Inclusive cross section ratios in highp T proton-proton scattering at ISR energies

Ratios of inclusive cross sections σ(π⁺)/σ(π⁺+K ⁺+p) and \(\sigma (\pi ^ - )/\sigma (\pi ^ - + K^ - + \bar p)\) were measured for proton-proton interactions with a highp _T hadron in the final state around c.m.s. scattering angles θ?20°, 20° and 45° at two ISR energies \(\sqrt s = 31\) Gev and 62 GeV. Results are shown as functions of transverse and longitudinal momentum and are compared with parton model predictions. The different dependences of positive and negative pion fractions atp _T ?2–3 GeV/c on longitudinal momenta is similar to that observed in soft hadronic interactions at low values ofp _T where the leading proton effect (diquark fragmentation) is known to contribute. The quantitative agreement of the data with diquark model predictions indicates the presence of diquark fragmentation also in highp _T jets.     

A measurement of the proton-proton cross section at the CERN ISR

We present a measurement of the total cross section σ_t in proton-proton collisions at the CERN ISR. The method involves determination of the total interaction rate and machine luminosity. A two-arm scintillation hodoscope observes ～ 90% of the total interaction rate, while a streamer chamber is employed for event topologies missed by the main trigger. An increase of about 10% in σ_t is observed in the energy range √s = 23.6 to √s = 62.8 GeV/c in agreement with previous experiments.     

Measurement of the total proton-proton cross-section at the ISR

We present the first results of a measurement of the total cross-section σ_T in proton-proton collisions at equivalent laboratory momenta between 291 and 1480 GeV/c at the CERN Intersecting Storage Rings (ISR). The method is based on the measurement of the ratio of the total interaction rate and the machine luminosity. The data show an increase of about 10% in σ_T in this energy interval.     

New measurements of proton-proton total cross section at the CERN intersecting storage rings

Measurements of the proton-proton total cross section have been made with increased precision (±0.6%) over the ISR energy range $\text{s}\text{=23.5?62.7}\text{GeV}$. Two different experimental methods gave consistent results, showing that the total cross section increases 10% over the ISR range and in addition that the absolute value of the ISR luminosity can be measured to ±0.9%.     

High energy proton-proton total cross section and cosmic-ray data

Proton-nucleus total inelastic cross sections have been calculated in the multiple scattering theory for incident proton energies ranging between 20 and 10⁵ GeV. The results are compared to available cosmic-ray data. In view of the present analysis, extrapolations of the latest I.S.R. results on the proton-proton total cross section σ according to a logarithmic law almost saturating the Froissart bound seem hazardous.     

Fusion cross section at sub-Coulomb energies

The effective barrier at low energies is approximated by a Coulomb and parabolic barriers. A simple closed formula is obtained for the total reaction cross section which is the natural extension of Wong's results into the low energy domain. Theoretical predictions of averaged energy behaviour agree fairly well with various experimental results. The relation?ω ₀≧π(2kh ²Z₁Z₂ e ²/μ)^1/2 R ₀ ^?3/2 between the curvature and the extremum point of the nucleus-nucleus potential is suggested, based on low energy fusion experiments. By assuming equality sign, it is possible to extract the parameters of the barrier directly from experiment. Incidentally it is found that?ω ₀ remains persistently arround 4.5 MeV for all the reactions which have been investigated.     

Gluon tagging in hard proton-proton interactions at the ISR

Events obtained by triggering on a single particle with high transverse momentump _T show a four-jet structure. The two transverse jets are due to the fragmentation of point-like scattered partons. Experimental evidence is presented that highp _T K ^? mesons and their associated jets are produced by hard scattering and subsequent fragmentation of flavour neutral partons with a rather soft structure function. Hence, gluons are a natural source of highp _T K ^? mesons which do not share any valence quark with the incoming protons. The analysis is based upon measurements of short-range quantum number correlations within the trigger jet and of long-range correlations between different jets. The data were obtained at \(\sqrt s\) =62 GeV GeV with the Split Field Magnet Detector (SFM) at the CERN ISR.     

Maximal electromagnetic contribution to pp inelastic cross sections at ISR energies

The maximal electromagnetix contribution to the pp inelastic cross section is estimated. Although this contribution is insufficient in itself to explain all of the recently observed rise at ISR energies if the purely strong cross section is asymptotically constant, it could amount to as much as approximately 3 mb at √s ≈ 53 GeV if the purely strong cross section rises with energy through the range of present accelerator energies like (ln s)² or slower.     

Spin-spin effect in the Ho total neutron cross section at energies of 0.4 and 1.0 MeV

Measurements of the spin-spin effect, σ_ss in the total cross section for polarized neutrons on polarized ¹⁶⁵Ho are reported at neutron energies of 0.4 and 1.0 MeV. The absence of an observable effect at 1.0 MeV is in contradiction with a recently reported experimental result. The results of an improved theoretical calculation of σ_ss for neutron energies below 8 MeV are presented and used with the new experimental data to obtain the new limit V_ss < 300 keV for the strength of the spin-spin potential.     

The pomeron-particle total cross section and diffractive production of showers at very high energies

The experimental data of ISR and NAL for the process pp → pX are used for the determination of the pomeron-particle total cross section and the triple-pomeron vertex. Estimates of the cross sections of the diffractive production of one and several showers of particles are given. It is shown that at s ～ 10³ GeV² the cross section of all inelastic diffractive processes is ～ 6 mb and grows with energy. A theoretical estimate of the amplitude of pomeron-pomeron scattering is given.     

Pionization at ISR energies

It is shown that the same formula that describes pionization in multiple-particle production at accelerator energies, up to 30 GeV, can also describe inclusive single-particle production spectra obtained at the CERN Intersecting Storage Rings, corresponding to an energy of 1000 GeV. By determining the parameters of the pionization formula at ISR energies we can draw some conclusions about the pionization process at high energies and about some gross features of multiple particle production.     

TeV strings and the neutrino-nucleon cross section at ultrahigh energies

In scenarios with the fundamental unification scale at the TeV one expects string excitations of the standard model fields at accessible energies. We study the neutrino-nucleon cross section in these models. We show that duality of the scattering amplitude forces the existence of a tower of massive leptoquarks that mediate the process in the s channel. Using the narrow-width approximation we find a sum rule for the production rate of resonances with different spin at each mass level. We show that these contributions can increase substantially the standard model neutrino-nucleon cross section, although they seem insufficient to explain the cosmic ray events above the Greisen-Zatsepin-Kuz'min cutoff energy.     

Determination of the proton-proton elastic cross section at 30 GeV center of mass energy

The absolute luminosity of the CERN Intersecting Storage Rings has been determined by the Van der Meer method. Combining the measurement with small angle proton-proton elastic events, we find σ_elastic = (6.8±0.6)mb.     

Comments on spin effects in proton-proton cross section measurements

Bounds are obtained from positivity on the possible size of spin dependent effects on the proton-proton total cross-section.     

A measurement of the cross section of the reaction pp→n ++(1232) at ISR energies

A measurement of the cross section of the charge-exchange reaction pp→ Δ⁺⁺(1232)n at √s = 23, 31 and 45 GeV at the CERN-ISR is reported. The energy dependence continues to follow a power law p_lab^?n with n = 1.94 ± 0.03 indicating dominance of one-pion exchange at the lowest ISR energy; there is some evidence for deviation from this at the higher ISR energies.