Abstract: The Cosmological Lithium Problem (CLP) is a well-known issue in astrophysics. It refers to an overestimation of the primordial 7Li abundance in the standard Big Bang nucleosynthesis (BBN) model predictions relative to astrophysical observations. Our research focuses on experimental nuclear physics to address the CLP. In particular, we aim to constrain the reaction rate of the 7Be(d, p)8Be reaction by measuring its cross section. The majority of 7Li nuclei were produced by the electron capture decay (T1/2= 53.22 days = 4.6 × 106 seconds) of 7Be. 7Be nuclei were produced in several hundred seconds during the BBN, leading to a timescale difference of more than 104 between the production time of 7Li and 7Be. This significant timescale difference implies that if more 7Be nuclei were destroyed during the BBN, it could result in a lower abundance of 7Li, potentially resolving the discrepancy.

Our study focuses on the 7Be(d, p)8Be reaction based on a theoretical suggestion that this reaction played a significant role in the destruction of 7Be nuclei during the BBN [1]. The measurement of the absolute cross section in the Big Bang energy region (Ec.m.=0.1−0.4 MeV) was crucial for understanding the nuclear reactions in the primordial universe. We produced a radioactive 7Be target and measured the 7Be(d, p)8Be reaction cross section at the tandem facility of Kobe University in Japan. A distinctive feature of this experiment was the production of an unstable nucleus 7Be as a target. The thick-target analysis method was applied to determine the cross sections. The cross section at the lowest energy of Ec.m.=0.12 MeV was measured with the highest sensitivity compared to the available data [2, 3, 4]. We confirmed that the measured 7Be(d, p)8Be cross sections have a limited impact on resolving the CLP.

This talk will outline the key details and discuss future perspectives, including a new project aimed at addressing the CLP.

References

[1] S. Q. Hou et al., Phys. Rev. C 91, 055802 (2015).

[2] R. Kavanagh, Nucl. Phys. 18, 492-501 (1960).

[3] C. Angulo et al., ApJ 630, L105 (2005).

[4] N. Rijal et al., PRL 122, 182701 (2019).

Abstract: The background of the formulation of the Simple Effective Interaction (SEI) is discussed. The systematics of its parameter fixation protocol is outlined that could account for the divergent trends on the density and momentum dependence of the isovector part of the nucleonic mean field predictions by different model calculations. 

The r-mode oscillation as a possible mechanism for the spin-down feature of newborn neutron stars is discussed. The ability of the bulk viscosity due to direct Urca processes in dissipating the large oscillations produced in the merger remnant in the event of two neutron star merger is examined where the equation of state of hot neutron star matter of neutron-proton-electron-muon composition is built upon it’s zero-temperature predictions.  

The predictions of SEI in different areas of finite nuclei properties is discussed. The correlation between the finite nuclei properties and the constraints resulting from neutron star phenomenology is examined using the charge radii differences in mirror nuclei pairs as observable.

Abstract: The progress in realising ultracold atomic mixtures has greatly revitalised the interest in studying impurities immersed in quantum mediums [1]. Following these developments, and motivated by the possibility of trapping ultracold atoms in optical lattices [2], the theoretical study of impurities in lattice configurations has emerged as a new platform for studying polaron physics. In this direction, recent studies of impurities interacting with bosonic baths have revealed intriguing features across the superfluid-to-Mott insulator transition [3,4].

In this talk  I will first present a numerical study of an impurity interacting with a bosonic bath and immersed in a harmonically confined optical lattice [5]. We reveal that the impurity can form a correlated counterflow state with the bath. This counterflow state [6] shows long-range anti-pair order and displays non-trivial features, including a sudden orthogonality. Then, I will briefly present a related study of an impurity interacting with a spin-1/2 fermonic bath in small lattices, where we show

[1] F. Grusdt, N. Mostaan, E. Demler and L. A. Peña Ardila, Rep. Prog. Phys. 88, 066401 (2025).

[2] I. Bloch, Nat. Phys. 1, 23 (2005).

[3] V. E. Colussi, F. Caleffi, C. Menotti, and A. Recati, Phys. Rev. Lett. 130, 17, 3002  (2023).

[4] R. Alhyder, V. E. Colussi, M. Čufar, J. Brand, A. Recati, G. M. Bruun, SciPost Phys. 19, 002 (2025).

[5] F. Isaule, A. Rojo-Francàs, L. Morales-Molina, and B. Juliá-Díaz, Phys. Rev. Lett. 135, 023404 (2025).

[6] A. B. Kuklov and B. V. Svistunov, Phys. Rev. Lett. 90, 100401 (2003).

Abstract: Since the prediction of the meson in 1935, facilities and institutions across the world have contributed to the discovery of over 200 distinct types, some of those being the well-known pions, kaons and J/Ψ. Understanding the properties of the mesons, including their spin, lifetime and mass, allows for the classification of this vast family of hadrons to be improved. This is particularly important in the case of the discovery of new or exotic mesons. In this endeavour, determining the spin is vitally important. A set of quantities known as moments of angular distributions relate the spin of a meson to the angular distributions of its decay products; furthermore, these quantities can be extracted unambiguously and directly from experimental data. The Thomas Jefferson National Accelerator Facility, also known as Jefferson Lab, located in Virginia, is home to the Continuous Electron Beam Accelerator Facility (CEBAF), which is capable of producing a high-luminosity 12 GeV electron beam. When this beam impinges on a supercooled liquid hydrogen target, electron-proton interactions result in the production of various mesons, which are then detected by the CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12). The purpose of this research is to use CLAS12 at Jefferson Lab to obtain the moments of angular distributions of mesons that decay into pairs of oppositely charged kaons.