Proton-pion and two- pion correlations in eA interactions

We report here the results on studying of proton-pion and two-pion correlations in eA interactions at 5 GeV. Kinematic correlations were studied as a function of the two-particle opening angle, their momenta and proton multiplicity. The universal properties of correlation functions were found with respect to different particle species. Interferometry method was used to determine the size of the interaction region.     

Asymmetry dependence of proton correlations

A dispersive-optical-model analysis of p+40Ca and p+48Ca interactions has been carried out. The real and imaginary potentials have been constrained from fits to elastic-scattering data, reaction cross sections, and level properties of valence hole states deduced from (e, e' p) data. The surface imaginary potential was found to be larger overall and the gap in this potential on either side of the Fermi energy was found to be smaller for the neutron-rich p+48Ca system. These results imply that protons with energies near the Fermi surface experience larger correlations with increasing asymmetry.     

Cosmic ray results on the A dependence of multiplicity and angular distributions in proton nuclear interactions above 100 GeV

A calorimeter-spark chamber system was used to collect data on several hundred proton-nucleus interactions above 100 GeV using targets of C, Al, Fe, Sn and Pb. The average charged prong multiplicity is found to depend on atomic mass number as 〈n_c〉 = 〈n_c〉(p-p)A^x where x = 0.129 ± 0.004, with the dominant increase in multiplicity occuring in the backward (p-p c.m.) hemisphere. The value of x shows no significant energy dependence.     

On the directional dependence of Bose-Einstein correlations

A simple method to measure the shape of the particle emission region in high energy particle collisions by interferometry is discussed. Results from an application to data on inelasticpp scattering are compared with results based on determinations of the radial extension of the source. Both show that in the c.m.s., the source is elongated in the beam direction.     

Influence of electron correlations on double-capture process in proton helium collisions

The first-order correct-boundary Coulomb–Born distorted-wave approximation is used to study the double-electron capture by protons from the ground-state helium atoms at intermediate and high impact energies. The differential double capture cross sections are obtained as a function of the projectile scattering angle and the total cross sections as a function of the impact energy. In the considered range of impact energy, our calculation shows that although the results are not so sensitive to the static inter-electronic correlations in the initial channel, the strong final-state correlations have a large effect on the magnitudes of the double capture cross sections. The calculated differential and integral cross sections are compared with their available experimental values. The comparison shows a good agreement between the present calculations and the measurements. The comparison of the integral cross sections shows that the present approach is compatible with other theories.     

Effects of the nuclear correlations on the neutrino-oxygen interactions

We perform a calculation of the absolute charged current neutrino-oxygen events rates relevant in the atmospheric neutrino experiments. The inclusive reaction cross-section is split into exclusive channels, which are classified according to the number of Čerenkov rings they produce. The model includes the effects of residual interaction in a RPA scheme with both nucleon-hole and Delta-hole excited states and the effects of (np-nh) excitations (n=2,3). Our result is that although the flavor ratio μ/e remains almost unaffected by the nuclear effects considered here and often neglected in the Monte-Carlo simulations, the absolute events rates are subject to important modifications. Received: 15 January 1999     

Azimuthal dependence of two-particle transverse momentum current correlations

The European Physical Journal C - We present a study on inclusive emissions of a double $$\Lambda _c$$ or of a $$\Lambda _c$$ plus a light-flavored jet system as probe channels in the semi-hard...     

Zero-motion flucton correlations in high-energy proton elastic scattering on40Ca

The 1.04 GeV-proton elastic scattering from⁴⁰Ca is studied in the framework of the coherent density fluctuation model (CDFM). The calculations are carried out in the Glauber theoretical scheme with three different charge densities. It is shown that:i) the account of the flucton correlations leads to results considerably different from those obtained in the independent particle Glauber approach (IPGA);ii) in contrast to the case of IPGA the use of a more realistic density improves the agreement of CDFM-results with the experimental data.     

Invariant mass dependence of particle correlations in π+ p andK + p interactions at 250 GeV/c

We study two- and three-particle correlations as a function of invariant mass. Using data on π⁺ p andK ⁺ p collisions at 250 GeV/c, we compare correlation functions and normalised factorial cumulants for various charge combinations. Strong positive correlations are observed only at small invariant masses. The normalised cumulants for “exotic” [(??), (++)] and “nonexotic” pairs (+?) and triplets decrease in power-like fashion with increasing invariant mass. The mass dependence is not incompatible with the power-law behaviour as expected in a Dual Mueller-Regge framework. Comparison with FRITIOF reveals strong disagreements, which are due to too large production rates of resonances, such as ρ⁰ and η, and the absence of a Bose-Einstein low-mass enhancement in JETSET.

     

Temperature dependence of proton relaxation times in vitro

Accurate measurement of tissue relaxation characteristics is dependent on many factors, including field strength and temperature. The purpose of this study was to evaluate the relationship between sample temperature, viscosity and proton spin-lattice relaxation time (T1) and spin-spin relaxation time (T2). A review of two basic models of relaxation the simple molecular motion model and the fast exchange two state model is given with reference to their thermal dependencies. The temperature dependence for both T1 and T2 was studied on a 0.15 Tesla whole body magnetic resonance imager. Thirteen samples comprising both simple and complex materials were investigated by using a standard spin-echo (SE) technique and a modified Carr-Purcell-Meiboom-Gill (CPMG) multi-echo sequence. A simple linear relationship between T1 and temperature was observed for all samples over the range of 20 degrees C to 50 degrees C. There is an inverse relationship between viscosity and T1 and T2. A quantity called the temperature dependence coefficient (TDC) is introduced and defined as the percent rate of change of the proton relaxation time referenced to a specific temperature. The large TDC found for T1 values, e.g. 2.37%/degrees C for CuSO4 solutions and 3.59%/degrees C for light vegetable oils at 22 degrees C, indicates that a temperature correction should be made when comparing in-vivo and in-vitro T1 times. The T2 temperature dependence is relatively small.     

Temperature dependence of F-centre hyperfine interactions

We report the temperature dependence of F-centre Isotropic hyperfine energies for the first shells of KCl, KBr, NaCl, LiF and Lid, and the second shell of KCl. In all cases at least 30 ENDOR data points were taken between 1.3° and 300°K, and the Fermi contact energies were found to adhere closely to a curve of the form a(T) = A + B coth (C/T).The effects of pure lattice expansion may be removed with the aid of high pressure ENDOR data. The remaining temperature dependence can be explained in terms of a configuration co-ordinate model, with the F-electron interacting with a single effective mode of lattice vibration.     

The Q-dependence of the generalised Gerasimov-Drell-Hearn integral for the deuteron,proton and neutron

The Gerasimov-Drell-Hearn (GDH) sum rule connects the anomalous contribution to the magnetic moment of the target nucleus with an energy-weighted integral of the difference of the helicity-dependent photoabsorption cross sections. Originally conceived for real photons, the GDH integral can be generalised to the case of photons with virtuality Q². For spin-1/2 targets such as the nucleon, it then represents the non-perturbative limit of the first moment of the spin structure function g ₁ (x,Q ² ) in deep inelastic scattering (DIS). The data collected by HERMES with a deuterium target are presented together with a re-analysis of previous measurements on the proton. This provides an unprecedented and complete measurement of the generalised GDH integral for photon-virtuality ranging over 1.2<Q ² <12.0 GeV² and for photon-nucleon invariant mass squared W² ranging over 1<W ² <45 GeV², thus covering simultaneously the nucleon-resonance and the deep inelastic scattering regions. These data allow the study of the Q²-dependence of the full GDH integral, which is sensitive to both the Q²-evolution of the resonance form factors and contributions of higher twist. The contribution of the nucleon-resonance region is seen to decrease rapidly with increasing Q². The DIS contribution is sizeable over the full measured range, even down to the lowest measured Q². As expected, at higher Q² the data are found to be in agreement with previous measurements of the first moment of g₁. From data on the deuteron and proton, the GDH integral for the neutron has been derived and the proton-neutron difference evaluated. This difference is found to satisfy the fundamental Bjorken sum rule at Q ² = 5 GeV². Received: 20 October 2002 / Published online: 15 January 2003     

Regge oscillations in integral cross sections for proton impact on atomic hydrogen

The integral cross sections for elastic scattering and spin exchange for proton impact on atomic hydrogen show several oscillations in the energy range 0.01-1.0 eV that cannot be associated with resonances or the glory effect. A complex angular momentum analysis using computed Regge trajectories shows that each peak of the oscillatory structure is predominantly associated with at most three trajectories. In this way, the peaks are related to the L=0 bound states of H+ 2. The complex angular momentum theory for integral cross sections that we introduce shows that such oscillations are a general feature of potential scattering.