Low noise front end ICECAL ASIC for the upgrade of the LHCb calorimeter

A fully differential ASIC with cooled input termination is presented as a solution for the Upgrade of the Calorimeter front end electronics. The LHCb experiment needs to increase about ten times the integrated luminosity in order to study new physics. The increase in signal has to be compensated reducing the gain of the photomultipliers which implies stringent noise requirements. The proposed solution offers an active termination at the input and avoids the noise originated by the use of a resistor. The circuit is based on a two interleaved channel with a first amplifier stage, a switched integrator, and a Track-and-Hold. Two prototypes have been implemented and tested in SiGe BiCMOS 0.35um technology

Measurement of the mass and lifetime of the Ωb- baryon

A proton-proton collision data sample, corresponding to an integrated luminosity of 3 fb−1 collected by LHCb at s√=7 and 8 TeV, is used to reconstruct 63±9 Ω−b→Ω0cπ−, Ω0c→pK−K−π+ decays. Using the Ξ−b→Ξ0cπ−, Ξ0c→pK−K−π+ decay mode for calibration, the lifetime ratio and absolute lifetime of the Ω−b baryon are measured to be τΩ−bτΞ−bτΩ−b=1.11±0.16±0.03,=1.78±0.26±0.05±0.06 ps, where the uncertainties are statistical, systematic and from the calibration mode (for τΩ−b only). A measurement is also made of the mass difference, mΩ−b−mΞ−b, and the corresponding Ω−b mass, which yields mΩ−b−mΞ−bmΩ−b=247.4±3.2±0.5 MeV/c2,=6045.1±3.2±0.5±0.6 MeV/c2. These results are consistent with previous measurements

Precision measurement of the B0 s –B 0 s oscillation frequency with the decay B0 s → D − s π +

A key ingredient to searches for physics beyond the Standard Model in B0 s mixing phenomena is the measurement of the B0 s – B 0 s oscillation frequency, which is equivalent to the mass difference 1ms of the B0 s mass eigenstates. Using the world’s largest B0 s meson sample accumulated in a dataset, corresponding to an integrated luminosity of 1.0 fb−1 , collected by the LHCb experiment at the CERN LHC in 2011, a measurement of 1ms is presented. A total of about 34 000 B0 s → D − s π + signal decays are reconstructed, with an average decay time resolution of 44 fs. The oscillation frequency is measured to be 1ms = 17.768 ± 0.023 (stat) ± 0.006 (syst) ps−1 , which is the most precise measurement to date

Implications of LHCb measurements and future prospects

During 2011 the LHCb experiment at CERN collected 1.0 fb−1 of s√=7~TeV pp collisions. Due to the large heavy quark production cross-sections, these data provide unprecedented samples of heavy flavoured hadrons. The first results from LHCb have made a significant impact on the flavour physics landscape and have definitively proved the concept of a dedicated experiment in the forward region at a hadron collider. This document discusses the implications of these first measurements on classes of extensions to the Standard Model, bearing in mind the interplay with the results of searches for on-shell production of new particles at ATLAS and CMS. The physics potential of an upgrade to the LHCb detector, which would allow an order of magnitude more data to be collected, is emphasised

Measurement of J/ψ polarization in pp collisions at s√=7 TeV

An angular analysis of the decay J/ψ→μ + μ − is performed to measure the polarization of prompt J/ψ mesons produced in pp collisions at s√=7 TeV. The dataset corresponds to an integrated luminosity of 0.37 fb−1 collected with the LHCb detector. The measurement is presented as a function of transverse momentum, p T, and rapidity, y, of the J/ψ meson, in the kinematic region 2<p T<15 GeV/c and 2.0<y<4.5

Measurement of the effective B0s→J/ψK0S lifetime

This paper reports the first measurement of the effective B0s→J/ψK0S lifetime and an updated mea-surement of its time-integrated branching fraction. Both measurements are performed with a data sample, corresponding to an integrated luminosity of 1.0 fb−1 of pp collisions, recorded by the LHCb experimentin 2011 at a centre-of-mass energy of 7 TeV. The results are:τeff J/ψK0S=1.75±0.12(stat)±0.07(syst)ps and B(B0s→J/ψK0S)=(1.97±0.23)×10−5. For the latter measurement, the uncertainty includes bothstatistical and systematic sources

Observations of B0 s → ψ(2S)η and B0 (s) → ψ(2S)π+π− decays

First observations of the B0s→ψ(2S)η,B0→ψ(2S)π+π− and B0s→ψ(2S)π+π− decays are made 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. The ratios of the branching fractionsof each of the ψ(2S) modes with respect to the corresponding J/ψ decays are B(B0s→ψ(2S)η)B(B0s→J/ψη)=0.83±0.14(stat)±0.12(syst)±0.02(B),B(B0→ψ(2S)π+π−)B(B0→J/ψπ+π−)=0.56±0.07(stat)±0.05(syst)±0.01(B),B(B0s→ψ(2S)π+π−)B(B0s→J/ψπ+π−)=0.34±0.04(stat)±0.03(syst)±0.01(B), where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψandψ(2S) meson decays

Time alignment of the front end electronics of the LHCb calorimeters

LHCb is the experiment at the Large Hadron Collider at CERN designed for performing studies of CP-symmetry violation and rare decays of B-hadrons. Its calorimeter system allows to trigger on photons and electrons by associating the information from a scintillating pad signing charged particle (SPD), a pre-shower tagging electromagnetic particles (PS), an electromagnetic calorimeter (ECAL) and a hadronic calorimeter (HCAL). We present the principles and procedures for the fine time-alignment throughout the commissioning and the first collision phases. We give a particular emphasis to the choices made in the electronic design of the calorimeters to deal with the signal shape and spill over. Also we summarise the achieved levels of synchronisation

Measurement of the B0–B0 oscillation frequency md with the decays B0→D−π+ and B0→J/ψK∗0

The B0–B0oscillation frequency mdis measured by the LHCb experiment using a dataset correspondingto an integrated luminosity of 1.0fb−1of proton–proton collisions at√s=7TeV,and is found to be md=0.5156±0.0051(stat.)±0.0033(syst.)ps−1. The measurement is based on results from analyses of the decays B0→D−π+(D−→K+π−π−) and B0→J/ψK∗0(J/ψ→μ+μ−,K∗0→K+π−) and their charge conjugated modes

Evidence for the decay B0 → J/ψω and measurementof 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 B0s→J/ψη and B0s→J/ψη′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experimentin proton–proton collisions at a centre-of-mass energy of√s=7 TeV. The branching fractions of these decays are measured relative to that of the B0→J/ψρ0 decay: B(B0→J/ψω)B(B0→J/ψρ0)=0.89±0.19(stat)+0.07−0.13(syst),B(B0s→J/ψη)B(B0→J/ψρ0)=14.0±1.2(stat)+1.1−1.5(syst)+1.1−1.0(fdfs),B(B0s→J/ψη′)B(B0→J/ψρ0)=12.7±1.1(stat)+0.5−1.3(syst)+1.0−0.9(fdfs),where the last uncertainty is due to the knowledge of fd/fs, the ratio of b-quark hadronization factors thataccounts for the different production rate of B0 and B0s mesons. The ratio of the branching fractions of B0s→J/ψη′ and B0s→J/ψη decays is measured to be B(B0s→J/ψη′)B(B0s→J/ψη)=0.90±0.09(stat)+0.06−0.02(syst)