Hadronic scaling and ratios of cosmic-ray components in the atmosphere

Using the scaling hypothesis of hadronic inclusive reactions at high energy and data from accelerators we compute ratios of cosmic-ray components in the atmosphere. For the μ⁺/μ^? ratio at sea level we find that the inclusion on nuclear effects results in a better agreement with experimental data. In the case of the (π⁺ + π^?)/p ratio, we predict a value at high energy that is considerably larger than the one usually inferred from lower energy data.     

The n-n S-wave scattering length from the neutron spectra of the reaction π− +d → 2n+γ

We present a measurement of the neutron-neutron S-wave scattering length, a_nn, from an analysis of the neutron energy and angular spectra for the reaction d(π^?, γ)2n. This reaction provides the unique advantage that while all three final-state particles are experimentally detectable, only the neutrons are strongly interacting. The data are analyzed using the treatment of this reaction given by Bander, taking the effects of experimental resolution into account with Monte Carlo techniques. Two independent analyses of 4200 events yield a_nn = ?16.7 ±1.3 fm assuming r_nn = 2.65 fm. This value is in good agreement with calculations of a_nn which assume charge symmetry of the nuclear components of p-p and n-n interactions.     

Mueller-Regge analysis in the central region

Mueller-Regge analysis of inclusive spectra in the central region for fixed p⊥ is carried out from 12 GeV/c to ISR energies. An analysis of the difference between π⁺ and π^? single- particle spectra reveals that both Mueller-Regge energy dependence and factorization are in accord with experiments only in a limited region of moderate value of $\text{p?}$, i.e. $\text{p? ? 0.7}\text{GeV/c}$. This suggests that double Regge exchange is a good approximation only for 0;t∥ and ∥u∥ ? 4 GeV². The K/π ratio calculated on the basis of an additive quark-counting picture is also consistent with experiments inside this region. The P? central vertex determined from ISR data turns out to be much smaller than one would obtain from low energy (12–24 GeV/c) data. The P-M-P exchange contribution to ππ correlations in rapidity thus estimated can explain only a part of observed correlations, which indicates that there should be a large positive contribution from some other effects, such as long range effects and/or Q exchange. The transverse momentum dependence of the P? central vertex also determined from ISR data predicts that the P-?-P exchange contribution to normalized ππ correlations increases as $\text{p}{}_1\text{?}$ and $\text{p}{}_{\mathrm{2?}}$ increase.     

Phase shift analysis of Kp scattering

We have analyzed data on K⁺p elastic scattering at 21 momenta covering the range 0.5–2.5 GeV/c. We present results of three phase shift analyses. One of these is an energy independent accelerated convergence expansion (ACE) analysis in which high partial waves are included through use of conformal mapping as suggested by analytic approximation theory. The other two are an energy independent and an energy smoothed conventional analysis. The ACE method gave, with the same number of parameters, a 20% average improvement in x² as well as more unique phase shift solutions. The high partial waves gave significant contributions to total and inelastic cross sections. The ACE method is also sensitive to the value of g_ΛΣ² = g_KΛN² + g_KΣN²; we have obtained the value g_ΛΣ² = 15.2 ± 2.3.     

Chemical trends for deep antisite defect levels in III –V compounds

Chemical trends for all deep antisite defect levels which are expected to lie within or close to the main energy gap are presented for nine III-V compounds. We use a previously presented rescaled defect-molecule model to select the relevant levels and calculate their position by extrapolating from available experimental data in GaAs. Charge-state effects as well as symmetry-conserving lattice distortions are included qualitatively. Anion antisite defects are fourd to produce deep A₁ levels within the main energy gap and T₂ levels close to the conduction band edge. For most of the investigated compounds we find that cation antisite defects induce deep T₂ levels which lie within the forbidden energy gap. No other deep sp³-type levels are expected to lie within or close to the main energy gap. Both the prediction and the calculated positions of these levels are in good agreement with previous calculations and the few experimental data available. The predicted chemical trends agree well with those obtained previously by tight-binding models, where available. This is quite remarkable because our model is mainly based on a simple rescaling assumption similar to that of tight-binding models, but does not require a detailed information on the band structure of the host.     

New mechanism of solution of the k B T-problem in magnetobiology

The effects of ultralow-frequency or static magnetic and electric fields on biological processes is of huge interest for researchers due to the resonant change of the intensity of biochemical reactions, despite the energy in such fields being small in comparison with the characteristic energy k _B T of the chemical reactions. In the present work, a simplified model to study the effects of weak static magnetic fields on fluctuations of the random ionic currents in blood is presented with a view to solving the k _B T problem in magnetobiology. An analytic expression for the kinetic energy of the molecules dissolved in certain liquid media is obtained. The values of the magnetic field leading to resonant effects in capillaries are then estimated. The numerical estimates show that the resonant values of the energy of molecules in capillaries and the aorta are different. These estimates prove that under identical conditions, a molecule in the aorta gets 10^?9 times less energy than the molecules in blood capillaries. Therefore, the capillaries are very sensitive to the resonant effect. As the magnetic field approaches the resonant value, the average energy of a molecule localized in a capillary is increased by several orders of magnitude as compared to its thermal energy. This amount of energy is sufficient to cause deterioration of certain chemical bonds.     

Nuclear vertex constants and asymptotic normalization coefficients for 8Be resonance states from effective-range expansions for αα scattering

The properties of the first excited state of the ⁸Be* nucleus (2⁺) are studied. This state corresponds to the resonance in αα scattering at the energy of E _α = E ₂ ≈ 3 MeV. Use is made of an expansion of the effective-range function K(k ²). The function K(k ²) is sensitive to the value of E ₂. A fit to experimental data on the dependence of the Coulomb-nuclear phase shift δ ₂ ^C on the energy E _α leads to an E ₂ value that is smaller than the average value obtained from an analysis of various reactions. The experimental behavior of δ ₂ ^C (E _α) cannot be described satisfactorily by fixing the average value of E ₂. The renormalized nuclear vertex function for the process α + α → ⁸Be*(2+) and the asymptotic normalization coefficient for the respectiveGamow wave function are calculated by using the set of parameter values found in the present study.     

A local versus non-local t-matrix in the N(p, 2p)C reaction at 46 MeV

The angular distributions for the ¹⁴N(p, 2p)¹³C reactions at 46 MeV incident proton energy are calculated in the distorted wave t-matrix approximation (DWTA) where approximate optical-model waves are used. A comparison is made between the calculation using a local t-matrix to that of a non-local t-matrix. The (p, 2p) angular distribution is smaller in magnitude where a non-local t-matrix is employed compared to the calculation using a local t-matrix which implies that there is an overall enhancement of absorption associated with the non-local t-matrix. This also implies that differences between the local and non-local off-energy-shell effects can be significant. Parameter studies were undertaken for the distorted waves and bound state wave function and the effects on the angular distributions were similar in the local and non-local cases. The distortion effect due to the final-state focus phase dramatically changes the shape of the angular distribution. The calculations are considered to be a test of the off-energy-shell effects due to non-local interaction. This calculation is also a test of the approximate distorted waves at 46 MeV and the comparison to the ¹⁴N(p, 2p)¹³C data indicates that the distortion is reasonably well described.     

Strong interaction physics from hadronic atoms

Hadronic atoms provide a unique laboratory for studying strong interactions and nuclear medium effects at zero kinetic energy. Previous results from analyses of strong-interaction data consisting of level shifts, widths and yields in π⁻, K⁻, p̄ and ∑⁻ atoms are reviewed. Recent results from fits to comprehensive sets of data in terms of density-dependent optical potentials that respect the low-density limit, where the interaction tends to the free hadron nucleon value, are discussed. The importance of using realistic nuclear density distributions is highlighted. The introduction of density dependence in most cases significantly improves the fit to the data and leads to some novel results. For K⁻ atoms, a substantial attraction of order 200 MeV in nuclear matter is suggested, with interesting repercussions for K̄ condensation and the evolution of strangeness in high-density stars. For p̄ atoms it is found that a reasonable p-wave strength can be accommodated in the fitted optical potential, in agreement with the energy dependence observed for some low-energy p̄N reactions. For ∑⁻ atoms, the fitted potential becomes repulsive inside the nucleus, implying that Σ hyperons generally do not bind in nuclei in agreement with recent measurements. This repulsion significantly affects calculated masses of neutron stars.     

The theoretical and experimental study of the ionization processes during the low energy ion sputtering

The process by which atoms are ionized as they are sputtered from a metal surface has been analyzed both theoretically and experimentally. In the theoretical part the expressions for ionization coefficient R⁺ of atoms having the ionization energy much larger than the metal work function have been derived using a molecular orbital method. The effect of the level crossing was estimated in an approximate way. In the experimental part the SIMS experiments on clean Ni and Al surfaces and on Ni surface covered with a submonolayer of adsorbed K, Na and Al are reported. It has been found and it is for the first time reported that the energy distribution of ions sputtered from a submonolayer of adatoms is independent of energy (200–2500 eV) and mass (Ar⁺ Xe⁺ of incident ions and depends only upon the adsorption energy of the adatom. The energy distribution of ions sputtered from bulk samples has been found dependent on the primary ion energy. The measurement of the absolute value of R⁺ has shown that there is a strong correlation between the number of the adatom valence d-electrons and the value of R⁺, the value of R⁺ being smaller for atoms with more d-electrons. These experimental data have been compared with the theoretical expressions and the important role of the mechanism which takes into account the bending of the adatom energy level has been assessed.     

A model of deep inelastic polarized electroproduction

A realistic phenomenological model combining parton/QCD ideas with lower energy SU(6) constraints is proposed for the shape and evolution of the leading spin-dependent structure function G^ep(x, Q²) in polarized electroproduction. Close's broken-SU(6) ansatz is used to relate appropriately defined polarized quark-parton distribution densities to unpolarized ones at the matching momentum scale Q² = Q₀². The differences between spin and helicity distribution densities as well as the complications due to perturbative QCD and parton k_T (with related target-mass) effects are taken into account. Evolution to higher (>10 GeV²) values of Q² (where target-mass effects can be neglected) yields experimentally testable numerical predictions that are presented through various plots. The value of Q₀ is self-consistently determined to be about 0.5 GeV.     

Dimensional effects of debye-waller factors in layered crystals

It has been found by He atom scattering and LEED, that the mean square vibrational amplitude 〈u²_c〉 normal to the basal planes of graphite does not saturate at low temperatures to the zero point energy value predicted by Debye theory, but decreases substantially below that value as T approaches zero. This result has been interpreted as being due to the strong anisotropy and reduced dimensionality of graphite, and has been observed, so far, only for surface atoms. Using X-rays, we have observed similar effects for bulk atoms of graphite and 1T-TaS₂. The (00 18) reflection for graphite, and the (00 16) for TaS₂, have been monitored as functions of T between 300 and 5K. While the Debye model works well in both cases above 100K, 〈u²_c〉 saturates to a value 10.2% lower than that predicted by the model in the case of graphite, and 23.8% in the case of TaS₂.     

A measurement of the neutral current electroweak parameters using the fermilab narrow band neutrino beam

We report a measurement of the electroweak parameters sin₂θ ^w and ? based on the ratios of neutral current to charged current events measured in the Fermilab narrow-band neutrino beam at energies of 30–240 GeV. The data are fully corrected for radiative effects, heavy-quark production, and other effects. The best value for sin₂θ ^w obtained, sin₂θ ^w =0.239±0.011, is consistent with the most recent values fromW andZ production, as well as from other neutrino experiments.     

Comparison of planar features of K−p interactions with e+e− annihilations and deep inelastic μp scattering

The planar features of hadronic final states in K^?p interactions at 4.5, 5.6 and 14.3 GeV c.m. energy are compared with data from e⁺e^? annihilation and deep inelastic μp scattering. A strong energy variation of the distributions (1/σ)dσ/dp_t², 〈p_t²〉_in and Σp²_{t in} is observed over this energy range. Striking agreement is found between the K^?p data at 14.3 c.m. energy and the leptonic data at similar hadronic c.m. energies. The behaviour of these distributions from K^?p data is not well described by the simple quark fragmentation model, but shows deviations similar to those attributed to hard gluon effects in leptonic interactions.     

An α-cluster model for Λ 9 Be spectroscopy

An α-cluster model is applied to study low-lying spectrum of the _Λ ⁹ Be hypernucleus. The three-body ααΛ problem is numerically solved by the Faddeev equations in configuration space using phenomenological pair potentials. We found a set of the potentials that reproduces experimental data for the ground state (1/2⁺) binding energy and excitation energy of the 5/2⁺ and 3/2⁺ states, simultaneously. This set includes the Ali-Bodmer potential of the version “e” for αα and modified Tang-Herndon potential for αΛ interactions. The spin-orbit αΛ interaction is given by modified Scheerbaum potential. Low-lying energy levels are evaluated applying a variant of the analytical continuation method in the coupling constant. It is shown that the spectral properties of _Λ ⁹ Be can be classified as an analog of ⁹Be spectrum with the exception of several “genuine hypernuclear states”. This agrees qualitatively with previous studies. The results are compared with experimental data and new interpretation of the spectral structure is discussed.     

Variation of even-odd proton effects with excitation energy in fission of 252Cf: Confirmation of fine structure in v(A)

The existence of even-odd proton effects (fine structure) in νv(A) of individual fragments from ²⁵²Cf(sf) has been confirmed by analysis of previously reported data. The fine structure is seen to increase in amplitude as the fragment excitation energy decreases, a behaviour similar to the well-known behaviour of the mass yield curve. The present mass yield data also show these effects, as expected. Conversely, our total kinetic energy data TKE(A), not previously reported, show very little even-odd proton effect. It is shown that energy balance considerations, also, support the existence of even-odd proton effects in neutron emission from ²⁵²Cf(sf).     

Inclusive processes and shadow effects in deuteron

Using the data on inclusive spectra we analyze the contribution of inelastic intermediate states to the shadow correction Δ for high-energy (E > 10 GeV) hadron-deuteron scattering. We note that the intermediate states with large masses M² ～ ER^?1 may contribute appreciably to the shadow correction, but the estimate of this contribution in the framework of the Regge-pole model for inclusive processes shows that it is small. The main contribution to the Δ is due to the small masses M < 2 GeV, which are produced by diffraction dissociation. We calculate the value Δ_inel for pd, πd and Kd scattering and estimate the energy dependence of Δ. The results are in agreement with the existing experimental data.     

High-resolution infrared spectrum of cyanogen

The high-resolution spectrum of cyanogen (¹⁴N¹²C¹²C¹⁴N) has been measured from 500 to 4900 cm⁻¹. For this isotopomer many combination levels with both degenerate fundamentals, ν₄ and ν₅, have been measured for the first time and the effects of vibrational l-type resonance are observed as well as rotational l-type resonance. The effects of the vibrational resonance coupling ν₂ and 2ν₄ have also been studied. The data have been combined with earlier measurements below 500 cm⁻¹ to give a comprehensive catalog of the vibrational energy levels and the rovibrational constants for the normal isotopomer of cyanogen. A comparison of the term value constants for the three major symmetric isotopomers is given and they are compared with a recent ab initio calculation. The present data were combined with earlier work on the two symmetric isotopomers, ¹³C₂¹⁴N₂ and ¹²C₂¹⁵N₂, to obtain the equilibrium bond lengths, r_CC = 138.109(60) pm and r_CN = 115.976(40) pm.     

Ultrasonic detection of the pinning of dislocations by point defects in lead—II. Model for dislocation defect interaction

Experiments are presented to establish that irradiation produced defects in lead not only pin dislocations but also can be trapped at the ends of dislocation lines in agreement with the model proposed by Thompson, Buck, Huntington and Barnes. This model indicates that there is a temperature T^* at which there is a maximum pinning of dislocations. T^* is found to be near 140 K. The data of Part I are analyzed according to this model using reasonable values of the dislocation density and the binding energy of the defect in the trap. The resulting activation energy for the region A process in the reaction kinetics model is found to be 0.15 eV which is consistent with the value found from an eigenvalue expansion model.     

Precocious scaling and nonperturbative effects in QCD

The onset of nonperturbative effects in QCD is studied in two ways: (1) by means of the nonvanishing vacuum expectation value of 〈g ² F ²〉 introduced by Shifman, Vainshtein and Zakharov; (2) using a finite energy sum rule (FESR) for the renormalization group function β. Our considerations are based upon the recently proposed “physical” β_MMOM, which is gauge invariant and shows explicit mass-decoupling.