Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session 4WKA: Recent Progress in Nuclear Physics with Hyperons I
2:00 PM–3:30 PM,
Monday, November 27, 2023
Hilton Waikoloa Village
Room: Kohala 3
Chair: Patrick Achenbach, Jefferson Lab/Jefferson Science Associates
Abstract: 4WKA.00002 : Decay pion spectroscopy of electro-produced light Lambda hypernuclei at MAMI*
2:30 PM–3:00 PM
Presenter:
Ryoko Kino
(Tohoku University)
Authors:
Ryoko Kino
(Tohoku University)
Patrick Achenbach
(Jefferson Lab)
Takeru Akiyama
(Tohoku University)
Ralph Böhm
(FAIR)
Michael O Distler
(Johannes Gutenberg University Mainz)
Philipp Eckert
(Johannes Gutenberg University Mainz)
Anselm Esser
(Johannes Gutenberg University Mainz)
Julian Geratz
(Johannes Gutenberg University Mainz)
Christian Helmel
(Johannes Gutenberg University Mainz)
Matthias Hoek
(Johannes Gutenberg University Mainz)
Tatsuhiro Ishige
(Tohoku University)
Kosuke Itabashi
(QUP, WPI research center at KEK)
Masashi Kaneta
(Tohoku Univ)
Pascal Klag
(Johannes Gutenberg University Mainz)
Harald Merkel
(Johannes Gutenberg University Mainz)
Masaya Mizuno
(Tohoku University)
Ulrich Müller
(Johannes Gutenberg University Mainz)
Sho Nagao
(The University of Tokyo)
Satoshi N Nakamura
(The University of Tokyo)
Kotaro Nishi
(The University of Tokyo)
KAZUKI OKUYAMA
(Tohoku University)
Josef Pochodzalla
(Johannes Gutenberg University Mainz)
Tianhao Shao
(Fudan University)
Björn Sören Schlimme
(Johannes Gutenberg University Mainz)
Marcell Steinen
(Helmholtz Institute Mainz, GSI Helmholtzzentrum für Schwerionenforschung)
Koga Tachibana
(Tohoku University)
Michaela Thiel
(Johannes Gutenberg University Mainz)
Yuichi Toyama
(Chubu University)
Keita Uehara
(Tohoku University)
Daigo Watanabe
(Tohoku University)
Collaboration:
A1 hypernuclear collaboration
After 2010, the STAR and ALICE collaborations reported a 20-30% shorter lifetime for 3ΛH. These groups also reported binding energies of BΛ = 406 ± 120(stat.) ± 110(syst.) keV and preliminarily BΛ = 102 ± 63(stat.) ± 67(syst.) keV, respectively. For understanding the correlation between hypertriton's lifetime and binding energy, accurate measurement of these values is crucial.
In October 2022, we conducted decay-pion spectroscopy experiments on s-shell hypernuclei (3ΛH and 4ΛH) at Mainz Microtron (MAMI). Some electro-produced hypernuclei form bound states and decay via two-body weak decay, emitting pions with monochromatic momentum. By measuring this momentum with high-resolution magnetic spectrometers (Δp/p ~ 10-4) and combining it with a Kaon spectrometer to tag strangeness production and suppress background events, we successfully measured the 4ΛH mass with an accuracy of 80 keV in 2014.
In 2022, to enhance the yield of 3ΛH and reduce background events, we changed the target from 9Be to 7Li in this experiment. The 7Li target was positioned at a 90-degree angle to increase luminosity and mitigate the effects of the pion energy struggle. Additionally, we introduced a new technology for beam energy measurement to achieve hypernuclear mass determination with 10-20 keV accuracy.
In this presentation, I will discuss this experimental method and provide an update on the latest analysis.
*This work is supported by JSPS KAKENHI (Grant No. JP18H05459, 20H01926, 23KJ0180), GP-PU Tohoku University, the DFG (Grant No. PO256/7-1), and the EU Horizon 2020 R&I program No. 824093. Two of the authors (R. Kino and K. Okuyama) are JSPS research fellowships.
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