HEPData Search

We investigate the four-photon final state produced in γγ colissions. In the π 0 π 0 channel we observe f(1270) production with predominantly helicity 2 and measure a partial width Γ γγ 2.9 +0.6 −0.4 ± keV (independent of assumptions on the helicity). We observe A 2 (1310) production in the π 0 η channel and find a partial width Γ γγ = 0.77 ± 0.18 ± 0.27 KeV (assuming helicity 2). We give an upper limit for f ≈ ηη .

1 data table match query

Table 2

Data read from graph.

Single pi- photoproduction on neutrons in the energy region of the p(11), d(13), s(11) pion-nucleon resonances

Beneventano, M. ; D' Angelo, S. ; De Notaristefani, F. ; et al.

Nuovo Cim.A 19 (1974) 529-547, 1974.

Inspire Record 96708 DOI 10.17182/hepdata.37753

In this note we report the results obtained in a single-photoproduction experiment on neutrons in deuterium, with an experimental apparatus made of scintillation counters, spark chambers and a magnetic spectrometer; the explored energy region is one around the second resonance, that is (500÷900) MeV indicent γ-ray energy. We briefly describe the present situation of the phenomenological analysis of the single photoproduction in the second resonance region and compare the results of an analysis made by us with the results obtained by other authors; in particular the e.m. coupling of theP11 isobaric state found by us is large, in accordance with the results of some other authors.

1 data table match query

Table 1

No description provided.

Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q2 = 1.0-GeV2.

The JLab Hall A collaboration Laveissiere, G. ; Degrande, N. ; Jaminion, S. ; et al.

Phys.Rev.C 69 (2004) 045203, 2004.

Inspire Record 625669 DOI 10.17182/hepdata.25226

Exclusive electroproduction of pi0 mesons on protons in the backward hemisphere has been studied at Q**2 = 1.0 GeV**2 by detecting protons in the forward direction in coincidence with scattered electrons from the 4 GeV electron beam in Jefferson Lab's Hall A. The data span the range of the total (gamma* p) center-of-mass energy W from the pion production threshold to W = 2.0 GeV. The differential cross sections sigma_T+epsilon*sigma_L, sigma_TL, and sigma_TT were separated from the azimuthal distribution and are presented together with the MAID and SAID parametrizations.

12 data tables match query

Table 1

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.975.

Table 2

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.925.

Table 3

Cross section SIG(T) + EPSILON*SIG(L) for COS(THETA*) = -0.875.

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Measurement of the polarized structure function sigma(LT') for pion electroproduction in the Roper resonance region.

The CLAS collaboration Joo, K. ; Smith, L.C. ; Aznauryan, I.G. ; et al.

Phys.Rev.C 72 (2005) 058202, 2005.

Inspire Record 681275 DOI 10.17182/hepdata.25214

The polarized longitudinal-transverse structure function $\sigma_{LT^\prime}$ measures the interference between real and imaginary amplitudes in pion electroproduction and can be used to probe the coupling between resonant and non-resonant processes. We report new measurements of $\sigma_{LT^\prime}$ in the $N(1440){1/2}^+$ (Roper) resonance region at $Q^2=0.40$ and 0.65 GeV$^2$ for both the $\pi^0 p$ and $\pi^+ n$ channels. The experiment was performed at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS) using longitudinally polarized electrons at a beam energy of 1.515 GeV. Complete angular distributions were obtained and are compared to recent phenomenological models. The $\sigma_{LT^\prime}(\pi^+ n)$ channel shows a large sensitivity to the Roper resonance multipoles $M_{1-}$ and $S_{1-}$ and provides new constraints on models of resonance formation.

12 data tables match query

Table 6

Polarized structure function of the reaction E- P --> E- PI0 P for Q**2 = 0.40 and W = 1.30 GeV.

Table 7

Polarized structure function of the reaction E- P --> E- PI0 P for Q**2 = 0.40 and W = 1.34 GeV.

Table 8

Polarized structure function of the reaction E- P --> E- PI0 P for Q**2 = 0.40 and W = 1.38 GeV.

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Single pi+ electroproduction on the proton in the first and second resonance regions at 0.25-GeV2 < Q2 < 0.65-GeV**2 using CLAS.

The CLAS collaboration Egiyan, H. ; Aznauryan, I.G. ; Burkert, V.D. ; et al.

Phys.Rev.C 73 (2006) 025204, 2006.

Inspire Record 707883 DOI 10.17182/hepdata.6748

The ep -> e'pi^+n reaction was studied in the first and second nucleon resonance regions in the 0.25 GeV^2 < Q^2 < 0.65 GeV^2 range using the CLAS detector at Thomas Jefferson National Accelerator Facility. For the first time the absolute cross sections were measured covering nearly the full angular range in the hadronic center-of-mass frame. The structure functions sigma_TL, sigma_TT and the linear combination sigma_T+epsilon*sigma_L were extracted by fitting the phi-dependence of the measured cross sections, and were compared to the MAID and Sato-Lee models.

75 data tables match query

Table 11

Structure functions for Q**2 = 0.30 GeV**2 and W = 1.31 GeV.

Table 12

Structure functions for Q**2 = 0.30 GeV**2 and W = 1.33 GeV.

Table 13

Structure functions for Q**2 = 0.30 GeV**2 and W = 1.35 GeV.

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rivet Analysis
The $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$, 2(\pi^+\pi^-)\eta$, $K^+ K^-\pi^+\pi^-\pi^0$ and $K^+ K^-\pi^+\pi^-\eta$ Cross Sections Measured with Initial-State Radiation

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.

Phys.Rev.D 76 (2007) 092005, 2007.

Inspire Record 758568 DOI 10.17182/hepdata.51824

We study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$, $2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+ K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$ channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from $e^+ e^-\to\omega(782)\pi^+\pi^-$ and study the $\omega(1420)$ and $\omega(1650)$ resonances. In the charmonium region, we observe the $J/\psi$ in all these final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and we measure the corresponding branching fractions.

4 data tables match query

Table 1

Measured cross section for E+ E- --> 2(PI+ PI-) PI0 with statistical errorsonly.

Table 2

Measured cross section for E+ E- --> ETA PI+ PI- with statistical errors only.

Table 3

Measured cross section for E+ E- --> OMEGA PI+ PI- with statistical errors only.

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rivet Analysis
Measurements of e+ e- ---> K+ K- eta, K+ K- pi0 and K0(s) K+- pi-+ cross- sections using initial state radiation events

The BaBar collaboration Aubert, Bernard ; Bona, M. ; Boutigny, D. ; et al.

Phys.Rev.D 77 (2008) 092002, 2008.

Inspire Record 765258 DOI 10.17182/hepdata.50372

This paper reports measurements of processes: e+e- -> gamma KsK+pi-, e+e- -> gamma K+K-pi0, e+e- -> gamma phi eta, and e+e- -> gamma phi pi0. The initial state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ~4.6 GeV. The overall size of the data sample analyzed is 232 fb-1, collected by the BaBar detector running at the PEP-II e+e- storage ring. From the Dalitz plot analysis of the KsK+pi- final state, moduli and relative phase of the isoscalar and the isovector components of the e+e- -> K K*(892) cross section are determined. Parameters of phi and rho recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli and phases of the e+e- -> KsK+pi-, K+K-pi0, phi eta final states. The cross section for the OZI-forbidden process e+e- -> phi pi0, and the J/psi branching fractions to KK*(892) and K+K-eta are also measured.

5 data tables match query

Table 1

The cross section for E+ E- --> K0S K+ PI- + CC with statistical errors only.

Table 2

The cross section for E+ E- --> K+ K- PI0 with statistical errors only.

Table 3

The cross section for E+ E- --> PHI PI0 with statistical errors only.

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Results of the experiments from the neutral detector at the VEPP-2M storage ring in the energy region 2E$_{0}$ = 1.05 - 1.40 GeV

Polarization of the recoil proton from the process gamma n ---> p pi- in deuterium for (theta pi)c.m.=90 degrees in the second-resonance region

Hadron pair production by electron-positron colliding beams

Production of $\pi^0 \pi^0$ and $\pi^0 \eta$ in Photon - Photon Collisions

Single pi- photoproduction on neutrons in the energy region of the p(11), d(13), s(11) pion-nucleon resonances

Backward electroproduction of pi0 mesons on protons in the region of nucleon resonances at four momentum transfer squared Q2 = 1.0-GeV2.

Measurement of the polarized structure function sigma(LT') for pion electroproduction in the Roper resonance region.

Single pi+ electroproduction on the proton in the first and second resonance regions at 0.25-GeV2 < Q2 < 0.65-GeV**2 using CLAS.

rivet Analysis
The $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$, 2(\pi^+\pi^-)\eta$, $K^+ K^-\pi^+\pi^-\pi^0$ and $K^+ K^-\pi^+\pi^-\eta$ Cross Sections Measured with Initial-State Radiation

rivet Analysis
Measurements of e+ e- ---> K+ K- eta, K+ K- pi0 and K0(s) K+- pi-+ cross- sections using initial state radiation events