121101159
Effect of a preshower detector on calorimetry performance
Abstract Test beam results obtained with a preshower detector in a SDC calorimetry configuration are presented. The benefits of independently instrumenting the first scintillating tile of each tower of the tile/fiber electromagnetic calorimeter, forming the analogue of the “Massless Gap” in LAr calorimeters, are demonstrated. Electron and pion data were taken with a calorimeter configured with one or two radiation lengths of inert material in front, a scintillating fiber preshower detector, a tile/fiber electromagnetic calorimeter, a shower maximum detector, and a tile/fiber hadron calorimeter. The energy deposited in the scintillating fibers of the preshower detector was summed to simulate the preshower energy that would be detected by the first scintillating tile of an EMC tower. The data were collected in the MP9 beam line at Fermilab during the Summer and Fall of 1991. The relative degradation in electromagnetic energy resolution due to the inert material in front of the electromagnetic calorimeter was measured. The resolution is improved by adding in the properly weighted preshower energy. The charged pion rejection versus electron acceptance is presented for combined cuts using the electromagnetic and hadronic calorimeters, with the energy deposited in the preshower and shower maximum detectors. We show that, even after calorimetric and shower maximum cuts, the pion rejection is further improved by using the preshower energy.
120345656
Evidence for the noneikonal effects in the tensor and vector analyzing powers in p-d elastic scattering at 800 MeV☆
Abstract Deuteron tensor and vector analyzing powers have been measured for the first time in p- d elastic scattering at 800 MeV proton laboratory energy for a - t range between 0.032 and 1.038 (GeV/ c ) 2 . The data provide a very sensitive test of the multiple scattering theory at intermediate energies. The inclusion of the noneikonal correction in the Glauber diffraction theory is essential in the description of the data, especially for -t ⪆0.2 (GeV/ c 2 ), where discrepancies of up to 150% are observed with the theory based on the eikonal approximation.
119819008
Large angle elastic and inelastic scattering of protons from Ca 40 at 800 MeV
Measurements are reported for the elastic and inelastic scattering of 800 MeV protons from $^{40}\mathrm{Ca}$. Differential cross sections were measured out to 42\ifmmode^\circ\else\textdegree\fi{} while analyzing powers were obtained out to 30\ifmmode^\circ\else\textdegree\fi{}. The angular distributions are diffractive in character at all angles. Theoretical analysis of the data was carried out in the framework of the diffraction multiple scattering theory. The following results were obtained: (i) Diffraction multiple scattering theory reproduces the data qualitatively out to the large momentum transfers. (ii) For the ground state density distribution ${〈{{r}_{p}}^{2}〉}^{\frac{1}{2}}\ensuremath{-}{〈{{r}_{n}}^{2}〉}^{\frac{1}{2}}=0.142\ifmmode\pm\else\textpm\fi{}0.075$ fm is obtained and the analysis favors the value of the correlation length ${\ensuremath{\xi}}_{c}=\ensuremath{-}0.5$ fm. (iii) The excitation of the lowest-lying collective states (${3}^{\ensuremath{-}}$, ${5}^{\ensuremath{-}}$, ${2}^{+}$) was analyzed using one-phonon excitation macroscopic parameters. The values of the ${\ensuremath{\beta}}_{2}$, ${\ensuremath{\beta}}_{3}$, ${\ensuremath{\beta}}_{5}$ parameters obtained agree quantitatively with lower energy ($p$,${p}^{\ensuremath{'}}$) scattering results.
120198608
Differential cross sections and analyzing powers for pp elastic scattering at 1. 46 GeV/c in the Coulomb-nuclear interference region
Differential cross sections sigma(theta) and analyzing powers A(theta) for pp elastic scattering have been measured in the Coulomb-nuclear interference region at 800 MeV. The measurements, which extend down to 0.5 deg in the laboratory, have been analyzed to deduce the zero-degree pp scattering amplitudes. The ratio rho of the real to imaginary parts of the spin-independent amplitude was found to be -0.04 +- 0.04; the contribution of the double-spin-flip amplitudes to sigma(0) was found to be 0.16 +- 0.03 times that of the spin-independent amplitude; while the ratios of the imaginary and real parts of the single spin-flip amplitude to sintheta were found to be 0.74 +- 0.04 and -0.03 +- 0.08 fm, respectively. Except for the last, these experimental values agree with the predictions of forward dispersion relations and phase shift analyses.
123099584
Cross sections and analyzing powers in the (p,d) reaction around 500 MeV
Abstract Cross sections and analyzing powers for the (p,d) reaction on 12 C, 13 C and 28 Si are measured around 500 MeV. DWBA calculations are found to reproduce the main features of the (p,d) data, when proton potentials are used which give strong oscillations in the (p,p) analyzing powers as required by the elastic data. Damping of the nuclear interior contribution is unimportant at this energy.
118411966
Elastic Scattering of Positive Kaons on Polarized Deuterons at 1.5 Gev/c.
30744353
Reconstruction of the deceleration parameter and the equation of state of dark energy
The new 182 gold supernova Ia data, the baryon acoustic oscillation measurement and the shift parameter determined from the Sloan Digital Sky Survey, and the three-year Wilkinson Microwave Anisotropy Probe data are combined to reconstruct the dark energy equation of state parameter $w(z)$ and the deceleration parameter $q(z)$. We find that the strongest evidence of acceleration happens around the redshift $z\ensuremath{\sim}0.2$ and the stringent constraints on $w(z)$ lie in the redshift range $z\ensuremath{\sim}0.2\char21{}0.5$. At the sweet spot, $\ensuremath{-}1.2lw(z)l\ensuremath{-}0.6$ for the dark energy parametrization $w(z)={w}_{0}+{w}_{a}z/(1+z{)}^{2}$ at the $3\ensuremath{\sigma}$ confidence level. The transition redshift ${z}_{t}$ when the Universe underwent the transition from deceleration to acceleration is derived to be ${z}_{t}={0.36}_{\ensuremath{-}0.08}^{+0.23}$. The combined data is also applied to find out the geometry of the Universe, and we find that at the $3\ensuremath{\sigma}$ confidence level, $|{\ensuremath{\Omega}}_{k}|\ensuremath{\lesssim}0.05$ for the simple one-parameter dark energy model, and $\ensuremath{-}0.064l{\ensuremath{\Omega}}_{k}l0.028$ for the $\ensuremath{\Lambda}\mathrm{CDM}$ model.
14902021
Kink stability of isothermal spherical self-similar flow revisited
The problem of kink stability of isothermal spherical self-similar flow in newtonian gravity is revisited. Using distribution theory we first develop a general formula of perturbations, linear or non-linear, which consists of three sets of differential equations, one in each side of the sonic line and the other along it. By solving the equations along the sonic line we find explicitly the spectrum, k, of the perturbations, whereby we obtain the stability criterion for the self-similar solutions. When the solutions are smoothly across the sonic line, our results reduce to those of Ori and Piran. To show such obtained perturbations can be matched to the ones in the regions outside the sonic line, we study the linear perturbations in the external region of the sonic line (the ones in the internal region are identically zero), by taking the solutions obtained along the line as the boundary conditions. After properly imposing other boundary conditions at spatial infinity, we are able to show that linear perturbations, satisfying all the boundary conditions, exist and do not impose any additional conditions on k. As a result, the complete treatment of perturbations in the whole spacetime does not alter the spectrum obtained by considering the perturbations only along the sonic line.
118669175
Bounded excursion stable gravastars and black holes
Dynamical models of prototype gravastars were constructed in order to study their stability. The models are the Visser–Wiltshire three-layer gravastars, in which an infinitely thin spherical shell of stiff fluid divides the whole spacetime into two regions, where the internal region is de Sitter, and the external one is Schwarzschild. It is found that in some cases the models represent the 'bounded excursion' stable gravastars, where the thin shell is oscillating between two finite radii, while in other cases they collapse until the formation of black holes occurs. In the phase space, the region for the 'bounded excursion' gravastars is very small in comparison to that of black holes, but not empty. Therefore, although the possibility of the existence of gravastars cannot be excluded from such dynamical models, our results indicate that, even if gravastars do indeed exist, that does not exclude the possibility of the existence of black holes.
15078923
Dark Energy and Cosmic Curvature: Monte Carlo Markov Chain Approach
We use the Monte Carlo Markov chain method to explore the dark energy properties and the cosmic curvature by fitting two popular dark energy parameterizations to the observational data. The new 182 gold Type Ia supernova data and the ESSENCE data both give good constraints on the dark energy parameters and the cosmic curvature for the dark energy model w0 + waz/(1 + z) . The cosmic curvature is found to be | Ωk| 0.03. For the dark energy model w0 + waz/(1 + z)2, the ESSENCE data gives better constraints on the cosmic curvature, and we get | Ωk| ≤ 0.02.
199678292
Linear perturbations of cosmological models in the Horava-Lifshitz theory of gravity without detailed balance