Radiation tolerant and controlable power supply design and implementation for the VFE of SPD at LHCB detector

Projecte Final de Carrera d'Enginyeria Electrònica, Universitat de Barcelona, Facultat de Física. Director: Atilà Herms i Berenguer. Any: 2005[cat] En el present projecte, emmarcat en el disseny electrònic de circuits de control, es desenvolupa la font d’alimentació per als circuits de lectura de dades (VFE) del subdetector SPD en el detector LHCb que s’està construint al CERN. Per tant és una de les parts principals que formen aquest subdetector i s’ha d’assegurar la seva robustesa amb el màxim de funcionalitat implementada possible. Cal tenir en compte que tota la electrònica d’aquest subdetector treballarà sota un entorn en radiació i, per tant, s’han de prendre totes les mesures necessàries per assegurar-ne un correcte funcionament en aquest entorn. El sistema de regulació de tensió es basa en reguladors lineals dissenyats de forma específica per a una empresa privada per tal d’assegurar la resistència a la radiació esmentada anteriorment. Pel que respecta el control d’aquesta font s’utilitzen FPGA’s també tolerants a la radiació. La flexibilitat d’aquests dispositius ens permeten implementar tots els elements lògics de control, comunicació i lectura de dades necessaris per a l’aplicació. El disseny del sistema es divideix bàsicament en les següents tasques; definició dels requeriments (que ens vindràn limitats en la seva majoria per les característiques de consum del VFE i de control en el subdetector), selecció dels components a utilitzar en la implementació electrònica, disseny dels esquemes necessaris, disseny del circuit impres, prototipatge del circuit i posta en marxa, codificació en un llenguatge de descripció de hardware (VHDL) de les funcions de control i finalment la comprovació del correcte funcionament del hardware. Degut a les necessitats de control d’aquesta aplicació també s’hauran de realitzar dissenys de circuits auxiliars i de software per tal de comprovar el correcte funcionament del prototip. Aquest projecte representa un bon exemple del desenvolupament complet d’un disseny de hardware mixte digital/analògic basat en una FPGA en l’àmbit de la recerca.[eng] In the present project we present the developement of the electronic system of the low voltage power supply of the VFE board of the SPD subdetector in the LHCb detector that is being built at CERN. This is a fundamental part to assure the correct behaviour of the subdetector system. In this design we must take into account that all the electronics of the subdetector will be exposed to relevant levels of radiation and use the components most suituable to work in this environment. The voltage regulator system is based in linear regulators designed by a comercial manufacturer specially for this purpose of working under radiation conditions. In the control part we will use FPGA’s wick are also radiation tolerant. The flexibility of this devices will perit the implementation of all the logic elements of control, comunications and data readout necessary for this aplication. The design of the whole system will follow this steps; definititon of the specifications (basically determined by the power consumption of the VFE and the comunications system used at the subdetector), selection of the components wich will be used, schematics design, printed circuit board design, prototiping, coding of the FPGA funcionality in VHDL and finally checking of the complete design behaviour. In addition and because of the control nature of this design there would be necessary to design some auxiliar hardware and to code some software in order to check the correct behaviour of the prototype. This project represents a good example of a complete hardware developement of a mixed signal system (analog and digital) in the research scope

Low noise pixel detectors based on gated geiger mode avalanche photodiodes

The gated operation is proposed as an effective method to reduce the noise in pixel detectors based on Geiger mode avalanche photodiodes. A prototype with the sensor and the front-end electronics monolithically integrated has been fabricated with a conventional HV-CMOS process. Experimental results demonstrate the increase of the dynamic range of the sensor by applying this technique

Readout electronics for low dark count pixel detectors based on geiger mode avalanche photodiodes fabricated in conventional CMOS technologies for future linear colliders

The high sensitivity and excellent timing accuracy of Geiger mode avalanche photodiodes makes them ideal sensors as pixel detectors for particle tracking in high energy physics experiments to be performed in future linear colliders. Nevertheless, it is well known that these sensors suffer from dark counts and afterpulsing noise, which induce false hits (indistinguishable from event detection) as well as an increase of the necessary area of the readout system. In this work, we present a comparison between APDs fabricated in a high voltage 0.35 µm and a high integration 0.13 µm commercially available CMOS technologies that has been performed to determine which of them best fits the particle collider requirements. In addition, a readout circuit that allows low noise operation is introduced. Experimental characterization of the proposed pixel is also presented in this work

Study of B0(s)→K0Sh+h′− decays with first observation of B0s→K0SK±π∓ and B0s→K0Sπ+π

A search for charmless three-body decays of B 0 and B0s mesons with a K0S meson in the final state is performed using the pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected at a centre-of-mass energy of 7 TeV recorded by the LHCb experiment. Branching fractions of the B0(s)→K0Sh+h′− decay modes (h (′) = π, K), relative to the well measured B0→K0Sπ+π− decay, are obtained. First observation of the decay modes B0s→K0SK±π∓ and B0s→K0Sπ+π− and confirmation of the decay B0→K0SK±π∓ are reported. The following relative branching fraction measurements or limits are obtained $ B(B0→K0SK±π∓)B(B0→K0Sπ+π−)=0.128±0.017(stat.)±0.009(syst.),B(B0→K0SK+K−)B(B0→K0Sπ+π−)=0.385±0.031(stat.)±0.023(syst.),B(B0s→K0Sπ+π−)B(B0→K0Sπ+π−)=0.29±0.06(stat.)±0.03(syst.)±0.02(fs/fd),B(B0s→K0SK±π∓)B(B0→K0Sπ+π−)=1.48±0.12(stat.)±0.08(syst.)±0.12(fs/fd)B(B0s→K0SK+K−)B(B0→K0Sπ+π−)∈[0.004;0.068]at90%CL

PACIFIC: the readout ASIC for the SciFi Tracker of the upgraded LHCb detector

The LHCb detector will be upgraded during the Long Shutdown 2 (LS2) of the LHC in order to cope with higher instantaneous luminosities and will switch to a 40 MHz readout rate using a trigger-less software based system. All front-end electronics will be replaced and several sub-detectors must be redesigned to cope with the higher detector occupancy and radiation damage. The current tracking detectors downstream of the LHCb dipole magnet will be replaced by the Scintillating Fibre (SciFi) Tracker. The SciFi Tracker will use scintillating fibres read out by Silicon Photomultipliers (SiPMs). State-of-the-art multi-channel SiPM arrays are being developed and a custom ASIC, called the low-Power ASIC for the sCIntillating FIbres traCker (PACIFIC), will be used to digitise the signals from the SiPMs. This article presents an overview of the R&D for the PACIFIC. It is a 64-channel ASIC implemented in 130 nm CMOS technology, aiming at a radiation tolerant design with a power consumption below 10 mW per channel. It interfaces directly with the SiPM anode through a current mode input, and provides a configurable non-linear 2-bit per channel digital output. The SiPM signal is acquired by a current conveyor and processed with a fast shaper and a gated integrator. The digitization is performed using a three threshold non-linear flash ADC operating at 40 MHz. Simulation and test results show the PACIFIC chip prototypes functioning well

Differential branching fraction and angular analysis of the decay B 0 → K ∗0 μ + μ -

The angular distribution and differential branching fraction of the decay B 0→ K ∗0 μ + μ − are studied using a data sample, collected by the LHCb experiment in pp collisions at s√=7 TeV, corresponding to an integrated luminosity of 1.0 fb−1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions

First measurement of time-dependent CP violation in B0s→K+K− decays

Direct and mixing-induced CP-violating asymmetries in B0s→K+K− decays are measured for the first time using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb−1, collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C KK  = 0.14 ± 0.11 ± 0.03 and S KK  = 0.30 ± 0.12 ± 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B 0 → π + π − decays to be C ππ  = −0.38 ± 0.15 ± 0.02 and S ππ  = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements

A study of the Z production cross-section in pp collisions at s√=7 TeV using tau final states

A measurement of the inclusive Z → ττ cross-section in pp collisions at s√=7TeV is presented based on a dataset of 1.0 fb−1 collected by the LHCb detector. Candidates for Z → τ τ decays are identified through reconstructed final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. The production cross-section for Z bosons, with invariant mass between 60 and 120 GeV/c 2, which decay to τ leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5, is measured to be σ pp→Z→ττ = 71.4 ± 3.5 ± 2.8 ± 2.5 pb; the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty on the integrated luminosity. The ratio of the cross-sections for Z → τ τ to Z → μμ is determined to be 0.93 ± 0.09, where the uncertainty is the combination of statistical, systematic, and luminosity uncertainties of the two measurements

Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of B0s meson decays to J/ψη and J/ψη′

First evidence of the B0 → J/ψω decay is found and the B0 s → J/ψη and B0 s → J/ψη decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in proton–proton collisions at a centre-of-mass energy of √s = 7 TeV.

Measurement of relative branching fractions of B decays to ψ(2S) and J/ψ mesons

The relative rates of B-meson decays into J/ψ and ψ(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions ( B) are measured to be where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ + μ −