Asymmetry Parameter and Branching Ratio of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>Σ</mml:mi></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mo>→</mml:mo><mml:mi>p</mml:mi><mml:mi>γ</mml:mi></mml:math>

Gershwin, Lawrence K.; Alston‐Garnjost, M.; Bangerter, R.O.; Barbaro‐Galtieri, A.; Mast, Terry S.; Solmitz, Frank T.; Tripp, Robert D.

doi:10.1103/physrev.188.2077

Cited by 82 publications

(17 citation statements)

References 13 publications

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“…Introducing weak breaking of SU(3) symmetry one expects to observe small decay asymmetries. In contrast to this, a large negative decay asymmetry in the weak radiative decay Σ + → pγ was first measured by Gershwin et al [4] and later confirmed [5]. To address this observation, models were developed which tried to obtain large decay asymmetries in spite of weak SU(3) breaking.…”

Section: Introductionmentioning

confidence: 96%

Measurement of the Ξ0→Λγ decay asymmetry and branching fraction

Lai

Marras

Bevan³

et al. 2004

Physics Letters B

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In data taken with the NA48 experiment at the CERN SPS in 1999, 730 candidates of the weak radiative hyperon decay Ξ 0 → Λγ have been found with an estimated background of 58 ± 8 events. From these events the Ξ 0 → Λγ decay asymmetry has been determined to α(Ξ 0 → Λγ ) = −0.78 ± 0.18 stat ± 0.06 syst , which is the first evidence of a decay asymmetry in Ξ 0 → Λγ . The branching fraction of the decay has been measured to be Br(Ξ 0 → Λγ ) = (1.16 ± 0.05 stat ± 0.06 syst ) × 10 −3 .

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Section: Introductionmentioning

confidence: 96%

Measurement of the Ξ0→Λγ decay asymmetry and branching fraction

Lai

Marras

Bevan³

et al. 2004

Physics Letters B

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“…In addition, the number of py events detected in both experiments was very small (61 [2] and 46 [3], respectively).…”

Section: S7 Petersburg Nuclear Physics Institute Gatchina Russia ^mentioning

confidence: 81%

Measurement of the asymmetry parameter in the hyperon radiative decayΣ+→pγ

Foucher¹,

If²,

Bondar³

et al. 1992

Phys. Rev. Lett.

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We have measured the asymmetry parameter (a r ) in the hyperon radiative decay X + -py with a sample of 34754±212 events obtained in a polarized charged hyperon beam experiment at Fermilab. We find ee y --0.720 ±0.086 ±0.045, where the quoted errors are statistical and systematic, respective-"y.PACS numbers: 13.40.Hq, 14.20JnHyperon radiative decays represent a class of baryon decays which require contributions from both the weak and electromagnetic interactions. Hara proved in 1964 [1] that the asymmetries in radiative hyperon decay vanish in the SU(3) limit, assuming only CP invariance and left-handed currents in the weak interaction. Contrary to this prediction, the first measurements of the asymmetry parameter in the decay Z + -* py revealed some evidence for large negative asymmetries (a Y = -1.03 io."42 f2], -0.53 ±0.36 [3]). These were bubble chamber experiments where polarized I + were produced from the lowenergy K~p->I + /r~ reaction. The average Z + polarization was about 40%.The main difficulty in such experiments is separation of the £ + -* py radiative decay from the 400 times more abundant hadronic decay Z + -* pn 0 .Moreover, the asymmetry parameter in the hadronic decay is large and negative (a^c--0.980±0.016 [4]), which raised the concern that the observed asymmetry in the E + -py decay might be, in fact, due to some contamination of the background into the py sample. In addition, the number of py events detected in both experiments was very small (61 [2] and 46 [3], respectively). These observations raised a wide interest among theorists [5]. Various models were investigated. None of these models could describe satisfactorily both the large negative asymmetry and the observed rate of the I + -• py decay. This became possible only recently in the form of a QCD sum-rule model [6]. A new measurement of the S + -* py asymmetry was performed in 1987 at KEK in a counter experiment [7]L + K + . The with I + produced in the reaction n*ppolarization of the 1* was about 87%. From a sample of 190 events the asymmetry parameter was found to be -0.86 ± 0.13(stat) ± 0.04(syst).This experiment (E761) [8] was designed to perform a measurement of the asymmetry parameter in the L + -+ py decay on a high statistical level and with reliable separation from the L + -•/J/T 0 mode. The highenergy hyperon beam at Fermilab provided a large flux («2000/sec) of I + with a polarization of 12%. The direction of the polarization was periodically reversed to allow the separation of the asymmetry from instrumental biases. To identify the I*-* py decay we used chargedparticle spectrometers that provided high-precision measurements of the missing neutral mass. In addition, a special photon spectrometer was constructed to determine the direction and energy of the photons.The experiment was located in the Proton Center beam line at Fermilab. The apparatus (Fig. 1) has four parts: 3004

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“…Polarization experiments with baryons often show results that are substantially different from the ones obtained in theoretical calculations made beforehand. It is possible to point to such researches as examples: the deep inelastic scattering of longitudinally polarized muons by longitudinally polarized protons [1]; the production of the hyperons Σ 0 [2] and Ξ + [3] by polarized protons on Be nuclei; the decays of polarized hyperons Σ + → pγ [4]. It is especially worth noting a substantial discrepancy in the values of the ratio of the electric G E and magnetic G M form factors of the proton obtained in two series of experiments on elastic electron-proton scattering staged at Jefferson Laboratory.…”

Section: Introductionmentioning

confidence: 99%

MAGNETIC MOMENT OPERATOR OF NON-DIRAC PARTICLES AND SOME ELEMENTS OF POLARIZATION ep-EXPERIMENTS

Slad

2013

Mod. Phys. Lett. A

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An explicit form of the magnetic moment tensor operator for non-Dirac particles with rest spin 1/2 and its essential difference from the spin operator are established. Possible consequences of the last fact for the description of the spin rotation in the magnetic field and for the values of magnetic moments of some nuclei, as well as the impact of this and other facts on the validity of modeling the azimuthal asymmetry of the secondary-scattered protons in polarization ep-experiments are noted. * slad@theory.sinp.msu.ru

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Asymmetry Parameter and Branching Ratio ofΣ+→pγ

Abstract: E 7 interval over which the fit is carried out, the cross sections p7r + 7r~ir 0 , whereA N exposure of 1.3X10 6 pictures in the Berkeley 25-in. hydrogen bubble chamber yielded about 57 000 events of the typ… Show more

Cited by 82 publications

References 13 publications

Measurement of the Ξ0→Λγ decay asymmetry and branching fraction

Measurement of the Ξ0→Λγ decay asymmetry and branching fraction

Measurement of the asymmetry parameter in the hyperon radiative decayΣ+→pγ

MAGNETIC MOMENT OPERATOR OF NON-DIRAC PARTICLES AND SOME ELEMENTS OF POLARIZATION ep-EXPERIMENTS

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