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Emine Yildirim

Publications and source records attributed to Emine Yildirim.

11 recordsLinked to original sources
arXiv2026

Double SM-like Higgs production at future $ e^+ e^- $ colliders in the 3-Higgs Doublet Model under the $ S_{3} $ symmetry

In this paper, we present the production of double Standard Model (SM)-like Higgs $ (h) $ at the future electron positron colliders within the framework of the $ S_{3} $ model with three Higgs doublets (S3-3H) and no CP violation to describe beyond the SM Higgs Physics. We focus first on the numerically allowed parameter space of the model, taking into account theoretical bounds from perturbative unitarity and vacuum stability, as well as by data at the Large Hadron Collider (LHC) and the Tevatron. Double Higgs production in the S3-3H model can deviate from the SM predictions up to a few orders of magnitude in both the $ e^+e^- \rightarrow hhZ $ and the $ e^+ e^- \rightarrow h hν_{e} \barν_{e}$ channels. Thus, our findings indicate that the S3-3H model can lead to sizable deviations from the SM predictions of Higgs production at future $ e^+ e^- $ colliders. These results highlight the importance of studies at such colliders for searching for physics beyond the SM.

hep-ph↗
arXiv2024

Polytopal realizations of non-crystallographic associahedra

We use the folding technique to show that generalized associahedra for non-simply-laced root systems (including non-crystallographic ones) can be obtained as sections of simply-laced generalized associahedra constructed by Bazier-Matte, Chapelier-Laget, Douville, Mousavand, Thomas and Yildirim.

math.CO↗
arXiv2022

Loop induced $h \rightarrow γγ, Zγ, gg $ decays in 3-Higgs doublet models

In this paper, we analyze the loop induced decays of neutral Higgs boson $ h $ into pairs of photons, gluons, and Z$ γ$ in 3-Higgs Doublet Models (3HDMs), where all the doublets have non-zero vacuum expectation values. In the 3HDM, there are contributions to these decays from loops of charged scalars $ H^{\pm}_{1,2} $ that are not present in the Standard Model. We find an enhancement in the channel $ h\rightarrow Zγ$ with respect to the Standard Model prediction in some parameter region while respecting constraints from the measurements of $ h\rightarrow γγ$ at the LHC. The charged Higgs bosons $ H^{\pm}_{1,2} $ lead to the enhancement of $ Zγ$ decay mode in some part of the parameter space of the 3HDM. Then, we discuss the correlations between the decay modes $ h\rightarrow Zγ$ and $ h\rightarrow γγ$. Moreover, we study Type-I and Type-Z of 3HDMs and find that these types of 3HDMs can be distinguished via only the gluonic decays, since the contributions of the $ H^{\pm}_{1,2} $ loops are dominant to those of fermion loops. We also investigate the effects of the model parameters on these loop induced decays. As an interesting phenomenological consequence, the 3HDM is dominantly governed by the parameters: two ratios of vacuum expectation values (VEVs); $ \tanγ,~\tanβ$ and the mixing angles of the CP-even Higgs bosons, $ α_{1,2}~ \text{and}~θ$.

hep-ph↗
arXiv2021

Completions of discrete cluster categories of type $\mathbb{A}$

We complete the discrete cluster categories of type $\mathbb{A}$ as defined by Igusa and Todorov, by embedding such a discrete cluster category inside a larger one, and then taking a certain Verdier quotient. The resulting category is a Hom-finite Krull-Schmidt triangulated category containing the discrete cluster category as a full subcategory. The objects and Hom-spaces in this new category can be described geometrically, even though the category is not $2$-Calabi-Yau and Ext-spaces are not always symmetric. We describe all cluster-tilting subcategories. Given such a subcategory, we define a cluster character that takes values in a ring with infinitely many indeterminates. Our cluster character is new in that it takes into account infinite dimensional sub-representations of infinite dimensional ones. We show that it satisfies the multiplication formula and also the exchange formula, provided that the objects being exchanged satisfy some local Calabi-Yau conditions.

math.RT↗
arXiv2018

The Coxeter transformation on Cominuscule Posets

Let $\mathsf{J(C)}$ be the poset of order ideals of a cominuscule poset $\mathsf{C}$ where $\mathsf{C}$ comes from two of the three infinite families of cominuscule posets or the exceptional cases. We show that the Auslander-Reiten translation $τ$ on the Grothendieck group of the bounded derived category for the incidence algebra of the poset $\mathsf{J(C)}$, which is called the \emph{Coxeter transformation} in this context, has finite order. Specifically, we show that $τ^{h+1}=\pm id$ where $h$ is the Coxeter number for the relevant root system.

math.RT↗
arXiv2017

LHC Phenomenology of Composite 2-Higgs Doublet Models

We investigate the phenomenology of Composite 2-Higgs Doublet Models (C2HDMs) of various Yukawa types based on the global symmetry breaking $SO(6)\to SO(4)\times SO(2)$. The kinetic term and the Yukawa Lagrangian are constructed in terms of the pseudo Nambu-Goldstone Boson (pNGB) matrix and a 6-plet of fermions under $SO(6)$. The scalar potential is assumed to be the same as that of the Elementary 2-Higgs Doublet Model (E2HDM) with a softly-broken discrete $Z_2$ symmetry. We then discuss the phenomenological differences between the E2HDM and C2HDM by focusing on the deviations from Standard Model (SM) couplings of the discovered Higgs state ($h$) as well as on the production cross sections and Branching Ratios (BRs) at the Large Hadron Collider (LHC) of extra Higgs bosons. We find that, even if the same deviation in the $hVV$ ($V=W,Z$) coupling is assumed in both scenarios, there appear significant differences between E2HDM and C2HDM from the structure of the Yukawa couplings, so that production and decay features of extra Higgs bosons can be used to distinguish between the two scenarios.

hep-ph↗
arXiv2017

Single and Double SM-like Higgs Boson Production at Future Electron-Positron Colliders in C2HDMs

We investigate single- and double-$h$, the discovered Standard Model (SM)-like Higgs boson, production at future $e^+e^-$ colliders in Composite 2-Higgs Doublet Models (C2HDMs) and Elementary 2-Higgs Doublet Models (E2HDMs) with a softly-broken $Z_2$ symmetry. We first survey their parameter spaces allowed by theoretical bounds from perturbative unitarity and vacuum stability as well as by future data at the Large Hadron Collider (LHC) with an integrated luminosity up to 3000 fb$^{-1}$ under the assumption that no new Higgs boson is detected. We then discuss how different the cross sections can be between the two scenarios when $κ_V^{}$, the $hVV$ ($V=W^\pm,Z$) coupling normalised to the SM value, is taken to be the same value in the both scenario We find that if $κ_V^2$ is found to be, e.g., $0.98$, then the cross sections in C2HDMs with $f$ (the compositeness scale) in the TeV region can be maximally changed to be about $-15\%$, $-18\%$, $-50\%$ and $-35\%$ for the $e^+e^-\to t \bar t h$, $e^+e^-\to Zhh$, $e^+e^-\to e^+e^-hh$ and $e^+e^-\to t\bar{t}hh$ processes, respectively, with respect to those in E2HDMs. Thus, a future electron-positron collider has the potential to discriminate between E2HDMs and C2HDMs, even when only $h$ event rates are measured.

hep-ph↗
arXiv2017

Light charged Higgs boson scenario in 3-Higgs doublet models

The constraints from the measurements of the $B\to X_sγ$ decay rate on the parameter space of 3-Higgs Doublet Models (3HDMs), where all the doublets have non-zero vacuum expectation values, are studied at the next-to-leading order in QCD. In order to naturally avoid the presence of flavour changing neutral currents at the tree level, we impose two softly-broken discrete $Z_2$ symmetries. This gives rise to five independent types of 3HDMs that differ in their Yukawa couplings. We show that in all these 3HDMs (including the case of type-II-like Yukawa interactions) both masses of the two charged Higgs bosons $m_{H_1^\pm}$ and $m_{H_2^\pm}$ can be smaller than the top mass $m_t$ while complying with the constraints from $B\to X_sγ$. As an interesting phenomenological consequence, the branching ratios of the charged Higgs bosons decay into the $cb$ final states can be as large as $80\%$ when their masses are taken to be below $m_t$ in two of the five 3HDMs (named as Type-Y and Type-Z). This light charged Higgs boson scenario provides a hallmark 3HDM signature that cannot be realised in $Z_2$ symmetric 2-Higgs doublet models. We find that in the Type-Y and Type-Z 3HDMs the scenario with $90\,{\rm GeV}< m_{H^\pm_1}^{}\,, m_{H^\pm_2}^{}<m_t$ is ruled out by the direct searches at the LHC, but in the Type-Y 3HDM $80~\text{GeV}<m_{H_1^\pm}^{}<90~\text{GeV}$ and $90~\text{GeV}<m_{H_2^\pm}^{}<m_t$ is allowed by $B\to X_sγ$ and direct searches at LEP2, Tevatron and LHC due to the reduced sensitivity of these searches to the degenerate case $m_{H_1^\pm}\approx m_{W^\pm}$. The cases where only one or both charged Higgs bosons are above the top quark mass are also naturally allowed in the both Type-Y and Type-Z 3HDMs.

hep-ph↗
arXiv2016

Light charged Higgs boson scenario in 3HDMs

The measurement of the $B\to X_sγ$ process gives important constraints on physics related to charged Higgs bosons ($H^\pm$). In 2-Higgs Doublet Models (2HDMs) with a softly-broken $Z_2$ symmetry, a light $H^\pm$ scenario, in which $H^\pm$ can be produced via the top decay, is possible in two of four types of Yukawa interactions (the so-called Type-I and Type-X). In these types of 2HDMs, the $H^\pm \to τ^\pm ν$ decay mode is dominant in wide regions of the parameter space. In this report, we discuss the other possibility of a light charged Higgs boson scenario in 3-Higgs-Doublet Models (3HDMs) based on the results obtained in Ref. [1]. We show that charged Higgs bosons can mainly decay into $cb$ without contradiction with the $B\to X_sγ$ data and the direct searches for charged Higgs bosons at the LHC, and this scenario cannot be realized in the 2HDMs.

hep-ph↗
arXiv2016

Perturbative Unitarity Bounds in Composite 2-Higgs Doublet Models

We study bounds from perturbative unitarity in a Composite 2-Higgs Doublet Model (C2HDM) based on the spontaneous breakdown of a global symmetry $SO(6)\to SO(4)\times SO(2)$ at the compositeness scale $f$. The eight pseudo Nambu-Goldstone Bosons (pNGBs) emerging from such a dynamics are identified as two isospin doublet Higgs fields. We calculate the $S$-wave amplitude for all possible 2-to-2-body elastic (pseudo)scalar boson scatterings at energy scales $\sqrt{s}$ reachable at the Large Hadron Collider (LHC) and beyond it, including the longitudinal components of weak gauge boson states as the corresponding pNGB states. In our calculation, the Higgs potential is assumed to have the same form as that in the Elementary 2-Higgs Doublet Model (E2HDM) with a discrete $Z_2$ symmetry, which is expected to be generated at the one-loop level via the Coleman-Weinberg (CW) mechanism. We find that the $S$-wave amplitude matrix can be block-diagonalized with maximally $2\times 2$ submatrices in a way similar to the E2HDM case as long as we only keep the contributions from ${\cal O }(ξs)$ and ${\cal O }(ξ^0 s^0)$ in the amplitudes, where $ξ=v_{\text{SM}}^2/f^2$ and $v_{\text{SM}}^{}\simeq 246$ GeV, which is an appropriate approximation for our analysis. By requiring the C2HDM to satisfy perturbative unitarity at energies reachable by the LHC, we derive bounds on its parameters such as $ξ$ and the masses of extra Higgs bosons present in the scenario alongside the Standard Model (SM)-like Higgs state discovered in 2012.

hep-ph↗