Average Multiplicity Research Articles

A Comparative Study on the Positive Lightning Return Stroke Electric Fields in Different Meteorological Conditions

Positive cloud-ground lightning is considerably more complex and less studied compared to the negative lightning. This paper aims to measure and characterize the significant parameters of positive return strokes electric field, namely, the zero-to-peak rise time, 10–90% rise time, slow front duration, fast transition rise time (10–90%), zero-crossing time, and opposite polarity overshoot relative to peak. To the best of the authors’ knowledge, this is the first time such detailed characteristics of positive lightning in Malaysia are thoroughly analyzed. A total of 41 positive lightning flashes containing 48 return strokes were analyzed. The average multiplicity is 1.2 strokes per flash. The majority of positive lightning was initiated from the primary positive charge rather than as a byproduct of in-cloud discharges. The cumulative probability distribution of rise time parameters, opposite polarity overshoot relative to peak, and slow front amplitude relative to peak are presented. A comparison between studies in four countries representing tropic, subtropic, and temperate regions was also carried out. Measured parameters in Florida, Sweden, and Japan are generally lower than those in Malaysia. Positive lightning occurrences in tropical regions should be further studied and analyzed to improve our current understanding on positive return strokes.

Prompt Fission γ–ray Spectra Characteristics – Systematics and Predictions

Revised systematics for prompt fission γ-ray spectra (PFGS) characteristics as function of both atomic and mass number of the compound system, derived from recent experiments on thermal-neutron induced and spontaneous fission, is presented and applied to fission induced by fast neutrons. Results from these calculations for 238U(n, f) and 235U(n, f) for incident neutron energies from 0 to 20 MeV are compared to new experimental results, exhibiting nice agreement. Very recent PFGS measurements for 240Pu(sf) and 242Pu(sf) have been evaluated and the determined PFGS characteristics are shown to also fit well with the systematics. From this we conclude that the obtained systematics, although purely empirical, is indeed a useful tool for the prediction of average total γ-ray energy released in prompt fission, mean energy per photon as well as average photon multiplicity for fissioning systems, which are difficult or even impossible to study experimentally.

Why not: Prompt Fission Neutrons are Released at Scission

The main properties of the neutrons released during the neck rupture and emitted immediately thereafter are calculated for 236U in the frame of a dynamical scission model. These properties are: the angular distribution with respect to the fission axis (calculated on spheres of radii R=30 and 40fm and at time T = 4 × 10−21sec), the distribution of the average energies of neutrons emitted from each state (calculated for durations of the neck rupture ΔT = 1 and 2 × 10−22sec) and the total neutron multiplicity (calculated for two values of the minimum neck-radius rmin=1.6 and 1.9fm). They are compared with measurements of prompt fission neutrons during 235U(nth, f). The experimental trends are well reproduced, i.e., the focussing of the neutrons along the fission axis, the preference of emission from the light fragment, the range, slope and average value of the neutron energy-spectrum and the average total neutron multiplicity. The neutron emission during a non-adiabatic scission process is therefore a viable alternative to the evaporation (from fully accelerated fragments) hypothesis.

Study of Compound Particle Production in <sup>28</sup>Si and <sup>32</sup>S-Emulsion Collisions at 14.6 and 200 AGeV

This work displays a study of the compound multiplicity characteristics of 14.6 and 200 AGeV/c 28Si and 32S-emulsion interactions, where the number of shower and grey particles taken together is termed as compound multiplicity, Nc. It has been found that the average compound multiplicity depends on the mass number of the projectile, Ap, and energy of the projectile. A positive linear dependence of the compound multiplicity on the black, grey, heavy and shower particles has been found. Also the scaling of compound multiplicity distributions produced in these interactions has been studied in order to check the validity of KNO-scaling. A simplified universal function has been used to represent the experimental data. The experimental results have been compared with those obtained by analyzing events generated with the computer code FRITIOF based on Lund Monte Carlo model.

Effect of sodium nitroprusside on micropropagation and biochemicalparameters of CAB-6P and Gisela 6 cherry rootstocks

The effects of sodium nitroprusside (SNP) on micropropagation of CAB-6P and Gisela 6 cherry rootstocks were investigated. Shoot multiplication of CAB-6P was reduced by adding 4.4 $\mu$M 6-benzylaminopurine (BA) and SNP. Gisela 6 microcuttings treated with BA + 30 $\mu$M SNP gave the highest average shoot number (4.15) and multiplication percentage (100%). In CAB-6P, $\alpha$-naphthaleneacetic acid (NAA) + 30 $\mu$M SNP led to the maximum root number (13.79) and fresh weight (0.336 g); average root length (82 mm) and rooting percentage (95.45%) were greatest after adding 40 and 10 $\mu$M SNP + NAA, respectively. In Gisela 6, NAA + 40 $\mu$M SNP resulted in the highest root number (9.75) and fresh weight (0.238 g), while NAA + 30 $\mu$M SNP enabled maximum root length (30.77 mm). Rooting percentage was greatest (84.62%) when Gisela 6 microcuttings were treated only with NAA. Application of SNP alone in CAB-6P reduced leaf chlorophyll, carbohydrate, and pr?line levels. In contrast, 30?50 $\mu$M SNP increased leaf chlorophyll levels of Gisela 6. SNP augmented leaf carbohydrate and proline content, but it diminished root carbohydrate content. In BA + SNP or NAA + SNP treatments, changes in biochemical constituents were dependent on SNP concentrations and genotypes.

Cumulative hadron production in pA collisions in the framework of z-scaling

Data on cumulative particle production in pA collisions with momentum [Formula: see text] are analyzed in the [Formula: see text]-scaling approach. Scaling function [Formula: see text] is constructed for different types of target nuclei and inclusive particle angle. The function is expressed via respective inclusive cross section and average multiplicity density of charged particles. This regime corresponds to low [Formula: see text] (low transverse momentum [Formula: see text]). Validity of the concept was verified for this data. A-dependence of the scaling function is studied for low-[Formula: see text] region. Self-similarity of hadron production in pA collisions is confirmed over a wide kinematic range.

Forward-backward multiplicity correlations of target fragments in nucleus-emulsion collisions at a few hundred MeV/u

The forward-backward multiplicity and correlations of a target evaporated fragment (black track particle) and target recoiled proton (grey track particle) emitted from 150 A MeV 4He, 290 A MeV 12C, 400 A MeV 12C, 400 A MeV 20Ne and 500 A MeV 56Fe induced different types of nuclear emulsion target interactions are investigated. It is found that the forward and backward averaged multiplicity of a grey, black and heavily ionized track particle increases with the increase of the target size. The averaged multiplicity of a forward black track particle, backward black track particle, and backward grey track particle do not depend on the projectile size and energy, but the averaged multiplicity of a forward grey track particle increases with an increase of projectile size and energy. The backward grey track particle multiplicity distribution follows an exponential decay law and the decay constant decreases with an increase of target size. The backward-forward multiplicity correlations follow linear law which is independent of the projectile size and energy, and the saturation effect is observed in some heavy target data sets.

Prompt neutron multiplicity in correlation with fragments from spontaneous fission ofCf252

The spontaneous fission of $^{252}\mathrm{Cf}$ serves as an excellent benchmark of prompt emission in fission since experimental data can be obtained without the need of an incident beam. With the purpose of providing experimental data on the prompt fission neutron properties in correlation with fission-fragment characteristics, an experiment on $^{252}\mathrm{Cf}$(SF) has been performed. In addition, the experiment serves as a benchmark of setup and analysis procedures for measurements of fluctuations in the prompt-neutron properties as a function of incident neutron energy in fission of the major actinides $^{235}\mathrm{U}$ and $^{239}\mathrm{Pu}$. The experiment employs a twin Frisch grid ionization chamber as fission-fragment detector while neutrons were counted by using a liquid scintillator placed along the symmetry axis of the ionization chamber. Average neutron multiplicity has been obtained as a function of fission-fragment mass and total kinetic energy (TKE). The average multiplicity as a function of mass agrees well with available data in the literature in the mass range from 80 to 170 u. The existence of additional sawtooth structures in the far asymmetric mass region could not be confirmed, although the statistical accuracy of the present experiment is as good as the previous study where such structures have been reported [Nucl. Phys. A 490, 307 (1988).]. The available data in the literature on the TKE dependence of the multiplicity show strong deviations. Therefore, effort was focused on investigating experimental factors in low-efficiency neutron-counting experiments that may lead to faulty determination of this dependence. Taking these factors into account, a result that agrees well with data from high-efficiency neutron-counting experiments is obtained. The experimental arrangement allows determination of the angle between the detected neutron and the fission axis, which permits the neutron properties to be transformed into the fission-fragment rest frame. Fission neutron emission spectra in the fragment center-of-mass frame have thereby been obtained as a function of the fission-fragment mass and TKE.

A STUDY OF COMPOUND PARTICLES IN EMULSION

An attempt is made to study the compound particles by taking black and shower particles together. Average compound particle multiplicity is found to vary linearly with heavily ionizing particle multiplicity but with black particle multiplicity it does not show a linear dependence. Dispersion of the compound multiplicity distribution has also been studied. The ratio of the mean number of compound particles to its dispersion for different target sizes has been calculated.

Study of fission dynamics of the excited nuclei produced in fusion reactions in the framework of the four-dimensional Langevin equations

The dynamics of fission of excited nuclei has been studied by solving four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. The projection of the total spin of the compound nucleus to the symmetry axis, K, was considered as the fourth dimension in Langevin dynamical calculations. The average pre-scission neutron multiplicities, mean kinetic energy of fission fragments and the variances of the mass and kinetic energy have been calculated in a wide range of fissile parameter for compound nuclei 162Yb, 172Yb, 215Fr, 224Th, 248Cf, 260Rf and results compared with the experimental data. Calculations were performed with a constant dissipation coefficient of K, γK (MeV zs)-1/2, and with a non-constant dissipation coefficient. Comparison of the theoretical results for the average pre-scission neutron multiplicities, mean kinetic energy of fission fragments and the variances of the mass and kinetic energy with the experimental data showed that the results of four-dimensional Langevin equations with a non-constant dissipation coefficient are in better agreement with the experimental data. Furthermore, the difference between the results of two models for compound nuclei with low fissile parameter is low whereas, for heavy compound nuclei, is high.

System size dependence in backward relativistic hadron production in pA and AA collisions

In this comprehensive study the multiplicity characteristics of the backward emitted relativistic hadron (shower particle) through hadron-nucleus and nucleus-nucleus are overviewed in three dimensions. These dimensions are the projectile size, target size, and energy. To confirm the universality in this production system, wide ranges of system size and energy (Elab ∼ 2.1 A up to 200 A GeV) are used. The multiplicity characteristics of this hadron imply a limiting behavior with respect to the projectile size and energy. The target size is the main effective parameter in this production system. The exponential decay shapes is a characteristic feature of the backward shower particle multiplicity distributions. The decay constant changes with the target size to be nearly 2.02, 1.41, and 1.12 for the interactions with CNO, Em, and AgBr nuclei, respectively, irrespective of the projectile size and energy. While the backward production probability and average multiplicity are constants at different projectile sizes and energies, they can be correlated with the target size in power law relations.

Role of Exposure and Recovery Transients in Classification of Gases/Odors With Thick Film Sensor Array

In the present study, the effect of exposure (falling transients) and recovery (rising transients) responses of thick film gas sensor array on the classification and quantification accuracy of gas sensing system has been studied. The exposure and recovery data were extracted from the already published dynamic responses of a thick film gas sensor array. These datasets were individually fed to the multilayer feed-forward neural network with back propagation (BPNN) algorithm. The classification accuracy obtained for exposure responses was 81.2% while 84.3% for recovery responses. The same trend was obtained after applying principal component analysis, and our newly proposed average slope multiplication (ASM) feature techniques for data preprocessing. ASM transformed data showed 93.7% and 95.8% classification accuracy for exposure responses and recovery data, respectively. The simultaneous quantification results also followed the same trend, where ASM transformed data provided maximum 89.6% and 91.6% accuracy for exposure and recovery data, respectively, with relatively very less number of epochs required for network learning with simpler neural architecture. Thus, recovery or response readings alone can be used with the proposed ASM feature technique to get promising results in gas identification and/or quantification system. This can reduce data complexity, save computational time and, thus, can help in realizing real time gas sensing systems.

Multiplikácia Acer davidii ssp. grosseri (Pax) De Jong v podmienkach in vitro

Experimental works were focused on creation of optimal protocol forAcer davidiissp.grosserishoots multiplication. As the basic medium we used MS (Murashige α Skoog) culture medium enriched by cytokinins TDZ (Thidiazuron) and BAP (6-Benzylaminopurine) in different concentrations. There were used single nodal segments from four years old mother plants in experiments. Experiments were established in the middle of June in the phase of rapid growth of shoots. Cultivation conditions were: 21°C, light intensity 40 μmol . m−2. s−1, period of light 16 hours during the day. The reactions of explants were evaluated after six and twelve month. The results were statistically analysed. The explants ofAcer davidiissp.grosserireacted differently on hormonal regulation. The lowest multiplication activity of explants was found out on MS culture medium enriched by 2,6 μM BAP. The average shoot multiplication on MS + 0,5 μM TDZ culture medium was 1,2. Multiplication 1,49 shoot per explants was found out on MS + 2,6 μM BAP + 0,5 μM TDZ. On the basic MS medium 1,35 shoots per explants multiplicated. In spite of positive influence of application of TDZ and BAP on shoot multiplication the results compared with multiplication on MS medium were statistically insignificant.

Target dependence of clan model parameter in 84 Kr 36 – Emulsion interactions at 1 GeV per nucleon

This article focusses on the study of clan model parameters and their target dependence in light of void probability scaling for heavy (Ag and Br) and light (C, N and O) groups of targets present in nuclear emulsion detector using 84Kr36 at ∼1 A GeV. The variation of scaled rapidity-gap (rap–gap) probability with single moment combination has been studied. We found that experimental points lie approximately on the negative binomial distribution (NBD) curve, indicating a scaling behaviour. The increase in average clan multiplicities ( $\bar {N}$ ) for interactions with the pseudorapidity interval (Δη) was also observed. The values of $\bar {N}$ for AgBr targets are larger than those for C/N/O target and also average number of particles per clan ( $\bar {n}_{\mathrm {c}}$ ) increases with increase in pseudorapidity interval. We further observed that for a particular target, the average number of particles per clan ( $\bar {n}_{\mathrm {c}}$ ) increases with an increase in the size of projectile nucleus.

Properties of prompt-fissionγrays

In a Monte Carlo Hauser-Feshbach statistical framework, we describe spectra, average multiplicities, average energy, and multiplicity distributions of the prompt $\ensuremath{\gamma}$ rays produced in the thermal neutron-induced fission of $^{235}\mathrm{U}$ and $^{239}\mathrm{Pu}$, and the spontaneous fission of $^{252}\mathrm{Cf}$. Comparisons against recent experimental data show reasonable agreement in all cases investigated, after adjustment of the initial spin distribution in the fission fragments. In particular, when we include in the calculation the Doppler broadening we obtain a qualitatively good description of the measured low-energy spectra, where contributions from collective discrete transitions in specific fragments can be identified. At higher energies, both the calculated neutron and $\ensuremath{\gamma}$-ray spectra are softer than experimental data. The impact of selected model parameters on the prompt neutron and $\ensuremath{\gamma}$-ray spectra is analyzed. Finally, we present the prompt $\ensuremath{\gamma}$ spectrum and multiplicity distribution for the neutron-induced fission of $^{235}\mathrm{U}$ for 5.5 MeV neutron incident energy, just below the threshold for second-chance fission.

Reminiscences of Wit Busza and 41 years of [formula omitted] physics

One of the more memorable (and easiest) proposal to deal with when I served on Bob Wilson’s Program Advisory Committee at NAL (Now Fermilab) from 1972 to 1975 was Proposal-178, “A study of the average multiplicity and multiplicity distributions in hadron–nucleus collisions at high energies”, with only 4 authors, Wit Busza, Jerry Friedman, Henry Kendall and Larry Rosenson, as presented at the PAC meeting by Wit. What I remember was that he discussed only ONE 5 inch photomultiplier with a Cherenkov radiator in the beam to make this measurement of production of charged particles with angles up to 30° in various nuclei, 40 h requested. This turned out to be a “seminal” experiment leading to the Wounded Nucleon and other participant models. Subsequent p(d)+A experiments from the AGS to RHIC, as well as alpha–alpha measurements at the CERN-ISR, will be discussed together with the various ‘participants’ that they revealed.

On moments of the multiplicity events of slow target fragments in relativistic Sulfur-ion collisions

A detailed study on the multiplicity characteristics of the slow target fragments emitted in relativistic heavy-ion collisions has been carried out at E Lab = 3.7 A and 200A GeV using 32 S projectile. The beam energy dependence of the black particles produced in the full phase space of 32 S -emulsion (32 S -Em) interactions on the target size in terms of their moments (mean, variance, skewness and kurtosis) is investigated. The various order moments of target fragments emitted in the interactions of 32 S beams with the heavy ( AgBr ) target nuclei are estimated in the forward (FHS) and backward (BHS) hemispheres. The investigated values of ratio of variance to mean at both energies show that the multiplicity distributions (MDs) are not Poissonian and the strongly correlated emission of target fragments are in the forward directions. The degree of anisotropic fragment emission and nature of correlation among the emitted fragments are investigated. The energy dependence of entropy is examined in both hemispheres. The entropy values normalized to average multiplicity are found to be energy independent. Scaling of MD of black particles produced in these interactions has been studied to verify the validity of scaling hypothesis via two scaling (Koba–Nielsen–Olesen (KNO)-scaling and Hegyi-scaling) functions. A simplified universal function has been used in each scaling to display the experimental data.

Even–odd effects in prompt emission in fission

Abstract Compared to the extensively studied proton even–odd effects in fission fragment distributions, the even–odd effects in prompt emission received less attention. In this context the present paper is focusing on the even–odd effects (in both Z and N) appearing in prompt neutron and gamma ray emission. The study of even–odd effects in the prompt emission of four fissioning nuclei with even Z and even N, 233,235U( n th , f ), 239Pu( n th , f ) and 252Cf(SF), shows that these effects are mainly due to the Z even–odd effects in fragment distributions and charge deviations and the N even–odd effect in average neutron separation energies. The most pronounced even–odd effect in prompt emission is for the prompt neutron multiplicity. The average multiplicity as a function of Z, ν ( Z ) , has a sawtooth shape and exhibits a visible staggering for asymmetric fragmentations. The size of the global even–odd effect in prompt neutron multiplicity shows a decrease with increasing fissility. The N even–odd effect in average neutron separation energy influences the global even–odd effect in prompt neutron multiplicity often in an opposite way compared to the Z even–odd effect. The average prompt neutron multiplicity as a function of TKE shows an increase of the Z even–odd effect with increasing TKE and this effect is decreasing for heavier fissioning systems. The Z even–odd effects in the average prompt γ-ray energy and the average prompt neutron energy have comparable sizes and are lower than the even–odd effects in prompt neutron multiplicity. Different average prompt emission quantities (as a function of A, of Z, of TKE and total average ones)—being dependent on fragment distributions—are affected by the even–odd effects in Y ( A , Z , TKE ) . The N even–odd effect in neutron separation energy and the Z even–odd effect in the charge deviation enter the primary multi-parametric matrices of prompt emission quantities (e.g. ν ( A , Z , TKE ) ) which are not depending on fragment distributions.

Self-similarity of Low-p T cumulative pion production in proton-nucleus collisions at U70

The data on inclusive momentum spectra of π± mesons produced in p + A collisions over the range pL =15–65 GeV/c and θlab = 159° at U70 are analyzed in the framework of z-scaling approach. Self-similarity of the pion production in the low-pT cumualtive region is verified. Scaling function ψ(z) for Be, C, Al, Ti, Mo, W nuclei is constructed. It is expressed via the invariant cross section and the average multiplicity density of charged particles. Results of the analysis are compared with data obtained by J. Cronin, R. Sulyaev, and D. Jaffe groups at pL = 70, 400 GeV/c, pT > 1 GeV/c and θcms − 90°. A microscopic scenario of p + A interactions in terms of momentum fractions x1, x2 is discussed. Indication on self-similarity of the low-pT cumulative pion production in p + A collisions was found. Universality of the shape of the scaling function is used to predict inclusive cross sections of π+ and π− pions produced in p + A collisions on Be, C, Al, Ti, Mo, W targets in the deep-cumulative region (x2 ≫ 1/A).

Self-similarity of high-p T cumulative hadron production in p + A collisions at high energies at U70

New data on inclusive transverse momentum spectra of charged hadrons produced in p + A collisions at U70 are analyzed in the framework of the z-scaling approach. Self-similarity of the hadron production in the high-pT cumualtive region is verified. Scaling function ψ(z) for C, Al, Cu, W nuclei is constructed. It is expressed via the invariant cross section and the average multiplicity density of charged particles. Results of analysis are compared with the data obtained by J. Cronin, R. Sulyaev and D.Jaffe groups. Self-similarity of the hadron production in p + A collisions over a wide kinematical range is verified. A microscopic scenario of p + A interactions in terms of momentum fractions x1, x2 is discussed. Indication on self-similarity of the high-pT cumulative hadron production in p + A collisions over a wide kinematical range has been found. Based on the universality of the shape of the scaling function the inclusive cross sections of h− and h+ hadrons produced in p + A collisions on C, Al, Cu, W targets in the high-pT deep-cumulatice region are predicted.