E. P. Hartouni

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.

Pion-pion correlations at low relative momentum produced in p-p collisions at 27.5 GeV/c.

We have measured the momentum correlation of pion pairs produced in the collisions of 27.5 GeV/[ital c] protons in liquid hydrogen. By considering events for which all final state particles have been measured, we have succeeded in reducing backgrounds due to particle misidentification below 5% for [pi][sup +] and 1% for [pi][sup [minus]]. Our use of a precision magnetic spectrometer has provided an accurate determination of particle momenta and excellent acceptance for particle pairs with small relative momentum essential for correlations studies. A large data sample of fully reconstructed events (1[times]10[sup 6]) allows us to analyze the correlations for [pi][sup +][pi][sup +] and [pi][sup [minus]][pi][sup [minus]] pairs separately, and also as a function of the final state multiplicity. We find that the pion pair correlations scale 0.98 fm describes the data well. We do not find any indication of multiplicity dependence of the correlation scale for multiplicities from 6 to 14 final state particles.

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

Λ0 Polarization in Exclusive pp Reactions From the FNAL e690 Experiment

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

Some preliminary results from BNL E766 on pp−→pp KS0 Kπ

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.

Study of Λ0 polarization in exclusive pp reactions at 27.5 GeV/c

This brief talk will present the very preliminary results of an ongoing data analysis of the data from BNL E766. BNL E766 was an experiment to study heavy particle spectroscopy in np(15−24 GeV) and pp interactions (28 GeV). The following discussion pertains to the pp → ppKsoKπ run.u2009 (AIP)

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

We report a measurement of the xF and PTΛ0 polarization dependence; Λ0’s were produced in the specific channels: pp→pΛ0K+π+π−, pp→pΛ0K+π+π−π+π−, pp→pΛ0K+π+π−π+π−π+π−, and pp→pΛ0K+π+π−π+π−π+π−π+π− with 27.5 GeV/c protons incident on a liquid hydrogen target. We find that Λ0 polarization is independent of the final state.

Recent results from Fermilab E690

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.

Λ0 polarization in exclusive pp reactions at 27.5 GeV/c

Partial wave analysis results of centrally produced mesons in the reaction pp {yields} P{sub slow}(X)P{sub fast}, with 800 GeV/c protons incident on a liquid hydrogen target are presented. In the reactions considered in this paper the (X) system decays into: a) K{sup 0}{sub s}K{sup {+-}}{pi}{sup {-+}}, b) K{sub s}K{sub s}, and c) {pi}{sup +}{pi}{sup -}.

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

In Λ0’s created from the specific reactions: pp→pΛ0K+π+π−, pp→pΛ0K+π+π−π+π−, pp→pΛ0K+π+π−π+π−π+π−, and pp→pΛ0K+π+π−π+π−π+π−π+π−, using 27.5 GeV/c proton beam incident on a liquid hydrogen target, we measured Λ0 polarization as a function of xF and PT. We found that Λ0 polarization is independent of any particular final state and of any specific mechanism responsible of producing Λ0.