Study of Clusters by Rapidity Interval Method at 24 GeV Proton-Nucleus Interaction in Emulsion

We present here the analysis of the distribution of rapidity intervals in Proton-Nucleus interactions at 24 GeV/c in emulsion. The statistics of the rapidity intervals Δ_{k, n} is discussed in terms of Multiperipheral model. The application of such a method is very useful for the analysis of clusterization phenomenon in individual events. The correlation between neighbouring particles in rapidity is observed in small multiplicity events while multiple correlation is observed in high multiplicity events.     

Charged-particle multiplicity distributions in different rapidity windows in 800 GeV proton-nucleus interactions

Multiplicity distributions of charged particles produced in interactions of 800 GeV protons with emulsion nuclei in various rapidity windows are presented. The data is also analyzed separately for the forward and the backward hemispheres, for rapidity windows of different widths. It is found that the Negative Binomial Distribution (NBD) describes well the multiplicity distribution of secondary particles in various rapidity windows and also in both the hemispheres. We have compared the NBD parameters, in both the hemispheres, at 200 GeV and 360 GeV, with those at 800 GeV. The behaviour of NBD parameters in rapidity windows of different widths and for different targets has also been studied. Received: 30 August 2001 / Accepted: 28 January 2002     

Momenta and rapidity characteristics of the multiparticle production in 50 GeV/c π −-Emulsion collison

The momenta and rapidity characteristics of the particles produced in 50 GeV/c π ⁻-collision with emulsion nuclei have been studied with an emulsion stack exposed under a pulsed magnetic field. The longitudinal rapidity plots suggest that leading pion is attenuated strongly when passing through a heavy nucleus. The average net charge 〈N _s ⁺ −N _s ⁻ 〉 produced in the final state of the reaction rises rapidly from a negative to a positive value atN _h ⩽1 and attains a constant value⋍0.60±0.08 at allN _h ⩾7.     

Unintegrated gluon distributions and Higgs boson productionin proton-proton collisions

Inclusive cross sections for Higgs boson production in proton-proton collisions are calculated in the formalism of unintegrated gluon distributions (UGDFs). Different UGDFs from the literature are used. Although they were constructed in order to describe the HERA deep-inelastic scattering F₂ data, they lead to surprisingly different results for Higgs boson production. We present both the two-dimensional invariant cross section as a function of Higgs boson rapidity and transverse momentum, as well as the corresponding projections on rapidity or transverse momentum. We quantify the differences between different UGDs by applying different cuts on interrelations between the transverse momentum of the Higgs and the transverse momenta of both fusing gluons. We focus on the large rapidity region. The interplay of the gluon-gluon fusion and weak-boson fusion in rapidity and transverse momentum is discussed. We find that above p_t ∼ 50–100 GeV the weak-gauge boson fusion dominates over gluon-gluon fusion. PACS. 12.38.Bx,12.38.Cy,13.85.Qk,14.70.Hp,14.80.Bn     

Impact parameter study in multiparticle production at 70 GeV/c

This paper presents a study of the experimental lower boundb _L, on the root-mean-squared impact parameter of the multiparticle production in 70 GeV/c p-nucleon interaction. It has been observed that theb _L decreases with increasing final state multiplicity (n) at this fixed energy. The results are in good agreement with those of other authors.The authors would like to thank Prof. K. D. Tolostov of Dubna, U.S.S.R. for kindly supplying the exposed emulsion plates.     

AnomalousE1 conversion in octupole-deformed nuclei and muon shake-off in prompt fission

It has been shown that the coexistence of octupole and quadrupole deformation in nuclei gives rise to strong penetration effects in internal conversion for theE1 transitions. This idea has been applied for evaluating the muon shake-off probabilityW _sh. The value obtained,W _sh/–0.5% per prompt fission, is in good agreement with the experimental result. Possibilities for further experimental studies of this effect are discussed.The author would like to acknowledge fruitful discussions of the problem together with Prof. Yu.P. Gangrsky, Dr. V. Yu. Denisov and Prof. D.F. Zaretsky. He is also grateful to Prof. G.Ye. Belovitsky, Prof. P. David and Dr. Ch. Rösel for discussions of the experimental situation. This work was completed at the University of Bonn in the frame of a fellowship from the Heinrich Hertz Foundation.     

An application of Lorentz invariant kinematical analysis to proton-nucleus collision at 70 GeV/c

The analysis of data obtained from 70 GeV proton-nucleus interactions in emulsion is presented in a manner suitable for observation from all Lorentz frames. The results of the analysis clearly indicate the production of pions due to the pionisation process.The authors are grateful to Prof. K. D.Tolstov of JINR (Dubna), U.S.S.R., for supplying the irradiated plates.     

Two Parton Shower Background for Associate <Emphasis Type="Italic">W</Emphasis> Higgs Production

The estimates of the background for the associate W Higgs production, which stems from the two parton shower production, leads to a background which is of the order of the signal for the non-perturbative contribution. In the perturbative approach the background turns out to be small. This background does not depend on the rapidity difference between the W and the pair, while the signal peaks when the rapidity difference is zero. Detailed calculations for the enhanced diagrams’ contribution to this process are presented, and it is shown that the overlapping singularities, being important theoretically, lead to a small contribution for the LHC range of energies.     

Energy dependence of the fast fragment of the target nucleus in high energy hadron-nucleus interaction

This paper presents an extensive study on the dependence of the mean number of the fast fragment of the target nucleus n _g on the incident beam energy in proton-nucleus interaction in emulsion in the range 6·2E ₀400 GeV/c. It has been observed that n _g decreases in the range 6·2E ₀200 GeV/c, then increases and attains an approximately steady value up to 400 GeV/c. It is very difficult to explain this behaviour with the help of the existing nuclear production models.The author would like to thank Prof A. J. Herz (CERN), Prof. K. D. Tolostov (Dubna, U.S.S.R.), Prof. P. L. Jain (State University of New York, U.S.A.), Prof. G. Giacomelly (Italy) for kindly supplying the exposed emulsion plates.     

Target mass dependence of mean slow particle multiplicity in high energy hadron-nucleus interaction

This work presents a study on the dependence of mean slow particle multiplicity (N_h) on the mass numberA of the target nucleus for a wide range of target mass and energy. It has been shown that this dependence can be best expressed by the relation N _h= 0.57A^0.61.The author would like to express his indebtedness to Prof. A. Herz (CERN), Prof. K. D. Tolostov (JINR), Prof. R. Wilkes (University of Washington) for kindly supplying the exposed emulsion plates.     

Strong-symmetry-breaking limit of SU(3) Skyrme model and bound-kaon approach to strangeness

The semi-leptonic weak decays of hyperons are investigated in the Skyrme model. The vector currents for strangeness-changing processes are shown to have a very similar structure in the strong-symmetry-breaking limit in the SU(3) collective-coordinate method, proposed by Yabu and Ando, with those in the bound-kaon approach to strangeness by Callan and Klebanov. It is also shown that the quite differentN _c dependence between them becomes also to coincide with each other in the limit.Dedicated to Prof. Erich Schmid on the occasion of his 60th birthday     

RING-LIKE EVENT OBSERVED IN SUPERHIGH ENERGY INTERACTION AND PHASE TRANSITION

The kinematical analysis of the ring-like event observed in mountain emulsion chamber shows that this kind of events might relate to the multi-particle production within a narrow rapidity interval of the fragmentation region in the superhigh energy interactions, therefore possibly relate to the phase transition in the nucleus-nucleus interaction. The air cascade showers induced by superhigh energy nucleus-nucleus interactions are simulated by a transition model. Under the condition of the emulsion chamber experiment, the ring-like event is obtained.     

Charged particle multiplicity distributions in restricted rapidity intervals inZ0 hadronic decays

The multiplicity distributions of charged particles in restricted rapidity intervals inZ ⁰ hadronic decays measured by the DELPHI detector are presented. The data reveal a shoulder structure, best visible for intervals of intermediate size, i.e. for rapidity limits around ±1.5. The whole set of distributions including the shoulder structure is reproduced by the Lund Parton Shower model. The structure is found to be due to important contributions from 3-and 4-jet events with a hard gluon jet. A different model, based on the concept of independently produced groups of particles, clans, fluctuating both in number per event and particle content per clan, has also been used to analyse the present data. The results show that for each interval of rapidity the average number of clans per event is approximately the same as at lower energies.This paper is dedicated to the memory of Léon Van Hove     

Canonical realizations of classical lie algebras

We construct sets of canonical realizations for all classical Lie algebras (A _n ,B _n ,C _n ,D _n ). These realizations depend ond parameters,d=1, 2, 3,...,n; all Casimir operators are realized by multiples of identity. For most of the real forms of these algebras we give sets of realizations which are, moreover, in well-defined sense skew-Hermitian. Further we study extremal cases of the presented realizations. The realizations with minimal numbers of canonical pairs are discussed from the point of view of general results concerning minimal realizations. On the other hand, a connection is found between our maximal realizations ofA _n and the Gel'fand-Kirillov Conjecture.The authors would like to thank Prof. A.Uhlmann for his kind interest in this work. They are very grateful to Prof. A. A.Kirillov and Prof. D. P.Zhelobenko for helpful discussions and to Prof. J.Dixmier for his informative letter concerning the problem mentioned in Sect. 5.One of the authors (W. L.) thanks Prof. I.Úlehla for the hospitality at the Nuclear Center of the Charles University, Praha.     

Proton distributions in the target fragmentation region in proton-nucleus and nucleus-nucleus collisions at high energies

We present measurements of the rapidity and transverse-momentum distributions of the protons emitted in S+W, O+W, andp+W reactions at 200 GeV/A around the target rapidity (y=1). The rapidity density rises linearly with the transverse energy for all three systems, but the slope forp+W is much steeper than for O+W and S+W. The rapidity density forp+W is much higher than predicted by summing single nucleonnucleon collisions without any nuclear effects, indicating substantial rescattering of the produced particles. The predictions of the VENUS 3 model, including rescattering, show reasonable agreement with the data for all three systems. We do not have evidence for a strong collective flow of the outgoing particles.     

Production of helium fragments in197Au-emulsion collisions at 10.6 A GeV

We present a systematic analysis on the helium projectile fragments produced from 10.6 A GeV¹⁹⁷Auemulsion interactions in an experiment conducted at the Brookhaven AGS. Total charge changing and partial production cross-sections are measured experimentally on the basis of helium multiplicity. The multiplicity distribution of helium fragments which are produced collectively obey a KNO scaling. The transverse momentum distribution of these particles indicates that they are produced from two different independent sources.We are thankful to the BNL technical staff and specially to Dr. D. Beavis for his help in the exposure of emulsion stacks. Thanks are due to Profs. Y. Takahashi and G. Romano for their help in the preparation and development of the emulsion stacks. We appreciate the discussions with Prof. H. Stocker and J. Aichelin. This work was supported by D.O.E. under Grant No. DE-FGO2-90ER 40566.     

Transverse Momentum and Rapidity Distributions of Charged Secondaries Emitted in Proton Nucleon Inelastic Interactions at 69 Gev/c

This paper deals mainly with the study of the transverse momentum and the rapidity distributions of the charged secondaries emitted in the proton-nucleon inelastic scattering at 69.0 Gev/c. Our sample consists of 300 proton-nucleon inelastic events, found amongst 1887 stars attributed to inelastic interactions of 69 Gev/c protons with emulsion nucleons and nuclei, in 768 meters of proton tracks. Our plates were obtained from the JINR Dubna, USSR. Accurate coulomb scattering mesuremments were performed on about 300 emitted charged secondaries to determine their momenta. The average value of the transverse momentum 〈P_t〉 of the charged secondaries emitted in p-nucleon, p-p, and p-n interactions at 69 Gev/c are 0.329 ± .020, 0.317 ± .029 and 0.332 ± .027 Gev/c respectively. The 〈P_t〉 value is almost constant for primary energies from above 6.0 Gev up to cosmic ray energies. It slightly decreases as the charged multiplicity increases as expected according to the statistical models. It is found that the linear and the Hagedorn distribution (LD and HD), both fit the experimental transverse momentum distributions better than the Boltzmann distribution (BD) in the energy range from above 6.0 Gev up to cosmic ray range. In all the cases of p-nucleon, p-p and p-n interactions at our energy, it has been found that the HD gives 〈P_t〉 values nearer to the experimental results than the LD. The different order moments of the experimentally obtained transverse momentum distribution strongly confirms the applicability of the generalized HD at our energy and in the range of interaction from above 6.0 Gev up to cosmic ray ranges. The temperature of the interaction volume was determined to be 140 Mev in agreement with the Hagedorn model which predicts it to be of the order of one pion mass. The variation of 〈P_t〉 with the angle of emission in the C.M. system and the momentum distribution in the C.M. system were studied in view of the isobar model. A study of the rapidity (Y) distribution confirmed an energy independent behaviour especially for slow emitted pions both in the projectile and the target fragmentation regions in accordance with the limiting fragmentation hypothesis.     

J/<Emphasis Type="Italic">ψ</Emphasis> production measurements by the PHENIX experiment

Quarkonia suppression is considered to be one of the key probes of the Quark Gluon Plasma (QGP) created in heavy ion collisions. The PHENIX experiment has measured J/ψ production in a variety of colliding systems. Measurements made in p+p collisions show good agreement with pQCD predictions and serve as baseline for other systems at the same collision energy. The cold nuclear matter contribution to the suppression is constrained through measurements in d+Au collisions. In Au+Au, the suppression observed at mid rapidity is smaller than that at forward rapidity, a tendency opposite to what is expected from the higher gluon density at mid rapidity. The results will be presented and discussed in this article.     

New representation for energy-momentum and its applications to relativistic dynamics

In this paper we introduce the concept counterpart of rapidity and define energy and momentum of the relativistic particle as functions of the counterpart of rapidity. Formulae of the relativistic mechanics defined in such a way are regular near the zero-mass and speed of light state. This representation admits to attain a correct limit of the formulae of the relativistic mechanics, including the Dirac equation, at zero-mass point and explains violation of the parity at this state. On the other hand, the representation for energy-momentum can be realized as a mapping from the massless state onto the massive one which looks like a “q deformation”. Hypothesis on quantization of the energy-momentum and the velocity near the light speed is suggested. The group of transformations using the counterpart of rapidity as a parameter of transformation is constructed.     

A note on matrix elements of finiteU(n) transformations

Matrix elements of finite transformations of the group U(n) in an arbitrary unitary irreducible representation of U(n) are discussed and a technique for their determination is presented. As a by-product a recursion relation for a special Racah coefficient of U(n) is obtained.Work supported by the Comisión de Energia Nuclear, Mexico.Almost the whole work was done at theInternational Centre for Theoretical Physics, Trieste, Italy.We would like to thank Prof. Abdus Salam and Prof. P. Budini as well as the International Atomic Energy Agency for their hospitality at the I.C.T.P., Trieste. One of us (J. F.) would like to express his thanks to Prof. M. Moshinsky for helpful comments.