scholarly journals QUASI-FREE PHOTOPRODUCTION OF η-MESONS OFF 2H AND 3He

2014 ◽  
Vol 26 ◽  
pp. 1460114
Author(s):  
IRAKLI KESHELASHVILI ◽  
DOMINIK WERTHMÜLLER ◽  
LILIAN WITTHAUER
Keyword(s):  
Excitation Function ◽  
Electron Accelerator ◽  
Electromagnetic Calorimeter ◽  
Crystal Ball ◽  
Fermi Motion ◽  
Incident Photon ◽  
Preliminary Results ◽  
Narrow Structure

In this work, we are presenting a combination of two preliminary results for quasi-free photoproduction of η-mesons from the liquid deuterium and 3 He targets for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI electron accelerator, using the Glasgow tagged photon facility. Decay photons of the η-mesons and the recoil nucleons were detected with an almost 4π covering electromagnetic calorimeter combining the Crystal Ball and TAPS detectors. The data from both targets show a narrow structure in the excitation function of γ + n → n + η. The results from the two measurements are consistent within the expected effects from nuclear Fermi motion.

PHOTOPRODUCTION OF MESONS OFF LIGHT NUCLEI

2010 ◽  
Vol 19 (05n06) ◽  
pp. 915-926 ◽  
Author(s):  
B. KRUSCHE
Keyword(s):  
Excitation Function ◽  
Light Nuclei ◽  
Final States ◽  
Meson Photoproduction ◽  
Crystal Ball ◽  
Series Of Experiments ◽  
Nuclear Targets ◽  
Narrow Structure ◽  
Surprising Finding

In a series of experiments at the tagged photon facilities of the Bonn ELSA accelerator and the Mainz MAMI accelerator photoproduction of mesons from light nuclear targets (deuteron, 3 He ) has been studied. The experiments used the combined Crystal Barrel/TAPS setup in Bonn and the Crystal Ball/TAPS setup in Mainz. Meson photoproduction off the neutron has been investigated for the πo, πoπo, πoπ-, η, η′, and ηπo final states. A surprising finding was a narrow structure in the γn → nη excitation function, which is not seen in the proton case. Measurements of η- and πo-photoproduction off a liquid 3 He -target have provided further evidence for the formation of η-mesic 3 He .

scholarly journals Narrow Structure in the Excitation Function ofηPhotoproduction off the Neutron

2013 ◽  
Vol 111 (23) ◽  
Author(s):  
D. Werthmüller ◽  
L. Witthauer ◽  
I. Keshelashvili ◽  
P. Aguar-Bartolomé ◽  
J. Ahrens ◽  
...  
Keyword(s):  
Excitation Function ◽  
Narrow Structure

N* PHYSICS AT MAMI — RESULTS AND PERSPECTIVES

2014 ◽  
Vol 26 ◽  
pp. 1460051
Author(s):  
MICHAEL OSTRICK
Keyword(s):  
Partial Wave ◽  
Scalar Meson ◽  
Crystal Ball ◽  
Preliminary Results ◽  
Model Independent ◽  
Pseudo Scalar ◽  
Photo Production

New measurements of transverse target and beam-target asymmetries in pion photo-production were performed using the Crystal Ball at the Mainz Microtron MAMI. Preliminary results are discussed in the context of model-independent partial wave analyses for pseudo-scalar meson photo-production below Ecm = 2 GeV.

scholarly journals Measurement of π0π+/− photoproduction off the deuteron and dbutanol targets

2019 ◽  
Vol 199 ◽  
pp. 02010
Author(s):  
Debdeep Ghosal
Keyword(s):  
Excitation Spectrum ◽  
Cross Section ◽  
Crucial Role ◽  
Electromagnetic Coupling ◽  
Polarization Observable ◽  
Cross Section Data ◽  
Meson Photoproduction ◽  
Crystal Ball ◽  
Preliminary Results ◽  
Section Data

Recent experiments using the Crystal Ball/TAPS setup at the MAMI accelerator in Mainz, Germany continue to study the properties and the excitation spectrum of the nucleon with meson photoproduction. Electromagnetic excitations of the proton and neutron are essential for understanding their isospin decomposition. The electromagnetic coupling of photons to protons is different than that of neutrons in certain states. Cross-section data alone is not sufficient for separating resonances, whereas polarization observables play a crucial role being essential in disentangling the contributing resonant and non-resonant amplitudes. Preliminary results of the polarization observable E of double π production off an unpolarized (LD2) and polarized (dButanol) target are shown with comparison to predictions of recent analyses.

scholarly journals Measurement of π0π+/- photoproduction off the deuteron and dbutanol targets

2020 ◽  
Vol 241 ◽  
pp. 01006
Author(s):  
Debdeep Ghosal
Keyword(s):  
Excitation Spectrum ◽  
Cross Section ◽  
Crucial Role ◽  
Electromagnetic Coupling ◽  
Polarization Observable ◽  
Cross Section Data ◽  
Meson Photoproduction ◽  
Crystal Ball ◽  
Preliminary Results ◽  
Section Data

Recent experiments using the Crystal Ball/TAPS setup at the MAMI accelerator in Mainz, Germany continue to study the properties and the excitation spectrum of the nucleon with meson photoproduction. Elec tromagnetic excitations of the proton and neutron are essential for understanding their isospin decomposition. The electromagnetic coupling of photons to protons is different than that of neutrons in certain states. Cross section data alone is not sufficient for separating resonances, whereas polarization observables play a crucial role being essential in disentangling the contributing resonant and non-resonant amplitudes. Preliminary results of the polarization observable E of double π production measured with a polarized solid deuterated Butanol target are shown with comparison to predictions of recent analyses.

scholarly journals QUASIFREE PHOTOPRODUCTION OF PION-PAIRS OF PROTONS AND NEUTRONS

2014 ◽  
Vol 26 ◽  
pp. 1460106
Author(s):  
◽  
M. OBERLE ◽  
B. KRUSCHE
Keyword(s):  
Cross Sections ◽  
Resonance Region ◽  
Electromagnetic Calorimeter ◽  
Final State ◽  
Model Calculations ◽  
Incident Photon ◽  
Free Neutron ◽  
Protons And Neutrons ◽  
Charged Pions ◽  
Comparison Of The Results

Beam-helicity asymmetries and mass-differential cross sections have been measured at the MAMI accelerator in Mainz for the photoproduction of neutral and mixed-charge pion pairs in the reactions γp → nπ0π+ and γp → pπ0π0 off free protons and γd → (p)pπ0π-, γd → (n)pπ0π0 and γd → (n)nπ0π+, γd → (p)nπ0π0 off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced in bremsstrahlung processes of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The decay products (photons, protons neutrons and charged pions) were detected in the 4π electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a full kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, indicate that the quasi-free neutron results are also a close approximation of the free-neutron results. Comparison of the results to predictions of model calculations portend that especially the reaction mechanisms in the production of the mixed-charge final states are still not well understood, in particular at low incident photon energies in the second nucleon resonance region.

INCLUSIVE PHOTON v2 AND THE APPROACH TO DIRECT PHOTON v2 IN $\sqrt{^SNN} = 200\ {\rm GEV}$AU+AU COLLISIONS

2007 ◽  
Vol 16 (07n08) ◽  
pp. 1839-1844
Author(s):  
◽  
GUOJI LIN
Keyword(s):  
Direct Photon ◽  
Electromagnetic Calorimeter ◽  
Event Plane ◽  
Preliminary Results ◽  
Decay Products ◽  
Flow Effects

We present the STAR preliminary results of inclusive photon v2 as a function of pT in [Formula: see text] AU + AU collisions. Photons are identified in the STAR Barrel Electromagnetic Calorimeter (BEMC). Non-flow effects are suppressed by obtaining the event plane in different pseudo-rapidity regions. The v2 of π0 decay products is calculated from the known v2 and spectra of hadrons and is compared to the inclusive photon v2. The comparison indicates that direct photon v2 is small.

The O–C diagrams of minor planets − a new approach to modelling the rotation

1999 ◽  
Vol 173 ◽  
pp. 185-188
Author(s):  
Gy. Szabó ◽  
K. Sárneczky ◽  
L.L. Kiss
Keyword(s):  
Error Analysis ◽  
Time Dependence ◽  
Theoretical Work ◽  
Minor Planet ◽  
Minor Planets ◽  
New Approach ◽  
Preliminary Results ◽  
Ccd Observations

AbstractA widely used tool in studying quasi-monoperiodic processes is the O–C diagram. This paper deals with the application of this diagram in minor planet studies. The main difference between our approach and the classical O–C diagram is that we transform the epoch (=time) dependence into the geocentric longitude domain. We outline a rotation modelling using this modified O–C and illustrate the abilities with detailed error analysis. The primary assumption, that the monotonity and the shape of this diagram is (almost) independent of the geometry of the asteroids is discussed and tested. The monotonity enables an unambiguous distinction between the prograde and retrograde rotation, thus the four-fold (or in some cases the two-fold) ambiguities can be avoided. This turned out to be the main advantage of the O–C examination. As an extension to the theoretical work, we present some preliminary results on 1727 Mette based on new CCD observations.

Cyclic Evolution of Sunspots: Gleaning New Results from Old Data

2000 ◽  
Vol 179 ◽  
pp. 163-165
Author(s):  
S. K. Solanki ◽  
M. Fligge ◽  
P. Pulkkinen ◽  
P. Hoyng
Keyword(s):  
Sunspot Number ◽  
Sunspot Cycle ◽  
Preliminary Results ◽  
Butterfly Diagram

AbstractThe records of sunspot number, sunspot areas and sunspot locations gathered over the centuries by various observatories are reanalysed with the aim of finding as yet undiscovered connections between the different parameters of the sunspot cycle and the butterfly diagram. Preliminary results of such interrelationships are presented.

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