Search

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 → ß-Γ 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. [ABSTRACT FROM AUTHOR]

Flavor violating processes in the quark and lepton sectors are investigated within a realistic supersymmetric SO(10)×A4 grand unification model. By employing exotic heavy fermion fields, this model successfully describes various features of the fermion masses and mixings including large neutrino mixings accompanied by small quark mixings. In this model the flavor violation is induced at GUT scale, at which A4 flavor symmetry is broken, as a consequence of the large mixings of the light fermion fields with these exotic heavy fields. The stringent experimental constraint from μ→eγ decay rate necessitates a high degree of degeneracy of the supersymmetry breaking soft scalar masses of the exotic heavy fields and supersymmetric scalar partners of the light fermion fields. The choice of slepton masses of order 1 TeV is found to be consistent with the constraints from branching ratio of μ→eγ and with all other flavor changing neutral current processes being sufficiently suppressed. [ABSTRACT FROM AUTHOR]

Abstract: A search for neutral Higgs bosons decaying to pairs of τ leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton–proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb−1. After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson ϕ as a function of the Higgs boson mass and for production in the Minimal Supersymmetric Standard Model (MSSM) as a function of the parameters and . [Copyright &y& Elsevier]

We study the cross-section of heavy Higgs production at the LHC within the framework of the constrained MSSM. It is not only enhanced by tan2β but sometimes is also enhanced by the squark contribution. First, we consider the universal scenario within mSUGRA and find out that to get the desired enhancement one needs large negative values of A0, which seems to be incompatible with the b → sγ decay rate. To improve the situation, we release the unification requirement in the Higgs sector. Then it becomes possible to satisfy all requirements simultaneously and enhance the squark contribution. The latter can gain a factor of several units increasing the overall cross-section which, however, is still smaller than the cross-section of the associated $Hb\bar b$ production. We consider also some other consequences of the chosen benchmark point. [ABSTRACT FROM AUTHOR]

We construct supersymmetric Pati-Salam flux vacua in AdS from intersecting D6-branes on T6/(ℤ2 × ℤ′2). The models constructed have three generations of MSSM matter plus right-handed neutrinos. Because the cycles wrapped by the D-branes are rigid there are no extra massless fields in the adjoint representation, arising as open-string moduli. However, we find that it is problematic to break the Pati-Salam gauge symmetry to the Standard Model (SM) while keeping the SM hypercharge massless. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: We construct a four-generation MSSM with rank-4 Yukawa matrices from intersecting D6 branes on a orientifold. The Yukawa matrices obtained provide an example of Flavor Democracy (FD), where the Yukawa couplings are all nearly equal. Mass hierarchies may then be generated by slight perturbations away from FD. We find that it is possible to obtain hierarchical masses for the quarks and leptons of each generation and mixings between them. In addition, the tree-level gauge couplings are unified at the string scale. Finally, we also construct similar models with one, two, and three generations in which the rank of the Yukawa matrices is equal to the number of generations in each model. [Copyright &y& Elsevier]

Abstract: We consider the possible anomaly free Abelian discrete symmetries of the MSSM that forbid the μ-term at perturbative order. Allowing for anomaly cancellation via the Green–Schwarz mechanism we identify discrete R-symmetries as the only possibility and prove that there is a unique symmetry that commutes with . We argue that non-perturbative effects will generate a μ-term of electroweak order thus solving the μ-problem. The non-perturbative effects break the symmetry leaving an exact matter parity. As a result dimension four baryon- and lepton-number violating operators are absent while, at the non-perturbative level, dimension five baryon- and lepton-number violating operators get induced but are highly suppressed so that the nucleon decay rate is well within present bounds. [Copyright &y& Elsevier]

Abstract: In this Letter, we reevaluated the Higgs-mediated contribution to , , and conversion in nuclei in the MSSM, assuming left-handed sleptons have flavor-mixing mass terms. Contrary to previous works, it is found that Barr–Zee diagrams including top quark give dominant contribution to , and those including bottom quark and tau lepton are also non-negligible only when is large. As a result, the Higgs-mediated contribution dominates over the gaugino-mediated contribution at one-loop level in when , irrespectively of as far as is not large. Here, and are a typical mass scale of the SUSY particles and the CP-odd Higgs boson mass, respectively. Ratio of branching ratios for and conversion in nuclei is also evaluated by including both the gaugino- and Higgs-mediated contributions to the processes. It is found that the ratio is sensitive to and when and . [Copyright &y& Elsevier]

Abstract: Using the formalism of constrained superfields, we derive the most general effective action of a light goldstino coupled to the minimal supersymmetric standard model (MSSM) and study its phenomenological consequences. The goldstino-induced couplings become important when the (hidden sector) scale of spontaneous supersymmetry breaking, , is relatively low, of the order of few TeV. In particular, we compute the Higgs potential and show that the (tree level) mass of the lightest Higgs scalar can be increased to the LEP bound for to 7 TeV. Moreover, the effective quartic Higgs coupling is increased due to additional tree-level contributions proportional to the ratio of visible to hidden sector supersymmetry breaking scales. This increase can alleviate the amount of fine tuning of the electroweak scale that exists in the MSSM. Among the new goldstino couplings, beyond those in MSSM, the most important ones generate an invisible decay of the Higgs boson into a goldstino and neutralino (if ), with a partial decay rate that can be comparable to the SM channel . A similar decay of Z boson is possible if and brings a lower bound on that must be of about 700 GeV. Additional decay modes of the Higgs or Z bosons into a pair of light goldstinos, while possible, are suppressed by an extra factor and have no significant impact on the model. [Copyright &y& Elsevier]

We expand the superpotential of νMSSM to sixth order. This is the order at which all flat directions can be lifted. All 5179 (complex) couplings are independent, i.e. the superpotential cannot be zero for all fields, without all couplings being zero. Likewise, any gauge invariant potential to the sixth order can be made by fixing the constants. A specific and well-defined choice of normalization has been adopted. The case for investigating this potential, rather than looking at one or several generalized flat directions is made. [ABSTRACT FROM AUTHOR]

Abstract: We study the MSSM in F-theory. Its group is the commutant to a structure group of a gauge bundle in . The spectrum contains three generations of quarks and leptons plus vectorlike electroweak and colored Higgses. The minimal MSSM Yukawa couplings with matter parity is obtained at the renormalizable level. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

We study the pair production of scalar quark in a muon collider within the MSSM with CP violation. We show that including the CP phases can strongly affect the cross section of the process: $\mu^{+}\mu^{-}\rightarrow \tilde{q}_{i}\bar{\tilde{q}}_{j}$. This could have an important impact on the search for squarks and the determination of the MSSM parameters at future colliders. [ABSTRACT FROM AUTHOR]

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 ${\mathcal O}(\alpha_s^2)$ 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. [ABSTRACT FROM AUTHOR]

Abstract: If SUSY provides a solution to the hierarchy problem then supersymmetric states should not be too heavy. This requirement is quantified by a fine tuning measure that provides a quantitative test of SUSY as a solution to the hierarchy problem. The measure is useful in correlating the impact of the various experimental measurements relevant to the search for supersymmetry and also in identifying the most sensitive measurements for testing SUSY. In this Letter we apply the measure to the CMSSM, computing it to two-loop order and taking account of current experimental limits and the constraint on dark matter abundance. Using this we determine the present limits on the CMSSM parameter space and identify the measurements at the LHC that are most significant in covering the remaining parameter space. Without imposing the LEP Higgs mass bound we show that the smallest fine tuning () consistent with a relic density within the WMAP bound corresponds to a Higgs mass of . Fine tuning rises rapidly for heavier Higgs. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

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 $\mathcal{O}(m^2/s)$ 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. [ABSTRACT FROM AUTHOR]

The running mass of the b-quark defined in $\overline{\rm DR}$-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 $\overline{\rm MS}$-scheme is more natural than $\overline{\rm DR}$, we also propose a new procedure that allows one to calculate relations between $\overline{\rm MS}$- and $\overline{\rm DR}$-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 $\overline{\rm DR}$ to $\overline{\rm MS}$, at the same time. An explicit two-loop example of $\overline{\rm DR} \to \overline{\rm MS}$ transition is given in the context of QCD. The advantages and disadvantages of the method are briefly discussed. [ABSTRACT FROM AUTHOR]

We discuss the pair production of scalar quarks in e + e − annihilation within the MSSM with complex parameters. We calculate the SUSY-QCD corrections to the cross section $$e^{+} e^{-}\rightarrow \tilde{q}_i\bar{\tilde{q}}_j\; (i, j=1, 2)$$ and show that the effect of the CP phases of these complex parameters on the cross section can be quite strong in a large region of the MSSM parameter space. This could have important implications for squarks searches and the MSSM parameter determination in future collider experiments. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract: We analyze the parameter space of the (, ) CMSSM at large with a small degree of non-universality originating from D-terms and Higgs-sfermion splitting inspired by GUT models. The effects of such non-universalities on the sparticle spectrum and observables such as , , the SUSY threshold corrections to the bottom mass and are examined in detail and the consequences for the allowed parameter space of the model are investigated. We find that even small deviations to universality can result in large qualitative differences compared to the universal case; for certain values of the parameters, we find, even at low and , that radiative electroweak symmetry breaking fails as a consequence of either or . We find particularly large departures from the mSugra case for the neutralino relic density, which is sensitive to significant changes in the position and shape of the resonance and a substantial increase in the Higgsino component of the LSP. However, we find that the corrections to the bottom mass are not sufficient to allow for Yukawa unification. [Copyright &y& Elsevier]

The feasibility of detecting a heavy charged Higgs boson,m H±>m t+m b, decaying in theH±?tbchannel is studied with the fast simulation of the ATLAS detector. We study thegg?H± tbproduction process at the LHC which together with the aforementioned decay channel leads to fourb-quarks in the final state. The whole production and decay chain reads. Combinatorial background is a major difficulty in this multi-jet environment but can be overcome by employing multivariate techniques in the event reconstruction. Requiring fourb-tagged jets in the event helps to effectively suppress the Standard Model backgrounds but leads to no significant improvement in the discovery potential compared to analyses requiring only threeb-tagged jets. This study indicates that charged Higgs bosons can be discovered at the LHC up to high masses (m H±>400 GeV) in the case of large tanß.Keywords:charged Higgs; MSSMPACS:14.80.Cp - 12.60.Jv - 11.10.Kk [ABSTRACT FROM AUTHOR]

Abstract: We evaluate the and productions at the LHC within the general unconstrained MSSM framework. We find that these single top quark productions induced by SUSY-QCD FCNC couplings have remarkable cross sections for favorable parameter values allowed by current low energy data, which can be as large as a few pb. Once large rates of the and productions are detected at the LHC, they may be induced by SUSY FCNC couplings. We show that the precise measurement of single top quark production cross sections at the LHC is a powerful probe for the details of the SUSY FCNC couplings. [Copyright &y& Elsevier]

Abstract: The Letter is devoted to the calculation of the two-loop and MSSM corrections to the relation between the pole mass of the b-quark and its running mass in the scheme. To evaluate the needed diagrams the large mass expansion procedure is used. The obtained contributions are negative in most of the regions of the parameter space and partly compensate the positive contribution calculated earlier. [Copyright &y& Elsevier]

Abstract: We have developed the system for the automatic computation of cross-sections, GRACE/SUSY, including the one-loop calculations for processes of the minimal supersymmetric extension of the standard model. For an application, we investigate the process . [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

We compute the rates for $q\bar q$ 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An ansatz, DetMH˜=0, for the Higgsino mass matrix is suggested toward the minimal supersymmetric standard model (MSSM). Small instanton solutions effective around the GUT scale can fulfill this condition. An argument that the couplings contain a moduli field is given for a dynamical realization of this Higgsino mass matrix ansatz. We also present a string orbifold trinification toward this realization. [Copyright &y& Elsevier]

Results of a new study of the discovery potential within mSUGRA parameter space of inclusive searches for SUSY at ATLAS are presented. These results indicate that superior performance is provided by the jets + E Tmiss channel in which no requirements are placed upon lepton multiplicity. The sensitivity of this and other channels is mapped in m0 - m1/2 parameter space for four different values of tan(β) with similar performance being obtained in all cases. Inclusive measurements of the effective mass scale Msusyeff and total production cross-section σsusy of supersymmetric particles are also discussed and results presented of a study of the likely measurement precisions. [ABSTRACT FROM AUTHOR]

We compute the QCD corrections at next-to-leading order to the effective Hamiltonian for BB¯ and KK¯ mixing in the Minimal Supersymmetric Standard Model with minimal flavour violation. We take into account the region of low tanβ and focus on QCD corrections to the box diagrams mediated by one additional gluon. [Copyright &y& Elsevier]