Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales.
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Why do some particles have a greater mass than others?
The property of mass that almost every particle possesses comes from the Higgs Field. It is this field, which permeates all of space, that particles interact with and hence obtain mass.
But why do ...
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356 views
What does the concept of phase space mean in particle physics?
I came across the concept of phase space in statistical mechanics.
How does this concept come about in particle physics?
Why was it introduced and how is it used?
What does it mean when ...
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196 views
What is the smallest distance between a decaying vertex and an interaction point a detector can measure?
A short lived particle is created at the interaction point and then decaying a distance $d$ away, in some detector. My question is what is the smallest distance $d$ that can be measured ...
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466 views
7 GeV dark matter particle: how particle accelerators missed it?
This posting is regarding the recent confirmation of the DAMA results that might be due to underlying differences in proton and neutron cross section with the dark matter particles, which reflect on ...
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687 views
The contribution to mass from the dynamical breaking of chiral symmetry
The claim is often made that the discovery of the Higgs boson will give us information about the origin of mass. However, the bare masses of the up and down quarks are only around 5 MeV, quite a bit ...
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253 views
particle accelerators and Heisenberg uncertainty principle
In accelerators we shoot very high momentum particles at each other to probe their structure at very small length scales. Has that anything to do with the HUP that addresses the spread of momentum and ...
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152 views
Quantum spin in a rotating reference frame
Rather predictably, I'm having a hard time understanding quantum spin. I know that it has units of angular momentum and relates to rotation, but that it can't be thought of as the actual spin of a ...
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172 views
Inelastic nucleon-nucleon cross section at LHC energies
I am trying to reproduce the number of participants $N_{part}$ in Pb-Pb Collisions at LHC using a Glauber Monte Carlo simulation, specifically aiming to reproduce the values given in Phys. Rev. Lett. ...
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266 views
How are the HEP experiments' invariant mass plots generated?
I am experimenting and playing around with some data, and I'm having trouble seeing how to generate invariant mass plots.
The data I have has a bunch of events, and variables such as ...
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Does the equivalence between inertial and gravitational mass imply anything about the Higgs mechanism?
For example: the role it might play in a theory of quantum gravity (ie causing space-time curvature)?
I realize that inertial mass can result from binding energy alone. Has the equivalence principle ...
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468 views
List of Scattering Phenomena
While at lunch with my lab group we got into discussion of the different types of scattering phenomenon that we encounter in everyday life and physical experiments. We ended up listing about a dozen ...
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100 views
Mechanisms of mass generation for Dirac neutrinos
If neutrinos are Majorana particles, one way of explaining their small masses is the seesaw mechanism.
Now say I'd like my neutrinos to be Dirac, for symmetry to the quark sector. What mechanisms ...
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352 views
Is there a concise-but-thorough statement of the Standard Model?
I’m a grad student in high-energy physics. I’m familiar enough with the Standard Model, but I’ve always wondered whether there existed a canonical statement of, effectively, “what we talk about when ...
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256 views
How do physicists know that mass of possible Higgs particle is limited between two values?
How do physicists know that mass of possible Higgs particle is limited between two values 90 GeV/c$^2$ and 145 GeV/c$^2$?
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113 views
What is the first appearance of the MV (McLerran-Venugopalan) initial condition?
First a quick introduction for the unfamiliar: in saturation physics (my research field), a lot of theoretical work centers on the BK (Balitsky-Kovchegov) equation, which is a differential equation ...
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$WW\to t\bar{t}$ growth
I was told recently that "it is well known that processes like $WW\to t\bar{t}$ ($t$ being a top, or any massive fermion) grows linearly with the energy in the absence of an Higgs boson." Does anyone ...
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257 views
How well is the $\rho$ and $\omega$ coupling universality measured?
Is there any good recent experimental data that tests whether the $\rho$ coupling constant depends only on the isospin multiplet of the produced particle?
EDIT: I got a downvote, so I should explain ...
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206 views
Parametrisation of general MSSM/SUSY based on collider experiment observables
The full MSSM contains 120 parameters. In SUSY searches, one usually picks a model like MSUGRA which makes a few assumptions and only has 5 free parameters like $m_0$, $m_{1/2}$, ....
Now, I'm ...
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Have I discovered how to calculate the proton's mass using only integers?
Could it be possible that the mass of the proton can be calculated by a series of integer sequences? Or is this just a curiosity?
$$\sum_{m=1}^{\infty } \frac{1}{10^{26}(m^2+1)_{2m}}=$$
...
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951 views
What is the difference between a neutron and hydrogen?
Differences? They are both an electron and a proton, since the neutron decays to a proton and an electron, what's the difference between a neutron and proton + electron? so is it just a higher binding ...
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544 views
Why are neutrino oscillations considered to be “beyond the Standard Model”?
Is this just a historical artifact - that the particle physics community decided at some point to call all of the pre-oscillation physics by the name the "Standard Model"? The reason I ask is because ...
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Why can't a single photon produce an electron-positron pair?
In reading through old course material, I found the assignment (my translation):
Show that a single photon cannot produce an electron-positron pair, but needs additional matter or light quanta.
...
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350 views
What's with the very slightly larger mass of the neutron compared to the proton?
Neutron mass: 1.008664 u
Proton mass: 1.007276 u
Why the discrepancy?
On a related note, how does one go about measuring the mass of a neutron or proton, anyway?
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Cosmic ray hazards
The Pierre Auger Observatory site mentions the detection of a 3E20 eV (48 J) cosmic ray whose energy, well above the GZK cutoff, was based on an analysis of its atmospheric shower. This was equivalent ...
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About free quarks and confinement
I simply know that a single free quark does not exist. What is the reason that we can not get a free quark?
If we can't get a free quark then what is single-top-quark?
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What are quarks made of?
So atoms are formed from protons and neutrons, which are formed from quarks.
But where do these quarks come from? What makes them?
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Quantum Field Theory cross sections integrals
Where can I find some examples of cross sections calculations in QFT done step-by-step? Those integrals are a little horror. For example - a simple scalar+scalar -> scalar+scalar at the tree level in ...
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408 views
How was the Oh-My-God particle observed?
How exactly was the Oh-My-God particle (ultra-high energy cosmic ray) observed and its energy measured?
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425 views
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 ...
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390 views
Is nature symmetric between particles and antiparticles?
Is nature symmetric with respect to presence of particles? Do we have an antiparticle for every particle thought of? Are there any proven examples where we don't have an antiparticle? And what about ...
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Neutrino versus Anti-neutrino Detection
Is there a that detection method in use that can distinguish between a neutrino from its anti-neutrino?
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687 views
Jauch, Piron, Ludwig -> QFT? [duplicate]
Possible Duplicate:
What is a complete book for quantum field theory?
At the moment I am studying
Piron: Foundations of Quantum Physics,
Jauch: Foundations of Quantum Mechanics, and
...
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216 views
What is the Standard Model equation which unified Strong, Weak, and Electromagnetism?
I always heard that three atomic force in small scale structure (Strong, weak and electromagnetic) are unified through the standard model, but I've never seen its unified equation. What is single ...
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323 views
How can some-one independently do research in particle physics?
I'm not affiliated with a physics department and I want to do independent research. I'm working my way through Peskin et. al. QFT now. Let's say that I've finished Peskin et. al. and Weinberg QFT ...
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479 views
Higgs Boson Mass
The WIKI Higgs boson site has an interesting diagram illustrating likely Higgs mass intervals that experiments (LEP & Tevatron) or indirect measurements have determined with a 95% confidence ...
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Does a Photon leave trace in a silicon tracker?
I am having this image from ATLAS Detector.
In gray you can see the ATLAS's Si Tracker.In Green you see the Electromagnetic Callorimeter. In red there is the Hadron Callorimeter and in Blue there ...
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587 views
What is the relationship between string net theory and string / M-theory?
I've just learned from this one of Prof. Wen's answers that there exists a theory called string net theory. Since I've never heard about this before it picks my curiosity, so I`d like to ask some ...
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251 views
Why mass, charge and spin are good labels for elementary particles?
Why mass and charge are good quantities to labels elementary particles?
[I know that what qualifies to be a good label must be a quantity that is invariant under some kind of transformation, but why ...
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hadron jets from quark-antiquark in colliders
The observation of hadron jets from electron-positron collisions (LEP)
is explained (e.g. Wilczek, The Lightness of Being, p 55) as follows-
e,p collide and produce a virtual photon.
the photon goes ...
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What has been measured at the Higgs experiment and what do we know now?
Explained at the level of a 5$^{\text {th}}$ semester physics student (i.e. pre QFT, but far beyond the level of a news article for non-physicists, which avoids all details and only deals in ...
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299 views
How do we know the geodesic is a minimum?
The geodesic equation is derived from the Euler-Lagrange equation, which (as I understand it) is a necessary but not sufficient condition to ensure that the geodesic is a minimum.
The introductory GR ...
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Maximum electron momentum in $\beta^-$-decay
This should be easy, but I think I have a mind-block...
For $\beta^-$-decay, what is the maximum possible momentum for the electron? The two equations I can use are conservation of energy and ...
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1k views
Difference between Higgs and anti-Higgs Fields
I'm assuming the LHC can create a Higgs and an anti-Higgs boson. If so, would their fields be identical with respect to mass effects? How would LHC detectors distinguish between the two bosons?
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312 views
Will negatively charged strangelets be produced by the LHC?
Witten (and earlier, Bodner) hypothesized that strange matter (up, down, strange quarks) should be more stable than "regular" nuclear matter(The strange matter hypothesis). That is that the typical ...
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619 views
Particle physics getting started
I know classical physics, quantum mechanics, special relativity, basic nuclear physics.
I would like to get into some particle physics.
I want to get into that higgs boson, lepton, quark things :D
...
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244 views
Why is the majorana particle a fermion?
My knowledge of quantum mechanics is rather limited, but what I always understood was that Bosons have integer spins and Fermions have half-integer spins.
My question is very simple: the Majorana ...
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195 views
Assuming that extra dimensions will not be visible at LHC, what motivation will still remain to study them?
Many physicists believe that there is little possibility of observing extra dimensions at LHC so that some extra dimension models originally designed to solve hierarchy problem (ADD/Randall-Sundrum) ...
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342 views
CP Violation of the CKM Matrix
Considering the relation between the $SU(2)_{WEAK}$ partners of the $|u \rangle$, $|c \rangle$, and $|t \rangle$ mass eigenstates and the corrseponding downtype eigenstates
$
\left(
...
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What does tagging in experimental high energy physics mean?
Could someone explain in details the meaning of the terminology "tagging" in experimental high energy physics and how is it used in the analysis ?
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391 views
What is meant by “combinatorial background” in experimental high energy physics
My guess is that they find a certain tracks coming from a certain source by "combintaorially" selecting all track pairs and finding their invariant mass. If this is true, of which I am not sure, how ...
