PACIFIC: SiPM readout ASIC for LHCb upgrade de Cos, José Mazorra; Chanal, Hervé; Comerma Montells, Albert ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2018, Letnik:
912
Journal Article
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A new 64-channel mixed-signal ASIC is presented: PACIFIC. It was developed in TSMC 130 nm CMOS technology for the readout of the Scintillating Fibre Tracker, as a part of the LHCb upgrade. This ...detector is based on 250 μ m scintillating fibers readout by custom designed 128-channel silicon photomultiplier arrays. It will cover a total area of 340 m2, distributed over the 12 planes that compose it. The sensors are connected directly to PACIFIC without any interface components. The ASIC acquires the current pulses using a current conveyor. A fast double pole-zero cancellation shaper is used to minimize spillover. The charge is then collected using gated integrators, with a twofold interleaved scheme to minimize dead time. The resulting voltage level is digitized with a configurable 2 bit non-linear flash ADC. The output is a 320 Mbps differential signal produced by the serializers, which gather the results from four adjacent channels.
•A new mix-signal silicon photomultiplier readout ASIC is presented.•Direct anode connection with voltage and impedance control at this node.•Fast shaping and integration with configurable 2-bit non-linear output.•It has demonstrated single photoelectron detection capability.
The decay B 0 → DK *0 and the charge conjugate mode are studied using 1.0 fb−1 of pp collision data collected by the LHCb experiment at s√=7s=7 TeV in 2011. The CP asymmetry between the B 0 → DK *0 ...and the B⎯⎯⎯⎯0→DK⎯⎯⎯⎯∗0B¯0→DK¯∗0 decay rates, with the neutral D meson in the CP-even final state K + K −, is found to be
KKd=−0.45±0.23±0.02,
AdKK=−0.45±0.23±0.02,
where the first uncertainty is statistical and the second is systematic. In addition, favoured B 0 → DK *0 decays are reconstructed with the D meson in the non-CP eigenstate K +π−. The ratio of the B-flavour averaged decay rates in D decays to CP and non-CP eigenstates is measured to be
KKd=1.36+0.37−0.32±0.07,
RdKK=1.36−0.32+0.37±0.07,
where the ratio of the branching fractions of D 0 → K −π+ to D 0 → K + K − decays is included as multiplicative factor. The CP asymmetries measured with two control channels, the favoured B 0 → DK *0 decay with D → K +π− and the B⎯⎯⎯⎯0s→DK∗0B¯s0→DK∗0 decay with D→K + K −, arealsoreported.
Avalanche photodiodes operated in the Geiger mode offer a high intrinsic gain as well as an excellent timing accuracy. These qualities make the sensor specially suitable for those applications where ...detectors with high sensitivity and low timing uncertainty are required. Moreover, they are compatible with standard CMOS technologies, allowing sensor and front-end electronics integration within the pixel cell. However, the sensor suffers from high levels of intrinsic noise, which may lead to erroneous results and limit the range of detectable signals. They also increase the amount of data that has to be stored. In this work, we present a pixel based on a Geiger-mode avalanche photodiode operated in the gated mode to reduce the probability to detect noise counts interfering with photon arrival events. The readout circuit is based on a two grounds scheme to enable low reverse bias overvoltages and consequently lessen the dark count rate. Experimental characterization of the fabricated pixel with the HV-AMS 0.35µm standard technology is also presented in this article.
Decays of ¯ B 0 s and ¯ B 0 mesons into J / ψ π + π − π + π − final states, produced in p p collisions at the LHC, are investigated using data corresponding to an integrated luminosity of 3 fb − ...1 collected with the LHCb detector. ¯ B 0 ( s ) → J / ψ f 1 ( 1285 ) decays are seen for the first time, and the branching fractions are measured. Using these rates, the f 1 ( 1285 ) mixing angle between strange and nonstrange components of its wave function in the q ¯ q structure model is determined to be ± ( 24 . 0 + 3.1 + 0.6 − 2.6 − 0.8 ) ° . Implications on the possible tetraquark nature of the f 1 ( 1285 ) are discussed.
We present a measurement of form-factor-independent angular observables in the decay B 0 → K ∗ ( 892 ) 0 μ + μ − . The analysis is based on a data sample corresponding to an integrated luminosity of ...1.0 fb − 1 , collected by the LHCb experiment in p p collisions at a center-of-mass energy of 7 TeV. Four observables are measured in six bins of the dimuon invariant mass squared q 2 in the range 0.1 < q 2 < 19.0 GeV 2 / c 4 . Agreement with recent theoretical predictions of the standard model is found for 23 of the 24 measurements. A local discrepancy, corresponding to 3.7 Gaussian standard deviations is observed in one q 2 bin for one of the observables. Considering the 24 measurements as independent, the probability to observe such a discrepancy, or larger, in one is 0.5%.
Observation of the Decay B+c→B0sπ Calvo Gómez, Míriam; Camboni, Alessandro; Comerma Montells, Albert ...
Physical review letters,
11/2013
Journal Article
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The result of a search for the decay B + c → B 0 s π + is presented, using the B 0 s → D − s π + and B 0 s → J / ψ ϕ channels. The analysis is based on a data sample of p p collisions collected with ...the LHCb detector, corresponding to an integrated luminosity of 1 fb − 1 taken at a center-of-mass energy of 7 TeV, and 2 fb − 1 taken at 8 TeV. The decay B + c → B 0 s π + is observed with significance in excess of 5 standard deviations independently in both decay channels. The measured product of the ratio of cross sections and branching fraction is σ ( B + c ) / σ ( B 0 s ) × B ( B + c → B 0 s π + ) = 2.37 ± 0.31 ( stat ) ± 0.11 ( syst ) + 0.17 − 0.13 ( τ B + c ) × 10 − 3 , in the pseudorapidity range 2 < η ( B ) < 5 , where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the B + c lifetime. This is the first observation of a B meson decaying to another B meson via the weak interaction.
A search for the rare decays B 0 s → μ + μ − and B 0 → μ + μ − is performed at the LHCb experiment. The data analyzed correspond to an integrated luminosity of 1 fb − 1 of p p collisions at a ...center-of-mass energy of 7 TeV and 2 fb − 1 at 8 TeV. An excess of B 0 s → μ + μ − signal candidates with respect to the background expectation is seen with a significance of 4.0 standard deviations. A time-integrated branching fraction of B ( B 0 s → μ + μ − ) = ( 2.9 + 1.1 − 1.0 ) × 10 − 9 is obtained and an upper limit of B ( B 0 → μ + μ − ) < 7.4 × 10 − 10 at 95% confidence level is set. These results are consistent with the standard model expectations.
The ratio of the Λ 0 b baryon lifetime to that of the ¯¯¯ B 0 meson is measured using 1.0 fb − 1 of integrated luminosity in 7 TeV center-of-mass energy p p collisions at the LHC. The Λ 0 b ...baryon is observed for the first time in the decay mode Λ 0 b → J / ψ p K − , while the ¯¯¯ B 0 meson decay used is the well known ¯¯¯ B 0 → J / ψ π + K − mode, where the π + K − mass is consistent with that of the ¯¯¯¯ K * 0 ( 892 ) meson. The ratio of lifetimes is measured to be 0.976 ± 0.012 ± 0.006 , in agreement with theoretical expectations based on the heavy quark expansion. Using previous determinations of the ¯¯¯ B 0 meson lifetime, the Λ 0 b lifetime is found to be 1.482 ± 0.018 ± 0.012 ps . In both cases, the first uncertainty is statistical and the second systematic.
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