Formation of the $S=-1$ resonance X(2265) in the reaction $pp -> X + K^+$ at 2.50 and 2.85 GeV

TL;DR

This study investigates the production of the X(2265) resonance in proton-proton collisions at two energies, revealing its dependence on the Lambda(1405) state and providing insights into its formation mechanism.

Contribution

It demonstrates the energy-dependent production of X(2265) and highlights the role of Lambda(1405) as a doorway state in its formation, based on analysis of DISTO data.

Findings

X(2265) production is significantly lower at 2.50 GeV than at 2.85 GeV.

The production rate at 2.50 GeV is less than 10%, contrary to expectations of 33%.

Lambda(1405) weak production correlates with X(2265) formation.

Abstract

Analyzing DISTO data of $pp -> p Lambda K^+$ at $T_p = 2.50$ and 2.85 GeV to populate a previously reported X(2265) resonance with $M_X = 2267$ MeV/$c^2$ and $Gamma_X = 118$ MeV at 2.85 GeV, we found that the production of X(2265) at 2.50 GeV is much less than that at 2.85 GeV (less than 10%), though it is expected from a kinematical consideration to be produced as much as 33% of that at 2.85 GeV. The small population of X(2265) at 2.50 GeV is consistent with the very weak production of Lambda (1405) at the same incident energy toward its production threshold, thus indicating that Lambda (1405) plays an important role as a doorway state for the formation of X(2265).