Laser spectroscopy of muonic deuterium

Abstract

The deuteron is the simplest compound nucleus, composed of one proton and one neutron. Deuteron properties such as the root-mean-square charge radius rd and the polarizability serve as important benchmarks for understanding the nuclear forces and structure. Muonic deuterium μd is the exotic atom formed by a deuteron and a negative muon μ(-). We measured three 2S-2P transitions in μd and obtain r(d) = 2.12562(78) fm, which is 2.7 times more accurate but 7.5σ smaller than the CODATA-2010 value r(d) = 2.1424(21) fm. The μd value is also 3.5σ smaller than the r(d) value from electronic deuterium spectroscopy. The smaller r(d), when combined with the electronic isotope shift, yields a "small" proton radius r(p), similar to the one from muonic hydrogen, amplifying the proton radius puzzle.

Lamb shift in muonic ions of lithium, beryllium, and boron

“…Thus, with proper experimental accuracy we can obtain more precise values of the nuclear charge radii. 4 in the second order PT Three-loop VP contribution in the 0.08 0.08 second order PT of order α 3 (Zα) 2 Three-loop VP contribution 0.04 0.05 in the third order PT of order α 3 (Zα) 2 Relativistic and two-loop VP 0.15 0.15 corrections of order α 2 (Zα) 4 in the second order PT Nuclear structure contribution of order (Zα) 4 −3301 ± 117 −3675 ± 112 Nuclear structure contribution 177 ± 9 208 ± 9 of order (Zα) 5 from 2γ amplitudes Nuclear structure and VP contribution -12.78 -14.21 in 1γ interaction of order α(Zα) 4 Nuclear structure and VP contribution -20.68 -23.00 in the second order PT of order α(Zα) 4 4 in the second order PT Nuclear structure contribution of order (Zα) 4 −9826 ± 142 −11200 ± 107 Nuclear structure contribution 679 ± 14 826 ± 12 of order (Zα) 5 4 in the second order PT Three-loop VP contribution in the 0.35 0.35 second order PT of order α 3 (Zα) 2 Three-loop VP contribution 0.31 0.31 in the third order PT of order α 3 (Zα) 2 Relativistic and two-loop VP 1.44 1.44 corrections of order α 2 (Zα) 4 in the second order PT Nuclear structure contribution of order (Zα) 4 −25115 ± 618 −25493 ± 1059 Nuclear structure contribution 2217 ± 82 2269 ± 143 of order (Zα) 5 from 2γ amplitudes Nuclear structure and VP contribution -117.14 -118.86 in 1γ interaction of order α(Zα) 4 Nuclear structure and VP contribution -200.06 -202.98 in the second order PT of order α(Zα) 4 …”

“…The subsequent in 2010 year measurement of the Lamb shift in muonic hydrogen has led to another problem, called the proton charge radius puzzle [1][2][3][4]. After a new measurement of the Lamb shift [5] in muonic deuterium it became clear that there is a discrepancy in the values of the charge radius of the proton and deuteron determined by electronic and muonic atoms. This may mean that the muons are playing an important role in subatomic physics, which is not fully understood.…”

Measuring the Rydberg constant using circular Rydberg atoms in an intensity-modulated optical lattice

“…More recently, the large discrepancies in the proton [1,2] and deuteron [3] radii that were found using muonic hydrogen and deuterium, respectively, have reinforced the need to confirm the accuracy of R ∞ . Previous precision experiments with this goal have involved low-lying states of hydrogen, limited typically by statistical uncertainties, AC Stark shifts and second-order Doppler shifts [4].…”

High-accuracy deep-UV Ramsey-comb spectroscopy in krypton

“…This mismatch, known as the proton radius puzzle, remains to be explained and requires more spectroscopic measurements, e.g., in systems other than (muonic) hydrogen. Recent results on muonic deuterium [14] reveal that also the deuteron radius is significantly smaller (7.5 σ) than the radius based on normal deuterium spectroscopy.Interesting candidates for precision spectroscopy to solve this puzzle need to be sufficiently simple for precise theoretical treatment. One example is molecular hydrogen, made possible by recent improvements in theory [15].…”

“…This mismatch, known as the proton radius puzzle, remains to be explained and requires more spectroscopic measurements, e.g., in systems other than (muonic) hydrogen. Recent results on muonic deuterium [14] reveal that also the deuteron radius is significantly smaller (7.5 σ) than the radius based on normal deuterium spectroscopy.…”