203 votes
Accepted

Why isn’t CERN afraid of a fusion reaction in the LHC?

Proton-proton fusion happens at energies around 15 keV. The LHC currently operates at an energy of 13 TeV, which is literally one billion times larger. Fusion is one of the lowest-energy processes ...
probably_someone's user avatar
102 votes
Accepted

How do we know the LHC results are robust?

That's a really great question. The 'replication crisis' is that many effects in social sciences (and, although to a lesser extent, other scientific fields) couldn't be reproduced. There are many ...
innisfree's user avatar
  • 15.1k
100 votes
Accepted

Will the Large Hadron Collider "explode" if the power is turned up too high?

In the case of the LHC, yes the beam can do quite a lot of damage. At full power there is something like 350MJ stored in the beam - close to a freight train, or roughly the kinetic energy of a full ...
Martin Beckett's user avatar
61 votes
Accepted

What does CERN do with its electrons?

You're right that CERN gets its protons by ionizing matter and collecting them. But the number of electrons & protons CERN deals with is far smaller than you might think. They get about 600 ...
user1504's user avatar
  • 16.4k
59 votes
Accepted

Why does LIGO do blind data injections but not the LHC?

After they told me about their impressive "LHC Olympics" in which physicists (often hardcore theorists) were reverse engineering a particle physics model from the raw (but fake) LHC data, I proposed ...
Luboš Motl's user avatar
42 votes
Accepted

Why can't the LHC detect heavy particles?

It's not detecting the particles that is hard, it's making them in the collisions. Although the LHC collision energy is 14TeV, collisions aren't between the protons but rather between individual ...
John Rennie's user avatar
38 votes

Why does LIGO do blind data injections but not the LHC?

Let me first mention that the LHC is in a way a text book experiment: you have a very good control over the experimental conditions and you can repeat your experiment as often as you like. You have, ...
Martin's user avatar
  • 15.6k
36 votes

What news about the second Higgs mode (or the mysterious particle) is anticipated to be seen at LHC around 750 GeV?

One of the searches performed at the LHC consists in selecting events in which two high energy photons are produced ($\gamma\gamma$ channel) and in computing their invariant mass - the energy of the ...
Lucas Gautheron's user avatar
30 votes

What is an LHC Fill?

A single LHC fill has roughly the following steps: A dose of protons enters the accelerator complex Protons are accelerated through the chain (Linac, PSB, PS, SPS, LHC) to the maximum energy Protons ...
mpv's user avatar
  • 5,220
26 votes
Accepted

Why is Higgs particle detected much later than top quark when it's lighter?

With both particles you cannot detect them within their own lifetimes, only look at what they decay into. The top decays to a b jet and W (which can then become fermion anti-fermion or leptons) and is ...
Lio Elbammalf's user avatar
25 votes
Accepted

What are "large hadrons"? Are there also "small hadrons"?

The article is either a joke or a gross misinterpretation of the name “Large Hadron Collider”. The name refers to the physical size of the device. It is a “large” hadron collider, not a “large hadron” ...
Riley Scott Jacob's user avatar
24 votes
Accepted

Why did it take so long to find the Higgs?

Electroweak theory told us where to look for the $W$ and $Z$ gauge bosons. For the Higgs, its mass is a free parameter, hence we didn't know where to look for it. Once you start to look in many places ...
pfnuesel's user avatar
  • 1,978
21 votes
Accepted

How can an electron fake a jet?

Hadronic jets deposit a significant fraction of their energy in the electromagnetic calorimeter, for example because they can contain neutral pions that decay as $\pi^0\to\gamma\gamma$, bottom/charm ...
atlas-insider's user avatar
20 votes
Accepted

How does the LHC explore extra dimensions?

First, no evidence for other dimensions has been found. However, there are ways for particle colliders to detect other dimensions. One of the main ones is to see if any energy "disappears" under ...
auden's user avatar
  • 7,037
20 votes

How can an electron fake a jet?

Those of us who've worked at JLAB (and those who worked at SLAC) know that energetic electrons create a lot of hadronic junk when incident on significant amounts of matter. Think about Deep Inelastic ...
dmckee --- ex-moderator kitten's user avatar
20 votes

Will the Large Hadron Collider "explode" if the power is turned up too high?

The only thing that could explode are the magnets. As mentioned by Countto10, there is a huge amount of energy stored in these magnets. Superconducting magnets are used, they are cooled using liquid ...
Count Iblis's user avatar
  • 10.1k
14 votes

Will the Large Hadron Collider "explode" if the power is turned up too high?

If the power output of the Large Hadron Collider were infinite [...] would it eventually "explode" if the power is turned up too high? Yes - any hypothetical object capable of producing infinite ...
tparker's user avatar
  • 47.5k
14 votes
Accepted

Hard particles and soft particles

It is a sloppy usage, hard particles are the ones coming from "hard scattering", i.e. deep inelastic scattering, and are particles with a lot of energy. Soft particles are the ones with low energy and ...
anna v's user avatar
  • 234k
14 votes

How do we know the LHC results are robust?

In addition to innisfree's excellent list, there's another fundamental difference between modern physics experiments and human-based experiments: While the latter tend to be exploratory, physics ...
chrylis -cautiouslyoptimistic-'s user avatar
14 votes

Why isn’t CERN afraid of a fusion reaction in the LHC?

As pointed out in the comments, the energy in the LHC is very high. High enough that the interactions are with partons inside the proton, where a parton is any one of the 3 valence quarks (u, u, d), ...
JEB's user avatar
  • 33.6k
14 votes
Accepted

Why don't they use electrons at CERN?

The choice of particles for a collider depends on what needs to be clarified next in the zoo of particle physics and the theory of the Standard model, and also depends on the difficulties introduced ...
anna v's user avatar
  • 234k
14 votes

How does a booster work in a particle accelerator like the LHC?

The proton synchrotron booster is not a simple circular ring: The Proton Synchrotron Booster is made up of four superimposed synchrotron rings that receive beams of negative hydrogen ions (H-, ...
anna v's user avatar
  • 234k
13 votes

What if particle colliders cannot find anything beyond the standard model?

We will do what is always done in science (when we come up short). We will look for new approaches. There are, perhaps, other ways to understand the fundamental particles/interactions of nature ...
JRL's user avatar
  • 778
12 votes

Why does LIGO do blind data injections but not the LHC?

Fake event injection is only one of several schemes for "blind" analysis. Other blinding schemes involve manipulating some parameter of the data as show to the analysis team by a reversible ...
dmckee --- ex-moderator kitten's user avatar
12 votes

Hard particles and soft particles

It's a shorthand for describing the particle's kinetic energy, by anticipating the sorts of collisions that a particle will produce. More energetic particles will "hit harder" and less energetic ...
rob's user avatar
  • 89.7k
12 votes

Why can't the LHC detect heavy particles?

As a consequence of $E=mc^2$, to create a heavy particle (i.e. large $m$) requires a large amount of energy ($E$). Since the LHC only generates a finite amount of energy in the collisions, there may ...
lemon's user avatar
  • 13.2k
12 votes

Why isn’t CERN afraid of a fusion reaction in the LHC?

A simple experimental fact about the LHC is that all reactions of protons on protons happen in vacuum. As the other answers explain, the energy in the beams is too high to allow the two protons to ...
anna v's user avatar
  • 234k
12 votes

What does CERN do with its electrons?

The usual thing for a shutdown is to 1) stop injecting fresh particles into the beam tube, and 2) deflect any remaining particles in the main tube and any storage rings into a beam dump which is a ...
niels nielsen's user avatar
11 votes

Why does LIGO do blind data injections but not the LHC?

The LIGO experiment consists of detecting individual events with a characteristic form that take place in less than a second. Given the high stakes and that conceivably, only one or a few events might ...
ProfRob's user avatar
  • 131k

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