Low Energy Electron Positron Physics at Jefferson Lab

Nov 3, 2025, 8:30 AM → Nov 7, 2025, 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.

 

List of Participants

Mon, November 3

8:35 AM → 12:30 PM General Introduction

Convener: Douglas Higinbotham (Jefferson Lab)

8:45 AM Registration

9:00 AM Welcome

9:15 AM Workshop Charge

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

9:30 AM TBD

Speaker: Wally Melnitchouk (Jefferson Lab)

10:00 AM The Ce+BAF 12 GeV project

Speaker: Yves Roblin (jefferson lab)

10:30 AM Coffee break

11:00 AM TBD

Speaker: Kevin Jordan (Jefferson Lab)

11:30 AM Recirculating injector at LERF - Layout and optics architecture

Speaker: Alex Bogacz (Jefferson Lab)

12:00 PM TBD

Speaker: Andreas Wagner (Helmholtz-Zentrum Dresden-Rossendorf)

12:30 PM → 1:45 PM Lunch

1:45 PM → 5:30 PM Positron Source & Instrumentation - I

Convener: Joe Grames (JLab)

1:45 PM TBD

Speaker: Max Bruker (Jefferson Lab)

2:15 PM TBD

Speaker: Victor Manuel Lizarraga-Rubio

2:45 PM TBD

Speaker: Silviu Covrig Dusa (Jefferson Lab)

3:15 PM Tea break

3:35 PM TBD

Speaker: Vaclav Kostroun (Xelera Research)

4:05 PM Development of a rotating target

Speaker: Yu Morikawa (KEK)

4:35 PM High energy and slow positron sources at KEK

Speaker: Yoshinori Enomoto (KEK)

5:05 PM Discussion

5:30 PM → 7:00 PM Reception

Tue, November 4

8:45 AM → 12:30 PM Materials Science

Convener: Farida Selim (Arizona State University)

8:45 AM Introduction and overview

Speaker: Farida Selim (Arizona State University)

9:15 AM TBD

Speaker: Alex Weiss (University of Texas at Arlington)

9:45 AM Total-reflection high-energy positron diffraction: principle and application

Speaker: Yuki Fukaya (Japan Atomic Energy Agency)

10:15 AM Coffee break

10:35 AM Slow mono-energetic positron beams for defect characterization in material science

Speaker: Marcel Dickmann (University of the Bundeswehr Munich)

11:05 AM TBD

Speaker: Andrew Knights (McMaster University)

11:35 AM The Compact Positron Source project at SLAC

Speaker: Spencer Gessner (SLAC)

12:05 PM Discussion

12:30 PM → 1:45 PM Lunch

1:45 PM → 5:45 PM Nuclear Physics - I

Convener: Tyler Kutz (Mainz University)

1:45 PM TBD

Speaker: Michael Nycz (University of Virginia)

2:15 PM TBD

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

2:45 PM Low-energy electron scattering for nucleons and nuclei, including exotics

Speaker: Toshimi Suda (Rsearch Center for Electron-Photon Science)

3:15 PM Tea break

3:35 PM Heaven and Earth: connecting JLab to the cosmos

Speaker: Jorge Piekarewicz (Florida State University)

4:05 PM Test of Weizsaker-Williams method using Compton scattering from atomic electrons

Speaker: Bogdan Wojtsekhowski (Jefferson Lab)

4:35 PM Low energy neutrino-nucleus interaction

Speaker: Kate Scholberg (Duke University)

5:05 PM Discussion

Wed, November 5

8:45 AM → 12:30 PM Atomic Physics

Convener: David Cassidy (University College London)

8:45 AM TBD

Speaker: David Cassidy (University College London)

9:15 AM An energy tunable positronium beam produced using photo-detachment of positronium negative ions

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

9:45 AM TBD

Speaker: Kosuke Yoshioka (The University of Tokyo)

10:15 AM Coffe break

10:35 AM TBD

Speaker: Tim Gay (University of Nebraska-Lincoln)

11:05 AM TBD

Speaker: Daniel Murtagh (Marietta Blau Institute for Particle Physics)

11:35 AM TBD

Speaker: Gabriel Cecchini (University of California)

12:05 PM Discussion

12:30 PM → 2:00 PM Lunch

2:00 PM → 4:30 PM Jefferson Lab Tour

Thu, November 6

8:45 AM → 12:30 PM Tests of the Standard Model

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

8:45 AM Improved search for CP-violation in ortho-positronium decay

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

9:15 AM TBD

Speaker: Riad Suleiman (Jefferson Lab)

9:45 AM TBD

Speaker: Aleksandr Pustyntsev (University of Mainz)

10:15 AM Coffee break

10:35 AM TBD

Speaker: David Mack (JLab)

11:05 AM Dark sector searches at Ce+BAF

Speaker: Marco Battaglieri (INFN-GE)

11:35 AM TBD

Speaker: Win Lin (Stony Brook University)

12:05 PM Discussion

12:30 PM → 1:45 PM Lunch

1:45 PM → 5:30 PM Positron Source and Instrumentation - II

Convener: Kevin Jordan (Jefferson Lab)

1:45 PM Channeling experiments at the Mainz Microtron MAMI and the new positron beam line

Speaker: Werner Lauth (University of Mainz)

2:15 PM Positron diffraction and positronium studies with high-intensity slow-positron beams generated by an S-band LinAc

Speaker: Ken Wada (High Energy Accelerator Research Organization (KEK))

2:45 PM Moderator informed compact positron source optimization

Speaker: Sophie Crisp (SLAC National Accelerator Laboratory)

3:15 PM Tea break

3:35 PM TBD

Speaker: Fanglei Lin (Oak Ridge Notional Laboratory)

4:05 PM TBD

Speaker: Tim Gay (University of Nebraska-Lincoln)

4:35 PM Spin light polarimetry for low energy electron/positron beams

Speaker: Dipangkar Dutta (Mississippi State University)

5:05 PM Discussion

Fri, November 7

8:05 AM → 12:30 PM Nuclear Physics - II

Convener: Axel Schmidt (George Washington University)

8:45 AM TBD

Speaker: Christian Weiss (Jefferson Lab)

9:15 AM The Sivers effect in atomic Compton scattering

Speaker: Andrea Signori (University of Turin and INFN)

9:45 AM TBD

Speaker: Concettina Sfienti (University of Mainz)

10:15 AM Coffee break

10:35 AM The Sherman function and its radiative correrctions for elastic positron-nucleus scattering

Speaker: Doris Jakubassa (University of Munich)

11:05 AM Radiative corrections for elastic lepton-proton scattering with McMule

Speaker: Matteo Ronchi (University of Mainz)

11:35 AM Positron beam-based search for a MeV mass range axion

Speaker: Ashot Gasparian (NCAT)

12:05 PM Discussion

12:30 PM → 1:45 PM Lunch

1:45 PM → 5:30 PM Contributions

1:45 PM Overview on the Nuclear Radius Extraction Collaboration

Speaker: Vladimir Khachatryan (Duke University)

2:10 PM Low-energy monochromatic high-intensity high-brightness positron source in the LERF and its possible applications

Speaker: Branislav Vlahovic (North Carolina Central University)

2:35 PM A new pulsed low-energy positron system at UniBwN-Lab: design and current status

Speaker: Ricardo Helm (University of the Bundeswehr Munich)

3:00 PM Status of the scanning positron microscope at the NEPOMUC positron source

Speaker: Johannes Mitteneder (Universität der Bundeswehr München)

3:25 PM Discussion & Close-out