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Title: Dissecting Soft Radiation with Factorization

An essential part of high-energy hadronic collisions is the soft hadronic activity that underlies the primary hard interaction. It includes soft radiation from the primary hard partons, secondary multiple parton interactions (MPI), and factorization-violating effects. The invariant mass spectrum of the leading jet in $$Z+\mathrm{jet}$$ and $$H+\mathrm{jet}$$ events is directly sensitive to these effects, and we use here a QCD factorization theorem to predict its dependence on the jet radius $R$, jet $${p}_{T}$$, jet rapidity, and partonic process for both the perturbative and nonperturbative components of primary soft radiation. We prove that the nonperturbative contributions involve only odd powers of $R$, and the linear $R$ term is universal for quark and gluon jets. The hadronization model in Pythia8 agrees well with these properties. The perturbative soft initial state radiation (ISR) has a contribution that depends on the jet area in the same way as the underlying event, but this degeneracy is broken by dependence on the jet $${p}_{T}$$. The size of this soft ISR contribution is proportional to the color state of the initial partons, yielding the same positive contribution for $$gg{\rightarrow}Hg$$ and $$gq{\rightarrow}Zq$$, but a negative interference contribution for $$q\overline{q}{\rightarrow}Zg$$. Hence, measuring these dependencies allows one to separate hadronization, soft ISR, and MPI contributions in the data.
Authors:
 [1] ;  [2] ;  [3]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Theoretical Physics
  2. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group
  3. Nikhef, Amsterdam (Netherlands). Theory Group; Univ. of Amsterdam (Netherlands). Inst. for Theoretical Physics Amsterdam (ITFA)
Publication Date:
Grant/Contract Number:
SC0011090; TA 867/1-1; PIIF-GA-2012-328913
Type:
Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 114; Journal Issue: 9; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Nikhef, Amsterdam (Netherlands)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26); German Research Foundation (DFG); European Union (EU)
Country of Publication:
United States
Language:
English
OSTI Identifier:
1505723
Alternate Identifier(s):
OSTI ID: 1181456

Stewart, Iain W., Tackmann, Frank J., and Waalewijn, Wouter J.. Dissecting Soft Radiation with Factorization. United States: N. p., Web. doi:10.1103/physrevlett.114.092001.
Stewart, Iain W., Tackmann, Frank J., & Waalewijn, Wouter J.. Dissecting Soft Radiation with Factorization. United States. doi:10.1103/physrevlett.114.092001.
Stewart, Iain W., Tackmann, Frank J., and Waalewijn, Wouter J.. 2015. "Dissecting Soft Radiation with Factorization". United States. doi:10.1103/physrevlett.114.092001. https://www.osti.gov/servlets/purl/1505723.
@article{osti_1505723,
title = {Dissecting Soft Radiation with Factorization},
author = {Stewart, Iain W. and Tackmann, Frank J. and Waalewijn, Wouter J.},
abstractNote = {An essential part of high-energy hadronic collisions is the soft hadronic activity that underlies the primary hard interaction. It includes soft radiation from the primary hard partons, secondary multiple parton interactions (MPI), and factorization-violating effects. The invariant mass spectrum of the leading jet in $Z+\mathrm{jet}$ and $H+\mathrm{jet}$ events is directly sensitive to these effects, and we use here a QCD factorization theorem to predict its dependence on the jet radius $R$, jet ${p}_{T}$, jet rapidity, and partonic process for both the perturbative and nonperturbative components of primary soft radiation. We prove that the nonperturbative contributions involve only odd powers of $R$, and the linear $R$ term is universal for quark and gluon jets. The hadronization model in Pythia8 agrees well with these properties. The perturbative soft initial state radiation (ISR) has a contribution that depends on the jet area in the same way as the underlying event, but this degeneracy is broken by dependence on the jet ${p}_{T}$. The size of this soft ISR contribution is proportional to the color state of the initial partons, yielding the same positive contribution for $gg{\rightarrow}Hg$ and $gq{\rightarrow}Zq$, but a negative interference contribution for $q\overline{q}{\rightarrow}Zg$. Hence, measuring these dependencies allows one to separate hadronization, soft ISR, and MPI contributions in the data.},
doi = {10.1103/physrevlett.114.092001},
journal = {Physical Review Letters},
number = 9,
volume = 114,
place = {United States},
year = {2015},
month = {3}
}