell closures at $N=82$ and $N=126$, subshell effects at $N=108$ and $N=152$, and shape transitions with coexistence in $^{192}$Hf and $^{222-236}$Hf are observed. Neutron skin thickness increases with neutron excess, and potential energy surfaces show consistent trends, validating CDFT's reliability for nuclear structure predictions.

The nature of dark energy remains one of the most important unanswered problems in physics. Here we use gamma-ray spectra from the Type Ia supernova 1991T to constrain the recent evolution of a dynamical pseudoscalar quintessence-like field $Q(t)$. We found that the 1991T gamma rays emitted by the $^{56}\text{Fe}$ nuclei observed by COMPTEL aboard the Compton Gamma Ray Observatory were slightly shifted to lower energies with respect to terrestrial values, with the average fractional energy shift of both the first and second excited states found to be $\delta E/E = -0.006\pm0.008$ including statistical and systematic errors. Assuming that this energy shift is caused by a dynamical QCD axion-like pseudoscalar field $Q(t)$, we find that observed energy deviations are consistent with a fractional rate of change of the pion mass given by $\delta \dot{m_{\pi}}/m_{\pi}=-(6\pm9)\times10^{-11}\text{ yr}^{-1}$. The observed energy deviation was also used to determine the rate of change of the quintessence-like field ($\dot{Q}_0$) for tracking models: $\dot{Q}_{0,max} = (3\pm 4)\times10^7 \text{ GeV/yr}$. Our findings are consistent with the cosmological constant ($\dot{Q}_0 =0$). Furthermore, we have demonstrated how nuclear spectra produced by astrophysical events can be used to inform the nature and behavior of dark energy.

The anisotropic flow coefficients $v_n$ quantify the collective medium response to the initial spatial anisotropy of the overlapping region in ion collisions and serve as sensitive probes of both the medium properties and shape of nuclear initial states. In this analysis, the $v_2$ and $v_3$ parameters of prompt charged particles are measured using the multiparticle cumulant method in fixed-target PbNe and PbAr collisions at $\sqrt{s_{NN}} = 70.9$ GeV, collected by LHCb using the SMOG2 gas-target system during the 2024 LHC lead-beam run. The cumulant method is first validated using 2018 PbPb collision data, successfully reproducing previous measurements obtained via the two-particle correlation method. Results for the fixed-target collisions are then presented, showing a significantly larger value of the elliptic flow coefficient $v_2$ in central PbNe with respect to PbAr collisions. This is qualitatively consistent with 3+1D hydrodynamic predictions including ab-initio descriptions of the nuclear structure. The results provide the first experimental confirmation of the distinctive bowling-pin shape of the ground-state $^{20}$Ne nucleus, validating at the same time the hydrodynamic description of the hot medium formed in high-energy collisions involving light ions.

Nuclear physics is a very abstract field with little accessibility for wider audiences, and yet it is a field of physics with far reaching implications for everyday life. The Nuclear Beavers demonstration is a hands-on experience that offers an intuitive lens into nuclear structure and decay. We aim to provide a more accessible entry point for students and educators by substituting complex nuclear structures and interactions with tactile building blocks following well-defined rules, thereby opening nuclear physics concepts to the general public.

In an ultra-peripheral collision, a photon can interact with a gluon in the target nucleus and produce a pair of charm quarks, while the target nucleus breaks up (inelastic scattering). These charm quarks then fragment and are observed as open charm hadrons or vector mesons. This process has been used in e$\unicode{x2014}$p collisions to set stringent limits on the proton gluon distribution at low-$x$. The current measurements can provide similar constraints on the much less known nuclear gluon distributions. ALICE has measured the transverse momentum distribution of inelastically photoproduced $\text{D}^0$ at midrapidity, in Pb$\unicode{x2014}$Pb collisions at $\sqrt{s_\text{NN}}$=5.36 TeV. The distribution is measured down to $p_\text{T}$=0 for the first time. The results are compared to model calculations.

I show a way to tune photo-nuclear cross section effectively and therefore achieve nuclear transitions "on demand". The method is based on combinatorial enhancement of multiphoton processes under intense conditions. Taking advantage of recent advances in high-power laser systems (HPLS) and nuclear structure calculations, efficient control of nuclear transitions up to E4 in multipolarity can be reached today. The same idea can be extended to the search for rare transitions and hidden states, which applies to the $\gamma$-beams generated from conventional sources as well.

We report on a high-precision measurement of the D($\gamma$, $n$)$p$ photodisintegration reaction at the newly commissioned Shanghai Laser Electron Gamma Source (SLEGS), employing a quasi-monochromatic $\gamma$-ray beam from Laser Compton Scattering. The cross sections were determined over $E_\gamma$=2.327-7.089 MeV, achieving up to a factor of 2.2 improvement in precision near the neutron separation threshold. Combined with previous data in a global Markov chain Monte Carlo (MCMC) analysis using dibaryon effective field theory, we obtained the unprecedentedly precise $p$($n$, $\gamma$)D cross sections and thermonuclear rate, with a precision up to 3.8 times higher than previous evaluations. Implemented in a standard Big-Bang Nucleosynthesis (BBN) framework, this new rate decreases uncertainty of the key cosmological parameter of baryon density $\Omega_b h^2$ by up to $\approx$16% relative to the LUNA result. A residual $\approx$1.2$\sigma$ tension between $\Omega_b h^2$ constrained from primordial D/H observations and CMB measurements persists, highlighting the need for improved $dd$ reaction rates and offering potential hints of new physics beyond the standard model of cosmology.

By extending our analysis and simulations of our $^{37}$K $\beta$-decay data set to allow the $\beta$ asymmetry with respect to nuclear spin to vary with $\beta$ energy $E_{\beta}$, we have gained sensitivity to new physics that depends on a helicity factor for the $\beta$, $m_\beta/E_\beta$. In particular, we constrain Lorentz scalar and tensor quark-lepton interaction strengths at a sensitivity complementary to the similar Fierz interference term in neutron $\beta$ decay. Our result for that new physics is $b_F$ = -0.0002 $\pm$ 0.024 (stat) $\pm$ 0.039 (syst), consistent with the standard model electroweak interaction value $b_F=0$. We consider presently achieved complementarity to $\beta$-decay and particle physics experiments, along with projectable technical improvements to our method.

sPHENIX is a next-generation experiment at RHIC for jet and heavy-flavor physics which was fully commissioned during 2023 and 2024. Using its novel streaming-readout-capable, precision tracking system, sPHENIX collected 100 billion unbiased $p$$+$$p$ collisions, and a further sample of minimum-bias Au-Au collisions, in Run-24. A key measurement of the sPHENIX heavy flavor physics program is the comparison of $\Lambda_c^+$ to $D^0$ differential yields in both Au+Au and $p$$+$$p$ collisions, which probes questions related to the hadronization of heavy-flavor baryons compared to mesons in the Quark-Gluon Plasma medium and in vacuum. At RHIC energies, there is no previous measurement of the $\Lambda_c^+/D^0$ baseline in $p$$+$$p$ collisions, modern Monte Carlo event generators give widely different predictions, and the ratio in Au+Au is only poorly known. These proceedings present the status of measurement from sPHENIX of the $\Lambda_c^+/D^0$ ratio in $p$$+$$p$ collisions.

The higher-twist (HT) formalism is used at $O(\alpha^2_s)$ to compute all possible medium-induced single emission scattering kernels for an incoming highly virtual and energetic quark traversing the nuclear environment. The effects of the heavy-quark mass scale are taken into account [Phys. Rev. C 94, 054902 (2016)] both in the initial state as well as in the final state, along with interactions involving both in-medium Glauber gluons and quarks [Nucl. Phys. A 793, 128 (2007)], as well as coherence effects [Phys. Rev. C 105, 024908 (2022)]. As this study is a continuation of our work on medium-induced photon production [Phys. Rev. C 112, 025204 (2025)], the general factorization procedure for $e$-$A$ deep-inelastic scattering is still used. An incoming quark energy loss in the nuclear medium yields four possible scattering kernels $\it{K}_i$ with the following final states: (i) $q+g$, (ii) $\it{g}+\it{g}$, (iii) $q+\bar{q}'$, where the quark $q$ may have a flavor different from the antiquark $\bar{q}'$, and (iv) $q+q'$, where, again, $q$ may have a flavor different from $q'$. The collisional kernels include full phase factors from all non-vanishing diagrams and complete first-order derivative in the longitudinal direction ($k^-$) as well as second-order derivative in the transverse momentum ($k_{\perp}$) gradient expansion. Furthermore, in-medium parton distribution functions and the related jet transport coefficients have a hard transverse-momentum dependence (of the emitted quark or gluon) present within the phase factor.

The $^{93}$Nb($t$,$^{3}$He) reaction at 115 MeV/u was studied to demonstrate that nuclear level densities and $\gamma$-ray strength functions can be extracted from charge-exchange reactions at intermediate energies using the Oslo technique. The matrix of excitation energy in $^{93}$Zr, reconstructed from the ($t$,$^{3}$He) reaction, versus the energy of $\gamma$ rays emitted by the excited $^{93}$Zr nuclei, was obtained in an experiment with the S800 Spectrograph operated in coincidence with the GRETINA $\gamma$-ray detector. The extracted level density and $\gamma$-ray strength function obtained by applying the Oslo method to this matrix were used to estimate the $^{92}$Zr($n$,$\gamma$)$^{93}$Zr cross section by combining the new results with other experimental data and theoretical calculations for $E$1 and $M$1 strength functions at higher energies. Good agreement with direct measurements of the $^{92}$Zr($n$,$\gamma$)$^{93}$Zr cross section was found. The contribution from the upbend in the extracted $\gamma$-ray strength function was important to achieve the consistency as the neutron-capture cross section without this contribution is significantly below the direct measurements otherwise. Since charge-exchange reactions at intermediate energies have long been used for extracting Gamow-Teller strengths, the successful demonstration of the charge-exchange Oslo method enables experiments in which ($n$,$\gamma$) cross sections and Gamow-Teller strengths can be measured simultaneously, which is of benefit for astrophysical studies.

The progress of the study of unstable states in relativistic dissociation events of light nuclei in nuclear emulsion is presented. Identification of these states is possible by means of the invariant mass determined from the most accurate and complete measurements of relativistic fragment emission angles in the approximation of conservation of momentum per nucleon of the parent nucleus. It is established that excitations $^{12}\mathrm{C}(0^{+}_{2})$ and $^{12}\mathrm{C}(3^{-})$ lead in the dissociation $^{12}\mathrm{C} \rightarrow 3\alpha$ and $^{16}\mathrm{O} \rightarrow 4\alpha$. The contribution of $^{9}\mathrm{B}$ and $^{12}\mathrm{C}(0^{+}_{2})$ decays to the leading channel of $^{3}\mathrm{HeH}$ dissociation of the $^{14}\mathrm{N}$ nucleus is estimated. The motivation and the beginning of the analysis of the relativistic dissociation $^{16}\mathrm{O}$$\rightarrow$$^{12}\mathrm{C}\alpha$ are presented. The presented relativistic dissociation events at the $^{7}\mathrm{Be}$$\rightarrow$$^{6}\mathrm{Li}p$ and $^{11}\mathrm{C}$$\rightarrow$$ ^{7}\mathrm{Be}\alpha$ coupling threshold point to the prospect of moving beyond $\alpha$-particle clustering.

In this contribution we review the algebraic cluster model (ACM) for $\alpha$-cluster nuclei with $A=4k$ nucleons and its extension to the cluster shell model (CSM) for $A=4k+x$ nuclei. Particular attention is paid to the question to what extent the $\alpha$-cluster structure survives under the addition of extra nucleons. As an example, we discuss the properties of $^{12}$C and $^{13}$C.

The nature of octupole deformation, whether static or vibrational, remains an open question in nuclear physics. Here, we propose a scaling approach to probe this ambiguity by triangular flow fluctuations using multi-particle cumulants, $c_{3,\varepsilon}\{4\}$, in relativistic $^{238}$U+$^{238}$U collisions. We demonstrate that both $|c_{3,\varepsilon}\{4\}|$ and the ratio $|c_{3,\varepsilon}\{4\}/c^2_{3,\varepsilon}\{2\}|$ scale linearly with the fourth-order moment of octupole deformation, $\langle \beta^4_{3,\mathrm{U}} \rangle$. Combined with the known linear relation of $c_{3,\varepsilon}\{2\}$ to $\langle \beta^2_{3,\mathrm{U}} \rangle$, this new relation provides a direct extraction of both the mean and variance of the octupole deformation fluctuations, finally discriminating between static and dynamic origins. This work establishes a new tool to probe the static and dynamic collective modes in high-energy nuclear collisions, advancing a significant step toward refining the initial conditions of quark-gluon plasma.