The LHC discovered the Standard Model (SM) like Higgs boson with mass around 125 GeV. However, there exist hints of deviations from Higgs decays. Including the Tevatron data, the deviations can be explained by the extremely mixed stop sector in the sense of best global fit (BGF). We analyze the relations among the competing reduced coupling hGG, Higgs boson mass,and LHC stop mass m_{\wt t_1} lower bound at the tree- and one-loop level. In particular, we point out that we use the light stop running mass in the Higgs boson mass calculation while the light stop pole mass in the Higgs decays. So the gluino radiative correction on the light stop mass plays the crucial role. Its large negative correction saves the GBF in the Minimal Supersymmetric SM (MSSM) and the next to the MSSM (NMSSM) constrained by the perturbativity. Moreover, a light stop is predicted: in the MSSM if we set the gluino mass M_3\lesssim4 TeV, we have m_{\wt t_1}<m_t; while in the NMSSM, imposing the least tuning condition we get m_{\wt t_1}\simeq130 GeV for M_3\simeq1.5 TeV.
We investigate the implications of the Higgs rate measurements from Run 1 of the LHC for the mass of the light scalar top partner (stop) in the Minimal Supersymmetric Standard Model (MSSM). We focus on light stop masses, and we decouple the second, heavy stop and the gluino to the multi-TeV range in order to obtain a Higgs mass of around 125 GeV. We derive lower mass limits for the light stop within various scenarios, taking into account the effects of a possibly light scalar tau partner (stau) or chargino on the Higgs rates, of additional Higgs decays to undetectable new physics, as well as o…
Searching for top squark (stop) is a crucial task of the LHC. When the flavor conserving two body decays of the stop are kinematically forbidden, the stops produced near the threshold will live long enough to form bound states which subsequently decay through annihilation into the Standard Model (SM) final states. In the region of stop mixing angle $θ_{\tilde{t}} \to 0$ or $π/2$, we note that the LHC-13 TeV diphoton resonance data can give a strong bound on the spin-$0$ stoponium ($η_{\tilde{t}}$) and exclude the constituent stop mass $m_{\tilde{t}}$ up to about 290 GeV. While in the large sto…
Pair production of Higgs bosons at hadron colliders is an enticing channel to search for new physics. New colored particles that couple strongly to the Higgs, such as those most often called upon to address the hierarchy problem, provide well motivated examples in which large enhancements of the di-Higgs rate are possible, at least in principle. However, in such scenarios the di-Higgs production rate is tightly correlated with the single Higgs production rate and, since the latter is observed to be SM-like, one generally expects that only modest enhancements in di-Higgs production are allowed …
We utilize the recent LHC-13 TeV data to study the lower mass bound on top-squark (stop) in natural supersymmetry. We recast the LHC sparticle inclusive search of $(\ge 1){\rm jets} + E^{miss}_T$ with $α_T$ variable, the direct stop pair search (1-lepton channel and all-hadronic channel) and the monojet analyses. We find that these searches are complementary depending on stop and higgsino masses: for a heavy stop the all-hadronic stop pair search provides the strongest bound, for an intermediate stop the inclusive SUSY analysis with $α_T$ variable is most efficient, while for a compressed stop…
Supersymmetric extensions of the standard model contain additional heavy neutral Higgs bosons that are coupled to heavy scalar top quarks (stops). This system exhibits interesting field theoretic phenomena when the Higgs mass is close to the stop-antistop production threshold. Existing work in the literature has examined the digluon-to-diphoton cross section near threshold and has focused on enhancements in the cross section that might arise either from the perturbative contributions to the Higgs-to-digluon and Higgs-to-diphoton form factors or from mixing of the Higgs boson with stoponium sta…
We compute the full next-to-leading order supersymmetric (SUSY) electroweak (EW) and SUSY-QCD corrections to the decays of CP-odd NMSSM Higgs bosons into stop pairs. In our numerical analysis we also present the decay of the heavier stop into the lighter stop and an NMSSM CP-odd Higgs boson. Both the EW and the SUSY-QCD corrections are found to be significant and have to be taken into account for a proper prediction of the decay widths.
We study the detectability of the stoponium in the di-Higgs decay mode at the photon-photon collider option of the International $e^+e^-$ Linear Collider (ILC), whose center-of-mass energy is planned to reach $\sim 1$ TeV. We find that $5σ$ detection of the di-Higgs decay mode is possible with the integrated electron-beam luminosity of $1 {\rm ab}^{-1}$ if the signal cross section, $σ(γγ\rightarrow σ_{\tilde{t}_1} \rightarrow hh)$, of ${\cal O}(0.1)$ fb is realized for the stoponium mass smaller than $\sim$ 800 GeV at 1 TeV ILC. Such a value of the cross section can be realized in the minimal …
In order to accommodate the observed Higgs boson mass in the CMSSM, the stops must either be very heavy or the mixing in the stop sector must be very large. Lower stop masses, possibly more accessible at the LHC, still give the correct Higgs mass only if the trilinear stop mixing parameter $|A_t|$ is in the multi-TeV range. Recently it has been shown that such large stop mixing leads to an unstable electroweak vacuum which spontaneously breaks charge or colour. In this work we therefore go beyond the CMSSM and investigate the effects of including baryon number violating operators $λ'' \bar{\bf…
Recently ATLAS reported a $3.3σ$ excess in the stop search with $\ell+jets+E_T^{miss}$ channel. We try to interpret the signal by a light stop pair production in the MSSM. We find: (1) simple models where stop decays into a higgsino or a bino are not favored. (2) an extension of them can explain the data at $2σ$ level without conflicting with the other search channels. A surviving possibility includes a light stop and a light higgsino, which is expected in a natural SUSY scenario.
We study a model where quintessence potential $e^{-ξϕ}$ coupled to Higgs potential. We calculate the evolution of the quintessence, and track the running of the effective Higgs self-coupling. We find it slightly larger than that of the standard model in the past. Requiring the electroweak vacuum to be absolutely stable in inflationary era, we find a lower bound $ξ> 0.35\pm 0.05$, where the uncertainty is mainly from the measurement of the top quark mass. This lower bound, together with the upper bound from the observation for dark energy $ξ\lesssim0.6$, narrows down the parameter space and mak…
We have explored the possibilities of scenarios with heavy gluinos and light stops in supersymmetric (SUSY) standard models with extra vector-like multiplets. If we assume the hierarchical structure for soft masses of the minimal supersymmetric standard model (MSSM) scalar fields and extra scalars, the light stop and the observed Higgs boson can be realized. While the stau is the lightest SUSY particle (LSP) in broad parameter space, we have found that the neutralino LSP is realized in the case that the non-zero soft parameters for the MSSM Higgs doublets or the non-universal gaugino masses ar…
Top squark (stop) plays a key role in the radiative stability of the Higgs boson mass in supersymmetry (SUSY). The LHC searches for stop have made a great progress and tightly constrained the stop mass during Run-1. In this work, we use the LHC Run-1 data to determine the lower mass limit of the right-handed stop in a natural SUSY scenario, where the higgsinos $\tildeχ^0_{1,2}$ and $\tildeχ^\pm_{1}$ are light and nearly degenerate. We find that the stop mass has been excluded up to 430 GeV for $m_{\tildeχ^0_1} \lesssim 250$ GeV and to 540 GeV for $m_{\tildeχ^0_1} \simeq 100$ GeV by the Run-1 S…
Higgs signatures from the cascade decays of light stops are an interesting possibility in the next to minimal supersymmetric standard model (NMSSM). We investigate the potential reach of the light stop mass at the 13 TeV run of the LHC by means of five NMSSM benchmark points where this signature is dominant. These benchmark points are compatible with current Higgs coupling measurements, LHC constraints, dark matter relic density and direct detection constraints. We consider single and di-lepton search strategies, as well as the jet-substructure technique to reconstruct the Higgs bosons. We fin…
The Higgs pair production in gluon fusion is a sensitive probe of beyond-Standard Model (BSM) phenomena and its detection is a major goal for the LHC and higher energy hadron collider experiments. In this work we reanalyze the possible modifications of the Higgs pair production cross section within low energy supersymmetry models. We show that the supersymmetric contributions to the Higgs pair production cross section are strongly correlated with the ones of the single Higgs production in the gluon fusion channel. Motivated by the analysis of ATLAS and CMS Higgs production data, we show that t…
In this work, we study the implication of Higgs precision measurements at future Higgs factories on the MSSM parameter space, focusing on the dominant stop sector contributions. We perform a multi-variable fit to both the signal strength for various Higgs decay channels at Higgs factories and the Higgs mass. The chi-square fit results show sensitivity to mA, tan beta, stop mass parameter mSUSY as well as the stop left-right mixing parameter Xt. We also study the impact of the Higgs mass prediction on the MSSM and compare the sensitivities of different Higgs factories.
We study the prospects for LHC discovery of a narrow resonance that decays to two Higgs bosons, using the final state of two photons and two bottom jets. Our work is motivated in part by a scenario in which two-body flavor-preserving decays of the top squark are kinematically forbidden. Stoponium, a hadronic bound state of the top squark and its anti-particle, will then form, and may have a large branching fraction into the two Higgs boson final state. We estimate the cross-section needed for a 5-sigma discovery at the 14 TeV LHC for such a narrow di-Higgs resonance, using the invariant mass d…
In supersymmetric models the mass of the stops can be considered as the naturalness measure of the theory. Roughly, the lighter the stops are, the more natural the theory is. Both, the absence of supersymmetric signals at experiment and the measurement of the Higgs mass, put scenarios with light stops under increasing tension. I will present a supersymmetry breaking mechanism of the Scherk-Schwarz type that, by introducing extra $SU(2)_L$ triplets in the Higgs sector, is able to generate the correct Higgs mass while keeping stops light.
Current searches for the light top squark (stop) mostly focus on the decay channels of $\tilde{t} \rightarrow t χ_1^0$ or $\tilde{t} \rightarrow b χ_1^\pm \rightarrow bW χ_1^0$, leading to $t\bar{t}/bbWW+\met$ final states for stop pair productions at the LHC. However, in supersymmetric scenarios with light neutralinos and charginos other than the neutralino lightest supersymmetric particle (LSP), more than one decay mode of the stop could be dominant. While those new decay modes could significantly weaken the current stop search limits at the LHC, they also offer alternative discovery channel…
We analyze a minimal flavored gauge mediation model in which the electroweak Higgs and messenger doublets are embedded in multiplets of a discrete non-Abelian symmetry. In this scenario, the minimal Higgs-messenger sector that is consistent with the 125 GeV Higgs mass has two vectorlike pairs of messenger fields. This scenario is obtained in a specific limit of the superpotential interactions of the Higgs-messenger fields and the matter fields. Due to the structure of the messenger-matter Yukawa couplings in this limit, sizable stop mixing and flavor-diagonal soft supersymmetry breaking parame…
Can blind spots save neutralino dark matter in natural supersymmetry models?
University of Oklahoma（俄克拉荷马大学）；University of Wisconsin, Madison（威斯康星大学麦迪逊分校）；INFN, Sezione di Roma, c/o Dip. di Fisica, Sapienza Università di Roma（意大利国家核物理研究所罗马分部，附罗马大学物理系）；University of Cyprus（塞浦路斯大学）
We show that the Higgs portal interactions involving extra dark Higgs field can save generically the original Higgs inflation of the standard model (SM) from the problem of a deep non-SM vacuum in the SM Higgs potential. Specifically, we show that such interactions disconnect the top quark pole mass from inflationary observables and allow multi-dimensional parameter space to save the Higgs inflation, thanks to the additional parameters (the dark Higgs boson mass $m_ϕ$, the mixing angle $α$ between the SM Higgs $H$ and dark Higgs $Φ$, and the mixed quartic coupling) affecting RG-running of the …
Gauge mediation predicts 10 TeV or heavier squarks because such a heavy stop is required to explain the observed 125 GeV Higgs boson mass without a large trilinear soft mass term in the minimal supersymmetric standard model. Although such a high scale cannot be searched by the LHC directly, gauge mediation also predicts a hierarchy $μ^2 \ll B_μ$ by a simple and naive solution of the $μ$ problem. We point out that this simple and naive way of generating the $μ$ ($B_μ$) term works in the case of 10 TeV or heavier squarks with a slight breaking of a GUT relation among messenger B-terms (or supers…
Stop coannihilation may bring the relic density of heavy supersymmetric dark matter particles into the range allowed by cosmology. The efficiency of this process is enhanced by stop-antistop annihilations into the longitudinal (Goldstone) modes of the $W$ and $Z$ bosons, as well as by Sommerfeld enhancement of stop annihilations and the effects of bound states. Since the couplings of the stops to the Goldstone modes are proportional to the trilinear soft supersymmetry-breaking $A$-terms, these annihilations are enhanced when the $A$-terms are large. However, the Higgs mass may be reduced below…
In order to reproduce the measured mass of the Higgs boson mh = 125GeV in the minimal supersymmetric standard model, one usually has to rely on heavy stops, increasing the fine tuning of the electroweak scale. By introducing a new gauge sector, the Higgs mass gets a tree-level contribution via a non-decoupling D-term, and mh = 125 GeV can be obtained with lighter stops. In this paper, we study the values of the stops masses needed to achieve the correct Higgs mass in a setup where the gauge group is extended by a single U(1)x interaction. We derive the experimental limits on the mass of the Z'…
