131 research outputs found
Photoproduction of pi0 omega off protons for E(gamma) < 3 GeV
Differential and total cross-sections for photoproduction of gamma proton to
proton pi0 omega and gamma proton to Delta+ omega were determined from
measurements of the CB-ELSA experiment, performed at the electron accelerator
ELSA in Bonn. The measurements covered the photon energy range from the
production threshold up to 3GeV.Comment: 8 pages, 13 figure
Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR
The possibility of measuring the proton electromagnetic form factors in the
time-like region at FAIR with the \PANDA detector is discussed. Detailed
simulations on signal efficiency for the annihilation of into a
lepton pair as well as for the most important background channels have been
performed. It is shown that precision measurements of the differential cross
section of the reaction can be obtained in a wide
angular and kinematical range. The individual determination of the moduli of
the electric and magnetic proton form factors will be possible up to a value of
momentum transfer squared of (GeV/c). The total cross section will be measured up to (GeV/c).
The results obtained from simulated events are compared to the existing data.
Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations,
4 tables, 9 figure
Study of the reaction
The reaction has been studied with the CBELSA
detector at the tagged photon beam of the Bonn electron stretcher facility. The
reaction shows contributions from , and
as intermediate states. A partial wave analysis suggests that the
reaction proceeds via formation of six resonances,
, , ,
, , , and two
nucleon resonances and , for which pole
positions and decay branching ratios are given.Comment: 13 pages, 10 figures, 7 table
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
Simulation results for future measurements of electromagnetic proton form
factors at \PANDA (FAIR) within the PandaRoot software framework are reported.
The statistical precision with which the proton form factors can be determined
is estimated. The signal channel is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , is studied.
Furthermore, the background versus signal efficiency, statistical and
systematical uncertainties on the extracted proton form factors are evaluated
using two different procedures. The results are consistent with those of a
previous simulation study using an older, simplified framework. However, a
slightly better precision is achieved in the PandaRoot study in a large range
of momentum transfer, assuming the nominal beam conditions and detector
performance
N* and Delta* decays into N pi0 pi0
Decays of baryon resonances in the second and the third resonance region into
N pi0 pi0 are studied by photoproduction of two neutral pions off protons.
Partial decay widths of N* and Delta* resonances decaying into Delta(1232) pi,
N(\pi\pi)_{S}, N(1440)P_{11} pi, and N(1520)D_{13} pi are determined in a
partial wave analysis of this data, and data from other reactions. Several
partial decay widths were not known before. Interesting decay patterns are
observed which are not even qualitatively reproduced by quark model
calculations. In the second resonance region, decays into Delta(1232) pi
dominate clearly. The N(\pi\pi)_{S}-wave provides a significant contribution to
the cross section, especially in the third resonance region. The P_{13}(1720)
properties found here are at clear variance to PDG values.Comment: 13 pages, 4 figures, long author's lis
Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR
This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented
Technical Design Report for the: PANDA Micro Vertex Detector
This document illustrates the technical layout and the expected performance
of the Micro Vertex Detector (MVD) of the PANDA experiment. The MVD will detect
charged particles as close as possible to the interaction zone. Design criteria
and the optimisation process as well as the technical solutions chosen are
discussed and the results of this process are subjected to extensive Monte
Carlo physics studies. The route towards realisation of the detector is
outlined.Comment: 189 pages, 225 figures, 41 table
Study of doubly strange systems using stored antiprotons
Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the P‾ANDA experiment at FAIR. For the first time, high resolution γ-spectroscopy of doubly strange ΛΛ-hypernuclei will be performed, thus complementing measurements of ground state decays of ΛΛ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Ξ−-atoms will be feasible and even the production of Ω−-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ω−-nucleus interaction. For the first time it will be possible to study the behavior of Ξ‾+ in nuclear systems under well controlled conditions
Measurement of the cross section for and observation of an excited baryon
Using a total of 11.0 fb of collision data with
center-of-mass energies between 4.009 GeV and 4.6 GeV and collected with the
BESIII detector at BEPCII, we measure fifteen exclusive cross sections and
effective form factors for the process
by means of a single baryon-tag
method. After performing a fit to the dressed cross section of
, no significant or
resonance is observed in the final states,
and upper limits at the 90\% confidence level on for
the processes / are
determined. In addition, an excited baryon at 1820 MeV/ is
observed with a statistical significance of 6.2 6.5 by including
the systematic uncertainty, and the mass and width are measured to be ~MeV/ and ~MeV, which confirms the existence of the state
.Comment: 8 pages, 4 figures, 1 Supplemental Material with 2 pages, consistent
with paper published in Phys. Rev. Lett. 124, 032002 (2020
PANDA Phase One - PANDA collaboration
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future antiProton ANnihilations at DArmstadt (PANDA or P¯ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton–nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the Phase One setup. The physics programme that is achievable during Phase One is outlined in this paper
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