Search results for "Proton"
showing 10 items of 5886 documents
Collective neutrino-pair emission due to Cooper pairing of protons in superconducting neutron stars
2000
The neutrino emission due to formation and breaking of Cooper pairs of protons in superconducting cores of neutron stars is considered with taking into account the electromagnetic coupling of protons to ambient electrons. It is shown that collective response of electrons to the proton quantum transition contributes coherently to the complete interaction with a neutrino field and enhances the neutrino-pair production. Our calculation shows that the contribution of the vector weak current to the $\nu \bar{\nu}$ emissivity of protons is much larger than that calculated by different authors without taking into account the plasma effects. Partial contribution of the pairing protons to the total …
Radiative and non radiative muon capture on the proton in heavy baryon chiral perturbation theory
1998
We have evaluated the amplitude for muon capture by a proton, mu + p --> n + nu, to O(p^3) within the context of heavy baryon chiral perturbation theory (HBChPT) using the new O(p^3) Lagrangian of Ecker and Mojzis (E&M). We obtain expressions for the standard muon capture form factors and determine three of the coefficients of the E&M Lagrangian, namely, b_7, b_{19}, and b_{23}. We describe progress on the next step, a calculation of the radiative muon capture process, mu + p --> n + nu + gamma.
Compton scattering on the pion and radiative pion photoproduction from the proton
1994
The contribution of the pion polarizabilities to radiative pion photoproduction has been investigated. It has been shown how an extrapolation of future experimental data on radiative pion photoproduction to the pion pole can give information on the polarizabilities of pion.
PHOTOPRODUCTION OF η AND η′ MESONS ON THE NUCLEON
2007
The isobar models η-MAID and η′-MAID have been used to analyze new data on quasi-free η photoproduction on the deuteron from Bonn and recent η′ data on the proton from Jlab. In η photoproduction on the neutron a bump around W = 1700 MeV was observed which could possibly arise from a narrow P11 state that is discussed as a non-strange member of the Θ+ antidecuplett. In η′ photoproduction on the proton resonance contributions are found that can be attributed to missing resonances in the energy region around W = 1900 MeV .
Measurement ofK+production cross section by 8 GeV protons using high-energy neutrino interactions in the SciBooNE detector
2011
The SciBooNE Collaboration reports K+ production cross section and rate measurements using high energy daughter muon neutrino scattering data off the SciBar polystyrene (C8H8) target in the SciBooNE detector. The K+ mesons are produced by 8 GeV protons striking a beryllium target in Fermilab Booster Neutrino Beam line (BNB). Using observed neutrino and antineutrino events in SciBooNE, we measure d2σ/dpdΩ = (5.34 ±0.76) mb/(GeV/c x sr) for p + Be =K+ + X at mean K+ energy of 3.9 GeV and angle (with respect to the proton beam direction) of 3.7 degrees, corresponding to the selected K+ sample. Compared to Monte Carlo predictions using previous higher energy K+ production measurements, this mea…
Study of several double-beta-decaying nuclei using the renormalized proton-neutron quasiparticle random-phase approximation
1997
The renormalized proton-neutron quasiparticle random-phase approximation model (RQRPA) has been used to calculate double-\ensuremath{\beta}-decay matrix elements and associated transition half-lives for two-neutrino double \ensuremath{\beta} decay of parent nuclei ${}^{76}\mathrm{Ge},$ ${}^{78}\mathrm{Kr},$ ${}^{82}\mathrm{Se},$ ${}^{96}\mathrm{Zr},$ ${}^{106}\mathrm{Cd},$ and ${}^{130}\mathrm{Te}$ to the ground state and excited one- and two-phonon states of their daughter nuclei. The results are compared to ordinary proton-neutron QRPA and experiments. In addition, the violation of the Ikeda sum rule in the RQRPA is examined and discussed.
GT neutrino–nuclear responses for double beta decays and astro neutrinos
2015
Gamow–Teller nuclear matrix elements (NMEs) for pairs of ground-state-to-ground-state transitions, in particular their geometric mean NME , are studied. The observed means in the medium-heavy mass region are compared with the corresponding single-quasiparticle (qp) NMEs and the means calculated by the proton neutron qp random-phase approximation (pnQRPA). The NMEs turn out to be insensitive to the nucleon occupancy/vacancy amplitudes and to the particle–particle interaction parameter of the pnQRPA. The observed mean NMEs are found to be reduced by a coefficient relative to the effective qp NMEs and by a coefficient with respect to the pnQRPA NMEs. The reductions associated with the spin iso…
A modified born term model for π± Δ electroproduction
1974
An electric Born type model is used to describeπ±Δ electroproduction at high energies. The electric pion form factor is taken from VDM; the contact term form factor and theΔ form factor are set equal to the proton form factor (or equal to zero) which is left as an arbitrary parameter, and is determined by a fit of the model to the recentπ+δ0 andπ−Δ++ electroproduction data.
Particle production from the Color Glass Condensate: proton-nucleus collisions in light of the HERA data
2014
We compute single inclusive hadron production in proton-proton and proton-nucleus collisions consistently within the CGC framework. The parameters in the calculations are obtained from electron-proton DIS and standard nuclear geometry. We obtain a good description of the DIS data without an anomalous dimension in the initial condition of the BK evolution and get a good agreement with the available single inclusive proton-proton and proton-nucleus data.
Multi-nucleon mechanism for subthreshold antiproton production in proton-nucleus reactions
1995
We study a many-body (multipion) mechanism for ¯p subthreshold production in proton-nucleus collisions. The incoming proton and the interacting nucleons in the target act as sources of pions that merge to produce a nucleon-antiproton pair. The calculation takes fully into account the initial state interaction and antiproton absorption in the final state. The cooperation of several nucleons in the initial state reduces the threshold for the reaction allowing for production rates that may account for 15–50% of the total ¯p production. We point out that this contribution should be added to the primary ¯p production mechanism due toΔ formation and rescattering, as found by other groups, and sho…