D. Paudyal
A5057048930- Quantum Chromodynamics and Particle Interactions
- Particle physics theoretical and experimental studies
- Nuclear physics research studies
- High-Energy Particle Collisions Research
- Atomic and Subatomic Physics Research
- Advanced NMR Techniques and Applications
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Nuclear Physics and Applications
- Machine Learning in Materials Science
- Computational Physics and Python Applications
- Dark Matter and Cosmic Phenomena
- Crystallography and Radiation Phenomena
- Medical Imaging Techniques and Applications
- Quantum Dots Synthesis And Properties
- Magnetic confinement fusion research
- Chalcogenide Semiconductor Thin Films
University of Regina
2015-2024
University of Basel
2023
Johannes Gutenberg University Mainz
2017-2023
George Washington University
2023
University of Glasgow
2015
University of Edinburgh
2015
The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96 GeV with tagged-photon facilities at Mainz Microtron, MAMI. Differential cross sections obtained unprecedented statistical accuracy, providing fine binning full production-angle coverage. A strong cusp is observed in total section for η photoproduction energies vicinity of η^{'} threshold, W=1896 MeV (E_{γ}=1447 MeV). Within framework a revised ηMAID isobar model, cusp, connection...
The Dalitz decays eta -> e^+e^-g and omega pi^0 e^+e^- have been measured in the g p reactions, respectively, with A2 tagged-photon facility at Mainz Microtron, MAMI. value obtained for slope parameter of electromagnetic transition form factor eta, Lambda^{-2}_eta=(1.97+/-0.11_tot) GeV^{-2}, is good agreement previous measurements mu^+mu^-g decays. uncertainty Lambda^{-2}_eta lower than results based on decay. parameter, Lambda^{-2}_omega_pi^0 = (1.99+/-0.21_tot) somewhat mu^+mu^-, but are...
Differential cross sections for the gamma p -> pi^0 reaction have been measured with A2 tagged-photon facilities at Mainz Microtron, MAMI C, up to center-of-mass energy W=1.9 GeV. The new results, obtained a fine and angular binning, increase existing quantity of photoproduction data by ~47%. Owing unprecedented statistical accuracy full coverage, results are sensitive high partial-wave amplitudes. This is demonstrated decomposition differential in terms Legendre polynomials further...
The double polarization observable E and the helicity dependent cross sections σ_{1/2} σ_{3/2} were measured for η photoproduction from quasifree protons neutrons. circularly polarized tagged photon beam of A2 experiment at Mainz MAMI accelerator was used in combination with a longitudinally deuterated butanol target. almost 4π detector setup Crystal Ball TAPS is ideally suited to detect recoil nucleons decay photons η→2γ η→3π^{0}. results show that narrow structure previously observed...
A precise measurement of the differential cross sections dσ/dΩ and linearly polarized photon beam asymmetry Σ_{3} for Compton scattering on proton below pion threshold has been performed with a tagged almost 4π detector at Mainz Microtron. The incident photons were produced by recently upgraded Glasgow-Mainz tagging facility impinged cryogenic liquid hydrogen target, scattered detected in Crystal Ball/TAPS setup. Using highest statistics data ever measured along two effective field theories...
The Dalitz decay π0→e+e−γ has been measured in the γp→π0p reaction with A2 tagged-photon facility at Mainz Microtron, MAMI. value obtained for slope parameter of π0 electromagnetic transition form factor, aπ=0.030±0.010tot, is agreement existing measurements this and recent theoretical calculations. uncertainty aπ lower than previous results based on decay.Received 16 November 2016DOI:https://doi.org/10.1103/PhysRevC.95.025202©2017 American Physical SocietyPhysics Subject Headings...
The $\ensuremath{\gamma}n\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}n$ differential cross section evaluated for 27 energy bins span the photon-energy range 290--813 MeV ($W=1.195$--1.553 GeV) and pion c.m. polar production angles, ranging from ${18}^{\ensuremath{\circ}}$ to ${162}^{\ensuremath{\circ}}$, making use of model-dependent nuclear corrections extract ${\ensuremath{\pi}}^{0}$ data on neutron measurements deuteron target. Additionally, total photoabsorption was measured. tagged...
Precise helicity-dependent cross sections and the double-polarization observable $E$ were measured for $\ensuremath{\eta}$ photoproduction from quasifree protons neutrons bound in deuteron. The $\ensuremath{\eta}\ensuremath{\rightarrow}2\ensuremath{\gamma}$ $\ensuremath{\eta}\ensuremath{\rightarrow}3{\ensuremath{\pi}}^{0}\ensuremath{\rightarrow}6\ensuremath{\gamma}$ decay modes used to optimize statistical quality of data estimate systematic uncertainties. measurement A2 detector setup at...
The double-polarization observable $E$ and the helicity-dependent cross sections $\sigma_{1/2}$ $\sigma_{3/2}$ have been measured for first time single $\pi^{0}$ photoproduction from protons neutrons bound in deuteron at electron accelerator facility MAMI Mainz, Germany. experiment used a circularly polarized photon beam longitudinally deuterated butanol target. reaction products, recoil nucleons decay photons $\pi^0$ meson were detected with Crystal Ball TAPS electromagnetic calorimeters....
This work measured $d\sigma/d\Omega$ for neutral kaon photoproduction reactions from threshold up to a c.m.\ energy of 1855MeV, focussing specifically on the $\gamma p\rightarrow K^0\Sigma^+$, n\rightarrow K^0\Lambda$, and K^0 \Sigma^0$ reactions. Our results are first-ever measurements that reaction. These data will provide insight into properties $N^*$ resonances and, in particular, lead an improved knowledge about those states couple only weakly $\pi N$ channel. Integrated cross sections...
We report a measurement of the spin polarisation recoiling neutron in deuterium photodisintegration, utilising new large acceptance polarimeter within Crystal Ball at MAMI. The measured photon energy range 300~--~700~MeV provides first recoil energies where quark substructure deuteron plays role, thereby providing important constraints on photodisintegration mechanisms. A very high narrow structure centred around $E_{\gamma}\sim$~570~MeV is observed, which inconsistent with current...
The largest, at the moment, statistics of 7x10^6 eta->3pi^0 decays, based on 6.2x10^7 eta mesons produced in gamma p -> reaction, has been accumulated by A2 Collaboration Mainz Microtron, MAMI. It allowed a detailed study dynamics beyond its conventional parametrization with just quadratic slope parameter alpha and enabled, for first time, measurement second-order term better understanding cusp structure neutral decay. present data are also compared to recent theoretical calculations that...
Polarisation-dependent differential cross sections σT associated with the target asymmetry T have been measured for reaction γp→→pπ0 transverse polarisation from π0 threshold to photon energies of 190 MeV. The data were obtained using a frozen-spin butanol Crystal Ball / TAPS detector set-up and Glasgow tagging system at Mainz Microtron MAMI. Results used in combination our previous measurements unpolarised section σ0 beam Σ model-independent determination S- P-wave multipoles region, which...
The data available from the A2 Collaboration at MAMI were analyzed to select γp→π0ηp reaction on an event-by-event basis, which allows for partial-wave analyses of three-body final states obtain more reliable results, compared fits measured distributions. These provide world's best statistical accuracy in energy range threshold Eγ=1.45 GeV, allowing a finer binning measurement all observables needed understanding dynamics. results obtained are existing models, and impact new is checked by...
The Compton double-polarization observable ${\mathrm{\ensuremath{\Sigma}}}_{2z}$ has been measured for the first time in $\mathrm{\ensuremath{\Delta}}(1232)$ resonance region using a circularly polarized photon beam incident on longitudinally proton target at Mainz Microtron. This paper reports these results, together with model-dependent extraction of four spin polarizabilities from fits to additional asymmetry data either dispersion relation calculation or baryon chiral perturbation theory...
We report the first large-acceptance measurement of beam-spin asymmetry for deuteron photodisintegration ($\vec{\gamma} d\to pn$) in photon energy range $400<E_{\gamma}<630$~MeV. The provides important new constraints on mechanisms above delta resonance and photocoupling recently discovered $d^*(2380)$ hexaquark.
High-statistics measurements of the photon asymmetry $\Sigma$ for $\overrightarrow{\gamma}p\rightarrow\pi^{0}p$ reaction have been made in center-of-mass energy range $W=1214-1450$ MeV. The data were measured with MAMI A2 real beam and Crystal Ball/TAPS detector systems Mainz, Germany. results significantly improve existing world are shown to be good agreement previous measurements, MAID, SAID, Bonn-Gatchina predictions. We also combined recent cross-section from Mainz calculate profile...
The transition from the nucleon to $\mathrm{\ensuremath{\Delta}}(1232)$ resonance is a sensitive test for models of structure. A magnetic dipole ($M1$) quark spin-flip essentially dominates photoexcitation $\mathrm{\ensuremath{\Delta}}$, but smaller components in and $\mathrm{\ensuremath{\Delta}}$ wave functions allow also electric quadrupole ($E2$) contributions. ratio $E2/M1$ then provides fundamental information on both spatial deformation or corresponding $D$ states their quark-model...
Background: Photoproduction of mesons off quasifree nucleons bound in the deuteron allows us to study electromagnetic excitation spectrum neutron and isospin structure nucleon resonances. The database for such reactions is much more sparse than free proton targets.Purpose: Study experimentally single ${\ensuremath{\pi}}^{0}$ photoproduction from deuteron. Investigate nuclear effects by a comparison results protons protons. Use data (corrected effects) test predictions reaction models partial...
An experimental study of the η′→π0π0η→6γ decay has been conducted with best up-to-date statistical accuracy, by measuring η′ mesons produced in γp→η′p reaction A2 tagged-photon facility at Mainz Microtron, MAMI. The results obtained for standard parametrization η′→π0π0η matrix element are consistent most recent η′→ππη decays, but have smaller uncertainties. available statistics and resolution allowed, first time, an observation a structure below π+π− mass threshold, magnitude sign which,...
The helicity-dependent cross sections for the photoproduction of $\pi^0\eta$ pairs have been measured first time. experiment was performed at tagged photon facility Mainz MAMI accelerator with combined Crystal Ball - TAPS calorimeter. used a polarized deuterated butanol target and circularly beam. This arrangement allowed $\sigma_{1/2}$ (photon spin antiparallel) $\sigma_{3/2}$ (parallel spins) components to be quasi-free production off protons neutrons. main finding is that two helicity...
The A2 collaboration at the Mainz Microtron has undertaken a program of Compton scattering experiments with goal extracting proton and, in future, neutron polarizabilities. These are fundamental parameters that describe response nucleon to an electromagnetic field. An extraction these will provide crucial test QCD theories. This talk presented concept and status this program, including some preliminary results.
The double-polarization observable $E$ and helicity-dependent cross sections $\sigma_{1/2}$, $\sigma_{3/2}$ have been measured for the photoproduction of $\pi^0$ pairs off quasi-free protons neutrons at Mainz MAMI accelerator with Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally electrons impinged on a deuterated butanol target. reaction products were detected an almost $4\pi$ covering calorimeter. results reveal first time...
Photoproduction of π0π±-pairs from quasifree nucleons bound in the deuteron has been investigated to study helicity dependence this reaction. Measurements with a liquid deuterium target were used extract unpolarized cross sections for reactions on protons and neutrons. A deuterated, longitudinally polarized solid-butanol target, together circularly photon beam, determined double polarization observable E. From these results spin-dependent σ1/2 σ3/2, corresponding anti-parallel parallel spin...