Spin and polarization of the D and E mesons in $$\bar pp$$ annihilationsannihilations

The case of the pseudoscalar glueball

“…It should be noted that in these data a much higher background level is also present with respect to the case of the pp at rest [20,21]. Nevertheless, the higher statistics of the π − p [22] data combined with the cumulative evidence from the other experiments [70][71][72][73] determined a revision of the E(1420) spin assignment, which was then identified as an axial vector [16]. This was the reason why, when a pseudoscalar was discovered a few years later at the same mass in the J / decay [14], it was given a different name (see section 3.1) giving rise to the E/ι puzzle.…”

“…In 1980, almost 20 years after its first observation in pp annihilation at rest [20], E(1420) was still considered an unclear object [69]. Originally identified as a J PC = 0 −+ state [21], its spin assignment was questioned, by several other experiments, in π − p interaction and pp annihilation at 0.7 and 0.76 GeV/c [70][71][72][73]. The experiments indicated that E(1420) was an axial vector rather than a pseudoscalar, but their statistics was poor and the data were not as clean as in the case of pp at rest [20,21].…”

“…However, for quite a few years E(1420) was still considered an unclear object [69]. Several other experiments questioned its spin assignment in π − p interaction and pp annihilation at 0.7 and 0.76 GeV/c 2 [22,[70][71][72][73]. All these experiments showed an enhancement corresponding to E(1420), but their analysis indicated that the state was an axial vector.…”

Light Hadronic Spectroscopy: Experimental and Quark Model Interpretations

“…The mass and width fo r this enhancement are given as "" 1420 MeV and 50 ±20 MeV, respectively. Analysis fa vors IG jP = 0-1 + (Vuillemin et al 1975) ; however, the back ground was large and the resonant interpretation of the enhancement was open to question as it has been observed only at low momentum pp annihilation at the peak of phase space. Recently the E has also been seen in the reaction n-p � K ± Kon ± n by two experiments, one at the Omega Spectrometer (Gordon et al 1978) and a bubble chamber experi ment at 3.9 GeV Ie (BCCFMS collaboration 1978), and can be considered well established.…”