Photoproduction of eta mesons off protons for 0.75-GeV < E(gamma) < 3-GeV.

The CB-ELSA collaboration Crede, Volker ; Bartholomy, Olivia ; Anisovich, A. ; et al.
Phys.Rev.Lett. 94 (2005) 012004, 2005.
Inspire Record 633776 DOI 10.17182/hepdata.41904

Total and differential cross sections for the reaction p(gamma, eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into p eta. At medium energies we find evidence for a new resonance N(2070)D15 with (mass, width) = (2068+-22, 295+-40) MeV. At photon energies above 1.5 GeV, a strong peak in forward direction develops, signalling the exchange of vector mesons in the t channel.

10 data tables

Total cross section determined by summing the angular bins and extrapolating outside the angular range of the experiment.

Differential cross section as a function of c.m. angle for the photon energy range 750 to 950 GeV.

Differential cross section as a function of c.m. angle for the photon energy range 950 to 1150 GeV.

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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.

14 data tables

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 300 to 425 GeV.

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

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K^0 pi^0 Sigma^+ and K^*0 Sigma^+ photoproduction off the proton

The CBELSA/TAPS collaboration Nanova, M. ; Bacelar, J.C.S. ; Bantes, B. ; et al.
Eur.Phys.J.A 35 (2008) 333-342, 2008.
Inspire Record 781382 DOI 10.17182/hepdata.51372

The exclusive reactions $\gamma p \to K^{*0} \Sigma^+(1189)$ and $\gamma p \to K^{0} \pi^{0}\Sigma^+(1189)$, leading to the p 4$\pi^{0}$ final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5 GeV. The experiment has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were combined to a photon detector system of almost 4$\pi$ geometrical acceptance. Differential and total cross sections are reported. At energies close to the threshold, a flat angular distribution has been observed for the reaction $\gamma p\to K^{0} \pi^{0}\Sigma^+$ suggesting dominant s-channel production. $\Sigma^*(1385)$ and higher lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions of the reaction $\gamma p \to K^{*0}\Sigma^+$ indicates a $t$-channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical predictions.

13 data tables

Differential cross section D(SIG)/DCOS(THETA(SIG+)) for the GAMMA P --> K0 PI0 SIGMA+ reaction for beam energies 1500-1700 and 1700-1850 MeV.

Differential cross section D(SIG)/DCOS(THETA(SIG+)) for the GAMMA P --> K0 PI0 SIGMA+ reaction for beam energies 1850-2000 and 2000-2150 MeV.

Differential cross section D(SIG)/DCOS(THETA(SIG+)) for the GAMMA P --> K0 PI0 SIGMA+ reaction for beam energies 2150-2300 and 2300-2500 MeV.

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Quasi-free photoproduction of eta-mesons of the neutron

The CBELSA & TAPS collaborations Jaegle, I. ; Mertens, T. ; Anisovich, A.V. ; et al.
Phys.Rev.Lett. 100 (2008) 252002, 2008.
Inspire Record 784698 DOI 10.17182/hepdata.50884

Quasi-free photoproduction of eta-mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta-mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasi-free n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta-production off the neutron shows a pronounced bump-like structure at W=1.68 GeV (E_g ~ 1 GeV), which is absent for the proton.

22 data tables

Measured value of the quasi-free eta cross section off protons and neutrons as a function of incident photon energy.

Ratio of the measured quasi-free neutron to proton cross sections as a function of incident photon energy.

Measured angular distribution for an incident photon energy of 0.700 GeV.

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Photoproduction of $\eta$ and $\eta\prime$ Mesons off Protons

The CBELSA/TAPS collaboration Crede, V. ; McVeigh, A. ; Anisovich, A.V. ; et al.
Phys.Rev.C 80 (2009) 055202, 2009.
Inspire Record 836340 DOI 10.17182/hepdata.53229

Total and differential cross sections for $\eta$ and $\eta ^\prime$ photoproduction off the proton have been determined with the CBELSA/TAPS detector for photon energies between 0.85 and 2.55 GeV. The $\eta$ mesons are detected in their two neutral decay modes, $\eta\to\gamma\gamma$ and $\eta\to 3\pi^0\to 6\gamma$, and for the first time, cover the full angular range in $\rm cos \theta_{cm}$ of the $\eta$ meson. These new $\eta$ photoproduction data are consistent with the earlier CB-ELSA results. The $\eta ^\prime$ mesons are observed in their neutral decay to $\pi^0\pi^0\eta\to 6\gamma$ and also extend the coverage in angular range.

56 data tables

Differential cross section for ETA production at incident photon energy 0.850 to 0.900 GeV.

Differential cross section for ETA production at incident photon energy 0.900 to 0.950 GeV.

Differential cross section for ETA production at incident photon energy 0.950 to 1.000 GeV.

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Study of the reaction $\gamma p\to p\pi^0\eta$

The CB-ELSA collaboration Horn, I. ; Anisovich, A.V. ; Anton, G. ; et al.
Eur.Phys.J.A 38 (2008) 173-186, 2008.
Inspire Record 789175 DOI 10.17182/hepdata.54384

The reaction $\gamma p\to p\pi^0\eta$ has been studied with the CBELSA detector at the tagged photon beam of the Bonn electron stretcher facility. The reaction shows contributions from $\Delta^+(1232)\eta$, $N(1535)^+\pi^0$ and $pa_0(980)$ as intermediate states. A partial wave analysis suggests that the reaction proceeds via formation of six $\Delta$ resonances, $\Delta(1600)P_{33}$, $\Delta(1920)P_{33}$, $\Delta(1700)D_{33}$, $\Delta(1940)D_{33}$, $\Delta(1905)F_{35}$, $\Delta(2360)D_{33}$, and two nucleon resonances $N(1880)P_{11}$ and $N(2200)P_{13}$, for which pole positions and decay branching ratios are given.

7 data tables

Total cross section for GAMMA P --> P PI0 ETA.

Differential cross sections as a function of the angles of the individual final state particles for the W range 1.7 to 1.9 GeV.. Errors shown are statistical only.

Differential cross sections as a function of the angles of the individual final state particles for the W range 1.9 to 2.1 GeV.. Errors shown are statistical only.

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$R$ value measurements for $e^+e^-$ annihilation at 2.60, 3.07 and 3.65 GeV

The BES collaboration Ablikim, M. ; Bai, J.Z. ; Bai, Y. ; et al.
Phys.Lett.B 677 (2009) 239-245, 2009.
Inspire Record 814778 DOI 10.17182/hepdata.51953

Using a data sample with a total integrated luminosity of 10.0 pb$^{-1}$ collected at center-of-mass energies of 2.6, 3.07 and 3.65 GeV with BESII, cross sections for $e^+e^-$ annihilation into hadronic final states ($R$ values) are measured with statistical errors that are smaller than 1%, and systematic errors that are about 3.5%. The running strong interaction coupling constants $\alpha_s^{(3)}(s)$ and $\alpha_s^{(5)}(M_Z^2)$ are determined from the $R$ values.

1 data table

R values.


Observation of an ABC effect in proton-proton collisions

Dymov, S. ; Hartmann, M. ; Kacharava, A. ; et al.
Phys.Rev.Lett. 102 (2009) 192301, 2009.
Inspire Record 812534 DOI 10.17182/hepdata.51593

The cross section for inclusive multipion production in the pp->ppX reaction was measured at COSY-ANKE at four beam energies, 0.8, 1.1, 1.4, and 2.0 GeV, for low excitation energy in the final pp system, such that the diproton quasi-particle is in the 1S0 state. At the three higher energies the missing mass Mx spectra show a strong enhancement at low Mx, corresponding to an ABC effect that moves steadily to larger values as the energy is increased. Despite the missing-mass structure looking very different at 0.8 GeV, the variation with Mx and beam energy are consistent with two-pion production being mediated through the excitation of two Delta(1232) isobars, coupled to S-- and D-- states of the initial pp system.

4 data tables

The P P --> P P X differential cross section as a function of the square ofthe missing mass (X) at incident beam energy of 0.8 GeV.

The P P --> P P X differential cross section as a function of the square ofthe missing mass (X) at incident beam energy of 1.1 GeV.

The P P --> P P X differential cross section as a function of the square ofthe missing mass (X) at incident beam energy of 1.4 GeV.

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Shape of the Lambda(1405) hyperon measured through its Sigma0 pi0 decay.

Zychor, I. ; Buscher, M. ; Hartmann, M. ; et al.
Phys.Lett.B 660 (2008) 167-171, 2008.
Inspire Record 750092 DOI 10.17182/hepdata.51635

The pp -> p K+ Y0 reaction has been studied for hyperon masses m(Y0)<1540 MeV/c2 at COSY-J\'ulich by using a 3.65 GeV/c circulating proton beam incident on an internal hydrogen target. Final states comprising two protons, one positively charged kaon and one negatively charged pion have been identified with the ANKE spectrometer. Such configurations are sensitive to the production of the ground state Lambda and Sigma0 hyperons as well as the Sigma0(1385) and Lambda(1405) resonances. Applying invariant- and missing-mass techniques, the two overlapping excited states can be separated unambiguously. The shape and position of the Lambda(1405) distribution, reconstructed cleanly from its Sigma0 pion0 decay, are similar to those found in other production modes and there is no obvious mass shift. This finding constitutes a challenging test for models that predict Lambda(1405) to be a two-state resonance.

2 data tables

Cross section for SIGMA(1385)0 production.

Cross section for LAMBDA(1405) production.


Production of upsilon(1S) mesons from chi(b) decays in p anti-p collisions at S**(1/2) = 1.8-TeV

The CDF collaboration Affolder, T. ; Akimoto, H. ; Akopian, A. ; et al.
Phys.Rev.Lett. 84 (2000) 2094-2099, 2000.
Inspire Record 508395 DOI 10.17182/hepdata.50106

We have reconstructed the radiative decays $\chi_{b}(1P) \to \Upsilon(1S) \gamma $ and $\chi_{b}(2P) \to \Upsilon(1S) \gamma $ in $p \bar{p}$ collisions at $\sqrt{s} = 1.8$ TeV, and measured the fraction of $\Upsilon(1S)$ mesons that originate from these decays. For $\Upsilon(1S)$ mesons with $p^{\Upsilon}_{T}>8.0$ GeV/$c$, the fractions that come from $\chi_{b}(1P)$ and $\chi_{b}(2P)$ decays are $(27.1\pm6.9(stat)\pm4.4(sys))%$ and $(10.5\pm4.4(stat)\pm1.4(sys))%$, respectively. We have derived the fraction of directly produced $\Upsilon(1S)$ mesons to be $(50.9\pm8.2(stat)\pm9.0(sys))%$.

1 data table

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