119883715
Negative pion capture on 12C with emission of neutron-proton pairs
Abstract Energy and angle measurements of neutron-proton pairs emitted after π − capture in 12 C have been made. The data are in partial agreement with several theories. Some evidence indicates that limits on the short-range correlation parameters might be determined from the nn/np ratio at backward angles.
125435973
Reaction Ni-58 (pi+, p p) at T(pi+) = 160-MeV
120631837
A bifilar helical multiware proportional chamber for position sensitive detection of minimum ionizing particles
Abstract A new type of multiware proportional chamber with a helical cathode for delay line readout has been developed and studied in detail. It gives cathode delay line pulses nearly as large as the anode pulses, and hence is well-suited for minimum ionizing particles. Measurements on such a chamber yielded spatial resolution better than 0.33 mm fwhm for 90 Sr β particles, a resolving time less than 30 ns, and maximum counting rate greater than 2 MHz. The most probable pulse height induced on the delay line by minimum ionizing particles in this chamber is approximately 8 mV.
111344904
Beam test of prototype 18 cm silicon-strip detectors with high speed electronics
A prototype silicon microstrip detector for the GEM general purpose detector proposed for the Super Collider was assembled and tested in the laboratory with radioactive sources and an IR-laser, and at SLAC in a 25 GeV electron beam. The system was designed for performance in the GEM environment: 60 MHz bunch crossing at 10/sup 33/ luminosity with inner barrel occupancies of 0.16%. Signals from the strips were amplified by custom designed high-speed, low-power, low-noise, low-mass, integrated microelectronics The mechanical design of the GEM tracker motivated the selection of long (18 cm) strip lengths (achieved by wire-bonding three 6 cm long detectors). Evaluation of the test beam and laboratory results demonstrate the feasibility of this approach.
30243209
Muon-neutrino carbon charged-current interaction near the muon threshold.
A measurement of the muon-neutrino carbon charged-current cross section, {sup 12}C({nu}{sub {mu}},{mu}{sup {minus}}){ital X}, was performed using the in-flight pion-decay neutrino source at the LAMPF accelerator. At an average interacting neutrino energy of 202 MeV an inclusive cross section of (15.9{plus minus}2.6{plus minus}3.7){times}10{sup {minus}39} cm{sup 2} was measured. This value is in best agreement with the Fermi-gas model and is in disagreement with a previous experiment and subsequent calculations that yielded substantially lower cross sections. However, the muon energy spectrum shows a marked depletion of events at high energies compared to the Fermi-gas model. From a small sample of events in which the final-state nucleus was in the ground state of {sup 12}N, a cross section for the reaction {sup 12}C({nu}{sub {mu}},{mu}{sup {minus}}){sup 12}N(g.s.) of (1.7{plus minus}0.8{plus minus}0.3){times}10{sup {minus}39} cm{sup 2} or about 11{plus minus}5 % of the total event rate was obtained.
124265140
Low-energy neutron shielding
The attenuation of low-energy neutrons (< 20 MeV) through a 120-cm-thick slab shield of various mixtures of concrete, boron compounds, and water has been investigated. A Monte Carlo code was used to sample the neutron probability distribution and track the neutrons through the shield.
14276849
THE ROLE OF DIAGONALIZATION WITHIN A DIAGONALIZATION/MONTE CARLO SCHEME
We discuss a method called quasi-sparse eigenvector diagonalization which finds the most important basis vectors of the low energy eigenstates of a quantum Hamiltonian. It can operate using any basis, either orthogonal or non-orthogonal, and any sparse Hamiltonian, either Hermitian, non-Hermitian, finite-dimensional, or infinite-dimensional. The method is part of a new computational approach which combines both diagonalization and Monte Carlo techniques.
18663889
Structure and rotations of the Hoyle state.
The excited state of the (12)C nucleus known as the "Hoyle state" constitutes one of the most interesting, difficult, and timely challenges in nuclear physics, as it plays a key role in the production of carbon via fusion of three alpha particles in red giant stars. In this Letter, we present ab initio lattice calculations which unravel the structure of the Hoyle state, along with evidence for a low-lying spin-2 rotational excitation. For the (12)C ground state and the first excited spin-2 state, we find a compact triangular configuration of alpha clusters. For the Hoyle state and the second excited spin-2 state, we find a "bent-arm" or obtuse triangular configuration of alpha clusters. We also calculate the electromagnetic transition rates between the low-lying states of (12)C.
16079959
Renormalization in spherical field theory
Abstract We derive several results concerning non-perturbative renormalization in the spherical field formalism. Using a small set of local counterterms, we are able to remove all ultraviolet divergences in a manner such that the renormalized theory is finite and translationally invariant. As an explicit example we consider massless φ 4 theory in four dimensions.
119296383
Causality constraints for charged particles
In quantum systems with short-range interactions, causality imposes nontrivial constraints on low-energy scattering parameters. We investigate these causality constraints for systems where a long-range Coulomb potential is present in addition to a short-range interaction. The main result is an upper bound for the Coulomb-modified effective range parameter. We discuss the implications of this bound to the effective field theory for nuclear halo systems. In particular, we consider several examples of proton–nucleus and nucleus–nucleus scattering. For the bound-state regime, we find relations for the asymptotic normalization coefficients (ANCs) of nuclear halo states. As an application of these relations, we extract the ANCs of the excited 2+ and 1− states in 16O from α − 12C scattering data.
119222693
Finite volume effects in low-energy neutron–deuteron scattering
We present a lattice calculation of neutron–deuteron scattering at very low energies and investigate in detail the impact of the topological finite-volume corrections. Our calculations are carried out in the framework of pionless effective field theory at leading order in the low-energy expansion. Using lattice sizes and a lattice spacing comparable to those employed in nuclear lattice simulations, we find that the topological volume corrections must be taken into account in order to obtain accurate results for the neutron–deuteron S-wave scattering lengths.