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SoftKiller, a particle-level pileup removal method.

Cacciari M, Salam GP, Soyez G - Eur Phys J C Part Fields (2015)

Bottom Line: It removes the softest particles in an event, up to a transverse momentum threshold that is determined dynamically on an event-by-event basis.In simulations, this simple procedure appears to be reasonably robust and brings superior jet resolution performance compared to existing jet-based approaches.It is also nearly two orders of magnitude faster than methods based on jet areas.

View Article: PubMed Central - PubMed

Affiliation: Université Paris Diderot, Paris, France ; Sorbonne Universités, UPMC Univ Paris 06, UMR 7589, LPTHE, 75005 Paris, France ; CNRS, UMR 7589, LPTHE, 75005 Paris, France.

ABSTRACT

Existing widely used pileup removal approaches correct the momenta of individual jets. In this article we introduce an event-level, particle-based pileup correction procedure, SoftKiller. It removes the softest particles in an event, up to a transverse momentum threshold that is determined dynamically on an event-by-event basis. In simulations, this simple procedure appears to be reasonably robust and brings superior jet resolution performance compared to existing jet-based approaches. It is also nearly two orders of magnitude faster than methods based on jet areas.

No MeSH data available.


Illustration of the SoftKiller method. The left plot depicts particles in an event, with the hard-event particles shown in blue and the pileup particles shown in red. On the right, the same event after applying the SoftKiller. The vertical dotted lines represent the edges of the patches used to estimate the pileup density
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Fig1: Illustration of the SoftKiller method. The left plot depicts particles in an event, with the hard-event particles shown in blue and the pileup particles shown in red. On the right, the same event after applying the SoftKiller. The vertical dotted lines represent the edges of the patches used to estimate the pileup density

Mentions: Choosing the minimal transverse-momentum threshold, , that results in is equivalent to gradually raising the threshold until exactly half of the patches contain no particles, which ensures that the median is zero. This is illustrated in Fig. 1. Computationally, is straightforward to evaluate: one determines, for each patch , the of the hardest particle in that patch, and then is given by the median of values:2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\begin{aligned} p_t^{\text {cut}} = \underset{i \in \text {patches}}{\text {median}} \left\{ p_{ti}^{\max } \right\} . \end{aligned}$$\end{document}ptcut=mediani∈patchesptimax.With this choice, half the patches will contain only particles that have . These patches will be empty after application of the threshold, leading to a zero result for as defined in Eq. (1).2 The computational time to evaluate as in Eq. (2) scales linearly in the number of particles and the method should be amenable to parallel implementation.


SoftKiller, a particle-level pileup removal method.

Cacciari M, Salam GP, Soyez G - Eur Phys J C Part Fields (2015)

Illustration of the SoftKiller method. The left plot depicts particles in an event, with the hard-event particles shown in blue and the pileup particles shown in red. On the right, the same event after applying the SoftKiller. The vertical dotted lines represent the edges of the patches used to estimate the pileup density
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4376401&req=5

Fig1: Illustration of the SoftKiller method. The left plot depicts particles in an event, with the hard-event particles shown in blue and the pileup particles shown in red. On the right, the same event after applying the SoftKiller. The vertical dotted lines represent the edges of the patches used to estimate the pileup density
Mentions: Choosing the minimal transverse-momentum threshold, , that results in is equivalent to gradually raising the threshold until exactly half of the patches contain no particles, which ensures that the median is zero. This is illustrated in Fig. 1. Computationally, is straightforward to evaluate: one determines, for each patch , the of the hardest particle in that patch, and then is given by the median of values:2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\begin{aligned} p_t^{\text {cut}} = \underset{i \in \text {patches}}{\text {median}} \left\{ p_{ti}^{\max } \right\} . \end{aligned}$$\end{document}ptcut=mediani∈patchesptimax.With this choice, half the patches will contain only particles that have . These patches will be empty after application of the threshold, leading to a zero result for as defined in Eq. (1).2 The computational time to evaluate as in Eq. (2) scales linearly in the number of particles and the method should be amenable to parallel implementation.

Bottom Line: It removes the softest particles in an event, up to a transverse momentum threshold that is determined dynamically on an event-by-event basis.In simulations, this simple procedure appears to be reasonably robust and brings superior jet resolution performance compared to existing jet-based approaches.It is also nearly two orders of magnitude faster than methods based on jet areas.

View Article: PubMed Central - PubMed

Affiliation: Université Paris Diderot, Paris, France ; Sorbonne Universités, UPMC Univ Paris 06, UMR 7589, LPTHE, 75005 Paris, France ; CNRS, UMR 7589, LPTHE, 75005 Paris, France.

ABSTRACT

Existing widely used pileup removal approaches correct the momenta of individual jets. In this article we introduce an event-level, particle-based pileup correction procedure, SoftKiller. It removes the softest particles in an event, up to a transverse momentum threshold that is determined dynamically on an event-by-event basis. In simulations, this simple procedure appears to be reasonably robust and brings superior jet resolution performance compared to existing jet-based approaches. It is also nearly two orders of magnitude faster than methods based on jet areas.

No MeSH data available.