What if it were possible to observe the fundamental building blocks upon which the Universe is based? All you would need is a massive particle accelerator, an underground facility large enough to cross a border between two countries, and the ability to accelerate particles to the point where they annihilate each other — releasing energy and mass which you could then observe with a series of special monitors.
This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Standard Model fails to explain neutrino oscillations, dark matter, and baryon asymmetry of the Universe.
All these problems can be solved with three sterile neutrinos added to SM. Quite remarkably, if sterile neutrino masses are well below the electroweak scale, this modification—Neutrino Minimal Standard Model MSM —can be tested experimentally.
We discuss a new experiment on search for decays of GeV-scale sterile neutrinos, which are responsible for the matter-antimatter asymmetry generation and for the active neutrino masses. If lighter than 2 GeV, these particles can be produced in decays of charm mesons generated by high energy protons in a target, and subsequently decay into SM particles.
To fully explore this sector of MSM, the new experiment requires data obtained with at least incident protons on target achievable at CERN SPS in future and a big volume detector constructed from a large amount of identical single modules, with a total sterile neutrino decay length of few kilometers.
The preliminary feasibility study for the proposed experiment shows that it has sensitivity which may either lead to the discovery of new particles below the Fermi scale—right-handed partners of neutrinos—or rule out seesaw sterile neutrinos with masses below 2 GeV.
Introduction The discovery of neutrino oscillations provides an undisputed signal that the Standard Model SM of elementary particles is not complete. However, what kind of new physics it brings to us remains still unclear: An attractive possibility is the extension of the SM by three right-handed neutrinos, making the leptonic sector similar to the quark one, see Figure 1.
Particle content of the SM and its minimal extension in neutrino sector. In the SM left the right-handed partners of neutrinos are absent. The masses of new leptons remain largely unknown.
Ever since the discovery of the Higgs Boson in , the Large Hadron Collider has been dedicated to searching for the existence of physics that go beyond the Standard pfmlures.com this end, the Large. A number of significant scientific events occurred in , including the discovery of numerous Earthlike exoplanets, the development of viable lab-grown ears, teeth, livers and blood vessels, and the atmospheric entry of the most destructive meteor since The year also saw successful new treatments for diseases such as HIV, Usher . The observation was made in a data sample of proton—proton collisions delivered in by CERN's Large Hadron Collider (LHC) operating at a centre-of-mass energy of 7 TeV.
The admitted region is sketched in Figure 2. The admitted values of the Yukawa couplings of sterile neutrinos as a function of their seesaw Majorana masses. Independently on their mass, the new Majorana leptons can explain oscillations of active neutrinos.
So, an extra input is needed to fix their mass range. It can be provided by the LHC experiments. This number is remarkably close to the lower limit on the Higgs mass coming from the requirement of the absolute stability of the electroweak vacuum and from Higgs inflation, and to prediction of the Higgs mass from asymptotic safety of the Standard Model see detailed discussion in [ 1 ] and in a proposal submitted to European High Energy Strategy Group by Bezrukov et al.
The existence of the Higgs boson with this particular mass tells that the Standard Model vacuum is stable or metastable with the life-time exceeding that of the Universe. The SM in this case is a valid effective field theory up to the Planck scale, and no new physics is required above the Fermi scale from this point of view.
The solution of the hierarchy problem does not require in fact the presence of new particles or new physics above the Fermi scale. Moreover, the absence of new particles between the electroweak and Planck scales, supplemented by extra symmetries such as the scale invariance may itself be used as an instrument towards a solution of the problem of stability of the Higgs mass against radiative corrections for detailed arguments see [ 3 — 5 ].
Even regardless the hierarchy problem, it is clear that the Standard Model of elementary particles is not complete. It is in conflict with several observations. These are nonzero neutrino masses and oscillations discussed above, the excess of matter over antimatter in the Universe, and the presence of nonbaryonic dark matter.
Guided by the arguments steaming from alternative solutions to the hierarchy problem it is natural to ask whether the observational problems of the SM can be solved by new physics below the Fermi scale.
And the answer is affirmative: The lightest of the three new leptons is expected to have a mass from keV to keV and plays the role of the dark matter particle see detailed discussion in [ 6 ] and in a proposal submitted to European High Energy Strategy Group by Boyarsky et al.
Two other neutral fermions are responsible for giving masses to ordinary neutrinos via the seesaw mechanism at the electroweak scale and to creation of the baryon asymmetry of the Universe.
The masses of these particles and their couplings to ordinary leptons are constrained by particle physics experiments and cosmology. Two leptons should be almost degenerate, forming thus nearly Dirac fermion this is coming from the requirement of successful baryogenesis.
For comparison, we show in Figure 3 the summary of different possibilities for the masses of Majorana leptons. This table shows whether a given choice of the mass of sterile neutrinos can explain neutrino masses and oscillations, accommodate eV neutrino anomalies, lead to baryogenesis, provide a dark matter candidate, ensure the stability of the Higgs mass against radiative corrections, and is directly searched at some experiments.
A lot of experimental efforts were devoted to the direct search of Majorana neutral leptons in the past [ 8 — 16 ]. No new particles were found, but several constraints on their mixing angles with ordinary leptons were derived.
The interest to these searches declined considerably at nineties, most probably due to the theoretical prejudice that the masses of Majorana leptons should be associated with the Grand Unified scale GeV [ 17 — 20 ], making their direct search impossible.The ATLAS experiment was proposed in its current form in , and officially funded by the CERN member countries in Additional countries, universities, and .
December 20, by Achintya Rao, Cern, CERN J/ψ-φ mass spectrum in a sample of B+ → J/ψφK decays. The two prominent structures are shown in red compared the expected background shown in . To fully explore this sector of MSM, the new experiment requires data obtained with at least incident protons on target (achievable at CERN SPS in future) and a big volume detector constructed from a large amount of identical single modules, with a total sterile neutrino decay length of few kilometers.
The Higgs boson was postulated nearly five decades ago within the framework of the standard model of particle physics and has been the subject of numerous searches at accelerators around the world.
The data sample corresponds to an integrated luminosity of 3 fb−1 collected in and The τ leptons are reconstructed through the decay τ−→π−π+π−ντ. An Experiment Revealing the Decay of Beauty Meson at CERN in and words. 2 pages. Understanding the Ideal pH in the Human Body. words.
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