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 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.

PSEUDOSCALAR MESON PRODUCTION USING THE CRYSTAL BALL

2005 ◽  
Vol 20 (08n09) ◽  
pp. 1674-1679
Author(s):  
W. J. BRISCOE
Keyword(s):  
Radiative Capture ◽  
National Laboratory ◽  
Meson Production ◽  
Brookhaven National Laboratory ◽  
Experimental Program ◽  
Final States ◽  
Production Mechanism ◽  
Fundamental Interaction ◽  
Crystal Ball ◽  
Series Of Experiments

The Crystal Ball Spectrometer was used at Brookhaven National Laboratory in a series of experiments which study all neutral final states of π- p and K- p induced reactions. We report about the experimental program and new results for the radiative capture reactions π-p → γ n and K-p → γΛ, charge exchange π-p → π° n , two π° production π-p → π° π° n , and η production π-p → η n reactions. Data have also been obtained on the decays of N*, Δ, Λ, and Σ resonances. Threshold η production has been studied in detail for both π- p and K- p . Sequential resonance decays have been investigated by studying the 2π° production mechanism both in the fundamental interaction and in nuclei.

PHOTOPRODUCTION OF MESONS OFF LIGHT NUCLEI

2011 ◽  
Vol 26 (03n04) ◽  
pp. 461-467
Author(s):  
BERND KRUSCHE
Keyword(s):  
Spin Structure ◽  
Light Nuclei ◽  
Photon Beams ◽  
Meson Photoproduction ◽  
Crystal Ball ◽  
Electromagnetic Resonance ◽  
Reaction Channels ◽  
Light Target ◽  
Mesic Nuclei

During the last few years photoproduction of mesons off light target nuclei (2 H , 3 He , 7 Li ) has been systematically studied at the tagged photon beams of the Bonn ELSA accelerator and the Mainz MAMI accelerator. The experiments used the combined Crystal Barrel/TAPS setup in Bonn and the Crystal Ball/TAPS setup in Mainz. Most measurements investigated meson photoproduction off the neutron for many different reaction channels in order to establish the iso-spin structure of electromagnetic resonance couplings. This project used mostly deuteron targets. The measurements with the He and Li targets aimed at the search for η-mesic nuclei and hadron in-medium properties.

scholarly journals On the quenching of Gamow–Teller strength

1987 ◽  
Vol 65 (6) ◽  
pp. 574-577 ◽  
Author(s):  
J. Rapaport
Keyword(s):  
Cross Sections ◽  
Wave Functions ◽  
Light Nuclei ◽  
Final States ◽  
Excitation Energies ◽  
Intermediate Energies ◽  
Quenching Factor ◽  
Configuration Mixing ◽  
Gamow Teller ◽  
Model Strength

The (p, n) reaction at intermediate energies has been used to measure differential cross sections in light nuclei to final states characterized with a ΔJπ = 1+ transfer (Gamow–Teller (GT) states). Experimental ft values for allowed beta-decay transitions in these nuclei are used to normalize the strength of the GT transitions in units of B(GT). This experimental GT strength is compared with predicted shell–model strength. For p-shell nuclei, the calculated excitation energies of the GT strength using Cohen and Kurath wave functions are in general agreement with the empirical GT distribution. Up to an excitation energy of about 20 MeV, the total experimental and calculated GT strengths are used to obtain the quenching factor, QF = Σ B(GT)exp/Σ B(GT)theor. It is found that QF decreases as the shell gets filled-up. The lowest value seems to occur for single-hole nuclei. This decrease may be explained by configuration mixing not specifically included in the calculations.

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

RECENT RESULTS FROM THE REAL PHOTON EXPERIMENT AT MAMI

2010 ◽  
Vol 19 (05n06) ◽  
pp. 1064-1075
Author(s):  
ANDREAS THOMAS
Keyword(s):  
High Intensity ◽  
Photon Beam ◽  
Real Photon ◽  
Final States ◽  
Detection Capability ◽  
Crystal Ball ◽  
The Real ◽  
The Future ◽  
Set Up

Experiments with real photons have been performed for many years at the Mainz accelerator MAMI with different detectors. The upgraded MAMI C accelerator recently delivered electrons with an energy of 1604MeV. The A2 collaboration performs experiments with energy tagged polarised real photons produced via 'Bremsstrahlung'. Linear and circular photon polarisation is possible. In the years 2005/2006 the Crystal Ball detector with its unique detection capability for multi photon final states was set up in Mainz. The Crystal Ball at MAMI setup offers an excellent possibility to study decays of the η and η′ mesons. Due to the high intensity photon beam the apparatus can be seen as an η-factory. Recent results from the Crystal Ball experiment at MAMI are presented. In the future we plan to use a longitudinal and transverse polarised frozen spin target to investigate the spin polarisibilities of the nucleons.

scholarly journals THE BGO-OD EXPERIMENT AT ELSA

2014 ◽  
Vol 26 ◽  
pp. 1460093 ◽  
Author(s):  
◽  
B. BANTES ◽  
D. BAYADILOV ◽  
R. BECK ◽  
M. BECKER ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Excitation Spectrum ◽  
Final States ◽  
Vector Mesons ◽  
Meson Photoproduction ◽  
Neutral Particles ◽  
Pseudoscalar Mesons ◽  
Initial Program ◽  
The University

Meson photoproduction is a key tool for the experimental investigation of the nucleon excitation spectrum. To disentangle the specific couplings of resonances, in addition to the rather well measured pion and eta photoproduction channels it is mandatory to obtain information on channels involving strange and vector mesons and higher mass pseudoscalar mesons, and the associated multi-particle final states with both charged and neutral particles. In this respect, the new BGO-OD experiment at the ELSA accelerator of the University of Bonn's Physikalisches Institut provides unique instrumentation. We describe the experiment, present its status and the initial program of measurements.

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