scholarly journals Detecting long-lived multi-charged particles in neutrino mass models with MoEDAL

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Martin Hirsch ◽  
Rafał Masełek ◽  
Kazuki Sakurai

AbstractA certain class of neutrino mass models predicts long-lived particles whose electric charge is four or three times larger than that of protons. Such particles, if they are light enough, may be produced at the LHC and detected. We investigate the possibility of observing those long-lived multi-charged particles with the MoEDAL detector, which is sensitive to long-lived particles with low velocities ($$\beta $$ β ) and a large electric charge (Z) with $$\Theta \equiv \beta /Z \lesssim 0.15$$ Θ ≡ β / Z ≲ 0.15 . We demonstrate that multi-charged scalar particles with a large Z give three-fold advantage for MoEDAL; reduction of $$\Theta $$ Θ due to strong interactions with the detector, and enhancement of the photon-fusion process, which not only increases the production cross-section but also lowers the average production velocity, reducing $$\Theta $$ Θ further. To demonstrate the performance of MoEDAL on multi-charged long-lived particles, two concrete neutrino mass models are studied. In the first model, the new physics sector is non-coloured and contains long-lived particles with electric charges 2, 3 and 4. A model-independent study finds MoEDAL can expect more than 1 signal event at the HL-LHC ($$L = 300$$ L = 300 $$\hbox {fb}^{-1}$$ fb - 1 ) if these particles are lighter than 600, 1100 and 1430 GeV, respectively. These compare with the current ATLAS limits 650, 780 and 920 GeV for $$L = 36$$ L = 36 $$\hbox {fb}^{-1}$$ fb - 1 . The second model has a coloured new physics sector, which possesses long-lived particles with electric charges 4/3, 7/3 and 10/3. The corresponding MoEDAL’s mass reaches at the HL-LHC are 1400, 1650 and 1800 GeV, respectively, which compare with the current CMS limits 1450, 1480 and 1510 GeV for $$L = 36$$ L = 36 $$\hbox {fb}^{-1}$$ fb - 1 . In a model-specific study we explore the parameter space of neutrino mass generation models and identify the regions that can be probed with MoEDAL at the end of Run-3 and the High-Luminosity LHC.

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
John Gargalionis ◽  
Raymond R. Volkas

Abstract Building UV completions of lepton-number-violating effective operators has proved to be a useful way of studying and classifying models of Majorana neutrino mass. In this paper we describe and implement an algorithm that systematises this model-building procedure. We use the algorithm to generate computational representations of all of the tree-level completions of the operators up to and including mass-dimension 11. Almost all of these correspond to models of radiative neutrino mass. Our work includes operators involving derivatives, updated estimates for the bounds on the new-physics scale associated with each operator, an analysis of various features of the models, and a look at some examples. We find that a number of operators do not admit any completions not also generating lower-dimensional operators or larger contributions to the neutrino mass, ruling them out as playing a dominant role in the neutrino-mass generation. Additionally, we show that there are at most five models containing three or fewer exotic multiplets that predict new physics that must lie below 100 TeV. Accompanying this work we also make available a searchable database containing all of our results and the code used to find the completions. We emphasise that our methods extend beyond the study of neutrino-mass models, and may be useful for generating completions of high-dimensional operators in other effective field theories. Example code: ref. [37].


2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Miguel Escudero ◽  
Jacobo Lopez-Pavon ◽  
Nuria Rius ◽  
Stefan Sandner

Abstract At present, cosmological observations set the most stringent bound on the neutrino mass scale. Within the standard cosmological model (ΛCDM), the Planck collaboration reports ∑mv< 0.12 eV at 95 % CL. This bound, taken at face value, excludes many neutrino mass models. However, unstable neutrinos, with lifetimes shorter than the age of the universe τν ≲ tU, represent a particle physics avenue to relax this constraint. Motivated by this fact, we present a taxonomy of neutrino decay modes, categorizing them in terms of particle content and final decay products. Taking into account the relevant phenomenological bounds, our analysis shows that 2-body decaying neutrinos into BSM particles are a promising option to relax cosmological neutrino mass bounds. We then build a simple extension of the type I seesaw scenario by adding one sterile state ν4 and a Goldstone boson ϕ, in which νi→ ν4ϕ decays can loosen the neutrino mass bounds up to ∑mv ∼ 1 eV, without spoiling the light neutrino mass generation mechanism. Remarkably, this is possible for a large range of the right-handed neutrino masses, from the electroweak up to the GUT scale. We successfully implement this idea in the context of minimal neutrino mass models based on a U(1)μ−τ flavor symmetry, which are otherwise in tension with the current bound on ∑mv.


2020 ◽  
Vol 101 (9) ◽  
Author(s):  
Carolina Arbeláez ◽  
Giovanna Cottin ◽  
Juan Carlos Helo ◽  
Martin Hirsch

Universe ◽  
2020 ◽  
Vol 6 (11) ◽  
pp. 196
Author(s):  
Vitaly Beylin ◽  
Maxim Khlopov ◽  
Vladimir Kuksa ◽  
Nikolay Volchanskiy

The history of dark universe physics can be traced from processes in the very early universe to the modern dominance of dark matter and energy. Here, we review the possible nontrivial role of strong interactions in cosmological effects of new physics. In the case of ordinary QCD interaction, the existence of new stable colored particles such as new stable quarks leads to new exotic forms of matter, some of which can be candidates for dark matter. New QCD-like strong interactions lead to new stable composite candidates bound by QCD-like confinement. We put special emphasis on the effects of interaction between new stable hadrons and ordinary matter, formation of anomalous forms of cosmic rays and exotic forms of matter, like stable fractionally charged particles. The possible correlation of these effects with high energy neutrino and cosmic ray signatures opens the way to study new physics of strong interactions by its indirect multi-messenger astrophysical probes.


2014 ◽  
Vol 29 (10) ◽  
pp. 1450064 ◽  
Author(s):  
Sandy S. C. Law ◽  
Kristian L. McDonald

The complexity of radiative neutrino-mass models can be judged by: (i) whether they require the imposition of ad hoc symmetries, (ii) the number of new multiplets they introduce and (iii) the number of arbitrary parameters that appear. Considering models that do not employ new symmetries, the simplest models have two new multiplets and a minimal number of new parameters. With this in mind, we search for the simplest models of radiative neutrino mass. We are led to two models, containing a real scalar triplet and a charged scalar doublet (respectively), in addition to the charged singlet scalar considered by Zee [h+~(1, 1, 2)]. These models are essentially simplified versions of the Zee model and appear to be the simplest models of radiative neutrino mass. However, despite successfully generating nonzero masses, present-day data is sufficient to rule these simple models out. The Zee and Zee–Babu models therefore remain as the simplest viable models. Moving beyond the minimal cases, we find a new model of two-loop masses that employs the charged doublet Φ~(1, 2, 3) and the doubly-charged scalar k++~(1, 1, 4). This is the sole remaining model that employs only three new noncolored multiplets.


2017 ◽  
Vol 32 (14) ◽  
pp. 1742001
Author(s):  
Raymond R. Volkas

Radiative neutrino mass models and the seesaw models are viewed from the unifying framework of standard model effective operators that explicitly violate lepton number by two units [Formula: see text]. After some comments on naturalness and leptogenesis in the minimal type 1 seesaw model, a full list of minimal renormalisable models that produce mass dimension-7, [Formula: see text] operators at low energies is presented. By way of example, phenomenological bounds from Run 1 LHC and lepton flavour violation data are then placed on one of these models. A possible connection between radiative neutrino mass models and the current flavour anomalies in [Formula: see text] and [Formula: see text] transitions is then described.


2015 ◽  
Vol 30 (12) ◽  
pp. 1530030 ◽  
Author(s):  
Raymond R. Volkas

In this talk (talk given at the International Conference on Massive Neutrinos, Singapore, 9-13 February 2015), I describe the general characteristics of radiative neutrino mass models that can be probed at the LHC. I then cover the specific constraints on a new, explicit model of this type.


2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Michael Gustafsson ◽  
José Miguel No ◽  
Maximiliano A. Rivera

Abstract We investigate neutrino mass generation scenarios where the lepton number breaking new physics does not interact with Standard Model (SM) quarks and couples only to the SM right-handed charged lepton chirality. The lowest-order lepton number violating effective operator which describes this framework is a unique dimension nine operator involving SM gauge fields, $$ {\mathcal{O}}_9 $$ O 9 . We find that there are two possible classes of new physics scenarios giving rise to this $$ {\mathcal{O}}_9 $$ O 9 operator. In these scenarios neutrino masses are induced radiatively via dark matter interactions, linking the dark matter to a natural explanation for the smallness of neutrino masses compared to the electroweak scale. We discuss the phenomenology and existing constraints in the different neutrino mass models within each class. In particular, we analyze the important interplay between neutrino mixing and neutrinoless double β-decay in order to predict characteristic signatures and disfavour certain scenarios.


2021 ◽  
Vol 81 (6) ◽  
Author(s):  
Miguel Escudero ◽  
Samuel J. Witte

AbstractThe majoron, a neutrinophilic pseudo-Goldstone boson conventionally arising in the context of neutrino mass models, can damp neutrino free-streaming and inject additional energy density into neutrinos prior to recombination. The combination of these effects for an eV-scale mass majoron has been shown to ameliorate the outstanding $$H_0$$ H 0 tension, however only if one introduces additional dark radiation at the level of $$\Delta N_{\mathrm{eff}} \sim 0.5$$ Δ N eff ∼ 0.5 . We show here that models of low-scale leptogenesis can naturally source this dark radiation by generating a primordial population of majorons from the decays of GeV-scale sterile neutrinos in the early Universe. Using a posterior predictive distribution conditioned on Planck2018+BAO data, we show that the value of $$H_0$$ H 0 observed by the SH$$_0$$ 0 ES collaboration is expected to occur at the level of $$\sim 10\%$$ ∼ 10 % in the primordial majoron cosmology (to be compared with $$\sim 0.1\%$$ ∼ 0.1 % in the case of $$\Lambda $$ Λ CDM). This insight provides an intriguing connection between the neutrino mass mechanism, the baryon asymmetry of the Universe, and the discrepant measurements of $$H_0$$ H 0 .


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