Hyperfine Interactions

, 194:327 | Cite as

Spin structure of \(\bar{p}p\rightarrow\bar{\Lambda}\Lambda\)

  • Mary Alberg


A complete determination of spin observables for \(\bar{p}p\rightarrow\bar{\Lambda}\Lambda\), at an antiproton lab momentum of 1.637 GeV/c, has been made by the PS185 Collaboration. Results of this experiment disagree strongly with the predictions of calculations which used either meson exchange or quark models for the reaction mechanism. We use a model-independent description of the spin structure of this reaction to show that, in the absence of initial and final state interactions, pure spin singlet or pure spin triplet reaction mechanisms require that depolarization D nn and spin transfer K nn are equal, in disagreement with experiment. We also show that a superposition of singlet and triplet reaction mechanisms allow D nn  ≠ K nn , as required by experiment.


Antiproton Lambda Polarization Spin observables Quark models 


13.75.Cs 13.88.+e 14.20.Jn 


  1. 1.
    Barnes, P.D., et al.: (PS185 Collaboration): High-statistics measurements of the \(\bar{p}p\rightarrow\bar{\Lambda}\Lambda\) and \(\bar{p}p\rightarrow\bar{\Lambda}\Sigma_0\) + c.c. reactions at threshold. Phys. Rev. C 62, 055203 (2000) and references thereinGoogle Scholar
  2. 2.
    Haidenbauer, J., Holinde, K., Mull, V., Speth, J.: Meson exchange and quark-gluon transitions in the \(\bar{p}p\rightarrow\bar{\Lambda}\Lambda\) process. Phys. Rev. C 46, 2158–2171 (1992)CrossRefADSGoogle Scholar
  3. 3.
    Paschke, K.D., et al.: (PS185 Collaboration): Experimental determination of the complete spin structure for \(\bar{p}p\rightarrow\bar{\Lambda}\Lambda\) at \(p_{\bar{p}}=1.637\) GeV/c. Phys. Rev. C 74, 015206 (2006)CrossRefADSGoogle Scholar
  4. 4.
    Alberg, M., Henley, E.M., Wilets, L., Kunz, P.D.: A quark model of \( \bar{\Lambda}\Lambda\) production in \(\bar{p}p\) interactions. Il Nuovo Cim. A 107, 2483–2490 (1994)CrossRefADSGoogle Scholar
  5. 5.
    Artru, X., Elchikh, M., Richard, J.-M., Soffer, J., Teryaev, O.: Spin observables and spin structure functions: inequalities and dynamics. Phys. Rep. 470(1–2), 1–92 (2009). arXiv:0802.0164v2 [hep-ph]CrossRefMathSciNetADSGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  1. 1.Department of PhysicsSeattle UniversitySeattleUSA

Personalised recommendations