Related Experiment Video
Updated: Jul 2, 2026
07:46
Setting Limits on Supersymmetry Using Simplified Models
Published on: November 15, 2013
eta-->gammagamma decay width via the Primakoff cross section
T E Rodrigues1, J D T Arruda-Neto, J Mesa
1Physics Institute, University of São Paulo, P. O. Box 66318, CEP 05315-970, São Paulo, Brazil.
Physical Review Letters
|September 4, 2008
Summary
This study analyzes eta photoproduction in nuclei, finding a destructive interference in copper and a new decay width for eta mesons. The results challenge previous measurements, offering a more accurate understanding of nuclear interactions.
Area of Science:
- Nuclear Physics
- Particle Physics
- High-Energy Physics
Background:
- Previous studies on eta photoproduction in nuclei lacked detailed final-state interaction analysis.
- Discrepancies existed in measured decay widths of eta mesons, necessitating further investigation.
Purpose of the Study:
- To evaluate incoherent eta photoproduction in nuclei at forward angles using a Monte Carlo cascade model.
- To analyze the interference between Coulomb and nuclear coherent amplitudes.
- To accurately determine the eta meson's decay width into two photons (Gamma(eta-->gammagamma)).
Main Methods:
- Utilized a multiple scattering Monte Carlo cascade calculation.
- Incorporated full eta-nucleus final-state interactions.
- Analyzed Primakoff, nuclear coherent, and nuclear incoherent cross sections for Beryllium (Be) and Copper (Cu).
Main Results:
- The model successfully fitted previous measurements for Be and Cu, indicating destructive interference for Cu.
- The nuclear incoherent component was identified as the inelastic background, not isotropic as previously assumed.
- Derived Gamma(eta-->gammagamma)=0.476(62) keV from Primakoff cross sections, consistent with the Particle Data Group average.
Conclusions:
- The study provides a more accurate determination of the eta meson's decay width, differing significantly from prior Cornell measurements.
- The findings highlight the importance of final-state interactions and interference effects in nuclear photoproduction.
- This work refines our understanding of eta meson properties and nuclear dynamics in high-energy interactions.
Related Concept Videos
03:23Types of Radioactivity
The most common types of radioactivity are α decay, β decay, γ decay, neutron emission, and electron capture.
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
Alpha (α) decay is the emission of an α particle from the nucleus. For example, polonium-210 undergoes α decay:
03:18Radioactivity and Nuclear Equations
Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for hydrogen, neutrons. The number of protons in the nucleus is called the atomic number (Z) of the element, and the sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are isotopes of the same element.
A nuclide of an element has a specific number of protons and...
A nuclide of an element has a specific number of protons and...
02:48Radioactive Decay and Radiometric Dating
Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. The number of disintegrations per unit time is called the activity (A), which is directly proportional to the number of nuclei in the sample. The decay constant (λ) is an average probability of decay per nucleus in unit time.
03:18Nuclear Stability
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together in the...
To hold positively charged protons together in the...
03:20Nuclear Transmutation
Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with another particle. The first manmade nucleus was produced in Ernest Rutherford’s laboratory in 1919 by a transmutation reaction, the bombardment of one type of nuclei with other nuclei or with neutrons. Rutherford bombarded nitrogen-14 atoms with high-speed α particles from a natural radioactive isotope of radium and observed protons being...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.