arXiv subjects

Dominik Stöckinger

Publications and source records attributed to Dominik Stöckinger.

At least 73 records · Page 4Linked to original sources

arXiv2013

Non-decoupling two-loop corrections to (g-2)_μ from fermion/sfermion loops in the MSSM

Two-loop contributions to the muon (g-2) from fermion/sfermion loops in the MSSM are presented, and an overview of the full MSSM prediction for (g-2) is given with emphasis on the behaviour in scenarios which are compatible with LHC data, including scenarios with large mass splittings. Compared to all previously known two-loop contributions, the fermion/sfermion-loop contributions can yield the largest numerical results. The new contributions contain the important universal quantities Δα and Δρ, and for large sfermion masses the contributions are non-decoupling and logarithmically enhanced. We find up to 15% (30%) corrections for sfermion masses in the 20 TeV (1000 TeV) range.

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arXiv2013

Renormalization of vacuum expectation values in spontaneously broken gauge theories: Two-loop results

We complete the two-loop calculation of beta-functions for vacuum expectation values (VEVs) in gauge theories by the missing O(g^4)-terms. The full two-loop results are presented for generic and supersymmetric theories up to two-loop level in arbitrary R_xi-gauge. The results are obtained by means of a scalar background field, identical to our previous analysis. As a by-product, the two-loop scalar anomalous dimension for generic supersymmetric theories is presented. As an application we compute the beta-functions for VEVs and tan(beta) in the MSSM, NMSSM, and E6SSM.

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arXiv2013

Renormalization of vacuum expectation values in spontaneously broken gauge theories

We compute one-loop and two-loop beta-functions for vacuum expectation values (VEVs) in gauge theories. In R_xi gauge the VEVs renormalize differently from the respective scalar fields. We focus particularly on the origin and behavior of this difference and show that it can be interpreted as the anomalous dimension of a certain scalar background field, leading to simple direct computation and qualitative understanding. The results are given for generic as well as supersymmetric gauge theories. These complement the set of well-known gamma- and beta-functions of Machacek/Vaughn. As an application, we compute the beta-functions for VEVs and tan(beta) in the MSSM, NMSSM and E6SSM.

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arXiv2012

Threshold Corrections in the Exceptional Supersymmetric Standard Model

We calculate threshold corrections to the running gauge and Yukawa couplings in the Exceptional Supersymmetric Standard Model (E6SSM) and analyse the more precise and reliable mass spectra in a constrained model (CE6SSM). Full expressions for the corrections are provided and the implementation into a spectrum generator is described. We find a dramatic reduction in the matching scale dependency of the masses of many states and observe a significant adjustment of the correlation of low-scale physical masses and high-scale parameters. Still, in substantial regions of parameter space the mass of the lightest Higgs is compatible with the new boson discovered at the LHC and the model satisfies limits from collider searches for squark, gluinos and Z' bosons. We study the implications for gauge coupling unification from a new dependency of the spectrum on so-called survival Higgs fields which cannot be addressed without the inclusion of the threshold corrections.

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arXiv2011

FeynArts model file for MSSM transition counterterms from DREG to DRED

The FeynArts model file MSSMdreg2dred.mod implements MSSM transition counterterms which can convert one-loop Green functions from dimensional regularization to dimensional reduction. They correspond to a slight extension of the well-known Martin/Vaughn counterterms, specialized to the MSSM, and can serve also as supersymmetry-restoring counterterms. The paper provides full analytic results for the counterterms and gives one- and two-loop usage examples. The model file can simplify combining MSbar-parton distribution functions with supersymmetric renormalization or avoiding the renormalization of epsilon-scalars in dimensional reduction.

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arXiv2008

Dimensional Reduction and Hadronic Processes

We consider the application of regularization by dimensional reduction to NLO corrections of hadronic processes. The general collinear singularity structure is discussed, the origin of the regularization-scheme dependence is identified and transition rules to other regularization schemes are derived.

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arXiv2008

Tan(beta)-enhanced supersymmetric corrections to the anomalous magnetic moment of the muon

We report on a two-loop supersymmetric contribution to the magnetic moment (g-2)_mu of the muon which is enhanced by two powers of tan(beta). This contribution arises from a shift in the relation between the muon mass and Yukawa coupling and can increase the supersymmetric contribution to (g-2)_mu sizably. As a result, if the currently observed 3 sigma deviation between the experimental and SM theory value of (g-2)_mu is analyzed within the Minimal Supersymmetric Standard Model (MSSM), the derived constraints on the parameter space are modified significantly: If (g-2)_mu is used to determine tan(beta) as a function of the other MSSM parameters, our corrections decrease tan(beta) by roughly 10% for tan(beta)=50.

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arXiv2007

(g-2)_mu and supersymmetry: status and prospects

The experimental determination of the muon magnetic moment and its theoretical prediction within the Standard Model and the MSSM are reviewed. A 3 sigma deviation between experiment and Standard Model prediction has been established, and supersymmetry could provide a natural explation of this deviation. Possible future improvements and the case for a new experiment are discussed.

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arXiv2006

The Muon Magnetic Moment and Supersymmetry

The present review is devoted to the muon magnetic moment and its role in supersymmetry phenomenology. Analytical results for the leading supersymmetric one- and two-loop contributions are provided, numerical examples are given and the dominant tan(beta)sign(mu)/M_SUSY^2 behaviour is qualitatively explained. The consequences of the Brookhaven measurement are discussed. The 2 sigma deviation from the Standard Model prediction implies preferred ranges for supersymmetry parameters, in particular upper and lower mass bounds. Correlations with other observables from collider physics and cosmology are reviewed. We give, wherever possible, an intuitive understanding of each result before providing a detailed discussion.

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arXiv2006

Regularization of supersymmetric theories - recent progress

General issues concerning the regularization of supersymmetric theories using dimensional regularization and dimensional reduction are reviewed. Recent progress on problems of dimensional reduction related to factorization, supersymmetry, Higgs boson mass calculations, and mathematical consistency is discussed.

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arXiv2005

MSSM Higgs-boson mass predictions and two-loop non-supersymmetric counterterms

The evaluation of Yukawa-enhanced two-loop contributions to the MSSM Higgs-boson mass is considered. We prove the common assumption that regularization by dimensional reduction preserves supersymmetry at the required level. Thus generating counterterms by multiplicative renormalization is correct. Technically, we identify a suitable Slavnov-Taylor identity, use a recently developed method to evaluate it at the two-loop level, and show that it is valid in dimensional reduction.

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arXiv2005

Factorization and Regularization by Dimensional Reduction

Since an old observation by Beenakker et al, the evaluation of QCD processes in dimensional reduction has repeatedly led to terms that seem to violate the QCD factorization theorem. We reconsider the example of the process gg->ttbar and show that the factorization problem can be completely resolved. A natural interpretation of the seemingly non-factorizing terms is found, and they are rewritten in a systematic and factorized form. The key to the solution is that the D- and (4-D)-dimensional parts of the 4-dimensional gluon have to be regarded as independent partons.

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arXiv2005

Regularization by Dimensional Reduction: Consistency, Quantum Action Principle, and Supersymmetry

It is proven by explicit construction that regularization by dimensional reduction can be formulated in a mathematically consistent way. In this formulation the quantum action principle is shown to hold. This provides an intuitive and elegant relation between the D-dimensional Lagrangian and Ward or Slavnov-Taylor identities, and it can be used in particular to study to what extent dimensional reduction preserves supersymmetry. We give several examples of previously unchecked cases.

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arXiv2005

Regularization of supersymmetric theories: Recent improvements

Recent progress concerning regularization of supersymmetric theories is reviewed. Dimensional reduction is reformulated in a mathematically consistent way, and an elegant and general method is presented that allows to study the supersymmetry-invariance of dimensional reduction in an easy manner. This method is applied to several supersymmetry identities at the one- and two-loop level, and thus the extent to which dimensional reduction is known to preserve supersymmetry is significantly enlarged.

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arXiv2004

The anomalous magnetic moment of the muon in the MSSM - recent developments

We present recent results of two interesting classes of supersymmetric two-loop contributions to (g-2)_mu. Two-loop diagrams involving either a closed sfermion loop or a closed chargino/neutralino loop can amount to 5*10^{-10}, which is almost one standard deviation of the current experimental uncertainty. We discuss the dependence of these two classes on the unknown supersymmetric parameters and their impact on the supersymmetric prediction of (g-2)_mu.

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arXiv2004

Supersymmetric two-loop contributions to the anomalous magnetic moment of the muon

Recent results of two interesting classes of supersymmetric two-loop contributions to (g-2)_mu are presented. Two-loop diagrams involving a closed sfermion loop can amount to 5*10^{-10} or almost one standard deviation of the current experimental uncertainty, and two-loop diagrams with a closed chargino/neutralino loop can be similarly large. The dependence of these two classes on the unknown supersymmetric parameters and the sensitivity on existing experimental constraints on the parameter space are quite different. We also comment on the calculational techniques, in particular the large mass expansion and the treatment of gamma_5 and the epsilon-tensor.

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arXiv2004

Electroweak and supersymmetric two-loop corrections to (g-2)_μ

We present the up to now most precise evaluation of electroweak and supersymmetric contributions to the anomalous magnetic moment of the muon \amu, describing in detail also the calculational techniques. We calculate the bosonic two-loop contributions in the Standard Model without the approximation of a heavy Higgs-boson mass, finding corrections up to 0.2*10^{-10} for a light Higgs boson. In the Minimal Supersymmetric Standard Model the corresponding two-loop contributions from the two-Higgs-doublet model part differ from the Standard Model result by up to 0.3*10^{-10}. Finally, we evaluate the diagrams where a loop of charginos or neutralinos, the superpartners of gauge and Higgs bosons, is inserted into a two-Higgs-doublet one-loop diagram. These corrections can amount up to 10*10^{-10}, which is almost 2σof the current experimental uncertainty.

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arXiv2004

Gauge dependence and renormalization of $\tanβ$ in the MSSM

Well-known and newly developed renormalization schemes for $\tanβ$ are analyzed in view of three desirable properties: gauge independence, process independence, and numerical stability in perturbation theory. Arguments are provided that no scheme can meet all three requirements, and as an illustration, a ``No-Go-Theorem'' for the renormalization of $\tanβ$ is established. Nevertheless, two particularly attractive schemes emerge. A discussion about which scheme might be the best compromise in practice is given.

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