Experience of the University Hospital Zurich, Zurich, Switzerland

Schlumpf, R.; Largiadèr, F

doi:10.1007/978-94-009-1083-6_35

Cited by 13 publications

(26 citation statements)

References 3 publications

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“…We get a value similar to Ref. [30] V us = 0.225 ± 0.003 [13]. (4.13) This has to be compared to the value from K e3 which is 0.2196 ± 0.0023 [31].…”

Section: E Su(3) Symmetry Breakingsupporting

confidence: 69%

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β decay of hyperons in a relativistic quark model

Schlumpf

1995

Phys. Rev. D

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A relativistic constituent quark model is used to calculate the semileptonic beta decay of nucleons and hyperons. The parameters of the model, namely, the constituent quark mass and the confinement scale, are fixed by a previous calculation of the magnetic moments of the baryon octet within the same model. We discuss the momentum dependence of the form factors, possible configuration mixing and SU(3) symmetry breaking. We conclude that the relativistic constituent quark model is a good framework to analyze electroweak properties of the baryons.

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“…We get a value similar to Ref. [30] V us = 0.225 ± 0.003 [13]. (4.13) This has to be compared to the value from K e3 which is 0.2196 ± 0.0023 [31].…”

Section: E Su(3) Symmetry Breakingsupporting

confidence: 69%

“…This puzzle was pointed out independently by Lipkin [17] and the author [13]. For g 2 = 0 it is measured that [18] …”

Section: Numerical Resultsmentioning

confidence: 99%

β decay of hyperons in a relativistic quark model

Schlumpf

1995

Phys. Rev. D

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“…We find a quark mass m = 263 MeV and a scale α = 607 MeV by fitting the magnetic moment of the proton µ(p) and the neutron µ(n). In addition, these parameters give also excellent results for the magnetic moments and the semileptonic decays of the baryon octet [7].For reference, we calculate the form factors with Eq. (2) using parameters α = 560 MeV and m = 267 MeV as well.…”

mentioning

confidence: 99%

“…The matrix elements can be calculated within a relativistic constituent quark model on the light cone [4,5,6]. This approach has been extended to asymmetric wave functions [7], which provide an excellent and consistent picture of electroweak transitions of the baryon octet. In this report we focus on the high energy behavior of the wave function.…”

mentioning

confidence: 99%

Nucleon form factors in a relativistic quark model

Schlumpf¹

1994

J. Phys. G: Nucl. Part. Phys.

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We demonstrate that a relativistic constituent-quark model can give nucleon form factors in agreement with data for both low and high momentum transfer. The relativistic features of the model and the specific form of the wave function are essential for the result.12.35. Ht, 13.40.Fn Typeset Using REVTEX * Work supported in part by the Department of Energy, contract DE-AC03-76SF00515. It is therefore important to have a model that is valid for all values of Q 2 .The hadronic matrix element of the radiative transition of the nucleon N → N ′ γ is represented in terms of the form factors aswith momentum transfer Q = p ′ − p, nucleon mass M N , and quark current J µ =qγ µ q.The Sachs form factor for the magnetic transition is given by G M = F 1 + F 2 . The matrix elements can be calculated within a relativistic constituent quark model on the light cone [4,5,6]. This approach has been extended to asymmetric wave functions [7], which provide an excellent and consistent picture of electroweak transitions of the baryon octet. In this report we focus on the high energy behavior of the wave function.Usually harmonic-oscillator-type wave functions are used [4,5,6] with α being the confinement scale of the bound state and N being the normalization. The operator M is the free mass operator of the noninteracting three-body system, and it is a function of the internal momentum variables q i of the quarks and the quark mass m:2 With this special form of the wave function the form factors fall off exponentially for high Q 2 . This is why the form factors calculated with Eq. (2) are only valid up to 4-6 GeV 2 , an energy scale well below the perturbative region [3].The orbital wave function we use iswith a scale α and normalization factor N different from Eq. (2). The two parameters of the model, the confinement scale α and the quark mass m, have to be determined by comparison with experimental data. We find a quark mass m = 263 MeV and a scale α = 607 MeV by fitting the magnetic moment of the proton µ(p) and the neutron µ(n). In addition, these parameters give also excellent results for the magnetic moments and the semileptonic decays of the baryon octet [7].For reference, we calculate the form factors with Eq. (2) using parameters α = 560 MeV and m = 267 MeV as well. The results are shown in Figs. 1-3. Note that the low energy behavior of both wave functions is almost identical, while only the wave function in Eq. (4) fits the data. It is therefore significant to choose an appropriate Ansatz for the orbital wave function. The relativistic features of the model are also important. In the nonrelativistic limit, α/m → 0, the form factor G M for the proton is (for small Q 2 )which is too small for any reasonable value of α and m (compare Figs. 1 and 2). This limit shows that the relativistic treatment of the problem increases the form factors significantly, even for low values of the momentum transfer. The same effect has also been found for the pion [8]. While the asymptotic falloff for the wave function in Eq. (4) is still larg...

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“…Basic definitions and formalism are discussed in Refs. [105,106]. A four-vector in the light-front frame is defined as…”

Section: Light-front Representation Of the Nucleonmentioning

confidence: 99%

Contribution of the spin-1 diquark to the nucleon’sg1structure function

Zamani

2010

Phys. Rev. C

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This is the final installment of a series of work that we have done in the context of the meson cloud model that investigates F 2 and g 1 structure functions. In our previous work on g 1 structure function, we showed that having a spin-0 quark-diquark for the nucleon core along with both pseudoscalar and vector meson clouds was not sufficient to reproduce experimental observation(s) consistently. For the F 2 structure function, we found that both superposition of a spin-0 diquark and a spin-1 diquark in the nucleon core along with pseudoscalar and vector meson clouds are needed to reproduce the observed F 2 (x) and the Gottfried sum rule (GSR) violation. Therefore, in the present work, we consider the contribution of a spin-1 diquark in the nucleon core to the g 1 structure function. The calculation is performed in the light-cone frame. The dressed nucleon is assumed to be a superposition of the bare nucleon plus virtual light-cone Fock states of baryon-meson pairs. For the bare nucleon, we consider different quark-diquark configurations along with the possibility that there is no diquark inside the nucleon. The initial distributions are evolved. The final results are compared with experimental results and other theoretical predictions.

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Experience of the University Hospital Zurich, Zurich, Switzerland

Cited by 13 publications

References 3 publications

β decay of hyperons in a relativistic quark model

β decay of hyperons in a relativistic quark model

Nucleon form factors in a relativistic quark model

Contribution of the spin-1 diquark to the nucleon’sg1structure function

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