High Energy Physics - Phenomenology - Science topic

Blind people have no visual imagery in their dreams, if born blind. Dreams do process past memories; in a dream, different temporal memory layers can be mixed over into 'one film'. We do not dream with our eyes, it is a brain function in sleep as the brain is a non-stop organ (you could put a light bulb on it).The existence of pre-cognitive dreams, which is portrayed in prophetic literature, e.g. Joseph in Egypt, cannot be ruled out. A healthy sleep cycle (chronobiology) and dreamimg are closely connected, in medical terms, to 'free' the memory from non-necessary psycho-logical ballast of life experiences.

okay then, dear mr. Baumgarten, why don`t you calcutate the square root of c²; maybe because between minus-c and plus+c the result were 2*c?! and why do physicists handle with c² if that were km² per square-seconds? is square-second 2-dimensional?

Essentially because for Majorana spinors ψ̅ γ_μ ψ = - ψ̅^c γ_μ ψ^c (sorry for not being able to type the bar over c, you should read psi-c-bar)  where ψ is a real four component spinor and c denotes charge conjugation. You can see the book: Particle and Astroparticle Physics by Utpal Sarkar, pages 142-143.

PS: It is best to prove this just by brute force.

@Christian Baumgarten  I think he ask if electron can round in different direction like stop the earth and round them to the other side ;)

Dear Eder problem is that spin Has nothing to do with round because is not a ball !!!

best  

Of course it can. The width is controlled by the ways the particle interacts with others. And that's one way to detect, indirectly, the presence of unknown particles. 

However it's the other way around: the higher the value of the width in units of energy, the shorter the decay time is, so the faster the particle decays. 

By modifying physics at a higher energy scale, I think you can do almost anything.

The question is whether the standard model is stable on its own, or has another negative minimum for very large field values. The answer to the last question is much more subtle than often discussed, since most properties of the effective potential, and the field on which is depends, are gauge dependent and dependent on the renormalization scale. More discussions can be found in the linked papers.

Hossein,

Why is it that people vote down the question?  It must be that they do not understand its importance.  If we knew all there was to know about the sub-atomic then this would be a meaningless question, however we know only what "Theory" tells us and that is obviously wrong.

There needs to be a new model to the atom and we have known this ever sense Niels Bohr proposed the current model more than 100 years ago.  

Even at the time Bohr knew that this was only a way to look at the atom and not the answer, yet we look at it at the truth.

The question puts into question our reasoning behind theory that has no bases in reality.  If there is objection to this line of questioning then logic has no place in science.

Where are the researchers that understand logic?

Gluons don't become massive in the infrared limit-that statement is incorrect.  Nor is the statement about the gluon jet losing kinetic energy correct, either. The references to the two slit experiment aren't relevant.  It's useful to consult textbooks or lectures on the subject, that's now background knowledge, e.g. 

The statement ``the emitted gluon at finite energy becomes a spatial coordinate singularity'' is meaningless and the statement that the gluon propagator doesn't have a spectrum beyond the first Gribov horizon is meaningless, also. What the Gribov ambiguity means is, simply, that it's not possible to fix the gauge uniquely, one must use coordinate patches in field space. Cf. http://projecteuclid.org/euclid.cmp/1103904019 

However, when performing a tree-level computation one isn't sensitive to the Gribov ambiguity, since one is working in the coordinate patch  about the identity in field space, anyway. 

Finally, the quoted text doesn't have anything to do with any comparison between a tree-level calculation and a higher loop calculation, so is completely irrelevant to the issue. It certainly doesn't produce either a mass gap or an example of color confinement. Cf. http://arxiv.org/abs/1008.1936 for how gluon jets are studied.

Dear Filipp!

The quintessence of the article: Reines and Cowan were interpreting the observations according to the theory. Look at the illustrations!

Regards

Hans

Another paper on this topic:

M. D. Tarasov et al, 'Efficiency of Radioluminescence of Water under the Action of Accelerated Electrons', Instruments and Experimental Techniques, 2007

Quantum mechanical position and momentum operators are not field operators of a relativistic field theory and therefore no micro-causality condition applies to their commutator. It is important to notice that the field operators of a quantum field theory are labeled by space-time points (or by space-time based test-functions) and that this labeling (a mapping in terms of mathematics) makes up an indispensable part of the physical meaning of a quantum field theory. Here I can't take the time to explain how the commutation (or anti-commutation) of space-like separated field operators is related to the physical concept of causality. The probably best book on the matter is R. Haag: Local Quantum Physics, Fields,Particles, Algebras, Springer, second edition 1996.

As to the second part of the question: Since the Schrödinger picture is related to the Heisenberg picture by an obvious mapping (formal, as all field-theory) there is no need for a independent formulation.

Sorry I have only seen this question now... anyway, I can provide you with a partial answer. In a nutshell, I think it it fair to say that, NO, there exists no such relation. The reason is that the production of keV neutrinos via resonant enhancement happens during a very complicated epoch in the Universe, the QCD transition, in which it is not even clear whether quarks or hadrons are the actual particle states. Thus, whenever you see an approximate formula, it is likely to be valid only in a very definitive regime, in which the resonance conditions is met under particular circumstances, but if some parameters are varied slightly, such a formula would need to be replaced by another one. Hence, although the process can be computed numerically by the respective experts, it is hard to boil things down to a very simple back-of-the-envelope formula. More complicated formulas do exist, however, but as far as I know they do only hold for certain regions in the parameter space (at least I have not seen a complete one).

The most complete reference I think exists is 1208.4607 by Canetti et al. The authors do go into some detail about resonant production of keV neutrinos, however, even this long text cannot contain all aspects so that they refer to previous works for some particular issues (e.g. taking into account hadronic effects). Nevertheless, this text contains many aspects and probably all you are after.

Let me note that there exist also some alternative production mechanisms such as producing keV neutrinos from (mainly) scalar decays. Variants include this scalar being identical to the inflaton (proposed, I think, by Shaposhnikov and Tkachev), this scalar being a general singlet scalar in equilibrium (proposed by Kusenko) or out of equilibrium (proposed by me and collaborators). Hopefully all references on this type of production can be found in our 1502.01011. In general, this mechanism happens earlier than a possible resonant production and thus it can be computed without the need to go into the details of the QCD transision. However, also here a detailed computation is required to ensure that the resulting DM is not hot.

There is at least one more alternative production mechanism, which however only works "far" beyond the Standard Model, in the sense that you would need a new gauge interaction under which the sterile neutrinos transform non-trivially. In that case, they could enter thermal equilibrium and freeze out like WIMP-DM, however, this production would generically overclose the Universe which is why an additional entropy production is required to dilute things. The most detailed reference on this mechanism is probably 1205.0844 by Senjanovic and collaborators. However, note that this mechanism seems not to easily make friendship with BBN on quite general grounds.

At the moment we cannot decide which mechanism - if any - is the correct one. If the 3.5 keV line survives, it may however help to give us a clearer picture (under the assumption that keV neutrinos are the DM in the first place).

Fundamental particles may not be exactly (mathematical) point objects. They can have some extended structures, however small. In string theory a conserved quantity called R charge is often discussed. According to a paper by, Ori J. Ganor of UC Berkeley, fundamental particles may occupy a volume proportional to the R charge. If the particles are not point-like then their interactions are also not happening exactly at the same point, hence a small amount of non-locality is introduced. Therefore, I do not think non-locality always means action at a distance. It can also result from extended structures of elementary objects. 

Dear Biswajoy,

the neutrino to anti neutrino oscil is helicity suppressed, was first described in http://journals.aps.org/prd/abstract/10.1103/PhysRevD.23.1666 Regarding the counting and parametrization was exhaustively desrbed in http://journals.aps.org/prd/abstract/10.1103/PhysRevD.22.2227 and the symmetric presentation given there is BETTER than PDG for LNV processes. The PDG form is more convenient for standard oscillations only  CHEERS

You may see the following reference.

The Two Loop beta Function for a G(1) x G(2) Gauge Theory

D.R.T. Jones, Phys. Rev.  D25, 581 (1982).

Not everybody thinks that the standard Lambda-CDM theory of cosmic structureformation is a good idea. Recent patches to the theory propose that the strongest signal in the COBE/WMAP/PLANCK background maps is baryonic accoustic oscillations, but nobody has the courage to ask, "If the baryons dominate structure formation scenario, what about turbulence in the baryons?" Indeed many find that the background overall obeys fractal mathematics and is turbulent in origin at z = 1100. See papers by Carl H. Gibson (UCSD), Sylos Labini (Rome), and Bershadskii (Tel Aviv).

If that is true, and turbulence traces back to the era of atomic element formation, the standard assumption of a homogeneous Universe expanding in thermal equilibrium are in question, and in particular the Michael Turner and more recent calculations of thermal equilibrium elemant formation are questionable. For example, when the temperature of the hj-z universe was 10^7, local heating of a volume would produce atomic fusion with its very strong 10^12 temperature dependence. This would cause runaway fusion and solve the puzzle of the Spite minimum in atomic abundances, the fact that we do not find any Pop III stars at any redshift,  or anywhere in our Galaxy or Halo.

Cowan-Reines neutrino experiment. Here an electron anti-neutrino scatters a proton to produce a neutron and a positron. Reines got Nobel prize in 1995. Neutrinos are produced in a nuclear reactor and then aimed at a water tank. Positrons then emit gamma rays which are detected by photo multiplier tubes.

Dear Riaz, why not to ask people from BRAHMS directly? Other way to find an answer is to read carefully relevant published papers from BRAHMS. 

The most official answer I have always heard is that three is a minimum for CP violating phase. But not a strong argument.

Extra dimensions seem to like three generations, as it is known from compactification of superstrings, usually getting the number of families from some topological parameter. With extra dimensions, but without superstrings, some of my university teachers did a paper years ago: https://inspirehep.net/record/11555?ln=es (Phys.Rev. D26 (1982) 691-697)

My own guess is a very retorted mechanism: use the quarks as preons for the yet-to-be-found susy scalars. This is only possible with three generations.

In QFT Vacuum is the state of lowest energy. If this state is degenerate then picking up one of the degenerate lowest energy states (the states of physical vacuum) will lead to spontaneous symmetry breaking and then mass will be generated through Higg's mechanism.

No-we do know what the cosmological constant means and its effects in the solutions to the Einstein equations. We do not know of any matter that can exert negative pressure, so the question, whether with the cosmological constant alone it is possible to quantitatively describe spacetime is perfectly well-defined-and it does seem to work, as the supernova measurements indicate.

Article "Periodic quantum gravity and cosmology" predicts innumerable particles. The particles of standard model are shown to be just the tip of the iceberg. According to this theory, to look for the fundamental building block of the universe is not a very wise thing to do.

The most economical way (and for some the most natural way) to treat neutrino masses is to have both a Majorana and a Dirac mass term. The Dirac mass corresponds to a left handed (active) to right handed neutrino (sterile) transition and the Majorana mass term corresponds to a left-handed neutrino (active) to a right handed anti-neutrino (also active). What thus requires sterile neutrinos is the existence of a Dirac mass term like all other fermions of the Standard Model. The Majorana mass term violates fermion number conservation, but there is no such quantum number conservation in the Standard Model, it is only an *apparent* conservation due to the combination of charge conservation (for charged fermions) and angular momentum conservation (for massless neutrinos).

Now one has four states for each neutrino species or 12 for all neutrinos families. They mix in all possible ways due to the transitions that exist between left and right handedness, between flavours and between 'charge' (both being defined as the flavour and charge of the lepton produced in a weak interaction of the neutrino). The particle that propagate in vacuum are eigenstates of mass, spin and electric charge not of the above, so there appear "almost sterile" neutrinos which have a small active component.

The mixing is typically of the order of mD/mM (Dirac mass divided by Majorana mass) and in absence of knowledge of mD and mM it can be very small. The lightest mass state is are the 'mostly active' neutrinos (those we know) and the heavier ones are 'almost sterile'. The usual wisdom would be that mD is similar to the top quark mass, and that mM should be almost of the order of the GUT scale (10^10 GeV?) but really we dont know, especially if there are three families. This is then an open question: why should mD not be of the same size as the electron mass, or even much smaller since neutrinos have no charge? The lightest neutrino state has a mass of order mD^2/mM i.e. Theta.mD. In arXiv:1208.4607, Shaposhnikov and collaborators find that the lightest of the 'almost sterile' neutrinos could have a mass of 10 keV and have a coupling sufficient to be produced in the early universe; and now in equilibrium within stars, as fraction of the normal neutrino-producing reactions; and be sterile enough to decay very slowly. In this scenario the heavier 'almost sterile' neutrinos can have masses of the order of the electroweak scale (GeV to 100 GeV) and be possibly searched for in heavy flavour decays, or at a Z factory such as TLEP (see DOI 10.1007/JHEP01(2014)164 or arXiv:1308.6176v3 [hep-ex] ) . The article arXiv:1208.4607, explain also that the heavy 'almost sterile' neutrinos can be involved in generating the baryon asymmetry of the Universe.

This scheme (the vSM) is gaining popularity as the most economical scenario to explain both the dark matter and the baryon asymmetry of the universe. But of course it remains to explain what generates the Majorana mass term!

The curious thing is that for zero value of the Higgs scalar

it has more potential energy than a non-zero value of the

scalar. This non-zero value is the VEV. This situation is

depicted in the picture above. Then how do we define a vacuum ?

There are two alternatives.

1) Where the value of Higgs field is zero.

2) Where the energy of Higgs field is zero (minimum)

The first choice is true vacuum and second choice is

false vacuum. But universe has chosen to stay in the

false vacuum. Isn't it ironic ?

A VEV of a fermion will break Lorentz invariance, which is a good

space time symmetry. When you minimize inflaton potential it will

naturally pick up nonzero VEV due to couplings with doublet Higgs.

Here I assume that inflaton is a singlet scalar.

Otherwise if inflaton transforms under extra gauge groups, then to

break them you will require a VEV of inflaton.

MiniBooNE has an anomaly of well over 3 standard deviations which seems

to confirm LSND. However, it is less than the 5 standard deviation value

which is now taken for full confirmation. For both LSND and MiniBooNE,

the evidence can be best described as "evidence for", not "observation of".

I recently heard a lecture from prof Ruth Durrer (who unlike me, is a real expert on this) that the correlation function of the temperature fluctuations of the Cosmic Microwave Background is the best test for the inflation hypothesis. In particular it contains peaks that are strong indications of in-phase Alfven waves and the most natural explanation is that they were coherent and in causal contact before inflation. These lecture notes http://arxiv.org/abs/astro-ph/0109522 are quite old (for this subject anyway) but seem to contain the same kind of pictures for the correlation spectrum on figure 4.2 as I saw in the lecture although it seems that they are purely theoretic in the notes but are now reconstructed in detail by measurements from the Planck satellite.

Your question requires really an answer which is much too complicated for this thread. The CMBR anisotropy measurements are expressed in terms of power functions which are modeled within general relativity. They contain 6 free parameters (at least) the values of which are determined by a fit of the model (or models) to the power functions. Of course the curvature enters, but indirectly, it is not one of the free parameters.

Biswajoy,

As I understand, if one assumes that the dark matter is cold (CDM), it's considered to interact only through gravitation. Self-gravitation in CDM-only simulations produces the cuspy-halo problem, which is, I think, most often ignored.

The prior reference, http://en.wikipedia.org/wiki/Cuspy_halo_problem, concludes:

"One approach to solving the cusp-core problem in galactic halos is to consider models that modify the nature of dark matter; theorists have considered warm, fuzzy, self-interacting, and meta-cold dark matter, among other possibilities."

See: http://en.wikipedia.org/wiki/Warm_dark_matter

There was a calculation of s,t,u parameters involving one loop

calculations involving standard model fields. Those could

differentiate between different models of new physics. For example

supersymmetry was preferred over technicolor models.

In that spirit, some calculations should exist, which will tell

us about the chances of discovering superpartners or

other new physics candidates.

Biswajoy,

"Can the general theory of relativity help ?"

In "General relativistic dynamics applied to the rotation curves of galaxies," Carrick & Cooperstock argue that it is inherent limitations in Newtonian physics that produce the improper representations of mass distribution and resulting gravitational interactions that produce spiral galaxy gravitational evaluation results that seem to require the presence of dark matter.

See http://arxiv.org/abs/1101.3224, page 4:

"In dismissing general relativity in favour of Newtonian gravitational theory for the study of galactic dynamics, insufficient attention has been paid to the fact that the stars that compose the galaxies are essentially in motion under gravity alone (\gravitationally bound"). It had been known for many years, in fact since the time of Eddington, that the gravitationally bound problem in general relativity is an intrinsically non-linear problem even when the conditions are such that the field is weak and the motions are non-relativistic, at least in the time-dependent case. Most significantly, we have found that under these conditions, the general relativistic analysis of the problem is also non-linear for the stationary (non-time-dependent) case at hand. Thus the intrinsically linear Newtonian-based approach used prior to our work has been inadequate for the description of the galactic dynamics and Einstein's general relativity must be brought into the analysis within the framework of established gravitational theory."

However, I think that disk mass distributions' gravitational interactions can be properly represented using Newtonian dynamics. The methods of GTR may or may not better facilitate proper representations - I can't evaluate.

Again, a model of spiral galaxy rotation that employs Newtonian dynamics to obtain flat rotation curves from observed galactic structures can be found at http://arxiv.org/pdf/1104.3236v4.pdf.

Dark matter interacts only gravitationally and therefore in my opinion it is impossible to detect it by other interactions

I think you mean Rarita-Schwinger equation?

Redefining the phases of all quarks corresponds to premultiplying the CKM-matrix with a diagonal matrix of phases, and postmultiplying it with another diagonal matrix of phases. Altogether 6 parameters. However, one combination of phase transformations does not change the CKM-matrix (when you premultiply by a phase times the unit matrix, and postmultiply with the inverse phase times the unit matrix). Thus, there are only a 5-parameter way to change the CKM-matrix without changing the physics of it, leaving 9-5=4 physical parameters.

For F families (generations) of quarks there would be F^2 -(2F-1) = (F-1)^2 physical parameters in the corresponding matrix.

You are not reporting a result with a smaller error than the LC. If your least count is 0.1, then you measure a value of 1, then the real value could be anywhere between 0.95 and 1.05, otherwise your apparatus will measure 0.9 or 1.1. The apparatus is effectively using the round function (as opposed to the floor or ceiling functions).

You can measure a value of 0, which really means a value between -0.05 and +0.05, but there is no physical meaning. If you takes lots of measurements of the same quantity then the error will decrease by a factor of 1 / sqrt( n )

Dear Sergio,

in general grounds the saturation of the Froissart bound at asymptotic energies is a consequence of the maximal (allowed) absorption of partial waves in the momentum angular series, which has the upper limit L_{max} = c \sqrt{s} lns (with c constant) . When complete absorption takes place, that is, when the inelasticity \eta(s,b=0)->0 at s->infinity, the impact parameter distributions (elastic, inelastic and total) recover the (simplest) geometrical limit, where the ratios elastic to total and inelastic to total cross section becomes 1/2 as s-> infinity (the so-called black disk limit). Under these simple arguments, the maximal energy saturation regime (the ln^2 s behaviour of the cross sections) means simply the saturation of the unitarity limit asymptotically. On the other hand, in regard to the log-squared energy dependence of the total cross section, several issues have been currently debated in the literature, i.e: (i) does "true QCD" play a role in the general hypothesis underlying the derivation of the FM bound (and leading to \sigma_{tot} < Cln^2 s)?; (ii) a faster rise of cross sections is forbidden by general principles like unitarity?; (iii) is a faster rise precluded by the present experimental information on the total cross sections. For your reference i forward two in-depth theoretical investigations on the subject (1 and 2) and a phenomenological discussion based on fits to the present experimental data (3):

1) How robust is the Froissart bound?: arXiv:1104.5314

2) What is the real meaning of the Froissart bound?: arXiv:1208.4304

3) On the rise of proton-proton cross sections at high-energies: arXiv:1208.3456

With kind regards,

Daniel.

Putting a sharp cut-off in momentum space can be thought of as replacing the continuum space time with some sort of lattice, which does not posses poinacare invariance.

Wei Fan is right - apart from an incorrect spelling of "leptons", and apart from a lack of precision: It is only the W- and the Z- gauge bosons mediating the weak interactions that acquire a mass via the Higgs mechanism; the photon and the gluons do not!

The real question is, in the end, why such text-book questions/answers are debated on a network like this. I think it would be better if one went to the library and read an appropriate book to find out what the correct answers are!

To complete Torsten'answer : please do not forget that the number of candidates is small especially in the higgs decay to 4 leptons and reconstructed over a standard model background which can make the invariant mass distribution fluctuate significantly. With our present luminosity the chance to observe what we see (or a higher fluctuation) is sizeable (of the order of a %) and forbids to draw any strong conclusion. We really need extra data that will not come before 2014 at the earliest. La patience est mère de toutes les vertus.

What scientists mean by "a positron moving forward in time is same as an electron going backward in time" is that the mathematical expression describing the motion of the two particles is exactly same except for the direction of time. Reverse can be said, like you can say that "an electron moving forward in time is same as a a positron going backward in time". What they talk here about is the mathematical symmetry (of equation of motion) that come in while describing the motion of the two particles. That doesn't mean that any positron that we detect is coming from the future. It is just a mathematical description, and is not what happens at the observational scale.