Measurement of spin density matrix elements in Λ(1520) photoproduction at 8.2–8.8 GeV

The GlueX collaboration Adhikari, S. ; Akondi, C.S. ; Albrecht, M. ; et al.
Phys.Rev.C 105 (2022) 035201, 2022.
Inspire Record 1892395 DOI 10.17182/hepdata.132920

We report on the measurement of spin density matrix elements of the $\Lambda(1520)$ in the photoproduction reaction $\gamma p\rightarrow \Lambda(1520)K^+$, via its subsequent decay to $K^{-}p$. The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Lab using a linearly polarized photon beam with $E_\gamma =$ 8.2-8.8 GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, $-(t-t_\text{0})$. We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in $\Lambda(1520)$ photoproduction.

10 data tables

Numerical results for all presented SDMEs. The first uncertainty is statistical, the second systematic

Numerical results for all presented natural and unnatural combinations, and covariances between $\rho^1_{11}$ and $\rho^1_{33}$. The first uncertainty is statistical, the second systematic

This table contains thinned out samples of the Markov chains used in the parameter estimation of the SDME measurements for $-(t-t_\text{0}) = 0.197\pm0.069~\text{GeV}^2/c^2$, reported in the main article. One in about 250 steps in the chain, which results in 200 different sets of SDMEs, is provided. These values should be used instead of bootstrapping of the results, in order to estimate uncertainties of physics models fitted to this data. To assess how the uncertainties propagate to the model uncertainties, one should evaluate the model under scrutiny for each of the 200 different sets of SDMEs. Plotting all resulting lines in a single plot will create bands which reflect the influence of the uncertainties in the data on the model. This method has the great advantage that all correlations are accurately taken into account.


Photoproduction of {\boldmath{$\pi^{0}$}} Mesons off Protons and Neutrons in the Second and Third Nucleon Resonance Region

The A2 collaboration Dieterle, M. ; Werthmüller, D. ; Abt, S. ; et al.
Phys.Rev.C (2018) 065205-1-065205-28, 2018.
Inspire Record 1675023 DOI 10.17182/hepdata.131794

Photoproduction of mesons off quasi-free nucleons bound in the deuteron allows to study the electromagnetic excitation spectrum of the neutron and the isospin structure of the excitation of nucleon resonances. The database for such reactions is much more sparse than for free proton targets. Single $\pi^0$ photoproduction off quasi-free nucleons from the deuteron was experimentally studied. Nuclear effects were investigated by a comparison of the results for free protons and quasi-free protons and used as a correction for the quasi-free neutron data. The experiment was performed at the tagged photon beam of the Mainz MAMI accelerator for photon energies between 0.45~GeV and 1.4~GeV, using an almost $4\pi$ electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. A complete kinematic reconstruction of the final state removed the effects of Fermi motion. Reaction model predictions and PWA for $\gamma n\rightarrow n\pi^{0}$, based on fits to data for the other isospin channels, disagreed between themselves and no model provided a good description of the new data. The results demonstrate clearly the importance of a measurement of the fully neutral final state for the isospin decomposition of the cross section. Model refits, for example from the Bonn-Gatchina analysis, show that the new and the previous data for the other three isospin channels can be simultaneously described when the contributions of several partial waves are modified. The results are also relevant for the suppression of the higher resonance bumps in total photoabsorption on nuclei, which are not well understood.

19 data tables

Excitation function at cos(Theta_pi0)cm = -0.95

Excitation function at cos(Theta_pi0)cm = -0.85

Excitation function at cos(Theta_pi0)cm = -0.75


$K^+\Lambda$ and $K^+\Sigma^0$ photoproduction with fine center-of-mass energy resolution

The Crystal Ball at MAMI collaboration Jude, T.C. ; Glazier, D.I. ; Watts, D.P. ; et al.
Phys.Lett.B 735 (2014) 112-118, 2014.
Inspire Record 1250810 DOI 10.17182/hepdata.130796

Measurements of $\gamma p \rightarrow K^{+} \Lambda$ and $\gamma p \rightarrow K^{+} \Sigma^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. The new analyses disfavor a strong role for quark-diquark dynamics in the nucleon.

26 data tables

Excitation function at cos(Theta_K+)cm = -0.8

Excitation function at cos(Theta_K+)cm = -0.7

Excitation function at cos(Theta_K+)cm = -0.6


Precision Measurement of the Hadronic Contribution to the Muon Anomalous Magnetic Moment

Xiao, T. ; Dobbs, S. ; Tomaradze, A. ; et al.
Phys.Rev.D 97 (2018) 032012, 2018.
Inspire Record 1643020 DOI 10.17182/hepdata.130772

We report on a precision measurement of the cross section for the reaction $e^+e^-\to\pi^+\pi^-$ in the mass range $0.30<M_{\pi\pi}<1.00$ GeV with the initial state radiation (ISR) method, using 817 pb$^{-1}$ of data at $e^+e^-$ center-of-mass energies near 3.77 GeV and 586 pb$^{-1}$ of data at $e^+e^-$ center-of-mass energies near 4.17 GeV, collected with the CLEO-c detector at the CESR $e^+e^-$ collider at Cornell University. The integrated cross sections in the range $0.30<M_{\pi\pi}<1.00$ GeV for the process $e^+e^-\to\pi^+\pi^-$ are determined with a statistical uncertainty of $0.7\%$ and a systematic uncertainty of $1.5\%$. The leading-order hadronic contribution to the muon anomalous magnetic moment calculated using these measured $e^+e^-\to\pi^+\pi^-$ cross sections in the range $M_{\pi\pi}=0.30$ to 1.00 GeV is calculated to be $(500.4\pm3.6 (\mathrm{stat})\pm 7.5(\mathrm{syst}))\times10^{-10}$.

1 data table

Born cross section of $e^+e^-\rightarrow h^+h^-$

Electromagnetic Structure of the Proton, Pion, and Kaon by High-Precision Form Factor Measurements at Large Timelike Momentum Transfers

Seth, Kamal K. ; Dobbs, S. ; Metreveli, Z. ; et al.
Phys.Rev.Lett. 110 (2013) 022002, 2013.
Inspire Record 1189656 DOI 10.17182/hepdata.130771

High precision measurements of the form factors of proton, pion, and kaon for timelike momentum transfers of |Q^2|=s=14.2 and 17.4 GeV^2 have been made. Data taken with the CLEO-c detector at sqrt(s)=3.772 GeV and 4.170 GeV, with integrated luminosities of 805 pb^-1 and 586 pb^-1, respectively, have been used to study $e^+e^-$ annihilations into pi+pi-, K+K^-, and ppbar. The perturbative QCD prediction that at large Q^2 the quantity Q^2F(Q^2) for vector mesons is nearly constant, and varies only weakly as the strong coupling constant alpha_S(Q^2) is confirmed for both pions and kaons. In contrast, a significant difference is observed between the values of the corresponding pQCD suggested near-constant quantity, |Q^4|G_M(|Q^2|)/mu_p for protons at |Q^2|=14.2 GeV^2 and 17.4 GeV^2. The results suggest the constancy of |Q^2|G_M(|Q^2|)/mu_p, instead.

2 data tables

Born cross section of $e^+e^-\rightarrow h^+h^-$

Timelike form factor

Experimental study of the $\gamma p\rightarrow K^0\Sigma^+$, $\gamma n\rightarrow K^0\Lambda$, and $\gamma n\rightarrow K^0 \Sigma^0$ reactions at the Mainz Microtron

The A2 collaboration Akondi, C.S. ; Bantawa, K. ; Manley, D.M. ; et al.
Eur.Phys.J.A 55 (2019) 202, 2019.
Inspire Record 1703675 DOI 10.17182/hepdata.130236

This work measured $d\sigma/d\Omega$ for neutral kaon photoproduction reactions from threshold up to a c.m.\ energy of 1855MeV, focussing specifically on the $\gamma p\rightarrow K^0\Sigma^+$, $\gamma n\rightarrow K^0\Lambda$, and $\gamma n\rightarrow K^0 \Sigma^0$ reactions. Our results for $\gamma n\rightarrow K^0 \Sigma^0$ are the first-ever measurements for that reaction. These data will provide insight into the properties of $N^*$ resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the $\pi N$ channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.

28 data tables

Total cross section as a function of c.m. energy W.

Total cross section as a function of c.m. energy W.

Total cross section as a function of c.m. energy W.


Version 2
Investigation of the rho-meson resonance with electron-positron colliding beams

Auslander, V.L. ; Budker, G.I. ; Pakhtusova, E.V. ; et al.
Yad.Fiz. 9 (1969) 114-119, 1969.
Inspire Record 57008 DOI 10.17182/hepdata.18687


2 data tables

Measured value of the pion form factor

Fitted peak cross section.

Version 2
Pion Form-factor Measurement in the Reaction $e^+ e^- \to \pi^+ \pi^-$ for Energies Within the Range From 0.4-{GeV} to 0.46-{GeV}

Vasserman, I.B. ; Ivanov, P.M. ; Kezerashvili, G.Ya. ; et al.
Yad.Fiz. 33 (1981) 709-714, 1981.
Inspire Record 167191 DOI 10.17182/hepdata.18823


1 data table

Measured value of the total E+ E- --> PI+ PI- cross section

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


T and F asymmetries in $π^0$ photoproduction on the proton

The A2 & MAMI collaborations Annand, J.R.M. ; Arends, H.J. ; Beck, R. ; et al.
Phys.Rev.C 93 (2016) 055209, 2016.
Inspire Record 1466854 DOI 10.17182/hepdata.116551

The γp→π0p reaction was studied at laboratory photon energies from 425 to 1445 MeV with a transversely polarized target and a longitudinally polarized beam. The beam-target asymmetry F was measured for the first time and new high precision data for the target asymmetry T were obtained. The experiment was performed at the photon tagging facility of the Mainz Microtron (MAMI) using the Crystal Ball and TAPS photon spectrometers. The polarized cross sections were expanded in terms of associated Legendre functions and compared to recent predictions from several partial-wave analyses. The impact of the new data on our understanding of the underlying partial-wave amplitudes and baryon resonance contributions is discussed.

68 data tables

Target asymmetry T for c.m. energy W= 1.3062 GeV

Target asymmetry T for c.m. energy W= 1.3275 GeV

Target asymmetry T for c.m. energy W= 1.3486 GeV