Showing papers on "Proton spin crisis published in 2000"
TL;DR: In this paper, a method to determine 1H−13C distances r CH with high precision from Lee−Goldburg cross-polarization (LG-CP) with fast MAS and continuous LG decoupling on uniformly 13C-enriched tyrosine·HCl was presented.
Abstract: Magic angle spinning (MAS) NMR structure determination is rapidly developing. We demonstrate a method to determine 1H−13C distances r CH with high precision from Lee−Goldburg cross-polarization (LG-CP) with fast MAS and continuous LG decoupling on uniformly 13C-enriched tyrosine·HCl. The sequence is γ-encoded, and 1H−13C spin-pair interactions are predominantly responsible for the polarization transfer while proton spin diffusion is prevented. When the CP amplitudes are set to a sideband of the Hartmann−Hahn match condition, the LG-CP signal builds up in an oscillatory manner, reflecting coherent heteronuclear transfer. Its Fourier transform yields an effective 13C frequency response that is very sensitive to the surrounding protons. This 13C spectrum can be reproduced in detail with MAS Floquet simulations of the spin cluster, based on the positions of the nuclei from the neutron diffraction structure. It is symmetric around ω = 0 and yields two well-resolved maxima. Measurement of CH distances is straig...
302 citations
TL;DR: In this paper, a review on the theoretical aspects and experimental results of polarized deep inelastic scattering and of other hard scattering processes is presented, with a focus on the first moment of the polarized structure function in various factorization schemes, which is related to the axial anomaly, and on its relevance for understanding the origin of the proton spin.
154 citations
TL;DR: In this paper, double-quantum NMR was applied to two 13 C2-labeled carbohydrate samples, (1,2-13 C2)-glucose and methyl-R-D-(1,3- 13 C 2)-Glucose, in both solution and solid phases.
Abstract: Double-quantum heteronuclear local field NMR was applied to two 13 C2-labeled carbohydrate samples, (1,2- 13 C2)-glucose and methyl-R-D-(1,3- 13 C2)-glucose. The geometry of the H- 13 C- 13 C-H moeity was estimated using the evolution of double-quantum coherences under correlated heteronuclear dipolar interactions. For (1,2- 13 C2)-glucose, double-quantum techniques were used both in solution and solid phases. The measured H-C1-C2-H torsion angles in crystalline glucose were 170° ( 5° for the ‚-anomer and 40° ( 15° for the R-anomer, in good agreement with reported crystal structures. In the solution phase we give a full analysis of an experiment in which the cross-correlation effects are isolated by the use of a heteronuclear multiple-quantum filter. We consider the influence of anisotropic rotational diffusion, chemical shift anisotropy, and proton - proton spin diffusion on the torsion angle estimate. We show that it is possible to determine the torsion angle and the rotational correlation time independently. The measured H-C1-C2-H torsion angles in solution differ slightly from the solid-state results: 159 ° ( 10° for the ‚-anomer and 57° ( 7° for the R-anomer. For methyl-R-D-(1,3- 13 C2)-glucose, the solid phase double-quantum heteronuclear local field experiment was applied for the first time to a HCCH moiety in which the carbons are not directly bonded. These techniques may be applied to other structural problems such as the determination of glycosidic linkage conformations and the conformation of sugar rings in nucleotides.
58 citations
CERN1
TL;DR: The present status of the nucleon's spin structure is reviewed with emphasis on new experimental results in this paper, where the authors propose a new spin structure for nucleon spin spin structure analysis.
Abstract: The present status of the nucleon's spin structure is reviewed with emphasis on new experimental results.
53 citations
TL;DR: In this paper, the quark orbital angular momentum of the nucleon was calculated from quark energy-momentum tensor form factors on the lattice and the disconnected insertion was estimated stochastically which employs the Z{sub 2} noise with an unbiased subtraction.
Abstract: The authors calculate the quark orbital angular momentum of the nucleon from the quark energy-momentum tensor form factors on the lattice. The disconnected insertion is estimated stochastically which employs the Z{sub 2} noise with an unbiased subtraction. This reduced the error by a factor of 4 with negligible overhead. The total quark contribution to the proton spin is found to be 0.30{+-}0.07. From this and the quark spin content the authors deduce the quark orbital angular momentum to be 0.17{+-}0.06 which is {approximately} 34% of the proton spin. The authors further predict that the gluon angular momentum to be 0.20{+-}0.07, i. e. {approximately} 40% of the proton spin is due to the glue.
53 citations
TL;DR: In this article, the angular momentum sum-rule for the proton in terms of matrix elements of three gauge-invariant, local composite operators is decomposed into three independent form factors, one of which is the flavour singlet axial charge.
28 citations
TL;DR: The odderon is a latecomer to the family of Regge poles and, to date, there is not any experimental evidence forit as discussed by the authors. But it is the putative negative charge conjugation partner to the Pomeron, the dominant Regge singularity at high energy.
Abstract: The odderon is a latecomer to the family of Regge polesand, to date, there is not any firm experimental evidence forit. It is the putative negative charge conjugation partner tothe Pomeron, the dominant Regge singularity at high energy.The exact nature of the Pomeron is even now not well un-derstood. Two aspects are virtually certain, almost by defi-nition: ~1! it is a singularity, no doubt more complicated thana simple pole, in the t-channel angular momentum plane thatlies at J51 when the momentum transfer t50, and ~2! it hascharge conjugation C511, signature (21)
16 citations
TL;DR: In this article, a detailed analysis of resonance contributions in the context of higher twist effects in the moments of the proton spin structure function g 1 was presented, and it was found that there exists a characteristic Q 2 region in which (perturbative) higher twist corrections coexist with (non-perturbation) resonance contribution of comparable magnitude.
16 citations
TL;DR: In this article, the temperature dependence of T1 of the proton in the Haldane-gap system TMNIN has been measured with external fields H up to 7.5 T.
Abstract: The temperature dependence of T1 of the proton in the Haldane-gap system TMNIN has been measured with external fields H up to 7.5 T. For H c =2.7 T , the relaxation rate 1/T1 decreases with decreasing temperature. These results have been understood in terms of magnon scattering within each of the Sz=±1 excited states. For H>Hc, on the other hand, 1/T1 exhibits a significant increase below about 3 K, which follows the equation 1/T1∼Tη−1 with η=0.5, suggesting the realization of a Luttinger-liquid state.
11 citations
11 citations
TL;DR: In this paper, the gluon polarization contribution at the quark model renormalization scale to the proton spin, Γ, in the chiral bag model was evaluated by taking the expectation value of the forward matrix element of a local gluons operator in the axial gauge A + = 0.
TL;DR: Solid state proton Zeeman relaxation rate R1z measurements in two isomers of an organic solid are reported and it is proposed that these systems might exist in two or more polycrystalline polymorphs or that they are observing distinguishable glassy states.
Journal Article•
TL;DR: In this paper, it is shown that the anomalous gluon and sea-quark interpretations for the deviation of the observed first moment of $g_1^p(x)$ from the Ellis-Jaffe sum rule are equivalent.
TL;DR: In this article, the authors review the theory and present status of the proton spin problem and discuss how the spin structure of constituent quarks is manifest in polarised deep inelastic scattering.
Abstract: We review the theory and present status of the proton spin problem and discuss how the spin structure of constituent quarks is manifest in polarised deep inelastic scattering.
Posted Content•
TL;DR: In this article, it is shown that the anomalous gluon and sea-quark interpretations for the deviation of the observed first moment of $g_1^p(x)$ from the Ellis-Jaffe sum rule are equivalent.
Abstract: The proton spin puzzle inspired by the EMC experiment and its present status are closely examined. Recent experimental progress is reviewed. Various factorization schemes due to the ambiguity arising from the axial anomaly are discussed. Some misconceptions in the literature about the $\MS$ factorization scheme are clarified. It is stressed that the polarized nucleon structure function $g_1(x)$ is independent of the factorization scheme chosen in defining the quark spin density. Consequently, the anomalous gluon and sea-quark interpretations for the deviation of the observed first moment of $g_1^p(x)$ from the Ellis-Jaffe sum rule are equivalent. While it is well known that the total quark spin in the chiral-invariant (CI) factorization scheme (e.g. the improved parton model) can be made to be close to the quark model expectation provided that the gluon spin is positive and large enough, it is much less known that, contrary to the gauge-invariant scheme (e.g. the MSbar scheme), the quark orbital angular momentum in the CI scheme deviates even farther from the relativistic quark model prediction. Recent developments in the NLO analysis of polarized DIS data, orbital angular momentum and lattice calculations of the proton spin content are briefly sketched.
01 Apr 2000
TL;DR: In this article, the form factor of the quark energy momentum tensor was calculated and the quarks orbital angular momentum of the nucleon was extracted from a quenched 163 × 24 lattice with Wilson fermions at β = 6.0 and β = 0.155.
Abstract: We calculate the form factor of the quark energy momentum tensor and thereby extract the quark orbital angular momentum of the nucleon. The calculation is done on a quenched 163 × 24 lattice at β = 6.0 and with Wilson fermions at κ = 0.148, 0.152, 0.154 and 0.155. We calculate the disconnected insertion stochastically which employs the Z2 noise with an unbiased subtraction. This proves to be an efficient method of reduce the error from the noise. We find that the total quark contribution to the proton spin is 0.29 ± 0.07. From this we deduce that the quark orbital angular momentum is 0.17 ± 0.08 and predict the gluon spin to be 0.21 ± 0.07, i.e. about 40% of the proton spin is due to the glue.
01 Jan 2000-Journal of The Japanese Society for Food Science and Technology-nippon Shokuhin Kagaku Kogaku Kaishi
TL;DR: T2値は米飯のかたさなど物性に関する官能検果していた.
Abstract: 冷蔵した米飯を電子レンジで加熱し,加熱した米飯内に存在するプロトンのスピン-スピン緩和時間T2値と米飯の官能検査値との関係を調べた.その結果,米飯内のプロトンのT2値と米飯の光沢など外観に関する官能検査値との対応は認められなかったが,T2値は米飯のかたさなど物性に関する官能検査値によく対応していた.
TL;DR: In this article, a theoretical interpretation is given to recent proton spin relaxation-time (T 1 ) measurements on NiCu(C 7 H 6 N 2 O 6 )(H 2 O) 3 ·2 H 2 O, which is an ideal one-dimensional ferrimagnetic Heisenberg model system of alternating spins 1 and 1 2.
TL;DR: In this paper, a thermal model for the gluonic cloud of comovers is given making contact between the formalism and the measured unpolarized cross sections, which leads to the conclusion that no correlations between the initial proton spin and the final charmonium spin should be existent.
Abstract: In this paper hadroproduction of charmonium states in polarized pp collisions is discussed. A thermal picture for the gluonic cloud of comovers is given making contact between the formalism and the measured unpolarized cross sections. The experimentally observed non-polarization of the final J/psi states leads to the consequence that no correlations between the initial proton spin and the final charmonium spin should be existent. Hence the single spin asymmetries vanish to leading order in that model.
Posted Content•
TL;DR: Gluonic degrees of freedom induce a contact term in the effective chiral Lagrangian description of the low-energy pp -> pp eta' reaction as discussed by the authors, and the strength of this contact term is related to the amount of spin carried by polarised gluons in a polarised proton.
Abstract: Gluonic degrees of freedom induce a contact term in the effective chiral Lagrangian description of the low-energy pp -> pp eta' reaction. The strength of this contact term is, in part, related to the amount of spin carried by polarised gluons in a polarised proton.
TL;DR: In this paper, the 1H nuclear magnetic resonance spin-lattice relaxation rate (NSLR) was measured as a function of temperature (1.5-4.2 K) and applied magnetic field (0.2-8.2 T) in the molecular magnet [(PhSiO2)6Cu6(O2SiPh)6] in short Cu6.
Abstract: We report 1H nuclear magnetic resonance spin-lattice relaxation rate (NSLR) measurements as a function of temperature (1.5–4.2 K) and as a function of applied magnetic field (0.2–8.2 T) in the molecular magnet [(PhSiO2)6Cu6(O2SiPh)6] in short Cu6. The results are explained in terms of a simple model whereby the NSLR is driven by the fluctuations of the local hyperfine field due to the reorientation of the total spin of the molecule in its ground state. From the analysis of the data, we infer the temperature and field dependence of the characteristic rate of the fluctuations of the total magnetization of the Cu6 ring in its ground state.We report 1H nuclear magnetic resonance spin-lattice relaxation rate (NSLR) measurements as a function of temperature (1.5–4.2 K) and as a function of applied magnetic field (0.2–8.2 T) in the molecular magnet [(PhSiO2)6Cu6(O2SiPh)6] in short Cu6. The results are explained in terms of a simple model whereby the NSLR is driven by the fluctuations of the local hyperfine field due to the reorientation of the total spin of the molecule in its ground state. From the analysis of the data, we infer the temperature and field dependence of the characteristic rate of the fluctuations of the total magnetization of the Cu6 ring in its ground state.
01 Jan 2000
TL;DR: In this article, the magnetic field dependence of the proton 1/T1 may be quantitatively related to structural fluctuations along the backbone that modulate proton-proton dipolar couplings.
Abstract: The magnetic field dependence of1H spin lattice relaxation rates in noncrystalline macromolecular solids including engineering polymers, proteins, and biological tissues is described by a power law, 1/T1 = Aω0-b, where ω0 is the Larmor frequency, A and b are constants. We show that the magnetic field dependence of the proton 1/T1 may be quantitatively related to structural fluctuations along the backbone that modulate proton-proton dipolar couplings. The parameters A and b are related to the dipolar coupling strength, the energy for the highest vibrational frequency in the polymer backbone, and the fractal dimensionality of the proton spatial distribution.
TL;DR: The Hermes experiment at the Desy laboratory in Hamburg, Germany, has been used to study the spin structure of the nucleon as mentioned in this paper, which is a unique feature of the Hera accelerator.
Abstract: The Hermes experiment at the Desy laboratory in Hamburg, Germany, studies the spin structure of the nucleon. Its unique feature is the combination of a polarized internal gas target with the longitudinally polarized 27.5 GeV electron/positron beam of the Hera accelerator. Recent Hermes measurements include the proton spin structure function g1p, the flavor decomposition of the polarized quark distributions in the nucleon, the DIS contribution to the generalized GDH sum rule, the first observation of a spin asymmetry in exclusive vector meson production and the first observation of a single-spin azimuthal asymmetry in semi-inclusive pion production. Additionally, the possibility of using various unpolarized gases as target material broadens the spectrum of physics measurements with Hermes.
TL;DR: In this paper, the contribution of a quark to the proton spin in the process of spin separation has been studied, where measurements of the quantities Δσ====== and Δσ± are obtained at small z, and the use of definite combinations of them allow important information on the spin structure to be obtained.
Abstract: In this work, the problem of separating the contribution of a strange quark to the proton spin in the process
$$ep \to e' Mx = (M = K^ \pm ,K^0 ,\bar K^0 ,\pi ^ \pm )$$
is studied. Measurements of the quantities Δσ
K
and Δσ±, where Δσ
M
=dσ
M
(+ +) -dσ
M
(+ -) at small z, and the use of definite combinations of them allow important information on the proton-spin structure to be obtained.
TL;DR: In this article, the second moment (M2) variation with temperature is explained on the basis of the different possible motions of CH3 and NH3 groups, and the observed T1 behaviour and second moment variation with second moment with temperature are explained by the CH3/NH3 groups.
Abstract: Proton spin lattice relaxation time (T1), measured as a function of temperature in the range 375–77 K, shows slope changes at 333, 221 and 111 K, in addition to a first order phase transition at 150K. The observed T1 behaviour and second moment (M2) variation with temperature are explained on the basis of the different possible motions of CH3 and NH3 groups.
TL;DR: In this paper, the spin of the proton was analyzed in terms of the spins of the constituent quarks, and the experimental electro-weak interactions between quarks and leptons.
Abstract: Employing the experimental electro-weak interactions between quarks and leptons, the spin of the proton may easily be understood in terms of the spins of the constituent quarks.
TL;DR: In this article, the gluon polarization contribution at the quark model renormalization scale to the proton spin in the chiral bag model was evaluated by taking the expectation value of the forward matrix element of a local glUon operator in the axial gauge.
Abstract: We study the gluon polarization contribution at the quark model renormalization scale to the proton spin, $\Gamma$, in the chiral bag model. It is evaluated by taking the expectation value of the forward matrix element of a local gluon operator in the axial gauge $A^+=0$. It is shown that the confining boundary condition for the color electric field plays an important role. When a solution satisfying the boundary condition for the color electric field, which is not the conventionally used but which we favor, is used, the $\Gamma$ has a positive value for {\it all} bag radii and its magnitude is comparable to the quark spin polarization. This results in a significant reduction in the relative fraction of the proton spin carried by the quark spin, which is consistent with the small flavor singlet axial current measured in the EMC experiments.
14 May 2000
TL;DR: In this paper, the ratio of the bound electron to proton g-factor in atomic hydrogen was measured in in a magnetic flux density of 0.6 tesla, and the electron and proton spin flip frequencies were determined by a least squares fit of the theoretical form of the modulated hydrogen electron spin resonance signal to the data.
Abstract: We describe an experiment to measure the ratio of the bound electron to proton g-factor in atomic hydrogen. This is performed in in a magnetic flux density of 0.6 tesla. The electron and proton spin flip frequencies are determined by a least squares fit of the theoretical form of the modulated hydrogen electron spin resonance signal to the data.