This pages summarizes search for an exotic baryon state Theta_c in CDF data.
The long-standing question of whether there are 5-quark baryons has been reinvigorated in the past year by multiple reports of the existence of a baryon decaying to a KN final state with positive strangeness. This state, the Theta(1540), is manifestly exotic and had been predicted in 1997 as the lightest member of an anti-decuplet of states on the basis of a chiral soliton model by Diakonov, Petrov, and Polyakov Z.Phys.A359:305-314,1997 . There should be a charmed analog of this decuplet. Charmed pentaquarks had been predicted much earlier by other authors based on different models. The H1 experiment recently reported the observation of a narrow baryon at 3099 Mev/c² decaying to D^*p + c.c. (hep-ex/0403017) This state is a candidate for the charmed pentaquark Theta_c or perhaps an excited state thereof.

All references to spesific charged state imply charge conjugate state as well unless specifically stated otherwise.
Below the eps versions of all figures meant for downloads.

• Figure 1: An invariant mass of K^-,pi⁺ combinations passing displaced trigger requirements eps , gif
• Figure 2: A mass difference plot M(D⁰pi⁺)-M(D⁰) eps, gif
• Reference Channels:
  • Figure 3: A mass difference plot M(D^*+pi^-)-M(D^*+) eps, gif
  • Figure 4: Mass of M(D⁺pi^-) eps, gif
  • Figure 5: Mass of M(D⁰pi⁺) eps, gif
• PID performance:
• Figure 6: Lambda_c> proton K^- pi⁺ eps, gif -- no PID cuts
• Figure 7: Lambda_c> proton K^- pi⁺ eps, gif -- PID cut LH_p > 0.3
• Pentaquark spectra
• Theta_c > D^*-p
• Figure 8: A mass difference M(D^*-p) = M(D^*-p)-M(D^*-)+2.010 spectrum eps, gif
• Figure 9: Pentaquark yield at 90% Confidence Level as a function of mass eps, gif
• Theta_c > D^-p
• Figure 10: M(D^-p) spectrum eps, gif
• Figure 11: Pentaquark yield at 90% Confidence Level as a function of mass eps, gif
• Theta_c > D⁰p
• Figure 12: M(D⁰p) spectrum eps, gif
• Figure 13: Pentaquark yield at 90% Confidence Level as a function of mass eps, gif
• Figure 14: M(D⁰⁼p) spectrum eps, gif
• Figure 15: Pentaquark yield at 90% Confidence Level as a function of mass eps, gif

Documentation

A full description of the analysis is in cdfnote 6978