K. Knudson

Strangeness enhancement at mid-rapidity in Pb Pb collisions at 158-A-GeV/c

We study the influence of lexical subsumption on the semantic proximity of terms. By studying the semantic relation between lexically subsumed terms in an existing controlled vocabulary and those in a corpus, we formulate hypotheses on the underlying specific relations. These hypotheses enable us to propose an ordering of term variants found in the corpus, by probability of decreasing semantic proximity. Results from our experiment show that surface indices like the presence of proper names, compounds and the number of added words in a term variant are criteria for ordering the variants of the same term. The ranking obtained will enable us to form more semantically-cohesive clusters. Applications targeted are text mining, question-answering and science and technology watch.

LHC1: A semiconductor pixel detector readout chip with internal, tunable delay providing a binary pattern of selected events

The Omega3/LHC1 pixel detector readout chip comprises a matrix of 128 × 16 readout cells of 50 μm × 500 μm and peripheral functions with 4 distinct modes of initialization and operation, together more than 800 000 transistors. Each cell contains a complete chain of amplifier, discriminator with adjustable threshold and fast-OR output, a globally adjustable delay with local fine-tuning, coincidence logic and memory. Every cell can be individually addressed for electrical test and masking. First results have been obtained from electrical tests of a chip without detector as well as from source measurements. The electronic noise without detector is ∼ 100 e− rms. The lowest threshold setting is close to 2000 e− and non-uniformity has been measured to be better than 450 e− rms at 5000 e− threshold. A timewalk of < 10 ns and a precision of < 6 ns rms on a delay of 2 μs have been measured. The results may be improved by further optimization.

Observation of direct soft photon production in K+p interactions at 70 GeV/c

Abstract The inclusive γ cross section in K + p interactions at 70 GeV/ c shows an excess of (4.5 ± 0.9) mb over the contributions arising from hadron decays. The excess consists of soft γs with −0.001 x p T c . The shape of this soft γ spectrum is consistent with that expected from QED inner bremsstrahlung, but the measured total cross section exceeds the QED expectation, indicating the presence of other source(s) of soft photons.

Λ and Λ production in sulphur-tungsten interactions at 200 GeV/c per nucleon

Abstract Results from the WA85 Experiment at the CERN Ω Spectrometer are presented. A 200 A GeV/ c beam of 32 S ions was used with a tungsten target. The apparatus is used to detect V 0, s and charged tracks in the range p T > 0.9 GeV/ c and 2.3 Y lab Λ and negative hadrons all show a linear increase with rapidity density in the range 70–140 as expected from models based on a superposition of independent NN collisions.

Enhancement of hyperon production at central rapidity in 158 A GeV/c Pb–Pb collisions

Results are presented on hyperon and antihyperon production in Pb–Pb, pPb and pBe collisions at 158 GeV/c per nucleon. Λ, Ξ and Ω yields have been measured at central rapidity and medium transverse momentum as functions of the centrality of the collision. Comparing the yields in Pb–Pb to those in pBe interactions, strangeness enhancement is observed. The enhancement increases with the centrality and with the strangeness content of the hyperons, reaching a factor of about 20 for the Ω in the central Pb–Pb collisions.

Spin-parity analysis of the E meson centrally produced in the reactions π+ p → π+ (K01K±K±) p and pp → p(K01K±π ±)p at 85 GeV/c

Results are presented of a spin-parity analysis on a sample of ∼ 1000 E mesons centrally produced in the reactions (π+/p) p → (π+/p) (K01K±π∓) p at 85 GeV/c. The E quantum numbers are determined to be JPC = 1++. Its decay in this channel is consistent with being 100% into K∗K + c.c. and no evidenceis seen for a δ π decay mode where δ → KK. The mass and width were determined to be M = (1425 ± 2) MeV and Γ = (62 ± 5) MeV.

Energy dependence of hyperon production in nucleus–nucleus collisions at SPS

A measurement of strange baryon and antibaryon production in Pb-Pb collisions has been carried out by the NA57 experiment at the CERN SPS, with 40 and 158 A GeV/c beam momentum. Results on

A fast on-line trigger for events with multiple high transverse momentum tracks

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Production of multistrange baryons and antibaryons in sulphur-tungsten interactions at 200 GeV/c per nucleon

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Production of strange and multistrange hadrons in nucleus—nucleus collisions at the SPS

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