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Khandaker, M. [Norfolk State University]

Publications and source records attributed to Khandaker, M. [Norfolk State University].

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

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↗
DOE OSTI2026

Proton transparency and neutrino physics: New methods and modeling

Extracting accurate results from neutrino oscillation and cross section experiments requires accurate simulation of the neutrino-nucleus interaction. The rescattering of outgoing hadrons (final state interactions) by the rest of the nucleus is an important component of these interactions. We present a new measurement of proton transparency (defined as the fraction of outgoing protons that emerge without significant rescattering) using electron-nucleus scattering data recorded by the CLAS detector at Jefferson Laboratory on helium, carbon, and iron targets. This analysis uses a new data-driven method to extract the transparency. It defines transparency as the ratio of electron-scattering events with a detected proton to quasi-elastic electron-scattering events where a proton should have been knocked out. Our results are consistent with previous measurements that determined the transparency from the ratio of measured events to theoretically predicted events. We find that the GENIE event generator, which is widely used by oscillation experiments to simulate neutrino-nucleus interactions, needs to better describe both the nuclear ground state and proton rescattering in order to reproduce our measured transparency ratios, especially at lower proton momenta.

direct reactions↗
DOE OSTI2025

Measurement of single- and double-polarization observables in the photoproduction of πœ‹ + β’πœ‹ βˆ’ meson pairs off the proton using CLAS at Jefferson Laboratory

The photoproduction of πœ‹ + β’πœ‹ βˆ’ meson pairs off the proton has been studied in the reaction π›Ύβ’π‘β†’π‘β’πœ‹ + β’πœ‹ βˆ’ using the CEBAF Large Acceptance Spectrometer (CLAS) and the frozen-spin target (FROST) in Hall B at the Thomas Jefferson National Accelerator Facility. For the first time, the beam and target asymmetries, 𝐼 𝑠,𝑐 and 𝑃 π‘₯,𝑦 , have been measured along with the beam-target double-polarization observables, 𝑃$^{𝑠,𝑐}_{π‘₯,𝑦}$, using a transversely polarized target with center-of-mass energies ranging from 1.51 GeV up to 2.04 GeV. These data and additional πœ‹β’πœ‹ photoproduction observables from CLAS and experiments elsewhere were included in a partial-wave analysis within the Bonn-Gatchina framework. Significant contributions from 𝑠-channel resonance production are observed in addition to 𝑑-channel exchange processes. The data indicate significant contributions from 𝑁* and Ξ”* resonances in the third and fourth resonance regions.

QCD phenomenology↗
DOE OSTI2025

Photoproduction of two charged pions off protons in the resonance region

Photoproduction of charged pions pairs off protons is studied within the invariant masses of the final state hadrons from 1.6 to 2.4 GeV at the Thomas Jefferson National Accelerator Facility with the CLAS detector. The total and differential cross sections and spin-density matrix elements are presented for the isobars pρ 0 (770), Ξ”(1232) ++ Ο€ βˆ’ , and Ξ”(1232) 0 Ο€ + . The data are included in the Bonn-Gatchina coupled-channel analysis and provide the information necessary to determine the branching fractions of Nρ(770) decays for most known N* and Ξ”* resonances. For the first time, the Nρ branching ratios are obtained here from an event-based likelihood to Ξ³p β†’ Ο€ + Ο€ βˆ’ p.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Measurement of the nucleon spin structure functions for 0.01 < 𝑄 2 < 1 GeV 2 using CLAS

The spin structure functions of the proton and the deuteron were measured during the EG4 experiment at Jefferson Lab in 2006. Data were collected for longitudinally polarized electron scattering off longitudinally polarized NH 3 and ND 3 targets, for 𝑄 2 values as small as 0.012 and 0.02 GeV 2 , respectively, using the CEBAF Large Acceptance Spectrometer. This is the archival paper of the EG4 experiment that summarizes the previously reported results of the polarized structure functions 𝑔 1 , 𝐴 1 ⁒𝐹 1 , and their moments $\bar{Ξ“}$ 1 , $\bar{𝛾}$ 0 , and $\bar{𝐼}$ TT , for both the proton and the deuteron. In addition, we report on new results on the neutron 𝑔 1 extracted by combining proton and deuteron data and correcting for Fermi smearing, and on the neutron moments $\bar{Ξ“}$ 1 , $\bar{𝛾}$ 0 , and $\bar{𝐼}$ TT formed directly from those of the proton and the deuteron. Our data are in good agreement with the Gerasimov-Drell-Hearn sum rule for the proton, deuteron, and neutron. Furthermore, the isovector combination was formed for 𝑔 1 and the Bjorken integral $\bar{Ξ“}^{π‘βˆ’π‘›}_1$, and it was compared to available theoretical predictions. All of our results, to the best of our knowledge, provide for the first time extensive tests of spin observable predictions from chiral effective field theory (πœ’β’EFT) in a 𝑄 2 range commensurate with the pion mass. Finally, they motivate further improvement in πœ’β’EFT calculations from other approaches such as the lattice gauge method.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Dihadron azimuthal correlations in deep-inelastic scattering off nuclear targets

We measured the nuclear dependence of the di-pion azimuthal correlation function in deepinelastic scattering (DIS) using the CEBAF Large Acceptance Spectrometer (CLAS) and a 5 GeV electron beam. As the nuclear-target size increases, transitioning from deuterium to carbon, iron, and lead, the correlation function broadens monotonically. Its shape exhibits a significant dependence on kinematics, including the transverse momentum of the pions and the difference in their rapidity. None of the various Monte-Carlo event generators we evaluated could fully replicate the observed correlation functions and nuclear effects throughout the entire phase space. As the first study of its kind in DIS experiments, this research provides an important baseline for enhancing our understanding of the interplay between the nuclear medium and the hadronization process in these reactions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Photoproduction of the Ξ£ + hyperon using linearly polarized photons with CLAS

Measurements of the polarization observables Ξ£, P, T, O x , O z for the reaction $\vec{Ξ³}$ p β†’ $K^0_S$Ξ£ + using a linearly polarized photon beam of energy 1.1 to 2.1 GeV are reported. The measured data provide information on a channel that has not been studied extensively, but is required for a full coupled-channel analysis in the nucleon resonance region. Observables have been simultaneously extracted using likelihood sampling with a Markov-Chain Monte Carlo process. Angular distributions in bins of photon energy E Ξ³ are produced for each polarization observable. T, O x , and O z are first time measurements of these observables in this reaction. The extraction of Ξ£ extends the energy range beyond a previous measurement. The measurement of P, the recoil polarization, is consistent with previous measurements. The measured data are shown to be significant enough to affect the estimation of the nucleon resonance parameters when fitted within a coupled-channels model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗