About this video
This colloquium was hosted on behalf of the IOP Nuclear Physics Group by The University of Edinburgh
Prof. Brian Fields (U. Illinois, US) - 40 min
Big-Bang Nucleosynthesis in Light of New Nuclear Experiments
We will summarize the status of big-bang nucleosynthesis (BBN), which describes the production of the lightest nuclides during the first three minutes of cosmic time. We will emphasize the transformational influence of cosmic microwave background (CMB) experiments culminating today with Planck, which pin down the cosmic baryon density to exquisite precision. Standard BBN combines this with the Standard Model of particle physics, and with nuclear cross section measurements--notably recent precision measurements of d(p,g)3He by the LUNA collaboration. These allow BBN to make tight predictions for the primordial light element abundances, with the result that deuterium observations agree spectacularly with these predictions, and helium observations are in good agreement. This CMB/BBN concordance marks a great success of the hot big bang, and BBN and the CMB together now sharply probe cosmology, neutrino physics, and dark matter physics at times around 1 second. But this success is tempered by lithium observations (in metal-poor halo stars) that are significantly discrepant with BBN+CMB predictions. We will summarize possible solutions to this "lithium problem" that could point to new stellar astrophysics, new nuclear physics, or new particle physics. We conclude with an outlook for how future CMB, astronomical, and laboratory measurements can better probe new physics, and shed light on these possible solutions to the lithium problem.
Dr. Francesca Cavanna (INFN/U. Turin, Italy) - 20 min
Probing the early Universe from deep underground
Light elements were produced in the first few minutes of the Universe through a sequence of nuclear reactions known as Big Bang nucleosynthesis (BBN). 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. Although astronomical observations of primordial deuterium abundance have reached percent accuracy, theoretical predictions based on BBN were hampered by large uncertainties on the cross-section of the deuterium burning D(p,g)3He reaction, before the LUNA measurement.
I will report on a new measurement of the D(p,g)3He cross section performed by the LUNA collaboration to an unprecedented precision of better than 3%. This result 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.
Mr. Jordan Marsh (U. Edinburgh) - 15 min
Measurement of the d(p,g)3He reaction using CARME
The d(p,g)3He reaction plays a key role in the destruction of deuterium during big bang nucleosynthesis (BBN). The uncertainty on the cross section of the reaction has previously placed a limit on the precision of theoretical BBN calculations, with high precision measurements of the d(p,g)3He reaction required to further constrain BBN models. Recent measurements of the reaction in LUNA have significantly reduced the uncertainty on the cross section however disagreement between datasets outside of uncertainties exists and the angular distribution remains
relatively unknown. The CRYRING Array for Reaction MEasurements (CARME) offers a novel method for nuclear reaction measurements utilising the CRYRING storage ring. Measurements using CARME will produce a comprehensive high precision dataset of the d(p,g)3He reaction with high angular resolution for angular distribution measurements.
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