We use fits to recent published CPLEAR data on neutral kaon decays to
π
+
π
− and πeν to constrain the CPT-violation parameters appearing in a formulation of the neutral kaon system as an open ...quantum-mechanical system. The obtained upper limits of the CPT-violation parameters are approaching the range suggested by certain ideas concerning quantum gravity.
Development of a fast gaseous detector: ‘Micromegas’ Barouch, G; Bay, A; Bouchigny, S ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/1999, Letnik:
423, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Several
15×15
cm
2
gaseous Micromegas chambers (MICROMEsh GAseous Structure) which consist of a conversion gap and an amplification gap separated by a thin grid have been extensively tested in ...low-intensity
10
GeV/c
pion beam and high-intensity (up to
5×10
5
Hz/
mm
2)
100
GeV/c
muon beam. The detector behaviour has been studied with respect to many parameters: conversion gaps of 1 and 3
mm, amplification gaps of 50 and 10
μm, an external magnetic field and many different filling gases. So far no effect of the magnetic field up to 1.3
T has been observed. The gas mixture argon + cyclohexane appears to be very suitable with gains above 10
5 and a full-efficiency plateau of 50
V at 340
V. With a conversion gap as small as 1
mm and an electronics with a threshold at 5000 electrons the efficiency reaches 96%. With the addition of CF
4 a time resolution of 5
ns (RMS) has been obtained. A spatial resolution better than
60
μ
m has been observed with anode strips of
317
μ
m pitch and was explained by transverse diffusion in the gas. Simulations show that with a pitch of
100
μ
m and the appropriate gas a resolution of
10
μ
m is within reach. This development leads to a new generation of cheap position-sensitive detectors which would permit high-precision tracking or vertexing close to the interaction region, in very high-rate environments.
We present particle beam test results using a high-rate, high-position and high-time-resolution gaseous detector, ‘Micromegas’, of
15×15
cm
2
. The rate capability was measured with 10
MeV protons ...from a TANDEM accelerator. No effect on gain was observed at particle rates up to
10
9
mm
−2
s
−1. With an argon and DME filling the gain was stable up to 50 mC total charge on a
3
mm
2
area. With minimum-ionizing particles in a CERN beam a high efficiency, close to 100%, was measured, under stable conditions. A first space-resolution measurement of
50
μ
m
±20
μ
m was obtained. The operation of the chamber shows that it is possible to optimize the geometrical parameters in order to improve the space resolution and bring the time resolution low enough to contain the events of each beam crossing (every 25
ns) in the European Large Hadron Collider. Further work in this direction is being actively pursued.
The CPLEAR-Experiment at CERN Adler, R.; Alhalel, T.; Angelopoulos, A. ...
Nuclear physics. Section B, Proceedings supplement,
11/1997, Letnik:
59, Številka:
1
Journal Article
Recenzirano
The CPLEAR experiment uses tagged K
0 and
K
0 produced in p
p
annihilation at rest to measure CP-, T- and CPT-violation parameters in the neutral kaon system. The results of these measurements and ...some implications are reported.
The CPLEAR experiment at CERN measures the time dependent decay rate asymmetries of initially pure K
0 and
K
0 states to study CP,T and CPT symmetries in the neutral kaon system. The latest results ...on
η
+−,
Δm and
x are reported, as well as direct tests of T violation and CPT violation in K
0-
K
0 oscillations. Our results are consistent with CPT invariance and allow for an improved limit on the K
0-
K
0 mass difference. Further, a possible loss of quantum coherence of the neutral kaon system has been tested to a level near the Planck scale.
The development of the optical discriminator Atac, M.; Charpak, G.; Chipaux, R. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/1995, Letnik:
367, Številka:
1
Journal Article
Recenzirano
New results from the tests of the impact parameter discriminator by the RD30 Collaboration are presented. The device, based on the detection of Cherenkov light produced in a thin crystal, is able to ...cope with extremely high rates in the GHz range and sign tracks with non-zero impact parameter at a first trigger level. We report experimental results obtained with a sapphire shell surrounded by a liquid cladding compensating chromatic dispersion. An excellent signal to background ratio has been obtained and the sensitivity at low impact parameters reaches the requirements for efficient B-meson selection. The use of such a device for hyperon selection will also be discussed.
The CPLEAR detector at CERN Adler, R.; Albrecht, W.; Alhalel, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/1996, Letnik:
379, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using K
0 and
K
0 produced by the annihilation of
p
's in a hydrogen gas ...target. The K
0 and
K
0 are identified by their companion products of the annihilation K
±
π
∓ which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the subdetectors are described.
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