Abstract
This chapter is dedicated to the specific applications of substructure techniques to discriminate quark-initiated jets from gluon-initiated jets. We begin with a brief discussion on how to tentatively define quark- and gluon-initiated jets. We then concentrate on two broad classes of observables: (i) shape observables like angularities or energy-correlation functions, and (ii) multiplicity-based observables like the iterated soft-drop multiplicity. In each case, we provide a basic analytic understanding of the tools based on the resummation techniques introduced in Chap. 4. We then discuss the key properties of the tools and assess their performance on Monte-Carlo simulations, highlighting the features which are reproduced by the simple analytic calculations.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Notes
- 1.
In practice, this definition of \(R^{\prime }_{\text{mMDT/SD}}(v)\) introduces a discontinuity in the differential distribution at v = z cut. This discontinuity is strictly-speaking subleading and can be avoided by defining R′ using a finite-difference derivative: R′(v) = [R(ve − Δ) − R(v)]∕ Δ, with Δ a constant number, which respects NLL accuracy (see [50]). This is what we have done for the results presented below, using Δ = 0.5.
- 2.
- 3.
For multiplicity-based observables, we have interpolated linearly between the discrete multiplicities.
- 4.
In the case of ISD, we have applied mMDT recursively, giving a behaviour equivalent to using β = 0 and a k t cut as shown in the middle plot of Fig. 7.6.
- 5.
For the results of Fig. 7.12 we have simply interpolated between different points in the distribution.
References
A.J. Larkoski, S. Marzani, G. Soyez, J. Thaler, Soft drop. J. High Energy Phys. 1405, 146 (2014). [1402.2657]
J. Gallicchio, M.D. Schwartz, Quark and Gluon jet substructure. J. High Energy Phys. 04, 090 (2013). [1211.7038]
J.R. Andersen et al., Les Houches 2015: Physics at TeV Colliders Standard Model Working Group Report, in 9th Les Houches Workshop on Physics at TeV Colliders (PhysTeV 2015), Les Houches, June 1–19, 2015 (2016). 1605.04692
A.J. Larkoski, G.P. Salam, J. Thaler, Energy correlation functions for jet substructure. J. High Energy Phys. 1306, 108 (2013). [1305.0007]
C. Frye, A.J. Larkoski, J. Thaler, K. Zhou, Casimir meets Poisson: improved quark/gluon discrimination with counting observables. J. High Energy Phys. 09, 083 (2017). [1704.06266]
P. Gras, S. Hoeche, D. Kar, A. Larkoski, L. Lönnblad, S. Platzer et al., Systematics of quark/gluon tagging. J. High Energy Phys. 07, 091 (2017). [1704.03878]
S. Bright-Thonney, B. Nachman, Investigating the topology dependence of quark and gluon jets. 1810.05653
Z. Nagy, Next-to-leading order calculation of three-jet observables in hadron-hadron collisions. Phys. Rev. D68, 094002 (2003). [hep-ph/0307268]
J.M. Campbell, R.K. Ellis, Update on vector boson pair production at hadron colliders. Phys. Rev. D60, 113006 (1999). [hep-ph/9905386]
J.M. Campbell, R.K. Ellis, W.T. Giele, A multi-threaded version of MCFM. Eur. Phys. J. C75, 246 (2015). [1503.06182]
Author information
Authors and Affiliations
Rights and permissions
Copyright information
© 2019 Springer Nature Switzerland AG
About this chapter
Cite this chapter
Marzani, S., Soyez, G., Spannowsky, M. (2019). Quark/Gluon Discrimination. In: Looking Inside Jets. Lecture Notes in Physics, vol 958. Springer, Cham. https://doi.org/10.1007/978-3-030-15709-8_7
Download citation
DOI: https://doi.org/10.1007/978-3-030-15709-8_7
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-15708-1
Online ISBN: 978-3-030-15709-8
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)