119494911
Deuteron Compton scattering in effective field theory and spin-independent nucleon polarizabilities
Abstract Deuteron Compton scattering is calculated to O ( Q 2 ) in pionless effective field theory using a dibaryon approach. The vector amplitude, which was not included in the previous pionless calculations, contributes to the cross section at O ( Q 2 ) and influences significantly the extracted values of nucleon electric polarizability at incident photon energy 49 MeV. We recommend future high precision deuteron Compton scattering experiments being performed at 25–35 MeV photon energy where the nucleon polarizability effects are appreciable and the pionless effective field theory is most reliable. For example, a measurement at 30 MeV with a 3% error will constrain the isoscalar nucleon electric polarizability α 0 with a ∼30% error.
119512566
Drell-Hearn-Gerasimov sum-rule for the deuteron in nuclear effective field theory
Abstract The Drell–Hearn–Gerasimov sum rule for the deuteron is studied in nuclear effective field theory. The low-energy theorem for the spin-dependent Compton amplitude f 1 ( ω ) is derived to the next-to-leading order in low-energy expansion. The spin-dependent photo-disintegration cross-section σ P − σ A is calculated to the same order, and its contribution to the dispersive integral is evaluated.
120566938
Direct detection of hot dark matter in the form of active and sterile neutrinos
Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM) in the Universe. We consider the beta-decaying (e.g., 3H) and EC-decaying (e.g., 163Ho) nuclei as the most promising targets to capture hot DM in the laboratory. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta decay or electron capture (EC) decay backgrounds in the (3+Ns) flavor mixing scheme. We stress that such direct measurements of hot DM might not be hopeless in the long term.
7909334
Anomalies and graded coisotropic branes
We compute the anomaly of the axial U(1) current in the A-model on a CalabiYau manifold, in the presence of coisotropic branes discovered by Kapustin and Orlov. Our results relate the anomaly-free condition to a recently proposed definition of graded coisotropic branes in Calabi-Yau manifolds. More specifically, we find that a coisotropic brane is anomaly-free if and only if it is gradable. We also comment on a different grading for coisotropic submanifolds introduced recently by Oh.
119448092
Electroweak bremsstrahlung from neutron-neutron scattering
Background: Nucleon-nucleon (NN) bremsstrahlung processes NN{gamma} (nn{gamma}, np{gamma}, and pp{gamma}) have been extensively investigated. Neutrino-pair bremsstrahlung processes from nucleon-nucleon scattering NN{nu}{nu} (nn{nu}{nu}, np{nu}{nu}, and pp{nu}{nu}) have recently attracted attention in studies of neutrino emission in neutron stars. The calculated NN{nu}{nu} cross sections (or emissivities) are found to be sensitive to the two-nucleon dynamical model used in the calculations. Purpose and Method: A realistic one-boson-exchange (ROBE) model for NN interactions is used to construct the electroweak bremsstrahlung amplitudes using the well-known nucleon electromagnetic and weak interaction vertices. The constructed nn{gamma} and nn{nu}{nu} amplitudes are investigated by applying them to calculate nn{gamma} and nn{nu}{nu} cross sections, respectively. Results: (i) The 190-MeV ROBE nn{gamma} cross sections agree well with those calculated using the TuTts amplitude, but they are in disagreement with those calculated using the Low amplitude. (ii) The calculated nn{nu}{nu} cross sections using the ROBE amplitude at the neutrino-pair energy {omega} = 1 MeV are in quantitative agreement with those calculated by Timmermans et al.[Phys. Rev. C 65, 064007 (2002)], who used the leading-order term of the soft neutrino-pair bremsstrahlung amplitude. Conclusions: The nn{gamma} amplitude in the ROBE approach, which obeys the soft-photon theorem, has a predictive power similar to that ofmore » the TuTts amplitude. The nn{nu}{nu} amplitude in the ROBE approach, which is consistent with the soft neutrino-pair bremsstrahlung theorem, has a predictive power similar to that of the soft neutrino-pair bremsstrahlung amplitude of Timmermans et al. in the low neutrino-pair energy region.« less
118518380
Investigating the Effect of Family Non-universal $Z^\prime$ Boson in $B \to \phi\phi$ Decay
Within the perturbative QCD approach, we re-calculate the branching ratio and polarization fractions of the pure annihilation decay $B \to \phi \phi$ in both the standard model (SM) and the family non-universal $Z^\prime$ model. We find that this decay is dominated by the longitudinal part, while the transverse parts are negligibly due to the absence of the $(S-P)(S+P)$-type operator. In SM, the branching ratio is predicted as $(4.4^{+0.8+0.3}_{-0.6-0.5}) \times 10^{-8}$, which is larger than the previous predictions. With an additional $Z^\prime$ boson, the branching ratio can be enhanced by a factor of 2, or reduced one half in the allowed parameters space. These results will be tested by the ongoing LHCb experiment and forthcoming Super-B experiments. Moreover, if the $Z^\prime$ boson could be directly detected at hadron collider, this decay can be used to constrain its mass and the couplings in turn.
123140582
Proton-proton bremsstrahlung calculation : Comparison with recent high-precision experimental results
Proton-proton bremsstrahlung cross sections and analyzing powers have been calculated at 190 MeV by using a one-boson-exchange model. The results are compared with the recently published high-precision Kernfysisch-Versneller-Instituut (KVI) data. Satisfactory agreement between theory and experiment has been found.