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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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Latest SUSY limits from LHC [on hold]

What are the latest limits on low energy supersymmetry scale from experiments (LHC, etc.)?
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Don't matter-antimatter annihilate each other completely releasing energy as photon?

Matter and antimatter should annihilate each other completely releasing energy in the form of photon, however it is discovered that smashing electron and positron together can also spew out higgs ...
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Could we use experimental evidence of micro black holes to prove the existence of additional spatial dimensions?

They are planning to create a new particle accelerator that can smash particles together at a much higher energy than the LHC. If in the process we observe the decay of a micro black hole, would that ...
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Does superconducting magnet prevents energy loss when hadron is being accelerated?

I read up on how synchrotron works and electron will heats up by emitting photon when it is steering(accelerating) around a bend, so more bends more heat loss. By heat I mean energy not necessarily ...
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What are “large hadrons”? Are there also “small hadrons”?

The BBC News article Cern plans even larger hadron collider for physics search says: The difficulty with Cern's proposals for a larger Large Hadron Collider is that no one knows what energies will ...
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How to analyse the LHC signal for Higgs?

With increasing energy the collision decreases in the plot for signal in LHC. why is that? and at an energy 125GeV the no of events suddenly increases. How this proves that higgs has a mass of 125GeV?
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What would happen if antiprotons were studied under the conditions of particle deceleration that they are collected under? [closed]

I have not had a very clear understanding of how antiprotons are collected, but I do know that when they collide with matter they explode in a puff of energy. Or so I have been told. If the current ...
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Is anything expected to be found at CERN with 14 trillion electron volts that wasn't found at 13?

Based on this article the accelerator has smashed together approximately 16 million billion protons since 2015, when it reached its current energy of 13 trillion electron volts. Planned ...
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Is it possible to replicate condition at planck time after big bang by smashing 2 protons really hard?

Because we need to achieve really really high temperature to mimick the condition just planck time after big bang, so suppose we can accelerate 2 protons at extremely close to speed of light and let ...
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How can a single particle hit many pixels in Large Hadron Collider?

In the Large Hadron Collider, the way particles are detected (specifically in ATLAS) is analogous to detecting photons using a photodiode(analogous is an exaggeration, but will suffice for the ...
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How is antimatter stored in the large hadron collider?

we studied that antimatter can be stored in the large hadron collider. what i dont get is that the collider is used to collide particles and antiparticles together right? so how is antimatter stored ...
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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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Light neutrino number from the invisible decay width of $Z$ boson, and precluding heavy neutrinos as dark matter candidate

The $Z$ boson decays into pairs of quarks and leptons. While the decays to quarks pairs and charged lepton pairs can be observed, the decays to $\nu\bar\nu$ are cannot be. By subtracting the visible ...
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ATLAS jet energy corrections

I've been reading this paper and on page 3 at the beginning of section 3 it states: 'After the events are recorded, the trigger-level jet energy and direction are corrected to those of simulated ...
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Invisible energy in a particle collision

I read a lot about the so-called "missing" energy in hadronic collisions. I always thought that it was mainly due to neutrinos and also nuclear deformations, but today I read that "on average, 30% of ...
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The Large Hadron Collider and Black Holes

Last week, I went to Switzerland and visited the LHC. I took a tour, and the guide told us that it is possible for black holes to appear in the LHC, but they will be so small, that they would ...
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Mass vs cross-section studies

Let's assume we have a event generator like "Pythia", and from that I have collected four momentum of a certain lepton production. the leptons are from excited gamma state. And the excited ...
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Can a rebranded super-symmetry be consistent with the null results at the LHC

To explain the null results on SUSY at the LHC, it continues to be assumed that the achievement of the energy threshold for the creation of the SUSY partners is beyond the capability of the ...
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How are particles in a collision chosen?

In synchrotron particle colliders, how are the particles which are collided chosen? For the most part, collisions of different types of particles don't do anything like you might expect in a video ...
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high $p_T$ and low $p_T$ b-jet energy correction factor

For b-jets, to get the true transverse momentum using the reconstructed $p_T$, we use a correction factor $p_{T}^{gen}/p_{T}^{reco}$ obtained using MC. Now suppose I make a plot of $p_{T}^{gen}/p_{T}^{...
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Does the vertex efficiency include track reconstruction efficiency?

Consider a document of ATLAS collaboration on displaced vertex level efficiency. On the first two pages there is a description of cut-offs required to background free displaced vertex reconstruction. ...
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Why are the elastic and total cross-section of $pp$ collisions increasing as the C.O.M. energy grows?

Well, that's about it. I don't find any reasonable explanation for this fact. Are they transversally expanding as the energy increases? Please, remember that strong interactions are short ranged and ...
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proton - proton collision, does LHC have any data regarding conservation of energy?

Does LHC release data regarding the calculation of input energy and measurement of output energy from their detectors during proton-proton collision. If yes, then how much is the measurement error? By ...
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Dark Matter Monojet signal

Dark matter can be observed at the LHC via a mono-jet signal i.e $pp\rightarrow XX + jet$. These signals can proceed via parton level processes like the mono gluon or mono photon ones. I was ...
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Pile-up in particle physics

Regarding pile-up, I came across two definitions. One dealing with electronics of detector where more than one event get recorded at the same time and other regarding all the pp collisions in the ...
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Computing hadronic cross sections with PDFs

I am trying to estimate the cross section for a BSM process at the LHC, and I would like to ask if anyone knows what is the simplest way to integrate over the PDFs, for example with Mathematica. I ...
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How are high-energy detectors able to to distinguish between $m_{e}$ and $m_{\mu}$?

I had a teacher pose this interesting question yesterday: Suppose you're running a high-energy scattering experiment at the LHC. For concreteness, let's suppose it's a 2 to 2 scattering event which ...
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Does the LHC see electro-weak symmetry breaking? [duplicate]

The energy scale of electro-weak processes is around $160$ GeV. But the LHC has a centre of mass energy of $7$ TeV... so do they see processes involving the $W^1, W^2, W^3$ and $B$ fields, before ...
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Tracking efficiency for experiments at CERN

For various experiments (e.g. ALICE, CMS etc) at the CERN-LHC, people talk about tracking efficiency. What exactly is this tracking efficiency? How different is it from reconstruction efficiency?
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What is the reason for a wide B$_S$ peak in dimuon plot?

Why is the B$_s$ meson peak in dimuon invariant mass spectrum wider than the others? Upsilon meson has a lifetime of several orders of magnitude shorter, which by my intution should lead the wider ...
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Observing signal over background

In the search for the Higgs boson, we look at particular decay channels of the Higgs and apply various cuts in order to maximize the signal to background ratio (background = non-Higgs events which ...
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Transverse mass of Higgs boson

There is lots of literature on Higgs decay to two leptons and two neutrinos ($H\rightarrow WW^*\rightarrow ll\nu\nu$) The transverse mass is defined as $m_{T}^2 = (E_{T}^{ll} + p_{T}^{\nu\nu})^2 - |...
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Collider physics; what is a jet residual?

I'm looking at a list of jet parameters (in a .root file). One of them is called JetResidual. It's there alongside parameters like ...
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Particle detection at LHC - leptons and jets

Invariably, the events that are triggered on have large transverse momentum, so it seems plausible that a jet and a lepton are often detected in nearly the same point of the detector. In this ...
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If we had enough energy available in particle colliders, what reactions could show up if the quark and electron fields weren't fundamental?

Suppose the quark and lepton fields weren't the fundamental fields of Nature, but that a "deeper" Lagrangian connected to a generic model of sub-quarks and -leptons would take over the conventional ...
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Probability densities at the LHC

Let $\sigma$ be a cross-section for the collision of two protons as given by $$ \sigma = \intop_0^1 \mathrm{d}x_1 \intop_0^1 \mathrm{d}x_2 \, \sum_{a,b}f_a(x_1,Q^2) f_b(x_2,Q^2) \frac{1}{2\hat{s}} \...
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Is it possible that there are more than 6 quark flavors/more than 3 generations? [duplicate]

I thought that things like the top quark don't exist in nature because they're super unstable and we can only observe them after high-energy collisions (e.g. LHC) Is it possible to make even more ...
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How does CERN simulate and interpret a simulated SUSY event of the Atlas detector?

Why do these histograms correspond to a simulated SUSY event? What kind of superparticles do we actually see here? We observe 3 histograms, but what do they tell us? How do they simulate such things? ...
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How can I access event data for LHCb calorimeters?

I want to do a project using machine learning on the calorimeter event data of the LHCb. How can I access this data? Is it very difficult to navigate your way through the source code on your own? I do ...
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How does the LHC separate the protium isotope to have only protons for the collision?

I am preparing a presentation for my physics class about the LHC and the following question arose: Every text about the LHC says that it collides protons from a gas of hydrogen whose electrons were ...
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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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Event rate for nuclear collisions covariant form

The event rate on a target of atomic mass $A$, with cross section per nucleus $\sigma$ is given by: $$dR=\dfrac{N_{A}}{A}\sigma\,mv\,dn$$ where $N_{A}$ is the Avogadro number, $m$ and $v$ are the mass ...
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What do we mean by fit of data in particle physics?

I am unable to clearly understand the meaning of fitting the data. Like in this paper of determination of mass and width of Z boson and number of neutrinos (from ALEPH detector) Does it mean that ...
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Decay of Z boson

I have following queries regarding the decay width of Z boson. In thisThomson's lectures, page 479, it says that decay of Z to hadrons have a large cross section because of factor 3 from colors. But, ...
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What is $\sigma_{i\eta i\eta}$?

In LHC experiments like, CMS there are variables like ieta which are used for designating the eta (pseudo rapidity) of each of the sub detector components. There are several plots which I came ...
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Periodic multi-layer scattering of neutrons

I am trying to understand the reflectivity plot on slide 26 of Neutron optics,Soldner lecture. 1.Is the peak from $\theta$=0.0 to 0.4 due to total external reflection from the first upper surface?. ...
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Difference between optical potential and nuclear potential (used in neutron optics)

I am discussing a question related to elastic coherent scattering of neutron from a nucleus. I am referring to the terms (optical and nuclear potential) which are used on page 272 of the review ...
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Coherent scattering of neutrons

It is said that neutrons have small scattering angles in case of elastic coherent scattering. I am having some queries regarding the same. Why do we call it coherent? I mean, we say that for coherent ...
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What is the difference between data-driven and semi-data-driven techniques?

I keep hearing the terms data-driven and semi-data-driven techniques(especially for background estimation) in many CERN analysis talks. I looked for their difference but didn't find any documentation ...