high energy physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and b ...

, thrust is a property, (one of the

event shape observables In high energy physics, event shapes observables are quantities used to characterize the geometry of the outcome of a collision between high energy particles in a collider. Specifically, event shapes observables quantify the general pattern trace ...

) used to characterize the collision of

high energy particles Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and ...

in a

collider A collider is a type of particle accelerator which brings two opposing particle beams together such that the particles collide. Colliders may either be ring accelerators or linear accelerators. Colliders are used as a research tool in particle ...

. When two

collide, they typically produce jets of secondary particles. This happens when one or several

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All common ...

-antiquark pairs are produced during the collision. Each

colored ''Colored'' (or ''coloured'') is a racial descriptor historically used in the United States during the Jim Crow Era to refer to an African American. In many places, it may be considered a slur, though it has taken on a special meaning in South ...

quark/antiquark pair travels its separate way and subsequently hadronizes. Many new particles are created by the hadronization process and travel in approximately the same direction as the original pair. This set of particles constitutes a jet. The thrust S. Brandt, C. Peyrou, R. Sosnowski, and A. Wroblewski (1964), “The Principal axis of jets. An Attempt to analyze high-energy collisions as two-body processes“, Phys. Lett. 12 57–61. E. Farhi (1977), “A QCD Test for Jets“, Phys. Rev. Lett. 39 1587–1588. quantifies the coherence, or ″jettiness″ of the group of particles resulting from one collision. It is defined as:V. D. Barger, R. J. N. Phillips (1997) “Collider Physics” Frontier in Physics, Addison-Wesley Publishing Company, Inc.

T= \underset \bigg frac\bigg /math>,

where p_i is the

momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass ...

of particle

i

, and

n

is a unit vector that maximizes

T

and defines the thrust axis. The sum is over all the final particles resulting from the collision. In practice, the sum may be carried over the detected particles only. The thrust

T

is stable under collinear splitting of particles, and therefore it is a robust observable, largely insensitive to the details of the specific hadronization process.

References

Experimental particle physics Quantum chromodynamics {{particle-stub