Large transverse momentum particle production in αα and pp collisions at the CERN ISR

The production of charged hadrons with high p_T in αα collisions at √s=126 GeV and pp collisions at √s=31 and 63 GeV is compared, and the structure of the events associated with the high-pT particles is studied. The probability of finding associated particles close to the trigger particle increases strongly between √s=31 and 63 GeV for pp collisions. For p_T>2.5GeV/c the αα/pp cross section ratio at the same energy per nucleon is measured to be 18.7 ± 2.0, to be compared with A² = 16, and a higher associated multiplicity is observed for αα.     

Charged particle production and correlations at high transverse momentum at the CERN intersecting storage rings

We study the production of identified charged particles in pp collisions at a c.m. energy of 63 GeV in events with an identified high-p_T trigger particle. The measurements were performed at the CERN Intersecting Storage Rings using the Axial Field Spectrometer.Production ratios are presented as a function of p_T in the range 2.5 to 8 GeV/c.     

Observation of high transverse momentum electrons at the CERN ISR

A search for high transverse momentum electrons directly produced in proton-proton collisions has been performed at the CERN ISR. The apparatus included a magnetic spectrometer with wire spark chambers, a lead-glass counter array, and a threshold gas ?erenkov counter. At a centre-of-mass energy √s = 52.7 GeV, a signal has been observed in the range $\text{1.6<p}{}_{\mathrm{T}}{}^1\text{<4.7}\text{GeV}\text{/c}$. The signal occurs at a level of approximately 10^?4 of the inclusive pion cross-section.     

The production of charged particles with high transverse momentum in proton-proton collisions at the CERN ISR

Results are given on the inclusive production of charged pions, kaons and nucleons in high-energy proton-proton collisions in the centre-of-mass rapidity range |y_cm| < 1 and for transverse momenta up to 4.8 GeV/c. The dependence of the composition of produced particles on y_cm, the total energy $\text{s}$, and transverse momentum p_T is discussed.     

Large transverse momentum particle production at 90° in proton-proton collisions at the ISR

Total charged particle fluxes above 1.2 GeV/c transverse momentum at 90° have been measured at the CERN Intersecting Storage Rings for c.m. energies between 23.2 and 52.7 GeV. In addition, charged pion spectra above 3 GeV/c have been obtained at 44.4 and 52.7 GeV, as well as gamma-ray spectra at the same energies. The upper limit to produce a single electron above 3 GeV/c at 90° is less than 1.2 × 10^?33cm²/sr at 90% confidence level.     

Charged particle spectra in αα and αp collisions at the CERN ISR

Momenta of charged particles produced in inelastic αα, αp, andpp collisions were measured using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. Inclusive and semi-in-clusive spectra are presented as a function of rapidityy, Feynman-x, and transverse momentump _T . The inclusivey distributions agree well with predictions of the dual parton model; the highest particle densities are reached aty?0 and the momenta of leading protons decrease significantly for increasing total multiplicity. ‘Temperatures’ are equal in αα, αp, andpp interactions. Thep _T distributions depend weakly on the multiplicity.     

Positive particle production in the fragmentation region at the CERN ISR

Cross sections for the production of positive pions, kaons and protons in proton-proton collisions at the CERN ISR have been measured. These measurements extend to transverse momenta p_T of 2.5 GeV and span the range in $\text{x = 2p}{}_{\mathrm{<mtext>L</mtext>}}\text{/}\text{s}$ between 0.3 and 0.8 For transverse momenta larger than ～ 1 GeV the cross sections show an increase relative to low-energy data, but are consistent with scaling within the energy range measured here, $\text{31 <}\text{s}\text{< 63}\text{GeV}$.     

Measurement of single electron production up to 45 GeV/c transverse momentum at the CERN ISR

The production of single electrons of transverse momentum between 1.8 and 45 GeV/c is measured in pp collisions at √s=53 and 63 GeV. Contributions from ?,ω,?,ψ, ?, DD? and Drell-Yan pairs are deduced from measurements in the same apparatus.     

W production at large transverse momentum at the CERN Large Hadron Collider

We study the production of W bosons at large transverse momentum in pp collisions at the CERN Large Hadron Collider. We calculate the complete next-to-leading order (NLO) corrections to the differential cross section. We find that the NLO corrections provide a large increase to the cross section but, surprisingly, do not reduce the scale dependence relative to leading order (LO). We also calculate next-to-next-to-leading-order (NNLO) soft-gluon corrections and find that, although they are small, they significantly reduce the scale dependence thus providing a more stable result.     

Correlations between two large transverse momentum πO mesons at the CERN ISR

The correlations between two π^O's of high transverse momentum were studied at the CERN ISR at a centre-of-mass energy $\text{s}\text{= 52.7}\text{GeV}$. Results are presented for two π^O's detected with an azimuthal separation near 180° and also near 0°. Angular and p_⊥ correlations are discussed, as well as invariant mass plots. The observations are compared with some theoretical models of high p_⊥ phenomena. The most striking feature of the data is a strong correlation in the transverse momentum of the two π^O's.     

Charged particle correlations at y = 0 in pp collisions at the CERN ISR

Measurements of the double differential cross sections for ππ and pπ production in pp collisions at the CERN ISR are presented for 5 c.m. energies $\text{s}\text{= 22, 30, 44, 53, 62}\text{GeV}$. Charge and transverse momentum correlations are also reported.     

Production of high transverse momentum particles in p-p-collisions in the central region at the CERN ISR

The inclusive production al all charged particles of transverse momentum p_T between 1.5 and 4.4 GeV/c at centre of mass angles 90° and 59.4° from p-p-collisions with √s = 44 and 53 GeV has been measured. No strong energy dependence is observed for these transverse momenta.     

Transverse momentum distribution in Pomeron-Pomeron collisions at the CERN ISR

Proton-proton interactions which result in a central cluster of massM _x and two quasi-elastically scattered protons are generally described by Pomeron-Pomeron scattering. A study of this process at ISR energies with the Split Field Magnet detector is carried out in terms of transverse momentum behaviour for the centrally produced system of particles. The inclusivep _T distribution for central hadrons is measured up to 3 GeV/c. Forp _T <1.2 GeV/c, thep _T distribution is exponential. Using a subsample of exclusive events, this exponential shape is shown to originate from a phase-space-like decay ofM _x when convoluted with a transverse component of the pomeron momentum. In the highp _T range, the shape of thep _T distribution strongly depends on Feynman-x of the scattered protons in a way that can be described by hard parton scattering.     

Correlations of high transverse momentum π0 pairs produced at the CERN ISR

Correlations of two π⁰ mesons with transverse momenta up to 10 GeV/c have been measured utilizing apparatus with large azimuthal acceptance. The data are analysed in the context of constituent scattering models, and also compared with a simple “back-ground” hypothesis.     

A study of high transverse momentum η and π0 mesons at the CERN ISR

The production of high transverse momentum η mesons from proton-proton collisions has been studied at the CERN ISR. The decay η→γγ was identified in an array of lead-glass ?erenkov counters. The preliminary results, obtained at a total centre-of-mass energy √s=52.7 GeV, show an η signal, which amounts to approximately one half of the π⁰ cross-section for centre-of-mass transverse momenta between 3 and 5 GeV/c. The production of high transverse momentum π⁰'s was also measured and compared with previous results.     

Differential production cross section of Z bosons as a function of transverse momentum at sqrt

We present a measurement of the transverse momentum distribution of Z bosons produced in p&pmacr; collisions at sqrt[s] = 1.8 TeV from data collected by the DO experiment at the Fermilab Tevatron Collider. We find good agreement between our results and current resummation calculations, and also use our data to extract nonperturbative parameters for a particular version of the resummation formalism. The resulting values are significantly more precise than obtained in previous determinations.     

Experimental results on diffractive one-pion production at the CERN ISR

New experimental results are reported on diffractive dissociation of protons into (nπ⁺) in proton-proton collisions at a centre-of-mass energy of $\text{s}\text{= 45}\text{GeV}$. The data were obtained using the Split-Field-Magnet detector at the CERN Intersecting Storage Rings. We have searched for resonance contributions and found peaks at mass values of 1.5 GeV, 1.65 GeV, and 2.1 GeV. A dip in $\text{d}\text{σ}\text{d}\text{t}$ is observed at low t and low mass; it is most pronounced for events with neutrons emitted at 90° in the Gottfried-Jackson frame. The correlation between mass and slope depends strongly on θ_J. The cross section of the channel pp → pnπ⁺ is 400 ± 110 μb at $\text{s}\text{= 45}\text{GeV}$, giving an energy dependence of s^?0.30±0.07 for isospin exchange zero in this channel.     

Ko and λ production at the CERN ISR

Transverse momentum distributions of $\text{λ}{}^{\mathrm{o}}\text{,}\text{λ}{}^{\mathrm{o}}$, and K^o, produced in pp collisions at x = 0, have obtained at the CERN ISR. The K^o yield is in agreement with published K⁺, K^? results, obtained at this centre-of-mass energy (√s≈44 GeV). The results on $\text{λ}{}^{\mathrm{o}}\text{and}\text{λ}{}^{\mathrm{o}}$ production obtained in this experiment are compared with results obtained at lower centre-of-mass energies.     

Particle composition at high transverse momenta in p-p-collisions in the central region at the CERN ISR

Preliminary measurements have been made at centre of mass energies √s = 31 and 44 GeV of the π, K and p production ratios at 90° for p_T between 2.0 and 3.5 GeV/c. The (K+p)/π ratio is given down to p_T = 1.4 GeV/c. No strong energy dependence is observed for these transverse momenta.