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Constraining sleptons at the LHC in a supersymmetric low-scale seesaw scenario
Get PDFThe discovery of the Higgs boson in the 8 TeV run of the LHC [1, 2] marks one of the
most important milestones in particle physics. Its mass is already known rather precisely:
mh = 125.09 ± 0.21 (stat.) ±0.11 (syst.) GeV [3], and the signal strength of various LHC
searches has been found consistent with the SM predictions. While this completes the
Standard Model (SM) particle-wise, several questions still remain open, for example: (i) Is
it possible to include the SM in a grand unified theory where all gauge forces unify? (ii) Is
there a particle physics explanation of the observed dark matter relic density? (iii) What
causes the hierarchy in the fermion mass spectrum and why are neutrinos so much lighter
than the other fermions? What causes the observed mixing patterns in the fermion sector?
(iv) What stabilizes the Higgs mass at the electroweak scale?
Supersymmetric model address several of these questions and consequently the search for
supersymmetry (SUSY) is among the main priorities of the LHC collaborations. Up to now
no significant sign for physics beyond SM has been found. The combination of the Higgs
discovery with the (yet) unsuccessful searches has led to the introduction of a model class
called ‘natural SUSY’ [4–15]. Here, the basic idea is to give electroweak-scale masses only
to those SUSY particles giving a sizeable contribution to the mass of the Higgs boson, such
that a too large tuning of parameters is avoided. All other particle masses are taken at the
multi-TeV scale. In particular, masses of the order of a few hundred GeV up to about one
TeV are assigned to the higgsinos (the partners of the Higgs bosons), the lightest stop (the
partner of the top-quark) and, if the latter is mainly a left-stop, also to the light sbottom In
addition the gluino and the heavier stop masses should also be close to at most a few TeV.
Neutrino oscillation experiments confirm that at least two neutrinos have a non-zero mass.
The exact mass generation mechanism for these particles is unknown, and both the SM and
the MSSM remain agnostic on this topic. Although many ways to generate neutrino mass
exist, perhaps the most popular one is the seesaw mechanism [16–21]. The main problem
with the usual seesaw mechanisms lies on the difficulty in testing its validity. In general, if
Yukawa couplings are sizeable, the seesaw relations require Majorana neutrino masses to be
very large, such that the new heavy states cannot be produced at colliders. In contrast, if
one requires the masses to be light, then the Yukawas need to be small, making production
cross-sections and decay rates to vanish. A possible way out of this dilemma lies on what
3
is called the inverse seesaw [22], which is based on having specific structures on the mass
matrix (generally motivated by symmetry arguments) to generate small neutrino masses.
This, at the same time, allows Yukawa couplings to be large, and sterile masses to be light.
We consider here a supersymmetric model where neutrino data are explained via a minimal
inverse seesaw scenario where the gauge-singlet neutrinos have masses in the range
O(keV) to O(100 GeV). We explore this with a parametrization built for the standard seesaw,
and go to the limit where the inverse seesaw emerges, such that Yukawas and mixings
become sizeable. Although non-SUSY versions of this scenario can solve the dark matter
and matter-antimatter asymmetry problems [23–25], we shall make no claim on these issues
in our model.
In view of the naturalness arguments, we further assume that the higgsinos have masses of
O(100 GeV), whereas the gaugino masses lie at the multi-TeV scale (see [26] for an example
of such a scenario). In addition, we assume all squarks are heavy enough such that LHC
bounds are avoided, and play no role in the phenomenology within this work1. In contrast
we allow for fairly light sleptons and investigate the extent to which current LHC data can
constrain such scenarios.
This paper is organized as follows: in the next section we present the model. Section
III summarizes the numerical tools used and gives an overview of the LHC analysis used
for these investigations. In Section IV we present our findings for the two generic scenarios
which differ in the nature of the lighest supersymmetric particle (LSP): a Higgsino LSP
and a sneutrino LSP. In Section V we draw our conclusions. Appendices A and B give the
complete formulae for the neutrino and sneutrino masses
Constraining sleptons at the LHC in a supersymmetric low-scale seesaw scenario
No full textThe discovery of the Higgs boson in the 8 TeV run of the LHC [1, 2] marks one of the
most important milestones in particle physics. Its mass is already known rather precisely:
mh = 125.09 ± 0.21 (stat.) ±0.11 (syst.) GeV [3], and the signal strength of various LHC
searches has been found consistent with the SM predictions. While this completes the
Standard Model (SM) particle-wise, several questions still remain open, for example: (i) Is
it possible to include the SM in a grand unified theory where all gauge forces unify? (ii) Is
there a particle physics explanation of the observed dark matter relic density? (iii) What
causes the hierarchy in the fermion mass spectrum and why are neutrinos so much lighter
than the other fermions? What causes the observed mixing patterns in the fermion sector?
(iv) What stabilizes the Higgs mass at the electroweak scale?
Supersymmetric model address several of these questions and consequently the search for
supersymmetry (SUSY) is among the main priorities of the LHC collaborations. Up to now
no significant sign for physics beyond SM has been found. The combination of the Higgs
discovery with the (yet) unsuccessful searches has led to the introduction of a model class
called ‘natural SUSY’ [4–15]. Here, the basic idea is to give electroweak-scale masses only
to those SUSY particles giving a sizeable contribution to the mass of the Higgs boson, such
that a too large tuning of parameters is avoided. All other particle masses are taken at the
multi-TeV scale. In particular, masses of the order of a few hundred GeV up to about one
TeV are assigned to the higgsinos (the partners of the Higgs bosons), the lightest stop (the
partner of the top-quark) and, if the latter is mainly a left-stop, also to the light sbottom In
addition the gluino and the heavier stop masses should also be close to at most a few TeV.
Neutrino oscillation experiments confirm that at least two neutrinos have a non-zero mass.
The exact mass generation mechanism for these particles is unknown, and both the SM and
the MSSM remain agnostic on this topic. Although many ways to generate neutrino mass
exist, perhaps the most popular one is the seesaw mechanism [16–21]. The main problem
with the usual seesaw mechanisms lies on the difficulty in testing its validity. In general, if
Yukawa couplings are sizeable, the seesaw relations require Majorana neutrino masses to be
very large, such that the new heavy states cannot be produced at colliders. In contrast, if
one requires the masses to be light, then the Yukawas need to be small, making production
cross-sections and decay rates to vanish. A possible way out of this dilemma lies on what
3
is called the inverse seesaw [22], which is based on having specific structures on the mass
matrix (generally motivated by symmetry arguments) to generate small neutrino masses.
This, at the same time, allows Yukawa couplings to be large, and sterile masses to be light.
We consider here a supersymmetric model where neutrino data are explained via a minimal
inverse seesaw scenario where the gauge-singlet neutrinos have masses in the range
O(keV) to O(100 GeV). We explore this with a parametrization built for the standard seesaw,
and go to the limit where the inverse seesaw emerges, such that Yukawas and mixings
become sizeable. Although non-SUSY versions of this scenario can solve the dark matter
and matter-antimatter asymmetry problems [23–25], we shall make no claim on these issues
in our model.
In view of the naturalness arguments, we further assume that the higgsinos have masses of
O(100 GeV), whereas the gaugino masses lie at the multi-TeV scale (see [26] for an example
of such a scenario). In addition, we assume all squarks are heavy enough such that LHC
bounds are avoided, and play no role in the phenomenology within this work1. In contrast
we allow for fairly light sleptons and investigate the extent to which current LHC data can
constrain such scenarios.
This paper is organized as follows: in the next section we present the model. Section
III summarizes the numerical tools used and gives an overview of the LHC analysis used
for these investigations. In Section IV we present our findings for the two generic scenarios
which differ in the nature of the lighest supersymmetric particle (LSP): a Higgsino LSP
and a sneutrino LSP. In Section V we draw our conclusions. Appendices A and B give the
complete formulae for the neutrino and sneutrino masses
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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