D. Wesson

High rate drift chambers

Fermilab experiment 690, a study of target dissociation reactions pp + pX using an 800 GeVlc proton beam and a liquid hydrogen target, collected data in late 1991. The incident beam and 600-800 GeV/c scattered protons were measured using a system of six 6” x 4” and two 15” x 8” pressurized drift chambers spaced over 260 meters. These chambers provided precise measurements at rates above 10 MHz (2 MHz per centimeter of sense wire). The measurement resolution of the smaller chambers was 90 urn, and the resolution of the larger chambers was 125 pm. Construction details and performance results, including radiation damage, are presented.

High speed simultaneous measurement of pulse area and time-of-flight for photomultiplier signals

Abstract A modular system to provide high speed simultaneous measurements of pulse area and time-of-flight for photomultiplier signals is described. By requiring a minimum pulse size and a time-of-flight signal within a gate before recording either measurement, the system achieves several advantages over other techniques. In particular, since no time is wasted reading channels without useful information, readout speed is enhanced. The system permits accurate measurements at rates exceeding 10 MHz per channel and can be read out without excessive dead time at rates up to approximately 100 kHz. Data storage problems are also reduced. Both pulse area and time-of-flight are measured using 128 bins (7 bits). Costs are less than

Preliminary results of the analysis of the centrally produced φφ system

40 US per channel. Other advantages and design features are discussed.

Λ0 Polarization in Exclusive pp Reactions From the FNAL e690 Experiment

We present preliminary results of the analysis of the centrally produced φφ system at 800 GeV/c in the reaction pp → pslow(φφ)pfast. A partial wave analysis of the data up to 2.6 GeV/c2 shows that three waves with JPCLS = 2++02 and with different Jz and reflectivity are needed to describe the data. A fit to the wave amplitudes using Jost functions gives two resonances, one above and one below the φφ threshold. The resonance above threshold has a Breit‐Wigner structure with MR = 2.243 ± 0.015(stat) ± 0.010(syst) GeV and ΓR = 0.368 ± 0.033(stat) ± 0.030(syst) GeV.

Resonances and Lambda0 polarization in 800-GeV/c p p --> p(diffracted) Lambda0 K+

It is an experimental evidence that all baryons are created polarized from unpolarized p—nucleus collisions. So far, the origin of this polarization remains unexplained in spite of the experimental evidences accumulated in the past thirty years. Up to these days, Λ0 is the most studied baryon for polarization, for it is copiously produced in p—nucleus collisions at the energies of the principal high energy physics accelerators of the world. This paper is an overview of the experimental evidences accumulated on the polarization of Λ0 from unpolarized exclusive pp collisions as function of xF, PT, and M(Λ0K+) in the past fifteen years inside Fermilab e690 experiment, in the particular reactions pp→pΛ0K0π+, pp→ppΛ0Λ−0, pp→pΛ0K+, produced at 800 GeV.

Resonances and Λ0 polarization in 800 GeV/c pp → pdiffractedΛ0K+

Abstract Λ 0 polarization from pp → p diffracted Λ 0 K + at 800 GeV / c in the average depends linearly on Λ 0 K + invariant mass: Λ 0 polarization is 0.635 ± 0.036 at 1.64 GeV , consistent with zero at ≈ 2.195 GeV , and −0.586 ± 0.072 at 3.200 GeV . The origin of this Λ 0 polarization is, probably, the interference of at least two Λ 0 K + resonances, created from the excitation of the target proton, due to the diffracted proton transfered momentum.

Preliminary Results of a PWA of the Centrally Produced φφ System

Abstract Λ 0 polarization from pp → p diffracted Λ 0 K + at 800 GeV / c in the average depends linearly on Λ 0 K + invariant mass: Λ 0 polarization is 0.635 ± 0.036 at 1.64 GeV , consistent with zero at ≈ 2.195 GeV , and −0.586 ± 0.072 at 3.200 GeV . The origin of this Λ 0 polarization is, probably, the interference of at least two Λ 0 K + resonances, created from the excitation of the target proton, due to the diffracted proton transfered momentum.

Lambda0 polarization in p p --> p Lambda0 K+ at 800-GeV/c

We present preliminary results of a Partial Wave Analysis of the centrally produced φφ system at 800 GeV/c in the reaction pp → pslow(φφ)pfast. Our preliminary results with one and two M = 0 waves, indicate that most of the cross section can be described by two waves, with JPC LSη = 2++02−1, 0++00−1.

K{sub s}K{sub s} system at 800 GeV/c

We present some preliminary measurements of Λ 0 polarization, in the final state pp→p{Λ 0 K + } created at 800 GeV/c, as a function of P T ,x F , and the diffractive mass of the object {Λ 0 K + }.

Spin-parity analysis of the centrally produced KsKs system at 800 GeV

Results are presented from a partial wave analysis of a sample of centrally produced mesons in the reaction pp {yields} p{sub slow}(K{sub s} K{sub s})p{sub fast} , with 800 GeV/c protons incident on a liquid hydrogen target. The meson system is found to be predominantly S-wave in the mass range between K{sub s} K{sub s} threshold and 1.58 GeV/c{sup 2} . The f{sub 0}(1500) is clearly observed in this region. Above 1.58 GeV/c{sup 2} two solutions are possible, one with mainly S-wave and another with mainly D-wave. This ambiguity prevents a unique determination of the spin of the f{sub J} (1710) meson.