Theoretical Innovations for Future Experiments Regarding Baryon Number Violation, Part 1

Jordy de Vries (UMass), Joshua Barrow (The University of Tennessee), Leah Broussard (Oak Ridge National Laboratory), Michael Wagman (MIT)

Theoretical Innovations for Future Experiments Regarding Baryon Number Violation, Part 1
Formerly Prospects for Baryon Number Violation by Two Units
An Amherst Center for Fundamental Interactions Workshop
In coordination with Snowmass 2021 Rare Processes and Precision Measurements Frontier: Topical Group on Baryon & Lepton Number Violation

This workshop is open for all to attend! Please join us from 10am-2pm EDT, and feel free to register! We will also be operating an optional Snowmass LOI/Contributed Paper writing session everyday of the workshop, typically from 2pm-3pm.

Abstract submission will be limited to previously agreed participants in light of postponed plans and time limits. We look forward to all of your contributions, participation, and attendance!


The overarching topic of the workshop is the violation of Baryon-minus-Lepton ($ \mathcal{B} - \mathcal{L} $) number. $ \mathcal{B} - \mathcal{L} $ number is exactly conserved in the Standard Model, but the observed matter-antimatter asymmetry of the universe hints that beyond the Standard Model $ \mathcal{B} - \mathcal{L} $ violating processes could exist. Proton decay (PDK) experiments set very strong limits on $ \mathcal{B} $-violating interactions (though most conserve $ \mathcal{B} - \mathcal{L} $), pointing towards very high-energy scales around $10^{13}\,$TeV; however, models exist where the proton is stable while $ \mathcal{B} $ is still not a good symmetry (for instance, if $ \mathcal{B} $ is only violated by two units, i.e. $\Delta\mathcal{B}=2$). Such models lead to unique and powerful experimental signatures such as the transformations of neutrons into antineutrons ($n\rightarrow\bar{n}$, similar to kaon-antikaon oscillations due to strangeness-changing weak interactions) or decays of otherwise stable nuclei via dinucleon annihilation.

Recent years have seen significant theoretical developments of various aspects of these intriguing scenarios, and models have been created that naturally avoid PDK limits while solving other problems within the Standard Model such as the matter-antimatter asymmetry of the universe. Lattice-QCD calculations have made tremendous improvements in calculating QCD matrix elements that connect $\mathcal{B}$-violating quark interactions to observables. Studies in effective field theories for B-violating nuclear interactions have been initiated and applied to light nuclei, while novel intranuclear simulations have been developed to assess whether dinucleon decay processes can be separated from background in medium-heavy nuclei. At the same time, the prospects for future experiments look good: The European Spallation Source, DUNE, PNPI Gatchina, and Hyper-Kamiokande are all expected to attain significantly increased sensitivities to $ \mathcal{B} - \mathcal{L} $ violation.

Despite these recent exciting developments, the collective particle, lattice-QCD, nuclear, and experimental communities are currently rather disjoint and do not meet very often (if at all) to discuss strategy and theoretical necessities for mutualistic progress in the field. A major goal of this workshop is to bring together representatives across these communities to discuss what major challenges exist, what the prospects are for discovering $\Delta\mathcal{B}=2$ violation in future experiments, and the interpretation of experimental signals or limits in the broader context of $ \mathcal{B} - \mathcal{L} $ violation.

Furthermore, the US particle physics community is preparing to identify and rank scientific priorities with the goal of shaping the physics program for the next few decades as part of the Snowmass process, which will initiate in the next year. A summertime workshop frame ensures that we can better serve the experimental community interested in BNV by surveying the opportunities in experiment and theory in order to build the foundation for the strategy for Snowmass. This will allow for in-depth planning for both topics and convener strategies in order to be noticed within the broader field.

Joshua Barrow (University of Tennessee)--email for Indico questions
Leah Broussard (Oak Ridge National Laboratory)
Jordy de Vries (University of Massachusetts Amherst/Riken Brookhaven)--email for ACFI questions
Michael Wagman (Fermi National Accelerator Laboratory)


Snowmass 2021 Letters of Interest for collective iteration by Workshop attendees:
ACFI Synthesis of Field 
DUNE $\mathcal{B-L}$ Violation
ESS NNBAR at the Large Beamport
ORNL to ESS $n\rightarrow n'$ and $n\rightarrow n' \rightarrow \bar{n}$ Searches


Workshop Recordings
Day 1: Morning, Afternoon
Day 2: Morning, Afternoon
Day 3
Day 4


Official Workshop Website
Previous Workshop Website (postponed due to COVID-19)


Registration for the ACFI Theoretical Innovations for Future Experiments Regarding Baryon Number Violation by Two Units, Part I--A Snowmass Official Workshop
  • Albert Young
  • Alexey Fomin
  • Anca Tureanu
  • Bhupal Dev
  • Bingwei Long
  • Elena Golubeva
  • Georgia Karagiorgi
  • James Wells
  • Jean-Marc Richard
  • Jordy de Vries
  • Joshua Barrow
  • Julian Heeck
  • K.S. Babu
  • Leah Broussard
  • Linyan WAN
  • Maury Goodman
  • Pavel Fileviez Perez
  • Prajwal Mohan Murthy
  • Praveen Kumar
  • Rabindra Mohapatra
  • Robert Shrock
  • Rukmani Mohanta
  • Sudhakantha Girmohanta
  • Susan Gardner
  • Sze Chun Yiu
  • Valentina Santoro
  • Zurab Berezhiani