Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of the tracking detectors. The curvature biases present at the LHCb detector are studied in $pp$ collision data recorded at $\sqrt{s}=13$~TeV from 2016 to 2018. The biases are determined using the pseudomass method with $Z\to\mu^+\mu^-$ decays in intervals defined by the data-taking period, magnet polarity and muon direction in the detector. Correcting for these biases, typically at the $10^{-4}$~GeV$^{-1}$ level, improves the $Z\to\mu^+\mu^-$ mass resolution by roughly 20\% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass.

One of the privileged ways to search for signs of New Physics (NP) beyond the Standard Model (SM), is the study of b\\rightarrow s\\ell^{+}\\ell^{-}b→sℓ+ℓ− (\\ellℓ\= electron or muon) transitions which involve Flavour Changing Neutral Currents (FCNC) via box or loop diagrams. The aim of this work is to perform an angular analysis on B\_s^0 \\rightarrow \\phi e^+e^-Bs0→ϕe+e− in the low dielectron mass region to provide the measurement of the photon polarization in b -> s gamma transitions.

The identification of helium nuclei at LHCb is achieved using a method primarily based on measurements of ionisation losses in the silicon sensors. It is developed using pp collision data at √s = 13 TeV recorded by the LHCb experiment in the years 2016 to 2018, corresponding to an integrated luminosity of 5.5/fb. A total of around $10^5$ helium and antihelium candidates are identified with negligible background contamination. The helium identification efficiency is estimated to be approximately 50% with a corresponding background misidentification probability of down to O(10−12). The method is validated with the observation of 107±11 hypertritons and antihypertritons, which are reconstructed via their two-body decay 3ΛH ⭢ 3He + π- and its charge conjugate. These observations open the door to a rich programme of precise measurements of QCD and astrophysics interest to be performed on the available data.

In order to increase the event rate and operate at a larger instantaneous luminosity, the LHCb detector has undergone a big upgrade for the new data-taking period in Run 3. An important part of the upgrade is the improvement of the trigger system, which is now fully software-based, and performs an offline-quality track reconstruction. A precise knowledge of the position and orientation of all LHCb sub-detectors in real-time is crucial to maximize the trigger efficiency and obtain the best-quality data for physics analyses. This poster summarizes the foreseen real-time alignment and calibration procedure, with a focus on the alignment of the LHCb tracker, which has a large impact on the reconstructed track \chi^2, affecting the number of tracks that can be reconstructed as well as the primary and secondary vertex resolution and the track momentum resolution. These are all quantities employed by most of the trigger lines for the selection of events. Results from the Run 3 commissioning period are presented, showing the impact of the VELO and SciFi alignment on the vertex and track resolution. The improvements seen on the reconstructed mass distributions of \K^{0}_s and \Lambda^0 hadrons between two different stages of the LHCb alignment are also shown as an example.

The LHCb experiment has been recently upgraded in most of all its subdetector, including the Upstream Tracker. The installation of the four planes of silicon microstrip was concluded in the beginning of 2023 and now the detector is under the commissioning phase. In this poster, the integration process of the Upstream Tracker in the global data taking of the LHCb is described, focusing on the data acquisition firmware, the decoding algorithm and control and data analysis software. Details on the latest progresses and on the detector performance will be given, including operational conditions, detector performance tests and the first data captured with the dedicated firmware.

At the start of 2023, a vacuum control incident resulted in damage to the thin aluminium box that separates the secondary vacuum of the LHCb experiment from the primary vacuum of the LHC, resulting in major disruption to LHCb data-taking. A detailed study of the resulting deformation of the box is presented, by reconstructing hadronic interactions in the material of the box. The deformations across both sides is found to be between 32-34mm, such that the normal procedure by which the two halves of the Vertex Locator (VELO) are opened during LHC beam injection and closed during data taking became impossible.

Monte Carlo event generators (MCEGs) play a crucial role in understanding the physics of particle colliders. They serve as essential components for experimental analyses and are extensively used by both theorists and experimentalists to make predictions and prepare for future experiments. MCEGs incorporate free parameters, primarily associated with soft and non- perturbative physics modeling, the values of which calibrated through the process of tuning. This process is based on two independent libraries, RIVET and PROFESSOR, within the LbMCSubmit framework, specifically for the purpose of tuning various parameters in PYTHIA 8.204, including cross- sections, color- reconnection, flavor composition, and multiparton interactions. The methodology, benefits, and implications of this approach are comprehensively discussed, highlighting the effective utilization of these tools for advancing Monte Carlo event generator capabilities through accurate parameter tuning.

The two LHCb Ring Imaging Cherenkov detectors, providing charged hadron discrimination, underwent a major upgrade to withstand with the five-fold increase in the instantaneous luminosity delivered to the experiment in Run 3. The opto-electronics chain has been completely changed by employing approximately 3100 Multianode Photomultiplier Tubes and a brand-new frontend electronics. The number of detected Cherenkov photons per track is one of the crucial parameters driving the charged hadron identification performance and therefore the sensitivity to single photons at rates up to 100 MHz/cm2 is of paramount importance. In order to uniformy the response of the detectors and to maximise the efficiency, the calibration data acquired in the experiment has been used to equalise the single photon gain over approximately 200k channels by keeping at the same time the backgrounds under control. The data-taking procedures, data analysis techniques and the results of the calibration are presented.

The LHCb experiment underwent a major upgrade to run with a five-fold increase in the instantaneous luminosity. All the subdetectors now employ a triggerless readout, while the trigger architecture has been changed to cope with larger input rates. The operations of the upgraded LHCb detector started in 2022 and the data collected by the experiment have been used to determine the first global performance figure of merit. In particular, the charged hadron identification performance, provided in LHCb by two Ring Imaging Cherenkov detectors and taking as input the tracking information, has been evaluated by using the dataset collected in 2022 and 2023. The performance is determined by using dedicated calibration streams and the procedure is therefore also providing a validation of the new LHCb Run 3 dataflow model. The early hadron identification performance achieved in Run 3 is presented.

Ratios of branching fractions constitute a powerful test of lepton flavour universality (LFU), since they have accurate Standard Model (SM) predictions and could be sensitive to New Physics processes that violate LFU. A significant tension remains between the SM theoretical values and the experimental measurements performed by LHCb and other experiments. In this poster, the status of the analysis aiming at the simultaneous measurement of the ratios R(D(*)0)= BR(B->D(*)0 Tau Nu)/BR(B->D(*)0 Mu Nu), where D(*)0 is either D0 or D*0 meson, is presented, with the tau lepton reconstructed by using 3-prong hadronic decays.