New Crystal Barrel data are reported for
p
̄
p→ωπ
0
and
p
̄
p→ωηπ
0
with
ω decaying to
π
+
π
−
π
0. The shapes of angular distributions agree well with those for data where
ω→
π
0
γ; this is a ...valuable cross-check on systematic errors. The new data provide good measurements of vector and tensor polarisations
P
y
,
T
20,
T
21 and
T
22 of the
ω. These lead to significant improvements in parameters of several resonances reported earlier. New values of masses and widths (in MeV) are:
J
PC
=5
−− (2300±45, 260±75),
J
PC
=3
−− (2260±20, 160±25),
J
PC
=1
+− (2240±35, 320±85), and
J
PC
=1
−− (2110±35, 230±50). A remarkable feature of the data is that vector polarisation
P
y
is close to zero everywhere. It follows that all interfering amplitudes have relative phases close to 0 or 180°. Tensor polarisations are large.
New Crystal Barrel data are reported for
p
̄
p→ωη
and
p
̄
p→ωπ
0π
0
with
ω decaying to
π
+
π
−
π
0. The
ωη data confirm angular distributions obtained earlier from data where
ω→
π
0
γ. The new
ωη ...data provide accurate measurements of vector and tensor polarisations of the
ω and lead to considerable improvements in masses and widths of
s-channel resonances. A new
J
PC
=3
+−
I=0 resonance is observed with mass
M=2025±20 MeV and width
Γ=145±30 MeV. Polarisation is close to zero everywhere and tensor polarisations are large, as is the case also for
p
̄
p→ωπ
0
.
The goal of the DIRAC experiment at CERN (PS212) is to measure the π+π− atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering ...lengths combination |a0−a2|. Based on part of the collected data we present a first result on the lifetime, τ=2.91−0.62+0.49×10−15 s, and discuss the major systematic errors. This lifetime corresponds to |a0−a2|=0.264−0.020+0.033mπ−1.
The properties of the scalars (0
++) below 2 GeV are reviewed. Particular attention is given to the observation of these scalars in proton-antiproton annihilations at rest in liquid hydrogen.
Review of particle properties Montanet, L; Gieselmann K Technical Associate; Barnett, RM ...
Physical review. D, Particles and fields,
08/1994, Letnik:
50, Številka:
3
Journal Article
This biennial review summarizes much of Particle Physics. Using data from previous editions, plus 2300 new measurements from 700 papers, we list evaluate, and average measured properties of gauge ...bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, monopoles, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full ital Review.
DIRAC: A high resolution spectrometer for pionium detection Adeva, B.; Afanasyev, L.; Benayoun, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2003, Letnik:
515, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The DIRAC spectrometer has been commissioned at CERN with the aim of detecting π+π− atoms produced by a 24GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to ...cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum and the measurement of the latter with resolution around 0.6MeV/c. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and set-up performances are also given.
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