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

Edwards, C. ; Partridge, Richard ; Peck, C. ; et al.
Phys.Lett.B 110 (1982) 82-86, 1982.
Inspire Record 168793 DOI 10.17182/hepdata.30959

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

Data read from graph.


A Measurement of the Cross-Section for Four Pion Production in gamma gamma Collisions at SPEAR

Burke, D.L. ; Abrams, G.S. ; Alam, M.S. ; et al.
Phys.Lett.B 103 (1981) 153-156, 1981.
Inspire Record 165016 DOI 10.17182/hepdata.31168

We present a measurement of the cross section for the reaction e + e − → e + e − π + π − π + π − at SPEAR. This channel is found to be large and dominated by the process γγ → ϱ 0 ϱ 0 → π + π − π + π − . The cross section, which is small just above the four-pion threshold, exhibits a large enhancement near the ϱ 0 ϱ 0 threshold.

1 data table match query

Axis error includes +- 0.0/0.0 contribution (THE QUOTED ERRORS INCLUDE VARIOUS SYSTEMATIC ERRORS ADDED QUADRATICALLY).


Total cross-section measurement for the three double pion production channels on the proton

Braghieri, A ; Murphy, L.Y ; Ahrens, J ; et al.
Phys.Lett.B 363 (1995) 46-50, 1995.
Inspire Record 382744 DOI 10.17182/hepdata.28464

The total cross sections for the three γp → Nππ reactions have been measured for photon energies from 400 to 800 MeV. The γ p → p π 0 π 0 and γ p → n π + π 0 cross sections have never been measured before while the γ p → p π + π − results are much improved compared to earlier data. These measurements were performed with the large acceptance hadronic detector DAPHNE, at the tagged photon beam facility of the MAMI microtron in Mainz.

3 data tables match query

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Neutral pion photoproduction off protons in the energy range 0.3-GeV < E(gamma) < 3-GeV

The CB-ELSA collaboration Bartholomy, O. ; Crede, V. ; van Pee, H. ; et al.
Phys.Rev.Lett. 94 (2005) 012003, 2005.
Inspire Record 654179 DOI 10.17182/hepdata.41902

Single pi0 photoproduction has been studied with the CB-ELSA experiment at Bonn using tagged photon energies between 0.3 and 3.0 GeV. The experimental setup covers a very large solid angle of about 98% of 4 pi. Differential cross sections (d sigma)/(d Omega) have been measured. Complicated structures in the angular distributions indicate a variety of different resonances being produced in the s channel intermediate state gamma p --> N* (Delta*) --> p pi0. A combined analysis including the data presented in this letter along with other data sets reveals contributions from known resonances and evidence for a new resonance N(2070)D15.

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Total cross section for GAMMA P --> P PI0 obtained by integration of the angular distributions and extrapolation into the forward and backward regions using the PWA result.

Differential cross section as a function of c.m. angle for the photon energy range 425 to 550 GeV.


Total cross-section measurement of the gamma n ---> p pi- pi0 reaction

Zabrodin, A. ; Audit, G. ; Beck, R. ; et al.
Phys.Rev.C 55 (1997) R1617-R1620, 1997.
Inspire Record 439886 DOI 10.17182/hepdata.47015

The total cross section for the γn→pπ−π0 reaction has been measured over the photon energy range 450–800 MeV at the 855 MeV MAMI Microtron in Mainz with the large acceptance detector DAPHNE and using a deuterium target. As expected, this reaction has a very similar cross section to the γp→nπ+π0 channel and its amplitude is strongly underestimated by the existing double pion photoproduction models.

1 data table match query

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Analysis of the pi+ pi- pi+ pi- and pi+ pi0 pi- pi0 final states in quasi-real two-photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 638 (2006) 128-139, 2006.
Inspire Record 705125 DOI 10.17182/hepdata.48674

The reactions gamma gamma -> pi^+pi^-pi^+pi^- and gamma gamma -> pi^+pi^0pi^-pi^0 are studied with the L3 detector at LEP in a data sample collected at centre-of-mass energies from 161GeV to 209GeV with a total integrated luminosity of 698/pb. A spin-parity-helicity analysis of the rho^0 rho^0 and rho^+ rho^- systems for two-photon centre-of-mass energies between 1GeV and 3GeV shows the dominance of the spin-parity state 2+ with helicity 2. The contribution of 0+ and 0- spin-parity states is also observed, whereas contributions of 2- states and of a state with spin-parity 2+ and zero helicity are found to be negligible.

4 data tables match query

Cross section for 4PI and (RHO0 RHO0) production.

Cross section for 4PI and (RHO+ RHO-) production.

Spin parity analysis fits for RHO0 RHO0.

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Measurement of exclusive rho+ rho- production in high-Q**2 two-photon collisions at LEP

The L3 collaboration Achard, P. ; Adriani, O. ; Aguilar-Benitez, M. ; et al.
Phys.Lett.B 597 (2004) 26-38, 2004.
Inspire Record 654177 DOI 10.17182/hepdata.48589

Exclusive rho^+ rho^- production in two-photon collisions involving a single highly-virtual photon is studied with data collected at LEP at centre-of-mass energies 89 GeV &lt; \sqrt{s} &lt; 209 GeV with a total integrated luminosity of 854.7 pb^-1. The cross section of the process gamma gamma^* -> rho^+ rho^- is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 1.2 GeV^2 &lt; Q^2 &lt; 30 GeV^2 and 1.1 GeV &lt; W_gg &lt; 3 GeV. The \rho^+\rho^- production cross section is found to be of the same magnitude as the cross section of the process gamma gamma^* -> rho^0 rho^0, measured in the same kinematic region by L3, and to have similar W_gg and Q^2 dependences.

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Cross sections for the reaction E+ E- --> E+ E- RHO+ RHO-. The differentialcross sections are corrected to the centre of each bin.

Cross sections for the two photon production of RHO+ RHO-.

Differential cross section for the process E+ E- --> E+ E- (RHO+ PI- PI0 + RHO+ RHO- PI0 PI0) corrected to bin centre.

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Measurement of the reaction gamma p ---> K0 Sigma+ at photon energies up to 2.6-GeV

Lawall, R. ; Barth, J. ; Bennhold, C. ; et al.
Eur.Phys.J.A 24 (2005) 275-286, 2005.
Inspire Record 680746 DOI 10.17182/hepdata.43595

The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.

1 data table match query

Polarization parameter of the SIGMA+ as a function of angle in two photon energy ranges.


Observation of Spin Parity 2+ Dominance in the Reaction $\gamma \gamma \to \rho^0 \rho^0$ Near Threshold

The ARGUS collaboration Albrecht, H. ; Ehrlichmann, H. ; Glaser, R. ; et al.
Z.Phys.C 50 (1991) 1-10, 1991.
Inspire Record 296187 DOI 10.17182/hepdata.45136

The reactionγγ→π+π−π+π− has been studied with the ARGUS detector. The rate in the invariant mass region below 1.8 GeV/c2 is found to be largely due toρ0ρ0 production. A spin-parity analysis shows a dominance of the partial wave (JP,Jz)=(2+, 2) with a small admixture fromJP=0+. The contribution of negative parity states is consistent with zero. The large ratio of cross sectionsσ(γγ→ρ0ρ0)/σ(γγ→ρ+ρ−)≃4, and the dominance of theJP=2+ wave in the reactionγγ→ρ0ρ0 is a signature consistent with the production of an exotic (I=2) resonance.

4 data tables match query

Statistical errors only.. Cross-section assuming phase-space distribution, as obtained by a 7 parameter fit.

Statistical errors only.. Cross-section assuming phase-space distribution, as obtained by a 7 parameter fit.

Partial wave components for the (JP,JZ) contribution to RHO0 RHO0 cross section.

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Electroproduction of $\pi^0$ Mesons in the Resonance Region at $q^2=1.0$-{GeV}/$c^2$

Latham, A. ; Allison, John ; Booth, I. ; et al.
Nucl.Phys.B 189 (1981) 1-14, 1981.
Inspire Record 155783 DOI 10.17182/hepdata.43833

Data are presented for the reaction ep → ep π 0 at a nominal momentum transfer squared of 1.0 (GeV/ c ) 2 . The data were obtained using an extracted electron beam from NINA and two magnetic spectrometers for coincidence detection of the electron and proton. Differential cross sections have been measured for isobar masses in the range 1.19–1.73 GeV/ c 2 .

6 data tables match query

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Data from forward bins.

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