scholarly journals New precise measurements of muonium hyperfine structure at J-PARC MUSE

2019 ◽  
Vol 198 ◽  
pp. 00003 ◽  
Author(s):  
P. Strasser ◽  
M. Abe ◽  
M. Aoki ◽  
S. Choi ◽  
Y. Fukao ◽  
...  
Keyword(s):  
Hyperfine Structure ◽  
Quantum Electrodynamics ◽  
Field Measurements ◽  
Bound State ◽  
New Physics ◽  
Muon Beam ◽  
Current Status ◽  
Zero Field ◽  
Order Of Magnitude ◽  
Muon Magnetic Moment

High precision measurements of the ground state hyperfine structure (HFS) of muonium is a stringent tool for testing bound-state quantum electrodynamics (QED) theory, determining fundamental constants of the muon magnetic moment and mass, and searches for new physics. Muonium is the most suitable system to test QED because both theoretical and experimental values can be precisely determined. Previous measurements were performed decades ago at LAMPF with uncertainties mostly dominated by statistical errors. At the J-PARC Muon Science Facility (MUSE), the MuSEUM collaboration is planning complementary measurements of muonium HFS both at zero and high magnetic field. The new high-intensity muon beam that will soon be available at H-Line will provide an opportunity to improve the precision of these measurements by one order of magnitude. An overview of the different aspects of these new muonium HFS measurements, the current status of the preparation for high-field measurements, and the latest results at zero field are presented.

New Experiment for the First Direct Measurement of Positronium Hyperfine Splitting with Sub-THz Light

2010 ◽  
Vol 666 ◽  
pp. 133-137 ◽  
Author(s):  
Akira Miyazaki ◽  
Takayuki Yamazaki ◽  
Taikan Suehara ◽  
Toshio Namba ◽  
Shoji Asai ◽  
...  
Keyword(s):  
Present Status ◽  
Quantum Electrodynamics ◽  
Hyperfine Splitting ◽  
Radiation Power ◽  
Bound State ◽  
New Physics ◽  
Ideal System ◽  
Fabry Perot ◽  
Current Design ◽  
High Finesse

Positronium is an ideal system for the research of Quantum Electrodynamics (QED), especially for QED in bound state. The discrepancy of 3.9σ was found recently between the measured HFS values and the QED prediction of O(α3). It might be due to the contribution of unknown new physics or systematic problems in the all previous measurements. We propose a new method to measure HFS directly and precisely. A gyrotron, a novel sub-THz light source is adopted with a Fabry-Pérot cavity with high finesse and an efficient transportation system in order to obtain sufficient radiation power at 203 GHz. The present status of the optimization studies and the current design of the experiment are described.

scholarly journals Observation of the hyperfine spectrum of antihydrogen

Nature ◽  
2017 ◽  
Vol 548 (7665) ◽  
pp. 66-69 ◽  
Author(s):  
M. Ahmadi ◽  
B. X. R. Alves ◽  
C. J. Baker ◽  
W. Bertsche ◽  
E. Butler ◽  
...  
Keyword(s):  
Hyperfine Structure ◽  
Quantum Electrodynamics ◽  
Atomic Hydrogen ◽  
Zero Field ◽  
Detection Techniques ◽  
Long Baseline ◽  
Systems Research ◽  
Field Independent ◽  
Spectroscopy Experiment ◽  
Charge Parity

Abstract The observation of hyperfine structure in atomic hydrogen by Rabi and co-workers1,2,3 and the measurement4 of the zero-field ground-state splitting at the level of seven parts in 1013 are important achievements of mid-twentieth-century physics. The work that led to these achievements also provided the first evidence for the anomalous magnetic moment of the electron5,6,7,8, inspired Schwinger’s relativistic theory of quantum electrodynamics9,10 and gave rise to the hydrogen maser11, which is a critical component of modern navigation, geo-positioning and very-long-baseline interferometry systems. Research at the Antiproton Decelerator at CERN by the ALPHA collaboration extends these enquiries into the antimatter sector. Recently, tools have been developed that enable studies of the hyperfine structure of antihydrogen12—the antimatter counterpart of hydrogen. The goal of such studies is to search for any differences that might exist between this archetypal pair of atoms, and thereby to test the fundamental principles on which quantum field theory is constructed. Magnetic trapping of antihydrogen atoms13,14 provides a means of studying them by combining electromagnetic interaction with detection techniques that are unique to antimatter12,15. Here we report the results of a microwave spectroscopy experiment in which we probe the response of antihydrogen over a controlled range of frequencies. The data reveal clear and distinct signatures of two allowed transitions, from which we obtain a direct, magnetic-field-independent measurement of the hyperfine splitting. From a set of trials involving 194 detected atoms, we determine a splitting of 1,420.4 ± 0.5 megahertz, consistent with expectations for atomic hydrogen at the level of four parts in 104. This observation of the detailed behaviour of a quantum transition in an atom of antihydrogen exemplifies tests of fundamental symmetries such as charge–parity–time in antimatter, and the techniques developed here will enable more-precise such tests.

scholarly journals Towards a New μ→eγ Search with the MEG II Experiment: From Design to Commissioning

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 466
Author(s):  
Marco Chiappini ◽  
Marco Francesconi ◽  
Satoru Kobayashi ◽  
Manuel Meucci ◽  
Rina Onda ◽  
...  
Keyword(s):  
State Of The Art ◽  
New Physics ◽  
Muon Beam ◽  
Current Status ◽  
Beyond The Standard Model ◽  
Experimental Apparatus ◽  
The Standard Model ◽  
Sensitivity Level ◽  
Paul Scherrer ◽  
Lepton Flavour

The MEG experiment represents the state of the art in the search for the Charged Lepton Flavour Violating μ+→e+γ decay. With its first phase of operations at the Paul Scherrer Institut (PSI), MEG set the most stringent upper limit on the BR (μ+→e+γ)≤4.2×10−13 at 90% confidence level, imposing one of the tightest constraints on models predicting LFV-enhancements through new physics beyond the Standard Model. An upgrade of the MEG experiment, MEG II, was designed and it is presently in the commissioning phase, aiming at a sensitivity level of 6×10−14. The MEG II experiment relies on a series of upgrades, which include an improvement of the photon detector resolutions, brand new detectors on the positron side with better acceptance, efficiency and performances and new and optimized trigger and DAQ electronics to exploit a muon beam intensity twice as high as that of MEG (7×107 μ+/s). This paper presents a complete overview of the MEG II experimental apparatus and the current status of the detector commissioning in view of the physics data taking in the upcoming three years.

scholarly journals On μe-scattering at NNLO in QED

2018 ◽  
Vol 179 ◽  
pp. 01014 ◽  
Author(s):  
P. Mastrolia ◽  
M. Passera ◽  
A. Primo ◽  
U. Schubert ◽  
W. J. Torres Bobadilla
Keyword(s):  
Quantum Electrodynamics ◽  
State Of The Art ◽  
Current Status ◽  
Analytic Evaluation ◽  
Art Techniques

We report on the current status of the analytic evaluation of the two-loop corrections to the μescattering in Quantum Electrodynamics, presenting state-of-the art techniques which have been developed to address this challenging task.

scholarly journals The history of the muon (g-2) experiments

2019 ◽  
Author(s):  
B. Lee Roberts
Keyword(s):  
Standard Model ◽  
Quantum Electrodynamics ◽  
National Laboratory ◽  
New Physics ◽  
Brookhaven National Laboratory ◽  
Muon Decay ◽  
Higgs Bosons ◽  
The Standard Model ◽  
History Of ◽  
First Time

I discuss the history of the muon (g-2)(g−2) measurements, beginning with the Columbia-Nevis measurement that observed parity violation in muon decay, and also measured the muon gg-factor for the first time, finding g_\mu=2gμ=2. The theoretical (Standard Model) value contains contributions from quantum electrodynamics, the strong interaction through hadronic vacuum polarization and hadronic light-by-light loops, as well as the electroweak contributions from the WW, ZZ and Higgs bosons. The subsequent experiments, first at Nevis and then with increasing precision at CERN, measured the muon anomaly a_\mu = (g_\mu-2)/2aμ=(gμ−2)/2 down to a precision of 7.3 parts per million (ppm). The Brookhaven National Laboratory experiment E821 increased the precision to 0.54 ppm, and observed for the first time the electroweak contributions. Interestingly, the value of a_\muaμ measured at Brookhaven appears to be larger than the Standard Model value by greater than three standard deviations. A new experiment, Fermilab E989, aims to improve on the precision by a factor of four, to clarify whether this result is a harbinger of new physics entering through loops, or from some experimental, statistical or systematic issue.

scholarly journals Review of strongly-coupled composite dark matter models and lattice simulations

2016 ◽  
Vol 31 (22) ◽  
pp. 1643004 ◽  
Author(s):  
Graham D. Kribs ◽  
Ethan T. Neil
Keyword(s):  
Dark Matter ◽  
Gauge Theory ◽  
Direct Detection ◽  
Bound State ◽  
New Physics ◽  
Abelian Gauge ◽  
Strongly Coupled ◽  
Abelian Gauge Theory ◽  
Lattice Calculations ◽  
Composite Description

We review models of new physics in which dark matter arises as a composite bound state from a confining strongly-coupled non-Abelian gauge theory. We discuss several qualitatively distinct classes of composite candidates, including dark mesons, dark baryons, and dark glueballs. We highlight some of the promising strategies for direct detection, especially through dark moments, using the symmetries and properties of the composite description to identify the operators that dominate the interactions of dark matter with matter, as well as dark matter self-interactions. We briefly discuss the implications of these theories at colliders, especially the (potentially novel) phenomenology of dark mesons in various regimes of the models. Throughout the review, we highlight the use of lattice calculations in the study of these strongly-coupled theories, to obtain precise quantitative predictions and new insights into the dynamics.

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