30104157
Chiral effective field theory on the lattice at next-to-leading order
Abstract.We study nucleon-nucleon scattering on the lattice at next-to-leading order in chiral effective field theory. We determine phase shifts and mixing angles from the properties of two-nucleon standing waves induced by a hard spherical wall in the center-of-mass frame. At fixed lattice spacing we test model independence of the low-energy effective theory by computing next-to-leading-order corrections for two different leading-order lattice actions. The first leading-order action includes instantaneous one-pion exchange and same-site contact interactions. The second leading-order action includes instantaneous one-pion exchange and Gaussian-smeared interactions. We find that in each case the results at next-to-leading order are accurate up to corrections expected at higher order.
15307965
The role of Monte Carlo within a diagonalization/Monte Carlo scheme
Abstract We review the method of stochastic error correction which eliminates the truncation error associated with any subspace diagonalization. Monte Carlo sampling is used to compute the contribution of the remaining basis vectors not included in the initial diagonalization. The method is part of a new approach to computational quantum physics which combines both diagonalization and Monte Carlo techniques.
17596274
Mesons with a Light Quark-Antiquark Pair and the Bethe-Salpeter Equation
The light quark-antiquark scattering Green's function is considered near a meson resonance peak. The Bethe-Salpeter equation is used to write formal expressions for the resonance width/mass ratio. Arguments are made concerning to what extent this ratio can be calculated perturbatively, and an upper bound is placed on the growth of this ratio as a function of radial excitation. Certain mesons and their radial excitations are considered, as well as the more general issue of classifying mesons in the quark model.
118374917
Lattice calculations for A = 3 , 4, 6, 12 nuclei using chiral effective field theory
Abstract.We present lattice calculations for the ground-state energies of tritium, helium-3, helium-4, lithium-6, and carbon-12 nuclei. Our results were previously summarized in a letter publication. This paper provides full details of the calculations. We include isospin-breaking, Coulomb effects, and interactions up to next-to-next-to-leading order in chiral effective field theory.
119868800
Ab initio lattice results for Fermi polarons in two and three dimensions
We investigate the attractive Fermi polaron problem in two and three dimensions using non-perturbative Monte Carlo simulations. We introduce a new Monte Carlo algorithm called the impurity lattice Monte Carlo method. This algorithm samples the path integral in a computationally efficient manner and has only small sign oscillations for systems with a single impurity. To benchmark the method, we calculate the universal polaron energy in three dimensions in the scale-invariant unitarity limit and find agreement with published results. We then present the first fully non-perturbative calculations of the polaron energy in two dimensions in the limit of zero range interactions. We find evidence for a smooth crossover transition from a fermionic quasiparticle to a molecular state as a function of interaction strength with significant mixing between the two descriptions in the crossover region.
125749692
Nuclear lattice simulations
We review recent progress on nuclear lattice simulations using chiral effective field theory. We discuss lattice results for dilute neutron matter at next-to-leading order, three-body forces at next-to-next-to- leading order, isospin-breaking and Coulomb effects, and the binding energy of light nuclei.
123008932
The response of drift tubes to variations in wire diameter and gas filling
Abstract A systematic study of the response of single-wire drift tubes to variations in the wire diameter and gas fillings has been conducted. Gas gain as a function of applied voltage and pulse-shape characteristics were measured for both the proportional and streamer modes. Argon gas fillings with mixtures of ethane, methane, isobutane, and carbon dioxide were studied. Ethanol and isopropyl alcohol admixtures were added to determine effects on stability. Additional studies were conducted on nonstandard gas mixtures such as Freon and neon fillings, and “magic gas”. Wire diameters included in the study were 20, 25, 50, and 100 μm. The results demonstrate that streamer operation can be achieved with most gases and wire diameters. However, in most cases, admixtures of alcohol were necessary to obtain adequate streamer mode plateaus for the smaller diameter wires.
123479705
Design and construction of double-sided silicon ladders for the L3 microvertex detector
Abstract The techniques used in the construction of the double-sided ladders for the L3 Silicon Microvertex Detector (SMD) are presented. The detector consists of two cylindrical layers, each of 12 ladders, with double-sided silicon detectors which provide r -phi and z coordinates measurements. This description includes ladder mechanical design and the assembly. A novel solution to readout the z -coordinates is presented. It optimizes very effectively the removal of heat generated by the readout electronics and minimizes the radiation length in the central region. Some results from the survey of the individual ladders are also discussed.
89609083
Evidence for a New Phase of Solid He-3
)Permanent address: Faculte des Sciences, Orsay, France. See, for exaxnple, I. Prigogine, Non Equi/ibrinm Statistica/ Mechanics (Wiley, New York, 1962); P. Resibois, in-Many Pmticle Physics, edited by K. Meeron (Gordon and Breach, New York, 1966). J. Van der Waals, Dissertation, University of Leiden, 1873 (unpublished) . See M. Kac, G. Uhlenbeck, and P. Hemmer, J. Math. Phys. 4, 216, 229 (1963), and 5, 60 (1964); J. Lebowitz, G. Steli, and S. Baer, J. Math. Phys. (N.Y.) 4, 1282 (1965). See K. Kawasaki, Progr. Theor. Phys. 41, 1190 (1969), snd references quoted therein. ~H. Mori, Progr. Theor. Phys. 28, 763 (1962}. P. Resibois, J. Chem. Phys. 41, 2979 (1964). P. Resibois, J. Stat. Phys. 2, 21 (1970). J. Dorfman and E. Cohen, Phys. Rev. Lett. 25, 1257 (1970). L. Kadanoff and J. Swift, Phys. Rev. 166, 89 (1968). M. Ernst, E. Hauge, and J. Van Leeuwen, Phys. Rev. Lett. 25, 1254 (1970), and Phys. Rev. A 4, 2055 (1971). "B.Alder and T. Wainwright, Phys. Rev. A 1, 18 (1970); see also Refs. 8 and 10; and Y. Pomeau, to be published.
121875662
Correlated neutron-deuteron and neutron-triton emission after pion capture on 12C
Abstract Energy and angle measurements of neutron-deuteron and neutron-triton pairs emitted following negative-pion capture on 12 C have been made. Strong 180° correlation is observed in the angular distributions of both types of pairs, indicating substantial absorption by clusters in the 12 C nucleus.
2385881
The Coincidence of Nuclear Star Clusters and Active Galactic Nuclei
We study galaxies that host both nuclear star clusters and AGNs, implying the presence of a massive black hole. We select a sample of 176 galaxies with previously detected nuclear star clusters that range from ellipticals to late-type spirals. We search for AGNs in this sample using optical spectroscopy and archival radio and X-ray data. We find galaxies of all Hubble types and with a wide range of masses (109-1011 M☉) hosting both AGNs and nuclear star clusters. From the optical spectra, we classify 10% of the galaxies as AGN and an additional 15% as composite, indicating a mix of AGN and star formation spectra. The fraction of nucleated galaxies with AGNs increases strongly as a function of galaxy and nuclear star cluster mass. For galaxies with both a nuclear star cluster and a black hole, we find that the masses of these two objects are quite similar. However, nondetections of black holes in Local Group nuclear star clusters show that not all clusters host black holes of similar masses. We discuss the implications of our results for the formation of nuclear star clusters and massive black holes.