LHCb

Abstract:

The ratio between the branching fractions of the B0 → ρ(770)0γ and B0 → K*(892)0γ decays is measured with proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The measured value isBB0→ρ7700γBB0→K∗8920γ=0.0189±0.0007±0.0005, where the first uncertainty is statistical and the second systematic. The branching fraction for B0→ ρ(770)0γ decays is hence obtained asBB0→ρ7700γ=7.9±0.3±0.2±0.2×10−7, where the last uncertainty is due to the branching fraction of the normalisation mode. This result assumes that both the ρ(770)0 and K*(892)0 decays saturate the dihadron mass spectra considered in the analysis. It is consistent with the current world-average value and by far the most precise measurement to date.

Abstract:

A study of charm mixing and CP violation in D0 → K±π∓π±π∓ decays is performed using data collected by the LHCb experiment in proton-proton collisions from 2015 to 2018, corresponding to an integrated luminosity of 6 fb−1. The ratio of promptly produced D0 → K+π−π+π− to D0 → K−π+π−π+ decay rates is measured as a function of D0 decay time, both inclusive over phase space and in bins of phase space. Taking external inputs for the D0−D¯0 mixing parameters x and y allows constraints to be obtained on the hadronic parameters of the charm decay. When combined with previous measurements from charm-threshold experiments and at LHCb, improved knowledge is obtained for these parameters, which is valuable for studies of the angle γ of the Unitarity Triangle. An alternative analysis is also performed, in which external inputs are taken for the hadronic parameters, and the mixing parameters are determined, including ∆x and ∆y, which are nonzero in the presence of CP violation. It is found that x=0.85−0.24+0.15%, y=0.21−0.27+0.29%, ∆x = (−0.02 ± 0.04) % and Δy=0.02−0.03+0.04%. These results are consistent with previous measurements and the hypothesis of CP conservation.

Abstract:

We present a Monte Carlo-based simulation stack that provides time-of-flight (ToF)-resolved blood flow index (BFi) and has been validated against continuous-wave (CW) and time-resolved BFi measurements in both tissue-mimicking phantoms and in-vivo. Using this simulation, we evaluated the influence of key parameters including source-detector separation, ToF selection, and minimum resolvable lag on brain sensitivity by comparing simulated pulsatile blood flow signals from scalp and brain layers. We used these results to optimise the design of CoMind Research One (R1), a 16-channel interferometric time-of-flight-resolved optical neuromonitoring system that operates in real time and enables high-fidelity measurements of field autocorrelation at times-of-flight exceeding 1 ns. We validated this system and demonstrated its depth sensitivity using homogeneous and bi-layer dynamic tissue-mimicking phantoms. The advancements in optical throughput, depth selectivity, and robustness demonstrated by CoMind R1 pave the way for clinical translation and broader adoption of non-invasive optical measurements of cerebral blood flow.

Abstract:

The spatial and temporal performance of a telescope system comprising planar silicon sensors bump-bonded to Timepix4-v2 ASICs are assessed at the CERN SPS using a 180 GeV/c mixed hadron beam. The pointing resolution at the centre of the telescope is 2.3 ± 0.1 μm and 2.4 ± 0.1 μm in x and y directions, respectively. The temporal resolution for the combined timestamps on a track using only the information from the Timepix4 planes is found to be 92 ± 5 ps. The telescope is extensively described including its data acquisition system and dedicated software as well as the corrections applied to the raw measurements.