1. 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.  + n vs.  0 p vs. K +  – 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. Sept. 26, 2009Hadron Spectroscopy MeetingMac Mestayer 1 uudd ss qq

2. Quark Pair Creation Quark-pair creation: “kernel” of exclusive production What field couples to the q-q current? susu sudsud K+K+  susu K+K+  udSudS ss produced From flux-tube ss produced from photon Sept. 26, 2009Mac Mestayer 2Hadron 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 uudd ss uudd ss Sept. 26, 2009Mac Mestayer 3Hadron 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  + (n) production experiment Kaskulov, Gallmeister, Mosel; arXiv:0804.1834v4 [hep-ph] – model was developed to explain Rosenbluth separated exclusive electro-production of  + (n)    L described well as t-channel exchange    T described well as “quark-scattering followed by string-breaking” with Lund model parameters – model also works for un-separated data Sept. 26, 2009Mac Mestayer 4Hadron Spectroscopy Meeting

5. Exclusive n  + : sum of two processes t-channel form factor falls with q 2 dudu ++ n uddudd photon couples to quark photon probes meson structure no form factor: q 2 independent  T : DIS via LUND model  L : t-channel exchange Sept. 26, 2009Mac Mestayer 5Hadron Spectroscopy Meeting

6. Analysis goals and plans Model-independent goal – measure ratio of  + n :  0 p : K +  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, q 2, t ) – tune PYTHIA/JETSET (fitting and MC generator) Study single quark-pair creation Sept. 26, 2009Mac Mestayer 6Hadron Spectroscopy Meeting

7. (  )  +  “Fake” plots mis-identified protons mis-identified pions K + Missing Mass Sept. 26, 20097Hadron Spectroscopy Meeting forward  Lab Angle  backward

8. P (  0 )  (n)  +  forward  Lab Angle  backward Missing Mass  2-body final state Sept. 26, 2009Mac Mestayer 8Hadron Spectroscopy Meeting

9. Sept. 26, 2009Mac Mestayer 9Hadron Spectroscopy Meeting

10. Sept. 26, 2009Mac Mestayer 10Hadron Spectroscopy Meeting

11. Sept. 26, 2009Mac Mestayer 11Hadron Spectroscopy Meeting

12. Sept. 26, 2009Mac Mestayer 12Hadron Spectroscopy Meeting

13. Sept. 26, 2009Mac Mestayer 13Hadron Spectroscopy Meeting

14. Sept. 26, 2009Mac Mestayer 14Hadron Spectroscopy Meeting

15. Sept. 26, 2009Mac Mestayer 15Hadron 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 +  – t-channel exchange + LUND-type model Sept. 26, 2009Hadron Spectroscopy MeetingMac Mestayer 16

17. Sept. 26, 2009Hadron Spectroscopy MeetingMac Mestayer 17 Lund model value: 0.2 Ratio of normalized yields : K +  /  + n W = 1.9 GeV

18. Sept. 26, 2009Hadron Spectroscopy MeetingMac Mestayer 18 Ratio of normalized yields : K +  /  + n W = 2 GeV Lund model value: 0.2

19. Sept. 26, 2009Hadron Spectroscopy MeetingMac Mestayer 19 Lund model value: 0.2 Ratio of normalized yields : K +  /  + n W = 2.2GeV