arXiv subjects

Levent Solmaz

Publications and source records attributed to Levent Solmaz.

13 recordsLinked to original sources

arXiv2021

Model Characterization and Dark Matter in the Secluded $U(1)^\prime$ Model

We consider a class of $U(1)^\prime$-extended MSSM in which the $U(1)^{\prime}$ symmetry is broken by vacuum expectation values (VEVs) of four MSSM singlet fields. While one MSSM singlet field interacts with the MSSM Higgs fields, three of them interact only with each other in forming a secluded sector. Assigning universal $U(1)^{\prime}$ charges for three families, the anomaly cancellation condition requires exotic fields which are assumed to be heavy and decoupled. We discuss a variety of $U(1)^{\prime}$ charge assignments and anomaly cancellation, $Z^{\prime}/Z$ hierarchy, neutralinos, charginos and the Higgs sector. We find that the typical spectra involve two CP-odd Higgs bosons lighter than about 200 GeV and 600 GeV respectively, which are mostly formed by the MSSM singlet fields. If the relic density of dark matter is saturated only by a neutralino, compatible solutions predict LSP neutralinos formed by the MSSM singlet fields in the mass scales below about 600 GeV, while it is possible to realize MSSM neutralino LSP above these mass scales. One can classify the implications in three scenarios. Scenario I involves NLSP charginos, while Scenario II involves charginos which do not participate coannihilation processes with the LSP neutralino. These two scenarios predict MSSM singlet LSP neutralinos, while Scenario I leads to larger scattering cross-sections of dark matter. Scenario III has the solutions in which the MSSM neutralinos are considerably involved in LSP decomposition which yields very large scattering cross-section excluded by the direct detection experiments.

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arXiv2021

Family Non-Universal U(1)$^\prime$ Model with Minimal Number of Exotics

We have studied phenomenological implications of several family non-universal U(1)$^\prime$ sub-models in the U(1)$^\prime$-extended Minimal Supersysmmetric Standard Model (UMSSM) possesing an extra down quark type exotic field. In doing this, we have started by enforcing anomaly cancellation criteria to generate a number of solutions in which the extra U(1)$^\prime$ charges of the particles are treated as free parameters. We have then imposed existing bounds coming from colliders and astrophysical observations on the assumed sub-models and observed that current limits dictate certain charge orientations, for instance, $Q_{H_u}\sim Q_{H_d}$ is preferred in general and the charge of the singlet $Q_S$ cannot be very small ($|Q_S|>$ 0.4) even if any of the charges is allowed to take any value within the $[-1, 1]$ range. We have finally studied the potential impact of such non-universal charges on $Z'$ mediated processes and made predictions for existing and future experiments. It has turned out that UMSSMs with or without the presence of light exotic quarks can yield distinguisable signatures if non-universal charges are realised in the leptonic sector of such models.

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arXiv2017

Charged Higgs in MSSM and Beyond

We conduct a numerical study over the constrained MSSM (CMSSM), Next-to-MSSM (NMSSM) and $U(1)$ extended MSSM (UMSSM) to probe the allowed mass ranges of the charged Higgs boson and its dominant decay patterns, which might come into prominence in near future collider experiments. {We present results obtained from a limited scan for CMSSM} as a basis and compare its predictions with the extended models. We observe within our data that a wide mass range is allowed as $0.5(1) \lesssim m_{H^{\pm}} \lesssim 17$ TeV in UMSSM (NMSSM). We find that the dominant decay channel is mostly $H^{\pm}\rightarrow tb$ such that ${\rm BR}(H^{\pm}\rightarrow tb) \sim 80\%$. While this mode remains dominant over the whole allowed parameter space of CMSSM, we realize some special domains in the NMSSM and UMSSM, in which ${\rm BR}(H^{\pm}\rightarrow tb) \lesssim 10\%$. In this context, the decay patterns of the charged Higgs can play a significant role to distinguish among the SUSY models. In addition to the $tb$ decay mode, we find that the narrow mass scale in CMSSM allows only the decay modes for the charged Higgs boson to $\tau\nu$ ($\sim 16\%$), and their supersymmetric partners $\tilde{\tau}\tilde{\nu}$ ($\sim 13\%$). On the other hand, it is possible to realize the mode in NMSSM and UMSSM in which the charged Higgs boson decays into a chargino and neutralino pair up to about $25\%$. {This decay mode requires non-universal boundary conditions within the MSSM framework to be available, since CMSSM yields ${\rm BR} (H^{\pm}\rightarrow \tilde{\chi}_{1}^{0}\tilde{\chi}_{1}^{\pm}) \lesssim 1\%$.} It can also be probed in near future collider experiments through the missing energy and CP-violation measurements...

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arXiv2017

Least Fine-Tuned U(1) Extended SSM

We consider the Higgs boson mass in a class of the UMSSM models in which the MSSM gauge group is extended by an additional U(1)' group. Implementing the universal boundary conditions at the GUT scale we target phenomenologically interesting regions of UMSSM where the necessary radiative contributions to the lightest CP-even Higgs boson mass are significantly small and LSP is always the lightest neutralino. We find that the smallest amount of radiative contributions is about 50 GeV in UMSSM, this result is much lower than that obtained in MSSM, which is around 90 GeV. Additionally, we examine the Higgs boson properties in these models to check if it can behave similar to the SM Higgs boson under the current experimental constraints. We find that enforcement of smaller radiative contribution mostly restricts the U(1)' breaking scale as v_S <~ 10 TeV. Besides, such low contributions demand h_S ~ 0.2 - 0.45. Because of the model dependency in realizing these radiative contributions theta_E_6 < 0 are more favored, if one seeks for the solutions consistent with the current dark matter constraints. As to the mass spectrum, we find that stop and stau can be degenerate with the LSP neutralino in the range from 300 GeV to 700 GeV; however, the dark matter constraints restrict this scale as m_stop, m_stau >~ 500$ GeV. Such degenerate solutions also predict stop-neutralino and stau-neutralino coannihilation channels, which are effective to reduce the relic abundance of neutralino down to the ranges consistent with the current dark matter observations. Finally, we discuss the effects of heavy M_Z' in the fine-tuning. Even though the radiative contributions are significantly low, the required fine-tuning can still be large. We comment about reinterpretation of the fine-tuning measure in the UMSSM framework, which can yield efficiently low results for the fine-tuning at the electroweak scale.

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arXiv2016

Quasi Yukawa Unification and Fine-Tuning in U(1) Extended SSM

We consider the low scale implications in the U(1)' extended MSSM (UMSSM). We restrict the parameter space such that the lightest supersymmetric particle (LSP) is always the lightest neutralino. In addition, we impose quasi Yukawa unification (QYU) at the grand unification scale (M_GUT). QYU strictly requires the ratios among the yukawa couplings as y_t/y_b ~ 1.2, y_tau/y_b ~ 1.4, and y_t/y_tau ~ 0.8. We find that the need of fine-tuning over the fundamental parameter space of QYU is in the acceptable range (Delta_EW <= 10^3), even if the universal boundary conditions are imposed at M_ GUT, in contrast to CMSSM and NUHM. UMSSM with the universal boundary conditions yields heavy stops (m_{stop} >~ 2.5 TeV), gluinos (m_gluino >~ 2 TeV), and squarks from the first two families (m_squarks >~ 4 TeV). Similarly the stau mass is bounded from below at about 1.5 TeV. Despite this heavy spectrum, we find Delta_EW >~ 300, which is much lower than that needed for the minimal supersymmetric models. In addition, UMSSM yield relatively small mu-term, and the LSP neutralio is mostly form by the Higgsinos of mass >~ 700 GeV. We obtain also bino-like dark matter (DM) of mass about 400 GeV. Wino is usually found to be heavier than Higgsinos and binos, but there is a small region where mu ~ M_1 ~ M_2 ~ 1 TeV. We also identify chargino-neutralino coannihilation channel and A-resonance solutions which reduce the relic abundance of LSP neutralino down to the ranges compatible with the current WMAP measurements.

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arXiv2015

Generalized Soft Breaking Leverage for the MSSM

In this work we study implications of additional non-holomorphic soft breaking terms (mu', A'_t, A'_b and A'_tau) on the MSSM phenomenology. By respecting the existing bounds on the mass measurements and restrictions coming from certain B-decays, we probe reactions of the MSSM to these additional soft breaking terms. We provide examples in which some slightly excluded solutions of the MSSM can be made to be consistent with the current experimental results. During this, even after applying additional fine-tuning constraints the non-holomorphic terms are allowed to be as large as hundreds of GeV. Such terms prove that they are capable of enriching the phenomenology and varying the mass spectra of the MSSM heavily, with a reasonable amount of fine-tuning. We observe that higgsinos, the lightest stop, the heavy Higgs boson states A, H, charged H, sbottom and stau exhibit the highest sensitivity to the new terms. We also show how the light stop can become nearly degenerate with top quark using these non-holomorphic terms.

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arXiv2013

Higgs Bosons in supersymmetric U(1)' models with CP Violation

We study the Higgs sector of the U(1)'-extended MSSM with CP violation. This is an extension of the MSSM Higgs sector by one singlet field, introduced to generate the μterm dynamically. We are particularly interested in non-standard decays of Higgs particles, especially of the lightest one, in the presence of CP violating phases for μ_{eff} and the soft parameters. We present analytical expressions for neutral and charged Higgs bosons masses at tree and one-loop levels, including contributions from top and bottom scalar quark sectors. We then study the production and decay channels of the neutral Higgs for a set of benchmark points consistent with low energy data and relic density constraints. Numerical simulations show that a Higgs boson lighter than 2m_W can decay in a quite distinctive manner, including invisible modes into two neutralinos (h->χ^0χ^0) up to 50% of the time, when kinematically allowed. The branching ratio into h->bb, the dominant decay in the SM, is reduced in some U(1)' models and enhanced in others, while the branching ratios for the decays h -> τ+ τ-, h -> WW^* and h -> Z Z^*-> 4l are always reduced with respect to their SM expectations. This possibility has important implications for testing the U(1)' model both at the LHC and later at the ILC.

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arXiv2010

Tevatron Higgs Mass Bounds: Projecting U(1)' Models to LHC Domain

We study Higgs boson masses in supersymmetric models with an extra U(1) symmetry to be called U(1)$^{\prime}$. Such extra gauge symmetries are urged by the $μ$ problem of the MSSM, and they also arise frequently in low-energy supersymmetric models stemming from GUTs and strings. We analyze mass of the lightest Higgs boson and various other particle masses and couplings by taking into account the LEP bounds as well as the recent bounds from Tevatron experiments. We find that the $μ$-problem motivated generic low-energy U(1)$^{\prime}$ model yields Higgs masses as large as $\sim 200\ {\rm GeV}$ and violate the Tevatron bounds for certain ranges of parameters. We analyze correlations among various model parameters, and determine excluded regions by both scanning the parameter space and by examining certain likely parameter values. We also make educated projections for LHC measurements in light of the Tevatron restrictions on the parameter space. We further analyze certain benchmark models stemming from E(6) breaking, and find that they elevate Higgs boson mass into Tevatron's forbidden band when U(1)$^{\prime}$ gauge coupling takes larger values than the one corresponding to one-step GUT breaking.

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arXiv2009

Neutral Higgs Sector of the MSSM with Explicit CP violation and Non-Holomorphic Soft Breaking

Using the effective potential method, we computed one-loop corrections to the mass matrix of neutral Higgs bosons of the Non-Holomorphic Supersymmetric Standard Model (NHSSM) with explicit CP violation, where the radiative corrections due to the quarks and squarks of the third generation were taken into account. We observed that the non-holomorphic trilinear couplings can compete with the holomorphic ones in CP violating issues for the mass and mixing of the neutral Higgs bosons.

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arXiv2008

Electric Dipole Moments in U(1)' Models

We study electric dipole moments (EDM) of electron and proton in E(6)--inspired supersymmetric models with an extra U(1) invariance. Compared to the Minimal Supersymmetric Standard Model (MSSM), in addition to offering a natural solution to the mu problem and predicting a larger mass for the lightest Higgs boson, these models are found to yield suppressed EDMs.

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arXiv2006

Particle Spectrum in the Minimal Supersymmetric Standard Model with non-universal Higgs masses

We present semi-analytical solutions of the supersymmetric non-universal masses models for low $\tanβ$ regime. In addition to this, scale and $\tanβ$ dependencies of the soft (mass)$^2$ terms are given in the form of numerical solutions. By using the constrained form of the semi-analtic results, particular attention is paid on the non-universality assumption of the Higgs mass values and their potential measurable effects on the mass spectra of the minimal supersymmetric standard model. It is observed that, certain measurables are almost insensitive to the initial mass choices of the Higgs fields, like the mass of the light $\mathcal{CP}$-even Higgs boson. On the other hand, large deviations exist on the mass of the remaining physical Higgs bosons signal that the allowed parameter space of the model can be probed successfully. For this aim, in addition to the other physical Higgs bosons, imprints originating from the heavier chargino ($\tilde χ^\pm_2$), heavy neutralinos ($\tilde χ^0_3$, $\tilde χ^0_4$) and the light scalar tau ($\tilde τ_1$) are necessary and found to be promising.

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arXiv2006

Effects of Supersymmetric Threshold Corrections on High-Scale Flavor Textures

Integration of superpartners out of the spectrum induces potentially large contributions to Yukawa couplings. These corrections, the supersymmetric threshold corrections, therefore influence the CKM matrix prediction in a non-trivial way. We study effects of threshold corrections on high-scale flavor structures specified at the gauge coupling unification scale in supersymmetry. In our analysis, we first consider high-scale Yukawa textures which qualify phenomenologically viable at tree level, and find that they get completely disqualified after incorporating the threshold corrections. Next, we consider Yukawa couplings, such as those with five texture zeroes, which are incapable of explaining flavor-changing proceses. Incorporation of threshold corrections, however, makes them phenomenologically viable textures. Therefore, supersymmetric threshold corrections are found to leave observable impact on Yukawa couplings of quarks, and any confrontation of high-scale textures with experiments at the weak scale must take into account such corrections.

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arXiv2005

LEP Indications for Two Light Higgs Bosons and U(1)' Model

Reanalyses of LEP data have shown preference to two light CP-even Higgs bosons. We discuss implications of such a Higgs boson spectrum for the minimal supersymmetric model extended by a Standard Model singlet chiral superfield and an additional Abelian gauge invariance (the U(1)' model). We, in particular, determine parameter regions that lead to two light CP-even Higgs bosons while satisfying existing bounds on the mass and mixings of the extra vector boson. In these parameter regions, the pseudoscalar Higgs is found to be nearly degenerate in mass with either the lightest or next-to-lightest Higgs boson. Certain parameters of the U(1)' model such as the effective mu parameter are found to be significantly bounded by the LEP two-light-Higgs signal.

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