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Zawartość zarchiwizowana w dniu 2022-12-23

Experimental light meson spectroscopy: search for high spin and exotic mesons

Cel



This project concerns the upgrading of the GAMS set-up at the Institute for High-Energy Physics (IHEP), Protvino, Russia. GAMS is the acronym for a novel type of electromagnetic calorimeter which is now widely used. It shows good energy resolution (sE/E = 5% / nE + 2%) and high precision for the measurement of the co-ordinates of gamma-ray impact ( >> l mm). It is divided into a large number of lead-glass cells (2304 at IHEP, 4096 at CERN), a feature that allows to measure up to 20 gammas in a single event. GAMS is, in both places, the heart of a complex spectrometer. As an example, the mass resolution of a reconstructed h observed into two g is about 3%. The GAMS programme on experimental meson spectroscopy, which has accumulated significant successes since 1980, will provide much needed information on the basic quantum chromodynamics (QCD) problem of light quark and exotic mesons.

GAMS-4p is a spectrometer built at IHEP around an electromagnetic calorimeter that may detect multi-photon events with good energy resolution and high precision on co-ordinate measurements. The spectrometer collects data over 99.5 % of the phase space on multi-photon decays of neutral mesons, which are produced in exclusive 7 charge exchange reactions at the IHEP 70 GeV accelerator. The upgrade of the wide angle calorimeter with heavy scintillating crystals (PbWO4) is under way. This project will provide the first opportunity to use this most promising technique in a physics experiment.

The upgrading of the GAMS setup is essentially proceeding through two steps: the first one, which is already implemented, aims at an increase of acceptance of the apparatus to more than 99.5% of the meson production and decay phase space through insertion of new large angle detectors. This is why the IHEP setup is now called GAMS-4p.

The second one, which is in progress, aims to improve the center of mass angular resolution of the spectrometer - a vital element for the observation of high-spin state - with the better gamma energy resolution provided by the new heavy scintillating crystal PbWO4. This crystal has been extensively studied for gamma detection by members of the GAMS collaboration together with the Minsk group, which has studied structural properties and developed the proper growing technique of such crystals. The first tests have been so thoroughly successful that these crystals are now being considered for future collider experiments.

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Koordynator

Université Libre de Bruxelles
Wkład UE
Brak danych
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Av. F.D. Roosevelt 50
1050 Bruxelles
Belgia

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