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Proton spin crisis

About: Proton spin crisis is a research topic. Over the lifetime, 1608 publications have been published within this topic receiving 29191 citations.


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Journal ArticleDOI
S. D. Bass1
TL;DR: In this paper, the authors review the theory and present status of the proton spin problem with emphasis on the transition between current quarks and constituent quarks in QCD, and propose a solution to the problem.
Abstract: We review the theory and present status of the proton spin problem with emphasis on the transition between current quarks and constituent quarks in QCD.

1,207 citations

Journal ArticleDOI
TL;DR: In this paper, an exchange interaction between the electron spin and proton spin in adjacent water molecules in paramagnetic solutions was proposed, and an explanation was given why T1/T2 for protons is much larger than unity in solutions of these particular ions in high magnetic fields, whereas T1 is about equal to T2 in other solutions or in low fields.
Abstract: An exchange interaction is postulated between the electron spin and proton spin in adjacent water‐molecules in paramagnetic solutions. In combination with the long electron spin relaxation times for Mn++ and Gd+++, an explanation is given why T1/T2 for protons is much larger than unity in solutions of these particular ions in high magnetic fields, whereas T1 is about equal to T2 in other solutions or in low fields.

1,027 citations

Journal ArticleDOI
TL;DR: The anomalous magnetic moment of the negative muon has been measured to a precision of 0.7 ppm (ppm) at the Brookhaven Alternating Gradient Synchrotron, and is over an order of magnitude more precise than the previous measurement.
Abstract: We present the first results of the Fermilab National Accelerator Laboratory (FNAL) Muon g-2 Experiment for the positive muon magnetic anomaly a_{μ}≡(g_{μ}-2)/2. The anomaly is determined from the precision measurements of two angular frequencies. Intensity variation of high-energy positrons from muon decays directly encodes the difference frequency ω_{a} between the spin-precession and cyclotron frequencies for polarized muons in a magnetic storage ring. The storage ring magnetic field is measured using nuclear magnetic resonance probes calibrated in terms of the equivalent proton spin precession frequency ω[over ˜]_{p}^{'} in a spherical water sample at 34.7 °C. The ratio ω_{a}/ω[over ˜]_{p}^{'}, together with known fundamental constants, determines a_{μ}(FNAL)=116 592 040(54)×10^{-11} (0.46 ppm). The result is 3.3 standard deviations greater than the standard model prediction and is in excellent agreement with the previous Brookhaven National Laboratory (BNL) E821 measurement. After combination with previous measurements of both μ^{+} and μ^{-}, the new experimental average of a_{μ}(Exp)=116 592 061(41)×10^{-11} (0.35 ppm) increases the tension between experiment and theory to 4.2 standard deviations.

932 citations

Journal ArticleDOI
01 Feb 2013-Science
TL;DR: It is shown that the NV center senses the nanotesla field fluctuations from the protons, enabling both time-domain and spectroscopic NMR measurements on the nanometer scale.
Abstract: Extension of nuclear magnetic resonance (NMR) to nanoscale samples has been a longstanding challenge because of the insensitivity of conventional detection methods. We demonstrated the use of an individual, near-surface nitrogen-vacancy (NV) center in diamond as a sensor to detect proton NMR in an organic sample located external to the diamond. Using a combination of electron spin echoes and proton spin manipulation, we showed that the NV center senses the nanotesla field fluctuations from the protons, enabling both time-domain and spectroscopic NMR measurements on the nanometer scale.

727 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231
20229
202115
202016
201920
201827