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.
The LHCb Outer Tracker is a gaseous detector covering an area of \(5\times 6 m^2\) with 12 double layers of straw tubes. The performance of the detector is presented based on data of the LHC Run 2 ...running period from 2015 and 2016. Occupancies and operational experience for data collected in \(p p\), pPb and PbPb collisions are described. An updated study of the ageing effects is presented showing no signs of gain deterioration or other radiation damage effects. In addition several improvements with respect to LHC Run 1 data taking are introduced. A novel real-time calibration of the time-alignment of the detector and the alignment of the single monolayers composing detector modules are presented, improving the drift-time and position resolution of the detector by 20\%. Finally, a potential use of the improved resolution for the timing of charged tracks is described, showing the possibility to identify low-momentum hadrons with their time-of-flight.
Results from the BABAR electromagnetic calorimeter beam test Barlow, Roger J.; Bernet, Roland; Bowdery, Christopher K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
1999, 1999-1-00, Volume:
420, Issue:
1
Journal Article
Peer reviewed
Open access
We present results from the PSI test beam run for the electromagnetic calorimeter of the BABAR experiment. A system of 25 CsI(Tl) crystals was tested with electrons and pions in the momentum range ...from 100 to 405
MeV/
c. Results are presented on crystal light output, on coherent and incoherent noise, on energy resolution and on spatial resolution. The design energy resolutions of the Technical Design Report of BABAR were achieved.
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.
Using the ARGUS detector at the
e
+
e
− storage ring DORIS II, we have determined the Michel parameters ξ and δ of
τ
∓ → l
∓ν
ν
-
decays. With an integrated luminosity of 445 pb
−1 around
s
= 10
GeV, ...we have produced approximately 415000 τ-pairs. From this data sample, 3262 events were selected with
e
+e
− → τ
+τ
− → (l
±ν
ν
-
) (π
∓π
+π
−ν)
. The semihadronic decay was used as analyser of the τ-spin and made possible - owing to the spin correlations - the determination of the parity-violating Michel parameters ξ and δ in the decay
τ
∓ → l
∓ν
ν
-
. Simultaneously to the determination of the Michel parameters, a measurement of the τ-neutrino helicity
h
ν
τ
in the decay
τ
∓ →
π
∓
π
+
π
−
ν was obtained. We observed
h
ν
τ
= −0.85
−0.17
+0.15 ± 0.05,
ϱ = 0.721 ± 0.040 ± 0.021,
ξ = 1.26
−0.26
+0.30 ± 0.09, and
ξδ = 0.77
−0.16
+0.18 ± 0.05. In addition, the combined ARGUS result on
h
ν
τ
, ϱ, ξ, and ξδ are reported using this work and previous measurements.
Using the ARGUS detector at the
e
+
e
− storage ring DORIS II at DESY, we have studied lepton energy spectra in τ decays. We present a “pseudo-rest-frame” technique in which the second τ in the ...event, decaying into a heavy hadronic system, is used as reference. This method allows for the first measurement of the Michel Parameter η in τ decays. We also determine the Michel Parameter ρ in τ →
ev̄v decays with a precision comparable to the present world average. The measured values of the parameters ρ=0.735±0.036±0.020 and η=0.03±0.18±0.12 are in good agreement with standard V-A coupling at the τ-ν-W vertex.
The LHCb Outer Tracker is a gaseous detector covering an area of 5x6 m2 with 12 double layers of straw tubes. The detector with its services are described together with the commissioning and ...calibration procedures. Based on data of the first LHC running period from 2010 to 2012, the performance of the readout electronics and the single hit resolution and efficiency are presented. The efficiency to detect a hit in the central half of the straw is estimated to be 99.2%, and the position resolution is determined to be approximately 200 um. The Outer Tracker received a dose in the hottest region corresponding to 0.12 C/cm, and no signs of gain deterioration or other ageing effects are observed.
The LHCb experiment at the European Organization for Nuclear Research (CERN) is dedicated to precision measurements of CP violation and rare decays of B hadrons. Its most sensitive components are ...protected by means of a Beam Conditions Monitor (BCM), based on polycrystalline CVD diamond sensors. Its configuration, operation and decision logics to issue or remove the beam permit signal for the Large Hadron Collider (LHC) are described in this paper.
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