As the PEP-II luminosity increases the
B
a
B
ar
trigger and dataflow systems must accomodate the increasing data rate. A significant source of background events at the first trigger level comes from ...the beam particle interactions with the beampipe and synchrotron masks, which are separated from the interaction region by more than
20
cm
. The
B
a
B
ar
trigger upgrade will provide 3D tracking capabilities at the first trigger level in order to remove background events by distinguishing the origin of particle tracks. Each new
z
0
p
T
Discriminator board processes over
1
Gbyte
of data per second in order to reconstruct the tracks and make trigger decisions based upon the 3D track parameters.
Today the B-factories BaBar and Belle have accumulated largest samples of tau-tau events and are competing to be called tau-factories. Among the problems to be tested and measurements to be done by ...BaBar and Belle are check of CP and CPT invariance in tau decays, measurement of strange and non-strange spectral functions, extraction of mass of strange quark and |V_us|, searches for lepton flavor violation processes. In this paper, the latest results in tau physics by these two experiments and measurements to be done within next few years are reviewed.
Moving to the high energy regime of LHC, the identification of tau leptons will become an important and very powerful tool, allowing the discovery of physics beyond the Standard Model. Tools to ...efficiently identify tau lepton at trigger level, based on the advanced calorimetry and tracking capabilities, have been developed for the ATLAS experiment. Commissioning of the tau trigger is presently being carried out. Tau trigger implementation, performance, and commissioning strategy is presented.
Using the ARGUS detector at the
e
+
e
− storage ring DORIS II at DESY, we have found evidence for the production of the excited charmed baryon state
Λ
c
(2593)
+ in the channel
Λ
c
+
π
+
π
−. Its ...mass was determined to be (2594.6±0.9±0.4) MeV/c
2, and the natural width measured to be Γ = (2.9
−2.1−1.4
+2.9+1.8) MeV. The production cross section times the branching ratios of
σ(
e
+
e
− →
Λ
c
(2593)
+
X) ×
Br(
Λ
c
(2593)
+ →
Λ
c
+
π
+
π
−) ×
Br(
Λ
c
+ →
pK
−
π
+) was measured to be (0.25
−0.13
+0.24 ±0.13) pb. The fractions of
Λ
c
(2593)
+ decays proceeding through the
Σ
c
0
π
+ and
Σ
c
++
π
− channels were determined to be 0.29±0.10±0.11 and 0.37±0.12±0.13, respectively.
Using the ARGUS detector at the
e
+
e
− storage ring DORIS II, we have measured the Michel parameters
ρ,
ξ, and
ξδ for
τ
±→l
±ν
ν
̄
decays in
τ-pair events produced at center of mass energies in the ...region of the
ϒ resonances. Using
τ
∓→
ρ
∓
ν as spin analyzing tags, we find
ρ
e
=0.68±0.04±0.08,
ξ
e
=1.12±0.20±0.09,
ξδ
e
=0.57±0.14±0.07,
ρ
μ
=0.69±0.06±0.08,
ξ
μ
=1.25±0.27±0.14 and
ξδ
μ
=0.72±0.18±0.10. In addition, we report the combined ARGUS results on
ρ,
ξ, and
ξδ using this work und previous measurements.
Physics with ARGUS Böckmann, P.; Drews, G.; Gläser, R. ...
Physics reports,
1996, Letnik:
276, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The impact of the ARGUS experiment to elementary particle physics is reviewed. More than ten years of data taking has allowed ARGUS to contribute significantly to our understanding of beauty and ...charmed hadrons, τ Leptons, ϒ mesons, ϒϒ interactions and fragmentation processes. In particular the ARGUS measurements of CKM matrix elements opened up a new window on the Standard Model.
Using the ARGUS detector at the
e
+
e
− storage ring DORIS II at DESY, we have made two measurements of the mixing parameter
χ
d
using kaons as flavour tags. Using
D
∗+ K
±
correlations we found
χ
d
...= 0.20 ± 0.13 ± 0.12 and from the study of
(D
∗+ℓ
−) K
±
correlations we obtained
χ
d
= 0.19 ± 0.07 ± 0.09. The branching ratio for
B → D
∗+ X
has been updated:
Br(
B → D
∗+ X) = (19.6 ± 1.9)
%. We have also determined the average multiplicity of charged kaons in
B
0 decays to be 0.78 ± 0.08.
The ATLAS tau trigger Casado, M.P.; Belanger-Champagne, C.; Benslama, K. ...
Nuclear physics. Section B, Proceedings supplement,
04/2009, Letnik:
189
Journal Article
The implementation of a trigger for hadronically decaying tau leptons at the Large Hadronic Collider (LHC) is challenging due to the high background rate, on the other hand it increases tremendously ...the discovery potential of ATLAS in searches for Standard Model (SM) or Supersymmetric (SUSY) Higgs or other more exotic final states. In this paper we describe the ATLAS tau trigger system, focusing on the early data taking period, and present results from studies based on GEANT 4 simulated events, including trigger rates and the acceptance of tau leptons from SM processes. In order to cope with the rate and optimize the efficiency of important physics channels, the results of the current simulation studies indicate that ATLAS tau triggers should include either relatively high transverse momentum single tau signatures, or low transverse momentum tau signatures in combination with other signatures, such as missing transverse energy, leptons, or jets.
Many theoretical models, like the Standard Model or SUSY at large tan(beta), predict Higgs bosons or new particles which decay more abundantly to final states including tau leptons than to other ...leptons. At the energy scale of the LHC, the identification of tau leptons, in particular in the hadronic decay mode, will be a challenging task due to an overwhelming QCD background which gives rise to jets of particles that can be hard to distinguish from hadronic tau decays. Equipped with excellent tracking and calorimetry, the ATLAS experiment has developed tau identification tools capable of working at the trigger level. This contribution presents tau trigger algorithms which exploit the main features of hadronic tau decays and describes the current tau trigger commissioning activities.
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