# Recent content by Barmecides

1. ### SU(3)xU(1) breaking exercise?

Hello, don't you have similar example from dynamical breaking of chiral QCD ?
2. ### Higgs excluded at 170 GeV (press release 4 August)

Hello, if you look at the bottom figure from this web page : http://tevnphwg.fnal.gov/results/SM_Higgs_Winter_08hepex/ you will see a plot drawing 95% exclusion limit/SM. As long as this number is > 1, you cannot exclude the point. To summarize this plot, the higher is this number, the...
3. ### Detecting Quarks

When you shoot two protons against each other, if protons were elementary particles, you would observed two scattered protons after the collisions (I'm simplifying). Instead of that, we observe what we call two "jets" back to back + some remnants. Jet is a collimated flux of hadrons particles...
4. ### Dark Matter and supersymmetry

Be careful dark matter and dark energy are different. If I remember well, dark matter is roughtly ~ 22% of universe mass, and dark energy ~ 73%. Supersymmetry provide indeed a candidate for "cold" dark matter (heavy matter with low speed). usually, because there are plenty of supersymmetry...
5. ### Higgs excluded at 170 GeV (press release 4 August)

Hello, it is much easier to exclude an Higgs at 170 GeV than at 120 GeV for both Tevatron and LHC. Just because around that energy H -> WW* which is much easier to check than low energy signatures. High energy higgs (> 170 GeV) are also quite easy to discover/exclude due to H -> ZZ -> llll...
6. ### Long-awaited braid-matter paper (Bilson-Thompson, Hackett, Kauffman, Smolin)

Hello Coin, this way of suggesting things as natural look to me quite antropic... In that case, why not invoking some underlying group theory telling us how many families we should expect, it will be as natural as infinite.
7. ### Energy reconstruction in calorimeter

Hello Kenith, you might be interested by this (rather old) paper about jets building at Tevatron : http://arxiv.org/PS_cache/hep-ex/pdf/0005/0005012v2.pdf In particular, in section 2, they explains with drawings collinear and infrared instabilities on jets.
8. ### Long-awaited braid-matter paper (Bilson-Thompson, Hackett, Kauffman, Smolin)

Hello, you can just look at existing pdg limits : m_nu < 2 eV If there is a neutral heavy leptons m > 90.3 GeV if Dirac m > 80.5 GeV if Majorana So if there is a standard 4th generation neutrino, there is a big mass gap between 3rd and 4th generation. Then, that could be sterile...
9. ### Soft particle

Hello, depends on the context. But it can be "soft Pt particle" ! Gamma can be the width of the resonance of an unstable particle (like a Z boson). Within the scheme c=h=1, you can choose arbritraly to express lengths, times, energies with a single unit (like GeV).
10. ### What quanta mediates the nuclear forces?

Ok thanks... Looking back to my old courses, indeed I found something like \frac{\delta^{ab}}{k^{2} - i\epsilon}(g_{\mu\nu} - (1-\varsigma)(\frac{k^{\mu}k^{\nu}}{k^{2}}))
11. ### What quanta mediates the nuclear forces?

Hello Jon, thanks for the link. Looking a bit at the article, I have a naive question : what does the assumption \lambda^{a}D^{ab}\lambda^{b} \rightarrow \lambda^{a}G(x-y)\lambda^{a} come from ? Is it this line which means that we have colorless objects as a first assumption ?
12. ### What quanta mediates the nuclear forces?

Can we really go through this analogy between nuclear forces and Van der Waals as we often hear ? I mean I understand there is a charge cancellation in both cases and so we are only sensitive to higher order effects. But, as QCD is highly non-perturbative in this energy domain contrary to QED...
13. ### What is charge? Why do fundamental particles possess it?

Yes why ? The yukawa coupling between higgs and fermions do not look really quantized. Why electric charge is ? And why is it such that it cancels prefectly eg anomalies ? Can it be explained in GUT theories ?
14. ### Left spinors in GUT theories

I do not know much about GUT theories, but it might be related to the fact we often have majorana particles and it is easier the formulate the them with left spinor, anti-particles and conjugate than with left and right spinors ? In any case, if you learn about the answer, I am interested...
15. ### Really a virtual particle sea?

Sorry marlon, this was a mistake in writing. I was only meaning that "I have some idea of what is a "virtual" particle in perturbative QFT" and only in perturbative QFT because I think this is an artefact of perturbative approximation of quantum mecanics. But, if you can proove the...