SUSY Contributions Research Articles

Interplay between the muon g−2 anomaly and the PTA nHZ gravitational waves from domain walls in the next-to-minimal supersymmetric standard model

With some explicitly Z3 breaking terms in the NMSSM (next-to-minimal supersymmetric standard model) effective superpotential and scalar potential, domain walls (DWs) from spontaneously breaking of the discrete symmetry in approximate Z3-invariant NMSSM can collapse and lead to observable stochastic gravitational wave (GW) background signals. In the presence of a hidden sector, such terms may originate from the geometric superconformal breaking with holomorphic quadratic correction to frame function when the global scale-invariant superpotential is naturally embedded into the canonical superconformal supergravity models. The smallness of such mass parameters in the NMSSM may be traced back to the original superconformal invariance. Naive estimations indicate that a SUSY explanation to muon g−2 anomaly can have tension with the constraints on SUSY by pulsar timing arrays data, because large SUSY contributions to Δaμ in general needs relatively light superpartners while present Ωgw0 can set the lower bounds for msoft. We calculate numerically the signatures of GWs produced from the collapse of DWs and find that the observed nHZ stochastic GW background by NANOGrav, etc., can indeed be explained with proper tiny values of χm3/2∼10−14 eV for χS2 case (and χm3/2∼10−10 eV for χHuHd case), respectively. Besides, there are still some parameter points, whose GW spectra intersect with the NANOGrav signal region, that can explain the muon g−2 anomaly to 1σ range. Published by the American Physical Society 2024

Stability of electroweak vacuum and supersymmetric contribution to muon g − 2

We study the stability of the electroweak vacuum in the supersymmetric (SUSY) standard model (SM), paying particular attention to its relation to the SUSY contribution to the muon anomalous magnetic moment aμ. If the SUSY contribution to aμ is sizable, the electroweak vacuum may become unstable because of enhanced trilinear scalar interactions. With aμ being fixed, larger slepton masses require more enhanced trilinear couplings, which make the electroweak vacuum more unstable. Thus, assuming SUSY contribution to aμ being sizable, an upper bound on the slepton masses is obtained. We give a detailed prescription to perform a full one-loop calculation of the decay rate of the electroweak vacuum for the case that the SUSY contribution to aμ is enhanced. We also give an upper bound on the slepton masses as a function of the SUSY contribution to aμ.

Muon and electron (g-2) anomalies with non-holomorphic interactions in MSSM

The recent Fermilab muon g-2 result and the same for electron due to fine-structure constant measurement through {}^{133}textrm{Cs} matter-wave interferometry are probed in relation to MSSM with non-holomorphic (NH) trilinear soft SUSY breaking terms, referred to as NHSSM. Supersymmetric contributions to charged lepton (g-2)_l can be enhanced via the new trilinear terms involving a wrong Higgs coupling with left and right-handed scalars. Bino-slepton loop is used to enhance the SUSY contribution to g-2 where wino mass stays at 1.5 TeV and the left and right slepton mass parameters for the first two generations are considered to be the same. Unlike many MSSM-based analyses completed before, the model does not require a light electroweakino, or light sleptons, or unequal left and right slepton masses, or a very large higgsino mass parameter. In absence of popular UV complete models, we treat the NH terms at par with MSSM soft terms, in a model independent framework of Minimal Effective Supersymmetry. The first part of the analysis involves the study of (g-2)_mu constraint along with the limits from Higgs mass, B-physics, collider data, direct detection of dark matter (DM), while focusing on a higgsino DM which is underabundant in nature. We then impose the constraint from electron g-2 where a large Yukawa threshold correction (an outcome of NHSSM) and opposite signs of trilinear NH coefficients associated with mu and e fields are used to satisfy the dual limits of Delta {a_mu } and Delta {a_e} (where the latter comes with negative sign). Varying Yukawa threshold corrections further provide the necessary flavor-dependent enhancement of Delta {a_e}/m_e^2 compared to that of Delta {a_mu }/m_mu ^2. A larger Yukawa threshold correction through A^prime _e for y_e also takes away the direct proportionality of a_e with respect to tan beta . With a finite intercept, a_e becomes only an increasing function of tan beta . We identified the available parameter space in the two cases while also satisfying the ATLAS data from slepton pair production searches in the plane of slepton mass parameter and the mass of the lightest neutralino.

Upper bound on the smuon mass from vacuum stability in the light of muon g − 2 anomaly

We derive an upper bound on the smuon mass assuming that the muon g−2 anomaly is explained by the supersymmetric (SUSY) contribution. In the minimal SUSY standard model, the SUSY contribution to the muon g−2 is enhanced when the Higgsino mass parameter is large. Then, the smuon-smuon-Higgs trilinear coupling is enhanced, which may destabilize the electroweak vacuum. We calculate precisely the decay rate of the electroweak vacuum in such a case. We include one-loop effects which are crucial to determine the overall normalization of the decay rate. Requiring that the theoretical prediction of the muon anomalous magnetic moment is consistent with the observed value at the 1 and 2σ levels (equal to the central value of the observed value), we found that the lightest smuon mass should be smaller than 1.38 and 1.68TeV (1.20TeV) for tan⁡β=10 (with tan⁡β being the ratio of the vacuum expectation values of the two Higgs bosons), respectively, and the bound is insensitive to the value of tan⁡β.

Gravitino dark matter, nonthermal leptogenesis, and low reheating temperature in no-scale Higgs inflation

We revisit Higgs inflation in the framework of a minimal extension of the Standard Model gauge symmetry by a $U(1)_{B-L}$ factor. Various aspects are taken into account with particular focus on the role of the supersymmetry breaking (SUSY) scale and the cosmological constraints associated with the gravitino. The scalar potential of the model is considered in the context of no-scale supergravity consisting of the F-part constructed from the K\"ahler function, the D-terms and soft SUSY contributions. We investigate several limiting cases and by varying the SUSY scale from a few TeV up to intermediate energies, for a spectral index around $n_s\sim 0.9655$ and reheating temperature $T_r\le 10^{9}$ GeV we find that the value of the tensor-to-scalar ratio ranges from $r\approx 10^{-3}$ to $10^{-2}$. Furthermore, it is shown that for certain regions of the parameter space the gravitino can live sufficiently long and as such is a potential candidate for a dark matter component. In general, the inflationary scenario is naturally implemented and it is consistent with non-thermal leptogenesis whereas the dominant decay channel of the inflaton yields right-handed neutrinos. Other aspects of cosmology and particle physics phenomenology are briefly discussed. Finally, we investigate the case where the inflaton is initially relaxed in a false minimum and estimate its probability to decay to the true vacuum.

Is the magnitude of the Peccei\u2013Quinn scale set by the landscape?

The value of the Higgs boson mass plus the lack of signal at LHC13 has led to a naturalness crisis for supersymmetric models. In contrast, rather general considerations of the string theory landscape imply a mild statistical draw towards large soft SUSY breaking terms tempered by the requirement of proper electroweak symmetry breaking where SUSY contributions to the weak scale are not too far from m_{weak}sim 100 GeV. Such a picture leads to the prediction that m_hsimeq 125 GeV while most sparticles are beyond current LHC reach. Here we explore the possibility that the magnitude of the Peccei–Quinn (PQ) scale f_a is also set by string landscape considerations within the framework of a compelling SUSY axion model. First, we examine the case where the PQ symmetry arises as an accidental approximate global symmetry from a more fundamental gravity-safe mathbb {Z}_{24}^R symmetry and where the SUSY mu parameter arises from a Kim-Nilles operator. The pull towards large soft terms then also pulls the PQ scale as large as possible. Unless this is tempered by rather severe (unknown) cosmological or anthropic bounds on the density of dark matter, then we would expect a far greater abundance of dark matter than is observed. This conclusion cannot be negated by adopting a tiny axion misalignment angle theta _i because WIMPs are also overproduced at large f_a. Hence, we conclude that setting the PQ scale via anthropics is highly unlikely. Instead, requiring soft SUSY breaking terms of order the gravity-mediation scale m_{3/2}sim 10–100 TeV places the mixed axion–neutralino dark matter abundance into the intermediate scale sweet zone where f_asim 10^{11}–10^{12} GeV. We compare our analysis to the more general case of a generic SUSY DFSZ axion model with uniform selection on theta _i but leading to the measured dark matter abundance: this approach leads to a preference for f_asim 10^{12} GeV.

Explaining electron and muon g \u2212 2 anomaly in SUSY without lepton-flavor mixings

We propose a SUSY scenario to explain the current electron and muon g − 2 discrepancies without introducing lepton flavor mixings. Threshold corrections to the Yukawa couplings can enhance the electron g − 2 and flip the sign of the SUSY contributions. The mechanism predicts a flavor-dependent slepton mass spectrum. We show that it is compatible with the Higgs mediation scenario.

NMSSM from alternative deflection in generalized deflected anomaly mediated SUSY breaking

We propose a new approach to generate messenger–matter interactions in deflected anomaly mediated SUSY breaking mechanism from typical holomorphic messenger–matter mixing terms in the Kahler potential. This approach is a unique feature of AMSB and has no analog in GMSB-type scenarios. New coupling strengths from the scaling of the (already known) Yukawa couplings always appear in this approach. With messenger–matter interactions in deflected AMSB, we can generate a realistic soft SUSY breaking spectrum for next-to-minimal supersymmetric standard model (NMSSM). Successful electroweak symmetry breaking conditions, which is not easy to satisfy in NMSSM for ordinary AMSB-type scenario, can be satisfied in a large portion of parameter space in our scenarios. We study the relevant phenomenology for scenarios with (Bino-like) neutralino and axino LSP, respectively. In the case of axino LSP, the SUSY contributions to Delta a_mu can possibly account for the muon g-2 discrepancy. The corresponding gluino masses, which are found to below 2.2 TeV, could be tested soon at LHC.

Exploring non-holomorphic soft terms in the framework of gauge mediated supersymmetry breaking

It is known that in the absence of a gauge singlet field, a specific class of supersymmetry (SUSY) breaking non-holomorphic (NH) terms can be soft breaking in nature so that they may be considered along with the Minimal Supersymmetric Standard Model (MSSM) and beyond. There have been studies related to these terms in minimal supergravity based models. Consideration of an F-type SUSY breaking scenario in the hidden sector with two chiral superfields however showed Planck scale suppression of such terms. In an unbiased point of view for the sources of SUSY breaking, the NH terms in a phenomenological MSSM (pMSSM) type of analysis showed a possibility of a large SUSY contribution to muon g − 2, a reasonable amount of corrections to the Higgs boson mass and a drastic reduction of the electroweak fine-tuning for a higgsino dominated {tilde{chi}}_1^0 in some regions of parameter space. We first investigate here the effects of the NH terms in a low scale SUSY breaking scenario. In our analysis with minimal gauge mediated supersymmetry breaking (mGMSB) we probe how far the results can be compared with the previous pMSSM plus NH terms based study. We particularly analyze the Higgs, stop and the electroweakino sectors focusing on a higgsino dominated {tilde{chi}}_1^0 and {tilde{chi}}_1^{pm } , a feature typically different from what appears in mGMSB. The effect of a limited degree of RG evolutions and vanishing of the trilinear coupling terms at the messenger scale can be overcome by choosing a non-minimal GMSB scenario, such as one with a matter-messenger interaction.

Probing non-holomorphic MSSM via precision constraints, dark matter and LHC data

In this analysis we explore the phenomenological constraints of models with non-holomorphic soft SUSY breaking terms in a beyond the MSSM scenario having identical particle content. The model referred as NHSSM shows various promising features like the possibility of a strong reduction in electroweak fine-tuning even for a scenario of a heavy higgsino type of LSP, a fact that is unavailable in pMSSM models. The other important aspect is satisfying the muon $g-2$ data even for a small $\tan\beta$ via a small value of coupling $A_\mu'$ associated with the tri-linear non-holomorphic soft term. Thus, a large SUSY contribution to muon $g-2$ is possible even for a significantly large smuon mass $m_{\tilde {\mu_1}}$. The Higgs mass radiative corrections are contributed by both the holomorphic and non-holomorphic trilinear soft parameters $A_t$ and $A_t'$, thus diluting the requirement to have a larger $A_t$ to satisfy the Higgs mass data. The model also provides with valid parameter space satisfying the constraint of $B \rightarrow X_s +\gamma$ for large values of $\tan\beta$, a scenario unfavourable in pMSSM.

Flavour violating lepton decays in low-scale seesaws

We present the first complete calculation of flavour violating lepton decays taking into account all supersymmetric (SUSY) and non-SUSY contributions in the context of the supersymmetric inverse seesaw, a specific SUSY low-scale seesaw model. We consider radiative and 3-body lepton decays as well as neutrinoless μ−e conversion in muonic atoms and perform a full one-loop calculation in the mass basis. Taking CMSSM-like boundary conditions for the soft SUSY breaking parameters, we find that cancellations between different contributions are present in several regions, which might reduce the branching ratios by as much as one order of magnitude. This has important consequences when translating current measurements into constraints and estimating the reach of future experiments, and justifies the use of a full calculation. We also show that the ratio of different cross-sections can discriminate between dominant SUSY or non-SUSY contributions.

Enhancement of the lepton flavor violating Higgs boson decay rates from SUSY loops in the inverse seesaw model

In this article we study the full one-loop SUSY contributions to the lepton flavor violating Higgs decay $h \to \tau \bar \mu $, within the context of the supersymmetric inverse sesaw model. We assume that both the right-handed neutrino masses, $M_R$, and their supersymmetric partner masses, $m_{\tilde \nu_R}$, are not far from the interesting ${\cal O}({\rm TeV})$ energy scale, and we work with scenarios with large neutrino Yukawa couplings that transmit large lepton flavor violating effects. By exploring the behavior with the most relevant parameters, mainly $M_R$, $m_{\tilde \nu_R}$ and the trilinear sneutrino coupling $A_\nu$, we will look for regions of the parameter space where the enhancement of $\mathrm{BR}(h\rightarrow \tau \bar \mu)$ is large enough to reach values at the percent level, which could explain the excess recently reported by CMS and ATLAS at the CERN Large Hadron Collider.

Mass limit for light flavon with residual Z3 symmetry

We present a modified Altarelli and Feruglio $A_4$ model where an additional $A_4$ singlet-prime flavon is introduced. In this model, non-zero $\theta _{13}$ is given by this additional $A_4$ singlet-prime flavon which breaks tri-bimaximal mixing. In the framework of the supersymmetry with $U(1)_R$ symmetry, we obtain vacuum expectation values (VEVs) and VEV alignments of flavons through driving fields. It is considered that flavon induces distinctive flavor violating process if flavon mass is light. Assuming mass of SUSY particles are sufficiently heavy so that the SUSY contributions can be negligible, we discuss the flavor violating Yukawa interaction through flavon exchange in the charged lepton sector. According to the potential analysis, the VEV of flavon breaks $A_4$ down to $Z_3$ in the charged lepton sector and relation among flavon masses is determined. Thanks for the residual $Z_3$ symmetry, many lepton flavor violating decay modes are forbidden except for $\tau \rightarrow \mu \mu \bar{e}$ and $\tau \rightarrow e e \bar{\mu}$. A mass limit of the flavon from these three-body decay modes is $60$~GeV taking into account the current experimental lower bounds at the Belle experiment. In our model, we predict a ratio of the branching ratios $\tau \rightarrow \mu \mu \bar{e}$ and $\tau \rightarrow e e \bar{\mu}$ by using known charged lepton masses. We also find that the production cross section for the flavon can be $\mathcal{O}(1)$ fb. Thus the flavon would be found at the LHC run 2 by searching for 4-tau lepton signal.

CP-violating phenomenological MSSM

We investigate the sensitivity of the next generation of flavor-based low-energy experiments to probe the supersymmetric parameter space in the context of the phenomenological MSSM (pMSSM), and examine the complementarity with direct searches for Supersymmetry at the 13 TeV LHC in a quantitative manner. To this end, we enlarge the previously studied pMSSM parameter space to include all physical non-zero CP-violating phases, namely those associated with the gaugino mass parameters, Higgsino mass parameter, and the tri-linear couplings of the top quark, bottom quark and tau lepton. We find that future electric dipole moment and flavor measurements can have a strong impact on the viability of these models even if the sparticle spectrum is out of reach of the 13 TeV LHC. In particular, the lack of positive signals in future low-energy probes would exclude values of the phases between ${\cal O}(10^{-2})$ and ${\cal O}(10^{-1})$. We also find regions of parameter space where large phases remain allowed due to cancellations. Most interestingly, in some rare processes, such as BR($B_s \to \mu^+ \mu^-$ ), we find that contributions arising from CP-violating phases can bring the potentially large SUSY contributions into better agreement with experiment and Standard Model predictions.

Improved prediction for the mass of the W boson in the NMSSM

Electroweak precision observables, being highly sensitive to loop contributions of new physics, provide a powerful tool to test the theory and to discriminate between different models of the underlying physics. In that context, the $W$ boson mass, $M_W$, plays a crucial role. The accuracy of the $M_W$ measurement has been significantly improved over the last years, and further improvement of the experimental accuracy is expected from future LHC measurements. In order to fully exploit the precise experimental determination, an accurate theoretical prediction for $M_W$ in the Standard Model (SM) and extensions of it is of central importance. We present the currently most accurate prediction for the $W$ boson mass in the Next-to-Minimal Supersymmetric extension of the Standard Model (NMSSM), including the full one-loop result and all available higher-order corrections of SM and SUSY type. The evaluation of $M_W$ is performed in a flexible framework, which facilitates the extension to other models beyond the SM. We show numerical results for the $W$ boson mass in the NMSSM, focussing on phenomenologically interesting scenarios, in which the Higgs signal can be interpreted as the lightest or second lightest CP-even Higgs boson of the NMSSM. We find that, for both Higgs signal interpretations, the NMSSM $M_W$ prediction is well compatible with the measurement. We study the SUSY contributions to $M_W$ in detail and investigate in particular the genuine NMSSM effects from the Higgs and neutralino sectors.

KL -> 0 Formula decay correlating with K in high-scale SUSY

We have studied the contribution of high-scale SUSY to the |$K_L \to \pi ^0 \nu {\bar {\nu }}$| and |$K^+ \to \pi ^+ \nu {\bar {\nu }}$| processes by correlating with the CP-violating parameter |$\epsilon _K$|⁠. Taking account of the recent LHC results for Higgs discovery and SUSY searches, we consider high-scale SUSY at the |$10$|–|$50$|TeV scale in the framework of non-minimal squark (slepton) flavor mixing. The Z penguin mediated chargino dominates the SUSY contribution for these decays. At the |$10$|TeV SUSY scale, the chargino contribution can enhance the branching ratio of |$K_L \to \pi ^0 \nu {\bar {\nu }}$| by eight times compared with SM predictions, whereas the predicted branching ratio |${\textit {BR}}(K^+ \to \pi ^+ \nu {\bar {\nu }})$| increases by up to three times that of the SM. The gluino box diagram dominates the SUSY contribution of |$\epsilon _K$| up to |$30{\%}$|⁠. If down-squark mixing is neglected compared with up-squark mixing, the Z penguin mediated chargino dominates both SUSY contributions of |${\textit {BR}}(K_L \to \pi ^0 \nu {\bar {\nu }})$| and |$\epsilon _K$|⁠. Then, a correlation between them is found, but the chargino contribution to |$\epsilon _K$| is at most |$3{\%}$|⁠. Even if the SUSY scale is |$50$|TeV, the chargino process still enhances the branching ratio of |$K_L \to \pi ^0 \nu {\bar {\nu }}$| from the SM prediction by a factor of two, and |$\epsilon _K$| is deviated from the SM prediction by |$\mathcal {O}(10{\%})$|⁠. We also discuss the chargino contribution to the |$K_L \to \pi ^0 e^+e^-$| process.

Sensitivity of High-Scale SUSY in Low Energy Hadronic FCNC

We discuss the sensitivity of the high-scale supersymmetry (SUSY) at \(10\)–\(1000\) TeV in \(B^0\), \(B_s\), \(K^0\) and \(D\) meson systems together with the neutron electric dipole moment (EDM) and the mercury EDM. In order to estimate the contribution of the squark flavor mixing to these flavor changing neutral currents (FCNCs), we calculate the squark mass spectrum, which is consistent with the recent Higgs discovery. The SUSY contribution in \(\epsilon_K\) could be large, around \(40\%\) in the region of the SUSY scale \(10\)–\(100\) TeV. The neutron EDM and the mercury EDM are also sensitive to the SUSY contribution induced by the gluino-squark interaction. The predicted EDMs are roughly proportional to \(|\epsilon_K^{\rm SUSY}|\). If the SUSY contribution is the level of \({\cal O}(10\%)\) for \(\epsilon_K\), the neutron EDM is expected to be discovered in the region of \(10^{-28}\)–\(10^{-26}\) ecm. The mercury EDM also gives a strong constraint for the gluino-squark interaction. The SUSY contribution of \(\Delta M_D\) is also discussed.

Lepton flavor violation in low-scale seesaw models: SUSY and non-SUSY contributions

Taking the supersymmetric inverse seesaw mechanism as the explanation for neutrino oscillation data, we investigate charged lepton flavor violation in radiative and 3-body lepton decays as well as in neutrinoless $\mu-e$ conversion in muonic atoms. In contrast to former studies, we take into account all possible contributions: supersymmetric as well as non-supersymmetric. We take CMSSM-like boundary conditions for the soft supersymmetry breaking parameters. We find several regions where cancellations between various contributions exist, reducing the lepton flavor violating rates by an order of magnitude compared to the case where only the dominant contribution is taken into account. This is in particular important for the correct interpretation of existing data as well as for estimating the reach of near future experiments where the sensitivity will be improved by one to two orders of magnitude. Moreover, we demonstrate that ratios like BR($\tau\to 3 \mu$)/BR($\tau\to \mu e^+ e^-$) can be used to determine whether the supersymmetric contributions dominate over the $W^\pm$ and $H^\pm$ contributions or vice versa.

Electron electric dipole moment as a sensitive probe of PeV scale physics

We give a quantitative analysis of the electric dipole moments as a probe of high scale physics. We focus on the electric dipole moment of the electron since the limit on it is the most stringent. Further, theoretical computations of it are free of QCD uncertainties. The analysis presented here first explores the probe of high scales via electron EDM within MSSM where the contributions to the electric dipole moment (EDM) arise from the chargino and the neutralino exchanges in loops. Here it is shown that the electron EDM can probe mass scales from tens of TeV into the PeV range.The analysis is then extended to include a vectorlike generation which can mix with the three ordinary generations. Here new CP phases arise and it is shown that the electron EDM now has not only a supersymmetric contribution from the exchange of charginos and neutralinos but also a non-supersymmetric contribution from the exchange of W and Z bosons. It is further shown that the interference of the supersymmetric and the non-supersymmetric contribution leads to the remarkable phenomenon where the electron EDM as a function of the slepton mass first falls and become vanishingly small and then rises again as the slepton mass increases This phenomenon arises as a consequence of cancellation between the SUSY and the non-SUSY contribution at low scales while at high scales the SUSY contribution dies out and the EDM is controlled by the non-SUSY contribution alone. The high mass scales that can be probed by the EDM are far in excess of what accelerators will be able to probe. The sensitivity of the EDM to CP phases both in the SUSY and the non-SUSY sectors are also discussed.

Probing the high scale SUSY in CP violations of K, [formula omitted] and [formula omitted] mesons

We probe the high scale SUSY at 10–50 TeV in the CP violations of K, B0 and Bs mesons. In order to estimate the contribution of the squark flavor mixing to these CP violations, we discuss the squark mass spectrum, which is consistent with the recent Higgs discovery. Taking the universal soft parameters at the SUSY breaking scale, we obtain the squark mass spectrum at 10 TeV and 50 TeV, where the SM emerges. Then, the 6×6 mixing matrix between down-squarks and down-quarks is discussed by input of the experimental data of K, B0 and Bs mesons. It is found that ϵK is most sensitive to the high scale SUSY. The SUSY contributions for the time-dependent CP asymmetries SJ/ψKS and SJ/ψϕ are 6–8% at the SUSY scale of 10 TeV. We also discuss the SUSY contribution to the chromo-EDM of the strange quark.