Narrow Results

We evaluate the total cross-sections of top-charm associated production induced by SUSY–QCD FCNC at the LHC within the general unconstrained MSSM framework. Our results show that these production rates may be as large as a few pb for favorable parameter values allowing by current precise experiments. It means that the LHC may produce abundant events of this process, and the SUSY FCNC effects through the above process may be observable in the future experiments.

We compute the rates for annihilation into charginos and neutralinos by taking into account the effects of supersymmetric soft phases. In particular, the phase of the μ parameter gains direct accessibility via the production of dissimilar charginos and neutralinos. The phases of the trilinear soft masses do not have a significant effect on the cross-sections. Our results can be important for sparticle searches at the LHC.

This review starts with a brief introduction to the charged Higgs boson (H^±) in the Minimal Supersymmetric Standard Model (MSSM). It then discusses the prospects of a relatively light H^± boson search via top quark decay at Tevatron/LHC, and finally a heavy H^± boson search at LHC. The viable channels for H^± search are identified in both the cases, with particular emphasis on the H^±→τν decay channel. The effects of NLO QCD correction in the SM as well as the MSSM are discussed briefly.

The MSSM contains CP-violating phases that may have important observable effects in Higgs physics. We review recent highlights in Higgs phenomenology obtained with the code CPsuperH, a useful tool for studies of the production, mixing and decay of a coupled system of the neutral Higgs bosons at future high energy colliders such as the LHC, ILC (γLC), and a muon collider (MC). CPsuperH implements the constraints from upper limits on electric dipole moments, and may be extended to include other related low-energy observables, such as b→sγ and B→Kl l, and to compute the relic abundance of the lightest neutralino.

We investigate the focus points of the renormalization group equations of the minimal supersymmetric standard model. We show that within this model the up- and down-type Higgs mass soft supersymmetry breaking parameters have focus point behavior at the electroweak scale simultaneously when appropriate conditions are fulfilled. The focus point scenario holds for large tan β. This two-focus-point scenario allows to fix the pole top-quark mass which is within the experimentally allowed interval. The main goal of this paper is the investigation of the influence of the existence of focus points on the determination of the mass of the lightest Higgs boson.

In the minimal supersymmetric extension of the Standard Model (MSSM) the interactions between the SUSY particles and the Standard Model (SM) particles can contribute to the lepton flavor violation (LFV) decays of vector mesons at loop level. Taking the constraint on the lightest Higgs mass around 126 GeV, we study these decays by a scan over the parameter space which gives the predictions on μ-e conversion and τ→μγ satisfying the experimental bounds. The branching ratios of the vector mesons decays into eμ are strongly suppressed. However, the branching ratios of the heavy flavor mesons decays into τμ can reach the experimental sensitivity in near future. Therefore, the experimental signals of these decays may serve as a probe of the MSSM.

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.

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 analyze the one-loop correction to $Z\to \nu \nu$ decay in framework of Minimal R-symmetric Supersymmetric Standard Model (MRSSM) in detail with normal and inverse neutrino mass orderings, as a function of $\mathrm{\text{tan}}\beta$, Dirac mass parameters $M_D^W$ and ${\mu }_u({\mu }_d)$, slepton mass $m_l$ that parametrize the mass matrices. The numerical results indicate that the branching ratio for $Z\to \nu \nu$ decay is compatible with the experimental measurement and the SM expectation at $2\sigma$ level. For inverse neutrino mass ordering, the prediction exceeds the SM expectation at $1\sigma$ level. The prediction on $\mathrm{\text{Br}}(Z\to \nu \nu )$ increases proportionally to $\mathrm{\text{tan}}\beta$ and inversely proportionally to $m_l$. For normal neutrino mass ordering, the peak value of the prediction on $\mathrm{\text{Br}}(Z\to \nu \nu )$ exceeds the SM expectation at $1\sigma$ level.

Different production processes involving the Higgs boson, such as annihilation and W/Z boson fusion, will be observed in the International Linear Collider (ILC). The ILC operates at a center-of-mass (CM) energy of $\sqrt{s}=200$–1000GeV. The study reveals that the production cross-section can either be enhanced or reduced depending on the CM energy and the specific combination used, which has implications for selecting appropriate production processes. Additionally, this investigation highlights that by polarizing beams, the number of measurable observables increases. These observables, such as left–right asymmetry, detailed effective polarization, and adequate effective luminosity, are crucial to ascertain contemporary physical parameters in physics models absurdly the Standard Model (SM).

We present the results of a search for charged Higgs in the decay products of at the CDF II detector at the Tevatron. The search is based on the cross section measurements of production in three exclusive decay channels: dilepton, lepton + jets and lepton + hadronic tau. Assuming the charged Higgs decays only via , and , and , limits in the MSSM (m_Higgs, tan(β)) plane are obtained at tree level. A model-independent analysis is introduced in which the results are independent of Higgs branching ratios. This analysis results in BR(t→Hb)<0.7 at 95%CL for 80 GeV<m_Higgs<150 GeV.

We present the results of a search for a neutral MSSM Higgs boson decaying to a pair of tau leptons. The analyzed data sample corresponds to integrated luminosity of approximately 200 pb^-1 of collisions at . It was collected by the CDF detector during Run 2 of the Fermilab Tevatron. We select tau pairs in which one of the taus decays hadronically and the other to e or μ and neutrinos. We see no evidence of signal and perform a fit to the (partially) reconstructed di-tau mass to set limits on the product of Higgs production cross-section and its branching fraction to taus.

We present results for the production cross section of a Higgs boson with a pair of quarks, including next-to-leading order (NLO) QCD corrections.

The present constraints from electroweak radiative corrections suggest that the low mass region will be particularly interesting in future Higgs boson searches. In this paper, the discovery potential for a search of a low mass Standard Model Higgs boson, as well as the sensitivity to the lightest Higgs boson of the MSSM (h) are presented as a function of the collected luminosity, for the ATLAS experiment at the LHC.

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 running mass of the b-quark defined in -scheme is one of the important parameters of SUSY QCD. To find its value, it should be related to some known experimental input. In this paper, the b-quark running mass defined in nonsupersymmetric QCD is chosen for determination of the corresponding parameter in SUSY QCD. The relation between these two quantities is found by considering five-flavor QCD as an effective theory obtained from its supersymmetric extension. A numerical analysis of the calculated two-loop relation and its impact on the MSSM spectrum is discussed. Since for nonsupersymmetric models -scheme is more natural than , we also propose a new procedure that allows one to calculate relations between - and -parameters. Unphysical ε-scalars that give rise to the difference between the above-mentioned schemes are assumed to be heavy and decoupled in the same way as physical degrees of freedom. By means of this method it is possible to "catch two rabbits," i.e. decouple heavy particles and turn from to , at the same time. An explicit two-loop example of transition is given in the context of QCD. The advantages and disadvantages of the method are briefly discussed.

We write explicit and self-contained asymptotic expressions for the tensorial B, C and D Passarino–Veltman functions. These include quadratic and linear logarithmic terms, as well as subleading constant terms. Only mass-suppressed contributions are neglected. We discuss the usefulness of such expressions, particularly for studying one-loop effects in 2-to-2 body processes at high energy.

Although in the framework of the Standard Model (SM) of particles, Lepton Flavor Violating (LFV) processes such as µ → eγ, µ → eee and µN → eN are strictly forbidden, in various beyond SM scenarios such as Minimal Supersymmetric Standard Model (MSSM), new sources of LFV appear that can lead to sizeable rates for these processes. There are on-going experiments that search for the LFV processes. If the rates of these processes are close to the present bound, these experiments will collect abundant amount of data which makes precision measurement of LFV parameters a close possibility. We show that by studying the polarization of the final particles, information on the CP-violating phases of the underlying theory can be also derived. We discuss the possibility to reduce the degeneracy of parameters by combining information from various experiments.

Masses of heavy Standard Model (SM) fermions (top-quark, bottom-quark and tau-lepton) play an important role in the analysis of theories beyond the SM. They serve as low-energy input and reduce the parameter space of such theories. In this paper Minimal supersymmetric extension of the SM is considered and two-loop relations between known SM values of fermion masses and running parameters of the MSSM are studied within the effective theory approach. Both b-quark and τ-lepton have the same quantum numbers with respect to SU(2) group and in the MSSM acquire their masses due to interactions with the same Higgs doublet. As a consequence, for large values of tan β parameter corresponding Yukawa couplings also become large and together with tan β can significantly enhance radiative corrections. In the case of b-quark two-loop contribution to the relation between running bottom-quark mass in QCD and MSSM is known in literature. This paper is devoted to calculation of the NNLO corrections proportional to Yukawa couplings. For the τ-lepton obtained contribution can be considered as a good approximation to the full two-loop result. For the b-quark numerical analysis given in the paper shows that only the sum of strong and Yukawa corrections can play such a role.

We present a complete and minimal catalogue of MSSM gauge invariant monomials. That is, the catalogue of Gherghetta, Kolda and Martin is elaborated to include generational structure for all monomials. Any gauge invariant operator can be built as a linear combination of elements of the catalogue lifted to nonnegative integer powers. And the removal of any one of the monomials would deprive the catalogue of this feature. It contains 712 monomials, plus 3 generations of right-handed neutrinos if one extends the model to the νMSSM. We note that νMSSM flat directions can all be lifted by the sixth-order superpotential compared to the ninth-order needed in MSSM.