Diffractive processes in pp interactions at 5.1 GeV/c

We have investigated the interaction $\text{p}\text{p}\text{→}\text{p}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}$ at 5.1 GeV/c using the prism plot method. In addition to the $\text{Δ}{}^{\mathrm{++}}\text{Δ}{}^{\mathrm{??}}$ final state, we isolate the three particle diffractive dissociation of the proton and antiproton into (pπ⁺π^?) and $\text{(}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ respectively. We estimate this process accounts for 30% of the final state.     

Strange particle production in pp annihilations at 8.8 GeV/c

Results are presented from an experiment at the SLAC 40″ hybrid facility (SHF) using an 8.8 GeV/c antiproton beam. Using external detectors and an on-line trigger, a sample of events enriched in $\text{p}$p annihilations was obtained. pp interactions taken under the same conditions enabled the annihilations to be identified. Cross sections and distributions for the inclusive production of K_s⁰ and K^1±(890), and cross sections for exclusive channels with a pair of strange particles are presented.     

On the difference between pp and pp topological cross sections up to 100 GeV/c

New 100 GeV/c$\text{p}$p data are used to find moments of the difference between the $\text{p}$p and pp topological cross sections. The mean multiplicity for annihilations at 100 GeV/c is estimated to be 9.06 ± 0.56, and the value of the quantity 〈n〉/D to be 2.75 ± 0.33. It is shown that $\text{R}{}_{\mathrm{n}}\text{= {σ}{}_{\mathrm{n}}\text{(}\text{p}\text{p) ? σ}{}_{\mathrm{n}}\text{(pp)}/σ}{}_{\mathrm{n}}\text{(pp)}$ appears at 100 GeV/c to have acquired an asymptotic form, R_n = s^?αβⁿ, with α and β constant.     

pp and pp forward elastic scattering between 4 and 10 GeV/c

Differential cross sections have been measured in the region of small forward angles (between 0 and ～40 mrad) for the elastic scattering reactions $\text{pp}\text{→}\text{pp at}\text{4.2, 7.0}\text{and}\text{10.0}\text{GeV}\text{/c}\text{and}\text{p}\text{p}\text{→}\text{p}\text{p at}\text{4.2, 6.0, 8.0}\text{and}\text{10.0}\text{GeV}\text{/c}$. The maximum momentum transfer is ～0.025 GeV² at the lowest and ～0.10 GeV/c at the highest incident momentum. Values of the slope and the real part of the forward scattering amplitude of the above reactions have been derived; the values obtained are in good agreement with dispersion relations.     

The four-pion final state in pp annihilations at 5.7 GeV/c

577 events from $\text{p}\text{p}\text{→2π}{}^{\mathrm{+}}\text{2π}{}^{\mathrm{?}}$ annihilations at 5.7 GeV/c are analyzed. Single-particle spectra are studied and an effective matrix element in the form Π_i=1⁴ exp(?Bp_Ti²) is determined. The rates for production of ?° and f⁰ mesons are estimated and the influence of resonances on the angular distributions of pions and dipions is investigated. Transverse momenta correlations can be explained using peripheral phase space.     

Diffraction and resonance production in exclusive pp interactions at 100 GeV/c

We have investigated the reactions $\text{p}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{a}\text{?}\text{and}\text{p}\text{p}\text{a}\text{?}\text{p}\text{p}\text{2π}{}^{\mathrm{+}}\text{2π}{}^{\mathrm{?}}\text{at}\text{100}\text{GeV}\text{/c}$. The $\text{p}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}$ final state is dominated by diffractive production of a $\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{(}\text{or}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{)}$ system which shows a strong tendency to form $\text{Δ}{}^{\mathrm{++}}\text{π}{}^{\mathrm{?}}\text{(}\text{or}\text{Δ}{}^{\mathrm{++}}\text{π}{}^{\mathrm{+}}\text{)}$. The process $\text{p}\text{p}\text{a}\text{?}\text{Δ}{}^{\mathrm{++}}\text{Δ}{}^{\mathrm{++}}$ is also observed in this reaction, indicating an energy dependence of s^?1.5±0.1. The $\text{p}\text{p}\text{2π}{}^{\mathrm{+}}\text{2π}{}^{\mathrm{?}}$ channel shows less single diffraction, and has a doubly diffractive component consistent with pomeron factorization. Strong Δ⁺⁺(Δ⁺⁺) production is agoain seen, but in contrast to the $\text{p}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}$ channel we also observe considerable ?⁰ production.     

Diffractive dissociation of the beam particle in pp interactions at 32.1 GeVc

We report the results of a study of the reaction $\text{p}\text{p}\text{→}\text{p}\text{+}\text{x}\text{at}\text{32.1}\text{GeV}\text{c}$, where the recoiling proton has a small laboratory momentum. The reaction is studied in the 4.5 m Mirabelle bubble chamber at Serpukhov. We compare the diffractive dissociation of the incident antiproton to other incident particles.     

Exclusive reactions in pp interactions at 32 GeV/c

The cross sections of several exclusive reactions in $\text{p}\text{p}$ interactions are given. In the channels $\text{p}\text{p}\text{→}\text{p}\text{p}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{and}\text{p}\text{p}\text{→}\text{p}\text{p}\text{2π}{}^{\mathrm{+}}\text{2π}{}^{\mathrm{?}}$ which dominate the interactions, the single and double diffractive dissociations are analysed and compared to the results obtained with K^±p interactions at the same energy, pp and $\text{p}\text{p}$ interactions at other energies. The test of factorization at the p → pπ⁺π^? vertex is well verified. The process $\text{p}\text{p}\text{→ Δ}{}^{\mathrm{++}}\text{Δ}{}^{\mathrm{++}}$ is studied and the cross sections of $\text{Δ}{}^{\mathrm{++}}\text{,}\text{Δ}{}^{\mathrm{++}}\text{, ?}{}^0\text{and}\text{f}{}^0$ production are also given.     

Possible heavy lepton signals at pp colliders

If a new sequential heavy lepton L exists with mass below that of the W boson, it will give rise to the following decay chains: W → Lν_Lwith $\text{L}\text{→}\text{e}\text{ν}{}_{\mathrm{<mtext>e</mtext>}}\text{ν}{}_{\mathrm{<mtext>L</mtext>}}$ or $\text{L}\text{→}\text{Q}\text{qν}{}_{\mathrm{<mtext>L</mtext>}}$. We critically study, and quantify, the possibility of identifying this heavy lepton signal against the various backgrounds in high energy p?p collision. We find that the leptonic decay signal is plagued by serious b?b, W → eν, and W → τν backgrounds, whereas the hadronic decay mode leads to a distinctive signature, after selected cuts are applied. We discuss how the mass of such a lepton may be determined.     

Search for baryonium production in pp and K−p interactions at 12 GeV

A search has been made for narrow structures in $\text{p}$p, $\text{p}$pπ^? and Λ⁰$\text{p}$ systems. No significant structures are seen. The upper limit at the 99.5% confidence level for production of narrow states in the $\text{p}$p system in the mass range 2.0–2.2 GeV is 40 nb.     

Elastic pp scattering in the cern sps energy region

The pronounced dip-bump structure with a sharp minimum at |t| = 1.5 (GeV/c)², recently observed in elastic $\text{p}$p scattering at P_L = 50 GeV/c at the CERN SPS, is explained by the quark multiple scattering model with a realistic wavefunction for the proton and the antiproton. It is predicted that a second dip will appear around |t| = 7 (GeV/c)² at P_L = 50 GeV/ c and at higher energies.     

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.     

Observation of a narrow resonance near the pp threshold

Annihilation and elastic cross-sections of $\text{p}$p have been measured between 400 and 850 MeV/c. In both cross-sections a resonance is observed at a mass of 1939 ± 3 MeV. For its natural width τ ? 4 MeV is obtained.     

Evidence for high mass NN and NNπ enhancements observed in pd interactions at 5.55 GeV/c

Based on 4085 $\text{p}\text{n→Xπ}{}^{\mathrm{?}}$ events, X denoting a neutral $\text{N}$N or $\text{N}\text{Nπ}$ system, we present evidence for 5.1 and 3.1 standard deviation enhancements at the X mass of 2.85 and 3.05 GeV/c², respectively. The lower mass bump has a width of Λ ? 39 GeV/c² while the 3.05 GeV/c² is seen as a one bin accumulation (20 GeV/c² width). The relevance of these peaks is discussed.     

Experimental analysis of pp interactions between 0 and 1.2 GeV/c: Evidence for a pp → 5π effect near 1950 MeV/c2

An experimental analysis of $\text{p}\text{p}$ interactions between the $\text{p}$p threshold (√s = 1878 MeV) and √s = 2 100 MeV leads to clear evidence for an s-channel effect in the reaction $\text{p}\text{p}\text{→ π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^{\mathrm{+}}\text{π}{}^{\mathrm{?}}\text{π}{}^0\text{at}\text{1949 ± 10}\text{MeV}\text{/c}{}^2\text{(Γ ? 80}\text{MeV}\text{/c}{}^2\text{)}$. A comparison is made with the backward elastic scattering and charge-exchange behaviour. An interpretation in terms of an object strongly coupled to mesonic decay modes, with small or middle-sized elasticity (x ? 0.135_?0.06^+0.13) is given. No significant narrow structure is observed in the backward elastic scattering between 1.9 and 2 GeV. The experimental resolution of √s in this case is 2 MeV.     

Double inelastic interactions in pd collisions in the 1.6–4.3 GeV/c incident p momentum range

We present results on $\text{p}\text{d}$ multiplicity distributions at 3.9 and $\text{4.3}\text{GeV}\text{/c}\text{p}$ incident momenta obtained from a bubble chamber experiment. An excess is observed for the even-prong multiplicities as compared with $\text{p}$ collisions on free protons. This excess as well as that observed in other existing $\text{p}\text{d}$ data in the 1.6–2.9 GeV/c range was analysed in terms of double interaction processes inside the deuteron.     

Hyperon-antihyperon production in pp interactions at 3.6 GeV/c leading to ⩾3 particles in the final state

Results are presented on the properties of the $\text{p}$p interactions at 3.6 GeV/c leading to a hyperon or an antihyperon in final states with ?3 particles from an experiment of 35 eV/μb sensitivity. Results of amultidimensional mass fit to each final state are given along with the cross sections, differential cross sections and polarization, where possible, for the hypercharge exchange reactions $\text{p}\text{p}\text{→}\text{Λ}\text{Y}{}^1\text{(1385),}\text{Λ}\text{Y}{}^1\text{(1520),}\text{Σ}\text{Y}{}^1\text{(1385)}\text{and}\text{Σ}\text{Y}{}^1\text{(1520)}$.     

Elastic pd scattering at 5.55 GeV/c incident momentum

Based on 150 000 photographs taken at the ZGS with the 30 inch deuterium-filled chamber we present an analysis of the elastic $\text{p}$d scattering reaction. Due to unrecoreded small deuteron recoils we were only able to measure the elastic cross section in the four-momentum region |t| > 0.03 (GeV/c)². Extrapolation towards small |t| by two different methods gave us two compatible estimates of the total elastic cross section. The differential cross section was analyzed by means of the Glauber formalism both with and without the effects due to the D-wave part of the deuteron wave function. The differential cross sections of np at 5.4 GeV/c and $\text{pn}$ deduced from our data were compared and exhibit a crossover phenomenon.     

Remarks on multiplicity fluctuations and KNO scaling in pp collider experiments

It is suggested that a major source of the recently observed large multiplicity fluctuation satisfying KNO scaling in $\text{p}$p collider experiments is the fluctuation of the impact parameter b. Conssequences of the association of the KNO variable z with b are discussed.     

General features of the pp interaction at 12 GeV/c

Simple inclusive cross sections for $\text{p}\text{p}$ interactions at 12 GeV/c are given. The data cover prong cross sections, V⁰ production and resonances. Separation has been made into annihilation and non-annihilation modes. Some implications of the data are discussed. It is pointed out that the ratios of cross sections for $\text{?}{}^0\text{π}{}^{\mathrm{?}}$ production are independent of incident antiproton momentum in $\text{p}\text{p}$ annihilation processes, and that data at the highest available pp energies (ISR) tend to the same value.