The
GlueX
collaboration
Adhikari, S.
;
Akondi, C.S.
;
Albrecht, M.
;
*et al. *

Phys.Rev.C 105 (2022) 035201, 2022.

https://inspirehep.net/literature/1892395
Inspire Record
1892395
DOI
10.17182/hepdata.132920
https://doi.org/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

The
A2
collaboration
Dieterle, M.
;
Werthmüller, D.
;
Abt, S.
;
*et al. *

Phys.Rev.C (2018) 065205-1-065205-28, 2018.

https://inspirehep.net/literature/1675023
Inspire Record
1675023
DOI
10.17182/hepdata.131794
https://doi.org/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

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.

https://inspirehep.net/literature/1250810
Inspire Record
1250810
DOI
10.17182/hepdata.130796
https://doi.org/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

The
A2
collaboration
Akondi, C.S.
;
Bantawa, K.
;
Manley, D.M.
;
*et al. *

Eur.Phys.J.A 55 (2019) 202, 2019.

https://inspirehep.net/literature/1703675
Inspire Record
1703675
DOI
10.17182/hepdata.130236
https://doi.org/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.

The
MAINZ-A2
collaboration
Schumann, S.
;
Otte, P.B.
;
Akondi, C.S.
;
*et al. *

Phys.Lett.B 750 (2015) 252-258, 2015.

https://inspirehep.net/literature/1394326
Inspire Record
1394326
DOI
10.17182/hepdata.126972
https://doi.org/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

The
A2
&
MAMI
collaborations
Annand, J.R.M.
;
Arends, H.J.
;
Beck, R.
;
*et al. *

Phys.Rev.C 93 (2016) 055209, 2016.

https://inspirehep.net/literature/1466854
Inspire Record
1466854
DOI
10.17182/hepdata.116551
https://doi.org/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

The
CBELSA/TAPS
collaboration
Metag, V.
;
Nanova, M.
;
Hartmann, J.
;
*et al. *

Eur.Phys.J.A 57 (2021) 325, 2021.

https://inspirehep.net/literature/1987678
Inspire Record
1987678
DOI
10.17182/hepdata.115572
https://doi.org/10.17182/hepdata.115572
The reaction $\gamma p \rightarrow p \pi^0 \eta$ has been studied with the CBELSA/TAPS detector at the electron stretcher accelerator ELSA in Bonn for incident photon energies from threshold up to 3.1 GeV. This paper has been motivated by the recently claimed observation of a narrow structure in the M$_{N\eta}$ invariant mass distribution at a mass of 1678 MeV/$c^2$. The existence of this structure cannot be confirmed in the present work. Instead, for E$_{\gamma}$ = 1400 - 1500 MeV and the cut M$_{p\pi^0} \le 1190 $ MeV/$c^2$ a statistically significant structure in the M$_{p\eta}$ invariant mass distribution near 1700 MeV/$c^2$ is observed with a width of $\Gamma\approx 35$ MeV/$c^2$ while the mass resolution is $\sigma_{res}$ = 5 MeV/$c^2$. Increasing the incident photon energy from 1420 to 1540 MeV this structure shifts in mass from $\approx$ 1700MeV/c$^2$ to $\approx$ 1725 MeV/$c^2$; the width increases to about 50 MeV/$c^2$ and decreases thereafter. The cross section associated with this structure reaches a maximum of $\approx$ 100 nb around E$_{\gamma} \approx$ 1490 MeV (W $\approx $ 1920 MeV), which coincides with the $p a_0$ threshold. Three scenarios are discussed which might be the origin of this structure in the M$_{p\eta}$ invariant mass distribution. The most likely interpretation is that it is due to a triangular singularity in the $\gamma p \rightarrow p a_0 \rightarrow p \pi^0 \eta$ reaction

32
data tables

The
H1
collaboration
Aktas, A.
;
Andreev, V.
;
Anthonis, T.
;
*et al. *

Eur.Phys.J.C 41 (2005) 453-467, 2005.

https://inspirehep.net/literature/676166
Inspire Record
676166
DOI
10.17182/hepdata.110966
https://doi.org/10.17182/hepdata.110966
A measurement of the beauty production cross section in ep collisions at a centre-of-mass energy of 319 GeV is presented. The data were collected with the H1 detector at the HERA collider in the years 1999-2000. Events are selected by requiring the presence of jets and muons in the final state. Both the long lifetime and the large mass of b-flavoured hadrons are exploited to identify events containing beauty quarks. Differential cross sections are measured in photoproduction, with photon virtualities Q^2 < 1 GeV^2, and in deep inelastic scattering, where 2 < Q^2 < 100 GeV^2. The results are compared with perturbative QCD calculations to leading and next-to-leading order. The predictions are found to be somewhat lower than the data.

10
data tables

Muons and jets from beauty photoproduction, pseudorapidity.

Muons and jets from beauty photoproduction, muon transverse momentum.

Muons and jets from beauty photoproduction, leading jet transverse momentum

The
GlueX
collaboration
Adhikari, S.
;
Ali, A.
;
Amaryan, M.
;
*et al. *

Phys.Rev.C 100 (2019) 052201, 2019.

https://inspirehep.net/literature/1749712
Inspire Record
1749712
DOI
10.17182/hepdata.110166
https://doi.org/10.17182/hepdata.110166
We report on the measurement of the beam asymmetry $\Sigma$ for the reactions $\vec{\gamma}p\rightarrow p\eta$ and $\vec{\gamma}p \rightarrow p\eta^{\prime}$ from the GlueX experiment, using an 8.2--8.8 GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Lab. These measurements are made as a function of momentum transfer $-t$, with significantly higher statistical precision than our earlier $\eta$ measurements, and are the first measurements of $\eta^{\prime}$ in this energy range. We compare the results to theoretical predictions based on $t$--channel quasi-particle exchange. We also compare the ratio of $\Sigma_{\eta}$ to $\Sigma_{\eta^{\prime}}$ to these models, as this ratio is predicted to be sensitive to the amount of $s\bar{s}$ exchange in the production. We find that photoproduction of both $\eta$ and $\eta^{\prime}$ is dominated by natural parity exchange with little dependence on $-t$.

3
data tables

The
ATLAS
collaboration
Aaboud, Morad
;
Aad, Georges
;
Abbott, Brad
;
*et al. *

Phys.Lett.B 776 (2018) 295-317, 2018.

https://inspirehep.net/literature/1632756
Inspire Record
1632756
DOI
10.17182/hepdata.79163
https://doi.org/10.17182/hepdata.79163
This Letter presents the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet. These final states provide sensitivity to the heavy-flavour content of the proton and aspects related to the modelling of heavy-flavour quarks in perturbative QCD. The measurement uses proton-proton collision data at a centre-of-mass energy of 8 TeV recorded by the ATLAS detector at the LHC in 2012 corresponding to an integrated luminosity of up to 20.2 fb$^{-1}$. The differential cross sections are measured for each jet flavour with respect to the transverse energy of the leading photon in two photon pseudorapidity regions: $|\eta^\gamma|<1.37$ and $1.56<|\eta^\gamma|<2.37$. The measurement covers photon transverse energies $25 < E_\textrm{T}^\gamma<400$ GeV and $25 < E_\textrm{T}^\gamma<350$ GeV respectively for the two $|\eta^\gamma|$ regions. For each jet flavour, the ratio of the cross sections in the two $|\eta^\gamma|$ regions is also measured. The measurement is corrected for detector effects and compared to leading-order and next-to-leading-order perturbative QCD calculations, based on various treatments and assumptions about the heavy-flavour content of the proton. Overall, the predictions agree well with the measurement, but some deviations are observed at high photon transverse energies. The total uncertainty in the measurement ranges between 13% and 66%, while the central $\gamma+b$ measurement exhibits the smallest uncertainty, ranging from 13% to 27%, which is comparable to the precision of the theoretical predictions.

12
data tables