Measurement of np elastic scattering at high energies and very small momentum transfers

The np elastic differential cross section has been measured for incident neutron momenta 100–400 GeV/c in the |t| range 6 · 10^?6 ? 5 · 10^?1 (GeV/c)². The np data of this experiment provide a first direct measurement of the hadronic amplitude for |t| < 10^?2 (GeV/c)², which is consistent with the extrapolations from higher |t| values. Our data for |t| < 10^?4 (GeV/c)² are consistent with a rise which can be attributed to Schwinger scattering, caused by the interaction of the neutron magnetic moment with the proton.     

Diffractive one-pion production in the αp → αX process at Pα = 7.0 GeV/c

Inclusive coherent proton dissociation on helium has been measured for a missing mass near the threshold of one-pion production, in the |t| range 0.05–1.6 (GeV/c)² and at an alpha incident momentum of 7.0 GeV/c. A strong t-slope dependence of the cross section at |t| ? 0.2 (GeV/c)² is followed at larger |t| by a less structured distribution. Data were analyzed using the Glauber-Margolis formula and by assuming a peripheral elementary diffraction amplitude for the production process.     

Measurement of high momentum transfer π−p → π0n at 5.9 GeV/c

The differential cross section for π^?p → π⁰n has been measured in the t range 1.8 ? |t| ? 8.2 (GeV/c)² by a counter-spark chamber experiment detecting the neutron and both π⁰ decay photons. A broad minimum was found, centered at |t| = 5.2 (GeV/c)².     

Calculation of the t2g antibonding molecular orbital in |VF6|4, comparison with E.S.R. investigations on KZnF3: V2+

Using the L.C.A.O.-M.O. framework we have calculated the coefficient λ_π which defines the t_2g antibonding orbital of the |VF₆|^4? cluster in the KZnF₃ host lattice, for the ⁴A_2g ground state. An approximate Hamiltonian, analogous to the one early used by Sugano and Shulman for |NiF₆|^4?, gives a good agreement between the calculation and the estimation of λ_π from E.S.R. measurements.     

Impact parameter analysis of the reaction π−p→pπ+π−π− at 9 and 12 GeV/c with very fast secondary proton

The results on the impact parameter for the reactions π^?p→pπ⁺π^?π^?, pK⁺K^?π^?, with a fast secondary forward proton are given at 9 and 12 GeV/c. For the reaction π^?p→pπ⁺π^?π^? our results corresponding to the small |u| region (|u| < 1 GeV²) are compared to the existing data for the small |t| region. We show that small |u| events are more central than small |t| events.     

The pomeron in elastic meson-baryon scattering

We show that a pomeron (P) trajectory with α_P(t) ≈ 1.07 + 0.22t provides a simple and satisfactory fit to π^±p and K^±p elastic scattering data (as well as pp and $\text{p}$p considered in an earlier publication) for |t| < 1.2 GeV², including the rising total cross sections. The destructive term needed to explain the diffraction minimum in pp may be explained as a weak P ? P cut effect provided that the Gribov vertices are given suitable structure, and the prediction is then made that similar minima should be observed in meson-baryon scattering at FNAL somewhere in the region 1.5 < |t| < 2.5 GeV². The P ? P cut does not seem to be related (at least directly) to the unitarization effects which must eventually make σ_tot ～ log²s (but not until s > 10⁸GeV²). Thus the “effective” J-plane singularity structure, at currently available energies seems to be much simpler than it can be asymptotically.     

Elastic pp scattering in the cern sps energy region

The pronounced dip-bump structure with a sharp minimum at |t| = 1.5 (GeV/c)², recently observed in elastic $\text{p}$p scattering at P_L = 50 GeV/c at the CERN SPS, is explained by the quark multiple scattering model with a realistic wavefunction for the proton and the antiproton. It is predicted that a second dip will appear around |t| = 7 (GeV/c)² at P_L = 50 GeV/ c and at higher energies.     

Measurements of elastic scattering in alpha-alpha and alpha-proton collisions at the CERN intersecting storage rings

We measured the elastic scattering of $\text{αα}\text{at}\text{s}\text{= 126}\text{GeV}$ and of αp at $\text{s}\text{= 89}\text{GeV}$. For αα, the differential cross section dσ/dt has a diffractive pattern minima at |t| = 0.10 and 0.38 GeV². At small |t| = 0.05?0.07 GeV², this cross section behaves like exp[(100 ± 10) t]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section α_tot(αα) = 250 ± 50 mb and an integrated elastic cross section σ_e1(αα) = 45 ± mb. Another method of estimating σ_tot(αα), based on measuring the interaction rate, yielded 295 ± 40 mb. For αp, dσ/dt has aminimum at |t| = 0.20 GeV², and for 0.05 < |t| < 0.18 GeV² behaves like exp[(41 ± 2) t]. Extrapolating this slope to |t| = 0, we found σ_tot(αp) = 130 ± 20 and σ_e1(αp) = 20 ± 4mb. Results on pp elastic scattering at $\text{s}\text{= 63}\text{GeV}$ agree with previous ISR experiments.     

Radiation of electromagnetic waves by a dipole in an external uniform electrostatic field

Exact solution for the electromagnetic field densities E and H of a dipole of uniformly accelerated point-charges with identical masses is discussed. It is shown that, for any fixed time t and a large distance R between the center of the dipole and the fieldpoint, |E| ~ R ^?4, |H| ~ R ^?5, while for large c|t| ~ R, |E| ~ |H| ~1/R as in spherical electromagnetic waves. Nevertheless, any irreversible radiation of electromagnetic waves is absent since the wave zone does not exist.     

Helmholtz transceiver array for improving the |<Emphasis Type="Italic">B</Emphasis><Subscript>1</Subscript>|-field homogeneity at 7-T magnetic resonance imaging

A 16-channel transceiver radiofrequency (RF) array using Helmholtz coils was designed to improve the RF transmission |B ₁ ⁺ |-field homogeneity for human brain magnetic resonance imaging (MRI) at 7 T. A numerical simulation of the proposed Helmholtz transceiver array was performed using the finite-difference time-domain method—the subset of the finite-element method simulation. The simulation results of proposed 16-channel Helmholtz transceiver array were compared with the generally used rectangular transceiver array in term of their |B ₁ ⁺ |-field and specific absorption rate (SAR). The simulation of each single element in 16-channel Helmholtz and rectangular transceiver arrays was compared using water phantom in term of their magnetic flux |B ₁| homogeneity for the full width at half maximum. From the simulation results, the proposed 16-channel Helmholtz transceiver array configuration offers superior |B ₁ ⁺ |-field homogeneity and low SAR at 7 T. These modifications to the coil geometries of the transceiver array coil could be applied to a 7-T MRI, and also extended to increase the homogenous coverage on |B ₁ ⁺ |field with low SAR.     

The experimental study of Ba 6pjnk |M| = 0, 1 autoionizing series

The spectra of the Ba 6pnk autoionizing Stark states with |M| = 0, 1, converging to the 6p_1/2⁺ and 6p_3/2⁺ ionization thresholds, are measured as a function of the electric field strength F. Several 6p_jnk Stark manifolds with n = 13–15 have been systematically studied in order to explore their characteristics of configuration interaction. Experimental results are analyzed by fitting them to the Lorentzian profile, from which the positions and widths are determined. Different spectroscopic properties between the Ba 6p_1/2nk and 6p_3/2nk autoionizing Stark states are investigated. Comparison between the Ba 6p_jnk autoionizing Stark states with |M| = 0 and those with |M| = 1 are made.     

Study off o (995) resonance in the π0π0 decay channel

A high-statistics study of the π⁰π⁰-system produced in the π^- p→π⁰π⁰ n reaction at 38GeV/c has been carried out at the IHEP accelerator using the GAMS-2000 multiphoton spectrometer. A partial-wave analysis which includesS, D ₀, D_? andD ₊ waves has been performed in the |t|-range up to 1 (GeV/c)². TheS ^*/f ₀(980) resonance is seen as a dip in theS-wave amplitude at small |t|. A distinct peak with a mass of 997±5MeV and a width of 48±10MeV is observed in theS-wave at |t|>0.3 (GeV/c)². The production cross sections are measured.     

Channel-combination method for phase-based |B1+| mapping techniques

PurposeThe aim of this study was to propose a channel combination method for |B₁⁺| mapping methods using phase difference to reconstruct |B₁⁺| map.Theory and methodsPhase-based |B₁⁺| mapping methods commonly consider the phase difference of two scans to measure |B₁⁺|. Multiple receiver coils acquire a number of images and the phase difference at each channel is theoretically the same in the absence of noise. Affected by noise, phase difference is approximately governed by Gaussian distribution. Considering data from all channels as samples, estimation can be achieved by maximum likelihood method. With this method, all phase differences at each channel are combined into one. In this study, the proposed method is applied with Bloch-Siegert shift |B₁⁺| mapping method. Simulations are performed to illustrate the phase difference distribution and demonstrate the feasibility and facility of the proposed method. Phantom and vivo experiments are carried out at 1.5 T scanner equipped with 8-channel receiver coil. In all experiments, the proposed method is compared with weighted averaging (WA) method.ResultsSimulations revealed appropriateness of approximating the distribution of phase difference to Gaussian distribution. Compared with WA method, the proposed method reduces errors of |B₁⁺| calculation. Phantom and vivo experiments provide further validation.ConclusionConsidering phase noise distribution, the proposed method achieves channel combination by finding the estimation from data acquired by multiple receivers coil. The proposed method reduces |B₁⁺| reconstruction errors caused by noise.     

On new predictions of the vector-meson dominance model for the reactions πN → ϱ0N and γN → πN

It is shown that the assumption of pole vector-meson dominance for the Ball invariant amplitude having a π-meson pole is sufficient for reproducing the longitudinal amplitude of ?⁰-production by the photoproduction amplitude at |t| < 0.1 (GeV/c)². The strong k²-dependence of the Ball invariant amplitude without the π-meson pole has been found by the deviations of theoretical predictions obtained in the VDM framework for the longitudinal ?⁰-production amplitude from the experimental data in the region |t| > 0.1 (GeV/c)². A natural explanation of the k²-dependence in the one-pion exchange model with absorption is given. The problem of A₂-exchange is discussed.     

| m | Partial wave treatment for two-dimensional Coulomb-scattering and Regge pole

The symmetry and |m| partial-wave analysis for two-dimensional (2D) Coulomb-scattering is investigated. As a function of energyE, the |m| partial-wave scattering amplitudef _|m|(θ) is analytically continuated to the, negativeE (complexk) plane, and it is found that the bound state energy eigenvalues (E<0) are just located at the poles off _|m|(θ) on the positive imaginaryk axis as is expected. In addition, as a function of |m|,f _|m|(θ) is analytically continuated to the complex |m| plane, the bound state energy eigenvalues are just located at the poles off _|m|(θ) on the positive real |m| axis.     

Polarization in proton-proton elastic scattering at 10, 14 and 17.5 GeV/c

Data on the polarization parameter in pp elastic scattering in the |t|-range from ∼0.1 to ∼ 2.9 (GeV/c)² and at 10, 14 and 17.5 GeV/c are presented.     

Study of K−p→K1(890)n at 13 GeV

The results of a wire chamber spectrometer experiment studying $\text{K}$¹ (890) production in the reaction K^?p→ K^?π⁺n at 13 GeV are presented. Strong forward structure is observed for |t|< m²_π in the s-channel density matrix elements and differential cross section. These features are similar to those observed in π^?p→?⁰n data and are characteristics of π exchange. In contrast in the intermediate, |t| ～ 0.2 GeV², and large momentum transfer regions $\text{K}$¹ (890) production is demonstrated by the natural parity ??A₂ exchange contribution.     

Polarization in charge exchange reaction π−+p→π0+n at 40 GeV/c for the 4-momentum transfer range 0<|t|<2 (GeV/c)2

The results on measuring polarization in charge exchange reaction π^?+p→π⁰+n at 40 GeV/c are presented for the 4-momentum transfer range from 0 up to 2 (GeV/c)². At |t|≦0.4 (GeV/c)² the polarization has a positive sign. In the “crossover” region of π^± elastic scattering a possible minimum in the polarization behaviour has been seen for the first time. the polarization is zero within the statistical accuracy near this point. In the “deep” region of the charge-exchange differential cross-section the polarization has a negative sign. The presented data are not in agreement with the modern theoretical models.