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A. Simonyan

Publications and source records attributed to A. Simonyan.

4 recordsLinked to original sources

E-Beam Induced Micropattern Generation and Amorphization of L-Cysteine-Functionalized Graphene Oxide Nano-composites

The evolution of dynamic processes in graphene-family materials are of great interest for both scientific purposes and technical applications. Scanning electron microscopy and transmission electron microscopy outstand among the techniques that allow both observing and controlling such dynamic processes in real time. On the other hand, functionalized graphene oxide emerges as a favorable candidate from graphene-family materials for such an investigation due to its distinctive properties, that encompass a large surface area, robust thermal stability, and noteworthy electrical and mechanical properties after its reduction. Here, we report on studies of surface structure and adsorption dynamics of L-Cysteine on electrochemically exfoliated graphene oxides basal plane. We show that electron beam irradiation prompts an amorphization of functionalized graphene oxide along with the formation of micropatterns of controlled geometry composed of L-Cysteine-Graphene oxide nanostructures. The controlled growth and predetermined arrangement of micropatterns as well as controlled structure disorder induced by e beam amorphization, in its turn potentially offering tailored properties and functionalities paving the way for potential applications in nanotechnology, sensor development, and surface engineering. Our findings demonstrate that graphene oxide can cover L-Cysteine in such a way to provide a control on the positioning of emerging microstructures about 10-20 um in diameter. Besides, Raman and SAED measurement analyses yield above 50% amorphization in a material. The results of our studies demonstrate that such a technique enables the direct creation of micropatterns of L-Cysteine-Graphene oxide eliminating the need for complicated mask patterning procedures.

cond-mat.mtrl-sci

Searching for Prompt and Long-Lived Dark Photons in Electro-Produced $e^+e^-$ Pairs with the Heavy Photon Search Experiment at JLab

The Heavy Photon Search experiment (HPS) at the Thomas Jefferson National Accelerator Facility searches for electro-produced dark photons. We report results from the 2016 Engineering Run consisting of 10608/nb of data for both the prompt and displaced vertex searches. A search for a prompt resonance in the $e^+e^-$ invariant mass distribution between 39 and 179 MeV showed no evidence of dark photons above the large QED background, limiting the coupling of {\epsilon}^2 {\geq} 10^-5, in agreement with previous searches. The search for displaced vertices showed no evidence of excess signal over background in the masses between 60 and 150 MeV, but had insufficient luminosity to limit canonical heavy photon production. This is the first displaced vertex search result published by HPS. HPS has taken high-luminosity data runs in 2019 and 2021 that will explore new dark photon phase space.

hep-ex

Search for a Dark Photon in Electro-Produced $e^{+}e^{-}$ Pairs with the Heavy Photon Search Experiment at JLab

The Heavy Photon Search experiment took its first data in a 2015 engineering run using a 1.056 GeV, 50 nA electron beam provided by CEBAF at the Thomas Jefferson National Accelerator Facility, searching for an electro-produced dark photon. Using 1.7 days (1170 nb$^{-1}$) of data, a search for a resonance in the $e^{+}e^{-}$ invariant mass distribution between 19 and 81 MeV/c$^2$ showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times10^{-6}$. In addition, a search for displaced dark photon decays did not rule out any territory but resulted in a reliable analysis procedure that will probe hitherto unexplored parameter space with future, higher luminosity runs.

hep-ex

Search for a Dark Photon in Electro-Produced $e^{+}e^{-}$ Pairs with the Heavy Photon Search Experiment at JLab

The Heavy Photon Search experiment took its first data in a 2015 engineering run at the Thomas Jefferson National Accelerator Facility, searching for a prompt, electro-produced dark photon with a mass between 19 and 81 MeV/$c^2$. A search for a resonance in the $e^{+}e^{-}$ invariant mass distribution, using 1.7 days (1170 nb$^{-1}$) of data, showed no evidence of dark photon decays above the large QED background, confirming earlier searches and demonstrating the full functionality of the experiment. Upper limits on the square of the coupling of the dark photon to the Standard Model photon are set at the level of 6$\times10^{-6}$. Future runs with higher luminosity will explore new territory.

hep-ex