Measurement of e p --> e' p pi+ pi- and baryon resonance analysis.

The CLAS collaboration Ripani, M. ; Burkert, V.D. ; Mokeev, V. ; et al.
Phys.Rev.Lett. 91 (2003) 022002, 2003.
Inspire Record 600451 DOI 10.17182/hepdata.11116

The cross section for the reaction $ e p \to e^{\prime} p \pi^{+} \pi^{-}$ was measured in the resonance region for 1.4$<$W$<$2.1 GeV and 0.5$<Q^{2}<$1.5 GeV$^{2}$/c$^{2}$ using the CLAS detector at Jefferson Laboratory. The data shows resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on $N^{*}$ and $\Delta$ states shows an evident discrepancy. A better description of the data is obtained either by a sizeable change of the properties of the $P_{13}$(1720) resonance or by introducing a new baryon state, not reported in published analyses.

84 data tables

Measured cross section DSIG/DM(PI+PI-) for the W range 1400 to 1425GeV.

Measured cross section DSIG/DM(PI+PI-) for the W range 1425 to 1450GeV.

Measured cross section DSIG/DM(PI+PI-) for the W range 1450 to 1475GeV.

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Eta photoproduction on the proton for photon energies from 0.75-GeV to 1.95-GeV

The CLAS collaboration Dugger, M. ; Ritchie, B.G. ; Ball, J. ; et al.
Phys.Rev.Lett. 89 (2002) 222002, 2002.
Inspire Record 603904 DOI 10.17182/hepdata.19406

Differential cross sections for γp→ηp have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75  GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass ∼1.8  GeV couples to the ηN channel.

6 data tables

Cross sections for photon energies 0.775 to 0.925 GeV.

Cross sections for photon energies 0.975 to 1.125 GeV.

Cross sections for photon energies 1.175 to 1.325 GeV.

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Exclusive electroproduction of Phi mesons at 4.2-GeV.

The CLAS collaboration Lukashin, K. ; Smith, E.S. ; Adams, G.S. ; et al.
Phys.Rev.C 64 (2001) 059901, 2001.
Inspire Record 552246 DOI 10.17182/hepdata.38589

We studied the exclusive reaction e p --> e' p' phi using the phi --> K^+ K^- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CLAS detector at Jefferson Lab. Our experiment covers the range in Q^2 from 0.7 to 2.2 GeV^2, and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of phi production on the proton. Our measurement shows the expected decrease of the t-slope with the vector meson formation time c Delta tau below 2 fm. At = 0.6 fm, we measure b_phi = 2.27 +- 0.42 GeV^-2. The cross section dependence on W as W^{0.2+-0.1} at Q^2 = 1.3 GeV^2 was determined by comparison with phi production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction.

3 data tables

Slope of the DSIG/DT distribution in different Q**2 regions.

Cross section as a function of Q**2 and W.

The differential cross section for exclusive PHI electroproduction off the photon, (TP=T-TMIN).