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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Why on the ATLAS Higgs discovery paper there are uncertanties on the expected cross section upper limits but not on the observed upper limits?
I was reading the ATLAS paper on the Higgs discovery and a question came to my mind. In the plot I attached, there are uncertainty bands on the background only hypothesis upper limits, and not on the ...
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Why can't we slap a proton for instead of using particle accelerators?
Very stupid question, but since the mass of a hand is very large compared to a proton, one should be able using a solid slap to accelerate a proton to ultra-relativistic speeds. If I consider a ...
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How do particle accelerators like the LHC bend beams of particles?
I know they use dipole magnets to curve the beams, and quadrupoles to focus them, but how do they know how powerful the magnets need to be so they bend the beams sufficiently but not too much so that ...
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Elementary particle detection post-collision
How do you detect elementary particles? What do you aim your detector at? What's a detector physically? How do you know that a particle "happened", if (I assume) you can't see it? Is the ...
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Typically energy of black hole compared to a planet or star of the same mass
Is the typical energy of a black hole much lower than the typical energy of a same-mass planet or star? I guess the answer is yes, energy of black hole is much lower. Otherwise, physicists would ...
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are there any equation which tell us the energies of for example a neutron emitted during photodisintegration from the energy of radiation subjected [closed]
So my question is that if we have a pile of Be9 which can decay upon being subject to radiation with energies of 13 Mev. So that 13 Mev represents the binding energy of the Nucleas of Beryllium 9? and ...
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If a beam of particles travelling at high speeds/ has high energy and decay is induced in the beam will the particles produced also be high energy
If we have a high energy beam of for example Beryllium 9 (this element emits neutrons when subject to high intensity radiation) and we hit it with high energy gamma radiation will the neutrons emitted ...
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Filtering combinatorial background in $B_0$ -> $\mu^+ \mu^- K^{*0}$ decay
We are looking to isolate a signal representing this decay from all possible background candidates produced in a pp collision in the LHCb. We have already dealt with all the peaking backgrounds (J/Psi ...
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Have the $W_0$, $W_1$, $W_2$ and $B$ bosons of Electroweak fame ever been discovered experimentally?
I have read that the LHC, and perhaps other collides, have reached so-called electroweak energies, where the two forces are unified....
So how much energy, exactly, is needed to produce fields/...
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What does an LHC Beam Dump sound like?
What does an LHC Beam Dump sound like?
Is it under a vacuum so that it doesn't make a sound, or does it go boom? Surely the heat generated instantly would make some kind of noise.
This article https://...
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What is the angle between two $b$-quarks when a Higgs boson decays to a $b$-quark pair, in the rest frame of Higgs boson?
I am generating events of $ep -> Xjv$, ($j$ is a jet, and $v$ shows a neutrino) where $X$ particle decays to a $b$-quark pair. I am going to calculate the angle between two b-quarks in the rest ...
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Why didn't the particle-antiparticle pairs collided at the LEP and Tevatron just instantly annihilate into pure energy? (presumably gamma rays?)
I wonder if the fact that protons and antiprotons are roiling seas of non-valence quarks and such with very brief lifetimes means that when they collided at Fermilab they were not perfectly identical (...
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The elusive graviton particle. Why does Hadron colider fail to find this elusive particle. It does exist but i think method for finding it is wrong [closed]
Why does Hadron colider fail to find this elusive particle. It does exist but i think method for finding it is floored.i think that trying to find it by collision is a floored method. My theory is ...
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Which observables in particle colliders are best for discriminating between quarks and gluons?
I have studied thrust and it seems to discriminate between quarks and gluons fairly well as their distributions are fairly separate. Which other event shapes/observables are useful for separating ...
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Why does Pseudorapidity distribution have two peaks?
I found plots(fig2) that state that it is the sum of two gaussian distributions, but I am not able to understand its physical significance. Any help would be appreciated.[PS Why does rapidity not have ...
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On slip factor and phase transitions in particle accelerators
In a uniform magnetic field $B$, a particle with mass $m$, charge $q$ and initial velocity $v$, undergoes a centripetal force (Lorentz force) which makes it travel on a circular orbit, with angular ...
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Why does the LHC use lead ions?
The obvious answer is more energy per collision. This is discussed on p21 in this brochure of FAQs: CERN-Brochure-2017-002-Eng, which I found linked in this old question: Why not build a particle ...
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Does the LHC Beam Dump experience deceleration forces, or only heat?
When the proton beam is dumped into the beam dump, will the dump actually experience the deceleration force of a 200 mph freight train that is being stopped to a standstill in about a microsecond?
If ...
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Experimental particle physics event shapes - why do different products have different event shapes?
Consider two interactions: $ \mu^+ \mu^- \rightarrow d \bar{d} $ and $ \mu^+ \mu^- \rightarrow gg $. The thrust of the down quarks will be different to the thrust of the gluon pair - why is this? More ...
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What is special about collider's designed collision energies?
For example, LHC at Geneva can achieve collisions with energy up to 14 TeV. Why did we set it at this amount?
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Why is the decay channel $H \to \gamma\gamma$ direct evidence that the spin of the Higgs must be different from one?
The title says it all really, I searched this website and came across a post with a question titled Why is the Higgs boson spin 0?. But it doesn't really answer my question in the title.
But this next ...
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What would be the impact of slighty higher mass for the $W$ boson? [closed]
With the recent announcement from CDF
https://cerncourier.com/a/cdf-sets-w-mass-against-the-standard-model/
placing it at the mass at $$80,433.5 \pm 6.4\; \text{(stat)} \pm 6.9\; \text{(syst) MeV},$$ ...
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What does the inverse background efficiency represent?
I am reading a paper from the ATLAS experiment on the identification of tau jets from background jets and came across this figure:
I am struggling to find what the formula is for the inverse ...
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What are "effective" operators and what is meant by effective operators "at the LHC"?
My research supervisor told me to read about this topic but is currently on leave for the next two weeks. I believe it is related to effective field theory but please could someone elaborate on what ...
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What are the Higgsless Theories that can explain the Higgs boson detection at the LHC?
As many know, in 2012 the Higgs Boson was "detected" at the LHC. I have read that the Higgs boson was not actually directly observed, but the existence of the Higgs boson in the standard ...
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Are the rest frames of particles in LHC detectors approximately inertial?
Years ago as an undergraduate, I studied new-physics contributions to the reaction $ cb \rightarrow tb $ in the case that the $t$ subsequently decays as $t\rightarrow be^+\nu_e$. I considered the ...
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How is the collison area cleaned between lead nuclei collisions at the LHC?
My question involves my lack of understanding present in my thought experiment, so I am looking for corrections in my language or mental model.
At the Large Hadron Collider (LHC) collisions happen ...
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Why $R(D)$ is not measured in LHCb and only $R(D^*)$ is measured?
Measurement of $R(D)$ and $R(D^*)$ are important probe of lepton universality violation. They are defined as the ratios of branching fractions:
$$R(D^{(*)}) = \frac{\mathcal{B}(B\rightarrow D^{(*)}\...
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What do objects mean in CERN's collision visualisation?
Trying to find a legend for some of the collision visualisations from CERN's CMS, ALICE or other experiments. The visualisation below is from the CMS Higgs Seminar (4 July 2012). What are the things ...
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Parton, detector and particle level at LHC [closed]
What is the difference between parton, detector and particle level in high energy physics?
I found a similar question but I couldn't understand the explanation for detector and particle level given ...
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How can a person be hit by a high-energy proton beam?
There is this somewhat famous story of a Russian particle physics Ph.D. student from the 70s, who stuck his head into a particle collider and got hit by a beam of high-energy protons. For more details ...
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How to calculate the direction of the missing transverse energy (MET)?
How exactly do you calculate the direction of the missing transverse energy? This paper (arXiv:1412.2641), for example, makes use of it to get some cuts. Adding to this, how can you correlate this to ...
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Why is magnetic field characterized in "Tesla" in case of a solenoid, but in terms of "magnetic field integral" (in $T \cdot m$) in case of a toroid?
Why is the magnetic field characterized in units of "Tesla" in the case of a solenoid, while it is typically characterized in terms of the "magnetic field integral" (so in $T\cdot ...
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How does collision of particles create more particles?
I mean, how do real particles get created in a collider like the LHC?
Is it right that the LHC just gives energy to a pair of virtual particles that were generated by the quantum vacuum making them ...
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Did a particle really seem to go backwards in time during a collision experiment at LHC?
I distinctly remember the news of a weird particle which seems to have gone backwards in time .Probably a Higgs singlet
It was probably a high energy collision between proton and proton . A particle ...
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How long does the LHC take to accellerate a particle to its full speed? How long would a linear accellerator have to be to reach the same energies?
I'm wondering how long it takes the LHC to accelerate particles from rest to their top speed at 6.5 TeV. And related, how long a hypothetical linear accelerator would have to be to accelerate ...
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What if particle colliders cannot find anything beyond the standard model? [closed]
What if the LHC and further colliders can not find anything beyond the Standard Model?
Nightmare scenario:
LHC can not find anything beyond the SM-Higgs-like boson.
VLHC, the linear collider or the ...
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Why can't I assume the quarks inside a hadron move together?
Looking at the following Feynman diagram:
Using conservation of energy, we can see that in the rest frame of $D^0$, the energy of $K^-$ is higher than its rest energy. Meaning, it is in motion. I ...
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How does a booster work in a particle accelerator like the LHC?
In the proton synchrotron booster (PS) booster at the LHC, protons are accelerated from $50 \, \text{MeV}$ to about $1.4 \,\text{ GeV}$. This takes about a second to accomplish. Since the radius of ...
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How can we detect particles that have no electric charge?
Particle accelerators look for electric changes, but what if particle has no effect on other particles or an electric charge, would we not detect it?
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Have we ruled out the Minimal Supersymmetric Standard Model (MSSM)?
This question is inspired by a Physics Stackexchange question posted 8 years ago (The future of supersymmetry). The question that I have is very similar to the question in the above link, except that ...
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Future Plans for Searches for Supersymmetry in the LHC
Due to the failure of the LHC to discover supersymmetry so far (July 2021), the simplest and the likeliest supersymmetric models (e.g. the MSSM) have been ruled out, and the confidence in ...
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Dalitz Plot Analysis and Kinematics
I have trouble understanding the fundamental properties of Dalitz plots. For example the Dalitz plotz for the J/Psi (which is treated as unknown) to 3pion decay:
I.e. we now have the invariant masses $...
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Has the sign of the quartic SM Higgs coupling ever been measured?
I know that for the SM we assume that the quartic coupling of the Higgs $\lambda_H>0$ due to vacuum stability, but in principle for $\lambda_H<0$ vacuum stability could still be safe if we have ...
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How can we control the resolution in experiments (collider, accelerator, etc.)?
Consider for example we perform the electron-proton scattering experiment.
If we accelerate the incident electron with a certain energy, then it means that we can control the center-of-mass energy of ...
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Are we looking at the CERN Supercollider's results the wrong way? [closed]
As some background, I really don't know all that much about physics except what I study in school. So, this question might make me sound like a noob, but I hope I can be beared with.
Anyway, I watched ...
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Luminosity of beamdump experiments
There is formula for luminosity of fixed-target experiments:
$$L = \Phi\rho l$$
$\Phi$ is the flux of incoming beam (particles per second), $\rho$ - density of target, $l$ - lenght of target. We can ...
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Why are jets misidentified as leptons?
I understand that jets come from the process of a proton-proton collision and the QCD confinement which create more quark-anti quark pair that emit this jets of particles. These jets of particles what ...
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Is there any relationship between the recent LHCb results on lepton universality violation and Bells Ineqalities? [closed]
Link to article re LHCb results
As a layperson, my knowledge is limited to what i can understand from pop sci books. Having recently read about (although not quite understood!) Bells Theorem, it ...
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Muons and Electrons Rare Beauty decay
Concerning this recent news from CERN:
CERN data on ‘beauty quarks’ behaviour may rewrite physics as we know it (TRT World, 24 March 2021)
My son and I (now 13yo) have been doing home based weighing ...