1,720,989 research outputs found
Beta and neutrinoless double beta decays with KeV sterile fermions
No full textMotivated by the capability of the KATRIN experiment to explore the existence of KeV neutrinos in the [1 − 18.5] KeV mass range, we explore the viability of minimal extensions of the Standard Model involving sterile neutrinos (namely the 3 + N frameworks) and study their possible impact in both the beta energy spectrum and the neutrinoless double beta decay effective mass, for the two possible ordering cases for the light neutrino spectrum. We also explore how both observables can discriminate between motivated low-scale seesaw realizations involving KeV sterile neutrinos. Our study concerns the prospect of a Type-I seesaw with two right-handed neutrinos, and a combination of the inverse and the linear seesaws where the Standard Model is minimally extended by two quasi-degenerate sterile fermions. We also discuss the possibility of exploring the latter case searching for double-kinks in KATRIN
Indirect constraints on lepton-flavor-violating quarkonium decays
No full textWithin an effective-field-theory framework, we present a model-independent analysis of the potential of discovering new physics by searching for lepton flavor violation in heavy quarkonium decays and, more in general, we study the phenomenology of lepton-flavor-violating (LFV) 2 quark-2 lepton (2q2) operators with two charm or bottom fields. We compute the constraints from LFV muon and tau decays on the new-physics operators that can induce LFV processes involving cc¯ and bb¯ systems, thus providing a comprehensive list of indirect upper limits on processes such as J/ψ→′, (nS)→′, (nS)→′γ etc., which can be sought at BESIII, Belle II, and the proposed super tau-charm factory. We show that such indirect constraints are so stringent that they prevent the detection of quarkonium decays into eμ. In the case of decays of quarkonia into τ (e, μ), we find that an improvement by 2-3 orders of magnitude on the current sensitivities is in general required in order to discover or further constrain new physics. However, we show that cancellations among different contributions to the LFV tau decay rates are possible, such that ϒ(nS)→τ can saturate the present experimental bounds. We also find that, interestingly, searches for LFV Z decays, Z→τ, at future e+e- colliders are complementary probes of 2q2ℓ operators with third generation quarksX. M. acknowledges partial support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 860881-HIDDeN and from the Spanish Research Agency (Agencia Estatal de Investigación) through the Grant IFT Centro de Excelencia Severo Ochoa No. CEX2020-001007-S and Grant No. PID2019-108892RB-I00 funded by MCIN/AE
Lepton flavor violation from diphoton effective interactions
Get PDFWe consider charged lepton flavor violating transitions mediated by the diphoton effective interactions ℓiℓjγγ and explore which processes can probe them better. Our analysis includes single and double radiative decays, ℓi → ℓjγ(γ), as well as ℓi → ℓj conversions in nuclei for all possible flavor combinations, which we compute for the first time for ℓ → τ conversions in this framework. We find that currently the best limits are provided by the loop-induced ℓi → ℓjγ processes, while the best future sensitivities come from μ → e conversion in aluminum and from potential τ → ℓγγ searches at Belle II or at the Super Tau Charm Facility. We also motivate the search for μ → eγγ at the Mu3e experiment as a complementary probe of these operatorsCEX2020-001007-S, Horizon Europe Programme under the Marie Skłodowska-Curie Grant Agreement No. 101066105 PheNUmena
Flavor techniques for LFV processes: Higgs decays in a general seesaw model
Get PDFInternational audienceLepton flavor violating processes are optimal observables to test new physics, since they are forbidden in the Standard Model while they may be generated in new theories. The usual approach to these processes is to perform the computations in the physical basis; nevertheless this may lose track of the dependence on some of the fundamental parameters, in particular on those at the origin of the flavor violation. Consequently, in order to obtain analytical expressions directly in terms of these parameters, flavor techniques are often preferred. In this work, we focus on the mass insertion approximation technique, which works with the interaction states instead of the physical ones, and provides diagrammatic expansions of the observables. After reviewing the basics of this technique with two simple examples, we apply it to the lepton flavor violating Higgs decays in the framework of a general type-I seesaw model with an arbitrary number of right-handed neutrinos. We derive an effective vertex valid to compute these observables when the right-handed neutrino masses are above the electroweak scale and show that we recover previous results obtained for low scale seesaws. Finally, we apply current constraints on the model to conclude on maximum Higgs decay rates, which unfortunately are far from current experimental sensitivities
Inclusive Displaced Vertex Searches for Heavy Neutral Leptons at the LHC
No full textInternational audienceThe inclusion of heavy neutral leptons to the Standard Model particle content could provide solutions to many open questions in particle physics and cosmology. The modification of the charged and neutral currents from active-sterile mixing of neutral leptons can provide novel signatures in Standard Model processes. We revisit the displaced vertex signature that could occur in collisions at the LHC via the decay of heavy neutral leptons with masses of a few GeV emphasizing the implications of flavor, kinematics, inclusive production and number of these extra neutral fermions. We study in particular the implication on the parameter space sensitivity when all mixings to active flavors are taken into account. We also discuss alternative cases where the new particles are produced in a boosted regime
and decays with sterile fermions
No full textMotivated by the capability of the KATRIN experiment to explore the existence of KeV neutrinos in the [1-18.5] KeV mass range, we explore the viability of minimal extensions of the Standard Model involving sterile neutrinos (effectively accounted by the 3+1 framework) and study their possible impact in both the beta decay and the neutrinoless double-beta decay effective mass, for the two possible ordering of the light neutrino spectrum. We also explore how both observables can discriminate between motivated low-scale seesaw realizations involving KeV sterile neutrinos.Based on A. Abada, A. Hernandez-Cabezudo, X. Marcano, In preparatio
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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