CERN Accelerating science

ATLAS Note
Report number	ATL-DAQ-PROC-2010-041
Title	Development and Online Operation of Minimum Bias Triggers in ATLAS
Author(s)	Martin, T A D (Birmingham U.)
Collaboration	On behalf of the ATLAS collaboration
Publication	2010
Imprint	01 Nov 2010
Number of pages	6
In:	JINST 5 (2010) C12051
In:	Topical Workshop on Electronics for Particle Physics 2010, Aachen, Germany, 20 - 24 Sep 2010, pp.C12051
DOI	10.1088/1748-0221/5/12/C12051
Subject category	Detectors and Experimental Techniques
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	Minimum Bias ; Trigger ; MBTS
Abstract	Since the restart of the LHC in November 2009, ATLAS has recorded inelastic $p - p$ collisions to perform first measurements on charged particle multiplicities. These measurements will help to constrain various phenomenological models describing soft parton interactions. Understanding trigger efficiencies for different event types is therefore crucial to minimize any possible bias in the event selection. ATLAS uses two main minimum bias triggers, utilizing complementary detector components and trigger levels. A hardware based first trigger level situated in the forward regions of $2.1 < |eta| < 3.8$ has been proven to select $p - p$ collisions with high efficiency. A complementary Inner Detector based minimum bias trigger uses a random seed on filled bunches and central tracking detectors for event selection. Both triggers were essential for the analysis of kinematic spectra of charged particles. Their performance and trigger efficiency measurements as well as studies on possible bias sources will be presented.
Copyright/License	Publication: (License: CC-BY-3.0)

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