Search results for "form factor [N(1535)]"
showing 10 items of 205 documents
Hyperon Semileptonic Decays and CKM Unitarity
2005
We perform a new numerical analysis of hyperon semileptonic decays emphasizing the systematic uncertainties. The poor understanding of SU(3) symmetry breaking effects at second order in the vector form factor translates into a large error of |V(us)|. Using our determination |V(us)| = 0.226 +/- 0.005 together with those coming from other sources we test the unitarity of the CKM matrix.
Deuteron electrodisintegration near threshold with the Bonn potential
1987
Deuteron electrodisintegration near threshold is calculated for the Bonn potential including consistent meson exchange currents. Experimental data can fairly well be described over the whole q-range if GE is used as electromagnetic form factor for the exchange current, whereas F1 leads to a large overestimation at high q.
Interpretation of the High-Energy ProcessesO16(γ,p0)N15andO16(γ,n0)O15
1978
Calculations based on a two-nucleon ($n\ensuremath{-}p$) absorption mechanism show that the form factor of the residual nucleus plays an important role in determining the shape of the photoproduction cross section in a wide energy range $60 \mathrm{MeV}l~{E}_{\ensuremath{\gamma}}l~300 \mathrm{MeV}$.
Differential cross sections for coherent and incoherent neutral-pion photoproduction from calcium
1989
Differential and absolute cross sections for the coherent reaction $^{40}\mathrm{Ca}$(\ensuremath{\gamma},${\ensuremath{\pi}}^{0}$${)}^{40}$Ca g.s., as well as for the incoherent reaction $^{40}\mathrm{Ca}$(\ensuremath{\gamma},${\mathrm{\ensuremath{\pi}}}^{0}$${)}^{40}$Ca(g.s.), have been measured with monochromatic photons in the threshold region (${E}_{\ensuremath{\gamma}}$=157--169 MeV). The differential cross section for the coherent process exhibits a diffraction minimum due to the nuclear mass form factor while the incoherent cross section is rather structureless. The cross sections are in good agreement with recent distorted-wave impulse-approximation calculations.
New physics in the kinematic distributions of B¯→D(*)τ−(→ℓ−ν¯ℓντ)ν¯τ
2016
We investigate the experimentally accessible kinematic distributions of the $\overline{B}\ensuremath{\rightarrow}{D}^{(*)}{\ensuremath{\tau}}^{\ensuremath{-}}(\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}{\ensuremath{\nu}}_{\ensuremath{\tau}}){\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ decays. Specifically, we study the decay rates as functions of the $B\ensuremath{\rightarrow}{D}^{(*)}$ transferred squared momentum, the energy of the final charged lepton and the angle of its 3-momentum with respect to the 3-momentum of the recoiling ${D}^{(*)}$. The angular distribution allows to introduce new observables, like a forwar…
Production ofWZEvents inpp¯Collisions ats=1.96 TeVand Limits on AnomalousWWZCouplings
2005
We present results from a search for WZ production with subsequent decay to l nu l'(l) over bar'(l and l' = e or mu) using 0.30 fb(-1) of data collected by the D0 experiment between 2002 and 2004 at the Fermilab Tevatron. Three events with WZ decay characteristics are observed. With an estimated background of 0.71 +/- 0.08 events, we measure the WZ production cross section to be 4.5(-2.6)(+3.8) pb, with a 95% C.L. upper limit of 13.3 pb. The 95% C.L. limits for anomalous WWZ couplings are found to be -2.0 <Delta kappa(Z)< 2.4 for form factor scale Lambda=1 TeV, and -0.48 <lambda(Z)< 0.48 and -0.49 <Delta g(1)(Z)< 0.66 for Lambda=1.5 TeV.
Lattice QCD and the timelike pion form factor.
2011
We present a formula that allows one to calculate the pion form factor in the timelike region 2mpi <= sqrt{s} <= 4mpi in lattice QCD. The form factor quantifies the contribution of two-pion states to the vacuum polarization. It must be known very accurately in order to reduce the theoretical uncertainty on the anomalous magnetic moment of the muon. At the same time, the formula constitutes a rare example where, in a restricted kinematic regime, the spectral function of a conserved current can be determined from Euclidean observables without an explicit analytic continuation.
η′transition form factor from space- and timelike experimental data
2016
The ${\ensuremath{\eta}}^{\ensuremath{'}}$ transition form factor is reanalyzed in view of the recent first observation by BESIII of the Dalitz decay ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\gamma}{e}^{+}{e}^{\ensuremath{-}}$ in both space- and timelike regions at low and intermediate energies using the Pad\'e approximants method. The present analysis provides a suitable parametrization for reproducing the measured form factor in the whole energy region and allows one to extract the corresponding low-energy parameters together with a prediction of their values at the origin, related to ${\mathrm{\ensuremath{\Gamma}}}_{{\ensuremath{\eta}}^{\ensuremath{'}}\ens…
Isovector electromagnetic form factors of the nucleon from lattice QCD and the proton radius puzzle
2021
Physical review / D 103(9), 094522 (2021). doi:10.1103/PhysRevD.103.094522
Constraints on electromagnetic form factors of sub-GeV dark matter from the cosmic microwave background anisotropy
2021
We consider dark matter which have non-zero electromagnetic form factors like electric/magnetic dipole moments and anapole moment for fermionic dark matter and Rayleigh form factor for scalar dark matter. We consider dark matter mass $m_\chi > \cal{ O}({\rm MeV})$ and put constraints on their mass and electromagnetic couplings from CMB and LSS observations. Fermionic dark matter with non-zero electromagnetic form factors can annihilate to $e^+ e^-$ and scalar dark matter can annihilate to $2\gamma$ at the time of recombination and distort the CMB. We analyze dark matter with multipole moments with Planck and BAO observations. We find upper bounds on anapole moment $g_{A}<7.163\times 10^{3} …