The high-intensity hyperon beam at CERN Alexandrov, Yu.A; Clement, M; Dropmann, F ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/1998, Letnik:
408, Številka:
2-3
Journal Article
A transition radiation detector has been built for the CERN hyperon beam experiment WA89. The task of this detector is to reject at an early trigger stage beam pions, which are more than twice as ...abundant as hyperons. Special requirements were imposed by the high beam flux and the need for an early trigger signal. Setup and performance of the detector are presented.
We present the set-up and performance of a high energy neutron trigger based on a detector system consisting of a scintillating tile hodoscope and a compensating lead/scintillating fibre calorimeter. ...A first level trigger signal is generated by a minimum hadronic energy detected in the fiducial volume of the calorimeter. This signature is complemented at a second trigger stage by the isolation of a shower whose origin cannot be attributed to a charged particle. We detect such a topology by comparing the hit pattern of the hodoscope with online available calorimeter information. This complex task can be fulfilled in an efficient and flexible way by Digital Signal Processors (DSP). The presented method of online neutron detection was developed in the framework of the hyperon beam experiment WA89 at CERN and yields an average trigger decision time of ≈11 μs. From an analysis based on
Σ
− decays (
Σ
− → n
π
−), we find a second level trigger efficiency for neutrons of 70% at a refection level of 95% for hadronic showers originating from charged particles.
During 1993 and 1995 LEP was run at 3 energies near the Z\(^0\) peak in order to give improved measurements of the mass and width of the resonance. During 1994, LEP operated only at the Z\(^0\) peak. ...In total DELPHI accumulated data corresponding to an integrated luminosity of approximately 116 pb\(^{-1}\). Analyses of the hadronic cross-sections and of the cross-sections and forward-backward asymmetries in the leptonic channels used the most precise evaluations of the LEP energies. In the dimuon channel, events with a photon radiated from the initial state have been used to probe the cross-sections and asymmetries down to PETRA energies. Model independent fits to all DELPHI lineshape and asymmetry data from 1990 to 1995 have been carried out giving values of the resonance parameters:These values are significantly more precise than those previously published. The results are interpreted in terms of the Standard Model.
mb at MZ Andersson, P; Andreazza, A; Augustinus, A ...
Physics letters. B,
02/1998, Letnik:
418, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The value of the
b quark mass at the
M
Z
scale defined in the
MS
renormalization scheme,
m
b
(
M
Z
), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI ...detector to be
m
b(M
Z)=2.67±0.25
(
stat.)±0.34
(
frag.)±0.27
(
theo.)
GeV/c
2
.
The analysis considers NLO corrections to the three-jet production rate including mass effects, and the result obtained agrees with the QCD prediction of having a running
b quark mass at an energy scale equal to
M
Z
. This is the first time that such a measurement is performed far above the
b
b
production threshold. The study also verifies the flavour independence of the strong coupling constant for
b and light quarks within 1% accuracy.
Production of V0 pairs in the hyperon experiment WA89 Adamovich, M.I.; Alexandrov, Yu.A.; Baranov, S.P. ...
The European physical journal. C, Particles and fields,
12/2007, Letnik:
52, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We present a comprehensive study of the inclusive production of V0V0 pairs (V0=Λ, Λ̄ or KS ) by Σ- and π- of 340 GeV/c momentum and neutrons of 260 GeV/c mean momentum in copper and carbon targets. ...In particular, the dependence of the xF spectra on the combination of beam-particle and produced V0V0 pair is investigated and compared to predictions obtained from PYTHIA and QSGM calculations. The data and these predictions differ in many details, the agreement can at best be termed as qualitative. A signal from decays of the tensor meson f’2(1525) was observed in the KS KS mass distribution and inclusive production cross sections were measured. No signal was found from the double-strange H-dibaryon decaying to ΛΛ.
We present a comprehensive study of the inclusive production of $V^{0}V^{0}$ pairs ($V^{0}=\Lambda, \bar\Lambda or K_S$) by $\Sigma^-$ and $\pi^-$ of 340 GeV/c momentum and neutrons of 260 GeV/c mean ...momentum in copper and carbon targets. In particular, the dependence of the $x_F$ spectra on the combination of beam-particle and produced $V^{0}V^{0}$ pair is investigated and compared to predictions obtained from PYTHIA and QSGM calculations. The data and these predictions differ in many details, the agreement can at best be termed as qualitative. A signal from decays of the tensor meson $f'_2$(1525) was observed in the K_S K_S mass distribution and inclusive production cross sections were measured. No signal was found from the double-strange H-dibaryon decaying to $\Lambda \Lambda$.
We report on the observation of a KSp resonance signal at a mass of 1765 ± 5 MeV/c2, with intrinsic width Γ = 108 ± 22 MeV/c2, produced inclusively in Σ--nucleus interactions at 340 GeV/c in the ...hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra.
m(b) at M-Z Abreu, P; Adam, W; Adye, T ...
Physics letters. B,
02/1998, Letnik:
418, Številka:
3-4
Journal Article
Recenzirano
Odprti dostop
The value of the Lr quark, mass at the M-Z scale defined in the <(MS)over bar> renormalization scheme, m(b)(M-Z), was determined using 2.8 million hadronic Z decays collected during 1992-1994 ...by the DELPHI detector to be m(b)(M-Z) = 2.67 +/- 0.25 (stat.)
We report on the observation of a K$_S$p resonance signal at a mass of 1765 ± 5 MeV/c/$^ $2, with intrinsic width Γ = 108 ± 22 MeV/c$^2$, produced inclusively in Σ$^-$-nucleus interactions at 340 ...GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra.
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