Welcome and Introduction

• Konrad Schmidt (Helmholtz-Zentrum Dresden-Rossendorf, Germany)

Room: online

Carpathian Summer School of Physics

• Livius Trache (IFIN-HH, Romania)

Room: online Introduction of the biannual Carpathian Summer School of Physics

Big-Bang Nucleosynthesis as a Probe of Fundamental Physics in the Early Universe

• Brian D. Fields (University of Illinois, USA)

Room: online Big-bang nucleosynthesis (BBN) is a quintessential example of how nuclear astrophysics can and does probe fundamental physics. BBN describes the production of the lightest elements during the first three minutes of cosmic time, and represents our earliest reliable probe of the universe. BBN has stood as a cornerstone of both modern cosmology and particle astrophysics, measuring the cosmic baryon content and probing physics beyond the Standard Model. We will review the status of BBN, emphasizing the transformative influence of cosmic microwave background experiments, particularly Planck, in precisely determining the cosmic baryon density, and the impact of recent nuclear reaction measurements. Standard BBN combines this with the Standard Model of particle physics to make tight predictions for the primordial light element abundances. Deuterium observations match these predictions spectacularly, helium observations are in good agreement, but lithium observations (in metal-poor halo stars) are significantly discrepant – this is the ”lithium problem”. Going beyond the Standard Model, BBN probes new physics at play when the universe was seconds old, deep into the radiation era, for example, placing tight limits on any light particles in equilibrium when the Universe was 1 second old. We conclude with a glimpse of prospects for the future.

Moderated questions

• Andreas Korn (Uppsala University, Sweden)

Room: online

Nuclear reactions for Standard Solar Models

• Aldo Serenelli (Institute of Space Science, Spain)

Room: online

Moderated questions

• Konrad Schmidt (Helmholtz-Zentrum Dresden-Rossendorf, Germany)

Room: online

Cross section measurement of the 3He(α,γ)7Be reaction with γ-spectroscopy

• Ákos Tóth (ATOMKI, Hungary)

Room: online The astrophysically important 3He(α,γ)7Be reaction plays role both in models of the Big Bang Nucleosynthesis (BBN) through the production of 7Li and in the p-p chain of solar hydrogen burning. In the case of the former event the Gamow energy of the reaction is around 0.2 MeV, while in the case of the p-p chain in the Sun, an order of magnitude less, around 0.023 MeV. Experimental investigation at such low energies is very difficult, if possible all, thus low energy extrapolation inevitable to predict the reaction rate at these energies. There are many precision datasets between Ec.m. = 0.3 – 3.1 MeV, but only two outside of this region, one below and one above. At higher energies known levels of 7Be exist, but those were investigated only in scattering experiments. No experimental radiative capture cross section data are available, which motivates the study of the reaction in that energy range. Therefore, we are performed irradiations, using the ATOMKI MGC-20 cyclotron type accelerator in the energy range of Ec.m. = 4.3 – 8.3 MeV. For the cross-section determination, the activation technique was used. A thin windowed gas cell filled up with 3He gas was used for the experiments, as a target. The reaction product 7Be has a half-life of 53.22 days. The number of collected radioactive 7Be reaction products was determined by gamma spectroscopy. A high purity germanium (HPGe) detector was utilised to measure the 477.6 keV gamma rays following 10.44% of the decays. The preliminary results will be presented.

Moderated questions

• Livius Trache (IFIN-HH, Romania)

Room: online

Underground measurement of the D(p,γ)3He reaction: nuclear and cosmological implications

• Nikhil Mozumdar (University of Padova, Italy)

Room: online The Big Bang Nucleosynthesis (BBN) encompasses the sequence of nuclear reactions in the early minutes of the Universe leading to the production of light nuclei. Among the light elements produced during BBN, deuterium is an excellent indicator of cosmological parameters because its abundance is highly sensitive to the primordial baryon density. Amidst all the reactions involving deuterium production or destruction, the deuterium burning reaction D(p,γ)3He has the largest uncertainty in its cross section which limits the theoretical predictions based on BBN. A recent work by the LUNA collaboration1, reports the cross sections for the D(p,γ)3He reaction in the energy range of 30 <Ecm < 260 keV with minimised uncertainties (<3%). This is based on an experiment carried out deep underground in order to exploit the reduced cosmic ray background at the Laboratory for Underground Nuclear Astrophysics (LUNA) of the Gran Sasso Laboratory (Italy). The experiment involved bombarding a high purity extended deuterium gas target with an intense proton beam from the LUNA 400-kV accelerator. The γ rays produced in the ensuing nuclear reaction were detected with the help of a High Purity germanium detector. These experimental results settles the most uncertain nuclear physics input to BBN calculations and substantially improves the reliability of using primordial abundances as probes of the physics of the early Universe. A systematic study of the angular distribution of this D(p,γ)3He reaction has also been performed on the same experimental data. The full energy peak, broadened due to the kinematics has been fit using Legendre polynomials Pℓ, considering ℓ = 0-3. Two separate methodologies have been adopted for the peak shape analysis. Finally, the coefficients obtained from the analysis are reported and compared to those predicted by theoretical ab-initio calculations. A very good agreement with the theoretical predictions is observed.

Moderated questions

• Livius Trache (IFIN-HH, Romania)

Room: online

Round table discussion

• Livius Trache (IFIN-HH, Romania)

Room: online Questions that were compiled in the chat during and after lectures and breakout session will be answered and discussed.