Narrow Results

The matter spectrum of the MSSM, including three right-handed neutrino supermultiplets and one pair of Higgs–Higgs conjugate superfields, can be obtained by compactifying the E₈ ×E₈ heterotic string and M-theory on Calabi–Yau manifolds with specific SU(4) vector bundles. These theories have the standard model gauge group augmented by an additional gauged U(1)_B-L. Their minimal content requires that the B-L gauge symmetry be spontaneously broken by a vacuum expectation value of at least one right-handed sneutrino. In previous papers, we presented the results of a quasianalytic renormalization group analysis showing that B-L gauge symmetry is indeed radiatively broken with an appropriate B-L/electroweak hierarchy. In this paper, we extend these results by (1) enlarging the initial parameter space and (2) explicitly calculating the renormalization group equations numerically. The regions of the initial parameter space leading to realistic vacua are presented and the B-L/electroweak hierarchy computed over these regimes. At representative points, the mass spectrum for all sparticles and Higgs fields is calculated and shown to be consistent with present experimental bounds. Some fundamental phenomenological signatures of a nonzero right-handed sneutrino expectation value are discussed, particularly the cosmology and proton lifetime arising from induced lepton and baryon number violating interactions.

Various aspects of the Higgs boson phenomenology of the Minimal Supersymmetric Standard Model (MSSM) are reviewed. Emphasis is put on the effects of higher-order corrections. The masses and couplings are discussed in the MSSM with real and complex parameters. Higher-order corrections to Higgs boson production channels at a prospective e⁺e^- linear collider are investigated. Corrections to Higgs boson decays to SM fermions and their phenomenological implications for hadron and lepton colliders are explored.

The structure of the B–L minimal supersymmetric Standard Model (MSSM) theory — specifically, the relevant mass scales and soft supersymmetric breaking parameters — is discussed. The space of initial soft parameters is explored at the high scale using random statistical sampling subject to a constraint on the range of dimensionful parameters. For every chosen initial point, the complete set of renormalization group equations is solved. The low energy results are then constrained to be consistent with present experimental data. It is shown that a large set of initial conditions satisfy these constraints and lead to acceptable low energy particle physics. Each such initial point has explicit predictions, such as the exact physical sparticle spectrum which is presented for two such points. There are also statistical predictions for the masses of the sparticles and the LSP species which are displayed as histograms. Finally, the fine-tuning of the μ parameter — which is always equivalent to or smaller than in the MSSM — is discussed.

We study the rare decays D⁺→π⁺ℓ⁺ℓ^-, and D⁰→ℓ⁺ℓ^-(ℓ = e, μ) in the minimal supersymmetic standard model with and without R-parity. Using the strong constraints on relevant supersymmetric parameters from mixing and decay, we examine constrained supersymmetry contributions to relevant branching ratios, direct CP violations and ratios of and decay rates. We find that both R-parity conserving LR as well as RL mass insertions and R-parity violating squark exchange couplings have huge effects on the direct CP violations of , moreover, the constrained LR and RL mass insertions still have obvious effects on the ratios of and decay rates. The direct CP asymmetries and the ratios of and decay rates are very sensitive to both moduli and phases of relevant supersymmetric parameters. In addition, the differential direct CP asymmetries of are studied in detail.

In this paper, a study of four different machine learning (ML) algorithms is performed to determine the most suitable ML technique to disentangle a hypothetical supersymmetry (SUSY) signal from its corresponding Standard Model (SM) backgrounds and to establish their impact on signal significance. The study focuses on the production of SUSY top squark pairs (stops), in the mass range of $500<m_{{\tilde{t}}_1}<800$GeV, from proton–proton collisions with a center of mass energy of 13TeV and an integrated luminosity of $140{\mathrm{\text{fb}}}^{-1}$, emulating the data-taking conditions of the run II Large Hadron Collider (LHC) accelerator. In particular, the semileptonic channel is analyzed, corresponding to final states with a single isolated lepton (electron or muon), missing transverse energy, and four jets, with at least one tagged as $b$-jet. The challenging compressed spectra region is targeted, where the stop decays mainly into a $W$ boson, a $b$-jet, and a neutralino (${\tilde{t}}_1\to W+b+{\tilde{\chi }}_1^0$), with a mass gap between the stop and the neutralino of about 150GeV. The ML algorithms are chosen to cover different mathematical implementations and features in ML. We compare the performance of a logistic regression (LR), a Random Forest (RF), an eXtreme Gradient Boosting, XGboost (XG) and a Neural Network (NN) algorithm. Our results indicate that XG and NN classifiers provide the highest improvements (over 17%) in signal significance, when compared to a standard analysis method based on sequential requirements of different kinematic variables. The improvement in signal significance provided by the NN increases up to 31% for the highest stop mass considered in this study (800GeV). The RF algorithm presents a smaller improvement that decreases with stop mass. On the other hand, the LR algorithm shows the worst performance in signal significance which even does not compete with the results obtained by an optimized cut and count method.

Considering the constraints from the current experiment results, we analyze mixing with a Higgs boson around 125 GeV, and discuss the influence of M_A, tanβ to the m_h and Δm_B in the Minimal Supersymmetric Standard Model (MSSM). We find these constraints have a strong impact to the parameters of M_A and tanβ, they almost exclude the small M_A and large tanβ, to have a obvious correction to the mass difference Δm_B we argue that the M_A should not too large, it is possible to observe the M_A boson with a mass 300 ~ 400 GeV in the future.

Studying the properties of the Higgs boson can be an important window to explore the physics beyond the Standard Model (SM). In this work, we present studies on the implications of the Higgs precision measurements at future Higgs Factories. We perform a global fit to various Higgs search channels to obtain the 95% C.L. constraints on the model parameter spaces of two-Higgs Doublet Model (2HDM) and Minimal Supersymmetric Standard Model (MSSM). In the 2HDM, we analyze tree-level effects as well as one-loop contributions from the heavy Higgs bosons. The strong constraints on $cos(\beta -\alpha )$, heavy Higgs masses and their mass splitting are complementary to direct search of the LHC as well as possible future $Z$ pole precision measurements. For the MSSM, we study both the Higgs couplings and mass precisions. The constraints on the CP-odd Higgs mass $m_A$ and stop mass scale $m_{\mathrm{\text{SUSY}}}$ can be complementary to the direct search of HL-LHC. We also compare the sensitivity of various future Higgs factories, namely, Circular Electron Positron Collider (CEPC), Future Circular Collider (FCC)-ee and International Linear Collider (ILC).