Inverse Seesaw, dark matter and the Hubble tension Fernandez-Martinez, E.; Pierre, M.; Pinsard, E. ...
The European physical journal. C, Particles and fields,
10/2021, Letnik:
81, Številka:
10
Journal Article
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We consider the inverse Seesaw scenario for neutrino masses with the approximate Lepton number symmetry broken dynamically by a scalar with Lepton number two. We show that the Majoron associated to ...the spontaneous symmetry breaking can alleviate the Hubble tension through its contribution to
Δ
N
eff
and late decays to neutrinos. Among the additional fermionic states required for realizing the inverse Seesaw mechanism, sterile neutrinos at the keV-MeV scale can account for all the dark matter component of the Universe if produced via freeze-in from the decays of heavier degrees of freedom.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Heavy neutral leptons are motivated by several extensions of the Standard Model and their presence induces modifications in the lepton mixing matrix, including new Dirac and Majorana CP violating ...phases. It has been recently shown that these phases play an important role in lepton number and lepton flavour violating decays and transitions, with a striking impact for the predicted rates of certain observables. In this work, we now consider the potential role of the heavy neutral fermions and of the new CP violating phases in Higgs and
Z
-boson lepton flavour violating decays
H
,
Z
→
ℓ
α
±
ℓ
β
∓
, as well as in the corresponding CP asymmetries. In order to allow for a thorough analysis, we derive the full analytical expressions of the latter observables, taking into account the effect of the (final state) charged lepton masses. A comprehensive exploration of lepton flavour violating
Z
and Higgs decays confirms that these are very sensitive to the presence of the additional heavy neutral leptons. Moreover, the new CPV phases have a clear impact on the decay rates, leading to both destructive and constructive interferences. Interestingly, in the
μ
τ
sector, the
Z
→
ℓ
α
±
ℓ
β
∓
rates are within reach of FCC-ee, with associated CP asymmetries that can potentially reach up to 20–30%.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We study lepton flavour universality violation in SM boson decays in low-scale seesaw models of neutrino mass generation, also addressing other electroweak precision observables. We compute the ...electroweak next-to-leading order corrections, which turn out to be important – notably in the case of the invisible decay width of the
Z
boson, for which the corrections can be as large as the current experimental uncertainty. As a well-motivated illustrative study case, we choose a realisation of the Inverse Seesaw mechanism, and discuss the complementary role of lepton flavour conserving, lepton flavour violating and precision observables, both in constraining and in probing such models of neutrino mass generation. Our findings suggest that invisible
Z
decays are especially important, potentially at the origin of the most stringent constraints for certain regimes of the Inverse Seesaw (while complying with charge lepton flavour violation and other electroweak precision tests). We also discuss the probing power of the considered observables in view of the expected improvement in experimental precision at FCC-ee.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The apparent tensions emerging from the comparison of experimental data of the anomalous magnetic moments of the muon and electron to the Standard Model predictions (
Δ
a
μ
,
e
) could be interpreted ...as a potential signal of New Physics. Models encompassing a light vector boson have been known to offer a satisfactory explanation to
Δ
a
μ
, albeit subject to stringent experimental constraints. Here we explore a minimal extension of the Standard Model via a leptophilic vector boson
Z
′
, under the hypothesis of strictly flavour-violating couplings of the latter to leptons. The most constraining observables to this ad-hoc construction emerge from lepton flavour universality violation (in
Z
and
τ
decays) and from rare charged lepton flavour violating transitions. Once these are accommodated, one can saturate the tensions in
Δ
a
μ
, but
Δ
a
e
is predicted to be Standard Model-like. We infer prospects for several observables, including leptonic
Z
decays and several charged lepton flavour violating processes. We also discuss potential signatures of the considered
Z
′
at a future muon collider, emphasising the role of the
μ
+
μ
-
→
τ
+
τ
-
forward-backward asymmetry as a key probe of the model.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A fully fibered microwave-optical source at 1.5 µm is studied experimentally. It is shown that the beat note between two orthogonally polarized modes of a distributed-feedback fiber laser can be ...efficiently stabilized using an optical phase-locked loop. The pump-power-induced birefringence serves as the actuator. Beat notes at 1 GHz and 10 GHz are successfully stabilized to a reference synthesizer, passing from the 3 kHz free-running linewidth to a stabilized sub-Hz linewidth, with a phase noise as low as -75 dBc/Hz at 100 Hz offset from the carrier. Such dual-frequency stabilized lasers could provide compact integrated components for RF and microwave photonics applications.
The radiation response of distributed feedback (DFB) Bragg gratings written with continuous wave (CW) UV or IR femtosecond lasers in Ge-doped fibers was studied up to the total ionizing dose of 1 ...kGy(SiO 2 ) since these components are aimed to be used as the laser cavity for space applications. We demonstrated that the ultranarrow passband peaks shift of the same quantity of their Bragg peak since the cavity length cannot change at such low doses. Moreover, the studied DFBs based on type I-UV and type I-IR FBGs show a shift of 5 and 3 pm, respectively, at 1 kGy. These are very encouraging results for their use in real-space applications, but better performances could be obtained by inscribing DFBs based on type II-IR gratings in F-doped fibers since these latter show generally better radiation resistance.
We present an approach coupling a limited experimental number of tests with numerical simulations regarding the design of radiation-hardened (RH) rare earth (RE)-doped fiber amplifiers. Radiation ...tests are done on RE-doped fiber samples in order to measure and assess the values of the principal input parameters requested by the simulation tool based on particle swarm optimization (PSO) approach. The proposed simulation procedure is validated by comparing the calculation results with the measured degradations of two amplifiers made with standard and RH RE-doped optical fibers, respectively. After validation, the numerical code is used to theoretically investigate the influence of some amplifier design parameters on its sensitivity to radiations. Simulations show that the RE-doped fiber length used in the amplifier needs to be adjusted to optimize the amplifier performance over the whole space mission profile rather than to obtain the maximal amplification efficiency before its integration in the harsh environment. By combining this coupled approach with the newly-developed RH RE-doped fibers, fiber-based amplifiers nearly insensitive to space environment may be designed in the future.
We investigated the behavior of a new class of erbium-doped fiber amplifier (EDFA) when exposed to 63 MeV protons. The EDFA is designed with a radiation hardened hole-assisted carbon coated (HACC) Er ...3 + -doped optical fiber. The particular structure of this HACC fiber allows to permanently incorporate an optimal amount of D 2 or H 2 gases into its core, reducing its radiation sensitivity without degrading the EDFA performances. Irradiations up to a fluence of 7.5 ×10 11 p/cm 2 confirm the excellent tolerance of this HACC-EDFA component. It exhibits a limited decrease of ~ 0.6 dB of its ~ 27 dB gain for this fluence corresponding to an ionization dose of 100 krad(Si). Such a device can then survive to the radiative environments associated with both today's space missions and future more challenging applications.
The so-called Faster is Slower (FIS) effect is observed in some particular real-life or experimental situations. In the context of an evacuation process, it expresses that increasing the speed (or, ...more generally, the competitiveness) of individuals may induce a reduction of the flow through the exit door. We propose here a parameter-free model to reproduce and investigate this effect (more precisely its backward “Slower is Faster” equivalent). In spite of its non-smooth character, which makes it difficult to analyze, this granular approach is based on very basic ingredients in terms of behavior. In its native, purely asocial version, individuals are represented by hard-discs, each of which has a desired velocity, and the actual velocity is built as the projection of this field on the set of admissible velocities (which respect the non-overlapping constraints). We implement the slower effect by introducing here an extra step to account for the fact that individuals refrain from pushing, and therefore tend to reduce their desired velocity accounting for the velocities of people upfront. The present paper has two objectives: establish the relevance of this model by showing that it satisfactorily reproduces various empirical effects in highly crowded evacuations with various levels of competitiveness, and explore how it can be implemented to recover and explain the FIS effect. In this spirit, we confront this Inhibition-Based (IB) model to experimental data, focusing on the Faster is Slower effect. We show in particular that this approach makes it possible to accurately recover the effect of competitiveness upon power-law distributions of time lapses which have been experimentally observed. We also study the effect of mixed behaviors, by introducing a two-population model using both approaches. We investigate in particular the effect upon evacuation efficiency of the ratio between competitive agents and non-competitive ones. In a similar context, we investigate the role of an obstacle placed upstream the exit upon evacuation efficiency.
•Numerical investigation of the Faster is Slower effect based on a parameter free model.•Integration of an inhibition tendency of polite pedestrians.•Numerical evidence of the fluidizing role of an obstacle upstream the exit during evacuation.•Numerical recovering of an experimental power law for time lapses.
The apparent tensions emerging from the comparison of experimental data of the anomalous magnetic moments of the muon and electron to the Standard Model predictions ( Formula omitted) could be ...interpreted as a potential signal of New Physics. Models encompassing a light vector boson have been known to offer a satisfactory explanation to Formula omitted, albeit subject to stringent experimental constraints. Here we explore a minimal extension of the Standard Model via a leptophilic vector boson Formula omitted, under the hypothesis of strictly flavour-violating couplings of the latter to leptons. The most constraining observables to this ad-hoc construction emerge from lepton flavour universality violation (in Z and Formula omitted decays) and from rare charged lepton flavour violating transitions. Once these are accommodated, one can saturate the tensions in Formula omitted, but Formula omitted is predicted to be Standard Model-like. We infer prospects for several observables, including leptonic Z decays and several charged lepton flavour violating processes. We also discuss potential signatures of the considered Formula omitted at a future muon collider, emphasising the role of the Formula omitted forward-backward asymmetry as a key probe of the model.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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