Regge Model Research Articles

Some General Consequences of Regge Theory for Pomeranchukon-Pole Couplings

Without reference to specific Regge models, and assuming only the validity of asymptotic Regge-pole expansions, we use unitarity and exact sum rules to draw conclusions concerning the couplings of the vacuum pole ${\ensuremath{\alpha}}_{p}(0)$. If ${\ensuremath{\alpha}}_{p}(0)<1$ we derive an upper bound on the triple-vacuum coupling. Assuming ${\ensuremath{\alpha}}_{p}(0)=1$ we prove either that the ($t=0$) Pomeranchukon-particle-Reggeon coupling vanishes for all Reggeon masses, or the ($t=0$) Pomeranchukon-Reggeon-Reggeon coupling vanishes. We also prove the vanishing of either the Pomeranchukon-Pomeranchukon-Reggeon vertex at zero mass, or the Mueller-like Pomeranchukon-Reggeon-particle-particle vertex, again all Reggeons at zero mass. Our model-independent technique is used to recover the Finkelstein-Kajantie result that the Pomeranchukon-Pomeranchukon-particle coupling vanishes for ${\ensuremath{\alpha}}_{p}(0)=1$; if ${\ensuremath{\alpha}}_{p}(0)<1$ an inequality is obtained for the coupling. The influence of Regge cuts is neglected.

Decay angular distributions of p π− states formed in diffraction dissociation of neutrons on carbon

We present decay angular distributions of the p π − system formed from the interactions of 25–30 GeV/ c neutrons on a carbon target. The data are studied as afunction of t′, which allows a partial separation of coherent and incoherent events. It is found that the coherent production goes substantially into p π − states with J ⩾ 3 2 and is consistent with pure J = 3 2 . We are not able to draw any firm conclusions about the question of helicity conservation from the data. There is no evidence for coherent production of the known I = 1 2 resonances. Comparison is made of the data with predictions of the Drell-Hiida-Deck and double Regge models. In their present form these models do not appear to give satisfactory descriptions of the data.

Polarisation in π−p → K° Λ° backward scattering at high energy

The sign of the polarisation in backward π −p → K° Λ° high energy scattering predicted in a parameter-free Regge model with exchange degenerate Σ α − Σ γ and Σ δ − Σ β poles. The sign prediction depends on (i) the sign of the Regge phase difference between Σ α Σ γ and Σ β Σ δ , which is 90°, (ii) the [SU (3)] sign of the Y ∗ resonance couplings determined experimentally in the crossed channel KN → πΛ , (iii) the simple connection between the sign of the non-flip/flip ratio and the parity of the exchanged baryon. The large magnitude of the experimental polarisation, ⋍ 100%, is explained naturally by the 90° difference in the Regge phase and the opposite sign of j−l = ± 1 2 for Σ αΣ γ and Σ βΣ δ .

Features of partial waves in πN charge-exchange scattering at 6 GeV/ c

From the result of amplitude analyses and Regge fits we try to determine the structure of the partial wave amplitudes in πN charge exchange. Significant high- J contributions to Im ⨍ ++ are which are in conflict with usual absorbed dual Regge models.

K +p elastic scattering between 2.11 and 2.72 GeV/ c

Final results are presented of the analysis of the elastic channel in an exposure of 40 000 pictures at each of the four incident K + momenta 2.11, 2.31, 2.5 and 2.72 GeV/ c taken in the 1.5 m British National Hydrogen Bubble Chamber at the 8 GeV/ c proton synchrotron at the Rutherford High Energy Laboratory. Differential cross sections are presented and the results are compared with other published data. A Legendre polynomial analysis requires partial waves up to G wave at all momenta. For the backward peak, visible at each momentum, the slope and the intercept are calculated. A comparison of the forward peak is made with extrapolations from Regge models fitted at higher momenta.

Rapidity correlations in inclusive two pion production and a multiperipheral-thermodynamic model

Inclusive two particle spectra and correlation functions are calculated from a multiperipheralthermodynamic model. This model was previously proposed by the authors in order to derive the velocity weight function used in the thermodynamic description of single particle spectra from the multi Regge model. It was argued that the one-fireball graph dominates at accelerator energies. In this model two particle correlation functions are calculated without introducing new concepts or parameters. The results of the calculation are compared with recent data on inclusive π - π - production in K +p collisions at 12 GeV/ c. Good agreement is found with the experimental correlation function plotted in terms of the rapidity difference Δy ∗ = y 1 ∗−y 2 ∗ of the two observed negative π mesons.

Elastic Scattering and Single-Pion Production inK−pInteractions at 5.5GeVc

We present results of an analysis of two-prong events for elastic scattering and single-pion production in ${K}^{\ensuremath{-}}p$ interactions at 5.5 $\frac{\mathrm{GeV}}{c}$. The resonance parameters for the charged and neutral ${K}^{*}(890)$ and ${K}^{*}(1420)$ are determined and the observed production and decay properties of the charged and neutral ${K}^{*}(890)$ are compared with the theoretical predictions of an absorptive one-particle-exchange model and a Regge model. The ${K}^{*}(1420)$ differential cross section and density-matrix elements are presented and the question of whether more than one resonance exists in this mass range is considered. A search for resonance effects at $K\ensuremath{\pi}$ mass beyond 1500 MeV is made. In particular, the recently reported state at 1800 MeV is discussed. A ${B}_{5}$-model analysis of the reaction ${K}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\overline{K}}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}p$ is also presented.

Some critical remarks on two recently proposed models of the behaviour of elastic slope parameters in hadron-hadron scattering

Two previously proposed models for the structure of elastic-diffraction slopes in hadron-hadron collisions are discussed. One of them, the geometrical Regge model of Barger and Cline, fails to describe the shrinkage-antishrinkage pattern for which it was proposed.

Baryon exchange and shapes of inclusive spectra

Contributions of baryon exchanges to inclusive single-pion production processes are investigated. We show that shapes of distributions in p T 2 are reproduced remarkably well by t dependence of simple baryon exchange, but absence of structure at WSNZ positions is noted. Simple Regge models cannot reproduce x (or missing mass) dependence of spectra; to achieve agreement with dat, we introduce and discuss additional modulating functions of x. Spin and absolute normalization are treated.

Shielded fixed-pole Pomeranchon model for high energy total and differential cross sections

A Regge model with a fixed-pole Pomeranchon and its associated shielding cut is used for π ±p, K ±p and pp scattering at small t and from 6 GeV to NAL and ISR energies. No additional parameters are associated with the cut. The model produces rising total cross sections and anti-shrinkage or non-shrinking diffraction peaks for some s and t. Good fits to total cross sections and to Serpukhov and ISR pp slope parameter data are obtained, and predictions about cross sections and shrinkage at NAL energies are made.

Energy dependence of the elastic diffraction slopes

We have redetermined and compiled the diffraction-slope parameter B for π±p, K±p, pp, and pp, fitting the forward-elastic data from the literature to 1n dσ/dt = A + Bt +(Ct2). We then fit this compilation, together with the total-cross-section data, to a Regge model with a pomeron of slope ≈12 interfering with exchange-degenerate meson trajectories. Thus we account for the observation that the pomeron seems to dominate the exotic channels already at much lower energies than the resonant channels.In resonant regions our model provides only a duality-average description. To give a non-resonant account of the observed structure in the exotic channels just above pion-production threshold, we include cuts for the first quasi-two-body thresholds, and a diffraction-threshold factor for the pomeron amplitude. The cuts turn out to give non-resonant Argand circles. At Serpukhov energies, the gradual emergence of the pomeron from the onset of inelasticity provides a possible description of the Regge-anomalous σT data.Though we did not fit data above 70 GeV/c, our solution with a pomeron slope of 0.4 (GeV/c)−2 extrapolates reasonably well to the new ultra-high-energy CERN-ISR B(pp) data.

A study of the inclusive reactions [formula omitted

The K∗, very strongly produced in K+p collisions at 8.2 GeV/c, are separated out in an inclusive analysis. The key features of their missing mass and momentum transfer distributions are compared to those already seen in the K+p → Ko + anything, inclusive reaction and which are those expected from a simple Regge model. The K∗ results here reported are also compatible with such a model. An important contribution from pion exchange is required at small four-momentum transfers in contradistinction with what is found for quasi elastic production.

Regge models of forward pion and ETA photoproduction

A Regge absorption model is presented which fits all pion and eta photoproduction data for |;t|; < 1, which fits the photoproduction FESR, and uses Regge residues in agreement with all constraints. The model uses poles with NWS zeroes, and uses a black disc form of absorption in which low partial waves was completely absorbed. The absorbed Regge amplitudes show remarkable ϱ − A2 and π − B exchange degeneracy, and agree well with the FESR, which are written for regularized s-channel helicity amplitudes in order to examine their absorption zero structure. We also examine models using a conventional form of absorption, and models in which the poles do not have NWS zeroes. We find that models without NWS zeroes can fit the high energy data, but are unable to fit the sum rules. Since Regge absorption models do not fit the distinctive large-t behaviour of the cross sections, we discuss fixed-pole models as a possible explanation of these data, and show that even in fixed pole models, some Regge cuts are necessary. We present are predictions of the various models for some new experimental quantities which can be measured using simultaneously polarized targets and beams, and suggest a test for A1 exchange.

Note on the Equivalence of Regge and Geometric Models

We show that a Regge pole plus destructive cut imitates a direct-channel Regge pole, the interpretation of which is well known in classical scattering theory. The rotating Regge part is "dual" to scattering from the edge of an interaction region of radius 0.8 F. A new interpretation is given for Schmid loops.

Δ++ϱ0 and Δ++ω0 final states at 5.45 GeV/c

Results are reported on the Δ ++ ϱ 0 and the Δ ++ ω 0 final states obtained from a 4 event/μb exposure of the Argonne National Laboratory 30 inch hydrogen bubble chamber to a π + beam at 5.45 GeV/ c. Data are presented on cross sections, differential cross sections, spin density matrix elements and differential cross-sections weighted by density matrix elements. Certain features of the data relevant to various Regge models are noted and the data is compared to a π-B exchange degenerate Regge model due to Abrams and Maor.

Regge pole-cut effective trajectories and the dual absorptive model

Recent ly IIARARI has proposed an in teres t ing dual absorpt ive model for two-body hadronic ampl i tudes , incorpora t ing good features of both the convent ional Regge models and opt ical or absorp t ive models (x.2). I t explains qua l i ta t ive ly a number of features of high-energy scat ter ing like the cross-over phenomena, the presence or the absence of ]t] ~ (0 :6) (GeV) 2 dips in elast ic and inelastic sca t ter ing and cer ta in facts about the polar izat ions and par t ic le-ant ipar t ic le cross-sections. Some quan t i t a t i ve success in fitt ing K+p, K p elast ic differential cross-sections at P,,b = 5 GeV/c for It[ < ~ 1.5 (GeV) ~ has been also achieved (2). The main assumption of I ta rar i ' s model is t ha t the imaginary par t of the nonpomeron ampl i tude {including Regge poles, cuts, etc.) is domina ted by the most per ipheral par t ia l waves within the interact ion radius r. The pome. ron par t , which is supposed to be connected to the nonrcsonant background, is then added to this contr ibut ion. Then, apar t f rom the pomeron contr ibut ion to the hcl iei ty nonflip ampli tudes , the imaginary par t s of the s-channel hel ici ty ampl i tudes are given by

Analysis of Reggeon-Particle Spin Couplings in Feynman-Diagram Models of Reggeization

An attempt is made to fit certain data for the reactions ${K}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{K}^{*}(890){\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p$ and ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}p\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ifmmode\pm\else\textpm\fi{}}p$ using simple Regge models incorporating the Reggeon-particle spin couplings of Blankenbecler and Sugar. The aim is to see if a universal form of such spin couplings exists. It is shown that this is not the case if simple, unadorned Regge models are used, but that if absorption is appealed to virtually any type of spin coupling will yield successful fits to existing data.

A simple empirical description of K ±p elastic scattering combining regge and absorption models

The sums and differences of K +p and K −p elastic scattering angular distributions above 3 GeV/ c incident momentum are analyzed. A simple factorization model, in which the t dependence and s dependence of the amplitudes are separated, is utilized to obtain a simple empirical description of these cross section combinations. Conventional values for the Pomeranchuk and ω trajectories are obtained. The Pomeranchuk and ω residue functions are quantitatively well described by a single exponential and the Bessel function J 0, respectively. Additional crossovers of the K +p and K −p elastic cross sections are predicted at t = −1.1, −2.7 and −5.0 (GeV/ c) 2.

Theory of pi K scattering near threshold

A simple theory id developed for the process pi K to pi K near threshold. It is similar to one recently proposed for pi pi to pi pi , and rests on an assumption of smoothness of the scattering amplitudes as functions of the energy-momentum invariants. The Adler PCAC consistency condition is imposed, but instead of current commutators, rho-meson dominance on the mass shell is used to fix overall normalization. The two approaches are connected by the KSRF relation, but because this model depends on two parameters (mass, width) more information is obtained. Thus the model contains P and D waves, and gives improved scattering-length predictions. Comparison with results from crossing-symmetric Regge models suggests that these need important additional terms.

Axial-vector form factors from current algebra Regge poles and Veneziano model

Considering the following processes axial current + nucleon → vector current + nucleon, axial current + pion → vector current + σ-meson, and making use of current algebra identities and the Regge model, an asymptotic expression is obtained for the axial-vector form factors of the nucleon and the pion. Though no definite power behaviour can be found by means of the Regge model alone, it is possible to find, under suitable assumptions, generalized scaling relations among vector and axial vector from factors. The use of the Veneziano model in the pion case, fixes the asymptotic power behaviour and thus, the pion scaling relations are obtained without further assumptions.