Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales.

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80 views

Is there a $\mathrm{p}^0$ particle?

In the following equation of a reaction $$\mathrm{p}^0 + \mathrm{n} \to \mathrm{K}^+ + \Sigma^-$$ What is the quark composition of the $\mathrm{p}^0$ particle? Or is it supposed to be $\rho^0$? ...
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58 views

Can a magnetic or electric field deflect subatomic particles?

I always wondered if the subatomic particles can be deflected by a magnetic or electric field. Basically I am asking the viability of the typical "Force Field" in movies.
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1answer
24 views

How the number of binary collisions increases with centrality faster than the number of participant in heavy ion collisions?

How the number of binary collisions increases with centrality faster than the number of participant in heavy ion collisions at different particle colliders?
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28 views

quantum two particle system? [duplicate]

according to wiki if you have two different particle with state vectors |1> and |2> respectively than the state vectors of the combined system is the tensor product denoted: |1>|2> but if the two ...
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1answer
145 views

Understanding Kaon Mixing

While studying Neutral-Kaon mixing, I learnt that the way we observe them is through their decays to Pions. But the states that decay are not the particles/antiparticles themselves but their mixture. ...
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2answers
1k views

How does a neutron have more mass than a hydrogen atom's isotope (Specifically deuterium)? [closed]

A hydrogen atom weighs 1.00794 u ± 0.00001 u. The mass of a neutron is slightly above it, at 1.00866491600(43) u‎. I'm wondering, how does a neutron weigh more than itself plus 2 extra particles, as ...
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80 views

What is Quantum fluctuation, and does it break law of conservation of energy?

Please explain what is quantum fluctuation as simple as possible and (according to Wikipedia) how could it break law of conservation of energy ? Wikipedia quote: That means that conservation of ...
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35 views

How does positronium work?

I've heard that in positronium, electrons and positrons orbit each other before annihilating one another shortly after. However, I thought that electrons never orbit anything, but instead have a ...
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21 views

What is Colour-Colour-Intensity Diagram?

What are color-color intensity diagrams? These are 3D plots usually used in high energy astrophysics ( particularly in relation to XRBs).
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156 views

Scattering, Perturbation and asymptotic states in LSZ reduction formula

I was following Schwarz's book on quantum field theory. There he defines the asymptotic momentum eigenstates $|i\rangle\equiv |k_1 k_2\rangle$ and $|f\rangle\equiv |k_3 k_4\rangle$ in the S-matrix ...
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3answers
177 views

What happens to a particle and antiparticle that collide?

Matter can never be destroyed, so what happens to those particles? Do they just disappear? Where does the mass go?
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73 views

complicated QCD Color factor formula?

I was doing higher order calculations for purely gluonic system and came across complicated color factors like the product of six structure constants product ...
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64 views

Application of CPT invariance : some trivial algebra

I am having some problem in understanding one step in the following algebra. Consider an interaction where initial state is defined as $ \left|i\right> $ and final state by $ \left|f\right> ...
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43 views

Characteristic Ka X-rays [closed]

In an experiment one observes the characteristic Ka X-rays of two elements at energies of 6.930 and 7.478 eV. The higher energy line is due to Ni. What element is responsible for the lower energy ...
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1answer
34 views

The elementary particles uniformity and its limits in the context of matter [closed]

We know that matter particles are uniform, i.e. they are absolutely identical (1, 2, 3). Particles of various properties are uniform. But if we look at bigger matter elements, when and how does the ...
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1answer
34 views

Particle-antiparticle behaviour

I am trying to understand several particle-antiparticle concepts and there are questions that are not answered in any literature: Hawking's radiation: what happens if classic particle of ...
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1answer
109 views

Does the neutrino have charge? Obviously not!

I was recently reading "Particle Physics: A Very Short Introduction" by Oxford University Press, and in it (I haven't finished it yet though) he says, "The weak force changes one variety of ...
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0answers
37 views

Is there an orbit decay associated with synchrotron radiation of a relativistic particle?

I had a question about a particle (say a proton) with relativistic energies interacts with a magnetic field (in the z direction). As it is accelerates the particle emits synchrotron radiation. ...
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1answer
77 views

Invariant mass spectrum to a transverse momentum distribution

For the decay of the Higgs boson in 2 photons having the following invariant mass formula: $$M = 2E_{1}E_{2}(1 - \cos \theta)$$ How can I go from an invariant mass spectrum distribution to a ...
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31 views

How to explain binding energy of electron in Geant4 particle transport code?

The question is related to binding energy of electrons in oxygen atom. First I will put the question and later explain how did I came across it. ========= The question =============== In the ...
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48 views

Condition for CP violation

I am studying how weak and strong phases lead to CP violation. I am following CP Violation by Branco. There is some algebra that I can not follow. Consider the process : $ a + \bar{a} \rightarrow b ...
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1answer
71 views

how do electrons in 2 separate atoms change its energy level when atoms come close together to form molecule?

The question is just as the title. It's said that electron must receive a specific amount of energy in order to go or drop to another energy level. So how can electrons of separate atoms which have ...
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7answers
2k views

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles?

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles? It would appear to a layman such as myself that these ...
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1answer
68 views

The parity of a pair of electrons

In the page 254 of Scrednicki's QFT book, it states that a pair of electrons also has negative intrinsic parity. But I think the parity of two identical particles must be one. Can someone please ...
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123 views

Did the initiation of the Higgs Field and the inflationary period occur simultaneously?

My question is: Both of these concepts involve a phase transition and they both started, as far as I know, early in time, so are the above two ideas linked in any way? My first source for this query ...
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Why spurious pulses are likely in partial discharges?

My notes The gas multiplication in the proportional counters is based on the secondary ionization created in collisions between electrons and neutral gas molecules, resulting in some visible ...
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2answers
718 views

Quarks in a hadron- where does the mass come from

We know that the sum of the masses of the quarks in a proton is approximately $30~\text{MeV}/c^2$, whereas the mass of a proton is $931~\text{MeV}/c^2$. This extra mass is attributed to the kinetic ...
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41 views

Where does the North Pole of a magnet originate?

My teachers have told me that magnetism occurs when spin, or magnetic moments of each atom in the substance align up, which creates an overall force. This would mean each atom is acting like a ...
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36 views

stable particles in the W, Z infinite mass limit

Which particles do become stable, or increase notably its lifetime, when weak interactions are switched off? Pretty sure neutron does, and charged pions surely too, and I'd guess all the particles ...
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1answer
70 views

Regarding parity conservation in the decay $\omega \to \pi^0 \,\pi^+\, \pi^-$

I'm somewhat confused by this decay. Associated vertex seem to be related to QCD residual terms contributing to the nuclear force, therefore they should manifest conservation of Isospin and Parity. ...
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32 views

C, P and T for Klein-Gordon Field

Taking transformation of Klein-gordon field under C, P and T as $$\phi_{p}(t,r)= \exp(i \alpha_{p}) \phi (t,-r)\ ,$$ $$\phi_{c}(t,r)= \exp(i \alpha_{c}) \phi^\dagger (t,r)\ ,$$ $$ \phi_{T}(t,r)= ...
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1answer
46 views

Precise definition of Jet Energy Scale and Jet Energy Resolution

I've been struggling to get the precise meaning of these two quantities, is it correct to say that the first one is only related to Montecarlo simulations? I can't seem to find a pedagogical ...
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2answers
140 views

What is Size of Photon?

Is there any size of photon if so what is it? And also which particle had smallest size / radius / volume considering all of the matter.
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2answers
47 views

Advantage of using higher luminosity accelerator

If two accelerators operate at the same energy but different luminosity, is the only advantage of accelerator with a higher luminosity that there will be more events in a given amount of time, thus it ...
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1answer
75 views

Does the charge of an atom or molecule change after absorbing a photon

I know atoms or molecules will absorb a photon of the right frequency but will this change the charge. If you have a neutral molecule once it absorbs a photon will the charge change to a positive or ...
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53 views

Quantum Flavordynamics and messenger particles

My question is about messenger particles and how they relate to the concept of flavordynamics. I know that messenger particles travel between other particles to "communicate the force" like a photon ...
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1answer
30 views

What exactly is measured in a e.g. hadronic calorimeter - momentum or energy of a particle?

I got a little puzzled with the concept of hadronic/electromagnetic calorimeter. Do they measure the energy of the particle e.g. an electron, like the first entry of the four-momentum, or the ...
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1answer
95 views

What is horizontal about a horizontal symmetry?

When studying a seminal paper in flavor physics by Yossi Nir and company, Mass Matrix Models (released in 1992), I came across the term, a horizontal symmetry (after seeing this I did a lot of ...
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1answer
33 views

Plasma field particle accelerators [closed]

I was discussing about particle accelerators with my friends and it came to my mind whether it is anyway possible to make a table-top accelerator(accelerator that can fit on a table). I asked this to ...
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0answers
41 views

Recommendations for Introduction to Quantum Flavourdynamics

It's surprisingly hard to find any resources on this on the internet. I'd want a suitable for self-study introduction to the QFD for someone with only a basic understanding of Quantum Field Theory. ...
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1answer
58 views

Length of time interval for an atom in excited state to drop to lower energy level [duplicate]

This is either a basic question or one that doesn't make any sense, but here goes. If I have an atom in an excited state (1st energy level or 2nd or more), how long does it take to drop to a lower ...
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2answers
99 views

How do metals transfer positive charge if the protons are immobile?

From my textbook:` "When you touch a positively charged object charge spreads over your body." My understanding is that the protons in a solid conductor are immobile since they are contained within ...
4
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2answers
719 views

What is going on in the photon-photon scattering Feynman diagram?

I understand the basic concepts of a Feynman diagram, but I don't get what is going on here. I have named the photons ABCD and the fermions 1234 for clarity. I'm going to assume that the vertical ...
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4answers
140 views

Can a positron decay without encountering an electron?

All the decays I read about involve electron - positron annihilation.
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1answer
157 views

What is the intuitive meaning of $Q^2$?

In particle physics, $-Q^2$ is defined by the four momentum transfer squared: $$Q^2 = -(p_i - p_f)^2 = (\vec{p}_i-\vec{p}_f)^2-(E_i-E_f)^2$$ For elastic scattering, the meaning of $Q^2$ is clear - it ...
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53 views

Confusion regarding interpretation of a diffusion related PDE?

So I was reading Keller & Segel paper related to mathematical model of cellular aggregation in slime molds. In the model (considering 2D assumption) we have an equation like below: ...
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67 views

Intrinsic parity

When we apply parity on a field two times, we demand that we should get back the same field. This gives us, $P^{2} =1$, which implies, $ P \psi = e^{i \theta} \psi$ . This extra phase factor is ...
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1answer
60 views

What do elements of CKM matrix imply?

In CKM matrix, there are 9 elements, e.g. Vud = .974, Vus = .227 ,Vub = .004. The sum of these 3 elements is greater than one, so they cannot represent the probability of an up quark to transform in ...
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58 views

What is the value of coupling constant at electroweak unification?

The value of running coupling constant is (1/24) at grand unification energy,where strong, weak & electromagnetic forces are unified and in a graph between running coupling constants vs ...
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How to obtain a lower mass bound for a unstable (or stable) particle from Poisson statistics?

Imagine you have a particle (stable e.g. if some R-symmetry or similar does exits) heavy or not so heavy... Question: how to guess a lower (upper bound as well) with the aid of Poisson statistics, ...