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Posters

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2023-12-05
17:17
LHCb - The LHCb Scintillating Fibre Tracker
Reference: Poster-2023-1129
Note: dimitrios.kaminaris@cern.ch; lukas.witola@cern.ch
Created: 2023. -1 p

The LHCb detector underwent a major upgrade in the past years. The modifications enable the detector to operate at an increased instantaneous luminosity and to read out data at the LHC bunch crossing rate of 40MHz. The new operating conditions required the replacement of the complete tracking system. The main tracking stations are replaced by the SciFi Tracker, a large high granularity scintillating fibre tracker read out by arrays of silicon photomultipliers (SiPMs). A custom ASIC is used to digitise the SiPM signals at 40MHz using three comparators per channel. Further digital electronics perform clustering and data-compression before the data is sent via optical links to the DAQ system. The comparator thresholds are calibrated using a dedicated light injection system. The commissioning of this system, calibration results, and latest performance measurements are presented in this poster. The SciFi Tracker has three stations with four detection layers each and uses the BCAM system for real-time 3D monitoring. Originally developed for the ATLAS experiment, BCAM uses opto-electronic sensors to monitor the detector geometry detecting shifts or deformations caused by factors like LHCb magnet powering cycles, SciFi detector powering, or environmental variations. Preliminary results highlight BCAM's micron-level sensitivity (10-20 microns) and its effectiveness in monitoring the impact of magnetic fields and operational conditions on the detector alignment.

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LHCb poster - 13th LHC students poster session
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2023-12-05
14:11
LHCb - Search for the decay B^+_(c) -> mu^+ ν_mu gamma
Reference: Poster-2023-1128
Created: 2023. -1 p

The search for the decay B→µνɣ at LHCb using Run 2 data is reported. This channel is considered the golden mode to probe the B meson substructure and allows to probe the first inverse moment of the B-meson light-cone distribution amplitude. Reconstruction of this decay is very challenging at the LHC and deemed impossible. Using photon conversions to an e+e- pair in the vertex locator the reconstruction of the displaced B vertex is possible. This also allows to correct for the missing neutrino momentum and get a signal peak in corrected B invariant mass. The upcoming result has the potential to prove once again that LHCb can perform B physics analyses that were thought to be impossible at a hadron machine.

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LHCb poster - 13th LHC students poster session
© CERN Geneva

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2023-12-04
17:45
CERN in images - EN-FR
Reference: Poster-2023-1127
Created: 2023. -20 p
Creator(s): Landua, Fabienne

At CERN, we probe the fundamental structure of particles that make up everything around us. We do so using the world’s largest and most complex scientific instruments. This visual exhibition focuses mainly on photos, offers visitors the opportunity to explore CERN through 20 posters.

© CERN Geneva

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2023-12-04
16:25
LHCb Early Measurements with electrons in the final state using first Run 3 data
Reference: Poster-2023-1126
Created: 2023. -1 p

The LHCb Detector has undergone a series of major upgrades during the LHC LS2. In the first stages of data taking an Early Measurements Task Force is being carried out in order to understand the early detector performance and provide the first physics results of Run 3. In this poster we present the first results of the decays B+→J/ψK+ and B+→ψ(2S) K+, with the charmonia resonances decaying into a dielectron pair, using 2022 and 2023 data from the upgraded LHCb detector. This result represents a critical milestone towards future analysis involving electrons in the final state in Run 3, including Lepton Flavour Universality measurements

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LHCb poster - 13th LHC students poster session
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2023-12-01
16:32
LHCb - Charge-dependent curvature bias corrections using a pseudomass method
Reference: Poster-2023-1125
Created: 2023. -1 p

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.

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LHCb poster - 13th LHC students poster session
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2023-11-30
16:14
LHCb - Angular Analysis of the B^0_s -> phi (K^+K^-)e^+e^- decay in the low dielectron mass region at LHCb
Reference: Poster-2023-1124
Created: 2023. -1 p

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.

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LHCb poster - 13th LHC students poster session
© CERN Geneva

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2023-11-29
14:13
LHCb - New helium identification technique at LHCb
Reference: Poster-2023-1123
Created: 2023. -1 p

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.

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LHCb poster - 13th LHC students poster session
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2023-11-28
17:41
LHCb - Real-time alignment of the LHCb detector in Run 3
Reference: Poster-2023-1122
Created: 2023. -1 p

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.

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LHCb poster - 13th LHC students poster session
© CERN Geneva

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2023-11-28
17:35
LHCb - Commissioning of the Upstream Tracker for the LHCb Upgrade I
Reference: Poster-2023-1121
Created: 2023. -1 p

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.

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LHCb poster - 13th LHC students poster session
© CERN Geneva

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2023-11-28
17:29
LHCb - Using Hadronic Interactions to Assess the LHCb RF Box Deformation
Reference: Poster-2023-1120
Created: 2023. -1 p

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.

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LHCb poster - 13th LHC students poster session
© CERN Geneva

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