The OBELIX spectrometer, studying at the Low Energy Antiproton Ring (LEAR) of CERN the
N̄N annihilation, has collected annihilation data with very low momentum
p̄(≈ 50
MeV/c). The results of the ...spin-parity analysis on the
p̄p annihilation into four and five pions are briefly described.
TPG, test results Ableev, V.; Ambrosino, F.; Apollonio, M. ...
IEEE transactions on nuclear science,
12/2005, Letnik:
52, Številka:
6
Journal Article
Recenzirano
TPG is the acronym for Time Projection Chamber with GEM amplification, high-granularity hexaboard read-out and FADC electronics. We have constructed a TPG read-out module, called TPG-head, with three ...GEM foils and a multilayer board, called hexaboard, covered with 710 000 hexagonal pads of 300 mum size. The total active area of this module is a disk of 30 cm diameter. The 710 000 pads are read by three sets of 576 strips dephased by 120 degrees. Each strip is read by a FADC channel with 100 ns sampling time. The module is mounted in a test-bed formed by a cylindrical field cage of 80 cm diameter and 150 cm length inside a solenoidal magnet that operates with a magnetic field up to B=0.7 Tesla. Tests with X-ray sources show an intrinsic spatial resolution of the order of 40 mum. The threshold for transverse momentum measurement of low energy tracks is below 0.1 MeV/c with a magnetic field of 0.07 Tesla. At 0.7 Tesla the intrinsic space point resolution of the chamber is such that the error on the measurement of the transverse momentum is DeltaP t sime0.1 MeV/c in absence of distortions from the drift region
TPG construction Ableev, V.; Ambrosino, F.; Apollonio, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2004, Letnik:
535, Številka:
1
Journal Article
Recenzirano
TPG is the acronym for a 3D imaging gas chamber with GEM amplification, hexaboard read-out and FADC electronics. We have constructed a TPG-head with three GEM foils (30
cm diameter) and a read-out ...board (30
cm diameter active surface) covered with 710,000 hexagonal pads of
300
μ
m
size. Aligned pads are connected in parallel to one strip out of three sets of 576 parallel strips (
500
μ
m
pitch). The three sets of strips run at
120
∘
from each other and at three different depths inside the hexaboard multilayer structure. Each strip is read out by FADC electronics. The TPG-head is under initial test in a small container with a drift volume 33
mm long and of 30
cm diameter. A 150
cm long drift volume inside a 0.7
T solenoidal magnetic field has been prepared by using HARP-TPC instrumentation as test bed.
TPG development Ableev, V.; Ambrosino, F.; Apollonio, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
TPG is the acronym for Time Projection chamber with GEM amplification, hexaboard read-out and FADC electronics. We are constructing a TPG read-out module with three GEM foils (30
cm diameter) and a ...read-out board (30
cm diameter active surface) covered with hexagonal pads of 300
μm size. Aligned pads are connected in parallel to one strip out of three sets of parallel strips. Each strip is read by FADC electronics. The test bench for the TPG head will be the HARP-TPC field cage. TPG characteristics, design and expected performances are discussed.
The
p̄p total annihilation cross section has been measured, with the Obelix apparatus at LEAR, at ten values of the antiproton incident momentum between 43 and 175 MeV/
c. The values of the cross ...section show that the well known
1
p
behaviour of the annihilation cross section is drastically modified at very low momenta, which demonstrates the important role of the Coulomb force in low energy
p̄p interaction. Moreover, they do not present any explicit resonant behaviour. Finally, when compared to potential model calculations, the data suggest that the percentage of P-wave in
p̄p interaction around 50 MeV/
c antiproton incident momentum is less than 5%.
A confirming evidence for two pseudoscalar states with masses
M
1=1405±5,
Γ
1=50±4 MeV/
c
2 and
M
2=1500±10,
Γ
2=100±20 MeV/
c
2 is reported. The second pseudoscalar fills the nonet and leaves the ...first as an outsider supporting the hypothesis for its exotic nature.
The
pp
total annihilation cross section has been measured at four values of the
p
̄
incident momentum, between 70 MeV/c and 38 MeV/c, with the Obelix apparatus at LEAR. The new measurements are in ...agreement with the trend of previous measurements of the
pp
total annihilation cross section at low energy, performed by the Obelix experiment A. Bertin et al., Phys. Lett. B 369 (1996) 77; A. Benedettini et al., Nucl. Phys. B (Proc. Suppl.) 56A (1997) 58, as well as with a fit of the latter data based on a low energy expansion of the scattering amplitude J. Carbonell, K.V. Protasov, A. Zenoni, Phys. Lett. B 397 (1997) 345. The departure of the annihilation cross section from a smooth behaviour, suggested by a previous measurement of the cross section around 44 MeV/c A. Bertin et al., Phys. Lett. B 369 (1996) 77, is not confirmed by the new data.
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