Low Energy Electron Positron Physics at Jefferson Lab

Mar 23, 2026, 8:30 AM → Mar 27, 2026, 5:55 PM US/Eastern

F113 (CEBAF CENTER)

Axel Schmidt (George Washington University), David Cassidy (University College London), Douglas Higinbotham (Jefferson Lab), Eric Voutier (Université Paris-Saclay - CNRS/IN2P3/IJCLab), Farida Selim (Arizona State University), Joe Grames (JLab), Kevin Jordan (Jefferson Lab), Tyler Kutz (MIT/GW)

The long time interest for positron beams at Jefferson Lab (JLab) forms the basis for an upgrade initiative known as Ce⁺BAF 12 GeV. It will feature high duty factor beams with intensi)es up to 1 μA within an RF-structure. The positrons for these beams will be produced in the bremsstrahlung shower generated by a lower energy mA electron beam impinging on a high-Z target, utilizing the PEPPo (Polarized Electrons for Polarized Positrons) technique for producing highly spin-polarized positrons in a compact accelerator footprint. This methodology opens up the possibility of also producing lower energy positron beams with high intensity and spin polarization. Beams generated from this source would enable unique experimental programs at JLab with the perspective to reveal details of the electromagnetic interaction, unravel the structure of nucleons and nuclei, and investigate the existence of physics beyond the standard model.

The success of Ce⁺BAF 12 GeV relies on the development of crucial R&D for generating the required electron and positron beams. Consequently, new capabili)es should emerge in the meantime, with opportunities for low-energy (sub-GeV) Nuclear Physics, Atomic Physics and Materials Science. Notably, this R&D aims at intense beams both for generation of polarized electrons at mA intensity and linac based positron beams that have the potential to exceed present capabilities by orders of magnitude. Altogether, output of this effort has a great potential to facilitate a venue for low energy e⁺/e^- physics.

The LEEPP@JLab International Workshop aims to explore new pathways for Science with both unpolarized/polarized electron and positron beams. Beam energies ranging from 1-100 MeV for both species as well as moderated/slow positrons to several eV are within the scope of this workshop.

Subjects to be discussed comprises:

- Positron sources, related equipment and diagnostics
- Nuclear Physics
- Atomic Physics
- Materials Science
- Tests of the Standard Model Physics.

 

Book of Abstracts

List of Participants

Mon, March 23

General Introduction

Convener: Douglas Higinbotham (Jefferson Lab)

1 Registration

2 Welcome

3 Workshop Charge

Speaker: Eric Voutier (Université Paris-Saclay - CNRS/IN2P3/IJCLab)

4 Positron physics program at Jefferson Lab

Speaker: Wally Melnitchouk (Jefferson Lab)

5 TBD

Speaker: Farida Selim (Arizona State University)

10:35 AM Coffee break

6 TBD

Speaker: Kevin Jordan (Jefferson Lab)

7 The Ce+BAF 12 GeV concept

Speaker: Yves Roblin (jefferson lab)

8 Recirculating injector at LERF - Layout and optics architecture

Speaker: Alex Bogacz (Jefferson Lab)

12:30 PM Lunch

Positron Source & Instrumentation - I

Convener: Joe Grames (JLab)

9 An R&D program for milliampere spin-polarized electron beams

Speaker: Max Bruker (Jefferson Lab)

10 Design of a high power 10 MeV electron beam injector for the LERF

Speaker: Victor Manuel Lizarraga-Rubio

11 TBD

Speaker: Karl Smolenski

3:15 PM Tea break

12 The solid positron converter target at Jefferson Lab

Speaker: Silviu Covrig Dusa (Jefferson Lab)

13 Development of a rotating target

Speaker: Yu Morikawa (KEK)

4:45 PM Discussion

5:30 PM Reception

Tue, March 24

Materials Science

Convener: Farida Selim (Arizona State University)

14 TBD

Speaker: Alex Weiss (University of Texas at Arlington)

15 Slow mono-energetic positron beams for defect characterization in materials science

Speaker: Marcel Dickmann (University of the Bundeswehr Munich)

16 Total-reflection high-energy positron diffraction: principle and application

Speaker: Yuki Fukaya (Japan Atomic Energy Agency)

10:15 AM Coffee break

17 TBD

Speaker: Andrew Knights (McMaster University)

18 A new pulsed low energy positron system at the UniBwM-Lab:design and current status

Speaker: Ricardo Helm (University of the Bundeswehr Munich)

19 Status of the scanning positron microscope at the NEPOMUC positron source

Speaker: Johannes Mitteneder (Universität der Bundeswehr München)

12:05 PM Discussion

12:30 PM Lunch

Nuclear Physics - I

Convener: Tyler Kutz (Mainz University)

20 Heaven and Earth: connecting JLab to the cosmos

Speaker: Jorge Piekarewicz (Florida State University)

21 TBD

Speaker: Paul Gueye (Facility for Rare Isotope Beams/Michigan State University)

22 Test of Weizsaker-Williams method using Compton scattering from atomic electrons

Speaker: Bogdan Wojtsekhowski (Jefferson Lab)

3:15 PM Tea break

23 Dark sector searches at Ce+BAF

Speaker: Marco Battaglieri (JLab/INFNGE)

24 Positron beam-based search for a MeV mass range axion

Speaker: Ashot Gasparian (NCAT)

4:45 PM Discussion

Wed, March 25

Atomic Physics

25 Phase-sensitive spectroscopy of n=2 positronium fine-structure intervals

Speaker: Donovan Newson

26 An energy tunable positronium beam produced using photo-detachment of positronium negative ions

Speaker: Yasuyuki Nagashima (Department of Physics, Tokyo University of Science)

27 TBD

Speaker: Kenji Shu

10:15 AM Coffe break

28 Electron plasmas and positron bunches in levitating and supported magnetic dipole traps

Speaker: Matthew Stoneking

29 A method to measure positron beam polarization using optically polarized atoms

Speaker: Tim Gay

11:45 AM Discussion

12:30 PM Lunch

Jefferson Lab Tour

5:30 PM Social Event

Thu, March 26

Nuclear Physics - II

Convener: Axel Schmidt (George Washington University)

30 TBD

Speaker: Christian Weiss (Jefferson Lab)

31 TBD

Speaker: Concettina Sfienti (University of Mainz)

32 Low energy neutrino-nucleus interaction

Speaker: Kate Scholberg (Duke University)

10:15 AM Coffee break

33 The Sherman function and its radiative corrections for elastic positron-nucleus scattering

Speaker: Doris Jakubassa (University of Munich)

34 Radiative corrections to elastic lepton-proton scattering with McMule

Speaker: Matteo Ronchi (Johannes Gutenberg University)

35 Neutron-polarizability extraction and new-physics search using deuteron photodisintegration

Speaker: Cornelis Mommers

12:05 PM Discussion

12:30 PM Lunch

Positron Source and Instrumentation - II

Convener: Kevin Jordan (Jefferson Lab)

36 High energy and slow positron sources at KEK

Speaker: Yoshinori Enomoto (KEK)

37 Applications of the compact positron source at SLAC

Speaker: Spencer Gessner (SLAC)

38 Low-energy monochromatic high-intensity high-brightness positron source in the LERF and its possible applications

Speaker: Branislav Vlahovic (North Carolina Central University)

3:15 PM Tea break

39 Moderator informed compact positron source optimization

Speaker: Sophie Crisp (SLAC National Accelerator Laboratory)

40 Investigation of spin rotation in polarized electron and position beams at CEBAF

Speaker: Fanglei Lin (Oak Ridge Notional Laboratory)

41 Spin light polarimetry for low energy electron/positron beams

Speaker: Dipangkar Dutta (Mississippi State University)

5:05 PM Discussion

Fri, March 27

Tests of the Standard Model

Convener: Eric Voutier (Université Paris-Saclay - CNRS/IN2P3/IJCLab)

42 Improved search for CP-violation in ortho-positronium decay

Speaker: Tom-Erik Haugen (National Institute of Standards and Technology)

43 An accelerator-based source of high-intensity quantum-entangled annihilation gamma photons

Speaker: Riad Suleiman (Jefferson Lab)

44 High precision fundamental physics experiments using particle accelerator compact spin-transparent storage rings of low-energy polarized electron/positron beams

Speaker: Vladimir Khachatryan (Mississippi State University)

10:15 AM Coffee break

45 New Physics searches via Beam Normal Spin Asymmetry in Bhabha scattering

Speaker: Aleksandr Pustyntsev (University of Mainz)

46 Positron source characterization and New Physics searches with Bhabha scattering

Speaker: David Mack (JLab)

47 TBD

Speaker: Win Lin (Stony Brook University)

12:05 PM Discussion

12:30 PM Close-out