Questions tagged [large-hadron-collider]
World's largest particle accelerator built by the CERN (European Organization for Nuclear Research) near the Franco-Swiss frontier near Geneva, Switzerland. It is designed to collide beams of protons with a centre of mass energy of up to 14 TeV. It contains the important detectors ALICE, ATLAS, CMS and LHCb.
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how to make a collider high luminosity?
Exactly what procedures are followed to increase the luminosity of a particle collider? Say when LHC increases its luminosity, does it increase the number of protons per bunch? If yes, then how?
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Is proton decay considered in neutron star models (and LHC)?
Although it is definitely not simple, there are many reasons to consider that baryon number can be violated, for example:
during baryogenesis (just after Big Bang) there was created more matter than ...
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Identifying the Higgs boson at LHC
In quest of confirming Higgs boson's existence, particle collisions were observed at the Large Hadron Collider. Scientists had to distinguish the observation of the background noise/fluctuation and ...
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Results of photon-photon collisions at LHC?
I recently read that CERN planned on performing photon/photon collisions in 2015. I can't seem to find the results. I'm not a scientist so not too familiar with finding CERN documentation.
Any ...
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Verifying the consistency of a quantum field theoretic cross-section formula
Consider the scattering $$e^-e^-\rightarrow e^-e^-$$ in QED. The cross-section is a Lorentz invariant quantity and therefore, given by $$\sigma=\sigma(m_e,e,s,\theta)$$ where electron mass $m_e$, ...
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Pile-up in LHC collisions and number of signal events
When counting the number of accepted events in a collider experiment, what is the effect of not considering the pile-up effect in e.g. proton-proton collisions at the LHC?
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What generates the current that then is made to flow in superconductors at CERN?
At CERN for example, what is actually providing the current? It cannot be a battery because when the load resistance is less that the internal resistance then the load sees no voltage...
So do they ...
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Could circular particle accelerators create spin?
How do we know that the process of accelerating a particle in a circle at a circular collider (such as the LHC) doesn't create particle spin?
If it does, then how do we know that a particle's ...
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What news about the second Higgs mode (or the mysterious particle) is anticipated to be seen at LHC around 750 GeV?
A few months ago, there were press releases about a possible second Higgs mode unveiled by LHC experiments. Or perhaps a new particle even more surprising like a graviton ... There was no certainty ...
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Problem About Calculation of double Higgs production Cross Section (for gluon fusion) with FeynArts+FormCalc
I want to mention about my problem about FeynArts/FormCalc.I have tried to calculate LHC cross section for "gluon gluon -> H H" process at Standard Model. However, my result XS is quite different from ...
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Is it possible to produce classical black holes in high energy collisions?
According to the Hoop Conjecture, if one can pack a sufficient amount of energy in a small enough region, black holes can be formed. The work on gravitational interaction between high energy particles ...
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LHC particle combinations and colliding neutral particles
In high-energy particle accelerators, we have limited possibilities for what kinds of particles we can collide due to their charge, radiation properties etc. I understand that in LHC we collide high-...
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Is there an upper-limit for sparticle masses?
I realize there are many flavors to supersymmetry theory but can the LHC reach the energy and luminosity levels past which if sparticles are not detected then supersymmetry can definitively be ruled ...
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Why was an 8 TeV collider needed to find a 125 GeV Higgs? [duplicate]
This might be very naive, but why wouldn't a (say) 209 GeV LEP do the job?
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How far are we from reaching around $10^{16}~\rm GeV$ collisions experimentally?
I understand this is a highly speculative question, so I'm not expecting final words, but rather insights to deepen my notion on the issue. I know we reached about 209GeV at LEP in the end of 2000, ...
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For how long will we be able to increase the power of the LHC? [closed]
And what can we do to make new discoveries in the fundamental(particle) physics if the LHC doesn't bring results?
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Will FAIR be able to reach the quark-gluon plasma phase transition?
At low temperature and baryonic density quarks and gluons are confined in hadrons. Most physicists believe that the phase transition between hadron and the quark-gluon plasma has been reached at LHC ...
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On the mass of the Higgs Boson
Thomson, in Modern Particle Physics, chapter 17, says
The SM Higgs boson H is a neutral scalar particle. Its mass is a free parameter of the SM that is given by $m_H=2\lambda v^2.$
In the next ...
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question about other dimensions
The Big Bounce theory says that before the Big Bang there were other Big Bangs over and over. For example, the universe would have a Big Bang within it and then this new mini-universe would expand, ...
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How does the Higgs boson work? [duplicate]
How does the Higgs boson give properties to matter such as mass?
I understand that the Higgs boson is one of the subatomic particles that gives matter its properties, but how?
Thanks
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How does the LHC explore extra dimensions?
The Large Hadron Collider (LHC) has been smashing particles for a long time and sometimes people say that it has found new dimensions. How is it even possible for a particle accelerator to find new ...
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LHC: Clumps of protons or continuous stream?
I am curious about the Large Hadron Collider and whether the proton (anti-) beams are clumps of protons (grouped together) or are they roughly equally distributed around the circumference of the ring.
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Estimated total number of Higgs events
How many Higgs events have been observed at the LHC?
I understand that this is not terribly well defined question; I'm just after an order of magnitude estimate for the excess events in, let's say, ...
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What's the recent released 750GeV particle's spin?
I was told that it has recently been confirmed to be spin-2 particle, and potentially to be graviton. I'm pretty interested in how this has been examined.
Edit:
During the Moriond 2016 conference, ...
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How correlated are the statistical significances of the same signal/non-signal for CMS and ATLAS?
Consider a diphoton excess for both ATLAS and CMS at the same energy for two cases:
false signal: I'd expect the two statistical significances to be
uncorrelated
true signal: I'd expect the two ...
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How does the "Look Else Where Effect" affect the chances of detecting a false diphoton excess at the LHC?
Back in December 2015, there was found a 750 GeV diphoton excess in both CMS and ATLAS at the same location with a significance well above $3\sigma$; a 0.13% chance of being false.
However, there ...
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Branching ratio for a bound state
Consider the meson $\Upsilon(10860)$. It decays into $B\bar{B}$, $B\bar{B}^*+cc$ and $B^*\bar{B}^*$. The mass of $B$ is $5.28 ~\textrm{ GeV}$ and mass of $B^*$ is $5.33~\textrm{ GeV}$. The branching ...
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High $p_T$ and high $Q^2$ in deep inelastic hadronic collisions
When reading about high energy collisions (for example proton-proton collisions at LHC), I always find the relation $Q\sim p_T$, which, for me, is hard to demonstrate. Moreover, I found statements ...
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How are the standard model and the Higgs boson actually confirmed experimentally in practice?
This is my mental picture on how we can make predictions from a theory (I'm not a physicist so this might be quite wrong) :
Typically, we solve a partial differential equation (analytically if we can,...
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Can we observe solar p-p fusion reaction somehow on Earth?
What are the properties of proton+proton fusion reaction
$p + p → 2H + e^+ + ν_e + 0.42 MeV$
making it hard to replicate on Earth?
If we aim beam of protons to a can of water, won't we observe ...
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Why does LIGO do blind data injections but not the LHC?
The LIGO group has a team that periodically produces fake data indicating a possible gravitational wave without informing the analysts. A friend of mine who works on LHC data analysis told me that ...
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Why is the tunnel cold in LHC?
Particle accelerators such as the LHC work by accelerating electrons
or protons close to the speed of light in opposing directions through
an incredibly cold tunnel, until they eventually smash ...
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$e^+e^-\to q\bar{q}$: Reconstructing $q\bar{q}$ energy and momentum
Question
In a real collider experiment e.g. LHC / LEP how can one reconstruct the energy and momentum of the resultant $q\bar{q}$ pair produced from the process $e^+e^-\to q\bar{q}$?
Specifically, ...
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How come two protons create top-antitop quark pair? (A question regarding CERN courier May 2016)
I am not very well versed in particle physics lingo but as much as I know $p$ stands for proton and $t$ stands for top-quark. Then, how could this be possible?
I hope I am wrong about what is written ...
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Explanation of graphs from CERN [closed]
I have a few questions about these kinds of graphs
What is the name of this type of graph?
What does the width of the peak mean?
If the points are data points, how was the curve created/predicted?
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How do I calculate the differential cross section with respect to the transversal momentum?
First of all, sorry for my English, my first language is German.
My problem is: I calculated the matrix element of the quark-gluon-Compton process (q+g -> gamma + q). With the kinematics of ...
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How can an electron fake a jet?
This is a question for experimentalists. I have seen in several ATLAS papers (see for example chapter 4 in arXiv:1602.09058, 6th paragraph), that after objects have been correctly identified, any jet ...
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Why did it take so long to find the Higgs?
The $W$ and $Z$ boson took a long time to be discovered because they were so heavy; we couldn't produce them in a particle collider until the 80's. But the Higgs boson isn't that much heavier than the ...
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In the LHC, how is the proton separated from the electron in the hydrogen? [duplicate]
I know that we use protons in the LHC. So my question is, how is the proton separated from the electron in the hydrogen?
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Why do Higgs decays depend on the production method?
I'm reading about Higgs phenomenology and I have come across the following table.
I don't see why gluon fusion to $b \bar{b}$ is considered to be "impossible" in this table.
As far as I can tell, ...
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How does a Collider work? [closed]
How does a collider work, explained using various Physics theories (or if there is a main one) . How does the acceleration play a part in the individual sub-atomic kinetic levels. What happens when ...
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Effective collision energy at LHC
The proton is not a fundamental particle, so in high energy proton-proton collision we actually collide proton's sub-constituents: quark-quark and (mostly) gluon-gluon. LHC operates now at 13 TeV ...
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Why is 7 TeV considered as a big amount of energy?
Considering that $7$ TeV is more or less the same kinetic energy as a mosquito flying, why is it considered to be a great amount of energy at the LHC?
I mean, a giant particle accelerator that can ...
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How the LHC bump can be a mere coincidence?
Speaking of http://www.nature.com/news/lhc-sees-hint-of-boson-heavier-than-higgs-1.19036.
I understand that such a bump can be a statistical fluctuation.
What troubles me is that the bump has been ...
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How are the protons for collisions in the LHC made?
I heard that the LHC smashes two protons together to research the universe.
But how does it create the protons for collision? If we strip off the electrons won't there be neutrons along with protons?
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Could the Large Hadron Collider accelerate one kilogram of protons at once?
Is it possible to accelerate a very large number of protons in a particle accelerator as opposed to only a few as is regularly done? What's to keep someone from accidentally dumping too many particles ...
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Where all those particles come from - proton proton collision
I was reading an article about the "Higgs factory" China is planning to build and it got me thinking about what happens when two protons collide.
I am an engineer so I have a good understanding of ...
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Head on collision of two black holes
LHC was built to collide two atomic particles to study contents within them. There are millions and billions of black holes present throughout galaxies. As collision between the galaxies is common in ...
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The use of electrons in synchrotrons
I'm researching synchrotrons for a class project, but I can't seem to find a decent answer to one of my questions. It appears that most synchrotrons use electrons as opposed to some other charged ...
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How are the two proton beams at the LHC accelerated in opposite directions?
At the Large Hadron Collider (LHC), how are the protons in the two beams accelerated in opposite directions?
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