M1: Improving photon energy calibration in the LHCb electromagnetic calorimeter

The LHCb experiment is one of the four main experiments at the Large Hadron Collider at CERN, specialised in the measurement of “beauty” hadrons containing a b-quark. Decays of these hadrons may receive contributions from processes beyond the Standard Model of particle physics. These decays are therefore powerful probes for particles too heavy to be produced directly in existing colliders. 

Following a major detector upgrade, the LHCb experiment is currently collecting the “Run 3” dataset until mid-2026. This large dataset will allow measurements of beauty hadron decays with unprecedented precision, opening new sensitivity to physics beyond the Standard Model. The LAPP group has a particular interest in measurements of “radiative” beauty hadron decays involving a high-energy photon.  These decays are particularly sensitive to possible contributions from physics beyond the Standard Model, and can provide particular insight into fundamental questions such as the origin of large matter-antimatter asymmetry in the universe.

The analysis of decays involving a photon relies on excellent performance of the electromagnetic calorimeter (ECAL), for which the LAPP group plays a leading role in operation and calibration. Since the ECAL is calibrated using low-energy photons, non-linearities in the energy measurement translate into percent-level biases at high energies that vary across the detector plane. This effect directly reduces the achievable precision of key measurements using this dataset.

The goal of this project is to derive energy-scale correction factors to align the reconstructed invariant masses of radiative decays with their known values. Implementing these corrections will enhance the precision of all Run 3 measurements of radiative decays. If time permits, the project can extend to related topics according to the student’s interest, such as improving the robustness of photon identification classifiers against miscalibration for future LHCb data-taking periods.

This internship offers an excellent opportunity for a motivated student interested in experimental high-energy physics to make an important contribution to LHCb’s physics programme while developing valuable skills through hands-on experience and supervision from experts in data analysis and calorimetry. The LHCb collaboration consists of over a thousand scientists internationally, including across six institutes in France.

Essential: Experience with Python or C programming languages

Preferred: Experience with the ROOT framework for particle physics analysis

Informations:

Expérience: LHCb

Responsable de stage: Fionn BISHOP

Email: fionn.bishop@lapp.in2p3.fr