Multiple Meson Production Research Articles

Electroproduction of tensor mesons in QCD

Due to multiple possible polarizations hard exclusive production of tensor mesons by virtual photons or in heavy meson decays offers interesting possibilities to study the helicity structure of the underlying short-distance process. Motivated by the first measurement of the transition form factor $\gamma^*\gamma \to f_2(1270)$ at large momentum transfers by the BELLE collaboration we present an improved QCD analysis of this reaction in the framework of collinear factorization including contributions of twist-three quark-antiquark-gluon operators and an estimate of soft end-point corrections using light-cone sum rules. The results appear to be in a very good agreement with the data, in particular the predicted scaling behavior is reproduced in all cases.

Recent results from ELSA

One of the foremost challenges in hadron physics is to obtain an understanding of the structure of baryons. The main features of the baryon mass spectrum at low excitation energies are reasonably known and described quite accurately by models, but the high-mass spectrum is still rather obscure. With modern achievements in accelerators, highly polarized nucleon targets and hermetically closed detectors allowing for charged and neutral particle detection high-lying excitations can be investigated through the systematic study of single and multiple meson production. In this contribution the instrumentation and results of experiments from the ELSA accelerator at Bonn as well as their significance for baryon resonance analyses are described. In particular, data on photoproduction of vector and pseudoscalar mesons of different flavors are presented.

Meson production and nuclear fragmentation of the nuclei in the atmosphere.

Propagation of primary and secondary cosmic rays in the atmosphere is calculated analytically. Two different cases of primary-cosmic-ray composition are used: the first case assumes a mixed composition of very heavy, heavy, middle, and $\ensuremath{\alpha}$ nuclei and nucleons; the second case considers only nucleons in the primary-cosmic-ray flux. The mechanism of multiple meson production is formulated according to the wounded-nucleon model for a nucleus-nucleus interaction and the scaling model for a nucleon-nucleon interaction. The mechanism of nuclear fragmentation is formulated according to experimental values of the fragmentation parameters at low energy. The calculated results of the electromagnetic flux are compared with the results of mountain experiments with a large-scale emulsion chamber and experimental data at airplane altitudes. From these comparisons the model with heavy nuclei gives the best fit.

Behaviour of Cosmic Rays in the Atmosphere at Super High Energy Region

Propagation of high energy cosmic rays in the atmosphere is calculated analytically relative to their longitudinal as well as lateral aspects, based on a model using the accelerator results on multiple meson production. Main concern is the energy spectrum, I( > E), and the lateral energy spread, , of particles of various components in each resultant atmospheric cosmic· ray phenomenon, called family in emulsion chamber experiments. Discussions are made on how each constituent assumption in the model affect the above· mentioned quantities.

Recombination in Multiple Hard Scattering and Meson Production at Large Transverse Momentum in High Energy Nucleus-Nucleus Collisions

Recombination in Multiple Hard Scattering and Meson Production at Large Transverse Momentum in High Energy Nucleus-Nucleus Collisions

Breakdown of Feynman scaling in high-energy cosmic-ray interactions

Extensive Monte Carlo calculation on $\ensuremath{\gamma}$-ray families was carried out under appropriate model parameters which are currently used in high-energy cosmic-ray phenomenology. Characteristics of $\ensuremath{\gamma}$-ray families are systematically investigated by the comparison of calculated results with experimental data obtained at mountain altitudes. The discussion is devoted mainly to examining the validity of Feynman scaling in the fragmentation region of multiplemeson production. It is concluded that the experimental data cannot be reproduced under the assumption of the scaling law if primary cosmic rays are dominated by protons. Other possibilities on primary composition and increase of interaction cross section are also examined. These assumptions are consistent with experimental data only when we introduce intense dominance of heavy primaries in the high-energy region and very strong increase of the interaction cross section (say $\ensuremath{\sigma}\ensuremath{\propto}{{E}_{0}}^{0.06}$) simultaneously. Otherwise, the breakdown of Feynman scaling in the fragmentation region and the existence of azimuthal asymmetry in production mechanism are strongly suggested by high-energy cosmic-ray interactions (${E}_{0}\ensuremath{\gtrsim}{10}^{15}$ eV).

Lateral Structure of Electrons in an Extensive Air Shower –Simulation Study–

The relation between the longitudinal development and the lateral distribution of electrons in extensive air shower is theoretically investigated by a simulation study. The results show that the features of the first collision are not the main factor that govern the fluctuation of the lateral distribution. The attenuation length and the lateral distribution of electrons are strongly correlated. The correlation, which is described by a simple formula, is insensitive to the gross value of inelasticity but is sensitive to the details of energy distribution among the secondary particles. A comparison of experimental results with this relation suggests that the multiple meson production mechanism at air shower energies (\({\gtrsim}100\) TeV) is different from that at \({\lesssim}1\) TeV.

Study of Multiple Meson Production at Cosmic Ray Energy. III: Transverse Behaviour of Gamma-Ray Air Family

Study of Multiple Meson Production at Cosmic Ray Energy. III: Transverse Behaviour of Gamma-Ray Air Family

Study of Multiple Meson Production at Cosmic Ray Energy. II: Analytical Derivation of Lateral Structure Function of Gamma-Ray Air Family

Study of Multiple Meson Production at Cosmic Ray Energy. II: Analytical Derivation of Lateral Structure Function of Gamma-Ray Air Family

Study of Multiple Meson Production at Cosmic Ray Energy. I: Longitudinal Behaviour of Gamma Ray Air Family

Study of Multiple Meson Production at Cosmic Ray Energy. I: Longitudinal Behaviour of Gamma Ray Air Family

Fire-Balls and Accelerator Experiments

The energy of accelerator has been increasing and already come to 300 GeV at NAL and 1,500 GeV at CERN machine. These large proton ac­ celerators are offering a large number of and various kinds of data on the multiple production of tnesons in high energy regions, which have been offered till the present only by the cosmic-ray experiments. The cosmic-ray experiments already gave indication for the existence of a spherical fire-ball with constant mass and temperature as the intermediate product of the multiple production of mesons.1),2) The authors made a fire­ ball study with the bubble chamber film on 10 GeV 7T--p collisions and with the emulsion stacks exposed to 24 Ge V proton beam, and the results showed existence of a spherical fire-ball of mass -2.4· GeV.3) From the above results it becomes highly probable that a fire-ball is playing an essential role for the multiple meson production over a wide range of energies, i.e., from about 10 GeV up to around 100,000 GeV.2),3) Further­ more, the physical properties of a fire-ball, such as its rest energy and temper­ ature, appear to remain constant, and increase of available energy is causing increase of velocity and number of produced fire-balls. These features are consistent with the H-quantum model. 4 > Because of importance of the conclusion and the information from the large accelerators being now available, the authors made a general survey over the published results on the multiple meson production from the acceler­ ator experiments, on the basis of the hypothesis of a fire-ball of constant mass and temperature. The results show that all the available data are in good consistency with the hypothesis and Serpukhov, NAL and CERN experiments are covering the region of production of two, three, four or more fire-balls.

On the Multiplicity Distribution in Hadronic Interaction at High Energy

Frqm recent experiments with the accelerators at Serpukhov and NAL we have now some knowledge on the multiplicity distribution of mesons in hadronic interactions at laboratory incident energies in the range (50,_,400) GeV. On the basis of the current idea that in the energy range covered by the accelerators now working hadron reactions have yet reached their asymptotic limits, that is, on the assumption that we are in the '' asymptotia' ', there have been many trials to get a universal function describing the experimental multiplicity distribution now obtained. One of such trials is Buras and . Koba's one,l) who used functions of the type such as ze-1rz / 4 , or its mixture with z3e-1lZ/4, to fit the experimental data, along Koba, Nielsen and Olesen's idea2> that the multiplicity distribution should be represented by a unique function z=n/(n) at high energies, where n and (n) are the multiplicity and the mean multiplicity, respectively. On the other hand, in journals there has been paid much interest in the fact that the experimental data give us .a value of about two for the ratio of the mean multiplicity to the standard deviation (n)/ { (n2)-(n)2} l/2, or, being expressed in another way, in the fact that the quantity /2=(n(n-l)) (n)2 is not zero experimentally. This is because the multiplicity distribution would be expected to be like the Poisson distribution, if one may take the bremsstrahlung analogy for the multiple production of mesons in hadronic interactions at high energy, and with the Poisson distribution one has D= ..J(n) and /2=0. The bremsstrahlung analogy has been used by Feynman3)

On the lifetime of the muon state of the electron-muon mass doublet

In a previous paper the electron and muon masses were derived by combining the author’s general relativistic derivation of the inertial masses of spinor particles from the geometrical field and his model of the « physical vacuum » (from a self-consistent field theory of electrodynamics) in terms of an ideal gas of electron-positron pairs in a particular state that was derived from the theory. It was predicted earlier that in this field theory spinor particles occur in mass doublets. In the electron-muon case, the observation of the « heavy electron » (muon) is a consequence of quadrupolar excitation of the physical vacuum of pairs—correspondingly altering the geometrical field in the vicinity of the observed electron, thereby making it more inertial. In this paper, the lifetime of the heavy electron in this physical vacuum will be determined, de-excitation occurring by the transferral of electromagnetic energy from this heavy electron to the pairs of the physical vacuum by means of a quadrupolar transition. To facilitate the calculation with time-dependent perturbation theory, use is made of Fermi’s multiple-meson production theory, and the improvisation of his theory for break-up reactions by the author. In this way, the ensuing quantitative analysis yields a lifetime for the heavy electron that is of the order of 2.09·10-6 s, which is within 5% of the observed muon decay rate. It is then shown how the present theory, in which electromagnetic variables are in terms of 2-component spinor fields, explains the reaction Μ → e++Ν in terms of a process that is purely electromagnetic and does not entail neutrinos.

Monte Carlo Simulation on Propagation of Cosmic-Rays in the Atmosphere

A simulation study is made on propagation and multiplication of the high energy cosmic-ray components in their passage through the atmosphere. The study is planned to simulate observation of high energy cosmic-ray phenomena by the emulsion chambers exposed at high altitude laboratories and to make clear how the observation of such kind will disclose unknown mechanism of the extremely high energy interactions-multiple production of mesons. In particular, the following two models of the multiple meson production are examined in the present simulation: 1) Two-fire-ball model,l> abbreviated as 2F; 2) H-quantum model,2> abbreviated as HQ. The outline of our simulation is as follows. A high energy primary cosmic-ray particle collides with an air nucleus of the upper atmosphere and causes the multiple meson production according to mechanism of the assumed models. The secondary nuclear-active particles, charged n-mesons and an outgoing nucleon, among the generated particles collide in their turn with air nuclei and they develop the so-called nuclear cascade processes while passing through the atmosphere. Gamma-rays, being the decay products of n°-mesons produced by the successive nuclear collisions, are the source of the atmospheric electromagnetic cascade showers. We make a record of particles with energies above a certain threshold energy both of the nuclear-active component and of the electro-magnetic component, which arrived at the observation level. The record consists of data of the arriving particles together with those on the primary particle. The present simulation calculation corresponds to observation of high energy cosmic-ray particles by the emulsion chamber exposed at the mountain altitudes. In particular, it provides us data of the artificial families: identity, energy and spatial distribution of member particles of the families. It is instructive to learn what kind of pattern the artificial families show at the observation plane under a certain assumption. This is indispensable for

A Model of Multiple Meson Production at Ultrahigh Energies

A Model of Multiple Meson Production at Ultrahigh Energies

Fireball Model with Double Regge Pole Exchange for Multiple Meson Production in the Accelerator Energy Region

Fireball Model with Double Regge Pole Exchange for Multiple Meson Production in the Accelerator Energy Region

Multiple Meson Production in Proton-Nucleon Interactions at 22.6 and 24 Gev/c

Multiple Meson Production in Proton-Nucleon Interactions at 22.6 and 24 Gev/<i>c</i>

Multiple Meson Production in Cascade Model

Multiple Meson Production in Cascade Model

Multiple Meson Production by Heavy Primary Nuclei of Cosmic Origin and their Fragmentation Products at Energies above1012eV

Studies were made of the interactions initiated by fragments, including nucleons, from the gradual breakup of ultra high-energy heavy nuclei in a large block of nuclear emulsion. The results obtained by this approach are free from the detection biases that arise in scanning for, e.g., high-energy electromagnetic cascades. For one family of genetically related interactions the primary per-nucleon energy could be reliably established as \ensuremath{\sim}1.3 TeV. The sample of nucleon-induced interactions with average multiplicity ${n}_{s}&lt;25$, with primary energies in the region of 1 TeV, show strong bimodality in the angular distribution of the created particles. An upper limit of 1.5 $\frac{\mathrm{BeV}}{c}$ is found for the average transverse momentum of the possible fireballs that could have given rise to this bimodality. The average inelasticity for the same sample of collisions is \ensuremath{\sim}0.6. The average multiplicity ${n}_{s}$ for the nucleon-induced interactions with ${N}_{h}\ensuremath{\le}5$ is \ensuremath{\sim}11.5. For the interactions initiated by heavy nuclei the lower limit to the average per-nucleon multiplicity, $\frac{{n}_{s}}{\ensuremath{\Delta}A}$, in the energy interval 1-20 TeV is consistent with the average multiplicity for the nucleon-induced interactions at about 1 TeV. A linear superposition, in nucleus-nucleus collisions, of elementary nucleon-nucleon acts of meson production is suggested.

Multiple meson production and some properties of loquian distributions

Some properties of angular distributions of jets of mesons produced in high-energy interactions are discussed in terms of the variable\(l = log\gamma _s tg\Theta _L \)(\(\gamma _s = Lorentz\) factor of the c.m. system,\(\Theta _L = emission\) angle in the laboratory system). Such distributions are called loquian distributions, because for a given distribution in the c.m. system, they are approximately independent of the primary energy. λ=logarithmicquasiinvariantangle. Loquian distributions for different c.m. system amplitudes are given and an analysis is discussed in terms of the moments of the loquian distributions. A fireball loquian distribution is approximately decomposed into one centre c.m. system amplitudes.