Experimental Physics Division (EPD) at AANL (formerly the Yerevan Physics Institute, YerPhI) has a long-standing tradition of research across a diverse range of topics, dating back to the 1967 launch of the ARUS Yerevan electron synchrotron, which reached energies of up to 6 GeV.
Despite the extensive research programs conducted in the USA (Cambridge, Cornell, SLAC), Germany (DESY), and the UK (NINA) during that era, YerPhI physicists succeeded in obtaining several landmark results. These findings significantly advanced the global understanding of hadron and nuclear structures, as well as the fundamental properties of elementary particle interactions.
Between 1970 and 1991, the Yerevan synchrotron operated at high productivity, yielding significant scientific results in the energy range up to 4.5 GeV, including:
Measurements of proton and neutron electromagnetic radii.
Studies of the hadronic properties of photons in $pi$-meson photoproduction on nuclei.
Investigations into the structure of nucleon resonances through multi-polarization experiments.
Analyses of nuclear matter structure and characteristics.
Studies of X-ray transition radiation and the radiation of relativistic electrons during channeling in monocrystals.
In 1980, Academician H. Vartapetian (Deputy Director of YerPhI, 1974–1993) and his colleagues were awarded the State Prize of the Armenian Soviet Socialist Republic for their outstanding contributions and scientific achievements at the synchrotron.
Core Research Areas
The YerPhI experimental program focused on the following fields:
Properties and structures of baryons (nucleons and nucleon resonances).
Properties of few-nucleon systems.
Characteristics of excited nuclear systems.
Nuclear matter at short distances.
Electron interaction with crystals.
Methodological and detector studies.
Following the 1991 energy crisis in Armenia, the accelerator was halted, and since then, only short-term experiments have been performed periodically. However, the institute’s international reputation allowed it to maintain and expand collaborations with major scientific centers in the USA, Germany, and Switzerland, where EPD scientists continue to participate fully in global experimental research.
Summary of Scientific Results (1970–1991)
The main achievements of the EPD scientists during the peak operation of the Yerevan synchrotron include:
X-ray Transition Radiation: Systematic study of the phenomenon and properties of X-ray transition radiation (predicted theoretically at YerPhI). These results are now utilized worldwide for ultra-relativistic particle detection.
Electromagnetic Radii: Measurement of the proton and deuteron electromagnetic radii using 4.5 GeV electron elastic scattering, providing high-precision data that supplemented global databases.
Vector Dominance Model (VMD): Through measurements of single $pi$-meson photoproduction on nuclei, it was demonstrated that the simplest version of the VMD is insufficient to describe the hadronic properties of photons.
$eta$-Meson Structure: Determination of the total cross-section of $eta$-meson-nucleon interaction via incoherent $eta$-photoproduction on nuclei.
Polarized Photon Beams: Production of quasi-monochromatic photon beams (0.5–2.0 GeV) with record-level polarization. This established YerPhI’s leadership in researching spin correlations in photoproduction.
Nucleon Resonances: Investigation of nucleon resonance structures through multi-polarization experiments (beam, target, and recoil nucleon polarization), allowing for the determination of electromagnetic constants and testing of quark model predictions.
Nuclear Matter & Deuterons: Extensive studies of nucleon properties in nuclei via inclusive $(e,e')$ and exclusive $(e,e'p)$ scattering, as well as the study of deuteron and quasi-deuteron structures through photodisintegration.
Crystal Channeling & PXR: Observation of intense radiation from relativistic electrons in channeling regimes within monocrystals. Additionally, Parametric X-radiation (PXR) was obtained and studied, offering an extremely monochromatic ($deltaomega/omega approx 10^{-3}$) radiation source.
Detector Development: Innovation in scintillator, gaseous, and porous detectors for use in photo- and electro-production experiments.
Double Beta Decay: In collaboration with ITEP (Moscow), the first observation of two-neutrino double beta decay of $^{76}Ge$ was made in an underground laboratory. This work set the most stringent limits of that time on neutrinoless double beta decay, providing a crucial upper limit for the Majorana mass of the neutrino.
