Low-Energy Electron Scattering for Nucleon and Exotic Nuclei (LEES2024)

Oct 28, 2024, 8:00 AM → Nov 1, 2024, 6:00 PM Asia/Tokyo

TOKYO ELECTRON House of Creativity (東北大学知の館), Tohoku University

The Low-Energy Electron Scattering for Nucleon and Exotic Nuclei (LEES2024) will be held in Sendai, Japan during October 28 - November 1, 2024.

Overview

We are currently conducting two unique low-energy electron scattering experiments in Japan to study nucleon and exotic nuclei: ULQ2 (Ultra-Low Q2) with Ee = 10 – 60 MeV at Tohoku University and SCRIT with Ee = 150 – 300 MeV at RIKEN.  The ULQ2 team has recently completed measurements of elastic electron scattering for the charge radius determination of proton covering the lowest-ever momentum transfer, and the SCRIT collaboration has successfully conducted the world’s first electron scattering experiment for an online-produced radioactive isotope.

Considering such progress made in Japan, which showcases new research opportunities presented by low-energy electron scattering, we decided to host an international workshop in Japan to discuss recent findings, exchange insights, and foster future collaborations. LEES2024 is designed as an in-person workshop to discuss primarily the size and structure of nucleons and exotic nuclei and related studies underway worldwide. Possible uses of low-energy electron accelerators for new physics will also be an important topic of this workshop.

 

Key Topics

Experimental and theoretical studies on
      Electron scattering for nucleons and nuclei including exotic ones,
      Size and structure of nucleons and nuclei including exotic ones,
      Photo-nuclear reaction,
New physics with high-intensity low-energy electron beams.
 

Scientific program

  The program will consist of presentations by invited speakers, contributed presentations, and posters. The detailed program will be shown later on the workshop website. 

 

Venue

  The workshop will take place at the TOKYO ELECTRON House of Creativity, located on the Katahira Campus of Tohoku University. The campus is in downtown Sendai and is approximately a 15-minute walk from the Sendai Station. (Website: https://www.tfc.tohoku.ac.jp/)."
  On the final day of the workshop, November 1st (Friday), we will convene at RARIS on the Mikamine Campus for additional sessions and a RARIS facility tour. We will provide a transportation bus between the Katahira Campus and the RARIS facility.
 

Accommodation

  As late October is the best season for tourism in the Sendai area, hotels in Sendai are expected to be crowded. Workshop participants are advised to book their accommodation well in advance.

 

Important dates

June 15th              Registration open

Oct. 10th               Registration deadline:

Oct. 28th – Nov. 1st            Workshop

             Oct. 28th               Welcome reception

             Oct. 29th               Poster session

             Oct. 30th               Excursion (one day)

             Oct. 31st               Banquet

             Nov. 1st                RARIS Facility tour

 

Registration, Fees

  The registration site will open on June 15th.  Please register by Oct. 10th.
If you wish to present your research, please submit the title and abstract of your presentation at the registration. 

  The registration fee is JPY 30,000.  This includes participation fees for this workshop, coffee break, welcome reception, excursion, and banquet. Concerning the accompanying person, the fee for the welcome reception, excursion, and banquet is JPY 15,000.

  Registration fee will be paid at the workshop desk. Only cash (Japanese Yen) is accepted. 
 

Excursion

  The one-day excursion includes a boat trip to Matsushima, and a visit to Zuiganji Temple after a traditional Japanese-style lunch. Matsushima is renowned as one of Japan's three most scenic spots, and late October is the best season to visit, offering beautiful autumn foliage and pleasant weather, and making the best season to enjoy this scenic area.
 

VISA

If you need VISA, please contact lees2024@raris.tohoku.ac.jp.

 

Local Organizing Committee

Toshimi Suda (RARIS, Tohoku Univ.)  Chair

Yuki Honda (RARIS, Tohoku Univ.)

Tetsuya Ohnishi (RIKEN Nishina Center)

Kyo Tsukada (ICR, Kyoto Univ.)

Shun Iimura (Rikkyo Univ.)

 

Contact: lees2024@raris.tohoku.ac.jp

 

Hosts

This workshop is hosted by the following universities and institutions.

　　Tohoku University, RARIS

　　RIKEN Nishina center accelerated-based science

　　Kyoto University, ICR

　　Rikkyo University

 

Supports

This workshop is supported by JSPS KAKENHI Grant Number 20H05635.

LEES2024_final_circular.pdf

LEES2024Poster.pdf

LEES_SocialEvents.pdf

Monday, October 28

Registration

1 Registration

Opening

2 Opening

Speaker: Toshimi Suda (Research Center for Electron-Photon Science, Tohoku University)

LEES_SocialEvents.key.pdf

Session

3 First electrn scattering off online-produced 137Cs and prospects for 132Sn

In 2022, we successfully measured the angular distribution of electron elastic scattering off 137Cs nuclei produced online at the SCRIT facility. I will present details of this experiment and prospects for the 132Sn experiment.

Speaker: Masanori Wakasugi (Kyoto University)

10:30 AM Caffe break

Session

4 New structure observables in a future GANIL facility for electron-radioactive ion collisions

Electron scattering on radioactive nuclei could provide nuclear observables with an unprecedented radial sensitivity. In these nuclei, unique quantum phenomena occur but basic properties such as charge densities are still completely unknown. Precise densities extracted from the scattering data could be confronted to modern structure calculations. Such studies would provide better insight both on the accuracy of the many-body treatment of the new techniques and on the validity of the microscopic characteristics of realistic nuclear interactions used in state-of-the-art models. Our goal is to build an electron beam accelerator implanted at a facility providing a variety of radioactive ion beams, such as GANIL, to perform electron-radioactive ion collisions and measure cross sections and excitation spectra. This talk will present the project conceived for the GANIL future. The measurements of electron scattering can be renewed taking advantage of the combined progress done in the fields of theory, accelerator techniques and experiments. Developments in the accelerator design and electron-ion collision techniques would offer the increased luminosities required for the project from 10(26) up to 10(28−29)/cm2 /s for the main physics cases of the first step, expanding to 10(29−31) in the long-term range for the inelastic form factors.

Speaker: Dr Valérie Lapoux (CEA-Saclay)

TalkProjectERIBphysLEESv29oct2024vf.pdf

5 A dual electron/positron linac and laser spectroscopy system for nuclear charge radii measurements

Particle accelerators enable scientists to probe deeper into nuclei to extract key observables to validate or improve our nuclear theoretical frameworks. A fundamental quantity is the precise measurement of the nuclear charge radius. Electron scattering is the best tool to probe such quantity, with laser spectroscopy being a highly precise complementary technique that extends the reach to unstable isotopes. However, the latter requires known reference radii. The SCRIT facility (RIKEN, Japan) is the only one in operation that can scatter electrons off rare isotopes. The Facility for Rare Isotope Beams (Michigan, USA) has opened an uncharted window in the nuclear landscape from the proton to neutron driplines. Technological breakthroughs in accelerators, e.g. C-beta magnets and cold copper cavities, allow building relatively low costs high energy, high current compact machines. Two prototypes are being studied to be coupled with an ion trap: one is a compact linac to deliver (un)polarized electron, positron and photon beams and the other is a laser system to perform laser spectroscopy on the same isotopes. This dual system will provide the foundation for a possible Advanced Rare-isotope Electron Scattering (ARES) facility in the U.S. A review of the status for this effort will be discussed.

Speaker: Prof. Paul Gueye (FRIB/MSU)

LEES2024_Gueye_final.pdf

12:00 PM Lunch

Session

6 Charge radii of unstable nuclei

Speaker: Prof. Xiaofei Yang (Peking University)

7 Present status and perspective of the ISOL system, ERIS,at the SCRIT electron scattering facility

In electron scattering off unstable nuclei, the radioactive isotope (RI) beam production is
one of most important experimental parts. A low-energy high-quality RI beam with low emittance and small energy spread is needed for SCRIT. Furthermore, a high-intensity RI beam is also required in order to obtain a sufficient luminosity. To satisfy these requirements, we constructed an online isotope separator named electron-beam-driven RI separator for SCRIT, ERIS, at the SCRIT electron scattering facility.[1] In ERIS, photofission of uranium is used for the RI production, and production target is self-made uranium carbide disks, which is 18-mm in a diameter and 0.8-mm in a thickness.
%which total amount of uranium is approximately 28 g. Recently, 137Cs beam was produced for the world's first electron scattering experiment with online-produced RI
at the SCRIT facility.[2], and rate of pulsed 137Cs ion beam was 2*10^7 ions/pulse with a 15-W electron beam and a total of approximately 28-g uranium.

In this contribution, we will report the present status and upgrade plane of ERIS.

Speaker: Dr Tetsuya Ohnishi (RIKEN Nishina Center for Accelerator-Based Science)

241028_eris.pptx

8 the ALTO facility

Speaker: Dr Fadi Ibrahim (IJCLab, CNRS, France)

3:30 PM Caffe break

Session

9 Present Status of the RAON ISOL facility and future possibilities for physics programs

The Rare Isotope Accelerator complex for ON-line experiment (RAON) is being developed as the flagship Radioactive Isotope (RI) facility for fundamental research and applications in Korea. The initial objective of the RAON in nuclear physics is to expand the nuclear chart through the in-flight method with RI beams and the measurement of the properties of newly discovered isotopes. A high-power Isotope Separator On-Line (ISOL) facility is the key facilitiy to provide high-quality and intense RI beams, which are indispensable for this method. The design, construction, and installation of the ISOL system and its commissioning with stable isotope beams have been completed, and it has been confirmed that all of the requirements have been satisfied. RI beam extraction tests are currently being conducted using SiC and LaC2 targets. In this presentation, we will discuss the present status of the RAON ISOL facility. Additionally, future possibilities for physics programs using RAON ISOL will be discussed.

Speaker: Dr Takashi Hashimoto (Institute for Basic Science)

10 Development of a High-Flux MRTOF Isobar Separator for Beam Purification

The SCRIT group is preparing to conduct an electron scattering experiment on 132Sn. However, isobaric contaminants in the ion beam present a significant challenge. To address this, we are developing a beam purification system based on the MRTOF (Multi-reflection time-of-flight) mass spectrograph. In this presentation, we will discuss the current status of the development, our plans, and the challenges that remain. Once completed, this system is expected to enable the production of high-intensity, pure single-nuclide beams, which could be utilized at ISOL facilities worldwide.

Speaker: Shun Iimura (Rikkyo University)

11 Ion traps for advancing nuclear physics in Orsay

Traps have become indispensable tools for investigating the fundamental properties of atomic nuclei. Their widespread use at rare isotope facilities has generated a wealth of nuclear data, impacting not only nuclear physics but also related fields such as astrophysics, neutrino physics, and atomic physics. The IJCLab at Orsay has a long-standing tradition of developing such tools, and in this presentation, I will discuss the latest advancements in trap technology, with a focus on two ongoing projects: MLLTRAP and HINA. MLLTRAP is a series of traps, culminating in a double Penning trap mass spectrometer designed for precise mass measurements of photofission fragments produced at the ALTO-LEB facility (Accélérateur Linéaire et Tandem à Orsay – Low Energy Branch). The HINA project, on the other hand, focuses on developing different types of traps, such as an Electron Beam Ion Trap (EBIT) and a Zajfman trap (electrostatic mirror type), aimed at studying the nuclear decay of highly charged ions. In this talk, I will present the scientific motivations behind each project, along with their current status. Additionally, I will touch on a future project, DESTIN@PERLE, which involves the development of traps for electron scattering studies at PERLE (an Electron Recovery Linac) currently under construction at Orsay, to probe the deep structure of exotic nuclei.

Speaker: Dr Sarah Naimi (IJCLab (France))

Naimi_LEES2024.pdf

12 Unexplored excitation due to triaxial deformation and electron scattering

Recent theoretical studies indicate that triaxial deformation may occur in many nuclei including those having axially symmetric shapes in conventional view. I will present an overview of such a novel picture confirmed by the state-of-the-art large-scale shell-model (or CI) calculations. I will then talk about a possible experimental clarification for the case of 154Sm nucleus. This nucleus has been classified as a typical example of axially-symmetric prolate deformation, but it may be triaxially deformed with triaxial parameter gamma equal to about 4 degrees. As a direct test of this prediction, the electron inelastic scattering is expected to play a pioneering role. I will further report what is predicted for other nuclei, as well as the significance of this case in a broad view.

Speaker: Prof. Takaharu Otsuka (RIKEN Nishina Center)

Welcome reception

13 Welcome reception

Tuesday, October 29

Session

14 The proton radius puzzle status and future measurements

The proton radius puzzle, created by two disagreeing precision measurements in 2010, has been the focus of intense work efforts. With new results in the last decade, our understanding of the puzzle has evolved, but it has not been fully resolved yet. In the talk, I will give an overview over the current status of the puzzle, and discuss the current and future plans for measurements, with a focus on measurements at MUSE, AMBER and MAGIX.

Speaker: Prof. Jan Bernauer (Center for Frontiers in Nuclear Science, Department of Physics and Astronomy, Stony Brook University)

lees2024.pdf

15 Proton Charge Radius from Electric Form Factor Measurements at Low Q2

In my presentation, I will discuss past and future measurements of the proton's electric form factor at MAMI and MESA and introduce a novel numerical approach for extracting the proton charge radius.

Speaker: Prof. Miha Mihovilovic (Faculty of Mathematics and Physics, University of Ljubljana / Jozef Stefan Institute)

MihaTalkLEES2024out.pdf

MihaTalkLEES2024out.ppsx

16 Proton Charge Radius Experiments at JLab

Speaker: Mr Weizhi Xiong (Shandong University)

LEES_PRad.pdf

10:30 AM Caffe break

Session

17 Low-energy electron scattering facility at RARiS

Speaker: Dr Yuki Honda (ELPH, Tohoku University)

20241029LEES2024_honda.pdf

18 Determination of the proton charge radius during the ULQ2 experiment

The proton charge radius is one of the most basic characteristics of the nucleons and is crucial for many applications such as the determination of the Rydberg constant, for QED tests, etc. Its determination is a hot topic in several physics communities as it has been reported close to 0.84 fm or 0.88 fm using electron scattering, atomic and muonic hydrogen spectroscopy. The proton charge radius is obtained from the cross section of the elastic lepton proton scattering at low momentum transfer Q2. At RARIS, we are conducting the most reliable measurement of the proton charge radius with electron proton scattering during the ULQ2 (Ultra-Low Q2) experiment using the world’s lowest energy beam for electron scattering. The main specificities of the ULQ2 experiment are the low beam energy and the use of a plastic CH2 target that allows the absolute normalization of the hydrogen to the carbon scattering cross-section. The new beam line as well as the twin spectrometers have been commissioned and the measurement of the detector efficiency is already complete. Most of the data taking for the proton charge radius measurement is finished and the analysis to determine the proton radius is underway.

Speaker: Mr Clement Legris (Tohoku University, ELPH)

LEES2024_slides.pdf

19 Deuteron charge radius by low-energy electron scattering at the ULQ2 facility

The precision result of a deuteron charge radius measurement (2.12562(78) fm) using muonic deuterium spectroscopy has about the 3.5 sigma discrepancy with the average of ordinary deuterium spectroscopy (2.1415(45) fm); this resulted in the deuteron radius puzzle, but the result of electron scattering (2.13(1) fm) is too imprecise to distinguish this discrepancy. New, reliable, and precise results from electron scattering are needed. The ULQ2 facility in Tohoku University realize the form factor measurement of deuteron at the lowest ever Q by using the lowest ever beam energy that is 10 to 60 MeV. In the talk, we will report the recent status of the experiment and discuss the possibility to derive the neutron charge radius that is poorly known from the deuteron charge radius.

Speaker: Taiga Goke (RARIS, Tohoku University)

LEES2024_goke_final.pdf

20 γZ-exchange contributions in low-energy parity-violating ep scattering

In this work, the γZ-exchange contributions in the low-energy elastic parity violating ep scattering are discussed with the approximation me = 0, where me is the mass of electron. By expanding the γpp and Zpp interactions on the momentum of photon and considering both the leading-order and the next-to-leading order interactions, we calculate the amplitudes of the γZ-exchange diagrams. After performing the loop integral, we expand the results in the low energy limit, and obtain the analytic expressions for the amplitudes. Numerical comparisons show that the analytic expressions are very close to the full results over a large region. We investigate the power behaviors of these contributions and find that some are enhanced by a kinematic factor in the low energy limit. Additionally, in some cases, the imaginary parts of the contributions from the next to-leading-order interactions are at the same order as those from the leading-order interactions. Furthermore, the corresponding contributions to the physical observable quantity APV are also discussed. Combining all the properties together, we conclude that these analytic expressions describe the leading-order contributions of the γZ-exchange helicity amplitudes in some regions.

Speaker: Qianqian Guo (Southeast University)

Qian-Qian-Guo-gamma-Z-exchange-contributions-in-parity-violating-ep-scattering-at-low-energy.pdf

12:30 PM Lunch

Session

21 Spatial Moments of the proton charge density

Based on an integral method [Phys. Lett. B 808, 135669 (2020)], spatial moments of the proton charge density are determined by means of a global analysis of available proton electric form factor data from Rosenbluth separation and low squared four-momentum transfer experiments. Specific attention is paid to the evaluation of the systematic errors of the method, particularly the sensitivity to the choice of the mathematical expression of the form factor fitting function. Within this comprehensive analysis of proton electric form factor data, the moments of the proton charge density are determined for integer order moments.

Speaker: Dr Dominique Marchand (IJCLab Orsay, CNRS/ Université Paris-Saclay, France)

2024-10-29_LEES24_D_Marchand.pdf

22 Proton Radius and Muonic Atom Spectroscopy

The "proton radius puzzle," originating from Lamb shift spectroscopy of muonic hydrogen atoms, has spurred extensive precision physics research involving various theoretical and experimental efforts. This talk will review recent advancements in the field, including ongoing preparations for a spectroscopy experiment on the hyperfine splitting in muonic hydrogen atoms at RIKEN/KEK, and discuss its potential impact on our understanding of proton structure.

Speaker: Dr Sohtaro Kanda (KEK)

Mup_LEES2024_20241029.pdf

23 Status of lattice QCD determination of nucleon form factors at the physical point and its challenge for the proton charge radius

We present our recent results for nucleon elastic form factors obtained from 2+1 flavor lattice QCD at the physical point with a large spatial extent of about 10 fm. Our calculations are performed with the PACS10 gauge configurations generated by the PACS Collaboration with the six stout-smeared O(a) improved Wilson-clover quark action and Iwasaki gauge action at beta=1.82 and 2.00 corresponding to lattice spacings of 0.085 fm and 0.063 fm respectively. We first evaluate the isovector quantities including the axial charge that is one of the most important pieces of information on the nucleon structure. Moreover, we also determine three kinds of isovector RMS radii such as electric, magnetic and axial ones at the two lattice spacings. We then discuss the discretization uncertainties on the axial charge and isovector RMS radii towards the continuum limit. Finally, we comment on the isoscalar nucleon form factors required for the evaluation of the proton charge radius.

Speaker: Prof. Shoichi Sasaki (Department of Physics, Tohoku University)

LEES2024_Sasaki_v3_public.pdf

4:00 PM Caffe break

Session

24 Few-nucleon system study via low-energy electron scattering

Speaker: Yukie Maeda (University of Miyazaki)

25 Quantum Monte Carlo calculations of magnetic structure in light nuclei

In this contribution, I present a recent theoretical study of the magnetic structure of light nuclei; namely, I will discuss the calculation of magnetic moments and form factors in $6\le A \le 10$ systems using the Norfolk model-- a chiral effective field theory based nuclear interaction-- and its consistent electromagnetic current operators. To study these observables, I employ quantum Monte Carlo techniques to stochastically solve the many-nucleon Schr\"{o}dinger Equation. Using the Norfolk model, it is possible to understand in detail the role of many-nucleon currents and correlations in describing low-energy magnetic moment data. The discussion of magnetic form factors will cover how these same two-body currents impact predictions of elastic electron scattering, as well as the role of different multipolarities in describing experimental data. Finally, I will show results for predicted magnetic form factors in light radioisotopes and will discuss the interpretation of an interesting effect predicted for pairs of mirror nuclei.

Speaker: Dr Garrett King (Washington University in St. Louis)

20241027-king-lees.pdf

Poster

26 Analytic Approximation of Beam Dynamics in Multi-RFQ for Isobar Separation

I have analytically derived low-voltage approximations of tunes in RFQ with multiple radio frequencies to increase the efficiency of finding conditions of betatron resonances for isobar separation. The SCRIT (Self-Confining RI Ion Target) electron scattering facility has been aiming at the 132Sn-electron scattering, which requires eliminating an isobar, 132Sb, from the ion source. To achieve such a separation with a mass sensitivity of 0.002%, Pf. Wakasugi proposes utilizing a sharp betatron resonance in MRFQ (RFQ with Multiple radio frequencies). The current way to find parameters causing the resonance is only numerical calculations with possible parameters, which is inefficient and impractical. To acquire the values of tunes more expeditiously than numeric operation, I have analytically computed low voltage approximations of tunes up to the second order by direct calculation of the transition matrix in MRFQ. My succeeding objective is to refine the approximation and obtain the mass sensitivity of each resonance.

Speaker: Mr Yoshihiro Saito (Kyoto University)

27 Cooling efficiency of MRTOF bunchers

We are conducting simulations to improve ion bunch cooling efficiency for the development of an isobar separator for 132Sn and 132Sb using SCRIT. The goal is to cool 10^5 ions to room temperature within 1 ms and then extract them to MRTOF for isobar separation. The setup involves simulations using a quadrupole ion trap. By applying RF and DC, we change the potential to collect the cooled ions in the potential well. Subsequently, the potential barrier is lowered to send the ions to MRTOF. As ions move through the gas-filled trap, they lose energy due to collisions with the gas, a process known as cooling. Without this effect, ions would gain energy due to potential differences, making them unsuitable for extraction to MRTOF. Currently, we are focusing on the type and pressure of the gas, observing their effects on trapping and energy dissipation. Other parameters include DC value, potential shape, ion temperature, spread, and extraction efficiency to MRTOF. The goal is to optimize these parameters.

Speaker: Ms Rin Teraguchi (Rikkyo University)

28 Development of Position Detector for Luminosity Monitor in SCRIT Experiment

The SCRIT group aims to perform electron scattering experiments targeting short-lived radioactive nuclei using a novel internal target generation method (SCRIT method) in the electron storage ring. The target ions trapped in the SCRIT device have variable densities, so a luminosity monitor is required besides the scattered electron measurement system when targeting unstable nuclei with unknown charge density distribution. To obtain the scattering cross section with high accuracy, the absolute value of luminosity with high precision is required. In this study, I aim to develop a position detector for more accurate luminosity measurement.

Speaker: Mariko Tachibana (Kyoto University, student)

29 Developmental measurement of proton elastic scattering for 50Ca

Study of nuclei with exotic neutron to proton number ratios is one of the frontiers in the quantum many-body system of nucleons. To clarify the size and structure of neutron-rich and neutron-deficient nuclei, we have applied proton elastic scattering as a different probe from electron scattering. It is essential to determine the proton and neutron density distribution of neutron-rich and neutron-deficient nuclei, which is related to symmetry energy in the equation of state (EoS) of nuclear matter. Measurement of proton elastic scattering for 50Ca, which is a neutron-rich nucleus, has been performed at RIKEN RI Beam Factory (RIBF). In this study, a new experimental setup with Silicon Strip Detector (SSD) has been adopted for detection of recoil protons. In this presentation, results of the developmental measurement of proton elastic scattering will be reported and distribution of excited energy, that demonstrates how well elastic and inelastic scattering events can be separated, will be discussed.

Speaker: Tomoya Nakada (Kyoto University)

30 Evaluation of momentum and angular dispersion of 208Pb ion trapped on SCRIT using ion analyzer simulation

work in progress

Speaker: Mr Kikuchi Yuta

31 High-spin states of nuclei around the N=50 and 82 closed shells

The excited states of nuclei near the N=50 and 82 closed shells can be well described by the shell model, thereby offering a suitable laboratory to test its predictions. Therefore, it has been attracting a large number of experimental and theoretical studies for these nuclei. Such studies are of great significance in providing information on the mechanism of particle-hole excitations of the N=50 and 82 cores. Using the in-beam -spectroscopic techniques, we have populated the high-spin states of 88Y (Z=39, N=49), 89Y (N=50), 141Pr (Z=59, N=82), and 142Pr (N=83) by the heavy-ion fusion evaporation reactions. The high-spin states of 142Pr have been reported for the first time. Combining large-scale shell model calculations, the neutron excitations across the N = 50 and 82 gap in 89Y and 141Pr have been observed. The level structures come from neutron core excitations have also been identified in 85Br (Z=35, N=50) and 92Mo (Z=42, N=50). The systematic features of neutron cross-shell excitations in the N=50 and 82 isotones have also been investigated.

Speaker: Dr Zhiquan Li (Shandong University, Weihai)

32 Ion-trapping properties of SCRIT: Target performance as a function of electron beam conditions

A SCRIT (Self-Confining RI Ion Target) method is a target-forming technique in an electron storage ring for electron scattering experiments with unstable nuclei. A target ion beam with a charge state of 1+ is injected into a SCRIT device. They are trapped transversely by periodic focusing forces from electron beam bunches and longitudinally by the electrostatic well-potential in the SCRIT device. The time evolution of luminosity during the ion trapping is monitored by the luminosity monitor. After ion trapping in the SCRIT device, the target ions are extracted and transported to the ion analyzer. The time evolutions of the trapped charge and charge state distributions were measured by the ion analyzer. Currently, the target ions trapped in the SCRIT contribute only 10–20% to the electron scattering. To improve the contribution ratio, optimizing the SCRIT performance is necessary. In this presentation, we report and discuss the target performance depending on the electron beam conditions for the target optimization.

Speaker: Dr Ryo Ogawara (RIKEN Nishina Center)

33 Measurement of neutron distribution radius in ²⁰⁸Pb by low-energy electron scattering

The charge density distributions of nuclei are best determined by elastic electron scattering, and the stable nuclei that have been studied so far have played an essential role in revealing their internal structure.
Recently it was pointed out theoretically that the 4th moment of the charge density distribution, <r_c^4>, contains the information of neutron-distribution radius^([1]).
Experimental determination of <r_c^4> can be two methods;
1) the form factor F(q) (where q is the momentum transfer) is measured from elastic electron scattering cross section and calculated using the charge density distribution ρ(r) obtained as its Fourier transform, and 2) obtained without ρ(r) via Taylor expansion of F(q) at low q region.
The neutron radius of ²⁰⁸Pb, whose charge density is the most precisely known, has been extracted from <r_c^4> following the method 1), and has been found to be consistent with the parity-violating electron scattering results performed out at JLab.
We are currently conducting the method 2) to extract <r_c^4> from the elastic cross section of ²⁰⁸Pb to be measured with ULQ2 facility. The required precision for the cross section is the order of 10⁻³ to determine the neutron-distribution radius accurately.
I will discuss the current status and perspectives of this project.

Speaker: Rika Danjo (RARIS, Tohoku University)

34 MRTOF simulation for optimal isobar separation between 132Sn and 132Sb

The SCRIT team aims to measure the structure of 132Sn in the future. However, they have already encountered some challenges, such as the isobar problem. The long-term goal of the Rikkyo University team is to use a multiple reflection time-of-flight mass spectrometer (MRTOF-MS) to accurately separate isobars with relative mass ‘dm/m=1/39783’. MRTOF is an instrument that measures the mass from the time of flight of ions stored and cooled in an ion trap by repeatedly passing them back and forth between a pair of electrostatic mirror electrodes. We first used an existing theoretical framework to reproduce the motion in the electrostatic mirrors as a one-dimensional model. According to this theory, by adjusting electrode size and electric field strength, we can approximately predict when the temporal spread between charged particles is minimized in the absence of particle interactions. This prediction suggests that separation of 132Sn and 132Sb within 1 ms is possible. This would achieve spatial separation and allow the particles to be transported to the SCRIT system. The current work is focused on incorporating these findings and extending them to a three-dimensional model of the motion in the electrostatic mirror of the MRTOF-MS. This paper presents an overview of this research.

Speaker: Mr Hiroto Matsubara (Rikkyo university)

35 The Upgrade of Accelerating Cavity of SR2 for Eliminating Beam Instability

To stabilize the ion trap and improve efficiency of SCRIT (Self-Confining RI Ion Target) experiment, it is essential to eliminate beam instability in the electron storage ring, SR2 (SCRIT-equipped Riken Storage Ring). The main cause of the beam instability is the Higher Order Modes (HOM) of the acceleration cavity induced by the wake field of the beam, which requires improvement of the acceleration cavity. In order to suppress the beam instability, we are introducing Landau cavities as harmonic cavities and developing a new acceleration cavity using TM020 mode and slot-type HOM damping mechanism. It is expected that the growth of instability will be suppressed by adding third-order harmonic voltage by Landau cavities. In addition, by installing a slot-type HOM damping mechanism at the nodal position of the TM020 mode, only the HOM causing the instability can be damped. The present status of these cavity developments is reported in this study.

Speaker: Mr Yusei Maeda (Kyoto University)

36 Triaxiality of 154Sm by Low Energy Electron Inelastic Scattering

In the 1950s, Bohr and Mottelson established the picture that most of heavy atomic nuclei deform into a prolate shape consisting of one long axis and two short axes of equal length. However, recent theoretical calculations by T. Otsuka et al. indicate that these nuclei prefer a triaxial shape, with all three axes having different lengths. Additionally, the presence of excited states due to rotational bands in the short-axis plane caused by triaxial asymmetry has also been suggested.
While $^{154}$Sm has long been regarded as a prolate nucleus, calculations by T. Otsuka et al. show that it weakly deforms into a triaxial shape, suggesting the existence of an excited state, $2^+_{g\gamma}$, around $E_x$ = 2.7 MeV. By measuring this excited state through low-energy electron scattering, we can determine that the total angular momentum of this excited state is $J=2$ by the momentum transfer dependence of the form factor. An experiment to measure this excited state is planned at RARiS, Tohoku University, with a test experiment scheduled in November. I will discuss the feasibility of measuring the $2^+_{g\gamma}$ state at Tohoku University and future studies.

Speaker: Kengo Hotta (RARIS, Tohoku University)

Wednesday, October 30

Excursion

Thursday, October 31

Session

37 Impact of the isospin symmetry breaking on nuclear densities

The isospin symmetry breaking part of the nuclear interaction is a small part of the whole; however, it sometimes gives important contributions to nuclear properties, such as the difference of mirror nuclei, the isobaric analog states, and the neutron-skin thickness. The isospin symmetry breaking terms also affect the estimation of the slope parameter of the nuclear symmetry energy.
In this talk, I will first summarize our recent study on the isospin symmetry breaking in nuclear properties and point out the lack of precise determination of the effective nuclear interaction or energy density functional for the isospin symmetry breaking terms. Then, I will introduce our recent attempt to determine the energy density functional of the isospin symmetry breaking terms using density distributions.

Speaker: Dr Tomoya Naito (RIKEN iTHEMS)

20241031_Tohoku_final.pdf

38 Neutron distribution in unstable nuclei observed through low energy electron scattering

In nuclear physics, electron scattering has been considered for studying proton distributions of nuclei so far.

I would like to talk about the investigation of the neutron distribution by electron scattering, in particular, focusing on unstable nuclei which will be done in future by low energy electron scattering.

Speaker: Dr TOSHIO SUZUKI (RARiS, Tohoku University)

final41031LEES2024.pptx

10:00 AM Caffe break

Session

39 Nuclear equation of state from terrestrial experiments and astrophysical observations

Using the relativistic mean-field model with the isoscalar- and isovector-meson mixing, we consider a new nuclear equation of state, which satisfies the large neutron skin thickness of Pb208 and the small neutron-star radius, respectively reported by the PREX-2 experiment and the NICER observation. We study the effects of scalar-isovector meson and its mixing on the properties of asymmetric-nuclear matter, finite nuclei, and neutron-star matter, focusing on the density dependence of nuclear symmetry energy. It is found that the nuclear symmetry energy becomes soft around twice the nuclear saturation density due to the scalar-meson mixing, and thus, it is possible to explain the PREX-2 data and the astrophysical results from NICER and GW170817 simultaneously. In addition, we discuss the result of the neutron skin thickness of Ca48 from CREX experiment.

Speaker: Dr Tsuyoshi Miyatsu (Soongsil University)

LEES2024.T.Miyatsu.pdf

40 Ab initio calculaitons for medium-mass nuclei and electromagnetic observable

The electron-nucleus scattering provides us with one of the clearest ways to investigate nuclear structure. The scattering cross is factorized as a product of the leptonic and nuclear parts. The nuclear part can be computed from the nuclear vector current operators. With chiral effective field theory, the current operators can also be derived systematically, the same as the nuclear interactions. With polynomially scaling many-body methods such as the coupled-cluster method and in-medium similarity renormalization group approach, ab initio calculations of medium-mass nuclei are becoming possible. In this talk, I will present the computed results of radii and the effect of the two-body current on magnetic observables for medium-mass nuclei.

Speaker: Takayuki Miyagi (University of Tsukuba)

miyagi_20241031.pdf

41 Ab initio nuclear densities from low-resolution interactions

The description of atomic nuclei based on ab initio methods that treat all nucleons as active has known tremendous progress over the past decades. In particular, the progress in interactions based on chiral effective field theory has lead to a more accurate description of bulk properties of nuclei such as density profiles and radii. In this talk, I will discuss recent developments that improved our reproduction of density profiles for scattering experiments and highlight results for physics cases ranging from Argon to the Tin and Xenon isotopic chains.

Speaker: Pierre Arthuis (IJCLab Orsay, CNRS, France)

Arthuis_Sendai_2024.pdf

12:00 PM Lunch

Session

42 Status and prospects of the MUSE project at PSI

Inspired by the proton radius puzzle, the MUon Scattering Experiment (MUSE) at Paul Scherrer Institute (PSI) in Villigen, Switzerland, was introduced to provide new information by simultaneously measuring elastic scattering of electrons and muons, as well as positrons and antimuons from a liquid hydrogen target. MUSE aims to provide precise cross sections with extractions of the electric form factor and charge radius for each of the four beam leptons, while addressing the issues of two-photon exchange and lepton universality through charge and species ratios, respectively. An overview of this experiment and the current status and outlook of the analysis will be presented. This material is based upon the work supported by the National Science Foundation (NSF) under award PHY-2113436. The MUSE experiment is supported by the Department of Energy (DOE), NSF, PSI, and the US-Israel Binational Science Foundation (BSF).

Speaker: Prof. Michael Kohl (Hampton University)

Talk_MUSE_LEES2024_MichaelKohl.pdf

43 The Proton Radius Measurement of AMBER at CERN

The AMBER collaboration at CERN plans to measure muon-proton scattering at low momentum transfer, allowing for a precision determination of the proton charge radius. A muon beam of 100 GeV will impact on a pressurized hydrogen target, which serves at the same time as detector of the recoiling protons. The high beam energy allows for small systematic corrections, with strongly forward-boosted kinematics and suppressed muon decays. With several new detectors currently being commissioned, the first measurement is planned in 2025.

Speaker: Dr Jan Friedrich (Technical University of Munich)

2024-10-31-AMBER-PRM.pdf

3:30 PM Caffe break

Session

44 NNLO QED with McMule for lepton-nucleus scattering at ULQ2

Precise lepton-proton (l-P) scattering experiments need similarly precise theory predictions. It is now possible to model electron-proton scattering at next-to-next-to-leading order (NNLO) in QED. These corrections can be similar in size or even larger than contributions that probe more in depth the nuclear structure, e.g. two-photon exchange corrections. Hence both kinds of contributions need to be brought under control. In this talk I will introduce the McMule framework for NNLO QED calculations and explain the theory background that is required to use it in the context of l-P scattering. I will then present results for the ULQ2 experiment, including an extension of the framework, where P can be any nucleus with a definite spin, e.g. carbon or deuteron, in the one-photon exchange approximation.

Speaker: Marco Rocco (Paul Scherrer Institut / Università di Torino)

rocco-lees24.pdf

45 Electromagnetic structure of light nuclei from chiral EFT

I will describe our recent and ongoing work towards high-accuracy calculations of the electromagnetic form factors of light nuclei in the framework of chiral EFT.

Speaker: Prof. Evgeny Epelbaum (Ruhr University Bochum)

LEES2024_Epelbaum.pdf

Banquet

Friday, November 1

8:30 AM Bus (Katahira to RARiS)

Introduction of RARiS

Session

46 Charge Radii and Neutron Skin Thickness of Unstable Nuclei

Recent experiments using advanced laser spectroscopy technique revealed that the charge radii of neutron-deficient gold (Au), Hg and Pb isotopes exhibit significant changes in ground state deformation: odd-even shape staggering in the N = 98 ∼ 100 region and abrupt change of charge radii from N =108. In this study, we examine the abnormal shape evolution of the nuclear charge radii. We use many different DFT theories. The significant change in mean-squared charge radii (δ< r2 >) turns out to originate from nuclear shape transitions between prolate deformation and small oblate deformation due to the shape coexistence possibility. We elucidate the nuclear shape evolution by analyzing the evolution of occupation probability for single-particle states.

Speaker: Prof. Myung-Ki Cheoun (Soongsil University)

47 (Tentative) Charge symmetry breaking effects with omega-rho_0 mixing

Charge symmetry breaking (CSB) of nuclear force is a key for a precise description of masses of normal nuclei and hypernuclei. In this work, I introduce the CSB effect by omega-rho_0 meson mixing term, which describes a part of CSB effects in nucleon-nucleon and nucleon-hyperon interactions in a unified way, in a framework of relativistic mean-field model. I will discuss the effects of the omega-rho0 mixing on nuclear mass and charge radius.

Speaker: Dr Yusuke Tanimura (Soongsil University)

10:30 AM Caffe break

Session

48 Deduction of matter and charge radii of unstable nuclei via interaction and charge-changing cross sections

The interaction cross section is one of the measurements from which the matter radii of nuclei can be derived. It can be applied to unstable nuclei very far from the stability line due to the large cross section and the ability to thick targets. It has contributed to the discovery of exotic halo structures, skin structures and new magic numbers of unstable nuclei. On the other hand, it has recently been found that the charge-change cross section measurements can be used to derive the charge radii. We have indicated that it is important to take into account proton evaporation effects in this derivation method. To apply these measurements to many nuclei, we have started the S3CAN (Symbiotic Systematic and Simultaneous Cross-section measurements for All over the Nuclear Chart) experiment as part of the TRIP project in RIKEN. In this presentation, we will discuss the experimental methods for cross-section measurements, the latest experimental results and future plans.

Speaker: Dr Daiki Nishimura (Tokyo City University)

DNishimura_LEES2024.pdf

49 Proton and Neutron density distributions measured by intermediate energy proton elastic scattering

Proton elastic scattering at 197 MeV and 295 MeV from 90,92, 94 Zirconium were measured at RCNP Osaka Univ. . By analyzing double energy data we have succeeded to extract proton and neutron density distributions separately using medium modified RIA. Point proton densities obtained by proton scattering are compared with the results obtained by electro-magnetic probes.

Speaker: Dr Harutaka Sakaguchi (RCNP, Osaka University)

50 The ESPRI project

Baryon density distribution is a fundamental information to understand the nuclear many body system. The ESPRI project is aimed at investigating the density distributions of not only stable but also unstalbe nuclei by using proton elastic scattering. Recent status and future plans of the project will be reported.

Speaker: Dr Juzo Zenihiro (Department of Physics, Kyoto University)

12:30 PM Lunch

Session

51 Nuclear contacts of unstable nuclei

Nuclear contact is a key quantity to describe the nucleon-nucleon short-range correlations (SRCs). While they have been determined by electron scattering experiments for selected stable nuclei, nuclear contacts are largely unknown for unstable nuclei. In this work, we study nuclear contacts for a number of nuclei in the vicinity of the doubly magic 132Sn from the theoretical perspective, with special emphasis on unstable nuclei. We find that the proton-proton contact generally gets suppressed by the excess neutrons for the Sn isotopes, resembling the suppression of α-cluster formation reported recently for the same isotopic chain [J. Tanaka et al., Science 371, 260 (2021)]. This might suggest a hidden universal aspect of SRCs and α clustering, two different kinds of nuclear correlations. Moreover, we reveal a model-independent correlation between the proton-proton contact and the root-mean-square radius of proton density distributions for Sn isotopes. Meanwhile, a linear relation is found between the proton-proton contact and the proton number for the N = 82 isotones. Our results can be helpful for future experimental studies of SRCs in unstable nuclei at advanced facilities worldwide.

Speaker: Mr Tongqi Liang (Tongji University)

52 Coexistence and Interplay between nuclear chirality and octupole correlations

Symmetry and its breaking are of great importance in physics and pervade every area of nature. The interplay between these symmetries is fundamental and of significance. As a many-body quantum system with the wealth of information on symmetries, the atomic nucleus is an ideal laboratory to study the fundamental symmetries breaking and their interplay. The present work provides the first test for chirality in the A ≈ 80 mass region by lifetime measurements, and firstly elucidates the formation of chiral geometry in the presence of the octupole correlations in Br isotopes, leading to the conclusion that the reflection symmetry breaking catalyzes rather than destroys chiral symmetry breaking in nuclear systems.

Speaker: Prof. Chen Liu (Shandong Unversity)

Introduction for RARiS tour

20241101LEES2024_honda.pdf

Closing

53 Closing

Speaker: Toshimi Suda (Research Center for Electron-Photon Science, Tohoku University)

LEESclosing.pdf

2:50 PM Caffe break

RARiS tour

5:00 PM Bus (RARiS to Katahira)