Nuclear size dependence of inclusive particle production

The inclusive production of π⁺, π^?, K⁺, K^?, p and $\text{p}$ for protons incident on carbon and tungsten targets was studied at the Internal Target Area of the Fermilab. We assume an A^α dependence for the inclusive cross sections and report here on the variation of α with incident momentum, transverse momentum and particle species.     

A measurement of the KL0p elastic cross section for 3 ⩽p⩽13 GeV/c and 0.1⩽|t|⩽1.3 GeV2

The cross section for the K_L⁰p elastic scattering has been measured for the first time. The incident momentum and momentum transfer ranges are 3 ?p? 13 GeV/c, 0.1 ? |t| ? 1.3 GeV². The results are compared to those of other experiments related to ours by isotopic spin conservation, finding agreement with some and discrepancies with others. The differential cross sections have been parametrized in the form Ae^bt. The coefficients show little or no dependence on energy, with A ? 9.8 mb · GeV^?2and b ? 4.7 GeV^?2. The effective linear trajectory has been determined and gives α₀ = 0.95 ± 0.15, α′ = ?0.35 ± 0.48 GeV^?2, in good agreement with dominance by pomeron exchange.     

An experimental test of exchange degeneracy in the hyperchange exchange reactions π+p→K+Σ+and K−→π−Σ+

For the first time, the line reversed reactions π⁺p→K⁺Σ⁺and K^?p→π^?Σ⁺ have been studied in the same apparatus. We present the differential cross sections and polarizations over a large t range and at two momenta, 7.0 and 10.1 GeV/c. The differential cross sections as a function of t are shown for the first time to cross over. Going from the lower to the higher momentum, the differences in cross section between the two reactions diminish at low |t| by about a factor 2. We find large polarizations of opposite sign for the two reactions. The momentum dependence, presented in the form of α_eff(t) for the t range 0 to ?2 (GeV/c)², is compared with the expectations from the K¹?K⁷ trajectory.     

Comparison of planar features of K−p interactions with e+e− annihilations and deep inelastic μp scattering

The planar features of hadronic final states in K^?p interactions at 4.5, 5.6 and 14.3 GeV c.m. energy are compared with data from e⁺e^? annihilation and deep inelastic μp scattering. A strong energy variation of the distributions (1/σ)dσ/dp_t², 〈p_t²〉_in and Σp²_{t in} is observed over this energy range. Striking agreement is found between the K^?p data at 14.3 c.m. energy and the leptonic data at similar hadronic c.m. energies. The behaviour of these distributions from K^?p data is not well described by the simple quark fragmentation model, but shows deviations similar to those attributed to hard gluon effects in leptonic interactions.     

A study of elastic photoproduction of low massK + K − pairs from hydrogen in the energy range 2.8–4.8 GeV

The results of an experiment to study elasticK ⁺ K ^? photoproduction are presented. Differential cross sections and spin density matrix elements for ?(1.019) production are stddied as a function of incident photon energy and over a wide range of momentum transfer,t (t _min >t>?1.5(GeV/c)²). Helicity conserving amplitudes are observed to dominate ? production throughout this range and the differential cross sections exhibit a forward diffractive peak which cannot be understood in terms of a simple exponential dependence. A new value of the photon ? coupling constant is determined and shown to be consistent withe ⁺ e ^? annihilation measurements. A detailed study of the energy dependence of the differential cross sections is made, including other experimental data, and the extracted effective Regge trajectory compared with other diffractive processes. A study of the dependence of theK ⁺ K ^? decay angular distribution on invariant mass reveals evidence for ans wave contribution interfering with thep wave ? which may be attributable to theS ^* meson.     

Systematics of exclusive diffraction dissociation modes inK ± p interactions at 32 GeV/c

We present results of an investigation of diffraction dissociation in exclusive channels inK ^± p interactions at 32 GeV/c. Total cross sections are determined forK ^±→K ^±π⁺π^?,K ^±2π⁺2π^?,K ⁰π^±π^± K ^±2π⁺π^?,K ^± K ⁺ K ^?,K ^±p \(\bar p\) , \(\bar \Lambda \) p, andp→pπ ⁺π^?,p2π⁺2π^?,pK ⁺K^?,ΛK ⁺,ΛK ⁺π⁺π^? dissociation modes, ranging from a high of ? 300 μb to ～ 3 μb. Thedσ/dt′ differential cross sections of most of the systems studied exhibit structure, with breaks of slope att′ ～ 0.2 to 0.5 GeV²; some modes have a sharp forward spike with a slope exceeding 10 GeV^?2. A systematic investigation of two-body dissociation modesK→A+B andp→A′+B′ shows that these cross sections decrease with increasing threshold massM _A+M _B, that they are comparable for kaon and proton dissociations at similar diffractive excitation masses and are systematically suppressed by a factor 3–4 for dissociations requiring an \(s\bar s\) quark pair creation when compared to \(u\bar u\) pair creation indicating a breakdown ofSU ₃ symmetry for the \(q\bar q\) sea.     

K + p andK − p elastic scattering at 32.1 GeV/c

Results are presented onK ⁺ p andK ^? p elastic scattering at 32.1 GeV/c in the |t| interval 0.06–1.4 GeV². The samples contain approximately 15,000 events each and are obtained in the MIRABELLE bubble chamber at the Serpukhov accelerator. The |t| distributions are parametrized by quadratic exponential formsdσ/dt=A exp (bt+ct ²). The total elastic cross sections, obtained by integrating the fitted distributions, are (2.39±0.07) mb and (2.57±0.10) mb inK ⁺ p andK ^? p interactions, respectively. A cross-over between theK ⁺ p andK ^? p differential cross sections is found at |t _c |=0.17±0.02 GeV². The hypothesis of geometric scaling becomes valid somewhere between 32 and 70 GeV/c forK ⁺ p interactions, and is trivially verified forK ^? p scattering. Finally, an impact parameter analysis of the difference betweenK ^? p andK ⁺ p elastic amplitudes is presented.     

Measurement of the charge asymmetry of the Dalitz plot parameters for K ± → π ± π 0 π 0 decays

The results are presented for the charge asymmetry of the Dalitz plot parameters g, h, and k measured for K ^± → π ^± π ⁰ π ⁰ decays. The experiment has been carried out in the 35-GeV/c kaon beams at the IHEP accelerator. The g, h, and k parameters appear to be identical for K ⁺ and K ^? decays within the experimental uncertainty. In particular, a value of (0.2 ± 1.9) × 10^?3 is obtained for the charge asymmetry A _g = (g ⁺ ? g ^?)/(g ⁺ + g ^?) of the Dalitz plot slope.     

New limits for the exotic exchange reaction π−p → K+Σ− at 5 and 8 GeV

Measurement of the exotic exchange reaction π^?p → K⁺Σ^? has been performed at 5 and 8 GeV, in the ?0.015 to ?0.13 and ?0.009 to ?0.15 (GeV/c)² range of t repectively. We give the value near t = 0 of the differential cross section at 5 GeV, 21_?21⁺⁷⁶ nb/(GeV/c)², and an upper limit (< 37 nb/GeV/c)²) at 8 GeV. As a check the measured differential cross section is given at both energies for the reaction π⁺p → K⁺Σ⁺ in the same range of t.     

Elastic and inelastic φ photoproduction

The differential cross section of the reaction (γp → pφ) has been measured in the t range 0 ? t ? 0.4 GeV² and for photon energies from 3.0 to 6.7 GeV. In particular for the small t region the measurement accuracy was better than 10%. We obtained for the slope parameter B in an exponential parametrization of the differential cross section dσ/dt = Ae^?Bt values of $\text{B ? 6 ± 0.5}\text{GeV}{}^{\mathrm{?2}}$ which are significantly larger than the slopes obtained by most other experiments at higher t values. This indicates a t dependence of B particularly in the small t region.An energy dependence of the optical point (dσ/dt)_t=0, observed in our measurements, has been explained as a kinematic effect due to the VDM relation. A fit of our measurements is in excellent agreement with all other published values of (dσ/dt)_t=0(γp → φp), this implies that σ_tot(φp) must be essentially energy independent in this energy range.Spin density matrix elements of the φ have been evaluated and an analysis of the helicity amplitudes has been carried out. This analysis confirmed s-channel helicity conservation. Moments of spherical harmonics of the $\text{K}\text{K}$ angular decay distribution have been computed for 10 MeV $\text{K}\text{K}$ mass-bins from threshold to 1.3 GeV. The mass dependence of the normalized moments is generally smooth. Contributing amplitudes have essentially only even moments. The moment 〈Y₂⁰〉/〈Y₀⁰〉 changes sign above the φ mass.Differential cross sections for the inelastic φ production γp → φX have been evaluated for the first time both with respect to t?t_min and M_K. The integrated inelastic cross sections are comparable in size with the elastic ones. The slopes of the differential cross sections dσ/dt appear to become flatter with increasing M_X.     

Study of proton dissociation into ΛK+ in 3-body final states at 10 and 16 GeV/c

Results are presented for p → (ΛK⁺) dissociation in the reactions K^?p → ΛK⁺K^? and and π^±p → ΛK⁺π^±at 10 and 16 GeV/c. The cross sections for the low-mass ΛK⁺ enhancement are compatible with the energy dependence σ ∝ p_lab^?0.3. The t′ spectra or the (ΛK⁺) threshold enhancement are exponential in shape. Its decay angular distribution reveals neither s-channel nor t-channel helicity conservation. The relative probabilities of the processes $\text{p}\text{→}\text{p, p}\text{→ (}\text{N}\text{π)}{}_{\mathrm{<mtext>I=</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{and p}\text{→ (Λ}\text{K}{}^{\mathrm{+}}\text{)}$ dissociation are in the ratios 100 : 10 : 0.2, independent of the nature of the incident particle.     

Charged particle multiplicity distributions for 32 GeV/c K±p and pp interactions and for 50 GeV/c π±p interactions

Topological cross sections are presented for K⁺p, K^?p and $\text{p}\text{p}$ interations at 32 GeV/c and for π⁺p and π^?p interactions at 50 GeV/c observed in the 4.5 m Mirabelle hydrogen bubble chamber at Serpukhov. Parameters characterizing the behaviour of the multiplicity distributions, namely 〈n_c〉, D and f₂ and the normalized moments are given. The dependence of these parameters on the energy and the nature of the beam particle is discussed. The multiplicity distributions obtained cannot be described by a single function in the KNO variables.     

The ϱ and A2 exchange amplitudes in meson-baryon scattering for ϱlab between 2.5 and 200 GeV/c

We present a parametrization of the ? and A₂ exchange amplitudes which fits all the available data on the reactions $\text{π}{}^{\mathrm{?}}\text{p}\text{→ π}{}^0\text{n}\text{, π}{}^{\mathrm{?}}\text{p}\text{→}\text{K}{}^0\text{n}\text{,}\text{and K}{}^{\mathrm{+}}\text{n}\text{→}\text{K}{}^0\text{p}$ in the momentum range from 2.5 to 200 GeV/c and for momentum transfers up to t = ?2.0 (GeV/c)².     

Comparing the p̅p → K − K + and p̅p → π−π+ reactions

A partial wave amplitude analysis of LEAR data on differential cross sections and analyzing powers of p?p → K ^? K ⁺ has been performed in the range p _lab = 360 ? 1000 MeV/c, and compared to the results from the same observables for p?p → π^?π⁺. Contrary to other analyses we see no compelling evidence of resonance behavior in our amplitudes. However, as we discuss, the resulting amplitudes are not unique since a third observable remains to be measured for both reactions. Another remarkable result is that for p?p → K ^? K ⁺ all our solutions in the momentum interval below 900 MeV/c, only partial wave amplitudes including J _max = 2 are necessary. This upper limit on the angular momentum is smaller than J _max = 3 which is required for the data of the reaction p?p → π^?π⁺ in the same momentum interval. This finding is consistent with a model analysis for data above 1 GeV/c. Annihilation models with short range baryon exchange give too small J ≥ 2 amplitudes and final state ππ and K?K interactions are presumably very important.     

Process dependence of the target jet remnants in the photoproduction of large transverse momentum jets

We use the quark recombination model of Das and Hwa to predict the inclusive meson spectra (π⁺, π^?,K ⁺,K ^?) in the target fragmentation region for processes in which a large transverse momentum jet is produced by a nearly real photon. We find that the antiparticle ratios of such target jet mesons are sensitive to the type of process which has produced the largep _t jet. By comparing the ratios found in photoproduction to those in deep inelastic scattering we point out that it is in principle possible to identify the presence of the Bethe-Heitler photoproduction subprocess. We conclude that the target jet remnants can contribute to separating the subprocesses responsible for the photoproduction of largep _t jets.     

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 .     

K−p and pp elastic scattering at 10.1 GeV/c

The differential cross sections for K^?p and $\text{p}$p elastic scattering have been measured over the range of four-momentum transfer squared 0.18<?t<3.3 (GeV/c)². The K^?p data decrease smoothly as a function of ?t, whereas, the $\text{p}\text{p}$ data shows a break at ?t = 0.6 (GeV/c)² followed by a fast drop to ?t ? 1.6 (GeV/c)² where the differential cross section levels off and stays constant out to ?t = 3 (GeV/c)².     

Study of K−p→K1(890)n at 13 GeV

The results of a wire chamber spectrometer experiment studying $\text{K}$¹ (890) production in the reaction K^?p→ K^?π⁺n at 13 GeV are presented. Strong forward structure is observed for |t|< m²_π in the s-channel density matrix elements and differential cross section. These features are similar to those observed in π^?p→?⁰n data and are characteristics of π exchange. In contrast in the intermediate, |t| ～ 0.2 GeV², and large momentum transfer regions $\text{K}$¹ (890) production is demonstrated by the natural parity ??A₂ exchange contribution.     

Electroproduction of π+ n, π- p andK + Λ,K + 2211; 0 final states above the resonance region

The reactionsΣ _v p→π⁺ n,K ⁺ Λ,K ⁺ ∑ ⁰ andΣ _v n→π⁺ n were studied at invariant hadronic masses around 2.2. GeV forQ ²=0.06, 0.28, 0.70, and 1.35 GeV². The main results are: At small |t| the π⁺ production is dominated by longitudinally polarized photons and can be described by one pion exchange. At low |t| the transverse (π⁺ n) cross section drops steeply withQ ², but remains roughly constant forQ ²≧0.5 GeV². For |t?≧0.8 GeV², (π⁺ n/dt) is almost independent ofQ ². The integrated cross section (π⁺ n) shows a similarQ ²-dependence asσ _tot (γ _v p) forQ ²≧0.28 GeV². The ratioσ(π^- p)/σ(π⁺ n) atQ ²=0.70 and 1.35 GeV² for |t|≧0.6 GeV² is smaller than in photoproduction and close to 1/4. The ratioσ(K ⁺ ∑ ⁰ decreases steeply withQ ² following roughly the predictions of the quark-parton model.