i-process workshop

Rationale

The intermediate neutron capture (i) process nucleosynthesis has gained a lot of attraction in the past years. Initially proposed by John Cowan in the 1970s, there has been a recent revival in interest when it was realized that the characteristic neutron density of ~10¹⁵cm^-3 leads to heavy element abundance signatures observed in a variety of stars, including the C-enhanced metal-poor stars with both Ba and Eu enhancements (CEMP-r/s). Simulations of the i-process nucleosynthesis must take into account simultaneously the effects of turbulent convective mixing and the complex (n,γ) - β-decay nucleosynthesis two to six mass numbers away from stability involving large networks. The i-process predictions are hampered by two competing sources of uncertainty, which are the often very vigorous hydrodynamic feedback from convective-reactive H+¹²C reactions, and the nuclear physics uncertainty of the unstable species in the n-capture nucleosynthesis path.

On the experimental side, the i process is quite interesting for existing radioactive-beam facilities since the nuclei of interest can be produced in high enough quantities to allow e.g. (d,p) reaction studies to constrain the respective direct neutron capture cross sections. As one example, the ISAC-II facility at TRIUMF has now commissioned the new EMMA recoil mass separator which will allow a unique access to (d,p) reactions of heavy radioactive, neutron-rich isotopes. First experimental proposals and letters of intent have already been submitted, and in 2019 the first measurements including the relocated TIGRESS gamma-ray spectrometer will take place. In addition, the new CANREB-EBIS will also be commissioned in 2019, and allow to use cleaner charge-bred beams for these reaction studies.

New observations indicating the operation of an i process are becoming available and allow the differentiation of i, s and r processes. An important aspect are uncertainties of such observations and future prospects.

Objectives

This specialized workshop is timely as several experimental opportunities are now opening up. This workshop brings together experimentalists from several labs and the groups performing i-process nucleosynthesis calculations. We will discuss dedicated experimental and theoretical effort for improving our understanding of this process which is required for a better understanding of the origin of the heavy elements. A major objective is to bring the community together by discussing in depth the various approaches, challenges, present results, uncertainties and future directions of both experiments and simulations. Observations will be covered as well with the goal of understanding the quality and quantity of observational constraints from this process.

The objective of this 3-day small workshop is to discuss the recent progress in i-process calculations and create a priority list for key reactions to be measured in the next years. The location will be the TRIUMF auditorium, where the workshop can also be livestreamed for interested participants that could not come. The afternoon of the 3rd day can be used for break-out sessions and dedicated discussions in smaller groups, for example for experiment proposals.

The 3-day workshop is followed by 2-day collaboration time to be organized by participants individually. TRIUMF and UVic will make arrangements to provide the required space and facilities.

Format

Day 1:

Morning: One longer overview talk plus lots of Q&A plus two shorter talks focusing on the state of the simulations, explaining in detail on the astrophysics of i process.

Afternoon: One overview talk about observations, and after that a group discussion (possibly breaking up into groups) on specific scenarios.

Day 2:

Like day 1 but focussing on experiments. Different nuclear physics approaches are presented and plans and ideas from different labs are explained and shared. Talk presentation time equals Q&A time.

Day 3:

• Themed group discussions and break-out sessions on bringing together the lessons learned from day 1 and day 2.
• Create i-process roadmap
• We will have a chance to perform on-site impact studies and tests by running numerical simulations for various prepared scenarios.

Day 4 & 5 (Optional, at UVic or TRIUMF):

Collaboration days: Simulation and experimental researchers are meeting separately and starting first steps to implement roadmap and/or plan out trajectories for the next year.

Contribution types:

We are going to have three types of contributions. Note that you can submit more than one contribution, e.g. a short talk and and a break-out talk. Just fill out the form twice.

Talk-long: Typically longer contributions that provide substantial overview, background and review material and cover a particular approach or research program. These contributions have aspects of lecture and include foundational and established knowledge of a particular simulation approach as well as new result.

Talk-short: Shorter focussed contributions of specific results, for example the main results of one particular paper.

Break-out: 1-2hr un-conference style free but moderated discussion sessions of sub-groups conducted in parallel with delegates deciding on the spot where to participate.

In the abstract submission form you will be able to indicate the type of contribution.

Financial support

This workshop is supported by TRIUMF, the NSF Physics Frontier center JINA-CEE, and the University of Victoria Astronomy Research Center (ARC). Delegates who are in need of financial support, especially junior researchers, should contact the Chair of the SOC, Iris Dillmann, until April 1, 2019. Support may also be available from CheTEC for eligible researchers from CheTEC countries. Please consult the respective webpage how to apply for CheTEC travel support.

JINA-CEE

JINA-CEE workshops and conferences are community events intended for networking and collaboration as well as learning. We value the participation of every attendee and want all attendees to have an enjoyable and productive experience. Accordingly, all attendees are expected to show respect and courtesy to other attendees throughout the workshop and to abide by the following Code of Conduct. Any participant who wishes to report a violation of this policy is encouraged to speak to Iris Dillmann or Falk Herwig, as they have agreed to serve as a point of contact (or if desired, to another member of the organizing team). Thank you for helping make this a welcoming, friendly event for all.

JINA-CEE Code of Conduct

JINA-CEE workshops and conferences are committed to providing a safe, harassment and discrimination-free environment for everyone. Harassment includes offensive verbal comments or jokes related to nationality, gender, sexual orientation, disability, physical appearance, body size, race, religion, sexual images in public spaces, deliberate intimidation, stalking, following, harassing photography or recording, sustained disruption of talks or other events, inappropriate physical contact, and unwelcome sexual attention. All communication should be appropriate for a professional audience including people of many different backgrounds. Be kind to others. Do not insult or put down other attendees. Behave professionally. Participants asked to stop any harassing behavior are expected to comply immediately. JINA-CEE will not allow retaliation against any individual who makes a report of known or suspected harassment. Attendees violating these rules may be asked to leave the event at the sole discretion of the conference organizers.