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Register a new userOne-loop corrections to neutralino-stop coannihilation revisited
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We discuss the ${cal O}(alpha_s)$ supersymmetric QCD corrections to neutralino-stop coannihilation into a top quark and a gluon in the Minimal Supersymmetric Standard Model (MSSM). This particular channel can be numerically important in wide ranges of the MSSM parameter space with rather light stops. We discuss technical details such as the renormalization scheme and the phase-space slicing method with two cutoffs. We also comment on improvements with respect to earlier works on the given process. Further, we study for the first time the phenomenologically very interesting interplay of neutralino-stop coannihilation with neutralino-pair annihilation into quark pairs taking the full next-to-leading order SUSY-QCD corrections into account. We demonstrate that the numerical impact of these corrections on the total (co)annihilation cross section and finally on the theoretically predicted neutralino relic density is significant.
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The extracted value of the relic density has reached the few per-cent level precision. One can therefore no longer content oneself with calculations of this observable where the annihilation processes are computed at tree-level, especially in supersymmetry where radiative corrections are usually large. Implementing full one-loop corrections to all annihilation processes that would be needed in a scan over parameters is a daunting task. On the other hand one may ask whether the bulk of the corrections are taken into account through effective couplings of the neutralino that improve the tree-level calculation and would be easy to implement. We address this issue by concentrating in this first study on the neutralino coupling to i) fermions and sfermions and ii) Z. After constructing the effective couplings we compare their efficiency compared to the full one-loop calculation and comment on the failures and success of the approach. As a bonus we point out that large non decoupling effects of heavy sfermions could in principle be measured in the annihilation process, a point of interest in view of the latest limit on the squark masses from the LHC. We also comment on the scheme dependencies of the one-loop corrected results.
We compute the full O(alpha_s) supersymmetric QCD corrections for neutralino-stop co-annihilation into electroweak gauge and Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM). We show that these annihilation channels are phenomenologically relevant within the so-called phenomenological MSSM, in particular in the light of the observation of a Higgs-like particle with a mass of about 126 GeV at the LHC. We present in detail our calculation, including the renormalization scheme, the infrared treatment, and the kinematical subtleties to be addressed. Numerical results for the co-annihilation cross sections and the predicted neutralino relic density are presented. We demonstrate that the impact of including the corrections on the cosmologically preferred region of parameter space is larger than the current experimental uncertainty from WMAP data.
We have calculated the full O(alpha_s) supersymmetric QCD corrections to neutralino-stop co-annihilation into electroweak vector and Higgs bosons within the Minimal Supersymmetric Standard Model (MSSM). We performed a parameter study within the phenomenological MSSM and demonstrated that the studied co-annihilation processes are phenomenologically relevant, especially in the context of a 126 GeV Higgs-like particle. By means of an example scenario we discuss the effect of the full next-to-leading order corrections on the co-annihilation cross section and show their impact on the predicted neutralino relic density. We demonstrate that the impact of these corrections on the cosmologically preferred region of parameter space is larger than the current experimental uncertainty of WMAP data.
We have calculated the two-loop strong interaction corrections to the neutralino pole masses in the DRbar-scheme in the Minimal Supersymmetric Standard Model (MSSM). We have performed a detailed numerical analysis for a particular point in the parameter space and found corrections of a few tenths of a percent. We agree with previously derived analytic formulae for two-loop corrections to fermion masses.
We study the process of the association production of chargino and neutralino including the NLO QCD and the complete one-loop electroweak corrections in the framework of the minimal supersymmetric standard model(MSSM) at the Fermilab Tevatron and the CERN Large Hadron Collider (LHC). In both the NLO QCD and one-loop electroweak calculations we apply the algorithm of the phase-space slicing(PSS) method. We find that the NLO QCD corrections generally increase the Born cross sections, while the electroweak relative corrections decrease the Born cross section in most of the chosen parameter space. The NLO QCD and electroweak relative corrections typically have the values of about 32% and -8% at the Tevatron, and about 42% and -6% at the LHC respectively. The results show that both the NLO QCD and the complete one-loop electroweak corrections to the processes $p bar p/pp to widetilde{chi}_1^{pm} widetilde{chi}_2^0+X$ are generally significant and should be taken into consideration in precision experimental analysis.
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