The ALICE electromagnetic calorimeter high level triggers

TL;DR

This paper discusses the development and implementation of the high-level trigger system for the ALICE electromagnetic calorimeter, enhancing real-time data filtering and jet measurement capabilities during LHC operations.

Contribution

It introduces a new online reconstruction and trigger chain within the HLT framework specifically for the EMCal detector, improving trigger sharpening and data reduction.

Findings

Successful commissioning during 2011 LHC run

Enhanced jet reconstruction capabilities

Improved trigger efficiency and data filtering

Abstract

The ALICE (A Large Ion Collider Experiment) detector yields a huge sample of data from different sub-detectors. On-line data processing is applied to select and reduce the volume of the stored data. ALICE applies a multi-level hardware trigger scheme where fast detectors are used to feed a three-level (L0, L1, and L2) deep chain. The High-Level Trigger (HLT) is a fourth filtering stage sitting logically between the L2 trigger and the data acquisition event building. The EMCal detector comprises a large area electromagnetic calorimeter that extends the momentum measurement of photons and neutral mesons up to $p_T=250$ GeV/c, which improves the ALICE capability to perform jet reconstruction with measurement of the neutral energy component of jets. An online reconstruction and trigger chain has been developed within the HLT framework to sharpen the EMCal hardware triggers, by combining the central barrel tracking information with the shower reconstruction (clusters) in the calorimeter. In the present report the status and the functionality of the software components developed for the EMCal HLT online reconstruction and trigger chain will be discussed, as well as preliminary results from their commissioning performed during the 2011 LHC running period.