arXiv subjects

Cem Salih Un

Publications and source records attributed to Cem Salih Un.

At least 19 recordsLinked to original sources

arXiv2026

Compressed Stop-Neutralino Spectra from Yukawa Unified Non-Holomorphic Pati-Salam Model: Prospects for the FCC

We explore the weak-scale phenomenology of SUSY models with the $SU(4)_{C}\times SU(2)_{L}\times SU(2)_{R}$ gauge symmetry. We include non-holomorphic soft supersymmetry breaking terms arising from perturbations on D-branes. These terms significantly alter the implications of Yukawa unification, as they directly interfere in the threshold corrections to the Yukawa couplings. With these corrections, Yukawa unification can be compatible with low fine-tuning alongside a heavy Higgsino-like lightest supersymmetric particle; however, these solutions are strongly constrained by dark matter observations. Furthermore, in contrast to previous studies, the non-holomorphic contributions accommodate heavy gluino masses in this class of models from approximately 2.2 to 10 TeV while preserving Yukawa unification. These gluinos can be probed up to about 2.5 TeV in high-luminosity collider searches, and up to about 6 TeV at future 100 TeV center-of-mass energy colliders. With the non-holomorphic threshold corrections to Yukawa couplings, Yukawa unification can be accommodated with relatively light third-generation squarks. We find that the supersymmetric spectra can accommodate sbottom masses around 1.5 TeV, making them highly accessible to upcoming experimental searches. The stop can also be as light as about 1.5~TeV, resulting in a compressed stop-neutralino spectrum. Although these solutions lie beyond the sensitivity of current collider searches, they can be potentially probed at future facilities, such as the proposed Future Circular Collider. Our results do not include systematic uncertainties, which can heavily impact the experimental analysis. In this context, our findings serve to highlight potential directions and prospects for new physics searches at future collider experiments. Our results assume that overall systematic uncertainties in background modeling do not exceed $0.1\%$.

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arXiv2026

Mono-Z' Signatures in the B-L Supersymmetric Standard Model at the LHC

The B-L Supersymmetric Standard Model with Inverse Seesaw (BLSSM-IS) extends the Minimal Supersymmetric Standard Model (MSSM) by incorporating a gauged B-L symmetry, right-handed neutrinos and an additional neutral gauge boson Z'. Searches at the Large Hadron Collider (LHC) constrain the mass of this gauge boson to be as low as only ~ 2.2 TeV in the BLSSM-IS, owing to interference effects with the SM. In this framework, mono-Z' events can arise from the associated production of a Z' boson and a singlet Higgs boson h', where h' subsequently decays into missing energy carried by a pair of the Lightest Supersymmetric Particle (LSP) - either a neutralino or a right-handed sneutrino - which serves as a Dark Matter (DM) candidate. Focusing on leptonic decays of the Z' (electrons and muons), we analyse the kinematic distributions of the final-state leptons and the missing transverse energy in order to extract a signal for this process which is independent of the nature of the BLSSM-IS DM.

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arXiv2026

LHC and dark matter implications of t-b-τ Yukawa unification in split SUSY GUTs

We investigate a grand unification (GUT) inspired version of the minimal supersymmetric standard model (MSSM) based on a left-right symmetric $4$-$2$-$2$ gauge group, incorporating Yukawa coupling unification and current phenomenological constraints. Utilizing a split soft supersymmetry-breaking (SSB) parameter space motivated by flavor symmetries, we analyze the implications of recent results from ATLAS, CMS, LHCb, and dark matter direct detection experiments. Our numerical scans, conducted with SARAH and SPheno, identify viable low-energy regions consistent with third-generation Yukawa unification, the observed Higgs boson mass, dark matter relic density, and flavor observables such as $B \to X_s γ$, $B_s \to μ^+ μ^-$ and $B_u \to τν_τ$ . Our findings suggest that while current bounds severely constrain much of the MSSM-like parameter space, substantial regions remain experimentally viable and testable in the ongoing LHC run and next-generation dark matter experiments.

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arXiv2025

Non-holomorphic Contributions in GMSB with Adjoint Messengers

We consider models of gauge mediated supersymmetry breaking, in which the breaking is transmitted to the visible sector by the messenger fields from the adjoint representation of MSSM's gauge group. We include the non-holomorphic terms induced by the supersymmetry breaking and involve them in the renormalization group evolution. The main impact from the non-holomorphic terms arises in the right-handed stau mass, which requires large hypercharge interactions with the messengers to accommodate non-tachyonic staus. With the non-holomorphic terms, the stau mass-square can remain positive in the renormalization group evolution, even if the hypercharge interactions are small. Although the radiative non-holomorphic contributions enhance the mass spectrum, their effects in the sparticle mixing rather reduce their overall contributions such that we realize about 25 GeV difference in the right-handed stau mass, while the difference is lowered by about 5 TeV in the lightest mass-eigenstate of staus. We realize 6-7 TeV difference in the sbottom mass, and about 15 TeV in the stop mass. These contributions in the sparticle masses also affect the SM-like Higgs boson mass, and we find that the SM-like Higgs boson can be enhanced as much as about 80 GeV. In a small region of the parameter space we also observe negative non-holomorphic contributions which do not exceed about 1 TeV for the sparticles, and 20 GeV for the SM-like Higgs boson. An interesting impact from the non-holomorphic terms happens in the muon g-2 results. We find that the non-holomorphic contributions can provide a significant decreasing in supersymmetric contributions to muon g-2. We realize that the muon g-2 results can be decreased as much as about -50 x 10^-10 by the non-holomorphic contributions, and consequently one can still accommodate light sleptons and gauginos in the spectrum.

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arXiv2024

Muon g-2 and lepton flavor violation in supersymmetric GUTs

We present a class of supersymmetric (SUSY) GUT models that can explain the apparent discrepancy between the SM predictions and experimental values of muon g-2 while providing testable signals for lepton flavor violation in charged lepton decays. Moreover, these models predict LSP neutralino abundance that is compatible with the Planck dark matter bounds. We find that scenarios in the framework of $SU(4)_c\times SU(2)_L\times SU(2)_R$ unification, with additional symmetries to explain fermion masses and neutrino oscillations, provide interesting benchmarks for the search of SUSY by correlating a possible manifestation of it in dark matter, rare lepton decays and LHC signals.

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arXiv2024

Low Fine-Tuning with Heavy Higgsinos in Yukawa Unified SUSY GUTs

The work presented considers a class of minimally constructed Yukawa unified SUSY GUTs - NUHM2 - and explore their implications when their soft supersymmetry breaking Lagrangian is generalized by the non-holomorphic terms which provide extra contributions to the Higgsino mass and couple the supersymmetric scalar fields to the wrong Higgs doublets. With such a simple extension, it can be found several regions with interesting implications which cannot be realized in the usual restricted models. It is observed that the Yukawa unification solutions can be compatible with relatively light mass spectrum and acceptable low fine-tuning measurements. In the restricted models such effects can directly be addressed to the non-holomorphic terms. They can provide a slight improvement in the SM-like Higgs boson mass without altering the mass spectrum too much, and they can accommodate relatively lighter sbottom and stau masses, while they do not change the stop sector much. The dark matter can be Higgsino-like or Bino-like, but the experimental relic density measurements favor the Higgsino-like dark matter, while the Bino-like dark matter is predicted with a quite large relic density. Also several coannihilation scenarios are identified in the Higgsino-like dark matter regions, while the Bino-like dark matter do not allow any of such coannihilation processes. The presence of the non-holomorphic terms can weaken the impact from the phenomenological or indirect constraints such as low fine-tuning, Yukawa unification and rare decays of $B-$meson, the direct and model independent constraints still yield a strong strike on the solutions. Such constraints are discussed in regard of the current collider analyses on $ττ$ events and direct detection of dark matter experiments.

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arXiv2023

Muon $g-2$ and dark matter in Supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R$

The latest FermiLab muon $g-2$ result shows a $5σ$ discrepancy with a ``widely advertised" Standard Model prediction. We consider a supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R$ model in which this discrepancy is resolved by including contributions to muon $g-2$ from a relatively light SUSY sector. A variety of realistic coannihilation scenarios can reproduce the observed dark matter relic abundance. With a significantly reduced discrepancy, of order $1 σ$ or less, the Higgsino-like dark matter solutions are also viable. We provide benchmark points for these solutions that will be probed in the direct detection dark matter experiments and collider searches.

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arXiv2023

Third family quasi-Yukawa unification: Higgsino dark matter, NLSP gluino and all that

We explore the implications of third family ($t-b-τ$) quasi-Yukawa unification (QYU) for collider and dark matter (DM) searches within the framework of a supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R$ model. The deviation from exact Yukawa unification is quantified through the relation $y_t : y_b : y_τ= |1+C|:|1-C|:|1+3C|$, with $C$ being a real parameter ($|C| \leq 0.2$). We allow for the breaking of left-right symmetry both by the soft scalar and gaugino mass parameters and obtain a variety of viable solutions that predict the sparticle mass spectrum including LSP DM (whose stability is guaranteed by a $Z_2$ gauge symmetry). We highlight solutions that include an NLSP gluino with mass $\sim$ 1.3-2.5 TeV, which should be accessible at LHC Run 3. There also exist NSLP stop solutions with masses heavier than about 1.8 TeV, which are consistent with the LSP neutralino dark matter relic density through stop-neutralino coannihilation. We identify A-resonance solutions with DM mass $\sim$ 0.8 - 2 TeV, as well as bino-chargino, bino-slepton and bino-stau co-annihilation scenarios. Finally, we also identify Wino-like ($\sim99\%$) and Higgsino-like ($\sim99\%$) solutions whose masses are heavier than about 1.5 TeV and 1 TeV, respectively. These solutions are compatible with the desired dark matter relic density and testable in ongoing and future direct detection experiments.

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arXiv2022

Explaining the ${\mathcal{R}}(D)$ and ${\mathcal{R}}(D^{\ast})$ Anomalies in the $B-L$ Supersymmetric Standard Model with Inverse Seesaw

We investigate the ${\mathcal{R}}(D)$ and ${\mathcal{R}}(D^{\ast})$ anomalies in the context of the $B-L$ extension of the Minimal Supersymmetric Standard Model with Inverse Seesaw. We demonstrate that the lepton penguin $W^{\pm}l \barν_l $ ($l=e,μ,τ$) mediated by CP-even/odd right-handed sneutrinos, charginos and neutralinos can account for these anomalies simultaneously.

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arXiv2022

The 28 GeV Dimuon Excess in Lepton Specific 2HDM

We explore the Higgs mass spectrum in a class of Two Higgs Doublet Models (THDMs) in which a scalar SU(2)_L doublet interacts only with quarks, while the second one interacts only with leptons. The spectrum includes two CP-even Higgs bosons, either of which can account for the SM-like Higgs boson, and the spectra involving light Higgs bosons receive strong impacts from the LEP results and the current collider analyses. We find that a consistent spectrum can involve a CP-odd Higgs boson as light as about 10 GeV, while the lightest CP-even Higgs boson cannot be lighter than about 55 GeV when m_A ~ 28 GeV. These analyses can rather bound the low tan beta region which can also accommodate an observed excess in dimuon events at m_mumu ~ 28 GeV. A lepton-specific class of THDMs (LS-THDM) can predict such an excess through A -> mu mu decays, while the solutions can be constrained by the A -> tau tau mode. After constraining the solutions with the consistent ranges of sigma(pp -> bbA -> bb tau tau), a largest excess at about 1.5 sigma at 8 TeV center of mass (COM) energy and 2 sigma at 13 TeV COM is observed for tan beta ~ 12 and m_A ~ 28 GeV in the sigma(pp -> bbA -> bb mu mu) events.

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arXiv2022

Proton Lifetime in Minimal SUSY SU(5) in Light of LHC Results

We examine proton decay mediated by color-triplet Higgsinos in minimal supersymmetric $SU(5)$ grand unified theory in light of the discovery of the Higgs boson and the absence of SUSY signals at the LHC. We pay special attention to various threshold effects arising from Planck-suppressed operators that affect the color-triplet Higgsino mass and also correct the wrong mass relations for the light fermions. Our analysis allows for a non-universal SUSY spectrum with the third family scalars having a separate mass compared to the first two families. We identify the allowed parameter space of the model and show that the SUSY scalar masses are constrained by current limits from proton lifetime to be above 5 TeV, while the glunio, Wino and the Higgsinos may be within reach of the LHC. When the SUSY scalar masses are required to be $\leq 20$ TeV, so that they are within reach of next generation collider experiments, we find that proton lifetime for the decay $p \rightarrow \overlineν K^+$ is bounded by $τ(p \rightarrow \overlineν K^+) \leq 1.1 \times 10^{35}$ yrs.

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arXiv2022

Muon g-2, Neutralino Dark Matter and Stau NLSP

We explore the implications of resolving the muon g-2 anomaly in a SU(4)_c x SU(2)_L x SU(2)_R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 sigma resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass <~ 400 GeV, and the sleptons from the first two families can be as heavy as about 800 GeV. The chargino is also required to be lighter than about 600 GeV to accommodate the muon g-2 solutions consistent with the dark matter relic density constraint. The dominant right-handed nature of the light slepton states suppress the sensitivity of possible signals which can be probed in Run3 experiments at the LHC. We also discuss the impact of accomodating the Higgs boson mass and the vacuum stability of the scalar potential for these solutions. The Higgsinos are heavier than about 4 TeV, and the LSP neutralino has the correct relic density if it is Bino-like. We identify stau-neutralino coannihilation as the dominant mechanism for realizing the desired dark matter relic density, with sneutrino-neutralino coannihiliation playing a minor role. These bino-like dark matter solutions can yield a spin-independent scattering cross-section on the order of 10^{-3} pb which hopefully, can be expected to be tested in the near future.

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arXiv2021

Sparticle Spectroscopy at LHC-Run3 and LSP Dark Matter in light of Muon g-2

Inspired by the latest measurement of muon g-2 by the Fermilab Experiment, we revisit a class of supersymmetric models in which non-universality at M_GUT allows us to realize relatively light sleptons in the few hundred GeV range. These sleptons provide additional contributions to muon g-2 that can be arranged to reconcile theory and experiment. The solutions compatible with the muon g-2 resolution typically predict light sleptons, charginos and neutralinos. We show how these solutions can be probed during LHC-Run3. A direct impact on the chargino mass is observed such that the chargino can be probed up to about 800 GeV during the Run3 experiments. Despite such a direct impact, it is still possible to realize lighter chargino masses which can escape detection due to the chirality mixture of the lighter slepton states. The colored squarks as well as the gluino turn out to be heavier than about 3-4 TeV if the LSP neutralino satisfies the Planck bound on the dark matter relic abundance. We highlight a variety of benchmark points and, in particular, coannihilation scenarios with dark matter candidates that will be tested in the ongoing and planned direct and indirect detection experiments. By relaxing the requirement that the LSP neutralino saturates the relic dark matter abundance, we are able to find solutions with gluino and squark masses in a range that may be accessible at LHC-Run3.

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arXiv2020

Sparticle Spectroscopy and Dark Matter in a $U(1)_{B-L}$ extension of MSSM

We consider a class of SUSY models in which the MSSM gauge group is supplemented with a gauged $U(1)_{B-L}$ symmetry and a global $U(1)_{R}$ symmetry. This extension introduces only electrically neutral states, and the new SUSY partners effectively double the number of states in the neutralino sector that now includes a blino (from $B-L$) and singlino from a gauge singlet superfield. If the DM density is saturated by a LSP neutralino, the model yields quite a rich phenomenology depending on the DM composition. The LSP relic density constraint provides a lower bound on the stop and gluino masses of about 3 TeV and 4 TeV respectively, which is testable in the near future collider experiments such as HL-LHC. The chargino mass lies between 0.24 TeV and about 2.0 TeV, which can be tested based on the allowed decay channels. We also find $m_{\tildeτ_{1}}\gtrsim 500$ GeV, and $m_{\tilde{e}},m_{\tildeμ},m_{\tildeν^{S,P}} \gtrsim 1$ TeV. We identify chargino-neutralino coannihilation processes in the mass region $0.24 \,{\rm TeV} \lesssim m_{\tildeχ_{1}^{0}}\approx m_{\tildeχ_{1}^{\pm}}\lesssim 1.5$ TeV, and also coannihilation processes involving stau, selectron, smuon and sneutrinos for masses around 1 TeV. In addition, $A_{2}$ resonance solutions are found around 1 TeV, and $H_{2}$ and $H_{3}$ resonance solutions are also shown around 0.5 TeV and 1 TeV . Some of the $A_{2}$ resonance solutions with $\tanβ\gtrsim 20$ may be tested by the $A/H\rightarrow τ^{+}τ^{-}$ LHC searches. While the relic density constraint excludes the bino-like DM, it is still possible to realize higgsino, singlino and blino-like DM for various mass scales. We show that all these solutions will be tested in future direct detection experiments such as LUX-Zeplin and Xenon-nT.

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arXiv2020

Scalar Dark Matter and Electroweak Stability

The standard model of elementary particles (SM), despite experimental completion at the LHC, needs to be extended for various physical reasons, including the cold dark matter (DM). Each extension comes with its scale and mechanism, and typically lifts, at the loop level, the electroweak scale towards its high scale. The problem is to keep the electroweak scale stable while providing a room for the aforementioned heavy extensions. To this end, it turns out that the SM Higgs sector remains stable in the presence of a heavy scalar if their quartic couplings unify at a certain scale when their masses are degenerate. Under this mass-degeneracy-driven unification (MDDU), the scalar under concern is found to qualify as a viable DM candidate and to leave the electroweak scale stable. Our detailed simulation studies explicitly show that the MDDU parameter space agrees with current collider and astrophysical bounds. Our work can be extended to other relevant scalars (like flavons, inflaton and others) as a mechanism by which the electroweak scale is held stable.

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arXiv2020

Testing Yukawa Unification at LHC Run-3 and HL-LHC

We explore $t-b-τ$ Yukawa unification (YU) in a supersymmetric $SU(4)_c \times SU(2)_L \times SU(2)_R $ model without imposing a discrete left-right (L-R) symmetry. A number of interesting solutions that are compatible with $t-b-τ$ YU, LSP neutralino dark matter (DM), and LHC and other experimental constraints are identified. In particular, they include gluino-neutralino and stau-neutralino co-annihilation scenarios, where the NLSP gluino mass can range from 1-3 TeV. Higgsino-like dark matter solutions are also identified for which gluino masses can approach 5 TeV or so. This scenario will be tested at LHC Run-3 and its future upgrades.

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arXiv2019

Stop Search in SUSY SO(10) GUTs with Nonuniversal Gaugino Masses

We have discussed the stop mass and possible signal processes within a class of SUSY GUTs with non-universal gaugino masses. This class of models predicts the stop mass in a wide range from about 400 GeV to 8 TeV, and the DM constraints bound it as $m_{\tilde{t}_{1}}\gtrsim 500$ GeV. Being the lightest supersymmetric particle the neutralino always takes part in possible signal processes, and its mass is realized as heavy as about 2.3 TeV in the fundamental parameter space. Similarly, the lightest chargino mass can be realized beyond 3 TeV, while the DM constraints bound its mass at about 2.7 TeV from above. We find that the stop mass below about 1.2 TeV is excluded by the analyses over the $\tilde{t}_{1}\rightarrow t\tildeχ_{1}^{0}$ decay mode performed under the current experimental setups. This mode can help probe the stop mass up to about 6 TeV in future collider experiments. Similar analyses yield that the stop mass will be able to be probed to about 4.8 TeV and 5 TeV, if the $\tilde{t}_{1}\rightarrow b W^{\pm}\tildeχ_{1}^{0}$ or $\tilde{t}_{1}\rightarrow b q\bar{q}^{\prime}\tildeχ_{1}^{0}$ decay modes are allowed. We show that the former decay mode is not available for this class of SUSY GUTs in the current experiments, while it will be able to be tested in future.

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arXiv2019

Gluino Search with Stop and Top in Nonuniversal Gaugino Mass Models at LHC and Future Colliders

We discuss the gluino mass in the CMSSM and Nonuniversal Gaugino Mass Models (NUGM) frameworks in light of the results from the current LHC and Dark Matter experiments. We probe the gluino mass scales by considering its decay modes into stop and top quarks, $\tilde{g}\rightarrow \tilde{t}_{1}t$ and $\tilde{g}\rightarrow \bar{t}t\tildeχ_{1}^{0}$, where $\tilde{t}_{1}t$ represents both $\tilde{t}_{1}\bar{t}$ and $\tilde{t}_{1}^{*}t$. The region with $m_{\tilde{g}} \lesssim 2$ TeV is excluded up to $68\%$ CL in the CMSSM if the gluino decays into a stop and top quark, while the $95\%$ CL exclusion requires $m_{\tilde{g}}\gtrsim 1.9$ TeV. Such exclusion bounds on the gluino mass more or less overlap with the current LHC results. The decay mode $\tilde{g}\rightarrow \bar{t}t\tildeχ_{1}^{0}$ may take over if $\tilde{g}\rightarrow \tilde{t}_{1}t$ is not allowed. One can probe the gluino mass in this case up to about 1.5 TeV with $68\%$ CL in the CMSSM, and about 1.4 TeV with $95\%$ CL. A similar analyses in the NUGM framework yield exclusion curves for the gluino mass $m_{\tilde{g}}\gtrsim 2.1$ TeV at 14 TeV for both decay modes of the gluino under consideration. We also show that increasing the center of mass energy to 27 TeV can probe the gluino mass up to about 3 TeV through its decay mode into stop and top quark. The Dark Matter constraints are not very severe in the framework of NUGM, and they allow solutions with $m_{\tilde{g}},m_{\tilde{t}} \gtrsim 1$ TeV. In addition, with NUGM the LSP neutralino can coannihilate with gluino and/or stop for $m_{\tilde{g}},m_{\tilde{t}}\approx m_{\tildeχ_{1}^{0}} \in [0.9-1.5]$ TeV. The 100 TeV FCC collider can probe the gluino masses up to about 6 TeV with $36.1~fb^{-1}$ integrated luminosity. We also find that the decay $\tilde{g}\rightarrow \tilde{t}t$ can indirectly probe the stop mass up to about 4 TeV.

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