20 research outputs found
O(\alpha^2 \ln(m_\mu/m_e)) Corrections to Electron Energy Spectrum in Muon Decay
O(\alpha^2 \ln(m_\mu/m_e)) corrections to electron energy spectrum in muon
decay are computed using perturbative fragmentation function approach. The
magnitude of these corrections is comparable to anticipated precision of the
TWIST experiment at TRIUMF where Michel parameters will be extracted from the
measurement of the electron energy spectrum in muon decay.Comment: 8 pages, LaTeX, revtex4.cls, 1 PostScript figur
Triton binding energy calculated from the SU_6 quark-model nucleon-nucleon interaction
Properties of the three-nucleon bound state are examined in the Faddeev
formalism, in which the quark-model nucleon-nucleon interaction is explicitly
incorporated to calculate the off-shell T-matrix. The most recent version,
fss2, of the Kyoto-Niigata quark-model potential yields the ground-state energy
^3H=-8.514 MeV in the 34 channel calculation, when the np interaction is used
for the nucleon-nucleon interaction. The charge root mean square radii of the
^3H and ^3He are 1.72 fm and 1.90 fm, respectively, including the finite size
correction of the nucleons. These values are the closest to the experiments
among many results obtained by detailed Faddeev calculations employing modern
realistic nucleon-nucleon interaction models.Comment: 10 pages, no figure
Weak capture of protons by protons
The cross section for the proton weak capture reaction
is calculated with wave functions obtained from a number of modern, realistic
high-precision interactions. To minimize the uncertainty in the axial two-body
current operator, its matrix element has been adjusted to reproduce the
measured Gamow-Teller matrix element of tritium decay in model
calculations using trinucleon wave functions from these interactions. A
thorough analysis of the ambiguities that this procedure introduces in
evaluating the two-body current contribution to the pp capture is given. Its
inherent model dependence is in fact found to be very weak. The overlap
integral for the pp capture is predicted to be in the range
7.05--7.06, including the axial two-body current contribution, for all
interactions considered.Comment: 17 pages RevTeX (twocolumn), 5 postscript figure
Tensor polarization in elastic electron-deuteron scattering in the momentum transfer range 3.8â€Qâ€4.6 fm-1
The tensor polarization of the recoil deuteron in elastic electron-deuteron scattering has been measured at the Bates Linear Accelerator Center at three values of four-momentum transfer Q=3.78, 4.22, and 4.62 fm-1, corresponding to incident electron energies of 653, 755, and 853 MeV. The scattered electrons and the recoil deuterons were detected in coincidence. The recoil deuterons were transported to a liquid hydrogen target to undergo a second scattering. The angular distribution of the dâ-p scattering was measured using a polarimeter. The polarimeter was calibrated in an auxiliary experiment using a polarized deuteron beam at the Laboratoire National Saturne. A Monte Carlo procedure was used to generate interpolated calibration data because the energy spread in the deuteron energies in the Bates experiment spanned the range of deuteron energies in the calibration experiment. The extracted values of t20 are compared to predictions of different theoretical models of the electromagnetic form factors of the deuteron: nonrelativistic and relativistic nucleon-meson dynamics, Skyrme model, quark models, and perturbative quantum chromodynamics. Along with the world data the structure functions A(Q) and B(Q) are used to separate the charge monopole and charge quadrupole form factors of the deuteron. A node in the charge monopole form factor is observed at Q=4.39±0.16 fm-1
Measurement of tensor polarization in elastic electron-deuteron scattering in the momentum-transfer range 3.8â€qâ€4.6 fm-1
The tensor polarization t20 of the recoil deuteron in elastic e-d scattering has been measured for three values of four-momentum transfer, q=3.78, 4.22, and 4.62 fm-1. The data have been used to locate the first node in the charge monopole form factor of the deuteron at q=4.39±0.16 fm-1. The results for t20 are in reasonable agreement with expectations based on the nucleon-meson description of nuclear dynamic
Perturbative Heavy Quark Fragmentation Function through O(alpha_s^2)
We derive the initial condition for the perturbative fragmentation function
of a heavy quark through order O(alpha_s^2) in the MS-bar scheme. This initial
condition is useful for computing heavy quark (or lepton, in case of QED)
energy distributions from calculations with massless partons. In addition, the
initial condition at O(alpha_s^2) can be used to resum collinear logarithms
ln(Q^2/m^2) in heavy quark energy spectrum with next-to-next-to-leading
logarithmic accuracy by solving the DGLAP equation.Comment: 14 pages, uses axodraw.sty; minor clarifications in the text;
Fig(1,2) corrected; references adde
An accurate nucleon-nucleon potential with charge-independence breaking
We present a new high-quality nucleon-nucleon potential with explicit charge
dependence and charge asymmetry, which we designate Argonne . The model
has a charge-independent part with fourteen operator components that is an
updated version of the Argonne potential. Three additional
charge-dependent and one charge-asymmetric operators are added, along with a
complete electromagnetic interaction. The potential has been fit directly to
the Nijmegen and scattering data base, low-energy scattering
parameters, and deuteron binding energy. With 40 adjustable parameters it gives
a per datum of 1.09 for 4301 and data in the range 0--350
MeV.Comment: 36 pages, PHY-7742-TH-9