In the harsh environment of the Large Hadron Collider at CERN (design luminosity of 10 34 cm −2 s −1 ) efficient reconstruction of vertices is crucial for many physics analyses. Described in this ...paper are the strategies for vertex reconstruction used in the ATLAS experiment and their implementation in the software framework Athena. The algorithms for the reconstruction of primary and secondary vertices as well as for finding of photon conversions and vertex reconstruction in jets are described. A special emphasis is made on the vertex fitting with application of additional constraints. The implementation of mentioned algorithms follows a very modular design based on object-oriented C++ and use of abstract interfaces. The user-friendly concept allows event reconstruction and physics analyses to compare and optimize their choice among different vertex reconstruction strategies. The performance of implemented algorithms has been studied on a variety of Monte Carlo samples and results are presented.
The ηππ and ωω systems produced in the
π
−
Be interactions with 37GeV/
c
π
− beam have been studied at the VES spectrometer. For the unnatural-parity exchange, the isoscalar channels demonstrate ...similar structures in
ηπ
−
π
+ and ωω final states, while the amplitudes with
I = 1 have the same behaviour for
ηπ
+
π
−
π
0. The
I = 0
J
PC
= 2
++ amplitudes show the signal of
f
2(1565) meson which decays to
a
2(1320)
π
− and ωω. The
f
2(1920) meson is observed in ωω. In the
I = 0
J
PC
= 4
++ intensities there are signals from
f
4(2050) and
f
4(2330) mesons.
The
I = 1
J
PC
= 3
−− waves demonstrate the presence of
p
3(1690) meson in
a
2(1320)
π and
pη decay modes. 3
−− waves at higher masses have complex behaviour and can be modelled by the further 3
−− resonances.
Natural parity resonances in ηπ+π Amelin, D; Berdnikov, E; Bityukov, S ...
Nuclear physics. A,
3/2000, Letnik:
668, Številka:
1
Journal Article
Recenzirano
Results of a partial wave analysis of the
ηπ
+
π
− final state are presented using 4.2×10
4 events with |
t|<0.2 GeV
2, collected at the VES setup; the reaction is
π
−
p→
π
−
π
+
ηn from a beryllium ...target. The data reveal resonant structures, which are identified by phase motion as well as peaks in intensities of partial waves. The
f
2(1565) meson, also called the
AX meson, is observed in decays to
a
2(1302)
π
L=1
. The parameters obtained from a fit with a Breit–Wigner amplitude are
M=1550±20 MeV with
Γ=130±40 MeV. The higher mass
f
2 resonances are also discussed. For
J
P
=3
−, the well known
ρ
3(1690) is seen in decays to both
a
2(1320)
π and
ρη channels. The complex behaviour of 3
−− amplitudes at higher masses is described best by introducing two additional resonant poles near 2.14 and 2.30 GeV. There is evidence for an
f
4(2300) meson, decaying dominantly to
f
2
η
L=3
.
Results on beam tests of 3D silicon pixel sensors aimed at the ATLAS Insertable-B-Layer and High Luminosity LHC (HL-LHC)) upgrades are presented. Measurements include charge collection, tracking ...efficiency and charge sharing between pixel cells, as a function of track incident angle, and were performed with and without a 1.6 T magnetic field oriented as the ATLAS Inner Detector solenoid field. Sensors were bump bonded to the front-end chip currently used in the ATLAS pixel detector. Full 3D sensors, with electrodes penetrating through the entire wafer thickness and active edge, and double-sided 3D sensors with partially overlapping bias and read-out electrodes were tested and showed comparable performance.
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