The performance of the muon identification in LHCb is extracted from data using muons and hadrons produced in J/psi arrow right mu super(+) mu super(-) , Lambda super(0) arrow right ppi super(-) and ...D* super(+) arrow right pi super(+)D super(0)(K super(-)pi super(+)) decays. The muon identification procedure is based on the pattern of hits in the muon chambers. A momentum dependent binary requirement is used to reduce the probability of hadrons to be misidentified as muons to the level of 1%, keeping the muon efficiency in the range of 95-98%. As further refinement, a likelihood is built for the muon and non-muon hypotheses. Adding a requirement on this likelihood that provides a total muon efficiency at the level of 93%, the hadron misidentification probabilities are below 0.6%.
A LYSO calorimeter for the SuperB factory Eigen, G.; Zhou, Z.; Chao, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
Odprti dostop
The SuperB project is an asymmetric e+e− accelerator of 1036cm−2s−1 design luminosity, capable of collecting a data sample of 50–75ab−1 in five years running. The SuperB electromagnetic calorimeter ...(EMC) provides energy and direction measurement of photons and electrons, and is used for identification of electrons versus other charged particles. In particular we present its design, geometry study and related simulations, as well as R&D on LYSO crystals and developments on readout electronics. A matrix of 25 crystals has been tested at the Beam Test Facility of Frascati (BTF) in May 2011 at energies between 200MeV and 500MeV. Results from this test are presented.
The performance of different types of multi-wire proportional chambers belonging to the LHCb Muon System was tested in laboratory with cosmic rays. The detection efficiency, the time and spatial ...resolution were measured and the high-voltage working region of these chambers was determined. These tests provide information which is complementary to those obtained in the final LHCb apparatus.
A new method has been developed to check the correct behaviour of the frontend electronics of the LHCb muon detector. This method is based on the measurement of the electronic noise rate at different ...thresholds of the front-end discriminator. The method was used to choose the optimal discriminator thresholds. A procedure based on this method was implemented in the detector control system and allowed the detection of a small percentage of front-end channels which had deteriorated. A Monte Carlo simulation has been performed to check the validity of the method.
The possibilty of performing high-rate calorimetry with a slow scintillating crystal is studied. In this experimental situation, to avoid pulse pile-up, it can be necessary to base the energy ...measurement on only a fraction of the emitted light, thus spoiling the energy resolution. This effect was experimentally studied with a BGO crystal and a photomultiplier followed by an integrator, by measuring the maximum amplitude of the signals. The experimental data show that the energy resolution is exclusively due to the statistical fluctuations of the number of photoelectrons contributing to the maximum amplitude. When such number is small its fluctuations are even smaller than those predicted by Poisson statistics. These results were confirmed by a Monte Carlo simulation which allows to estimate, in a general case, the energy resolution, given the total number of photoelectrons, the scintillation time and the integration time.
Performance of the LHCb muon system Alves, AA Jr; Anderlini, L; Anelli, M ...
Journal of instrumentation,
02/2013, Letnik:
7, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The performance of the LHCb Muon system and its stability across the full 2010 data taking with LHC running at square root s = 7 TeV energy is studied. The optimization of the detector setting and ...the time calibration performed with the first collisions delivered by LHC is described. Particle rates, measured for the wide range of luminosities and beam operation conditions experienced during the run, are compared with the values expected from simulation. The space and time alignment of the detectors, chamber efficiency, time resolution and cluster size are evaluated. The detector performance is found to be as expected from specifications or better. Notably the overall efficiency is well above the design requirements.
The SuperB project is an asymmetric e+e− accelerator of 1036 cm−2s−1 luminosity, capable of collecting a 50–75 ab−1 data sample in five years of running. The SuperB electromagnetic calorimeter (EMC) ...provides energy and direction measurement of photons and electrons and identification versus other charged particles for electrons. A matrix of 25 LYSO crystals has been tested at the Beam Test Facility at Frascati in May 2011 at energies between 100 MeV and 500 MeV. Results from this test will be presented. Design and Monte Carlo studies for the general EMC system will also be presented.
The performance demanded for the Level-0 trigger of LHCb imposes very stringent requirements on the quality of the muon chambers. These chambers must pass a series of tests before being mounted in ...the experimental setup. The six tests adopted for the quality control of the chambers produced at the Laboratori Nazionali di Frascati (LNF) are described. After the wires are wound and glued on a cathode panel, the wire pitch is measured by two digital cameras with a precision of about 20 mum. The mechanical tension of the wire is deduced from its mechanical resonance frequency measured by an automated system based on a digital electrostatic method. The wire tension is obtained with a precision of about 1%. Once all elements are assembled, the gas tightness of a chamber is verified by monitoring the decrease rate of an overpressure applied to it. After a suitable high-voltage conditioning, the dark current is recorded and the gas gain uniformity of the chamber is measured using a collimated 137 Cs source which can be moved over the chamber surface. Finally, the detector is fully equipped with the front-end electronics, and its detection efficiency is tested with cosmic rays
Charmed-meson production by 350 GeV/c π
− particles incident on copper and tungsten targets has been studied in the WA92 experiment, performed at the CERN Ω′ spectrometer. Results obtained are ...reported and discussed. Reconstruction of decays from the set D
0 → K
−
π
+ D
0 → K
−
π
−
π
+
π
+, D
s
+ →
φπ
+ and charge conjugates has yielded a sample of 7280 ± 108 charmed mesons, produced with
χ
F
> 0, (
χ
F
) = 0.18 and〈
p
T
2〉 = 1.86 (
GeV/
c)
2. Assuming a relationship
σ =
σ
0
A
α
between the cross section, σ, per nucleus of mass
A and the nucleonic cross section,
σ
0 the α value found for the detected charmed particles is 0.95 ± 0.06 ± 0.03. Taking
α = 1, the measured cross sections per nucleon for
χ
F
> 0 production are 7.78 ± 0.14 ± 0.52
μb for
D
0/
D
0, 3.28 ± 0.08 ± 0.29 μ
b
for D
+/D
− and 1.29 ± 0.16 ± 0.33
μb for D
s
+/D
s
−. Differential cross sections with respect to
χ
F
and
p
T
2 have been determined for the various types of charmed meson, and particle-antiparticle asymmetries have been analysed.
The muon detector of LHCb, which comprises 1368 multi-wire-proportional-chambers (MWPC) for a total area of 435 m
2
, is the largest instrument of its kind exposed to such a high-radiation ...environment. In nine years of operation, from 2010 until 2018, we did not observe appreciable signs of ageing of the detector in terms of reduced performance. However, during such a long period, many chamber gas gaps suffered from HV trips. Most of the trips were due to Malter-like effects, characterised by the appearance of local self-sustained high currents, presumably originating from impurities induced during chamber production. Very effective, though long, recovery procedures were implemented with a HV training of the gaps in situ while taking data. The training allowed most of the affected chambers to be returned to their full functionality and the muon detector efficiency to be kept close to 100%. The possibility of making the recovery faster and even more effective by adding a small percentage of oxygen in the gas mixture has been studied and successfully tested.
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