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Exclusive Production Ratios Mac Mestayer, Kijun Park, Christian Weiss

Exclusive Production Ratios Mac Mestayer, Kijun Park, Christian Weiss. What are we measuring? ratios of cross-sections for 2-body (baryon-meson) final states: e.g. p + n vs. p 0 p vs. K + L i.e. ratios of processes in which only one pair is produced :

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Exclusive Production Ratios Mac Mestayer, Kijun Park, Christian Weiss

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  1. Exclusive Production RatiosMac Mestayer, Kijun Park, Christian Weiss What are we measuring? • ratios of cross-sections for 2-body (baryon-meson) final states: e.g. p+n vs. p0p vs. K+L • i.e. ratios of processes in which only one pair is produced : What can we learn by measuring them? • kinematic domain in which the dominant interacting currents are quarks, not hadrons • how the color flux-tube is broken. ss uu qq dd Hadron Spectroscopy Meeting

  2. Quark Pair Creation • Quark-pair creation: “kernel” of exclusive production • What field couples to the q-q current? u d S L ss produced From flux-tube s u s u K+ ss produced from photon K+ s u d L Hadron Spectroscopy Meeting

  3. Using Exclusive Production to Study Quark Pair Creation • Lund model: successful phenomenology for hadron production; e.g. in e+e- reactions • color flux-tube broken by qq production • production rate depends on constituent quark mass • : : ~ 1 : 1 : 0.2 • Vector meson dominance: photon fluctuates into a virtual qq meson • production rate depends on quark charge • : : ~ 1: 0.25 : 0.25 ss ss uu uu dd dd Hadron Spectroscopy Meeting

  4. Limits of the “quark model” ? Can the Lund model work in the limit of single qq pair production? • recent analysis of a Hall C p+(n) production experiment • Kaskulov, Gallmeister, Mosel; arXiv:0804.1834v4 [hep-ph] • model was developed to explain Rosenbluth separated exclusive electro-production of p+(n) asLdescribed well as t-channel exchange asTdescribed well as “quark-scattering followed by string-breaking” with Lund model parameters • model also works for un-separated data Hadron Spectroscopy Meeting

  5. Exclusive np+: sum of two processes sT: DIS via LUND model sL: t-channel exchange photon probes meson structure u d d n photon couples to quark d u p+ t-channel no form factor: q2 independent form factor falls with q2 Hadron Spectroscopy Meeting

  6. Analysis goals and plans • Model-independent goal • measure ratio of p+n : p0p : K+L cross-sections • proportional to uu : dd : ss rate • Extend Kaskulov, Gallmeister, Mosel model • extend to dd and ss production • Analysis plan • identify final states (done) • decide on binning ( high/low bins for W, q2, t ) • tune PYTHIA/JETSET (fitting and MC generator) • Study single quark-pair creation Hadron Spectroscopy Meeting

  7. K+ Missing Mass (L) K+a “Fake” plots mis-identified protons mis-identified pions forward f Lab Angle g backward Hadron Spectroscopy Meeting

  8. Missing Mass • 2-body final state (n) p+a P (p0)a forward f Lab Angle g backward Hadron Spectroscopy Meeting

  9. Hadron Spectroscopy Meeting

  10. Hadron Spectroscopy Meeting

  11. Hadron Spectroscopy Meeting

  12. Hadron Spectroscopy Meeting

  13. Hadron Spectroscopy Meeting

  14. Hadron Spectroscopy Meeting

  15. Hadron Spectroscopy Meeting

  16. Conclusions • Yield ratios show simple phenomenology • Statistics look good • Analysis work to be done: • rad. corrections, phase-space factors, background subtractions • Decide on binning • Develop event generator for K+L • t-channel exchange + LUND-type model Hadron Spectroscopy Meeting

  17. Ratio of normalized yields : K+L / p+ n W = 1.9 GeV Lund model value: 0.2 Hadron Spectroscopy Meeting

  18. Ratio of normalized yields : K+L / p+ n W = 2 GeV Lund model value: 0.2 Hadron Spectroscopy Meeting

  19. Ratio of normalized yields : K+L / p+ n W = 2.2GeV Lund model value: 0.2 Hadron Spectroscopy Meeting

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