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 p _L =15–65 GeV/c and θ _lab = 159° at U70 are analyzed in the framework of z-scaling approach. Self-similarity of the pion production in the low-p _T 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 p _L = 70, 400 GeV/c, p _T > 1 GeV/c and θ _cms ? 90°. A microscopic scenario of p + A interactions in terms of momentum fractions x ₁, x ₂ is discussed. Indication on self-similarity of the low-p _T 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 (x ₂ ? 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-p _T 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 x ₁, x ₂ is discussed. Indication on self-similarity of the high-p _T 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-p _T deep-cumulatice region are predicted.     

Inclusive production of neutral pions in hadronic Z decays

A measurement of the inclusive production of π⁰ mesons in hadronic Z decays is presented and compared to Monte Carlo model predictions. The analysis is based on approximately 2 million hadronic events recorded with the ALEPH detector at LEP at a centre-of-mass energy of ?s = 91.2 GeV. Neutral pions are reconstructed using photons measured in the electromagnetic calorimeter and photons from conversion pairs. The inclusive π⁰ momentum spectrum is measured in the range 0.025 < x _p = p/p _beam < 1. In this range the number of π⁰ per hadronic Z is found to be 4.80 ± 0.07(stat) ± 0.31(sys). The differential inclusive π⁰ cross section is also measured as a function of transverse momentum with respect to the event plane (p _T ⁱⁿ and p _T ^out ).     

Hadronic ϕ production and the lund model for lowp T interactions

Experimental results on inclusive ? production are compared with the Lund model for lowp _T hadronic interactions. The data is based on a sample of 600,000 ? mesons in the kinematic rangep _T <1.0 (GeV/c)² and 0.0<x _F<0.4, produced in π^±,K ^±,p and \(\bar p\) Be interactions at 100 GeV/c and 120 GeV/c incident momentum. The Lund model reproduces the shapes of the longitudinal differential cross sections reasonably well, but the relative cross sections for incident, π,K andp show a discrepancy with the data.     

Photoproduction of large transverse momentum mesons and production of large-pT photons and leptons in proton-proton collisions

The photoproduction of large transverse momentum mesons is examined in a leading particle model using the techniques of the covariant parton model. In the leading particle model the large-p_T meson is produced in a high-energy, wide-angle scattering: γ + q → M + q. Numerical results such as inclusive cross sectioons, angular distributions and particle ratios are presented for the pseudoscalar mesons. The Landshoff-Polking-horne quark-fusion model is then applied to the production of large transverse momentum photons and leptons in proton-proton collisions. In the lepton case this model differs from the usual Drell-Yan mechanism in that the lepton pair has a small invariant mass but comes from a large-p_T virtual photon.     

A study of high transverse momentum π0's at ISR energies

We present a study of the transverse momentum spectrum of π⁰'s produced at c.m. angles θ = 90° and 53° in pp collisions at √s = 23.6, 30.8, 45.1, 53.2, and 62.9 GeV. The experiment was performed with a lead-glass detector. The data can be described with the usual parametrization $\text{p}{}_{\mathrm{<mtext>T</mtext>}}{}^{\mathrm{?n}}\text{?;(x}{}_{\mathrm{<mtext>T</mtext>}}\text{, θ)}$, with n = 7.2 ± 0.2. Comparison between the 90° and 53° data further indicates no appreciable dependence on θ, at least for x_T < 0.3. Two-particle inclusive cross sections for π⁰'s produced alongside are also presented. They are observed to have a dependence upon the transverse momentum of the dipion similar to that of single-particle cross sections and with the same value of n. Two-photon decays of η mesons are observed between 3 and 4 GeV/c transverse momentum with a production cross section half of that of π⁰.     

Production of pseudoscalar mesons in 300 GeV central π+ N collisions

The exculsive production of π⁰, η, and η′ mesons in π⁺ N central collisions has been studied with 300 GeV incident pions. The experiment has been performed at the CERN SPS. The gammas from decaying mesons were detected in the hodoscope multiphoton spectrometer GAMS-4000. The measured differential cross sections show a plateau in the longitudinal momentum interval 0.1F<0.3.     

Study of inclusive production of π± and protons in\bar p p interactions at 32 GeV/c

Results are presented on the inclusive production of π^± mesons and protons in \(\bar p\) p interactions at an incident antiproton momentum of 32 GeV/c in the MIRABELLE bubble chamber, based on a sample of 55,000 inelastic events. The spectra of π⁺(π^?) andp( \(\bar p\) ) are separated in the whole kinematically admitted region of phase space by a statistical method. The semi-inclusive and inclusive cross sections and the main average characteristics of π andp production are calculated. The invariant differential cross sections are studied as functions of the Fevnman scaling variablex, the rapidity and the transverse momentum. Thex distribution of π^± mesons in the proton fragmentation region does not show any significant contribution from quark exchange or annihilation processes. A possible contribution of hard quark scattering on mesons or baryons is observed for large transverse momenta.     

High transverse momentum π0 production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for π⁰ production by π^? and π⁺ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx _F ranges covered are 4.0<p _T <7.0 GeV/c and ?0.45<x _F <0.6 respectively. The data are compared with leading order QCD calculations.     

High transverse momentumη production in π− p, π+ p,andpp interactions at 280 GeV/c

The inclusive cross sections for η production by the interactions of 280 GeV/c momentum π^?, π⁺, and proton beams in hydrogen have been measured. The kinematical range covered is ?0.45<x _F <0.45, and 4.0<P _T <7.0 GeV/c for Feynmanx _F and transverse momentum respectively. The η to π⁰ cross section ratios are given for the three reactions. The ratio of π^? p to π⁺ p cross sections for η production in the above kinematic ranges is 1.22±0.08±0.11.     

Nuclear mass number dependence of inclusive pion production by pions and protons at 4.3GeV/c

The inclusive production of π⁺ for 0.4≤p_T<1.0 GeV/c in pion-nucleus and proton-nucleus collisions at 4.3 GeV/c was measured. A strong A-dependence of the cross sections at high p_T is observed to be persistent in the low energy region. The ratio of the cross sections for proton-nucleus and pion-nucleus collisions is also observed to be compatible with the quark-parton picture, for p_T>0.6 GeV/c.     

High statistics inclusive ϕ meson production at SPS energies

Inclusive ? meson production has been measured for 100 GeV/c and 200 GeV/c incident π^?, \(\bar p\) andK ^?, and for 120 GeV/c and 200 GeV/c incident π⁺,p andK ⁺, using a Be target. A total of 630,000 ? mesons has been recorded in the kinematic range 0<x _F <0.4. Presented are the differential cross sectionsdσ/dx _F anddσ/dp _T ². The longitudinal momentum distributions show that the strange valence quarks of the incidentK mesons play an important role in ? meson production, even at smallx _F . The decay angular distribution of the ? meson is evaluated in the Gottfried-Jackson frame and is expressed in the elements of the density matrix. There is a small but significant cos² θ _GJ dependence for smallp _T , which decreases for increasingp _T .     

Neutral transverse momentum spectra in 60 and 200A·GeV16O+nucleus and proton+nucleus reactions

Transverse momentum (p _T) distributions fo inclusive photons and neutral pions at midrapidity are measured with a lead glass calorimeter in 60 and are measured with a lead glass calorimeter in 60 and 200A·Gev¹⁶O+nucleus and and proton+nucleus reactions. Inclusive photon distributions are compared for central and peripheral reactions. The degree of centrality is determined either from the charged particle multiplicity or from the remaining projectile energy in the forward direction. Deviations from a nucleus+nucleus interaction model based upon linear extrapolation from p+p reactions are observed in central¹⁶O+Au data. The variation of theaverage transverse momentum is investigated as function of centrality. The target-mass and energy dependence of π⁰ p _T distributions are presented. For¹⁶O+Au a change of slope in these distributions is observed atp _t ≈0.8 GeV/c compatible with hydrodynamic expansion models.     

High transverse momentum prompt photon production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for prompt photon production by π^? and π⁺ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx _F ranges covered are 4.0<p _T <7.0GeV/c and ?0.45<x _F <0.55 respectively. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed.     

Investigation of the Balitsky-Fadin-Kuraev-Lipatov dynamics of gluon distributions in the inelastic production of <Emphasis Type="Italic">J/ψ</Emphasis> mesons at the HERA collider

The inelastic photo-and electroproduction of J/ψ mesons at the HERA collider are considered within the semihard (k _T -factorization) QCD approach and the color-singlet model. The total, differential, and double-differential cross sections for the inelastic production of J/ψ mesons are investigated versus the Pomeron intercept Δ, which is the basic parameter of low-x physics; also studied here is the spin alignment parameter α versus the square of the transverse momentum, p _ψT ² , and the variable z. The theoretical results obtained in the present study are compared with the latest experimental data of the H1 and ZEUS Collaborations. It is shown that experimental investigations of the polarization properties of J/ψ mesons at the HERA collider for Q²<1 GeV² may provide an additional test of the Balitsky-Fadin-Kuraev-Lipatov dynamics of gluon distributions.     

Inclusive photon and π0 production inK + p interactions at 70 GeV/c

Inclusive and semi-inclusive cross sections and distributions of γ's and π⁰'s inK ⁺ p interactions at 70 GeV/c are presented. The results are compared to other experiments and to the Lund model for low-p _T hadron collisions.     

Inclusive production of vector and tensor mesons in antiproton-proton annihilation and non-annihilation interactions at 9.1 GeV/c

Cross sections have been determined for the inclusive production of vector $\text{(?}{}^0\text{, ω,}\text{K}{}^1\text{)}$ and tensor (f, A₂^±) mesons in $\text{p}\text{p}$ reactions at 9.1 GeV/c for both annihilation and non-annihilation processes. Distributions in the Feynman variable x and transverse momentum squared, p_T², have been examined for the ?⁰, ω and f mesons. The slopes for p_T² appear to be exponential and decrease with increasing particle mass for both annihilation and non-annihilation reactions, furthermore the slopes have consistently higher values for non-annihilation reactions. Comparisons with other data indicate that the ratio ?⁰/π^? is independent of antiproton momentum in annihilation processes.     

Transverse momentum distribution of lepton-pairs and hard interaction mechanism of constituents

The wide transverse momentum distribution of massive > -pairs produced in hadronic collisions is discussed on the basis of a hard interaction mechanism of constituents which relates it directly to the p^?8_T behaviour of inclusive meson distributions in hadronic collisions at large p_T.     

Large-pTπ0 production with pion beams and dominance of the subprocess quark + quark → baryon + antiquark

We compare the predictions of the subprocesses M + q → M + q, q + $\text{q}$ → M + M, q + q → B + q?, for large-p_Tπ⁰ inclusive production in π^?p collisions, with the data. Calculations performed with various models show, in a model independent way, that q + q → B + q? is dominant in pp collisions.     

Multiparticle azimuthal correlations of negative pions in nucleus-nucleus collisions

Multiparticle azimuthal correlations of ?? ^? mesons have been studied in dC, HeC, CC, CNe, MgMg, (d, He)Ta, CCu, CTa, and OPb collisions at momentum of 4.2, 4.5 GeV/c per nucleon within the standard transverse momentum analysis method of P. Danielewicz and G. Odyniec. The data were obtained by SKM-200-GIBS and Propane Bubble Chamber Collaborations of JINR. The axis has been selected in the phase space and with respect to this axis ?? ^? meson correlations were observed. The values of the coefficient of the correlations linearly depend on the mass numbers of projectile (A _P ) and target (A _T ) nuclei. The Quark-Gluon String Model satisfactorily describes the experimental results.