ReDecay: A novel approach to speed up the simulation at LHCb

TL;DR

ReDecay introduces a method to significantly accelerate LHCb detector simulations by reusing parts of previously simulated events, maintaining accuracy while reducing computational time by an order of magnitude.

Contribution

The paper presents a novel re-usage technique in simulation software that drastically speeds up event simulation without compromising quality.

Findings

Achieves approximately tenfold increase in simulation speed.

Maintains the same simulation quality as traditional methods.

Reduces computational resources needed for large-scale data samples.

Abstract

With the steady increase in the precision of flavour physics measurements collected during LHC Run 2, the LHCb experiment requires simulated data samples of larger and larger sizes to study the detector response in detail. The simulation of the detector response is the main contribution to the time needed to simulate full events. This time scales linearly with the particle multiplicity. Of the dozens of particles present in the simulation only the few participating in the signal decay under study are of interest, while all remaining particles mainly affect the resolutions and efficiencies of the detector. This paper presents a novel development for the LHCb simulation software which re-uses the rest of the event from previously simulated events. This approach achieves an order of magnitude increase in speed and the same quality compared to the nominal simulation.