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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Hi, what is String Theory and what are the mathematical tools required to derive it? [closed]
An extended form of my question includes:
what is the proof and source of the validity of string theory? [ please link the papers or articles]
what makes strings exist?
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What are Semi-Visible Jets?
I'm working on a project that aims to discriminate semi-visible jets (SVJs) in a QCD background, through learning from simulated data in the context of the LHC. I know that these are related to hidden ...
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Collider luminosity basics
In a collider experiment, the Luminosity is defined as the proportionality factor between the interaction rate and the interaction cross section $dN/dt = L\times\sigma$, with units of $cm^{-2}s^{-1}$. ...
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Proton-proton collisions cross section plot by Stirling
I am struggling to understand some details of the cross section plot by Stirling that is very often shown when talking about LHC physics. See e.g. here: http://www.hep.ph.ic.ac.uk/~wstirlin/plots/...
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Why are there no antimatter-antimatter collisions in CERN?
The labs at CERN create anti-Protons, and have collided them with Protons. Anti-Hydrogen is used to study matter-antimatter asymmetry.
Were there any attempts to collide anti-Protons with anti-Protons?...
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Meson-Meson Scattering Data
Recently, I have been interested in the scattering amplitudes of mesons in the high-energy fixed-angle regime. I have come across a simple result, due to Brodsky et al., that predicts the scaling of ...
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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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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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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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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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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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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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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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What is an inverse femto barn?
I came across the use of the unit barn and inverse barn while reading about the operation of LHC. What is an inverse femtobarn? What does it tell about the experiment being described?
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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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Jet rapidity vs. Pseudorapidity
Thanks to this post
I got a better understanding of what makes (pseudo) rapidity an interesting and often-used concept.
Tangentially working with jet physics (the spray of hadrons kind of jet :), I am ...
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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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Where can I find inclusive $p^+p^+ \to W^+W^-+X^{++}$ cross-section prediction at $14 TeV$ (NNLO)?
The title self explains.. I desperately need the theoretical NNLO (also NLO can work) prediction for inclusive diboson production (WW), a link to a paper would make my week!
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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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How many pairs of nuclei collide in heavy ion collisions?
As each bunch of heavy ions consist of a large number of nuclei it does not seem unlikely that multiple binary ion collisions will occur as it does in p-p collisions. However, should this be the case, ...
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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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With estimates of mass constraints on magnetic monopoles, how likely is one to be found by the LHC (MoEDAL)?
Fermilab seems to have ruled out monopoles with mass less than 850 GeV, but I have seen some estimates of the mass thought to be in the order of up to $10^{18}$ GeV, which, of course, would make them ...
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What is the 'bump' near $M_{\mu\mu}\approx 30\text{ GeV}$
In this (attached) Summer 2011 plot from CMS (twiki page), they have a plot of the dimuon invariant mass spectrum across 3 orders of magnitude in energy. There seems to be a 'bump' near $M_{\mu\mu}\...
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Has the possibility of Higgs boson being a composite particle excluded already?
I heard some theory, such as technicolor, predicts the Higgs-like particle discovered at LHC should be a composite particle (correct me if I am wrong). Has this possible been completely excluded ...
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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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LHC data and mathematics of QFT
I'm reading Towards the Mathematics of Quantum Field Theory by Frederic Paugam, an advanced theoretical physics book.
I would like to know how I could apply the theories in this book. For example, ...
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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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Can black holes be created on a miniature scale?
A black hole is so powerful to suck everything into itself. So is it possible that mini black holes can be created? If not then we could have actively disproved the rumors spread during LHC experiment....
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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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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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Particle Accelerator Energy and Luminosity
Both beam energy and luminosity are important for succesful particle accelerator experiments. The LHC's nominal design is for $7 \ \mathrm{TeV}$ beams and $ \ \mathrm{1\ E34\ cm^{-2} \ sec{^-1}}$ ...
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ATLAS and CMS calorimeters
I was reading this interesting recent review on arXiv about particle identification:
"Particle Identification" by Christian Lippmann (2011), arXiv:1101.3276
In figure 2, there is an ...
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How do they draw collision pictures in Atlas?
Is the picture below a simulation? How to they draw these pictures? The picture is from here.
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In the Higgs boson experiments, why are protons used?
Why are protons used to create Higgs particles at CERN? Can anyone please explain the concepts very simply? (How to explain this to a layman?)
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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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