58
votes
2answers
10k views

Why doesn't matter pass right through other matter if atoms are 99.999% empty space?

The ghostly passage of one body through another is obviously out of the question if the continuum assumption were valid, but we know that at the micro, nano, pico levels (and beyond) this is not even ...
1
vote
1answer
32 views

Regarding luminosity monitor of particle collider

I am sorry if my question is completely wrong or foolish I would feel glad to be corrected On the wiki page for Bhabha Scattering, it is mentioned that it is used as luminosity monitor in many ...
0
votes
2answers
28 views

Capturing Energy from a Positron-Electron Collision

According to the book Physics of the Impossible, the catastrophic collision between a electron and a positron yields an output of 1.02 MeV. Assuming you have an isotope like $^{22}\text{Na}$, which is ...
3
votes
0answers
125 views

Baryonic density in collision experiments

Does anyone know any way of estimating the net baryon density in collision experiments, e.g. in LHC, RHIC, or the upcoming ones at GSI-FAIR? I have comes across many hand-waving arguments, sample - ...
2
votes
1answer
56 views

Advantages of $e^-e^-$ or $e^+e^+$ collisions over $e^+e^-$ collisions?

Is there any (interesting) HEP process whose study would take advantage from $e^-e^-$ or $e^+e^+$ collisions with respect to $e^+e^-$ collisions?
6
votes
2answers
184 views

How do collisions of fundamental particles produce different fundamental particles?

When considering fundamental particles as waves in fields, it seems like any collision of two particles of some fundamental type could only create energy within that type's field. Why do we expect ...
1
vote
1answer
157 views

Electron and photon collision

So electron moving left ($v_{initial}=0.8c$) collides into photon going right. After the collision electron is moving to right ($v_{after}=0.6c$) and the photon is moving to left. What is the ...
0
votes
1answer
55 views

absorption length of thermal neutrons in a medium

My book states that $$N(x)=N_0\cdot e^{n\cdot \sigma \cdot x}$$ for $n$ absorbing particles per volume element with a cross section $\sigma$. Can somebody explain where this comes from?
0
votes
1answer
173 views

Do particles ever touch each other during a collision? [duplicate]

Do particles ever touch each other during a collision? My understanding is that they can get really close to each other but never actually touch, is that true? Another thing I've read about is, the ...
1
vote
1answer
113 views

How can one calculate the gamma-ray energy spectrum for proton-proton collisions?

How does one calculate the the energy spectrum of gamma-rays produced by a proton-proton collision? I'm at a complete loss.
1
vote
1answer
196 views

Centrality and collision parameter b

Can someone tell me what does it 20-30% collision centrality mean in terms of impact parameter b?
1
vote
1answer
41 views

Lifetime of Positron and its existence

Since we know in condensed matter the lifetime of positron is about 10^-10 seconds, how do we collide positrons with electrons? How many positrons were there during the LEP experiment? I know ...
1
vote
1answer
84 views

Asteroid collision debris calculation

I wonder how to determine the directions, in which the collision debris is launched when 2 asteroids collide. I am aware of: m1*v1 + m2*v2 = m*v = m3*v3 + m4*v4 + m5*v5 + ... and this works just fine ...
0
votes
1answer
137 views

Elastic collision of photon [closed]

Consider an elastic collision of a photon with 100 eV energy hitting a mirror. How much momentum is exchanged in the collision? Also, can one model the reflection of an elastically colliding photon ...
1
vote
1answer
124 views

What would be the result of the collision of two down quarks?

Even if we can't have single quarks in nature because of the charge colour, what would be the result of the collision of two down quarks at high velocities (0,99% c) at high energies, like the ones of ...
2
votes
2answers
229 views

Matter and anti-matter collision energy problem

From Beyond Einstein, by Michio Kaku and Jennifer Thompson, Chapter 13, Antimatter : Dirac, also focused on the fact that Einstein's equation $E=mc^2$ wasn't totally true. (Einstein was aware that ...
11
votes
2answers
2k views

What happens in electron-electron collisions?

What are the results of high energy electron electron collisions? Are other particles created?
1
vote
0answers
100 views

Matrix element approximation

In the formula for the decay width of $\Upsilon(4S)$ to B-mesons from $\text{e}^+\text{e}^-$ collisions: $$\Gamma_{\Upsilon(4S)\to B\bar{B}}=\frac{\left|\underline{P}_B \right|}{8\pi ...
0
votes
2answers
83 views

Minimum $E$ of $p\bar{p}$-collision for $q\bar{q}$ pair with mass $m_q$

I am currently working out the energy required to create a particle anti-particle pair from a collision of a proton travelling along the x-direction with an anti-proton which is at rest. The particle ...
15
votes
6answers
2k views

What would happen if Large Hadron Collider would collide electrons?

After some reading about the Large Hadron Collider and it's very impressive instruments to detect and investigate the collision results, there is a remaining question. What would happen if the ...
4
votes
1answer
802 views

Advantages of high-energy heavy-ion collisions over proton-proton collisions?

Some high-energy experiments (RHIC, LHC) use ion-ion collisions instead of proton-proton collisions. Although the total center-of-mass energy is indeed higher than p-p collisions, it might happen that ...