Threshold π0 photoproduction on transverse polarised protons at MAMI

The MAINZ-A2 collaboration Schumann, S. ; Otte, P.B. ; Akondi, C.S. ; et al.
Phys.Lett.B 750 (2015) 252-258, 2015.
Inspire Record 1394326 DOI 10.17182/hepdata.126972

Polarisation-dependent differential cross sections σT associated with the target asymmetry T have been measured for the reaction γp→→pπ0 with transverse target polarisation from π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol target with the Crystal Ball / TAPS detector set-up and the Glasgow photon tagging system at the Mainz Microtron MAMI. Results for σT have been used in combination with our previous measurements of the unpolarised cross section σ0 and the beam asymmetry Σ for a model-independent determination of S - and P -wave multipoles in the π0 threshold region, which includes for the first time a direct determination of the imaginary part of the E0+ multipole.

18 data tables

Target asymmetry T for c.m. cos(Theta_pi0)= 0.996

Target asymmetry T for c.m. cos(Theta_pi0)= 0.966

Target asymmetry T for c.m. cos(Theta_pi0)= 0.906

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Measurement of the transverse target and beam-target asymmetries in $\eta$ meson photoproduction at MAMI

The A2 at MAMI collaboration Akondi, C.S. ; Annand, J.R.M. ; Arends, H.J. ; et al.
Phys.Rev.Lett. 113 (2014) 102001, 2014.
Inspire Record 1310837 DOI 10.17182/hepdata.116552

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the $\vec \gamma \vec p\to\eta p$ reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. All existing model predictions fail to reproduce the new data indicating a significant impact on our understanding of the underlying dynamics of $\eta$ meson photoproduction. The peculiar nodal structure observed in existing T data close to threshold is not confirmed.

24 data tables

Target asymmetry T for c.m. energy W= 1.4969 GeV

Target asymmetry T for c.m. energy W= 1.5156 GeV

Target asymmetry T for c.m. energy W= 1.5341 GeV

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Measurement of the g p -> K^0 Sigma^+ reaction with the Crystal Ball/TAPS detectors at the Mainz Microtron

The A2 collaboration Aguar-Bartolome, P. ; Annand, J.R.M. ; Arends, H.J. ; et al.
Phys.Rev.C 88 (2013) 044601, 2013.
Inspire Record 1237227 DOI 10.17182/hepdata.64391

The g p -> K^0 Sigma^+ reaction has been measured from threshold to Eg=1.45 GeV (W_cm=1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3pi^0 p final state, by assuming K^0_S -> pi^0 pi^0 and Sigma^+ -> pi^0 p. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve empirical knowledge about the g p -> K^0 Sigma^+ reaction in the measured energy range. The results are compared to previous measurements and model predictions. It is demonstrated that adding the present g p -> K^0 Sigma^+ results to existing data allowed a better description of this reaction with various models.

4 data tables

The differential cross section for photon energies 1125, 1175 and 1225 MeV.

The differential cross section for photon energies 1275, 1325, 1375 and 1425 MeV.

The recoil polarization of the SIGMA+ for photon energy 1125, 1175 and 1225 MeV.

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Accurate Test of Chiral Dynamics in the \boldmath$\gamma p \rightarrow \pi^0p$ Reaction

The A2 & CB-TAPS collaborations Hornidge, D. ; Aguar Bartolome, P. ; Annand, J.R.M. ; et al.
Phys.Rev.Lett. 111 (2013) 062004, 2013.
Inspire Record 1203736 DOI 10.17182/hepdata.127967

A precision measurement of the differential cross sections $d\sigma/d\Omega$ and the linearly polarized photon asymmetry $\Sigma \equiv (d\sigma_\perp - d\sigma_\parallel) \slash (d\sigma_\perp + d\sigma_\parallel)$ for the $\vec{\gamma} p \rightarrow \pi^0p$ reaction in the near-threshold region has been performed with a tagged photon beam and almost $4\pi$ detector at the Mainz Microtron. The Glasgow-Mainz photon tagging facility along with the Crystal Ball/TAPS multi-photon detector system and a cryogenic liquid hydrogen target were used. These data allowed for a precise determination of the energy dependence of the real parts of the $S$- and all three $P$-wave amplitudes for the first time and provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of agreement with experiment.

56 data tables

Differential cross section at W=1.0752268 GeV

Differential cross section at W=1.0773190 GeV

Differential cross section at W=1.0793464 GeV

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Measurement of $\pi^0 \Lambda$, $\bar{K}^0 n$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions for $p_{K^-}$ between 514 and 750 MeV/$c$

Prakhov, S. ; Nefkens, B.M.K. ; Bekrenev, V. ; et al.
Phys.Rev.C 80 (2009) 025204, 2009.
Inspire Record 804864 DOI 10.17182/hepdata.52376

The results on the differential cross sections as well as the polarizations of $\Lambda$ and $\Sigma^0$ have been obtained for $\bar{K}^0 n$, $\pi^0 \Lambda$, and $\pi^0 \Sigma^0$ production in $K^- p$ interactions at eight $K^-$ momenta between 514 and 750 MeV/$c$. The study is conducted by measuring multiphoton final states with the Crystal Ball spectrometer, using a $K^-$ beam from the Alternating Gradient Synchrotron of BNL. The results improve substantially the existing data, allowing a detailed reexamination of the $\Lambda^*$ and $\Sigma^*$ states in our energy range.

11 data tables

Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.

Differential cross section for the K- P --> KBAR0 N reaction. Errors are statistical only.

Differential cross section for the K- P --> PI0 LAMBDA reaction. Errors are statistical only.

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Reaction K- p --> pi0 pi0 lambda from p(K-) = 514-MeV/c to 750-MeV/c.

Prakhov, S. ; Nefkens, B.M.K. ; Allgower, C.E. ; et al.
Phys.Rev.C 69 (2004) 042202, 2004.
Inspire Record 650074 DOI 10.17182/hepdata.25228

Reaction K−p→π0π0Λ was measured at eight incident K− momenta between 514 and 750MeV∕c using the Crystal Ball multiphoton spectrometer. The reaction dynamics are displayed in total cross sections, Dalitz plots, invariant-mass spectra, production angular distributions, and the Λ polarization. The π0π0Λ production is dominated by the π0Σ0(1385) intermediate state; no trace of other light Σ∗ states is observed, and the role of the f0(600) meson appears to be insignificant. A striking similarity is seen between K−p→π0π0Λ and π−p→π0π0n; this can be understood as a consequence of dynamical flavor symmetry.

5 data tables

Measured cross section. Statistical errors only.

Differential cross section for the di-pion system in the c.m. system for incident momenta 514 to 629 MeV.

Differential cross section for the di-pion system in the c.m. system for incident momenta 659 to 750 MeV.

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Measurement of K- p --> eta Lambda near threshold

The Crystal Ball collaboration Starostin, A. ; Nefkens, B.M.K. ; Berger, E. ; et al.
Phys.Rev.C 64 (2001) 055205, 2001.
Inspire Record 569202 DOI 10.17182/hepdata.25269

We present measurements of the differential and total cross sections and the Λ polarization for the reaction K−p→ηΛ from threshold to pK−=770MeV/c, with much better precision than previous measurements. Our cross-section data show a remarkable similarity to the SU(3) flavor-related π−p→ηn cross-section results. The reaction K−p→ηΛ at threshold is dominated by formation of the intermediate Λ(1670)12− state.

5 data tables

Total cross section measurement for K- P --> ETA LAMBDA. Errors shown are statistical only.

Differential cross sections DSIG/DOMEGA for K- P --> ETA LAMBDA. Errors shown are statistical only.

Differential cross sections DSIG/DOMEGA for K- P --> ETA LAMBDA. Errors shown are statistical only.

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The Reaction d (polarized) p ---> He-3 pi0 near threshold

Nikulin, V.N. ; Boudard, A. ; Clajus, M. ; et al.
Phys.Rev.C 54 (1996) 1732-1740, 1996.
Inspire Record 421018 DOI 10.17182/hepdata.25833

Angular distributions for the differential cross section and three deuteron analyzing powers iT11, T20, and T22 of the reaction d→p→3Heπ0 have been measured over the whole angular domain at 20 energies close to threshold (0.03<Tπc.m.<10.2 MeV). The differential cross section and tensor analyzing power T20 both show strong variation in energy and angle due to interference between S- and P-wave pion production, whereas iT11 and T22 remain consistent with zero over the whole experimental range. All the data at different energies and angles fall on universal curves when plotted as functions of the single variable pπcosΘ, evaluated in the c.m. The broad features of the results are in line with theoretical expectations. © 1996 The American Physical Society.

1 data table

No description provided.


Measurement of the left-right asymmetry in pi- p ---> gamma n from 301-GeV/c to 625-MeV/c at backward angles

Kim, G.J. ; Engelage, J. ; Nefkens, B.M.K. ; et al.
Phys.Rev.D 43 (1991) 687-695, 1991.
Inspire Record 316108 DOI 10.17182/hepdata.22828

The left-right asymmetry of π−p→γn has been measured using a transversely polarized target at seven pion momenta from 301 to 625 MeV/c, mostly at photon angles of 90° and 110° c.m. The final-state γ and neutron were detected in coincidence. Neutrons were recorded in two arrays of plastic scintillators and the γ's in two matching sets of lead-glass counters. The results are compared with the predictions from the two most recent single-pion photoproduction partial-wave analyses. The agreement with the analysis of Arai and Fujii is poor, casting some doubt on the correctness of their values for the radiative decay amplitude of the neutral Roper resonance which are used widely. The agreement is much better with the results of the VPI analysis. Also, a comparison is made with the recoil-proton polarization data from the inverse reaction measured at 90° with a deuterium target. It reveals substantial discrepancies, indicating the shortcomings of the deuterium experiments for neutron target experiments. Our data are also compared with several bag-model calculations.

7 data tables

No description provided.

No description provided.

No description provided.

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Analyzing power for pi- p charge exchange in the backward hemisphere from 301-MeV/c to 625-MeV/c and a test of pi N partial wave analyses

Kim, G.J. ; Arends, J. ; Engelage, J. ; et al.
Phys.Rev.D 41 (1990) 733-743, 1990.
Inspire Record 301242 DOI 10.17182/hepdata.22935

The analyzing power of π−p→π0n has been measured for pπ=301−625 MeV/c with a transversely polarized target, mainly in the backward hemisphere. The final-state neutron and a γ from the π0 were detected in coincidence with two counter arrays. Our results are compared with predictions of recent πN partial-wave analyses by the groups of Karlsruhe-Helsinki, Carnegie-Mellon University-Lawrence Berkeley Laboratory (CMU-LBL), and Virginia Polytechnic Institute (VPI). At the lower incident energies little difference is seen among the three analyses, and there is excellent agreement with our data. At 547 MeV/c and above, our data strongly favor the VPI phases, and disagree with Karlsruhe-Helsinki and CMU-LBL analyses, which are the source of the πN resonance parameters given in the Particle Data Group table.

7 data tables

Axis error includes +- 5/5 contribution (Uncertainty in background normalisation).

Axis error includes +- 5/5 contribution (Uncertainty in background normalisation).

Axis error includes +- 5/5 contribution (Uncertainty in background normalisation).

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