Partial-wave analyses of KN two-body reactions between 1480 and 2170 MeV

We present partial-wave analyses of the reactions $\text{K}\text{N}\text{→}\text{K}\text{N}\text{,}\text{K}\text{N}\text{→Σπ,}\text{K}\text{N}\text{→Λπ}$, using world data from 1480 to 2170 MeV c.m. energy including new data in the range 1775 to 1960 MeV. The three channels have been treated in parallel using enrgy-dependent partial-wave analysis techniques.     

Partial-wave analysis of K−p → π∓Σ± (1385) between 1775–2170 MeV including new data below 1960 MeV

New data are presented for the reaction K^?p → Λπ⁺π^? at 11 energies between 1775 and 1957 MeV in the centre-of-mass. New values for the masses and widths of the Σ^±(1385) are given. The differential cross sections and the complete spin density matrices for the reactions K^?p → π^±Σ^? (1385) were extracted from these data using also the information from the Λ decay. An energy-dependent partial-wave analysis has been carried out over the c.m. range 1775–2170 MeV also using data from an earlier experiment. Comparisons between the observed resonant amplitudes and SU(3) and SU(6)_W ? O(3) predictions have been made.     

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.     

Observation of high mass electron-positron pairs produced in proton-proton collisions at the CERN ISR

In an experiment performed at the CERN Intersecting Storage Rings (ISR), 11 e⁺e^? pairs of high invariant mass value (> 2.5 GeV/c²) have been observed. Of these events, 9 can be interpreted as arising from the reaction p + p → J (3.1) + anything. the cross-section for this reaction is estimated and compared with the result obtained at lower centre-of-mass energies.     

Correlations associated with particles produced at small angles in pp collisions at the CERN ISR

Data on correlations between momentum analysed protons, pions or K mesons, and charged particles produced in pp collisions at the CERN ISR are presented. The charged particles were detected in a ～4π scintillation counter hodoscope. The pseudo-rapidity distributions are well described by production within the limits of cylindrical phase space, with negative kaons and antiprotons yielding narrower distributions than protons, pions and positive kaons. The azimuthal distributions show symmetry around the t-channel axis in the rest frame of the recoiling mass M_x in pp → aX (a = detected proton, pion, positive kaon).     

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.     

Correlations associated with small angle protons produced in proton-proton collisions at 31 GeV total energy

High energy inelastic protons with $\text{x = 2 p}{}_{\mathrm{<mtext>L</mtext>}}\text{/s}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{> 0.99}$ observed in 15.3/15.3 GeV proton-proton collisions at the CERN ISR are accompanied by particles whose angular distribution is confined to a narrow cone in the opposite direction. In constrast, lower energy protons (0.72 < x < 0.84) are accompanied in addition, by particles emitted at larger angles. The ratio of the associated charged multiplicities is approximately 0.4.     

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.     

Contribution of single diffraction dissociation to highp T production in proton-proton collisions at\sqrt s = 62 GeV at the CERN ISR

The contribution of single diffraction dissociation to highp _T particle production has been determined with the split field magnet detector. For transverse momentap _T >2 GeV/c and production angles θ>10° it is found to be less than 5% for all types of trigger particles. Specifically, a diffractive origin of the large production cross section for highp _T protons can be excluded. The contributions found to highp _T production are found to be in good agreement with extrapolations of the relative particle yields from single diffraction dissociation observed in inelastic minimum bias events.     

A measurement of the production of massive e+e− pairs in proton-proton collisions at √s = 62.4 GeV

An apparatus consisting of a superconducting solenoid magnet, cylindrical drift-chambers, and two arrays of lead-glass ?erenkov counters has been used at the CERN ISR to study the production of e⁺e^? pairs of invariant mass above 6.5 GeV/c². Cross sections for the continuum and the ? family of resonances are presented, as well as the mean transverse momentum 〈p_T〉 of the electron-positron pairs in the continuum and resonance region.     

Inelastic intermediate states in proton-deuteron and deuteron-deuteron elastic collisions at the ISR

We present experimental results on proton-deuteron and deuteron-deuteron elastic scattering measured at the two highest ISR energies, √s = 53 GeV and √s = 63 GeV. The data cover the single- and multiple-scattering regions over a wide interval of four-momentum transfer t. In both reactions we find clear evidence for a substantial t-dependent contribution of inelastic intermediate states in the multiple-scattering region, as well as in single scattering. In the analysis we use the Glauber multiple-scattering theory extended to include inelastic shadow effects. This extension of the basic theory contains as input a triple-Regge parametrization describing the high-mass inclusive spectrum. The analysis of inelastic corrections to multiple scattering on deuterons at high energies is shown to provide a sensitive test of different parametrization of inclusive production in proton-proton collisions.     

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 systematics in proton-proton and light ion collisions at the ISR

Some aspects of the variation of inclusive transverse momentum distributions with kinematical and topological variables proton-proton and lightion collisions are described.     

Measurements of elastic scattering in alpha-alpha and alpha-proton collisions at the CERN intersecting storage rings

We measured the elastic scattering of $\text{αα}\text{at}\text{s}\text{= 126}\text{GeV}$ and of αp at $\text{s}\text{= 89}\text{GeV}$. For αα, the differential cross section dσ/dt has a diffractive pattern minima at |t| = 0.10 and 0.38 GeV². At small |t| = 0.05?0.07 GeV², this cross section behaves like exp[(100 ± 10) t]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section α_tot(αα) = 250 ± 50 mb and an integrated elastic cross section σ_e1(αα) = 45 ± mb. Another method of estimating σ_tot(αα), based on measuring the interaction rate, yielded 295 ± 40 mb. For αp, dσ/dt has aminimum at |t| = 0.20 GeV², and for 0.05 < |t| < 0.18 GeV² behaves like exp[(41 ± 2) t]. Extrapolating this slope to |t| = 0, we found σ_tot(αp) = 130 ± 20 and σ_e1(αp) = 20 ± 4mb. Results on pp elastic scattering at $\text{s}\text{= 63}\text{GeV}$ agree with previous ISR experiments.     

Production of meson resonances as leading particles in jets in proton-proton collisions at\sqrt s = 62 GeV at the CERN ISR

The production of ρ(770)⁰,K ^*(892)⁰, \(\bar K^* (892)^0 \) andf ₂(1270) mesons as leading particles in hadron jets (<z>～0.7) has been measured in deep inelasticpp interactions at the CERN ISR at \(\sqrt s = 62\) GeV. The comparison of vector and pseudoscalar meson production at the same transverse momentum provides a rather model independent way to determine the fragmentation parameterV/P. We determine(V/P) _u,d =1.66±0.18±0.63 from the ρ/π ratio and(V/P) _s =0.90±0.13±0.27 from theK ^*/K ratio. For thef ₂(1270) production we findf ₂/ρ⁰=0.30±0.08.     

Measurement of the polarization in the forward peak of π−p→K0λ at 5 GeV/c

The π^?p→K⁰λ polarization has been measured at 5 GeV/c in the range 0<?t<1.4 (GeV/c)². The polarization is small for ?t?0.4 (GeV/c)², becoming negative at the higher values of ?t.     

Analysis of double diffraction dissociation in nucleon-nucleon collisions at the CERN ISR

Final results from combined measurements of single and double diffraction of protons neutrons into (Nπ) and (Nππ) final states are presented. The experiments were performed at the CERN Intersecting Storage Rings with the Split Field Magnet detector using proton and deuteron colliding beams.The general properties of the dissociating vertex in single and double diffractive reactions are essentially identical. Mass spectra and decay angular distributions are compared with the predictions of a dual resonant Deck model. Decay angular correlations and a strong slope-mass correlation are observed also in double diffraction. Detailed tests of factorization indicate its validity over the full range of all kinematical variables and in their correlations.A model-independent analysis gives strong support to the peripheral nature of diffraction dissociation, with double diffraction being concentrated in a narrow gaussian ring at the edge of the proton. Both the exclusive and the inclusive double diffractive cross sections display a marked increase over the ISR energy range. Both mechanisms yield comparable contributions to the peripheral increase of the total pp cross section, with an approximate saturation of the Pumplin bound.     

High pT π0 production from αα and αp collisions at the CERN ISR

The invariant cross sections for π⁰ meson production in alpha—alpha and alpha—proton collisions at the ISR were meas- ured up to transverse momenta of $\text{7}\text{GeV}\text{c}$ and $\text{8}\text{GeV}\text{c}$, respectively. These measurements are compared with π⁰ production in pp collisions at the same values of $\text{s}\text{/}$nucleon, and the variation of the nuclear A-dependence with p_T is determined.     

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.     

Charmonium production in proton-proton collisions and in collisions of lead nuclei at CERN and comparison with Brookhaven data

A review of experimental data on charmoniumproduction that were obtained in fixed-target experiments at the SPS synchrotron and in proton-proton collisions and in collisions of lead nuclei in beams of the Large Hadron Collider (LHC) at CERN (Switzerland) is presented. A comparison with data obtained at the Brookhaven National Laboratory (USA) from experiments at the Relativistic Heavy Ion Collider (RHIC) is performed. Measurement of the suppression of J/ψ-meson production as a possible signal of the production of quark-gluon plasmawas proposed back in 1986 by T. Matsui and H. Satz. An anomalous suppression of J/ψ-meson production was discovered by the NA50 Collaboration at SPS (CERN) in central collisions of lead nuclei at the c.m. collision energy of 158 GeV per nucleon. Data obtained at the c.m. energy of 200 GeV per nucleon in the PHENIX experiment at RHIC indicate that, depending on multiplicity, the suppression of J/ψ-meson production at this energy approximately corresponds to the suppression of J/ψ-meson production in collisions of lead nuclei at the SPS accelerator. Theoretical models that take into account the regeneration of J/ψ mesons describe better RHIC experimental data. The measurement of charmonium production in proton-proton collisions and in collisions of lead nuclei in LHC beams revealed the importance of taking into account the regeneration process. At the LHC energies, it is also necessary to take into account the contribution of B-meson decays. Future measurements of charmonium production at the LHC to a higher statistical precision and over an extended energy region would be of importance for obtaining deeper insight into the mechanism of charmonium production and for studying the properties of matter at high energy density and temperature.