The size of the proton dos Santos, Joaquim M. F; Fernandes, Luis M. P; Liu, Yi-Wei ...
Nature (London),
07/2010, Letnik:
466, Številka:
7303
Journal Article
Recenzirano
The proton is the primary building block of the visible Universe, but many of its properties—such as its charge radius and its anomalous magnetic moment—are not well understood. The root-mean-square ...charge radius, rp, has been determined with an accuracy of 2 per cent (at best) by electron–proton scattering experiments. The present most accurate value of rp (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants. This value is based mainly on precision spectroscopy of atomic hydrogen and calculations of bound-state quantum electrodynamics (QED; refs 8, 9). The accuracy of rp as deduced from electron–proton scattering limits the testing of bound-state QED in atomic hydrogen as well as the determination of the Rydberg constant (currently the most accurately measured fundamental physical constant). An attractive means to improve the accuracy in the measurement of rp is provided by muonic hydrogen (a proton orbited by a negative muon); its much smaller Bohr radius compared to ordinary atomic hydrogen causes enhancement of effects related to the finite size of the proton. In particular, the Lamb shift (the energy difference between the 2S1/2 and 2P1/2 states) is affected by as much as 2 per cent. Here we use pulsed laser spectroscopy to measure a muonic Lamb shift of 49,881.88(76) GHz. On the basis of present calculations of fine and hyperfine splittings and QED terms, we find rp = 0.84184(67) fm, which differs by 5.0 standard deviations from the CODATA value of 0.8768(69) fm. Our result implies that either the Rydberg constant has to be shifted by −110 kHz/c (4.9 standard deviations), or the calculations of the QED effects in atomic hydrogen or muonic hydrogen atoms are insufficient.
1 Department of Internal Medicine, Diabetes, and Metabolism, Medical University Graz, 2 Institute of Medical Technologies and Health Management, Joanneum Research, and 3 Department of Biophysics, ...Institute of Biomedical Engineering, Graz University of Technology, Graz, Austria
Submitted 10 September 2004
; accepted in final form 7 March 2005
Insulins action to stimulate glucose utilization is determined by the insulin concentration in interstitial fluid (ISF) of insulin-sensitive tissues. The concentration of interstitial insulin has been measured in human subcutaneous adipose tissue and skeletal muscle, however, never in parallel. The aim of this study was to compare interstitial insulin levels between both tissue beds by simultaneous measurements and to verify and quantify low peripheral ISF insulin fractions as found during moderate hyperinsulinemia. Nine healthy subjects (27.2 ± 0.8 yr) were investigated. A euglycemic-hyperinsulinemic clamp was started with a primed-constant intravenous insulin infusion of 1 mU·kg 1 ·min 1 . For direct access to ISF, macroscopically perforated open-flow microperfusion catheters were inserted in both tissues. During steady-state conditions (9.5 h), interstitial effluents were collected in 30-min fractions using five different insulin concentrations in the inflowing perfusates ("no net flux" protocol). Regression analysis of insulin concentrations in perfusates and effluents yielded the relative recovery and the perfusate insulin concentration, which was in equilibrium with the surrounding tissue. Thus, in subcutaneous adipose tissue and skeletal muscle, the mean ISF-to-serum insulin level was calculated as 21.0% 95% confidence interval (CI) 17.524.5 and 26.0% (95% CI 19.132.8; P = 0.14), respectively. Recoveries for insulin averaged 51 and 64%, respectively. The data suggest that the concentrations of insulin arising in healthy subjects at the level of ISF per se are comparable between subcutaneous adipose and skeletal muscle tissue. The low interstitial insulin fractions seem to confirm reports of low peripheral insulin levels during moderate insulin clamps.
extracellular fluid; euglycemic-hyperinsulinemic glucose clamp; open-flow microperfusion; no net flux; equilibrium method
Address for reprint requests and other correspondence: T.R. Pieber, Dept. of Internal Medicine, Medical Univ. Graz, Auenbruggerplatz 15, A-8036 Graz, Austria (e-mail: thomas.pieber{at}meduni-graz.at )
Accurate knowledge of the charge and Zemach radii of the proton is essential, not only for understanding its structure but also as input for tests of bound-state quantum electrodynamics and its ...predictions for the energy levels of hydrogen. These radii may be extracted from the laser spectroscopy of muonic hydrogen (μp, that is, a proton orbited by a muon). We measured the $2{\mathrm{S}}_{1/2}^{\mathrm{F}=0}-2{\mathrm{P}}_{3/2}^{\mathrm{F}=1}$ transition frequency in μp to be 54611.16(1.05) gigahertz (numbers in parentheses indicate one standard deviation of uncertainty) and reevaluated the $2{\mathrm{S}}_{1/2}^{\mathrm{F}=1}-2{\mathrm{P}}_{3/2}^{\mathrm{F}=1}$ transition frequency, yielding 49881.35(65) gigahertz. From the measurements, we determined the Zemach radius, r Z = 1.082(37) femtometers, and the magnetic radius, r M = 0.87(6) femtometer, of the proton. We also extracted the charge radius, r E = 0.84087(39) femtometer, with an order of magnitude more precision than the 2010-CODATA value and at 7σ variance with respect to it, thus reinforcing the proton radius puzzle.
Laser spectroscopy of muonic hydrogen Pohl, Randolf; Antognini, Aldo; Amaro, Fernando D. ...
Annalen der Physik,
09/2013, Letnik:
525, Številka:
8-9
Journal Article
Recenzirano
Odprti dostop
Muonic hydrogen (μp) is a very sensitive probe of the proton structure. Laser spectroscopy of two 2S‐2P transitions in μp was used to determine both the Lamb shift and the hyperfine splitting of the ...2S state in μp. The rms charge radius of the proton, Rch=0.84087(39) fm, was extracted from the Lamb shift. The Zemach radius of the proton, RZ=1.082(37) fm, was obtained from the 2S‐hyperfine splitting. This article summarizes the previously published findings.
Muonic hydrogen (μp) is a very sensitive probe of the proton structure. Laser spectroscopy of two 2S‐2P transitions in μp was used to determine both the Lamb shift and the hyperfine splitting of the 2S state in μp. The rms charge radius of the proton, Rch = 0.84087(39) fm, was extracted from the Lamb shift. The Zemach radius of the proton, RZ = 1.082(37) fm, was obtained from the 2S‐hyperfine splitting. This article summarizes the previously published findings.
We investigated the dynamic relationship between interstitial glucose (IG) in the subcutaneous adipose tissue and plasma glucose (PG) during physiologic conditions in type 1 diabetes mellitus (T1DM). ...Nine subjects with T1DM (5/4 M/F; age, 33 +/- 13 years; body mass index, 26.6 +/- 4.3 kg/m(2); glycosylated hemoglobin HbA(1c), 8.6% +/- 0.9%; mean +/- SD) treated by continuous subcutaneous insulin infusion (CSII) with insulin lispro were studied over 12 hours after a standard meal (40 g carbohydrate CHO) and prandial insulin. IG was measured by open flow microperfusion. Nine compartment models were postulated to account for temporal variations in the IG/PG ratio. The models differed in the inclusion of physiologically motivated alterations of pathways entering/leaving the IG compartment in the adipose tissue. The best model included zero order (constant) glucose disposal from the interstitial fluid (ISF) and insulin-stimulated glucose transfer from plasma to the ISF. The former effect is expressed by a positive association between the IG/PG ratio and PG, eg, a decrease in PG from 9 to 3.3 mmol/L lowers the IG/PG ratio by 0.1. The latter effect results in the IG/PG ratio to be increased by 0.03 per 10 mU/L of plasma insulin. We were not able to detect the stimulatory effect of insulin on glucose disappearance from the ISF. In conclusion, we developed and quantified a model of IG kinetics in the adipose tissue applicable to physiologic conditions in subjects with T1DM.
The size of the proton and the deuteron Pohl, Randolf; Amaro, Fernando D; Antognini, Aldo ...
Journal of physics. Conference series,
01/2011, Letnik:
264, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We have recently measured the 2S1/2F=1 − 2P3/2F 2 energy splitting in the muonic hydrogen atom μp to be 49881.88 (76) GHz. Using recent QED calculations of the fine-, hyperfine, QED and finite size ...contributions we obtain a root-mean-square proton charge radius of rp 0.84184 (67) fm. This value is ten times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of rp 0.8768 (69) fm. The source of this discrepancy is unknown. Using the precise measurements of the 1S-2S transition in regular hydrogen and deuterium and our value of rp we obtain improved values of the Rydberg constant, R 10973731.568160 (16) m−1and the rms charge radius of the deuteron rd 2.12809 (31) fm.
The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the
2S
1/2
F=1
-2P
3/2
F=2
energy splitting (Pohl et al., Nature,
466
, 213 (2010)) in μp with an ...experimental accuracy of 15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a root-mean-square proton charge radius of r
p
= 0.841 84 (67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of r
p
. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S-2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R
∞
= 10 973 731.568 160 (16) m
-1
and the rms charge radius of the deuteron r
d
= 2.128 09 (31) fm.
The Lamb shift in muonic hydrogen Pohl, Randolf; Antognini, Aldo; Nez, Francois ...
Canadian journal of physics,
01/2011, Letnik:
89, Številka:
1
Journal Article
Recenzirano
The long quest for a measurement of the Lamb shift in muonic hydrogen is over. Last year we measured the energy splitting (Pohl et al., Nature, 466, 213 (2010)) in μp with an experimental accuracy of ...15 ppm, twice better than our proposed goal. Using current QED calculations of the fine, hyperfine, QED, and finite size contributions, we obtain a rootmean-square proton charge radius of r.sub.p = 0.841 84(67) fm. This value is 10 times more precise, but 5 standard deviations smaller, than the 2006 CODATA value of r.sub.p. The origin of this discrepancy is not known. Our measurement, together with precise measurements of the 1S--2S transition in regular hydrogen and deuterium, gives improved values of the Rydberg constant, R.sub.∞ = 10973 731.568160(16) m.sup.-1 and the rms charge radius of the deuteron r.sub.d = 2.128 09 (31) fm.
The proton radius puzzle Antognini, A; Amaro, F D; Biraben, F ...
Journal of Physics: Conference Series,
09/2011, Letnik:
312, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
By means of pulsed laser spectroscopy applied to muonic hydrogen (μ− p) we have measured the 2SF 11/2 – 2PF 23/2 transition frequency to be 49881.88(76) GHz 1. By comparing this measurement with its ...theoretical prediction 2, 3, 4, 5, 6, 7 based on bound-state QED we have determined a proton radius value of rp 0.84184(67) fm. This new value differs by 5.0 standard deviations from the COD ATA value of 0.8768(69) fm 8, and 3 standard deviation from the e-p scattering results of 0.897(18) fm 9. The observed discrepancy may arise from a computational mistake of the energy levels in μp or H, or a fundamental problem in bound-state QED, an unknown effect related to the proton or the muon, or an experimental error.
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