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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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 ...
user81619
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How to integrate over rapidity for Parton Luminosities in LHC?
I want to make a comparison of parton luminosities between Tevatron and LHC. According to Factorization theorem the cross section in hadron colliders, as long as the partonic cross section has $\hat \...
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Baryonic density in collision experiments
Does anyone know any way of estimating the net baryon density in collision experiments, e.g. in LHC, RHIC, or the upcoming ones at GSI-FAIR?
I have comes across many hand-waving arguments, sample -
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What properties of dark matter can we derive from each of the available methods for probing the physics of dark matter?
This is probably a long shot but it's worth trying. My question is the following:
What properties of dark matter can we derive from each of the available methods for probing the physics of dark matter?...
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Current experimental evidence of lepton flavour violation other than neutrino oscillation
Is Lepton Flavour Violation (LFV) experimentally established in processes other than neutrino oscillation? This answer by Luboš Motl points out that
Interestingly, CMS has detected a 2.5 sigma ...
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Where can we find LHC results talks online?
I'm looking to educate myself on some searches at the LHC, but I find it easier to understand what's going on if I watch a LHC results talk (e.g. by ATLAS, CMS, or an overall summary by a theorist) ...
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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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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 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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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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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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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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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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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 ...
user81619
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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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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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Nature of particle spectra at ALICE
I have a question regarding the nature of the particle spectrum at ALICE as a function of momentum. The spectra in question can be seen here.
My question is, why is it that the particle spectrum in ...
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Limits on stable charged particles
Are there generic model-independent limits on massive stable charged particles (say 10-500GeV)? I mean SU(2)/color singlets with just a hypercharge.
For example the LEP search (CERN-EP/99-075) was ...
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What is the relationship between Luminosity, Intensity, and Flux?
I am always confused by the terminology:
In high energy particle scattering, and in particular, in the context of collider physics, what is the relationship between luminosity, intensity and flux? ...
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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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The Collins-Soper frame
I am looking for some thorough notes on the Collins-Soper frame. This is a reference frame used in Drell-Yan process in hadron colliders.
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Total cross section in hadron colliders with optical theorem?
In hadron colliders (like LHC) the total cross-section is calculated using the optical theorem.
The origin of this is the scattering of two particles which is solved with the Schrödinger equation ...
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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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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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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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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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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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Feynman type write up for particle physics observables?
In gist: Struggling particle physicist (on the verge of giving up)
needs qualitative writeup/article of the various aspects of heavy-ion physics:
Kinematics,transformation (Lab <-> Center of Mass)...
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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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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 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 ...
user86411
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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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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 ...
user81619
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Can TOTEM's T2 detector measure differential cross sections?
My current research involves making a prediction for data collected by the TOTEM experiment at the LHC. The experiment is primarily designed to measure the total inelastic and elastic scattering cross ...
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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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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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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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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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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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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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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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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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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 ...
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Higgs to gauge bosons branching ratios
Why does the Higgs to $WW$ branching ratio dominate the $ZZ$ branching ratio so much? Their couplings are quite similar, so what could explain the fact that, at high energies, there are many more $H^0 ...
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How can I build up my knowledge in particle physics to the level that I can calculate the path of elementary particles in a perfect vacuum?
I have to write a research paper (don't know the exact english translation) for school. The question I want the paper to answer/discuss is: 'Can the universe be predicted at sub-atomic level?'
The ...
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Why does CERN use magnets instead of capacitor grids like an electron gun?
The CERN tunnels use klystrons to accelerate the protons
https://home.cern/science/engineering/accelerating-radiofrequency-cavities
But electron guns use an electric field to accelerate electrons. ...
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$W^+/W^-$ bosons ratio in proton-proton collision
I'm studying my first-year physics in college, and I'm having to write a report of some proton-proton collisions that were registered in the LHC of CERN years ago. The main goal is to identify ...
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