Soft-Collinear Effective Theory

2020 ◽  
pp. 307-361 ◽  
Author(s):  
Thomas Becher
Keyword(s):  
Cross Sections ◽  
Vector Current ◽  
Jet Physics ◽  
Effective Theory ◽  
Event Shape ◽  
Sudakov Form Factor ◽  
Shape Variable ◽  
Soft Collinear Effective Theory ◽  
Jet Cross Sections ◽  
Event Shape Variable

The lectures that appear within this chapter provide an introduction to soft-collinear effective theory (SCET). It begins by discussing resummation for soft-photon effects in QED, including soft photons in electron–electron scattering and the expansion of loop integrals and the method of regions event-shape variables. It then covers SCET specifically, including the method of regions for the Sudakov form factor, effective Lagrangians, the vector current in SCET, and resummation by renormalization group (RG) evolution. It covers applications of SCET in jet physics, describes the characteristic feature in jet processes of Sudakov logarithms, and discusses factorization for the event-shape variable thrust and factorization and resummation for jet cross sections.

scholarly journals Massive event-shape distributions at N2LL

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Alejandro Bris ◽  
Vicent Mateu ◽  
Moritz Preisser
Keyword(s):  
Cross Sections ◽  
Numerical Study ◽  
Renormalization Group Equation ◽  
Effective Theory ◽  
Event Shape ◽  
Group Equation ◽  
Soft Collinear Effective Theory ◽  
Fixed Order ◽  
Collinear Limit ◽  
Event Shapes

Abstract In a recent paper we have shown how to optimally compute the differential and cumulative cross sections for massive event-shapes at $$ \mathcal{O}\left({\alpha}_s\right) $$ O α s in full QCD. In the present article we complete our study by obtaining resummed expressions for non-recoil-sensitive observables to N2LL + $$ \mathcal{O}\left({\alpha}_s\right) $$ O α s precision. Our results can be used for thrust, heavy jet mass and C-parameter distributions in any massive scheme, and are easily generalized to angularities and other event shapes. We show that the so-called E- and P-schemes coincide in the collinear limit, and compute the missing pieces to achieve this level of accuracy: the P-scheme massive jet function in Soft-Collinear Effective Theory (SCET) and boosted Heavy Quark Effective Theory (bHQET). The resummed expression is subsequently matched into fixed-order QCD to extend its validity towards the tail and far- tail of the distribution. The computation of the jet function cannot be cast as the dis- continuity of a forward-scattering matrix element, and involves phase space integrals in d = 4 − 2ε dimensions. We show how to analytically solve the renormalization group equation for the P-scheme SCET jet function, which is significantly more complicated than its 2-jettiness counterpart, and derive rapidly-convergent expansions in various kinematic regimes. Finally, we perform a numerical study to pin down when mass effects become more relevant.

scholarly journals Measurements of jet-related observables at the LHC

2015 ◽  
Vol 30 (31) ◽  
pp. 1546004 ◽  
Author(s):  
P. Kokkas
Keyword(s):  
Monte Carlo ◽  
Cross Sections ◽  
Event Shape ◽  
Leading Order ◽  
Centre Of Mass ◽  
Mass Energy ◽  
Perturbative Quantum Chromodynamics ◽  
Perturbative Quantum ◽  
Jet Shapes ◽  
Jet Cross Sections

During the first years of the LHC operation a large amount of jet data was recorded by the ATLAS and CMS experiments. In this review several measurements of jet-related observables are presented, such as multi-jet rates and cross sections, ratios of jet cross sections, jet shapes and event shape observables. All results presented here are based on jet data collected at a centre-of-mass energy of 7 TeV. Data are compared to various Monte Carlo generators, as well as to theoretical next-to-leading-order calculations allowing a test of perturbative Quantum Chromodynamics in a previously unexplored energy region.

scholarly journals Phenomenological and theoretical developments in jet physics at the LHC

2015 ◽  
Vol 30 (31) ◽  
pp. 1546001 ◽  
Author(s):  
Matteo Cacciari
Keyword(s):  
Cross Sections ◽  
High Energy Physics ◽  
High Energy ◽  
Jet Physics ◽  
The Status ◽  
History Of ◽  
Jet Cross Sections ◽  
New Algorithms ◽  
Energy Physics ◽  
Theoretical Developments

We review the history of jets in high energy physics, and describe in more detail the developments of the past ten years, discussing new algorithms for jet finding and their main characteristics, and summarising the status of perturbative calculations for jet cross sections in hadroproduction. We also describe the emergence of jet grooming and tagging techniques and their application to boosted jets analyses.

scholarly journals Energy-energy correlation in hadronic Higgs decays: analytic results and phenomenology at NLO

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Jun Gao ◽  
Vladyslav Shtabovenko ◽  
Tong-Zhi Yang
Keyword(s):  
Light Quark ◽  
Statistical Error ◽  
Event Shape ◽  
Leading Order ◽  
Energy Correlation ◽  
Quark Masses ◽  
Shape Variable ◽  
Fixed Order ◽  
Perturbative Uncertainty ◽  
Event Shape Variable

Abstract In this work we complete the investigation of the recently introduced energy-energy correlation (EEC) function in hadronic Higgs decays at next-to-leading order (NLO) in fixed-order perturbation theory in the limit of vanishing light quark masses. The full analytic NLO result for the previously unknown EEC in the H → $$ q\overline{q} $$ q q ¯ + X channel is given in terms of classical polylogarithms and cross-checked against a numerical calculation. In addition to that, we discuss further corrections to predictions of the Higgs EEC event shape variable, including quark mass corrections, effects of parton shower and hadronization. We also estimate the statistical error on the measurements of the Higgs EEC at future Higgs factories and compare with the current perturbative uncertainty.

scholarly journals The Evolution of Soft Collinear Effective Theory

2015 ◽  
Vol 37 ◽  
pp. 1560045 ◽  
Author(s):  
Christopher Lee
Keyword(s):  
Cross Sections ◽  
Nuclear Physics ◽  
Degrees Of Freedom ◽  
Heavy Ion ◽  
High Energy ◽  
Effective Field ◽  
Effective Theory ◽  
Ion Collisions ◽  
Soft Collinear Effective Theory ◽  
Single Scale

Soft Collinear Effective Theory (SCET) is an effective field theory of Quantum Chromodynamics (QCD) for processes where there are energetic, nearly lightlike degrees of freedom interacting with one another via soft radiation. SCET has found many applications in high-energy and nuclear physics, especially in recent years the physics of hadronic jets in e+e-, lepton-hadron, hadron-hadron, and heavy-ion collisions. SCET can be used to factorize multi-scale cross sections in these processes into single-scale hard, collinear, and soft functions, and to evolve these through the renormalization group to resum large logarithms of ratios of the scales that appear in the QCD perturbative expansion, as well as to study properties of nonperturbative effects. We overview the elementary concepts of SCET and describe how they can be applied in high-energy and nuclear physics.

scholarly journals THE 1-JETTINESS EVENT-SHAPE FOR DIS WITH NNLL RESUMMATION

2014 ◽  
Vol 25 ◽  
pp. 1460041 ◽  
Author(s):  
ZHONG-BO KANG ◽  
XIAOHUI LIU ◽  
SONNY MANTRY ◽  
JIANWEI QIU
Keyword(s):  
Nuclear Physics ◽  
Quantitative Measure ◽  
Effective Theory ◽  
Event Shape ◽  
Final State ◽  
Global Event ◽  
Soft Collinear Effective Theory ◽  
Factorization Formula ◽  
Single Jet ◽  
Nuclear Targets

We propose the use of 1-jettiness, a global event shape, for exclusive single jet production in lepton-nucleus deep inelastic scattering (DIS). We derive a factorization formula, using the Soft-Collinear Effective Theory, differential in the transverse momentum and rapidity of the jet and the 1-jettiness event shape. It provides a quantitative measure of the shape of the final-state QCD radiation in the presence of the hard jet, providing a useful powerful probe of QCD and nuclear physics. For example, one expects differences in the observed pattern of QCD radiation between large and small nuclei and these can be quantified by the 1-jettiness event shape. Numerical results are given for this new DIS event shape at leading twist with resummation at the next-to-next-to-leading logarithmic (NNLL) level of accuracy, for a variety of nuclear targets. Such studies would be ideal at a future EIC or LHeC electron-ion collider, where a range of nuclear targets are planned.

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