Search for the xi(2220) and Study of the X(3872) at BABAR

TL;DR

This paper reports a search for the xi(2220) resonance with no evidence found and sets upper limits, while also providing evidence for the decay X(3872) --> J/psi omega and analyzing its parity.

Contribution

First search for xi(2220) production at BABAR with improved upper limits; also reports evidence for X(3872) decay to J/psi omega and studies its parity.

Findings

No evidence for xi(2220); upper limits below previous reports.

Evidence for X(3872) --> J/psi omega with specific branching fractions.

Pi+ pi- pi0 mass distribution suggests negative parity for X(3872).

Abstract

The BABAR Collaboration performed a search for xi(2220) production in the initial-state radiation process e^+e^- --> gamma J/psi, J/psi --> gamma K^+K^- or J/psi --> gamma K^0_SK^0_S. No evidence for the xi(2220) resonance has been found. The 90% confidence level upper limits on the product of branching fractions are sensitive to the spin and helicity hypotheses. These upper limits are of the order 10^-5, below the values reported in previous experiments. Also at BABAR, the decays B --> J/psi pi^+ pi^- pi^0 K are studied to search for the decay X(3872) --> J/psi omega. This search yields a four standard deviation evidence for X(3872) --> J/psi omega, with product branching fractions of B(B^+ --> X(3872)K^+) x B(X(3872) --> J/psi omega)=[0.6 +- 0.2(stat) +- 0.1(syst) ] x 10^-5, and B(B^0 --> X(3872)K^0) x B(X(3872) --> J/psi omega =[0.6 +- 0.3(stat) +- 0.1(syst) ] x 10^-5. A detailed study of the pi^+ pi^- pi^0 mass distribution from X(3872) decay favors a negative-parity assignment but does not rule out the positive-parity hypothesis.