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Dec
4
comment What would happen if you put your hand in front of the 7 TeV beam at LHC?
the reflex time of 0.1-0.2 seconds is much larger than the time it takes for the beam to do one turn (which is about $90 \mu s$), once protons interact with the hand, most of them will not make another turn (the beam blows up in the transverse direction), i.e. the reaction time is slow enough to absorb one beam entirely. $1.2 \cdot 10^{11}$ is more the number of protons per bunch, of which there are up to 2808 per beam (see here which would give $3.4 \cdot 10^{14}$ protons per beam.
Dec
4
comment What would happen if you put your hand in front of the 7 TeV beam at LHC?
The design number of bunches is 2808 per beam (see here and $1.15\cdot 10^{11}$ protons per bunch ($3.2 \cdot 10^{14}$ protons per beam), you'll get 362 MJ per beam (at 7 TeV beam energy)
Nov
28
comment What role did the Higgs boson play in the Big Bang?
see the Wikipedia article on the Inflaton, which is a general term for a scalar field which drives inflation. The Higgs field is a scalar field and could be the Inflaton (i.e. drive inflation).
Nov
7
comment Unitarity of PMNS matrix
if any row or column squared sums to something less than one (experimentally), this is an indication that we're missing something, e.g. a fourth row/column corresponding to an additional species of neutrinos.
Nov
6
comment Software for calculating Feynman Diagrams
MadGraph does only tree level (no loops but many outgoing particles), MadGraph5_aMC@NLO can do one loop
Nov
5
comment Kitchen floor dries faster with lights on?
although traditional incandescent light bulbs and fluorescent tube lights have an efficiency far below 50% (according to en.wikipedia.org/wiki/Fluorescent_lamp#Luminous_efficacy), so more energy is converted to heat than to light for these.
Nov
1
comment Kitchen floor dries faster with lights on?
yes, good point, and the water in turn would heat the region of air immediately above the water
Oct
10
comment How detectors in particle colliders can differentiate neutrons from antineutrons?
because anti-quarks in the anti-neutrons annihilate with the quarks in the protons and neutrons in the carbon nuclei while at such low energies, a neutron essentially behaves like an (unbreakable) ball
Sep
29
comment How can I measure the speed of a figure skater's spin?
the stroboscope (or camera flash which has such a function) probably only works well if she can spin for a enough time while you adjust the stroboscope's frequency...
Sep
29
comment why are two higgs doublets required in SUSY?
see also physics.stackexchange.com/questions/116598/…
Sep
26
comment Why more than one Higgs?
Is there a typo here we don't want the theory to be renormalisable ?
Sep
7
comment Is the photoelectric effect a type of nuclear decay?
good point, so 'photonuclear reaction' is probably more adequate.
Sep
6
comment Is the photoelectric effect a type of nuclear decay?
The article on induced gamma emission I linked starts with the sentence: "In physics, induced gamma emission (IGE) refers to the process of fluorescent emission of gamma rays from excited nuclei". That's what the original poster was looking for as an analogy to the photoelectric effect, isn't it ?
Aug
20
comment How does one experimentally determine chirality, helicity, spin and angular momentum?
actually, the original poster asked for fundamental particles which usually means that they are not composite.
Aug
20
comment How does one experimentally determine chirality, helicity, spin and angular momentum?
in fact, at least in the Standard Model to talk about chirality makes only sense for the fermions (or the sfermions in the MSSM which have spin 0), because chirality is defined by how the corresponding field/particle transforms under $SU(2)_\mathrm{L}$
Aug
18
comment What is the total kinetic energy per second of the particles accelerated by the LHC
Note that the 4 Terawatts counts each particle about 11'000 times (the number of revolutions per second). You could not exploit this power: if you were to fully absorb the energy of the particles (e.g. at the beam dump), the machine would be empty after one revolution.
Aug
18
comment Can lightly-ionized atoms be accelerated to relativistic speeds with current technology?
the ions in these accelerators are fully ionized, not lightly (for lead, this would be Pb 82+), the force exerted on the fully ionized ions is much larger than on the singly ionized while the mass (to be accelerated) of both is more or less the same.
Jul
24
comment What will be the goal of (V)LHC after receiving upgrades?
175-200 TeV will certainly not happen in 2019. The energy limitation of the current LHC comes from the maximum field the dipole (bending) magnets can produce. To go to higher energies, one needs to either dig a longer tunnel or do extensive research & development to build large scale magnets achieving higher magnetic fields or both (this is called FCC-hh, there is also a similar Chinese project). Given the large cost of such a project, studies are currently going on to reduce cost and a decision whether or not to build such a machine will not be taken until we have more results from LHC.
Jun
18
comment What is the symmetry associated with the local particle number conservation law for fluid?
see also the question on the symmetry associated to the conservation of mass here: physics.stackexchange.com/q/2690
Jun
18
comment What is the symmetry which is responsible for conservation of mass?
see also physics.stackexchange.com/questions/24596/… on the discussion of the converse Noether's theorem