A new Coulomb correction method for Bose-Einstein correlations,based on the π+π− correlation measurements

We present the measured correlation functions for π⁺π^?, π^?π^? and π⁺π⁺ pairs in central S+Ag collisions at 200 GeV per nucleon. The Gamov function, which has been traditionally used to correct the correlation functions of charged pions for the Coulomb interaction, is found to be inconsistent with all measured correlation functions. Certain problems which have been dominating the systematic uncertainty of the correlation analysis are related to this inconsistency. It is demonstrated that a new Coulomb correction method, based exclusively on the measured correlation function for π⁺π^? pairs, may solve the problem.     

Determination of the fire-ball dimensions from second-order interference between two pions

Positive correlations are observed for pion pairs of equal charge and similar momentum vectors, produced in the reactions πp→p+5π and πp→p + 7π at 4 to 25 GeV/c. The results are consistent with being due to the second-order interference effects expected for pairs of identical bosons and lead to the determination of the average dimension of the “fire-ball’ from which the pions are emitted (〈R〉 = 1.0 ± _?0.2^+0.4 fm). Attempts are made to study the fire-ball shape by selecting pions pair emitted in various polar and azimuthal directions.     

The role of the quantum dispersion in the Coulomb correction of Bose-Einstein correlations

The time dependent Schrödinger equation for two identical and charged pions is solved using wavepacket states. It is shown that the expected Coulomb distortion in the momentum correlation function is obliterated by the dispersion of the localized states, and therefore becomes unobservable.     

Three applications toSO(4) invariant systems of a theorem of L. Michel relating extremal points to invariance properties

We consider a theorem due to Michel [1] which relates the invariance properties in peculiar directions in a linear space on which we represent a Lie groupG to the extremal points of an arbitrary smoothG-invariant function. The group we are interested in isSO(4) and we apply the mathematical results to the following problems:

1. mixed linear Stark Zeeman effect in a hydrogen atom,
2. perturbation of a finite Robertson-Walker metric,
3. gas evolutions preserving angular momentum and vorticity.

     

Radiative corrections for pion polarizability experiments

We use the semi-analytical program RCFORGV to evaluate radiative corrections to onephoton radiative emission in the high-energy scattering of pions in the Coulomb field of a nucleus with atomic numberZ. It is shown that radiative corrections can simulate a pion polarizability effect. The average effect is α _π ^rc =?β _π ^rc =(0.20±0.05)×^?43 cm³, for pion energies 40–600 GeV. We also study the range of applicability of the equivalent photon approximation in describing onephoton radiative emission.     

p + p → d + π+ p-wave production

The production of p-wave pions in p + p → d + π⁺ is calculated by introducing into the initial wavefunction NΔ configurations consistent with elastic scattering. Reasonable agreement with experiment is obtained without further adjustment. The Galilean term has only a small effect.     

Quantitative assessment of target dependence of pion fluctuation in hadronic interactions – estimation through erraticity

Event-to-event fluctuation pattern of pions produced by proton and pion beams is studied in terms of the newly defined erraticity measures χ(p, q), $\chi_q^{\prime}$ and $\mu_q^{\prime}$ proposed by Cao and Hwa. The analysis reveals the erratic behaviour of the produced pions signifying the chaotic multiparticle production in high-energy hadron–nucleus interactions (π ^???–AgBr interactions at 350 GeV/c and p–AgBr interactions at 400 GeV/c). However, the chaoticity does not depend on whether the projectile is proton or pion. The results are compared with the results of the VENUS-generated data for the above interactions which suggests that VENUS event generator is unable to reproduce the event-to-event fluctuations of spatial patterns of final states. A comparative study of p–AgBr interactions and p–p collisions at 400 GeV/c from NA27, with the help of a quantitative parameter for the assessment of pion fluctuation, indicates conclusively that particle production process is more chaotic for hadron–nucleus interactions than for hadron–hadron interactions.     

Photoproduction of charged pions on deuterium in the first resonance region

Photoproduction of π⁺ and π^? on deuterium has been measured in the photon energy range from 240 to 400 MeV and for pion c.m. angles between 15° and 180°. The pions were analysed in angle and momentum by a magnetic spectrometer. From the measured π^?/π⁺ ratio, corrected for Coulomb interactions in the final state, differential cross sections of the reaction γ+n→π^?+p were calculated. Together with the π⁺ photoproduction our data show no isotensor contribution. Comparison of our data with the recent experiments done on the inverse reaction shows no evidence of a violation of time reversal invariance. With the measured π⁺ photoproduction on deuterium, a test of the spectator model has been made. Using the closure-approximation of Chew and Lewis our data agree within a range of ±10%.     

Astroparticle physics with high energy neutrinos: from AMANDA to IceCube

Kilometer-scale neutrino detectors such as IceCube are discovery instruments covering nuclear and particle physics, cosmology and astronomy. Examples of their multidisciplinary missions include the search for the particle nature of dark matter and for additional small dimensions of space. In the end, their conceptual design is very much anchored to the observational fact that Nature produces protons and photons with energies in excess of 10²⁰ eV and 10¹³ eV, respectively. The puzzle of where and how Nature accelerates the highest energy cosmic particles is unresolved almost a century after their discovery. The cosmic ray connection sets the scale of cosmic neutrino fluxes. In this context, we discuss the first results of the completed AMANDA detector and the science reach of its extension, IceCube. Similar experiments are under construction in the Mediterranean. Neutrino astronomy is also expanding in new directions with efforts to detect air showers, acoustic and radio signals initiated by super-EeV neutrinos. The outline of this review is as follows:

Introduction

Why kilometer-scale detectors?

Cosmic neutrinos associated with the highest energy cosmic rays

High energy neutrino telescopes: methodologies of neutrino detection

High energy neutrino telescopes: status

     

Dynamical enhanced electron emission and discharges at contaminated surfaces

Broad-area electrodes show electron emission already at electric field strengthsF≈10⁷ V/m. This enhanced field emission (EFE) occurs only for contaminated surfaces. EFE is accompanied by photon emission and gas desorption yielding finally discharges. EFE is caused by dust and contaminants initiating the following effects:

an electron is stochastically emitted in a trigger zone

the electron gains energyΔE?eΔxF ^*

which excites electronic states

which relax by the emission of electrons, photons, and atoms

where the positive charges left behind enhanceF ^*=βF (β?1) initiating so an electron avalanche, i.e., a high conductivity channel. Because of charge migration and neutralization, this avalanche has a life time. This pulsating EFE is accompanied by light emission and gas desorption yielding finally a gas cloud and a discharge.

The pulsating, self-sustained EFE has the same root as:

the enhanced secondary emission found first by Malter

the conductivity switching exhibited by thin (≈ 1 μm) layers of semiconductors or insulators

the normal cathode fall and

the firing-wave instability in neurodynamics.

     

Optically-pumped stimulated recombination radiation inp-type InSb in high magnetic fields

In this paper measurements of the frequency, linewidth and polarization of stimulated recombination radiation (SRR) fromp-type InSb are reported. The samples had low excess-carrier concentrations between 10¹⁴ and 10¹⁵ per cm³ and different lengths between 0.4 and 9 mm. They were held in magnetic fields up to 6T at temperatures of pumped liquid helium. The excitation was done optically by the radiation of a Q-switched CO-laser. We could observe a number of different stimulated processes:

1. band-to-band recombination (tuning between 1875 and 1980 cm^?1),
2. band-to-acceptor recombination (tuning between 1840 and 1930 cm^?1),
3. stimulated spin-flip Raman scattering (SFR) of the SRR by excited electrons,
4. SFR of the laser by excited electrons and its interaction with the SRR.

From the observed shift of the band gap by exchange and correlation energy the number of created electron-hole pairs can be calculated to be up to 10¹⁶ per cm³. The observed acceptor binding energy varies from 66 cm^?1 atB=0 to 71 cm^?1 at 4.5T.     

Ambiguities in theη-nucleon scattering length determination

The positive sign of theη-nucleon scattering lengthb _ηN was predicted in [1] assuming the resonance mechanism for theπ ^?p → ηn reaction. We demonstrate that

1. the assumption about thet-channel mechanism of the reaction leads tob _ηN < 0 and
2. the experimental data on theη production cross section are equally compatible with both resonance andt-channel mechanisms.

     

Parametrization of Bose–Einstein correlations and reconstruction of the space–time evolution of pion production in ee annihilation

A parametrization of the Bose–Einstein correlation function of pairs of identical pions produced in hadronic e⁺e⁻ annihilation is proposed within the framework of a model (the τ-model) in which space–time and momentum space are very strongly correlated. Using information from the Bose–Einstein correlations as well as from single-pion spectra, it is then possible to reconstruct the space–time evolution of pion production.     

Fractal diffusion processes in particle physics

A series of consistent measurements of kinematic variables for pion diffraction production processes by pions with an initial momentum of about 4 GeV/c were analyzed: π ⁺ + p → p + 2π ⁺ + π ^? and π ^? + p → p + 2π ^? + π ⁺. The Hurst method analysis discovered the presence of the memory effect for both data arrays. The distributions of the transition probability density appeared to seek some equilibrium shape, characteristic of the fractal Brownian motion (FBM). The process can be defined by the special diffusion Fokker-Planck equation (FPE). The obtained values of Hurst coefficient 0.5 < H < 1, which is a parameter of FPE, mean that the processes explored are realized in fractal generalized phase space with fractional dimension.     

Nachwirkungsmechanismen in Ferriten

In ferrites a large number of after-effects are found, with time constants between nano-seconds and years. In this review the after-effects due to ion-and electron motion will be treated. One finds:

1. single-ion effects in combination with lattice deformations, e.g. Mn³⁺;
2. ion effects caused by mobile vacancies, e.g. Co²⁺;
3. effects due to electron transfer:
4. Co²⁺?Co³⁺
5. Me²⁺?Fe³⁺, in combination with Me⁴⁺ and vacancies.
6. Me⁴⁺?Fe²⁺, with Me=Si, Ti (photomagnetic effect).

The electron transfer is found to be related to electrical effects. In analogy to the photoelectric effect, one has found that illumination produces changes in magnetic properties. Generally speaking, one has in ferrites as many problems with donors and acceptors as in other semiconductors. Information from magnetic measurements helps to elucidate their nature.     

A study of\bar np annihilations between 0.5 and 0.8 GeV/c

A study of \(\bar np\) annihilations with \(\bar n\) momentum between 0.5 and 0.8 GeV/c is presented. The search fors-channel resonances in \(\bar np\) annihilations reveal possibly two narrow structures in the odd pions final state. Inclusiveρ ⁰ andf ⁰ cross sections in \(\bar np\) annihilations have been estimated to be 9.0±0.6 mb and 3.4±0.6 mb respectively. Longitudinal and transverse momentum distributions for inclusiveρ ⁰ production have been presented. A study of resonance production in exclusive final state revealsρ ⁰ production to be dominant in the odd pion final states andρ ⁺,ω ⁰ productions are most important for the even pion final states. Theπ ⁺ π ^? effective mass spectra in the backward and the forward directions in the \(\bar np\) c.m. system have been examined for a possible ?-ω interference effect.     

A proof of the unitarity ofS-matrix in a nonlocal quantum field theory

Using the formfactors which are entire analytic functions in a momentum space, nonlocality is introduced for a wide class of interaction Lagrangians in the quantum theory of one-component scalar field φ(x). We point out a regularization procedure which possesses the following features:

1. The regularizedS ^δ matrix is defined and there exists the limit $$\mathop {\lim }\limits_{\delta \to 0} S^\delta = S.$$
2. The Green positive-frequency functions which determine the operation of multiplication in \(S \cdot S^ + \mathop = \limits_{Df} S \circledast S^ + \) can be also regularized ?^δ and there exists the limit $$\mathop {\lim }\limits_{\delta \to 0} \circledast ^\delta = \circledast \equiv .$$
3. The operator \(J(\delta _1 ,\delta _2 ,\delta _3 ) = S^{\delta _1 } \circledast ^{\delta _2 } S^{\delta _3 + } \) is continuous at the point δ₁=δ₂=δ₃=0.
4. $$S^\delta \circledast ^\delta S^{\delta + } \equiv 1at\delta > 0.$$ Consequently, theS-matrix is unitary, i.e. $$S \circledast S^ + = S \cdot S^ + = 1.$$

     

Inclusive prompt photon production inpp and\bar p p interactions

High transverse momentum (p _T ) production of pions and photons in proton-proton and proton-antiproton interactions are studied within the QCD framework and compared with the presently available experimental data. Scaling violation effects are included, and shown to be important at largep _T . Predictions are made for the γ/π⁰ ratio at collider energies. The possibility of extricating the gluon distribution function from the invariant cross section data for the process \(\bar p\) +p→γ+X is suggested.