Strong- vs. weak-coupling pictures of jet quenching: a dry run using QED
- PDF / 1,448,761 Bytes
- 48 Pages / 595.276 x 841.89 pts (A4) Page_size
- 90 Downloads / 167 Views
Springer
Received: October 20, Revised: March 11, Accepted: April 4, Published: May 2,
2018 2019 2019 2019
Peter Arnold,a Shahin Iqbalb and Tanner Rasec a
Department of Physics, University of Virginia, 382 McCormick Road, Charlottesville, Virginia 22904-4714, U.S.A. b National Centre for Physics, Quaid-i-Azam University Campus, Shahdra Valley Road, P.O. Box No. 2141, Islamabad 44000, Pakistan c Department of Physics, University of Washington, 3910 15th Ave. NE, Seattle, Washington 98195-1560, U.S.A.
E-mail: [email protected], [email protected], [email protected] Abstract: High-energy partons (E T ) traveling through a quark-gluon plasma lose energy by splitting via bremsstrahlung and pair production. Regardless of whether or not the quark-gluon plasma itself is strongly coupled, an important question lying at the heart of philosophically different approaches to energy loss is whether the high-energy partons of an in-medium shower can be thought of as a collection of individual particles, or whether their coupling to each other is also so strong that a description as high-energy “particles” is inappropriate. We discuss some possible theorists’ tests of this question for simple situations (e.g. an infinite, non-expanding plasma) using thought experiments and firstprinciples quantum field theory calculations (with some simplifying approximations). The physics of in-medium showers is substantially affected by the Landau-Pomeranchuk-Midgal (LPM) effect, and our proposed tests require use of what might be called “next-to-leading order” LPM results, which account for quantum interference between consecutive splittings. The complete set of such results is not yet available for QCD but is already available for the theory of large-Nf QED. We therefore use large-Nf QED as an example, presenting numerical results as a function of Nf α, where α is the strength of the coupling at the relevant high-energy scale characterizing splittings of the high-energy particles. Keywords: Perturbative QCD, Quark-Gluon Plasma ArXiv ePrint: 1810.06578
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP05(2019)004
JHEP05(2019)004
Strong- vs. weak-coupling pictures of jet quenching: a dry run using QED
Contents 1 1 3 6 10 12 12
2 Stopping distributions 2.1 Simplifying assumptions 2.2 More assumptions for the analysis in the main text 2.3 Integro-differential equation for the charge distribution ρ(z) 2.4 Warm-up: charge stopping with no logarithms 2.4.1 Results for moments 2.4.2 Measures of size of NLO correction 2.5 Charge stopping with single logarithms 2.6 Charge stopping with double logarithms, etc.
13 13 14 16 17 17 18 19 21
3 The 3.1 3.2 3.3
21 21 23 24
example of large-Nf QED The relevant diagrams Formulas and numerical integrals Results (0)
4 Renormalization scale dependence of ∆`stop /`stop
25
5 Caveats for χα test of strong vs. weak-coupled splitting 5.1 Warm up/review for a single logarithm 5.2 Double logarithms
26 26 28
6 Conclusion
28
A Energy stopping distance and other general
Data Loading...
