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Quark fragmentation in the θ vacuum
Zhong-Bo Kang1, Dmitri E Kharzeev
1RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 1197-5000, USA.
Physical Review Letters
|March 17, 2011
Summary
This study explores quark fragmentation within the complex Quantum Chromodynamics (QCD) vacuum. It reveals new parity-odd fragmentation functions and their observable effects in electron-positron collisions, offering insights into fundamental symmetries.
Area of Science:
- Particle Physics
- Quantum Chromodynamics (QCD)
- High-Energy Physics
Background:
- The Quantum Chromodynamics (QCD) vacuum is a complex superposition of states with varying topological numbers, linked by tunneling phenomena.
- Gauge field configurations, such as instantons, create local parity-odd domains within Minkowski spacetime, impacting fundamental symmetries.
- While QCD globally conserves parity (P) and charge-parity (CP) symmetries, local topological structures can lead to observable symmetry violations.
Purpose of the Study:
- To investigate quark fragmentation within a topologically nontrivial QCD vacuum background.
- To identify and characterize new parity-odd fragmentation functions that may arise in this context.
- To explore the experimental signatures of these novel fragmentation functions in dihadron production.
Main Methods:
- Theoretical analysis of quark fragmentation in the QCD vacuum with non-trivial topology.
- Identification of emergent parity-odd fragmentation functions.
- Study of experimental observables in electron-positron (e+e-) collisions, specifically dihadron production.
Main Results:
- Two novel types of parity-odd fragmentation functions emerge even though QCD globally conserves P and CP symmetries.
- These functions manifest in specific dihadron correlations in e+e- collisions.
- A new parity-odd correlation proportional to sin(ϕ1+ϕ2) is identified, which is observable on an event-by-event basis.
Conclusions:
- The existence of parity-odd fragmentation functions in the QCD vacuum provides a mechanism for observing P and CP violation effects.
- Dihadron production in e+e- collisions serves as a sensitive probe for these novel fragmentation functions and associated correlations.
- The event-by-event observable sin(ϕ1+ϕ2) correlation offers a unique signature for probing the topological structure of the QCD vacuum.
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