Multiplicity structure of the hadronic final state in diffractive deep-inelastic scattering at HERA

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type , where Y is a hadronic system with mass GeV and where the squared momentum transfer at the pY vertex, t, is limited to , is studied as a function of the invariant mass of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low . A model with soft colour interactions is also successful. Received: 27 April 1998 / Published online: 3 September 1998     

Multiplicity structure of inclusive diffraction in À+ p andK + p interactions at 250 GeV/c

Results on the multiplicity structure of diffractively excited meson and proton systems in À⁺/K⁺ p interactions at 250 GeV/c are presented for diffractive masses up to about 9 GeV. The energy dependence of the average charge multiplicity and the shape of the multiplicity distribution in terms of KNO-scaling and negative binomial distribution are investigated. The diffractive systems are compared toe ⁺ e ^–,lh and non-diffractivehh final states as suggested by modern approaches of the Pomeron-hadron collision. Systematic differences are found between diffractive meson and proton systems but also between diffraction and the reactions compared to.     

Calculation of the cross section of helium ionization by an electron impact with the formation of a helium ion in an excited state

The total cross sections of He and He⁺ ionization by an electron impact are calculated in the first Born approximation. Calculations of the matrix elements are carried out by the Fock-Dirac multiconfiguration relativistic method using an intermediate type of coupling with orthogonal functions of the initial and final states. A single-electron wave function of the continuous spectrum for an Auger electron is obtained using the Fock-Dirac single-configuration method. The results of the calculations performed with orthogonal and nonorthogonal wave functions of the initial and final states are compared. The ionization cross sections are calculated for cases in which a knock-on electron of the continuous spectrum is described by both the orthogonal and nonorthogonal wave functions with respect to the wave functions of the core electrons.     

Angular momentum dependence of the giant dipole resonance width in excited nuclei of mass

Gamma ray spectra in the energy range of 4–25 MeV were measured in the reaction ²⁸Si + ¹²⁴Sn at E(²⁸Si) 150 MeV in coincidence with low energy γ-multiplicities. The spectra were analysed using a simulated Monte Carlo CASCADE code. The centroid energy and width of the giant dipole resonance were extracted for various multiplicity windows. The average angular momentum and temperature of the final states populated after the giant dipole photon emission range from 25 and 1.5 MeV to 56 and 1.3 MeV, respectively. The extracted widths are almost constant for the lower multiplicity windows and show an increase of 1.4 MeV at the highest window. The nuclei are expected to be near the liquid drop regime and the experimental results are not inconsistent with the liquid drop behaviour.     

O 1s --> sigma* resonance in O2: inadequacy of only two exchange-split components

The O 1s-->sigma* transition below the O K-edge in O2 has been investigated by absorption, constant ionic state (CIS) experiments, and extensive configuration interaction calculations. CIS scans of the three lowest-lying final states reached in resonant Auger decay provide a wealth of information on energy range, symmetry, and spin multiplicity of the intermediate states with sigma* character. We conclude that the identification of only two exchange-split components is inadequate because a complex manifold of states with sigma* character exists with no unique energy difference between related states.     

Local distinguishability by projective measurement

This paper proves that a set of orthogonal pure states are indistinguishable by restricted local projective measurement and classical communication if the sum of their Schmidt ranks is larger than the dimension of their joint Hilbert space. This result is useful in determining the local distinguishability of quantum states and is stronger in some respects than that of Hayashi et al [Phys. Rev. Lett. 96, 040501]. In addition, it presents a new method to determine the local distinguishability of orthogonal states by projecting measurement operators into their subspaces.     

A study of charged particle multiplicities in hadronic decays of theZ0

We present an analysis of multiplicity distributions of charged particles produced inZ ⁰ hadronic decays. The results are based on the analysis of 82941 events collected within 100 MeV of theZ ⁰ peak energy with the OPAL detector at LEP. The charged particle multiplicity distribution, corrected for initial-state radiation and for detector acceptance and resolution, was found to have a mean n _ch=21.40±0.02(stat.)±0.43(syst.) and a dispersionD=6.49±0.02(stat.)±0.20(syst.). The shape is well described by the Lognormal and Gamma distributions. A negative binomial parameterisation was found to describe the shape of the multiplicity distribution less well. A comparison with results obtained at lower energies confirms the validity of KNO(-G) scaling up to LEP energies. A separate analysis of events with low sphericity, typically associated with two-jet final states, shows the presence of features expected for models based on a stochastic production mechanism for particles. In all cases, the features observed in the data are well described by the Lund parton shower model JETSET.deceased 25th March 1991     

Multiplicity studies and effective energy in ALICE at the LHC

In this work we explore the possibility to perform “effective energy” studies in very high energy collisions at the CERN large hadron collider (LHC). In particular, we focus on the possibility to measure in pp collisions the average charged multiplicity as a function of the effective energy with the ALICE experiment, using its capability to measure the energy of the leading baryons with the zero degree calorimeters. Analyses of this kind have been done at lower centre-of-mass energies and have shown that, once the appropriate kinematic variables are chosen, particle production is characterized by universal properties: no matter the nature of the interacting particles, the final states have identical features. Assuming that this universality picture can be extended to ion–ion collisions, as suggested by recent results from RHIC experiments, a novel approach based on the scaling hypothesis for limiting fragmentation has been used to derive the expected charged event multiplicity in AA interactions at LHC. This leads to scenarios where the multiplicity is significantly lower compared to most of the predictions from the models currently used to describe high energy AA collisions. A mean charged multiplicity of about 1000–2000 per rapidity unit (at η∼0) is expected for the most central Pb–Pb collisions at . In memory of A. Smirnitskiy     

On local parton-hadron duality

The multiplicity measure on colour-connected partonic states introduced in [1] is further generalized and we show how to partition the properties of the final state hadronic multiplicity distributions into one part depending upon the partonic cascade and one depending upon the fragmentation inside the Lund model framework. We also show the stability of the measure with respect to variations in the energy and the possible cascade cutoffs and investigate the approximations made in the analytical formulas by means of Monte Carlo simulated events.     

Multiplicity of dielectric relaxation times of dispersed ice microcrystals

Summary The multiplicity of relaxation times of the dielectric relaxation of water molecules in dispersed ice microcrystals has been studied by means of the thermally stimulated depolarization (TSD) current method. Using several experimental techniques offered by the TSD method we have shown that the relaxation mechanism is characterized by a continuous distribution of relaxation times with both the activation energy.W and the pre-exponential factorτ ₀ in the Arrhenius equation being distributed parameters. A linear relationship has been found to exist betweenW and lnτ ₀. The dielectric behaviour of ice emulsions has been found to resemble strongly in some aspects that of HF-doped ice and ice samples with high concentrations of crystal imperfections. The multiplicity of relaxation times has been explained by the interaction of intrinsic ionic defects with water molecules. Work supported in part by the Greek Ministry of Research and Technology.     

Z0能区正负电子湮没强子多重数分布的近泊松形式与肩状结构

对Z⁰能区91.2GeV正负电子湮没产生强子末态的事例,分别针对全喷注和双喷注在不同快度窗口的单、双半球空间内进行多重数分布的泊松拟合.根据/D参量及拟合度得到近泊松形式,与有关理论模型进行了比较,并讨论了与KNO无标度性的关系.分析了偏离泊松形式的有关参数与非独立粒子发射及关联强度之间的联系.利用JADE喷注分析法讨论了中心快度区的“肩状结构”.     

Hund's rule and the Z expansion for the energy,electron repulsion and electron nuclear attraction

A Z expansion is derived for the expectation values of the interelectronic repulsion energy and the electron-nuclear attraction energy in atomic states. The formalism, which is based on a non-relativistic hamiltonian, is applied to excited states in iso-electronic sequences. It appears that there are many cases where the state of the highest multiplicity has the larger expectation value for the interelectronic repulsion energy although it has a lower total energy.     

On the origin of approximate KNO scaling ine + e − annihilation

KNO scaling of the multiplicity distribution in hadronic final states was originally derived as a consequence of Feynman scaling. We show that in iterative models of hadron production in jets, incorporating Feynman scaling, KNO scaling obtains only in the limit when the width of the multiplicity distribution tends to zero. Within the context of the models currently employed to describee ⁺ e ^? annihilation into hadrons, the apparent KNO scaling observed is an accidental consequence of effects which violate Feynman scaling.     

Reactions with leading hadrons in meson-proton interactions at 250 GeV/c

Inelastic final states with one or two leading hadrons are studied in π⁺p and K⁺p interactions at 250 GeV/c. In reactions with two leading hadrons, the dependence of the average charge multiplicity of associated pions on their effective mass is essentially consistent with that observed in p?p and γγ-collisions, but differs from that obtained in e⁺e^? -annihilation. The multiplicity and (semi)inclusive characteristics of the π⁺-induced non-diffractive reactions are compared to predictions of current versions of the FRITIOF fragmentation model. We show that the hard-like sub-processes, essentially responsible for the production of leading hadrons with relatively large transverse momentum as well as for the relatively large multiplicity of associated pions, are not properly treated in the model.     

High-p jets in diffractive electroproduction

The diffractive production of high-p jets in deep-inelastic scattering is studied in the semiclassical approach. The p-spectra of and diffractive final states are found to be qualitatively different. For fina states, which are produced by ‘hard’ colour-singlet exchange, the p-spectrum is much softer than for final states, where the colour neutralization is ‘soft’. Furthermore, the two different final states can be clearly distinguished by their diffractive mass distributions.     

Odd-odd nuclei as the core-particle-hole systems and chirality

Odd-odd nuclei treated as core-particle-hole systems with various collective cores and various particle-hole configurations are investigated within the Core-Particle-Hole Coupling (CPHC) model. A new symmetry, called the S-symmetry, is identified as a combination of the α-parity of the collective core and the proton-neutron symmetry of the valence proton and neutron in particle-hole configurations involving single-particle states with the same quantum numbers. It is found that the S-symmetric odd-odd nuclei show signatures which are usually considered as fingerprints of nuclear chirality, namely doublet band structure with a particular pattern of electromagnetic transitions. Reported results imply that the rigid rotor with a symmetric valence proton-neutron configuration is only a special case of the system with the novel S-symmetry. Therefore, it is an open question whether the chiral fingerprints discussed so far identify uniquely the orthogonal coupling of angular momentum in the intrinsic system.     

Nuclear effects in photoproduction and leptoproduction where are they? Are they Negligible?

We discuss nuclear effects in hadronic final states in photoproduction and leptoproduction on nuclei. Whereas the final states in photoproduction and leptoproduction on free nucleons are similar, striking differences are predicted for the case of nuclear targets, the differences being largest in multiplicity correlations. Quantitative predictions are given for the cases of practical interest: photoproduction and muonproduction on emulsion nuclei, and neutrino-production in neon and propanefreon bubble chambers. Neutrino-production on nuclei is emphasized as offering the most direct test of the formation length hypotheses.     

Gamma decay after heavy ion reactions studied by first and higher order multiplicity measurements

First and higher order multiple coincidence rates have been measured for the γ-rays from ¹⁶O induced reactions on targets of ^148,150Nd at various bombarding energies. Average values and shape parameters for the γ-ray multiplicity distributions have been extracted from the data. The multiplicities are connected to angular momentum through complete fusion cross sections, and conclusions are drawn on spin distributions of entry states in the final nuclei as well as on the decay pattern from these states.     

Selection of jets in multihadron final states produced bye + e −-annihilation

Fore ⁺ e ^?-annihilations a procedure is described to select events of a given multiplicity of jets. The procedure is demonstrated by applying it to a Monte-Carlo sample ofe ⁺ e ^? multihadron final states. Selection of three jet events is shown to be somewhat better than more conventional techniques.     

Cross sections and multiplicity distributions for pp annihilations at 4.6 GeV/c

Channel cross sections have been determined for $\text{p}\text{p}$ annihilations into final states containing 3 to 9 pions at 4.6 GeV/c. The moments of both the charged and neutral pion multiplicity distributions are presented and model predictions are critically examined.