[en] The Big Bang Nucleosynthesis (BBN) theory has been very successful in predicting the observed abundances of light elements like ²H, ^3,4He. There is, however, a serious discrepancy of a factor of about four in the observed abundance of ⁷Li as compared to that predicted by the BBN theory. The high precision measurement of the baryon to photon ratio η by the Wilkinson Microwave Anisotropy Probe (WMAP) and recent observations of metal poor halo stars shows that the ⁷Li abundance predicted by the BBN theory is about 5.12 × 10¹⁰, whereas the observed value is about 1.23 × 10¹⁰. This anomaly has been unsolved for decades and is well known. Several avenues have been searched for a solution, of which the resonance excitations in reactions with ⁷Be appear to be very attractive

[en] An experiment is carried out involving a 5 MeV/A ⁷Be beam on a CD₂ target to study resonance excitations, at the HIE-ISOLDE facility of CERN, Geneva. Presented in this work is the simulations of the ⁷Be + d experiment with NPTool (Nuclear Physics Tool). NPTool is an open source, freely distributed package for Monte Carlo simulation and data analysis of nuclear physics experiments. It offers a unified framework for designing, preparing and analyzing complex experiments employing multiple detectors using GEANT4 and CERN ROOT toolkits. It has been successfully used in accelerator based experiments worldwide with both stable and radioactive beams. Monte Carlo simulations Detailed Monte Carlo simulations are essential to successfully carry out a nuclear physics experiment

[en] The rate of the radiative capture reaction ¹²C(α, γ)¹⁶O is a key input to the determination of the abundance ratio of C to O in the stars after helium-burning cycle. The formation of elements heavier than oxygen and the course of evolution of a star is crucially dependent on the above mentioned abundance ratio. Hence, the quest for precise measurement of this “holy grail of nuclear astrophysics” is now going on for more than five decades. There have been several attempts to investigate the reaction by direct method, but the extremely low cross section ∼ 10⁻¹⁷ barn at 300 keV renders it impossible to measure with the present technology. In this situation, the indirect asymptotic normalization constant (ANC) method serves as an accurate tool for this investigation. Reactions with ⁷Be show no threshold anomaly and it has a weak breakup coupling at low energies. Therefore, the ⁷Be nucleus is a suitable candidate for such studies. the elastic and transfer reaction studies were carried out for ⁷Be + ¹²C at 35 MeV. A reliable set of OMPs were obtained from the elastic scattering data over a wide angular range. These parameters are indispensable for the analysis of the transfer reaction data. The ⁷Be breakup cross section is estimated to be less than 10% of the reaction cross section. Further work on the transfer data is in progress to determine the ANC of the relevant states of ¹⁶O in the context of the ¹²C(α,γ)¹⁶O radiative capture reaction

[en] The cosmological lithium problem is a widely studied and yet unsolved problem in nuclear astrophysics. The problem delineates a serious discrepancy between the observed abundance of ⁷Li and that predicted by the Big Bang Nucleosynthesis (BBN) theory. The BBN calculations rely on nuclear physics inputs. So it is natural to study in details the nuclear reactions pertinent to the abundance anomaly of ⁷Li. Sensitivity studies involving the ⁷Be(d,p)⁸Be(2α) (Q_gs = 16:67 MeV) reaction has shown that the primordial lithium problem can be resolved if the reaction rate is a factor of 100 larger at the relevant Gamow energies. Recent experiments studying the destruction of ⁷Be with deuterons could not and any significant enhancement in the reaction rate to resolve the anomaly. However, these experiments did not measure the contributions of high lying excitations above 11.35 MeV in ⁸Be, in particular the 16.6 MeV state. The ground state (0⁺), 3.03 MeV (2⁺) and 11.35 MeV (4⁺) states were identified from the background subtracted excitation energy spectrum of ⁸Be as well as the energy vs scattering angle plot of protons detected at the BB7 DSSDs. The excitation energy spectrum is shown in the article. Work on the angular distribution of the excited states is in progress

[en] The α-cluster transfer reaction studies involving loosely bound stable and unstable nuclei have a profound impact on astrophysics. In particular, the reactions with ^6,7Li have been widely used to get spectroscopic factors and reduced α-widths. These quantities in turn have been successfully utilized in the understanding of stellar nucleosynthesis. In the present work, α-transfer reaction with the radioactive nucleus ⁷Be on ¹²C at 5 MeV/A has been studied

[en] Proton scattering of exotic unstable nuclei in inverse kinematics is widely used to study such nuclei . A systematic p- scattering study of a loosely bound stable nucleus and its radioactive mirror counterpart throws light on the reaction dynamics as we move towards the driplines. The elastic scattering is known to be affected by the coupling to reaction channels, which usually results in an enhancement of the total reaction cross section. Several works with the stable weakly bound ^6,7Li nuclei at near barrier energies have been carried out in this regard . We investigate ⁷Be, the radioactive mirror nucleus of ⁷Li, at similar energies (E_cm = 4:4 MeV). In addition, the ⁷Be + p elastic data will be useful in the study of the ⁷Be(d,p)⁸Be transfer reaction. In this work, we highlight the results of our experiment at the HIE-ISOLDE facility in CERN to study the proton scattering of ⁷Be in inverse kinematics

[en] The α-cluster transfer reactions have earlier been used as a potential tool to study the reactions in the helium burning phase of stars. The direct capture reactions with extremely small cross sections at low energies are difficult to measure in the laboratory. Hence, an indirect technique to study α-capture reactions is useful. This involves investigation of α-cluster transfer reactions to populate the relevant states in the residual nuclei. The technique has been extensively used on stable nuclei to investigate the astrophysical α-capture reactions. The loosely bound Lithium isotopes ⁶Li and ⁷Li are widely studied in this regard due to their α-cluster structure. Amro et al. carried out similar study on the radioactive mirror counterpart ⁷Be. However, the uncertainty in the optical model parameters (OMP) due to the limited angular distribution presented a serious problem in the study of transfer reactions. The study shows that α-cluster transfer reaction is more probable than breakup of ⁷Be. This low breakup yield makes the ⁷Be nucleus an excellent candidate for the study of high-excitation α-cluster states in the residual nuclei. We studied the α-cluster transfer reactions of ⁷Be to populate the states of ¹⁶O that dominantly contribute to the al- pha capture reaction ¹²C(α; γ)¹⁶O in helium-burning process in nuclear astrophysics

[en] The anomaly in the ⁷Li abundance, from observations and big-bang nucleosynthesis (BBN) theory is a well known unresolved problem in nuclear astrophysics, popularly known as the cosmological lithium problem. In this context, the ⁷Be(d,³He)⁶Li reaction not only produces ⁶Li but also destroys ⁷Be. Hence it may impact both the lithium anomalies. Till date there is only a single experiment measuring this reaction at E_cm = 4.0 and 6.7 MeV. However the authors relied only on Monte Carlo simulation gates to select the reaction products ³He and ⁶Li. No kinematical signatures were shown to verify that the selected ³He and ⁶Li are indeed from the above reaction. Thus, detailed experimental investigation of the ⁷Be(d,³He)⁶Li reaction is required

[en] The study on the modifications of single particle orbitals away from the line of stability draws significant attention. In particular, there is a well known level inversion of 0d_5/2 and 1s_1/2 in case of ¹⁵C. Primarily, the neutron-rich nuclei of A = 15 isobars were studied, as compared to the proton-rich counterparts. The present work focuses on the proton-rich nucleus ¹⁵O. It is a radioactive nucleus with a half life of ∼ ¹²²s and forms the core of the borromean nucleus ¹⁷Ne. The present study involves the ¹²C(⁷Be,α) ¹⁵O transfer reaction, using a ⁷Be radioactive beam. The ⁷Be nucleus has a α−³He cluster structure and is expected to have significant transfer and breakup channels

[en] Elastic scattering is widely used in the study of change in properties of nuclei as we move towards the drip lines. The breakup and transfer reactions significantly alter the elastic scattering when the nucleus involved is loosely bound and has cluster structure. The loosely bound stable Lithium isotopes ⁶Li and ⁷Li, have cluster structures and their breakup channels have been extensively studied. The present work reports the measurement of elastic and inelastic scattering of ⁷Be on ¹²C using a detector array covering a wide angular range