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Gevorgyan, N. [Yerevan Physics Institute]

Publications and source records attributed to Gevorgyan, N. [Yerevan Physics Institute].

Polarization observables 𝑇 and 𝐹 in the π›Ύβ’π‘β†’πœ‹ 0 ⁒𝑝 reaction at CLAS

Pion photoproduction in the $\vec{Ξ³}$$\vec{p}$ β†’ Ο€ 0 p reaction has been measured in the FROzen Spin Target (FROST) experiment at the Thomas Jefferson National Accelerator Facility. In this experiment, circularly polarized photons with energies up to 3.082 GeV impinged on a transversely polarized frozen-spin target. Final-state protons were detected in the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer. The polarization observables T and F have been extracted for W from 1445 to 2525 MeV, of which the energy range is much broader, and the precision is better than the existing measurements in higher W ranges. The data generally agree with predictions of present partial-wave analyses but also show marked differences for higher W ranges. By incorporating the present data into the databases, the Scattering Analysis Interactive Data (SAID) fits have been improved with relatively small Ο‡ 2 and significant changes in the parameters of the (1910)1/2 + and N(2190)7/2 βˆ’ have been found with the JΓΌBo model.

particle production↗

First displaced vertex search for electroproduced dark-sector strongly interacting massive particles by the HPS experiment

The Heavy Photon Search experiment (HPS) is a fixed-target, electron beam experiment designed to search for 𝑒 + ⁒𝑒 βˆ’ mass resonances and displaced decays using a forward acceptance spectrometer. This paper details the search for naturally long-lived β€œdark” vector mesons (𝑉 𝐷 ) arising from a dark sector of beyond-Standard-Model strongly interacting massive particles, characterized by a QCD-like π‘†β’π‘ˆβ’(3) 𝐷 symmetry and coupled to the Standard Model photon via a new π‘ˆβ’(1) 𝐷 gauge interaction mediated by the β€œheavy photon,” or 𝐴′. The results are based on an integrated luminosity of 10 608 nb βˆ’1 collected during the 2016 HPS engineering run. The displaced vertex search for 𝑉 𝐷 β†’ 𝑒 +⁒ 𝑒 βˆ’ in the 𝑒 +⁒ 𝑒 βˆ’ invariant mass range 39–179 MeV showed no statistically significant evidence for signal above the QED background.

extensions of gauge sector↗