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SUMMARY:Precise measurement of the hyperfine splitting in muonium with a h
 igh intensity pulsed muon beam at J-PARC
DTSTART;VALUE=DATE-TIME:20220829T164000Z
DTEND;VALUE=DATE-TIME:20220829T170000Z
DTSTAMP;VALUE=DATE-TIME:20220826T110408Z
UID:indico-contribution-3793@indico.stfc.ac.uk
DESCRIPTION:Speakers: Ryoto Iwai (KEK)\nA muonium is a purely leptonic bou
 nd system of a positive muon and an electron.\nFundamental properties of s
 uch a system can be precisely predicted by the QED\, whereas ordinal atoms
  require to calculate hadronic interactions.\n\nAt J-PARC\, the MuSEUM (Mu
 onium Spectroscopy Experiment Using Microwave) collaboration aims to preci
 sely measure the ground-state hyperfine splitting of muonium atoms\, arisi
 ng from spins of the muon and electron.\nThe pulsed muon beam is stopped i
 n a krypton gas cell to form the muonium atoms.\nThe transitions of spin s
 tates are induced with a microwave cavity\, which is then measured by posi
 tron counters. \n\nIn previously performed measurement with a nearly-zero 
 magnetic field [1\,2]\, the resonance of the hyperfine transition was succ
 essfully observed with a relative precision of 160 ppb.\nAs a next step\, 
 we plan to perform the measurements with strong magnetic fields\, so that 
 the different frequency shifts by Zeeman splitting allow us to more precis
 ely determine the transition rate down to 1.2 ppb.\nThis unprecedented pre
 cision will be achieved by upgrading several components of the experimenta
 l setup\, including a new high intensity muon beamline which is currently 
 commissioned at J-PARC.\nPerforming measurements at various magnetic field
  strengths requires to replace the current cylindrical microwave cavity wi
 th a new boxed-shaped cavity.\n\nIn this presentation\, the general scheme
  of our experiment and status of the upgrades for the new measurement are 
 reported.\n\n[1] S. Kanda et al.\, Phys. Lett. B 815\, 136154 (2021).\n[2]
  S. Nishimura et al.\, Phys. Rev. A 104\, L020801 (2021).\n\nhttps://indic
 o.stfc.ac.uk/event/53/contributions/3793/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3793/
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