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 of up to 7 TeV. It contains the important detectors ALICE, ATLAS, CMS and LHCb.

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Detecting supersymmetry

What would scientists in particle colliders look for as evidence of supersymmetry?
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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 is the decay width of a resonance is measured?

Last December LHC found an excess in the diphoton channel around 750 GeV. Along with number of excess events and cross section for proton proton -> gamma gamma process, they also provided a width for ...
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57 views

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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45 views

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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54 views

$e^+e^-\to q\bar{q}$: 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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39 views

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 ...
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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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100 views

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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160 views

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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64 views

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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39 views

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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Parent particles. Production modes of hyperon $\Lambda$

In the PDG are listed the decay modes of the known particles. I wonder if there exist lists with the production modes of particles. It is, lists with all the possible parent particles that decay into ...
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35 views

Proton-Proton collision [duplicate]

How are the people at CERN able to exactly collide protons head on? What about the HUP? Do they accelerate many particles and smash them so that at least some of them collide head on?
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What is the meaning of the minimum separation requirement?

In this work, BHsearch done by CMS, they reconstructed and identified objects using certain conditions. And finally, in Page 3, the last paragraph requires that the minimum separation between any two ...
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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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125 views

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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70 views

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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92 views

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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71 views

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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1answer
79 views

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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How much damage do high energy experiments impose on the LHC detection equipment?

I do appreciate that I am second guessing lots of experts who have already considered this aspect of high energy experimentation, but I have not seen a similar question, my apologies if I missed a ...
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3answers
149 views

New particles found using the LHC

After finding the Higgs boson in 2012, CERN. What did the CERN found recently using the large Hadron Collider?
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Does this phrase in “Knocking On Heaven's Door”, refer to gravitons?

This is an extract from Knocking On Heaven's Door, by Randall (2011) The suprising fact is that if you have a stable particle whose mass corresponds to the weak energy scale that the LHC will ...
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1answer
292 views

The (relativistic) mass of a proton in the LHC

What would be the (relativistic) mass of a proton, in grams, as it is traveling at the maximum possible speed in the LHC?
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63 views

Precise definition of Jet Energy Scale and Jet Energy Resolution

I've been struggling to get the precise meaning of these two quantities, is it correct to say that the first one is only related to Montecarlo simulations? I can't seem to find a pedagogical ...
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1answer
101 views

Collision symmetry and measuring the asymmetry in the Drell-Yan process

I saw a talk the other day about an asymmetry in the Drell-Yan process caused by CP-violation: Apparently one way this can be measured (ATLAS is doing this) is to collide protons and observe the ...
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1answer
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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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1answer
125 views

Objects colliding at relativistic speeds combined energy?

LHC is currently capable of accelerating a batch of atoms faster than $0.5 \, c$. What if we made a second LHC that intersects the original at, lets say the atlas chamber, but that runs in the ...
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1answer
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Do we regularly measure and update our physical constants (By using the LHC)?

This question is motivated by sheer curiosity. I certainly do not expect that the free parameters we use in the standard model have changed in value since we started measuring them with a "modern" ...
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Earth still exists - does this fact tell us anything about LHC safety?

When LHC was about to be launched there were many fears that it would destroy the world. To counter them scientists tried to carefully examine all possibilities and concluded that there is nothing ...
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1answer
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What energy will the LHC use for pA collisions in Run 2?

Part of the LHC's Run 2 (which just recently started) will be dedicated to proton-ion collisions, but I haven't been able to find any firm information about what energy those collisions will run at. ...
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1answer
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Why in particle physics the background of resonance is a decaying exponential?

When in particle physics they plot the mass histogram we see a resonance on top of a decaying exponential background? Why is the background modeled to be that way? what is the physical explanation? ...
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1answer
99 views

What is meant by a preliminary run at the LHC?

I am a bit confused over the meaning of "Preliminary run" when referring to the LHC experiments CMS and ATLAS. For example in this summary, Figure 2 refers to both the CMS $19.7\ \mathrm{fb^{-1}}$ ...
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2answers
468 views

Why can't gravitons be created in traditional particle accelerators?

I've heard that it is incredibly difficult to detect a graviton, but I don't quite understand why. With all of the knowledge I have at the present time it seems like it should be possible to create a ...
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CMS magnetic field outside

The magnetic field at CMS is often given as 4 T. According to this picture the field outside the solenoid is just 2 T. Is this just because the field of a solenoid is not constant and decreases with ...
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What processes are involved in proton proton collision?

There is a lot of advanced materials at the internet but nowhere can I find brief introduction to the topic of proton-proton collisions in collider experiments (such as the large hadron collider). Can ...
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1answer
100 views

Decay channels of the Higgs Boson in Large Hadron Collider particle production

I attach a diagram of 4 of the (many) possible decay channels produced by the Higgs boson, and I have read that 57 % of the time, we find a bottom quark, antibottom quark pair resulting from this ...
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Large Hadron Collider 2015 upgrade, what may we discover?

I realise that the initial answer to my question that may come to mind is, "we don't know yet, obviously" But my question is hopefully not opinion based. For example, does this upgrade have a ...
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1answer
232 views

Signs of supersymmetry and thus dark matter at CERN

The Large Hadron Collider at CERN has just re-started after a two year pause and is now running at unprecedented levels of 6.5 TeV, with collisions that will release up to 13.5 TeV. With this increase ...
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How many different experimental configurations does the Large Hadron Collider have?

I understand that the LHC can collide protons with protons, heavy ions with heavy ions, or protons with heavy ions, giving three main configurations. But, I'm wondering: is that the only property that ...
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Is there a significant possibility of the LHC missing “exotic” particles or events?

In his popsci book, "Particle at the end of the universe", Sean Carroll says that the LHC, due to it's sheer information gathering capability, necessarily needs to completely discard most of the data ...