Disseny microelectrnic de circuits discriminadors de polsos pel detector LHCb

The aim of this thesis is to present a solution for implementing the front end system of the Scintillator Pad Detector (SPD) of the calorimeter system of the LHCb experiment that will start in 2008 at the Large Hadron Collider (LHC) at CERN. The requirements of this specific system are discussed and an integrated solution is presented, both at system and circuit level. We also report some methodological achievements. In first place, a method to study the PSRR (and any transfer function) in fully differential circuits taking into account the effect of parameter mismatch is proposed. Concerning noise analysis, a method to study time variant circuits in the frequency domain is presented and justified. This would open the possibility to study the effect of 1/f noise in time variants circuits. In addition, it will be shown that the architecture developed for this system is a general solution for front ends in high luminosity experiments that must be operated with no dead time and must be robust against ballistic deficit

Direct photon production at LHCb

At small Bjorken-x, the large gluon number density in the nucleon leads to gluon recombination competing with gluon splitting, which could result in saturation of the gluon PDF. This gluon saturation has yet to be conclusively observed. Direct photon production provides sensitivity to gluon densities in protons and nuclei, and the forward acceptance of LHCb detector allows for measurements of this process at low Bjorken-x, providing an ideal probe of saturation effects. Progress towards the measurement of forward direct photon production using the LHCb detector is presented

Characterisation of the MUSIC ASIC for large-area silicon photomultipliers for gamma-ray astronomy

Large-area silicon photomultipliers (SiPMs) are desired in many applications where large surfaces have to be covered. For instance, a large area SiPM has been developed by Hamamatsu Photonics in collaboration with the University of Geneva, to equip gamma-ray cameras employed in imaging atmospheric Cherenkov telescopes. The sensor being about 1 cm2, a suitable preamplification electronics has been investigated in this work, which can deal with long pulses induced by the large capacitance of the sensor. The so-called Multiple Use SiPM Integrated Circuit (MUSIC), developed by the ICCUB (University of Barcelona), is investigated as a potential front-end ASIC, suitable to cover large area photodetection planes of gamma-ray telescopes. The ASIC offers an interesting pole-zero cancellation (PZC) that allows dealing with long SiPM signals, the feature of active summation of up to 8 input channels into a single differential output and it can offer a solution for reducing power consumption compared to discrete solutions. Measurements and simulations of MUSIC coupled to two SiPMs developed by Hamamatsu are considered and the ASIC response is characterized.Postprint (published version

Strong constraints on the b → sγ photon polarisation from B 0 → K *0 e + e − decays

An angular analysis of the B0 → K∗0 e +e − decay is performed using a data sample corresponding to an integrated luminosity of 9 fb−1 of pp collisions collected with the LHCb experiment. The analysis is conducted in the very low dielectron mass squared (q 2 ) interval between 0.0008 and 0.257 GeV2 , where the rate is dominated by the B0 → K∗0γ transition with a virtual photon. The fraction of longitudinal polarisation of the K∗0 meson, FL, is measured to be FL = (4.4 ± 2.6 ± 1.4)%, where the first uncertainty is statistical and the second systematic. The ARe T observable, which is related to the lepton forward-backward asymmetry, is measured to be ARe T = −0.06 ± 0.08 ± 0.02. The A (2) T and AIm T transverse asymmetries, which are sensitive to the virtual photon polarisation, are found to be A (2) T = 0.11 ± 0.10 ± 0.02 and AIm T = 0.02 ± 0.10 ± 0.01. The results are consistent with Standard Model predictions and provide the world's best constraint on the b → sγ photon polarisation

Constraints on the unitarity triangle angle γ from Dalitz plot analysis of B0 →dK+π- decays

The first study is presented of CP violation with an amplitude analysis of the Dalitz plot of $B^0 \to D K^+ \pi^-$ decays, with $D \to K^+ \pi^-$, $K^+ K^-$ and $\pi^+ \pi^-$. The analysis is based on a data sample corresponding to $3.0\,{\rm fb}^{-1}$ of $pp$ collisions collected with the LHCb detector. No significant CP violation effect is seen, and constraints are placed on the angle $\gamma$ of the unitarity triangle formed from elements of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Hadronic parameters associated with the $B^0 \to D K^*(892)^0$ decay are determined for the first time. These measurements can be used to improve the sensitivity to $\gamma$ of existing and future studies of the $B^0 \to D K^*(892)^0$ decay

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

Matrix: a 15 ps resistive interpolation TDC ASIC based on a novel regular structure

This paper presents a 4-channel TDC ASIC with the following features: 15-ps LSB (9.34 ps after calibration), 10-ps jitter, < 4-ps time resolution, up to 10 MHz of sustained input rate per channel, 45 mW of power consumption and very low area (910×215 μm2) in a commercial 180 nm technology. The main contribution of this work is the novel design of the clock interpolation circuitry based on a resistive interpolation mesh circuit (patented), a two-dimensional regular structure with very good properties in terms of power consumption, area and low process variability

Model-independent evidence for J /ψp contributions to Λb0 →j /ψpK- decays

The data sample of Λ0b→J/ψpK− decays acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3  fb−1, is inspected for the presence of J/ψp or J/ψK− contributions with minimal assumptions about K−p contributions. It is demonstrated at more than nine standard deviations that Λ0b→J/ψpK− decays cannot be described with K−p contributions alone, and that J/ψp contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for P+c→J/ψp charmonium-pentaquark states in the same data sample

First observation of D0-D-0 oscillations in D0 →k+π-π+π- decays and measurement of the associated coherence parameters

Charm meson oscillations are observed in a time-dependent analysis of the ratio of D0→K+π−π+π− to D0→K−π+π−π+ decay rates, using data corresponding to an integrated luminosity of 3.0  fb−1 recorded by the LHCb experiment. The measurements presented are sensitive to the phase-space averaged ratio of doubly Cabibbo-suppressed to Cabibbo-favored amplitudes rK3πD and the product of the coherence factor RK3πD and a charm mixing parameter y′K3π. The constraints measured are rK3πD=(5.67±0.12)×10−2, which is the most precise determination to date, and RK3πDy′K3π=(0.3±1.8)×10−3, which provides useful input for determinations of the CP-violating phase γ in B±→DK±, D→K∓π±π∓π± decays. The analysis also gives the most precise measurement of the D0→K+π−π+π− branching fraction, and the first observation of D0-¯D0 oscillations in this decay mode, with a significance of 8.2 standard deviations

Angular analysis and differential branching fraction of the decay B {/s 0} → ϕμ + μ -

An angular analysis and a measurement of the differential branching fraction of the decay B0 s → φµ+µ − are presented, using data corresponding to an integrated luminosity of 3.0 fb−1 of pp collisions recorded by the LHCb experiment at √ s = 7 and 8 TeV. Measurements are reported as a function of q 2 , the square of the dimuon invariant mass and results of the angular analysis are found to be consistent with the Standard Model. In the range 1 < q2 < 6 GeV2/c4 , where precise theoretical calculations are available, the differential branching fraction is found to be more than 3 σ below the Standard Model predictions