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Questions tagged [strong-force]

The strong force or interaction is responsible for the confinement of quarks inside hadrons and the binding of nucleons inside a nucleon, and it is described by the gauge theory of QCD. It provides most of the mass of ordinary matter, which is dominated by the nucleons, proton and neutron: over 99% of the mass of these is attributable to the strong-force field energy. Use where technical details of QCD are not warranted.

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Binding Energy and mass defect

Binding energy is the energy required to separate the nucleus into its constituent particles. The thing is that I read in a book that the binding energy is also the energy equal to the mass defect. ...
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What drives the charge separation in atoms?

In atoms charges are neatly separated. Instead of pairing which seems natural they all stick together with their peers. What drives this peer behaviour? Why is it stable?
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How does the nuclear interaction keep protons and neutrons together?

The strong force holds atoms hadrons together by using gluons to change the color charge of quarks and making the hadrons color nutral. But how does the nuclear force keep protons together, I heard ...
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Why does the pion live in a representation of isospin SU(2) and is the mediator of the strong force generated by color SU(3)?

Why does the pion live in a representation of isospin $\rm SU(2)$ and is the mediator of the strong force generated by color $\rm SU(3)$? I somehow find strange that this is the case. Given that $\rm ...
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The strong CP problem in Grand Unified Theories

The strong CP problem could, in principle, be solved by a massless up quark. Can this solution be embedded in Grand Unified Theories, such as $SO(10)$ (or $SU(5)$)? These theories, in particular $SO(...
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Where do the color indices come back in $SU(3)$ Yang-Mills Quantization?

Can the partition function of $SU(3)$ (the Generic Partition function for a yang-mills theory found on the linked wiki page below), be split into a sum of 8 functional integrals for each gauge field? ...
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Does it really make sense to talk about the color of gluons?

It is my understanding that by enforcing SU(3) gauge invariance on our lagrangian of 3-colored quark fields, we are forced to accept the existence of 8 new massless vector fields, the gluons. The 8 ...
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How does the exchange of pions result in the strong force?

I understand that the residual strong force is a result of an exchange of pions. But I fail to understand how this exchange results in a force that holds nuclei together! May this query please be ...
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How do we show that gluon-fields have color?

I understand how to derive the QCD lagrangian based on certain assumptions about Quark fields and $SU(3)$ gauge invariance and in the final expression one finds the term $(A_µ)^c*T_c$ where $T_c$ is ...
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When/ how were/are quarks formed?

We know that all particles can eventually be converted into energy. We know also that electrons were and still are formed by pair production from a 1MeV photon. Do physicists have yet any idea how ...
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Unstable vs. stable nuclei plotted on a graph

The enclosed graph shows the number of Protons on the x-axis (Z), and the number of Neutrons on the y-axis for all elements (N). Stable combinations are marked by black squares, whereas unstable ones ...
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isospin conservation for total isospin or third component of isospin?

In strong interaction, is total isospin or 3rd component of isospin conversed or they are both conserved? Thank you!
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Why does the weak nuclear interaction have a shorter range than strong nuclear interaction?

My textbook says: "Weak nuclear interaction acts on protons, neutrons, electrons and neutrinos in order to bring about beta decay. It has very short range (10-18m)" "Strong nuclear interaction ...
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Half-life of $W$ and $Z$ bosons

$W$ and $Z$ bosons should decay through weak interaction. But their half-life is around $\tau = 10^{-25} s$ which is a typical value for particles decaying through strong force (instead of a $10^{-12}-...
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What happens if a neutron flies towards a nucleus?

Rutherford experiment shows that alpha-particles when they fly towards metal foil sometimes (in minority of cases) can bounce. An explanation proposed was that atoms in fact have positively charged ...
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Do color changing interactions between up and down quark exist?

In our Standard Model course we wrote down the term for the quark-gluon interaction of the left handed $SU(2)_L$ quark doublet $q_L$ as: $\mathscr{L} = … + \bar{q}_L \gamma^\mu iG^a_\mu(x) \lambda^a ...
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What are chromoelectric and chromomagnetic fields?

Are they the normal elctric and magnetic fields from Maxwell fields? Or are they just the corresponding components from $G_{\mu\nu}^a$ (the gluon fields), say chromoelectric fields are simply $G_{0i}^...
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Unification of the strong and electromagnetic interaction

Is it somehow possible to theoretically unify the electric charge in electromagnetic interaction with the colour charge in the strong interaction and how these charges give rise to the respective ...
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Antimatter: weak and strong forces

Antimatter is known to have equal mass to matter and opposite charge sign. Positron has the same mass as electron and opposite sign of charge, anti-proton has the same mass as proton and opposite sign ...
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A place of space-time where the only fundamental interaction will be the gravitational forces: does make sense?

We know that there are four (fundamental forces) fundamental interactions of nature, this Wikipedia. I'm curious about if we can speculate that there exists a place of the space-time in which, after ...
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Bag model and MFT

Can I think of the MIT Bag model as an application of mean field theory (MFT) in nthe domain of nuclear physics? All the interactions between quarks are mediated via strong interaction, whose exact ...
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Why isn't there an universal nuclear model? [closed]

What problems does (low energy) nuclear physics face when trying to model the nuclear structure? Why isn't possible to have a theoretical model that can be used to describe any nucleus?
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What is the time period in which an interaction with a π-meson takes place?

The longer-range inter-nucleon force is not a direct result of the gluon field, but is indirectly affected by a quark-antiquark pair (meson). If this ‘residual’ strong interaction between nucleons ...
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How are exchange terms in phenomenological nuclear potentials related to the exchange of nuclear force carrirer particles?

Consider a proton-neutron system. Phenomenlogical nucleon-nucleon potentials contain exchange forces terms (Majorana, Bartlett and Heisenberg terms), which are linked to the symmetry of the state w.r....
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Why is the distance between two nucleons greater than the minimum energy point?

The potential energy associated to the interaction between nucleons has its minimum (point of equilibrium) at $r\sim 0.7 fm$, as showed in the following graph: Nevertheless, there are two facts ...
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Does the strong force increase or decrease with aligned spins?

The deuterium exists only with the proton and neutron of aligned spin, which suggests that the residual strong force is greated with aligned spins, i.e. the binding energy is greater if the spins are ...
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Measuring characteristic time of strong and weak interaction using cross section

Consider a scattering between two particles a and b that produces two particles c and d: d is stable, while c decays in two other different particles e and f. The first interaction is by strong ...
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Description of strong force as exchange of meson or as exchange of quark and antiquark

The (residual) strong force between nucleons can be desribed as The exchange of a meson (from a nucleon to the other), as in picture b) The exchange of a quark and an antiquark: in picture a) one ...
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Why is $SU(3)$ and not $U(3)$ the correct gauge symmetry? [duplicate]

If quarks come in three colours $r$, $g$ and $b$ than (neglecting all other quantum numbers and spacial freedom for now) a state of a quark would be a vector in $\mathbb{C}^3$. If we are now looking ...
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Hadrons in realistic string phenomenology

String theory contains a number of models of baryons as branes, notably the Sakai-Sugimoto model. But I don't remember ever seeing a discussion of baryons, or any kind of hadron, in the specific ...
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Why does it take less binding force to hold the two atoms that a uranium atom has split into?

When a Uranium atom splits into two there is a little bit of mass left that is equivalent to a big amount of energy (e=mc^2) and it explodes in fission It takes less binding force to keep the two ...
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Creating isotopes by shooting neutrons into an unstable nucleus [closed]

I've been doing a lot of amateur research lately (youtube videos) on particle physics and find it all really interesting. I'm also a crazy alien conspiracy theorist who believes in the whole "Bob ...
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Do all binding energies work like the exchanging force of photons but just in different strengths? [closed]

Do all Binding Energies use the same force but in different strengths?
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What is meant with an $X$ in the particle data booklet?

What is meant with the $X$ in some decay channel of the $B^0$ ? B⁰ PDG Booklet I imagine it could be an unidentified resonance, but I cannot find a definition. What especially confuses me is that ...
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Nuclear stability [duplicate]

Why does increasing the number of neutrons in a nucleus make it more unstable? I know that adding more protons increases electrostatic repulsion, therefore the nucleus is more unstable, but as ...
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If colour charge is like electric charge how do baryons hold together when all the colour charges have the same sign?

So a quark and an antiquark in a meson have colour charges of the same colour but opposite sign eg $r \bar{r}$, so I think this is like an electric charge with a positive and negative particle so ...
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Strong force gets weaker at small distances yet approximated by -1/r potential

My particle physics textbook (by Martin and Shaw) has confused me, it states in ch.7 that the strong force gets weaker at small distances, and that it can be approximated by $V(r) = -\frac{4 \alpha_s}{...
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Can a nucleus (made of neutrons) exist without an EM field?

I understand that the EM field has an EM charge and that a nucleus made of neutrons and protons has an opposite EM charge, and this attracts. And because the electron's kinetic energy (that would ...
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Variable number of virtual particles inside neutron (relative to observer's speed)

I have read somewhere (sorry I do not know where) that the number of virtual particles in a neutron is variable depending on the speed of the observer (relative to the neutron). I understand that the ...
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What keeps quarks separate (strong force pulls, but what repels to equal out)

We know that the strong force keeps quarks together, that is mediated by gluons (and their charge is called color charge). We know that the residual strong force keeps neutrons and protons together in ...
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How does mass of the exchange particles affect the range of a force? [duplicate]

I read an article asserting that nuclear force is a short range force because of gluon's mass, and EM force is a long range force because photons massless. I also want to know, why quantum ...
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What is the force carrier for neutrons in fission?

Say I have a neutron capture event, leading to a fission reaction in which a few neutrons are expelled. These neutrons inherit a certain momentum from this fission reaction. How do these neutrons ...
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What is the difference between a deuterium nucleus and a sexaquark?

Assume a sexaquark contains 3 up and 3 down quarks. What is the difference between this and a deuterium nucleus containing a proton bound to a neutron? Is there any difference?
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Inverse square rule for strong forces

Most of the forces induced by a point particle follows the $1/r^2$ rule. Then why does the strong force not obey it?
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No need for Strong force

As 3 quarks stay inside of proton, where down quark just opposite charge of up quarks then what would happen if I say both of them are attached by their own electromagnetic force instead of strong ...
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How would an interaction with a single charge, and a charged weightless carrying particle behave?

We learnt about, among the other three fundamental interactions, the strong interaction. The particles that are affected by it are those with color-charge. It's carrying particles, gluons, have a ...
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Error estimation of $\alpha_s$

I have calculated the strong coupling constant $\alpha_s$ using and approximate solution of the Renormalization Group Equation $$\mu_R^2\frac{d\alpha_s}{d\mu_R^2}=-(b_0 \alpha_s^2 + b_1\alpha_s^3 + ...
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Question about the vacua of the Standard Model

This question is probably based on a misunderstanding. Please correct me if I'm wrong, and if unclear, I'll try to put it in a clearer language. In Yang-Mills theory such as the theory of strong ...
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Anti-quark transformation

The center of $SU(3)$ is $Z_3$. So a quark transforms under an element $z\in Z_3$ in this center as $q\to q'=z q$. How do I figure out how the anti-quark $\bar q$ under this center? How about the ...
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What if we had a universe that contained only two particles held together by the strong force? [closed]

What if we had a universe that contained only two particles held together by the strong force? What would be the behavior of the particles if the strong force suddenly vanished?