rpp2010-rev-eta1440 - 1 THE (1405), (1475), f 1 (1420), AND...

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Unformatted text preview: 1 THE (1405), (1475), f 1 (1420), AND f 1 (1510) Revised February 2010 by C. Amsler (Zurich) and A. Masoni (INFN Cagliari). The first observation of the (1440) was made in p p anni- hilation at rest into (1440) + , (1440) K K [1]. This state was reported to decay through a (980) and K (892) K with roughly equal contributions. The (1440) was also ob- served in radiative J/ (1 S ) decay into K K [24] and [5]. There is now evidence for the existence of two pseudoscalars in this mass region, the (1405) and (1475). The former decays mainly through a (980) (or direct K K ) and the latter mainly to K (892) K . The simultaneous observation of two pseudoscalars is re- ported in three production mechanisms: p [6,7]; radiative J/ (1 S ) decay [8,9]; and pp annihilation at rest [1114]. All of them give values for the masses, widths, and decay modes in reasonable agreement. However, Ref. [9] favors a state decay- ing into K (892) K at a lower mass than the state decaying into a (980) , although agreement with MARK-III is not excluded. In J/ (1 S ) radiative decay, the (1405) decays into K K through a (980) , and hence a signal is also expected in the mass spectrum. This was indeed observed by MARK III in + [15], which reports a mass of 1400 MeV, in line with the existence of the (1405) decaying into a (980) . BES [10] reports an enhancement in K + K around 1.44 GeV in J/ (1 S ) decay, recoiling against an (but not a ) without re- solving the presence of two states nor performing a spin-parity analysis, due to low statistics. This state could also be the f 1 (1420) (see below). The (1405) is also observed in pp annihilation at rest into + , where it decays into [16]. The intermedi- ate a (980) accounts for roughly half of the signal, in agreement with MARK III [15] and DM2 [4]. The (1295) has been observed by four p experiments [7,1719], and evidence is reported in pp annihilation [2325]. In J/ (1 S ) radiative decay, an (1295) signal is evident in the + wave of the DM2 data [9]. Also BaBar [20] reports evidence for a signal around 1295 MeV in B decays into K . CITATION: K. Nakamura et al. (Particle Data Group), JPG 37 , 075021 (2010) (URL: http://pdg.lbl.gov) July 30, 2010 14:34 2 However, the existence of the (1295) is questioned in Refs. [21] and [22]. The authors claim a single pseudoscalar meson in the 1400 MeV region. This conclusion is based on properties of the wave functions in the 3 P model (and on an unpublished analysis of the annihilation pp 4 ). The pseudoscalar signal around 1400 MeV is then attributed to the first radial excitation of the ....
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rpp2010-rev-eta1440 - 1 THE (1405), (1475), f 1 (1420), AND...

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