119224346
Using final state pseudorapidities to improve s-channel resonance observables at the LHC
We study the use of final state particle pseudorapidity for measurements of s-channel resonances at the LHC. Distinguishing the spin of an s-channel resonance can, in principle, be accomplished using angular distributions in the center-of-mass frame, possibly using a center-edge asymmetry measurement, A{sub CE}. In addition, forward-backward asymmetry measurements, A{sub FB}, can be used to distinguish between models of extra neutral gauge bosons. In this article we show how these measurements can be improved by using simple methods based on the pseudorapidity of the final state particles and present the expected results for A{sub FB} and A{sub CE} for several representative models.
19324611
Identification of extra neutral gauge bosons at the LHC using b and t quarks.
New neutral gauge bosons (Z' 's) are predicted by many models of physics beyond the standard electroweak theory. It is possible that a Z' will be discovered by the Large Hadron Collider program. The next step would be to measure its properties to identify the underlying theory that gave rise to the Z'. Heavy quarks have the unique property that they can be identified in the final states. In this Letter we demonstrate that measuring Z' decays to b- and t-quark final states can act as an effective means of discriminating between models with extra gauge bosons.
123039432
Development and online operation of minimum bias triggers in ATLAS
Since the restart of the LHC in November 2009, ATLAS has recorded pp collisions to investigate new phenomena at the high energy frontier. One early measurement is of charged particle multiplicities in inelastic interactions, which was performed on data sets of about 360,000 and 10,000,000 minimum bias event at (s)1/2 = 900 GeV and 7 TeV respectively. This measurements will help to constrain various phenomenological models describing inelastic interactions. Understanding trigger efficiencies for different event types is crucial to minimize any possible bias in the event selection. ATLAS has a three level trigger system and utilises two main minimum bias triggers. A primary scintillator based trigger situated in the forward regions of 2.1 < |η| < 3.8 was proven to select pp collisions with high efficiency. A complementary control trigger runs on unbiased filled proton bunches and utilizes space points reconstructed in the silicon tracking volume to trigger on inelastic interactions. Both triggers were essential for the analysis of charged particle multiplicities. Their performance and trigger efficiency measurements as well as studies on possible bias sources are presented. The triggers are shown to form an effective and inclusive triggering solution for early LHC physics.