1,223 research outputs found
Global analysis of muon decay measurements
We have performed a global analysis of muon decay measurements to establish
model-independent limits on the space-time structure of the muon decay matrix
element. We find limits on the scalar, vector and tensor coupling of right- and
left-handed muons to right- and left-handed electrons. The limits on those
terms that involve the decay of right-handed muons to left-handed electrons are
more restrictive than in previous global analyses, while the limits on the
other non-standard model interactions are comparable. The value of the Michel
parameter eta found in the global analysis is -0.0036 \pm 0.0069, slightly more
precise than the value found in a more restrictive analysis of a recent
measurement. This has implications for the Fermi coupling constant G_F.Comment: 5 pages, 3 table
Refractive effects in the scattering of loosely bound nuclei
A study of the interaction of loosely bound nuclei 6,7Li at 9 and 19 AMeV
with light targets has been undertaken. With the determination of unambiguous
optical potentials in mind, elastic data for four projectile-target
combinations and one neutron transfer reaction 13C(7Li,8Li)12C have been
measured on a large angular range. The kinematical regime encompasses a region
where the mean field (optical potential) has a marked variation with mass and
energy, but turns out to be sufficiently surface transparent to allow strong
refractive effects to be manifested in elastic scattering data at intermediate
angles. The identified exotic feature, a "plateau" in the angular distributions
at intermediate angles, is fully confirmed in four reaction channels and
interpreted as a pre-rainbow oscillation resulting from the interference of the
barrier and internal barrier farside scattering subamplitudes.Comment: 19 pages, 14 figures, 3 tables to submit to Phys. Rev.
Lambda hyperonic effect on the normal driplines
A generalized mass formula is used to calculate the neutron and proton drip
lines of normal and lambda hypernuclei treating non-strange and strange nuclei
on the same footing. Calculations suggest existence of several bound
hypernuclei whose normal cores are unbound. Addition of Lambda or,
Lambda-Lambda hyperon(s) to a normal nucleus is found to cause shifts of the
neutron and proton driplines from their conventional limits.Comment: 6 pages, 4 tables, 0 figur
Magnetic Field Evolution in Merging Clusters of Galaxies
We present initial results from the first 3-dimensional numerical
magnetohydrodynamical (MHD) simulations of magnetic field evolution in merging
clusters of galaxies. Within the framework of idealized initial conditions
similar to our previous work, we look at the gasdynamics and the magnetic field
evolution during a major merger event in order to examine the suggestion that
shocks and turbulence generated during a cluster/subcluster merger can produce
magnetic field amplification and relativistic particle acceleration and, as
such, may play a role in the formation and evolution of cluster-wide radio
halos. The ICM, as represented by the equations of ideal MHD, is evolved
self-consistently within a changing gravitational potential defined largely by
the collisionless dark matter component represented by an N-body particle
distribution. The MHD equations are solved by the Eulerian, finite-difference
code, ZEUS. The particles are evolved by a standard particle-mesh (PM) code. We
find significant evolution of the magnetic field structure and strength during
two distinct epochs of the merger evolution.Comment: 21 pages, 7 figures, Figure 2 is color postscript. Accepted for
publication in Ap
Nuclear structure beyond the neutron drip line: the lowest energy states in He via their T=5/2 isobaric analogs in Li
The level structure of the very neutron rich and unbound He nucleus has
been the subject of significant experimental and theoretical study. Many recent
works have claimed that the two lowest energy He states exist with spins
and and widths on the order of hundreds of keV.
These findings cannot be reconciled with our contemporary understanding of
nuclear structure. The present work is the first high-resolution study with low
statistical uncertainty of the relevant excitation energy range in the
He system, performed via a search for the T=5/2 isobaric analog states
in Li populated through He+p elastic scattering. The present data show
no indication of any narrow structures. Instead, we find evidence for a broad
state in He located approximately 3 MeV above the neutron
decay threshold
Experimental Validation of the Largest Calculated Isospin-Symmetry-Breaking Effect in a Superallowed Fermi Decay
A precision measurement of the gamma yields following the beta decay of 32Cl
has determined its isobaric analogue branch to be (22.47^{+0.21}_{-0.19})%.
Since it is an almost pure Fermi decay, we can also determine the amount of
isospin-symmetry breaking in this superallowed transition. We find a very large
value, delta_C=5.3(9)%, in agreement with a shell-model calculation. This
result sets a benchmark for isospin-symmetry-breaking calculations and lends
support for similarly-calculated, yet smaller, corrections that are currently
applied to 0+ -> 0+ transitions for tests of the Standard Model
- …