E. G. Zverev

Observation of a narrow baryon resonance decaying to pK S 0 in proton-nucleus interactions at 70 GeV/c with the SVD-2 setup

AbstractData from the SVD-2 experiment that were obtained at the IHEP accelerator in 70-GeV/c proton-nucleus interactions are analyzed with the aim of searches for an exotic Θ+ baryon that decays through the pKS0 channel. The reaction pN → pKS0 + X characterized by a bounded multiplicity of charged secondaries is used for this analysis. A resonance of mass M = 1526 ± 3(stat.) ± 3(syst.) MeV/c2 and width Γ < 24 MeV/c2 is observed in the invariant-mass spectrum of the pKS0 system at a statistical significance of 5.6σ. The mass and the width of this resonance correspond to the recently found positive-strangeness Θ+ baryon, which was predicted to be an exotic baryon consisting of five quarks (pentaquark), n

A drift tracker of the SVD-2 setup

uuddbar s

A vertex microstrip detector of the SVD setup for experiments on the IHEP accelerator

n. The total cross section for the production of a Θ+ baryon in pA interactions is estimated at a value within the range 30–120 μb for xF ≥ 0. An analysis of the A dependence of the cross section for Θ+-baryon production does not reveal a significant deviation from the A dependence for inelastic events (∼A0.7).

Experimental estimation of the charm-production cross section in pp interactions at 70 GeV/c with the aid of the SVD setup

The stages of development and the current status of the versatile “Spectrometer with a Vertex Detector” setup designed for physics experiments at the U-70 accelerator of the Institute for High Energy Physics (Protvino) is described. The main detectors of the setup are the vertex detector based on silicon microstrip detectors, the wide-aperture magnetic spectrometer based on multiwire proportional chambers, and the lead-glass hodoscope γ detector. In the setup, there is a fast two-level trigger system for selecting required particle interactions. The key characteristics of the setup systems are presented, and the physical results obtained on it are briefly listed.

Electronic Equipment for Reading and Recording Signals from the Microstrip Vertex Detector of the SVD-2 Setup

The design and the characteristics of a drift tracker for the SVD-2 setup at the U-70 accelerator of the Institute for High Energy Physics (Protvino, Russia) are described. The drift tracker has been developed to improve the quality of track reconstruction in high-multiplicity events. It is composed of 2304 drift tubes with a diameter of 6 mm and a sensitive region 500–900 mm long. The distance between a track and the anode wire is determined from the drift time. The coordinate resolution and the detection efficiency of the tubes have been determined from the data of the accelerator run in 2006.

A Technique for the Mass Testing of Single-Sided Microstrip Detectors

The results of an analysis of data from the SERP-Е-184 experiment devoted to studying mechanisms of the production of charmed particles in proton–nucleus interactions at 70 GeV and their decays are presented. The data in question were obtained upon irradiating the SVD-2 active target consisting of carbon, silicon, and lead plates with a beam of 70-GeV protons. A detailed simulation on the basis of the FRITIOF7.02 and GEANT3.21 code packages made it possible to optimize event-selection criteria and to calculate the detection efficiency for Λc+ baryons. After selecting a signal from the threebody decay of a Λc+ baryon, the inclusive cross section for its production at near-threshold energies, its lifetime, and the parameter of the A dependence of the cross section were found. The Λc+ -baryon yields are tabulated along with data from other experiments and theoretical predictions.

A Technique for Testing the Si Tracker Modules for the D0 Collider Experiment (FNAL) and Comparative Analysis of the Test Results

A precision vertex microstrip detector has been developed for the spectrometer with a vertex detector (SVD) setup on which the properties of hadrons and short-lived unstable particles are investigated on the accelerator of the Institute for High Energy Physics. The structure and the design of the main detector components—microstrip sensors and an active target—are presented, as well as techniques for manufacturing them. The readout electronics, the data acquisition system, and its software are also described. The accuracy in determining the vertex position is 70–250 µm along the beam axis and 8–15 µm in a transverse direction at a throughput of 500–1000 events/s.

New analysis on narrow baryon resonance decaying into pK0(s) in pA-interactions at 70-GeV/c with SVD-2 setup

AbstractCharmed-particle production in pp interactions at 70 GeV/c was studied with the SVD setup at the IHEP accelerator (Protvino). The experimental procedure used and the data-selection methods are described. Data obtained by using a quickly cycling bubble chamber and a magnetic spectrometer are analyzed. The number of inelastic-interaction events recorded in the chamber is 109000, with the charge multiplicity being nch/4. The corresponding statistics are 4.96 event/µb. Part of the events were recorded in the magnetic spectrometer. Three three-prong decays of charged particles near the primary vertex are found on the films, two of these being recorded with the spectrometer. All three are interpreted as D− decays. Two neutral decays observed simultaneously in the chamber and in the spectrometer are interpreted as n