Inclusive charged particle cross sections in full phase space from proton proton interactions at ISR energies

Measurements are presented of inclusive charged particle production in proton-proton collisions at √s=31, 44 and 62 GeV at the CERN ISR. The large acceptance of the Split Field Magnet detector allows a single experimental setup to cover almost the full longitudinal phase space up to a transverse momentum of 3 GeV/c.     

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.     

Production of thef 0 meson in the Double Pomeron Exchange reactionpp→ppπ+π−

Data are presented for the exclusive reaction pp → pp π⁺ π^? at \(\sqrt s = 62GeV\) with two leading protons at large Feynman-x and a centrally produced π^+;π^? system. In this kinematical configuration one expects a substantial contribution from Double Pomeron Exchange, which is a potential source of glueballs. The experiment was performed at the CERN ISR using the Split Field Magnet spectrometer. In the mass range between 1,000 and 1,700 MeV/c² the invariant mass distribution for the central π^+;π^? system exhibits a very significant signal for thef ⁰(1270) and no other obvious resonant states.     

The reaction Pomeron-Pomeron →π + π − and an unusual production mechanism for thef 2 (1270)

Data are presented on Pomeron-Pomeron interactions which produce a centralπ ⁺ π ^? system in proton-proton collisions at \(\sqrt s = 62 GeV\) at the CERN Intersecting Storage Rings. This process may favor the production of gluonic bound states. A partial-wave analysis of theπ ⁺ π ^? system shows evidence for the production of the statesf ₀(975),f ₀(1400), andf ₂(1270). The fitted mass for thef ₂(1270) is about 50 MeV below the world average. In addition, the production mechanism for thef ₂(1270) is uniquely different from that for the other final states in that there is a correlation between the outgoing protons. this is consistent with a picture of two-gluon exchange with thef ₂(1270) produced by gluon fusion, and could indicate that thef ₂(1270) has a glueball component.     

The single-mode rate equations for semiconductor lasers with thermal effects

A mathematical model describing the coupling of electrical,optical and thermal effects in semiconductor lasers is introduced.Numerical and asymptotic solutions are derived, including expressionsfor key physical quantities such as the initial time delay,the frequency of spike oscillation and the temperature rise,together with its influence on the photon density, the electronconcentration and the threshold current. The consequences ofthermal effects in reducing efficiency are thus quantified.     

High-pT pion production in ππ interactions

Charged pion production in high energy π^-π^- interactions is studied in the p_T region of 1–2 GeV/c. The characteristics of pion production in π^-π^- interactions are compared with those in π^-p and pp interactions. The p_T dependence of pion production in these reactions follows a systematic trend which indicates that high-p_T pion production for ππ interactions as well as for πp and pp interactions proceeds via quark-quark scattering as predicted by QCD.     

Inclusive Pomeron-Pomeron interactions at the CERN ISR

Data are presented for the first time on inclusive Pomeron-Pomeron interactions which produce a central systemX (composed mainly of multimeson states) in proton-proton collisions at \(\sqrt s \) at the CERN ISR. The systemX has a Feynman-x distribution which is sharply peaked atx _f=0, is inconsistent with any significant contributions from Reggeon exchange processes, and has an invariant mass dependence in good agreement with the predicted formM _x ^?2 . Kaon production is about 15% of pion production, nearly independent ofM _x, while proton-antiproton production averages about 5% of pion production and increases withM _x. The structure of the central systemX develops into a jetlike shape, asM _x increases, as would be expected from a model of Pomeron fragmentation. The shape of thex _f(π) distribution in the center of mass of theX system (although not proving existence) is consistent with asoft partonic substructure of the Pomeron.