The proton spin puzzle and depolarization in

Alberg, Mary; Ellis, John; Kharzeev, Dmitri E.

doi:10.1016/0370-2693(95)00789-n

Cited by 51 publications

(64 citation statements)

References 41 publications

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“…We found that, with the use of RHOQM, the direct knockout process gives a very distinct contribution to some of the double polarization observables in φ photoproducton as compared to those of diffractive production and one-pion-exchange (OPE) process. A similar conclusion was drawn from thepp →ΛΛ process to distinguish between contributions from the hidden strangeness of the nucleon and the effects from meson exchange processes [35]. (See also Ref.…”

Section: Introductionsupporting

confidence: 61%

Photoproduction ofφmesons from the proton: Polarization observables and strangeness in the nucleon

Титов¹,

Yang

et al. 1998

Phys. Rev. C

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The polarization observables in φ meson photoproduction is studied to probe the strangeness content of the nucleon. In addition to the dominant diffractive production and the one-pion-exchange process, we take into account the direct knockout mechanism that arises from the possible hidden strangeness content of the nucleon. We find that some double polarization observables are very sensitive to the strangeness content of the proton because of the different spin structures of the amplitudes associated with different mechanisms. This suggests that such measurements could be very useful in probing the strangeness content in the proton. The orbitally excited quark-cluster configurations in the proton are included in the calculation and found to have little effect. PACS number(s): 13.88.+e, 24.70.+s, 25.20.Lj, 13.60.Le

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Section: Introductionsupporting

confidence: 61%

Photoproduction ofφmesons from the proton: Polarization observables and strangeness in the nucleon

Титов¹,

Yang

et al. 1998

Phys. Rev. C

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“…The process could also proceed via the dissociation of a strangeness component in the (anti-)proton, as shown in Fig. 1b, an idea which has already been applied to the pp → ΛΛ reaction [6]. More conventionally, the reaction can be described in a one-baryon-exchange model via charged Σ exchange.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the p̄p→KSKSη cross section at beam momenta in the regions of 1.45 and 1.7 GeV/c

et al. 2001

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The PS185 experiment at LEAR/CERN has investigated strangeness production in pp collisions with final states such as ΛΛ, Σ 0 Λ+c.c, Σ + Σ + , Σ − Σ − and K S K S . Results are presented from a study of about 32,000 K S K S X events obtained at several p momenta in the regions of 1.45 and 1.7 GeV/c. The pp → K S K S η cross sections extracted at these momenta constitute the first measurement of this reaction in flight and are broadly consistent with expectations of a phase-space extrapolation of branching ratios from annihilation at rest.

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“…While careful applications of each of these approaches have been able to describe the existing data with reasonable accuracy, differing predictions are obtained for those observables which depend on initial state spin [4,6]. There has also been growing interest in the relevance of the spin structure ofpp →ΛΛ to the question of the strangeness component of the nucleon [8,9].The formalism for scattering two spin-1 2 particles to two spin-1 2 particles has been well developed in both the general case and in application to thepp →Ȳ Y reaction [10][11][12][13]. The implications of this application of the formalism must be carefully explored for the larger set of observables available to PS185/3 [14,15].…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…The implications of this application of the formalism must be carefully explored for the larger set of observables available to PS185/3 [14,15]. The recent literature discussing the strangeness production dynamics has focused on the depolarization D nn , and, to a lesser extent, other rank-2 spin observables to which PS185/3 is directly sensitive [3, 4,6,8,14]. As will be shown below, the use of a transverse target polarization, in principle, allows the complete determination of the spin structure of the reaction.…”

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confidence: 99%

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Spin observables in with a transverse initial state polarization

Paschke

Quinn

2000

Physics Letters B

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The formalism describing the scattering of two spin-1 2 objects is reviewed for the case ofpp →ΛΛ. It is shown that an experiment utilizing a transverse target polarization can, in principle, completely determine the spin structure of the reaction. Additional measurements, even those using both beam and target polarizations, would not be sensitive to any additional spin dynamics. Thus, the transverse target polarization allows access to the complete set of spin observables, not just the subset upon which the literature has previously focused. This discussion is especially relevant in light of the data collected by PS185/3 at LEAR.Exclusive production of antihyperon-hyperon states from antiproton-proton annihilation (pp → Y Y ) has been extensively studied near threshold by the PS185 collaboration throughout the 13 year lifetime of LEAR at CERN [1,2]. Results for the total and differential cross-sections and those spin observables depending only on final state spins have been published for a range of energies and channels. In 1996, an upgraded version of the experiment, PS185/3, incorporated a transverse target polarization to allow sensitivity to a wider range of spin observables in the reactionpp →ΛΛ [3].There is significant interest in the results of this measurement. Two types of models with different physical motivations have been successfully used to describe the reaction in this energy regime: K and K * meson exchange [4,5] and effective quark models [6,7]. While careful applications of each of these approaches have been able to describe the existing data with reasonable accuracy, differing predictions are obtained for those observables which depend on initial state spin [4,6]. There has also been growing interest in the relevance of the spin structure ofpp →ΛΛ to the question of the strangeness component of the nucleon [8,9].The formalism for scattering two spin-1 2 particles to two spin-1 2 particles has been well developed in both the general case and in application to thepp →Ȳ Y reaction [10][11][12][13]. The implications of this application of the formalism must be carefully explored for the larger set of observables available to PS185/3 [14,15]. The recent literature discussing the strangeness production dynamics has focused on the depolarization D nn , and, to a lesser extent, other rank-2 spin observables to which PS185/3 is directly sensitive [3,4,6,8,14]. As will be shown below, the use of a transverse target polarization, in principle, allows the complete determination of the spin structure of the reaction. This then permits model independent predictions of the full set of spin observables, including those that were not directly measured. This is the first demonstration of the feasibility of such an analysis for pp →ΛΛ, although this possibility had been hinted at by previous publications [13].In discussing spin-1 2 particle scattering it is common to parameterize the spin structure of the transition matrix M explicitly. Forpp →ΛΛ, the transition matrix M can be written 1

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The proton spin puzzle and depolarization in

Cited by 51 publications

References 41 publications

Photoproduction ofφmesons from the proton: Polarization observables and strangeness in the nucleon

Photoproduction ofφmesons from the proton: Polarization observables and strangeness in the nucleon

Measurement of the p̄p→KSKSη cross section at beam momenta in the regions of 1.45 and 1.7 GeV/c

Spin observables in with a transverse initial state polarization

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