Study on the reaction of γp→f1(1285)p in Regge-effective Lagrangian approach

Abstract

The production of the f1(1285) resonance in the reaction of γp → f1(1285)p is investigated within a Regge-effective Lagrangian approach. Besides the contributions of the t-channel ρ and ω trajectories exchanges, we also take into account the contributions of s/u-channel N (2300) terms, s/u-channel nucleon terms, and the contact term. By fitting to the CLAS data, we find that the s-channel N (2300) term plays an important role in this reaction. We predict the total cross section for this reaction, and find a clear bump structure around W = 2.3 GeV, which is associated with the N (2300) state. The reaction of γp → f1(1285)p could be useful to further study of the N (2300) experimentally.PACS numbers: 13.60. Le, 14.20.Gk, 11.10.Ef I. INTRODUCTIONIt has been known that the nucleon is a bound state of three valence quarks since 1970s. Many nucleon resonances, referred as N * , have been observed [1], the properties of nucleon resonances are the important issues in hadron physics, and attract lots of attentions [2][3][4]. For the nucleon resonances with masses below 2 GeV, their properties have been widely investigated in literature. However, the current knowledge on the properties of excited nucleon states with masses above 2 GeV is scarce. On the other hand, many missing N * s, predicted by the constituent quark models are not yet found [5].Recently, the CLAS Collaboration has measured the f 1 (1285) meson for the first time in photoproduction from a proton target, and presented the f 1 (1285) differential photoproduction cross section into ηπ + π − final states from the threshold up to a center-of-mass (c.m.) energy of W = 2.8 GeV [6]. A cross section comparison for γp → η ′ (958)p → ηπ + π − p and γp → f 1 (1285)p → ηπ + π − p at W = 2.55 GeV in Fig. 10 of Ref. [6] shows that the η ′ (958) cross section exhibits much stronger tand u-channel signatures in the angle dependence than dose the one of f 1 (1285), which is quite flat. This may imply that the f 1 (1285) photoproduction mechanism is not dominated alone by t-channel production processes.Before the experimental study on γp → f 1 (1285)p [6], there are several theoretical works on this reaction. Within the Regge-model, considering the exchanges of t-channel ρ and ω trajectories, Kochelev et al. calculated the differential cross sections of γp → f 1 (1285)p [7]. Comparison of the Regge-model calculations and the CLAS data shows the t-channel production process alone does not reproduce the CLAS measurements.

Photoproductions of f1(1285) and η′Yu1, Kong2 2020Phys. Rev. D2030View full textAdd to dashboardCite

“…However, it is interesting to see in Ref. [34] that the total cross section is given similarly to our case in shape and magnitude, insofar as the model prediction agrees with differential cross section data in its own way. The respective contributions of ρ and ω exchanges are shown with the same notations.…”

“…The role of nucleon resonance N Ã ð2300Þð1=2 þ Þ together with the nucleon in the s and u channels is discussed to account for the u-channel rise at ffiffi ffi s p ¼ 2.65 and 2.75. [34]. Nevertheless, it should be pointed out that the results from these models follow the dependence on the cutoff mass of the form factors, which is the point that is quite different from the current calculation.…”

Consistent analysis of f1(1285) meson form factors

“…Therefore, the probability of these processes can be sensitive to the f 1 meson internal structure, i.e., to the dependence of the form factors on photon virtualities. At present, there are a few experimental [2][3][4][5][6][7] and theoretical [8][9][10][11][12][13][14][15][16][17] results on production and decays of f 1 meson. Unfortunately, QCD cannot predict now the shapes of the corresponding form factors at moderate photon virtualities.…”

ϕ(2170) production in the process γp→ηϕp

“…for the exchanged baryons [27,28,30,54], where the q and M are the four-momentum and the mass of the exchanged hadron, respectively. Indeed, the values of the cutoff parameters can be directly related to the hadron size.…”