IMPLICATIONS OF A MODEL WITH A LONGER TAU LIFE-TIME

1992 ◽  
Vol 07 (31) ◽  
pp. 2921-2930
Author(s):  
R. FOOT ◽  
H. LEW
Keyword(s):  
Standard Model ◽  
General Model ◽  
Life Time ◽  
Tau Lepton ◽  
Standard Cosmology ◽  
The Standard Model ◽  
Weyl Fermion

It is possible that the tau lepton may have a longer life-time than that predicted by the Standard Model. The simplest extension to the Standard Model incorporating a longer tauon life-time involves the addition of a gauge singlet Weyl fermion. We consider the most general model of this kind and evaluate the experimental constraints on the various parameters of this model. We show that the model is consistent with the standard cosmology model for a range of parameters. We then examine possible signatures of the model in certain experiments searching for heavy neutral leptons.

scholarly journals The anomalous 21-cm absorption at high redshifts

2021 ◽  
Vol 81 (3) ◽  
Author(s):  
Fulvio Melia
Keyword(s):  
Standard Model ◽  
Supernova Remnants ◽  
First Generation ◽  
Neutral Hydrogen ◽  
Absorption Feature ◽  
X Rays ◽  
Spin Temperature ◽  
Standard Cosmology ◽  
The Standard Model ◽  
Adiabatic Cooling

AbstractThe EDGES collaboration has reported the detection of a global 21-cm signal with a plateau centered at 76 MHz (i.e., redshift 17.2), with an amplitude of $$500^{+200}_{-500}$$ 500 - 500 + 200  mK. This anomalous measurement does not comport with standard cosmology, which can only accommodate an amplitude $$\lesssim 230$$ ≲ 230  mK. Nevertheless, the line profile’s redshift range ($$15\lesssim z\lesssim 20$$ 15 ≲ z ≲ 20 ) suggests a possible link to Pop III star formation and an implied evolution out of the ‘dark ages.’ Given this tension with the standard model, we here examine whether the observed 21-cm signal is instead consistent with the results of recent modeling based on the alternative Friedmann–Lemaître–Robertson–Walker cosmology known as the $$R_{\mathrm{h}}=ct$$ R h = c t universe, showing that – in this model – the CMB radiation might have been rethermalized by dust ejected into the IGM by the first-generation stars at redshift $$z\sim 16$$ z ∼ 16 . We find that the requirements for this process to have occurred would have self-consistently established an equilibrium spin temperature $$T_{\mathrm{s}}\approx 3.4$$ T s ≈ 3.4 K in the neutral hydrogen, via the irradiation of the IGM by deep penetrating X-rays emitted at the termination shocks of Pop III supernova remnants. Such a dust scenario has been strongly ruled out for the standard model, so the spin temperature ($$\sim 3.3$$ ∼ 3.3 K) inferred from the 21-cm absorption feature appears to be much more consistent with the $$R_{\mathrm{h}}=ct$$ R h = c t profile than that implied by $$\Lambda $$ Λ CDM, for which adiabatic cooling would have established a spin temperature $$T_\mathrm{s}(z=17.2)\sim 6$$ T s ( z = 17.2 ) ∼ 6 K.

General Model Independent Searches for Physics Beyond the Standard Model

2020 ◽  
Author(s):  
Saranya Samik Ghosh ◽  
Thomas Hebbeker ◽  
Arnd Meyer ◽  
Tobias Pook
Keyword(s):  
Standard Model ◽  
General Model ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Model Independent

THE TAU-LEPTON AND TESTS OF THE STANDARD MODEL

1993 ◽  
Vol 08 (26) ◽  
pp. 2491-2496 ◽  
Author(s):  
MARK A. SAMUEL
Keyword(s):  
Standard Model ◽  
Tau Lepton ◽  
Tau Neutrino ◽  
The Standard Model ◽  
B Factory

Using a new value for the mass of the tau-lepton we reconsider various tests of the Standard Model (SM) for the tau. The agreement with the SM is much improved. All tests agree within 1.2σ or smaller and the so-called “tau-lifetime problem” has disappeared. We also obtain bounds on the mass of the tau-neutrino. It is shown that an improved bound [Formula: see text] MeV at 95% C.L. can be obtained at the τ-charm factory in Spain or at a proposed B-factory.

ELECTROWEAK THEORY AND THE NEUTRINO-MASS AND NEUTRINO-OSCILLATION QUESTIONS

2007 ◽  
Vol 22 (12) ◽  
pp. 853-865 ◽  
Author(s):  
G. ZIINO
Keyword(s):  
Standard Model ◽  
Neutrino Oscillation ◽  
Neutrino Mass ◽  
Parity Violation ◽  
Crucial Role ◽  
Tau Lepton ◽  
Electroweak Theory ◽  
Mass Eigenstates ◽  
The Standard Model

It is shown that both conjectures of neutrino mass and neutrino oscillation can be made really well-grounded within the Standard Model provided that one adopts a recent new version of the electroweak scheme spontaneously giving also a fundamental explanation for the so-called "maximal parity-violation" effect. A crucial role is played by the prediction of two distinct, scalar and pseudoscalar, replicas of (electron, muon, and tau) lepton numbers that could fully account for an actual non-coincidence between neutrino mass-eigenstates and gauge-eigenstates.

scholarly journals Leptonic decays of the tau lepton

2019 ◽  
Vol 212 ◽  
pp. 08004 ◽  
Author(s):  
Matteo Fael
Keyword(s):  
Standard Model ◽  
Weak Interaction ◽  
Tau Lepton ◽  
Decay Modes ◽  
Leptonic Decays ◽  
The Standard Model

In these proceedings we review the SM prediction for the tau leptonic decays, including the radiative $ (\tau \to \ell \lambda \nu \bar \nu ) $ and the five-body $ (\tau \to \ell \ell '\ell '\nu \bar \nu ) $ decay modes, which are among the most powerful tools to study precisely the structure of the weak interaction and to constrain possible contributions beyond the V–A coupling of the Standard Model.

scholarly journals Beyond the Standard Model

2020 ◽  
pp. 455-517
Author(s):  
Eliezer Rabinovici
Keyword(s):  
Quantum Mechanics ◽  
Standard Model ◽  
Life Time ◽  
Full Detail ◽  
Proton Antiproton ◽  
Hadronic Collider ◽  
Electron Positron ◽  
The Standard Model ◽  
Almost All ◽  
New Generation

AbstractStarting sometime in 2008/2009 one expects to be able to take a glimpse at physics at the TeV scale. This will be done through the Large Hadronic Collider (LHC) at CERN, Geneva. It will be a result of an unprecedented coordinated international scientific effort. This chapter is written in 2007. It is essentially inviting disaster to spell out in full detail what the current various theoretical speculations on the physics are, as well motivated as they may seem at this time. What I find of more value is to elaborate on some of the ideas and the motivations behind them. Some may stay with us, some may evolve and some may be discarded as the results of the experiments unfold. When the proton antiproton collider was turned on in the early eighties of the last century at Cern the theoretical ideas were ready to face the experimental results in confidence, a confidence which actually had prevailed. The emphasis was on the tremendous experimental challenges that needed to be overcome in both the production and the detection of the new particles. As far as theory was concerned this was about the physics of the standard model and not about the physics beyond it. The latter part was left safely unchallenged. That situation started changing when the large electron positron (LEP) collider experiments also at Cern were turned on as well the experiments at the Tevatron at Fermilab. Today it is with rather little, scientifically based, theoretical confidence that one is anticipating the outcome of the experiments. It is less the method and foundations that are tested and more the prejudices. It is these which are at the center of this chapter. Some claim to detect over the years an oscilatory behavior in the amount of conservatism expressed by leaders in physics. The generation in whose life time relativity and quantum mechanics were discovered remained non-conservative throughout their life. Some of the latter developed eventually such adventurous ideas as to form as a reaction a much more conservative following generation. The conservative generation perfected the inherited tools and has uncovered and constructed the Standard Model. They themselves were followed by a less conservative generation. The new generation was presented with a seemingly complete description of the known forces. In order to go outside the severe constraints of the Standard Model the new generation has drawn upon some of the more adventurous ideas of the older generation as well as created it own ideas. In a way almost all accepted notions were challenged. In the past such an attitude has led to major discoveries such as relativity and quantum mechanics. In some cases it was carried too far, the discovery of the neutrino was initially missed as energy conservation was temporarily given up.

ELECTRIC CHARGE QUANTIZATION AND VECTOR-LIKE FERMIONS

1990 ◽  
Vol 05 (24) ◽  
pp. 1947-1949 ◽  
Author(s):  
ROBERT FOOT
Keyword(s):  
Standard Model ◽  
Electric Charge ◽  
Life Time ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Simple Method ◽  
Gauge Models ◽  
Flavor Changing ◽  
Charge Quantization ◽  
The Standard Model

In extended gauge models with gauge group G, electric charge quantization is not always an automatic consequence of the consistency of the theory. Exotic fermions which have SU (3) ⊗ SU (2) L ⊗ U (1) invariant mass terms can provide a simple method for preserving the charge quantization feature of the standard model. This procedure is applied to the segregated isospin model.This approach indicates that precision measurements of the τ-lepton life-time and rare flavor-changing neutral processes may provide the first indications of new physics beyond the standard model.

scholarly journals New method for beyond the Standard Model invisible particle searches in tau lepton decays

2020 ◽  
Vol 102 (11) ◽  
Author(s):  
E. De La Cruz-Burelo ◽  
A. De Yta-Hernandez ◽  
M. Hernandez-Villanueva
Keyword(s):  
Standard Model ◽  
Tau Lepton ◽  
New Method ◽  
Beyond The Standard Model ◽  
The Standard Model ◽  
Invisible Particle ◽  
Lepton Decays

A TESTABLE MODEL OF A 17 keV TAU NEUTRINO

1992 ◽  
Vol 07 (06) ◽  
pp. 459-465
Author(s):  
DANIEL NG
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Life Time ◽  
Local Symmetry ◽  
Global Symmetry ◽  
Tau Neutrino ◽  
The Standard Model ◽  
Near Future ◽  
Breaking Scale ◽  
Testable Model

We discuss an extension of the standard model with a local symmetry of Le−Lμ and a global symmetry of Lτ to incorporate a 17 keV Dirac tau neutrino. A massive neutral gauge boson (AX) and a majoron (J) are present by breaking the symmetries spontaneously. The tau neutrino, with a life-time of the order 10−3 s, will decay by emitting an electron and a majoron. Tau will also decay into an electron and a majoron with a branching ratio as large as 10−4. The breaking scale of Le−Lμ symmetry can be as low as 700 GeV. Hence, AX can be produced in LEP II in the near future.

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