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Register a new userInvestigation of interaction of circularly and linearly polarized photon beams with polarized 3He target
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Photodisintegration of polarized 3He by linearly or circularily polarized photons offers a rich choice of observables which can be calculated with high precision using a rigorous scheme of three-nucleon Faddeev equations. Using the (semi)phenomenological AV18 nucleon-nucleon potential combined with the Urbana IX three-nucleon force we investigate sensitivity of 3He photodisintegration observables to underlying currents taken in the form of a single-nucleon current supplemented by two-body contributions for $pi$- and $rho$-meson exchanges or incorporated by the Siegert theorem. Promising observables to be measured for two- and three-body fragmentation of 3He are identified. These observables form a challenging test ground for consistent forces and currents being under derivation within the framework of chiral perturbation theory. For thre-body 3He photodisintegration several kinematicaly complete configurations, including SST and FSI, are also discussed.
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Inclusive 3He(e,e) and exclusive 3He(e,en) processes with polarized electrons and 3He have been theoretically analyzed and values for the magnetic and electric neutron form factors have been extracted. In both cases the form factor values agree well with the ones extracted from processes on the deuteron. Our results are based on Faddeev solutions, modern NN forces and partially on the incorporation of mesonic exchange currents.
Proton-3He scattering is one of the good probes to study the T=3/2 channel of three--nucleon forces. We have measured 3He analyzing powers for p-3He elastic scattering with the polarized 3He target at 70 and 100 MeV. The data are compared with the theoretical predictions based on the modern nucleon--nucleon potentials. Large discrepancies are found between the data and the calculations at the angles where the 3He analyzing power takes the minimum and maximum values, which are not explained by taking into account Delta-isobar degrees of freedom.
We show that the asymmetries in the nuclear resonance fluorescence processes with a circular polarized photon beam may be used as a tool for studying the parity non-conservation (PNC) in nuclei. The PNC asymmetry measurements both in exciting the parity doublet states and in exciting the discrete states near the ground states with parity mixing are discussed. We derived the formulae needed for measuring the PNC asymmetries.
The gas breakdown produced by high-power pulsed linearly and circularly polarized microwave fields which are much weaker than the atomic fields is investigated in the non-relativistic limit. Obtained the electron distribution function produced by the interaction with intense linearly and circularly polarized microwave fields, it is shown that it is non-equilibrium and anisotropic. Finding the general dispersion relation and analyzing it, we firstly obtain the low frequency oscillations and secondly we show that an instability may develop in the aforementioned system. It will be shown that for linearly polarized microwave fields this instability may always develop but for the circular polarization fields it grows only when ion density is higher than a critical density.
The Breit-Wheeler process which produces matter and anti-matter from photon collisions is investigated experimentally through the observation of 6085 exclusive electron-positron pairs in ultra-peripheral Au+Au collisions at $sqrt{s_{_{NN}}}=200$ GeV. The measurements reveal a large fourth-order angular modulation of $cos{4Deltaphi}=(16.8pm2.5)%$ and smooth invariant mass distribution absent of vector mesons ($phi$, $omega$ and $rho$) at the experimental limit of $le 0.2%$ of the observed yields. The differential cross section as a function of $e^+e^-$ pair transverse momentum $P_perp$ peaks at low value with $sqrt{ langle P_perp^2 rangle } = 38.1pm0.9$ MeV and displays a significant centrality dependence. These features are consistent with QED calculations for the collision of linearly polarized photons quantized from the extremely strong electromagnetic fields generated by the highly charged Au nuclei at ultra-relativistic speed. The experimental results have implications for vacuum birefringence and for mapping the magnetic field which is important for emergent QCD phenomena.
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