BGO-OD is a new meson photoproduction experiment at the ELSA facility of Bonn University. It aims at the investigation of non strange and strange baryon excitations, and is especially designed to be able to detect weekly bound meson-baryon type structures. The setup for the BGO-OD experiment is presented, the characteristics of the photon beam and the detector performances are shown and the initial experimental program is discussed.

10.1051/epjconf/201613007013

Cite

Citations (0)

Sivers asymmetry extracted in SIDIS at the hard scales of the Drell–Yan process at COMPASS

Physics Letters B (2017)

C. Adolph M. Aghasyan R. Akhunzyanov M. Alexeev G. D. Alexeev

Proton transverse-spin azimuthal asymmetries are extracted from the COMPASS 2010 semi-inclusive hadron measurements in deep inelastic muon-nucleon scattering in those four regions of the photon virtuality $Q^2$, which correspond to the four regions of the di-muon mass $\sqrt{Q^2}$ used in the ongoing analysis of the COMPASS Drell-Yan measurements. This allows for a future direct comparison of the nucleon transverse-momentum-dependent parton distribution functions extracted from these two alternative measurements. Various two-dimensional kinematic dependences are presented for the azimuthal asymmetries induced by the Sivers transverse-momentum-dependent parton distribution function. The integrated Sivers asymmetries are found to be positive with an accuracy that appears to be sufficient to test the sign change of the Sivers function predicted by Quantum Chromodynamics.

Compass

Drell–Yan process

10.1016/j.physletb.2017.04.042

Cite

Citations (55)

Threshold [pi superscript 0] photoproduction on transverse polarised protons at MAMI

S. Schumann P. B. Otte C. S. Akondi J. R. M. Annand H. J. Arends

Source

Cite

Citations (0)

Helicity AmplitudesA1/2andA3/2

Physical Review Letters (2002)

J. Ahrens S. Altieri J. R. M. Annand G. Anton H. J. Arends

The helicity dependence of the γ→p→→pπ0 reaction has been measured for the first time in the photon-energy range from 550 to 790 MeV. The experiment, performed at the Mainz microtron MAMI, used a 4π-detector system, a circularly polarized, tagged photon beam, and a longitudinally polarized frozen-spin target. These data are predominantly sensitive to the D13(1520) resonance and are used to determine its helicity amplitudes.Received 4 March 2002DOI:https://doi.org/10.1103/PhysRevLett.88.232002©2002 American Physical Society

10.1103/physrevlett.88.232002

Cite

Citations (61)

The impact of new polarization data from Bonn, Mainz and Jefferson Laboratory on $\gamma p \rightarrow \pi N$ multipoles

The European Physical Journal A (2016)

A. V. Anisovich R. Beck M. Döring M. Gottschall J. Hartmann

Sigma

10.1140/epja/i2016-16284-9

Cite

Citations (49)

Exclusive charged pion photo-production in 12C

M. T. Laing D. Branford T. Davinson D. Johnston J.A. Mackenzie

Source

Cite

Citations (0)

Investigation of multiparticle final states in12C photoreactions

Physical Review C (1998)

P. D. Harty I. J. D. MacGregor J. Ahrens J. R. M. Annand I. Anthony

The ${}^{12}\mathrm{C}(\ensuremath{\gamma},pn)$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},pp)$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},ppp)$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},pp{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}})$, ${}^{12}\mathrm{C}(\ensuremath{\gamma},p{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}})$ reactions have been studied using tagged photons of energy ${E}_{\ensuremath{\gamma}}=250$--600 MeV. A model which includes all major absorption mechanisms and final state interactions gives results that agree well with the shapes of missing energy spectra, but for some channels the predicted cross sections are too large.

10.1103/physrevc.57.123

Cite

Citations (12)

High-statistics measurement of Collins and Sivers asymmetries for transversely polarised deuterons

arXiv (Cornell University) (2024)

G. D. Alexeev M. Alexeev C. Alice A. Amoroso V. Andrieux

New results are presented on a high-statistics measurement of Collins and Sivers asymmetries of charged hadrons produced in deep inelastic scattering of muons on a transversely polarised $^6$LiD target. The data were taken in 2022 with the COMPASS spectrometer using the 160 \gevv\ muon beam at CERN, balancing the existing data on transversely polarised proton targets. The first results from about two-thirds of the new data have total uncertainties smaller by up to a factor of three compared to the previous deuteron measurements. Using all the COMPASS proton and deuteron results, both the transversity and the Sivers distribution functions of the $u$ and $d$ quark, as well as the tensor charge in the measured $x$-range are extracted. In particular, the accuracy of the $d$ quark results is significantly improved.

Compass

10.48550/arxiv.2401.00309

Cite

Citations (0)

Photoemission of protons from 4He in the ⊿-resonance region

Zeitschrift für Physik A Hadrons and Nuclei (1996)

R. Wichmann J. Ahrens H. J. Arends R. Beck G. Galler

Photodisintegration

Photon energy

10.1007/s002180050095

Cite

Citations (0)

Photoproduction ofη-MesicHe3

Physical Review Letters (2004)

Masahiro Yoshita J. Ahrens J. R. M. Annand R. Beck G. Caselotti

The photoproduction of η-mesic 3He has been investigated using the TAPS calorimeter at the Mainz Microtron accelerator facility MAMI. The total inclusive cross section for the reaction γ3He→ηX has been measured for photon energies from threshold to 820 MeV. The total and angular differential coherent η cross sections have been extracted up to energies of 745 MeV. A resonancelike structure just above the η production threshold with an isotropic angular distribution suggests the existence of a resonant quasibound state. This is supported by studies of a competing decay channel of such a quasibound η-mesic nucleus into π0pX. A binding energy of (−4.4±4.2) MeV and a width of (25.6±6.1) MeV is deduced for the quasibound η-mesic state in 3He.Received 11 December 2003DOI:https://doi.org/10.1103/PhysRevLett.92.252001©2004 American Physical Society

10.1103/physrevlett.92.252001

Cite

Citations (149)