FastIC: a fast integrated circuit for the readout of high performance detectors

This work presents the 8-channel FastIC ASIC developed in CMOS 65 nm technology suitable for the readout of positive and negative polarity sensors in high energy physics experiments, Cherenkov detectors and time-of-flight systems. The front-end can be configured to perform analog summation of up to 4 single-ended channels before discrimination in view of improving time resolution when segmenting a SiPM. The outputs encode the time-of-arrival information and linear energy measurement which captures the peak amplitude of the input signal in the 5 µA–25 mA input peak current range. Power consumption of the ASIC is 12 mW/ch with default settings. Measurements of single photon time resolution with a red-light laser source and a HPK SiPM S13360-3050CS are ≈140 ps FWHM

Search for CP violation in Xi(+)(c) -> pK(-) pi(+) decays using model-independent techniques

A first search for CP violation in the Cabibbo-suppressed Ξ+c→pK−π+ decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are based on a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0fb−1, and collected by the LHCb experiment at centre-of-mass energies of 7 and 8TeV. The data are consistent with the hypothesis of no CP violation

Search for the doubly charmed baryon Xi(+)(cc)

A search for the doubly charmed baryon Ξ+cc is performed through its decay to the Λ+cK−π+ final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb−1. No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c2. Upper limits are set at 95% credibility level on the ratio of the Ξ+cc production cross-section times the branching fraction to that of Λ+c and Ξ++cc baryons. The limits are determined as functions of the Ξ+cc mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c

Observation of New Resonances in the Λb0 π+π- System

We report the observation of a new structure in the Λ0 bπþπ− spectrum using the full LHCb data set of pp collisions, corresponding to an integrated luminosity of 9 fb−1, collected at ffiffi s p ¼ 7, 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be mΛbð6146Þ0 ¼ 6146.17 0.33 0.22 0.16 MeV; mΛbð6152Þ0 ¼ 6152.51 0.26 0.22 0.16 MeV; ΓΛbð6146Þ0 ¼ 2.9 1.3 0.3 MeV; ΓΛbð6152Þ0 ¼ 2.1 0.8 0.3 MeV;with a mass splitting of Δm ¼ 6.34 0.32 0.02 MeV, where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ0 b baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λbð1DÞ0 states

HRFlexToT: A High Dynamic Range ASIC for Time-of-Flight Positron Emission Tomography

Abstract: Time-of-Flight positron emission tomography scanners demand fast and efficient photo sensors and scintillators coupled to fast readout electronics. This article presents the high resolution flexible Time-over-Threshold (HRFlexToT), a 16-channel application-specific-integrated circuit for silicon photomultipliers (SiPM) anode readout manufactured using XFAB 0.18- μm CMOS technology. The main features of the HRFlexToT are a linear Time-over-Threshold with an extended dynamic range (10 bits) for energy measurement, low power consumption (≈ 3.5 mW/ch), and an excellent timing response. The experimental measurements show an energy linearity error of ≈ 3% and an energy resolution of about 12% at 511 keV. Single-photon time resolution measurements performed using an Fondazione Bruno Kessler (FBK) SiPM NUV-HD ( 4×4 mm2 pixel, 40- μm cell) and a Hamamatsu SiPM S13360-3050CS are around 142 and 167 ps full width at half maximum (FWHM), respectively. Coincidence time resolution (CTR) measurements with small cross-section pixelated crystals (LSO:Ce,Ca 0.4%, 2×2×5 mm3) coupled to the same Hamamatsu S13360-3050CS and FBK NUV-HD sensors yield a CTR of 117 ps and 119 ps, respectively. Measurements performed with a large cross-section monolithic crystal (LFS crystal measuring 25×25×20 mm3) and a Hamamatsu SiPM array S13361-6050NE-04 show a CTR of 324 ps FWHM after time-walk and time-skew correction

Updated measurement of decay-time-dependent CP asymmetries in D-0 -> K+ K- and D-0 -> pi(+)pi(-) decays

A search for decay-time-dependent charge-parity (CP) asymmetry in D0→K+K− and D0→π+π− decays is performed at the LHCb experiment using proton-proton collision data recorded at a center-of-mass energy of 13 TeV, and corresponding to an integrated luminosity of 5.4  fb−1. The D0 mesons are required to originate from semileptonic decays of b hadrons, such that the charge of the muon identifies the flavor of the neutral D meson at production. The asymmetries in the effective decay widths of D0 and ¯D0 mesons are determined to be AΓ(K+K−)=(−4.3±3.6±0.5)×10−4 and AΓ(π+π−)=(2.2±7.0±0.8)×10−4, where the uncertainties are statistical and systematic, respectively. The results are consistent with CP symmetry and, when combined with previous LHCb results, yield AΓ(K+K−)=(−4.4±2.3±0.6)×10−4 and AΓ(π+π−)=(2.5±4.3±0.7)×10−4

Measurement of the Bc-meson production fraction and asymmetry in 7 and 13 TeV pp collisions

The production fraction of the Bc-meson with respect to the sum of B- A nd B0 mesons is measured in both 7 and 13 TeV center-of-mass (c.m.) energy pp collisions produced by the Large Hadron Collider (LHC), using the LHCb detector. The rate, approximately 3.7 per mille, does not change with energy, but shows a transverse momentum dependence. The Bc-Bc+ production asymmetry is also measured and is consistent with zero within the determined statistical and systematic uncertainties of a few percent

Search for the lepton flavour violating decay B + → K + μ − τ + using Bs2∗0 decays

A search is presented for the lepton flavour violating decay B+ → K+μ−τ+ using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1. The τ leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the τ lepton is determined by using B+ mesons from B∗0s2→B+K− decays. No significant excess is observed, and an upper limit is set on the branching fractio

Search for the Rare Decays B-s(0) -> e(+) e(-) and B-0 -> e(+) e(-)

A search for the decays B0s→e+e− and B0→e+e− is performed using data collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 2  fb−1, respectively. No signal is observed. Assuming no contribution from B0→e+e− decays, an upper limit on the branching fraction B(B0s→e+e−)<9.4(11.2)×10−9 is obtained at 90(95)% confidence level. If no B0s→e+e− contribution is assumed, a limit of B(B0→e+e−)<2.5(3.0)×10−9 is determined at 90(95)% confidence level. These upper limits are more than one order of magnitude lower than the previous values

Measurement of CP observables in B ± → DK ± and B ± → Dπ ± with D → KS0K±π∓ decays

Measurements of CP observables in B± → DK± and B± → Dπ± decays are presented, where D represents a superposition of D0 and D¯¯¯¯0 states. The D meson is reconstructed in the three-body final states K0SK±π∓ and K0SK∓π±. The analysis uses samples of B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb−1 collected with the LHCb detector at centre-of-mass energies of s√ = 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle γ