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Strakovsky, I. I.

Publications and source records attributed to Strakovsky, I. I..

13 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Electro- and photoproduction of muon pairs with $$\mu $$CLAS12: double deeply virtual compton scattering, timelike compton scattering, and $$J/\psi $$ production

The CEBAF Large Acceptance Spectrometer for operation at 12 GeV (CLAS12) at the Thomas Jefferson National Accelerator Facility has played a central role in advancing the understanding of nucleon and nuclear structure. As increasingly precise data become available, new physics opportunities emerge that extend beyond the current capabilities of CLAS12. In this article, a program to explore the quark and gluon structure of the nucleon through di-muon electro- and photoproduction is presented. Its primary focus is the measurement of beam-spin asymmetries in Double Deeply Virtual Compton Scattering, . By independently varying the incoming and outgoing photon virtualities and momentum transfer, the DDVCS measurement provides access to the Generalized Parton Distributions over their full three-dimensional phase space, extending beyond the kinematic constraints of Deeply Virtual Compton Scattering and Timelike Compton Scattering. In addition, the large acceptance and high luminosity of the CLAS12 experiment will enable precision measurements of near-threshold production and high-statistics studies of Timelike Compton Scattering.

Alvarado, J. S.↗
DOE OSTI2024

First Measurement Using Elliptically Polarized Photons of the Double-Polarization Observable E for γ p → p π 0 and γ p → n π +

We report the measurement of the helicity asymmetry E for the p π 0 and n π + final states using, for the first time, an elliptically polarized photon beam in combination with a longitudinally polarized target at the Crystal Ball experiment at MAMI. The results agree very well with data that were taken with a circularly polarized photon beam, showing that it is possible to simultaneously measure polarization observables that require linearly (e.g., G ) and circularly polarized photons (e.g., E ) and a longitudinally polarized target. The new data cover a photon energy range 270–1400 MeV for the p π 0 final state (230–842 MeV for the n π + final state) and the full range of pion polar angles, θ , providing the most precise measurement of the observable E . A moment analysis gives a clear observation of the p η cusp in the p π 0 final state. Published by the American Physical Society 2024

Physics↗
DOE OSTI2023

Measurement of the helicity asymmetry $${\mathbb {E}}$$ for the $$\vec {\gamma }\vec {p} \rightarrow p \pi ^0$$ reaction in the resonance region: The CLAS Collaboration

Abstract The double-spin-polarization observable $${\mathbb {E}}$$ E for $$\vec {\gamma }\vec {p}\rightarrow p\pi ^0$$ γ → p → → p π 0 has been measured with the CEBAF Large Acceptance Spectrometer (CLAS) at photon beam energies $$E_\gamma $$ E γ from 0.367 to $$2.173~\textrm{GeV}$$ 2.173 GeV (corresponding to center-of-mass energies from 1.240 to $$2.200~\textrm{GeV}$$ 2.200 GeV ) for pion center-of-mass angles, $$\cos \theta _{\pi ^0}^{c.m.}$$ cos θ π 0 c . m . , between $$-$$ - 0.86 and 0.82. These new CLAS measurements cover a broader energy range and have smaller uncertainties compared to previous CBELSA data and provide an important independent check on systematics. These measurements are compared to predictions as well as new global fits from The George Washington University, Mainz, and Bonn-Gatchina groups. Their inclusion in multipole analyses will allow us to refine our understanding of the single-pion production contribution to the Gerasimov-Drell-Hearn sum rule and improve the determination of resonance properties, which will be presented in a future publication.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

First measurement of polarisation transfer $C$$^{n}_{x'}$ in deuteron photodisintegration

A first measurement of the polarisation transfer from a circularly-polarised photon to the final state neutron ($C$$^{n}_{x'}$) in deuterium photodisintegration has been carried out. This quantity is determined over the photon energy range 370 – 700 MeV and for neutron centre-of-mass breakup angles ~ 45 – 120°. The polarisation of the final state neutrons was determined by an ancillary large-acceptance nucleon polarimeter, surrounding a cryogenic liquid deuterium target within the Crystal Ball detector at MAMI. The polarimeter characterised (n, p) charge exchange of the ejected neutrons to determine their polarisation. The new $C$$^{n}_{x'}$ data are also compared to a theoretical model based on nucleonic and nucleon resonance degrees of freedom constrained by the current world-database of deuterium photodisintegration measurements. Structures in $C$$^{n}_{x'}$ observed in the region of the d*(2380) could not be explained by conventional models of deuteron photodisintegration.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Single $\pi ^0$ production off neutrons bound in deuteron with linearly polarized photons

The quasifree γ → d → π 0 n(p) photon beam asymmetry, Σ, has been measured at photon energies, E γ , from 390 to 610 MeV, corresponding to center of mass energy from 1.271 to 1.424 GeV, for the first time. The data were collected in the A2 hall of the MAMI electron beam facility with the Crystal Ball and TAPS calorimeters covering pion center-of-mass angles from 49° to 148°. In this kinematic region, polarization observables are sensitive to contributions from the Δ(1232) and N(1440) resonances. The extracted values of Σ have been compared to predictions based on partial-wave analyses (PWAs) of the existing pion photoproduction database. Our comparison includes the SAID, MAID and Bonn–Gatchina analyses; while a revised SAID fit, including the new Σ measurements, has also been performed. In addition, isospin symmetry is examined as a way to predict π 0 n photoproduction observables, based on fits to published data in the channels π 0 p, π + n and π – p.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Threshold $\pi ^-$ photoproduction on the neutron

Recent data from the PIONS@MAX-lab Collaboration, measuring the total cross section of the incoherent pion photoproduction reaction, γd → π – pp, near threshold, have been used to extract the E 0+ multipole and total cross section of the reaction γn → π – p, also near threshold. These are the first measurements of the reaction γd → π – pp in the threshold region. The value of E 0+ is extracted through a fit to the deuteron data in a photoproduction model accounting for final-state interactions. The model takes an S-wave approximation for the elementary reaction γn → π – p with E 0+ = const in the threshold region. The fit over all the 6 deuteron data points gives the value E 0+ = –31.86 ± 0.8 (in units 10 –3 /mπ). We explore the dependence of our results on the choice of data subsets included in the fit. Here, the obtained values of E 0+ , for different subsets, have overlapping errors and agree with previous determinations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗