Course 7: Origin of the Elements (2014)

A three-week TALENT course on the Origin of the Elements was held at Michigan State University, starting May 28 and ending June 13 2014. All course material, slides, codes, exercises, etc. are here.

Motivation and background

Progress on this topic can only be made when the expertise of several fields is combined: nuclear theory, nuclear experiment, astronomy, astrophysics and neutrino physics. The focus was on three specific interconnected topics of current interest in element synthesis, core collapse supernovae, r-process nucleosynthesis and neutrino physics. The lectures providee students with the tools necessary to perform calculations, and to put these calculations into context. The detailed course information can be found at https://wikihost.nscl.msu.edu/talent/doku.php

The course was sponsored by Michigan State University and the National Superconducting Cyclotron Laboratory www.nscl.msu.edu and JINA, the Joint Institute for Nuclear Astrophysics www.jinaweb.org, a National Science Foundation Physics Frontiers Center, which aims at advancing science at the intersection of nuclear physics and astrophysics by research, synergistic activities, and training of young researchers.

Overview, format and objectives

Format: The course was held from May 28 to June 13 in 2014 at Michigan State University, East Lansing, Michigan, USA and was organized in collaboration with the Joint Institute for Nuclear Astrophysics (JINA). A series of thirty hours of lecture and forty-five hours of “lab” work were given. The course drew from the JINA experience with practical activities during schools and carefully designed the exercises together with the lecturers to foster student engagement, maximize learning, and to create lasting value for the students, and for the TALENT series and the community by making lectures and other teaching material publicly available.

We envisioned the following features for the practical exercises:

We will use group work to carry out tasks that are very specific in technical instructions, but leave freedom for creativity.
Groups will be carefully put together to maximize diversity of backgrounds
Interdependence among group members will be created through formally distributing responsibilities for various technical aspects such as running and editing code, managing input, and visualizing output.
Results will be presented in a conference like setting to create accountability
We will organize events where groups exchange their experiences, difficulties, and successes to foster interaction among groups. This will include events for all participants as well as events grouped by responsibilities (for example, all responsible for output visualization meet and exchange ideas, code, etc)
Training is key for successful practical work. We will setup a pre-school online training module that will include instructions on downloading code etc. Participants will be required to do this training prior to arrival. During the school, on-line and lecture based training tailored to technical issues will be provided, in part directed to the specific responsibilities. In addition we will work with lecturers to align lectures with the practical exercises.
During group work lecturers and other experts will be available to interact with groups as needed. Interactions may range from help with technical problems, over answering physics questions, to ad-hoc “mini-lectures” on an interesting topic.
Each group will maintain an online logbook of their activities and results.
Training modules, codes, lectures, practical exercise instructions, online logbooks, and instructions and information created by participants will be merged into a comprehensive website that will be available to the community and the public for self-guided training or for use in various educational settings (for example, a graduate course at a university could assign some of the projects as homework or extra credit project, etc etc).

Motivation: Element synthesis has several aspects. Successful modeling of an astrophysical environment is crucial to determining the outcome of a nucleosynthetic process. Astronomical observation as well as nuclear and weak reactions are also key ingredients. Topics of core collapse supernovae, the r-process, and neutrinos illustrate these points.

Core collapse supernovae Hydrodynamics and thermodynamics are an important part of understanding nucleosynthesis in any environment. Unless one understands the temperature and density of the material undergoing element synthesis at each point, it is difficult to reliably determine reaction rates and therefore final element abundances. Since the mechanism of core collapse supernovae explosion is an important problem in low energy nuclear theory with many aspects, we will undertake a detailed investigation of this environment. Great strides have been made in the last few years with the advent of reliable 2D calculations and initial 3D calculations. Considerable effort is being focused on this problem and much more development is expected in the next few years. Solution of the supernova problem will reduce major uncertainties in the basic underlying conditions that affect nucleosynthesis as well as supernovae neutrino physics.

R-process nucleosynthesis The r-process, or a rapid neutron capture process, is a type of element synthesis in which neutrons are captured on a time scale that is quick relative to the beta decays of nuclei near stability. Thus nuclei are formed away from stability and decay back to stability as neutrons become exhausted. The astrophysical origin of the r-process elements is an important unsolved problem in nuclear astrophysics with core collapse supernovae and neutron star mergers as the two primary contenders. Considerable progress will be made in the next years with the coming of radioactive beam experiments and associated developments in theory. For the first time it will be possible to measure properties of nuclei that participate in the end of the r-process, called “freeze-out”. When combined with theory, this will provide constraints on the environment.

Neutrinos Neutrinos are an important part of understanding nucleosynthesis in a number of environments. Once an environment is hot enough to undergo a primary nucleosynthesis process (one that starts with free nucleons) it is often hot enough to produce enormous numbers of neutrinos. These neutrinos play a pivotal role in determining energetics of the environment and in some cases they also set the relative numbers of neutrons and protons. Both of these functions have a strong impact on the resulting element synthesis. Thus, the areas of neutrino physics and element synthesis are intertwined. The field of neutrino physics has had a number of exciting developments over the last decade. Beginning with the understanding that neutrinos oscillate, many of the fundamental parameters that determine the oscillation have been measured. Most recently, the third mixing angle was measured at Daya Bay. However, to understand neutrinos in astrophysical setting where many other neutrinos also exist is a daunting theoretical task. Much progress has been made in the last few years, but more is necessary in order to truly understand how neutrinos oscillate in environments like core collapse supernovae or the disks that form from compact object mergers.

Course objectives: At the end of the course students should be able to:

Read and interpret abundance plots created by both observers and theorists
Understand and be able to communicate the main ideas in various types of nucleosynthetic environments (big bang, supernovae, novae, x-ray bursts, etc.)
Understand and be able to describe the major components of a core collapse supernova calculation
Effectively use a hydrodynamic code to simulate a supernova-like explosion
Explore the impact of choices in gridding and resolution in a hydrodynamic simulation
Understand and be able to communicate the main ideas in r-process research
Use a pre-exisiting reaction network to calculate the type of nucleosynthesis that comes from two different astrophysical settings
Modify a reaction network to include new rates
Understand and describe the different types of neutrino flavor transformation
Perform calculations that demonstrate the different types of transformation
Understand and explain the importance of neutrinos in nucleosynthesis

Detailed course content

Introduction: Given that several fields are involved, all of which use their own terminology, it is important to give students the language needed to communicate with all groups. Specific topics will be

General types of nucleosynthesis
The ingredients for calculating a nuclear reaction rate
How to read abundance plots from astrophysicists and astronomers
Overview of Big Bang nucleosynthesis with the necessary introduction to cosmology, neutrino physics and the relevant nuclear reactions
Stellar nucleosynthesis with an introduction to hydrostatic equilibrium, nuclear burning and various reaction chains
Solar neutrinos and their detection
Supernovae, starting with main sequence evolution and appropriate reaction chains. Explosive burning from supernova, as well as novae and x-ray bursts. vNeutron capture nucleosynthesis, including s-process and r-process.

Core collapse Supernovae: This part of the course will discuss the triggering of the initial collapse, the bounce and the explosion in core collapse supernovae. Methods of neutrino transport and the evolution of the proto- neutron star will be discussed. The hydrodynamic outflow, including shock propagation – the forward shock and the reverse shock will be discussed.

R-process: This part of the course will be devoted to developing a better understanding of the key issues for the r-process. The two main candidate environments will be discussed: neutron star mergers and neutrino-driven winds of supernovae. An overview will be given of other sites as well. The importance of astronomical observation and interpretation of observation will be discussed. The importance of experiment will be discussed with an overview of which nuclei and properties are accessible at relevant facilities. Ideas for how to best use future experimental results in determining the r-process site will be introduced.

Neutrino Physics: This part of the course will involve developing the basic theory of neutrino flavor transformation. First an overview of weak interactions will be given with a discussion of important cross sections. The importance of various neutrino processes in particular astrophysical settings, such as BBN and core collapse supernovae will be discussed. Neutrino flavor transformation will be developed. Vacuum oscillations and matter enhanced oscillations will be discussed in the solar environment. The self-interaction will be considered, along with the basic phenomenological picture that goes with collective oscillations. Application to supernovae, the early universe and accretion disks will be given.

All course material, slides, codes, exercises etc are available here.

The organization of the day is follows:

 Time            Activity
9am-12pm  Lectures, directed exercises
12pm-2pm  Lunch
2pm-6pm   Hands-on sessions, computational projects
6pm-7pm   Wrap-up of the day

Teachers and organizers

The teachers were

Brian Fields (University of Illinois), bdfields@illinois.edu
George Fuller (University of California San Diego), gfuller@ucsd.edu
Raph Hix (University of Tennessee), raph@utk.edu
Gail McLaughlin (North Carolina State University), cmclaug@ncsu.edu
Hendrik Schatz (Michigan State University), schatz@nscl.msu.edu

The organizers were

Richard Cyburt (Michigan State University), cyburt@nscl.msu.edu [Chairperson]
Gail McLaughlin (North Carolina State University), gcmclaug@ncsu.edu
Hendrik Schatz (Michigan State University) and contact person, schatz@nscl.msu.edu
Morten Hjorth-Jensen (Michigan State University and University of Oslo), hjensen@nscl.msu.edu

Prerequisites

We expect the students to have a background in physics that corresponds to at least one year of graduate studies (or first year of Master of Science studies). Furthermore, we expect that the students are familiar with programming languages and programming concepts. Knowledge and programming skills with languages like C++, Fortran, Python or similar languages is recommended.