Squark production at the pp collider

The recently observed $\text{p}\text{p}$ collider events with large missing P_T are analysed in terms of a supersymmetric model with a light photino and scalar quarks with mass in the range 20 to 35 GeV. A lower bound of O(60 GeV) on the gluino mass in this scenario is found.     

Squark pair production mechanisms in pp collisions

Through a phenomenological analysis in the transverse plane of a $\text{p}\text{p}$ collision, we study different production mechanisms of squark pairs, decaying into a quark and a photino (missing energy): excitation of squarks inside the proton, fusion of light partons into squark pairs, and decay of heavier gluinos into squarks. The rates for missing transverse momentum are calculated and confronted with the monojet events observed at the CERN collider. In the framework of “minimal” supergravity models the excitation and fusion of squark pairs are disfavoured, whereas the dominant processes involve heavier gluinos and squarks cascading into photinos through intermediate squarks. The agreement with experimental data is better if heavier squarks and gluinos decay through an intermediate b-squark. We remark that energy dissipating effects during the cascade towards the final state tend to improve the comparison between theory and experiment.     

Mechanisms in pp annihilation

We consider the annihilation mechanism in the antiproton momentum range 2.5 to 9.1 GeV/c. Techniques for identifying a “leading pion” are discussed. The annihilation is examined as a quasi two-body process, and the properties of the “leading pion” and the remaining multi-pion “cluster” are presented. A simple parametrization is found to reproduce satisfactorily several features of the data.     

QCD bremsstrahlung effects in hadronic production of jets at the CERN pp collider

Effects attributable to QCD bremsstrahlung which have been recently observed in hadronic production of jets by the UA1 and UA2 collaborations are compared with theoritical expectations. The theoretical results are sensitive to the value of the QCD parameter λ. λ ? 0.1 GeV gives reasonable agreement with experimentally observed effects.     

Weak Drell-Yan processes in pp collisions

The weak production of leptons in high energy proton-antiproton collisions is investigated using the parton model. Charged and neutral current signals are calculated both with the standard SU(2) × U(1) gauge model and with a pointlike four-fermion coupling. In addition to differential cross-sections, angular and polarization asymmetries are calculated and their significance is assessed.     

Angular distributions and structure functions from two-jet events at the CERN SPS pp collider

The two-jet cross section measured in the UA1 apparatus at the CERN $\text{p}\text{p}$ Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x₁ and x₂. The angular distribution dσ/d cos σ rises rapidly as cos → 1, independent of x₂ and x₂, as expected in vector gluon theories (QCD). The differential cross section in x₁ and x₂ is consistent with factorization and provides a measurement of the proton structure function $\text{F(x) = G(x) +}\text{4}\text{9}\text{[Q(x) +}\text{Q}\text{(x)]}$ at values of the four-momentum transfer squared, -t? ≈ 2000 GeV². Over the range x = 0.10?0.80 the structure function shows an exponential x dependence and may be parametrized by the form F(x) = 6.2 exp (?9.5x).     

Soft pion emission in pp resonance formation

We calculate hadronic toponium production by specific diagrams obeying colour conservation and charge conjugation. The resulting rates, though lower than those calculated using semi-local duality arguments are encouraging and may allow for toponium discovery at hadronic colliders currently in development.     

Observation of a narrow pp enhancement at 1940 MeV

A narrow enhancement is observed in $\text{p}\text{p}$ states produced inclusively in proton-proton interactions at 93 GeV. The mass 1940 ± 1 MeV is consistent with that of the S(1936).     

Structures in pp → ππ

A Barrelet-zero analysis is presented of data on $\text{p}\text{p}\text{→ π π}$ in the momentum range 1 to 2 GeV/c. With π^?π⁺ data alone, the slope for ambiguity is very large, but the addition of π⁰π⁰ information enables the number of solutions to be reduced to just a few. Although the alternative solutions differ considerably, they significant common features, in particular, with plausible extra assumptions, all solutions appear to be dominated by resonances in all spin states from J = 1 to 5.     

Analysis of topological cross sections in pp interactions at 22.4 GeVc

The multiplicity distribution for 11558 events in $\text{p}\text{p}$ interactions at 22.4 $\text{GeV}\text{c}$ was analyzed. The average charged multiplicity 〈n_ch〉 for inelastic events was found to be 4.69 ±0.05 and $\text{〈n}{}_{\mathrm{ch}}\text{〉}\text{D=2.04 ± 0.05}$. The early KNO scaling of normalized topological cross sections has been tested.     

pp annihilation channel as a means to distinguish high-energy production models

The possibility to use the pp annihilation channel as a means to distinguish high-energy hadron production models is pointed out, and the application of a multiperipheral model to pp annihilation is discussed. Certain subtraction rules are proposed in order to avoid the necessity of separating the annihilation and non-annihilation events at high energy pp collisions.     

Evidence for two narrow pp resonances at 2020 MeV and 2200 MeV

From the study of the reaction $\text{π}{}^{\mathrm{?}}\text{p→p}{}_{\mathrm{F}}\text{p}\text{p}\text{π}{}^{\mathrm{?}}$ using a fast proton (p_F) trigger device in the CERN Omega spectrometer, we find evidence for two narrow $\text{p}\text{p}$ states produced mainly in association with a Δ° (1232) and a N° (1520). The statistical significance of each peak is greater than 6 standard deviations. Masses and natural widths of these resonances are respectively M = 2020 ± 3 MeV, Λ₁ = 24 ± 12 MeV and M₂ = 2204 ± 5 MeV, Λ₂ = 16_?16⁺²⁰ MeV. Our data are consistent with a small production of the narrow ～ 1935 MeV resonance already reported. Production cross sections for these new $\text{p}\text{p}$ resonances are given.     

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.     

μ-pair production by inelastic πp and pp collisions

The massive μ-pair production in πp scattering is calculated in the Kuti-Weisskopf relativistic quark model of hadrons.     

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.     

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.     

Inclusive V0 production in pp interactions at 12 GeV/c

Results are presented on the inclusive reactions $\text{p}\text{p}\text{→}\text{K}{}^0\text{X}\text{,}\text{p}\text{p}\text{→ Λ}\text{X and}\text{p}\text{p}\text{→}\text{Λ}\text{X}$ at an incident antiproton momentum of 12 GeV/c in BEBC. The cross sections are studied as functions of the Feynman scaling variable x, the rapidity, the transverse momentum of the V⁰ and the missing mass squared. The dependence of the Λ and $\text{Λ}$ polarization on x are also studied. Comparisons with proton-proton data at 12 GeV/c are also made. Finally, events with two detected V⁰ are analyzed in order to study correlations arising from the production of two strange neutral particles.     

A comparison between pp and pp diffractive peaks at and beyond ISR energies

Although a substantial difference between pp differential cross section at ISR energies and $\text{p}\text{p}$ differential cross section at SPS energy has been reported, we demonstrate that both differential cross sections, at least up to |t| ～ 1.2 GeV², can be satisfactory accounted for within the usual eikonal model in which the diffractive component is crossing even. Thus at a given ultra high energy, there is no suggestive evidence for a difference between pp and $\text{p}\text{p}$ diffractive peaks.     

Comparison of pp and pp interactions at s = 53 GeV

Results are presented from the first p$\text{p}$ colliding beam runs at the CERN ISR, using the UA5 streamer chamber detector. p$\text{p}$ interactions at $\text{s}\text{= 53}\text{GeV}$ are compared with pp data taken in the same experiment. The results are in good agreement with extrapolations of low-energy p$\text{p}$ data.     

Cross sections and multiplicity distributions for pp annihilations at 4.6 GeV/c

Channel cross sections have been determined for $\text{p}\text{p}$ annihilations into final states containing 3 to 9 pions at 4.6 GeV/c. The moments of both the charged and neutral pion multiplicity distributions are presented and model predictions are critically examined.