Colour Of Quarks


Another property of Quark is the Color” or Color Charge” of Quarks. According to the Color Charge of Quarks :


In The Theory Of Quantum Chromodynamics, The Color Charge Is The Property Of Quarks Which Is Related To The Particle Strong Interactions (  Strong Interaction : It Is The Mechanism Which Is Responsible For Strong Nuclear Force ).


As we have learned in the previous chapters that, Color of Quarks or Color Charge of Quarks is not related to the real perception or real visual perception of Color. The Physicists have just put the term “Color” because the charge between particles is responsible for Strong Interaction Force.  These charge which create Strong Force are connected to Three Primary Colors which are easily detected by Human Eyes. The Three Color of Quarks show’s the Quantum State of Quarks. Color Charge of Quarks is one of the very complicated method to show the properties of Quark. The sets of Color Combination, Which are given by Physicists are as follows:


  • Red


  • Green

  • Blue



In Science, All Particles have their Anti-Particles. These Anti-Particles are also represented by “Colors” which shows interactions between Anti-Particles. The Color Charges on Anti-Paticles will be :


  • Anti-Red (Cyan)


  • Anti-Green (Magenta)


  • Anti-Blue (Yellow)


Understanding Combination Of Colour Charges :


Let’s take some examples of combination of Quarks, Which combine to form heavier elements such as “Baryons”. Baryons is the result of combination of Three Quarks. But each quarks will have one Color i.e. Either Red , Green or Blue . But what about particles which are composed of only one Quark & one Anti-Quark such as Mesons”. In this situation Quark can be found in any Color Either Red, Green or Blue & Anti-Quark will be the Anti-Color of the Quark by which Meson is composed of. Suppose, If Meson is composed of Blue Color Quark then it’s Anti-Quark will consist of Anti-Blue Color (Yellow). Thus, Combination of Blue Color Quark & Anti-Blue (Yellow) Quark will result into a Colorless Meson”.


In Fact the combination of Color Charges will always results into a “Colorless Particle”. For Example, Baryon consist of One Red , One Green & One Blue Color Quark. When all these Three Color Quark combines it results into a Colorless Baryon”. Similarly, All other combination of Color Charges results into a Colorless Particle”.



Similarly the combination of Color Charges of Three Anti-Quarks results into to a “Colorless Anti-Particle”.



Field Lines Of Quarks :


Another way of showing Interaction between Color Charge is drawing Field Lines” between Quarks. Field Lines of Color Charge will be analogues to that of “Electric Field Lines”. But Field Lines of Color Charge will not arc much outward from one Quark to another because Quarks are confined to each other with Strong Force” created by “Gluons” .



In the above figure, Top figures shows the Strength” of Color Charges. The Strength of Colour Charges are Neutral” or at “Ternary Neutral States” or “Binary Neutral States”. We can see that the “Arrow” between Quarks are at Same Distance” from all each other.  Where G is the Gluon Field Strength . In the Bottom Figure, Field Lines showing the Quark & Anti-Quark combination. Which shows the interaction between Red Quark & Anti-Red Quark, Green Quark & Anti-Green Quark, Blue Quark & Anti-Blue Quark respectively.


Mathematical Analysis :


There are other some Mathematical ways to show the Color charge of Quarks. This can be defined as “Coupling Constant” & “Charge” of a Quark. In Quantum Chromodynamics Coupling Constant is different from Charge but they are related to each other.


Coupling Constant :


Coupling Constant Set’s The Intensity Or The Magnitude Of Force Of Interaction Between Quarks. For Example : In Quantum Electrodynamics, The Fine Structure Constant (It Is A Physical Constant, Which Characterise The “Strength” Of Electromagnetic Interaction Between Elementary Charged Particles), Is A Coupling Constant.

Charge :


Charge Can Be Explained By “Gauge Theory”. Gauge Theory Is A Type Of Field Theory In Which The Lagrangian” Is Invariant Under A Continuous Group Of Local Transformation. The Charge Of A Particle With Gauge Theory Show’s Transformation Of A Particle Under Gauge Symmetry.

For Example : Electron Has -1 Charge & Positron Has +1 Charge On It. The Gauge Transformation In Some Sense Will Have Opposite” Effects On Them.


Quarks, Gluons & Field Charge With Gauge Transformation :


Now, Let us combine the Quarks, Gluon Field & Color Charges. There is a fundamental representation of Quark, Which contain Triplet Of Field’s together, Denoted by Ψ. The Anti-Quark Field also contains Triplet Of Field. They both can be represented as :



The Three indices in the Triplet given above (“Ψ1”, “Ψ2” , “Ψ3”) are usually identified with the Three Colors Of Quarks. Now, Color of Quarks will change, Which can be theorised by Gauge Transformation & the new Color combination of Quark will be the analogous to the old Color combination of Quarks.


              The Quarks Before Color Change

          The Quark Above Emits A Combine Blue & Anti-Green Gluons



The Green Quark Absorbs Combine Blue & Anti-Green Quark. Now The Green Quark Transformed Into Blue Color & Blue Color Quark Is Transformed Into Green Color  .


The above diagram represents that how the Gauge Transformation” & New Color Combination is taking place between Quark. But even after New Color Combination the Color Charge of the system remains Conserved.



Neutron Gauge Transformation: 


Above Animation show’s “Neutron”. As Neutron is composed of Two Down Quark & One Up Quark. The Particle travelling from one Quark to other are “Gluons” also known as “Gluon Particle Field”, The Gluons travelling from one Quark to other as shown above, Have One Color Charge & One Anti-Color Charge. The Quark which absorb Gluon, Will transform into the color of absorbed Color Charge. Suppose if One Down Quark absorb Blue Color Gluon then that Down Quark will be Transformed into Blue Color & the Quark which emits Gluon will take Color of Quark, Which absorbs it’s Gluon. For example : If Down Quark have Green Color & Up Quark have Blue Color. Now, If Down Quark emits Green Color Gluon & Anti-Blue Color (Yellow Color) Gluon then, This Quark will Transform into Blue Color & Up Quark will absorb the Green Color Gluon & Anti-Blue Color (Yellow Color) Gluon (Which was emitted by Down Quark) & It will Transform into Green Color. Hence, This process also follow’s the “Law Of Conservation Of Color’s”.


There are many more complicated perception of Color Charge & It is not really easy to visualise Quark’s, Gluon Field’s & Color Charge’s. Still Particle Physicist’s are working on Quark Color Charge Properties, To make it more simpler & coming more close to the perfection in understanding Properties of Quarks, Which can determine the behaviour of Quarks in a “Quantum Manner”.