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Register a new userCan effective muon g-2 depend on the gravitational potential?
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H. Nikolic
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Contrary to the claim in a series of recent papers, we show that it cannot. A source of the error in those papers is misinterpretation of coordinate time as a physical time.
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According to the FNAL+BNL measurements for the muon $g-2$ and the Berkeley $^{133}$Cs measurement for the electron $g-2$, the SM prediction for the muon (electron) $g-2$ is $4.2sigma$ ($2.4sigma$) below (above) the experimental value. A joint explanation requires a positive contribution to the muon $g-2$ and a negative contribution to the electron $g-2$. In this work we explore the possibility of such a joint explanation in the minimal supersymmetric standard model (MSSM). Assuming no universality between smuon and selectron soft masses, we find out a part of parameter space for a joint explanation of muon and electron $g-2$ anomalies at $2sigma$ level. This part of parameter space can survive the LHC and LEP constraints, but gives an over-abundance for the dark matter if the bino-like lightest neutralino is assumed to be the dark matter candidate. With the assumption that the dark matter candidate is a superWIMP (say a pseudo-goldstino in multi-sector SUSY breaking scenarios, whose mass can be as light as GeV and produced from the late-dacay of the thermally freeze-out lightest neutralino), the dark matter problem can be avoided. So, the MSSM may give a joint explanation for the muon and electron $g-2$ anomalies at $2sigma$ level (the muon $g-2$ anomaly can be ameliorated to $1sigma$).
The difference between the updated experimental result on the muon anomalous magnetic dipole moment and the corresponding theoretical prediction of the standard model on that is about $4.2$ standard deviations. In this work, we calculate the muon anomalous MDM at the two-loop level in the supersymmetric $B-L$ extension of the standard model. Considering the experimental constraints on the lightest Higgs boson mass, Higgs boson decay modes $hrightarrow gammagamma,;WW,;ZZ,; bbar b,;taubartau$, B rare decay $bar Brightarrow X_sgamma$, and the transition magnetic moments of Majorana neutrinos, we analyze the theoretical predictions of the muon anomalous magnetic dipole moment in the $B-L$ supersymmetric model. The numerical analyses indicate that the tension between the experimental measurement and the standard model prediction is remedied in the $B-L$ supersymmetric model.
The statistical significance that characterizes a discrepancy between a measurement and theoretical prediction is usually calculated assuming that the statistical and systematic uncertainties are known. Many types of systematic uncertainties are, however, estimated on the basis of approximate procedures and thus the values of the assigned errors are themselves uncertain. Here the impact of the uncertainty {it on the assigned uncertainty} is investigated in the context of the muon $g-2$ anomaly. The significance of the observed discrepancy between the Standard Model prediction of the muons anomalous magnetic moment and measured values are shown to decrease substantially if the relative uncertainty in the uncertainty assigned to the Standard Model prediction exceeds around 30%. The reduction in sensitivity increases for higher significance, so that establishing a $5sigma$ effect will require not only small uncertainties but the uncertainties themselves must be estimated accurately to correspond to one standard deviation.
After a brief review of the muon g-2 status, we analyze the possibility that the present discrepancy between experiment and the Standard Model (SM) prediction may be due to hypothetical errors in the determination of the hadronic leading-order contribution to the latter. In particular, we show how an increase of the hadro-production cross section in low-energy e^+e^- collisions could bridge the muon g-2 discrepancy, leading however to a decrease on the electroweak upper bound on M_H, the SM Higgs boson mass. That bound is currently M_H < ~ 150GeV (95%CL) based on the preliminary top quark mass M_t = 172.6(1.4)GeV and the recent determination Delta alpha_{rm had}^{(5)}(M_Z) = 0.02768(22), while the direct-search lower bound is M_H > 114.4GeV (95%CL). By means of a detailed analysis we conclude that this solution of the muon g-2 discrepancy is unlikely in view of current experimental error estimates. However, if this turns out to be the solution, the 95%CL upper bound on M_H is reduced to about 130GeV which, in conjunction with the experimental lower bound, leaves a narrow window for the mass of this fundamental particle.
The Fermilab Muon $g-2$ collaboration recently announced the first result of measurement of the muon anomalous magnetic moment ($g-2$), which confirmed the previous result at the Brookhaven National Laboratory and thus the discrepancy with its Standard Model prediction. We revisit low-scale supersymmetric models that are naturally capable to solve the muon $g-2$ anomaly, focusing on two distinct scenarios: chargino-contribution dominated and pure-bino-contribution dominated scenarios. It is shown that the slepton pair-production searches have excluded broad parameter spaces for both two scenarios, but they are not closed yet. For the chargino-dominated scenario, the models with $m_{tilde{mu}_{rm L}}gtrsim m_{tilde{chi}^{pm}_1}$ are still widely allowed. For the bino-dominated scenario, we find that, although slightly non-trivial, the region with low $tan beta$ with heavy higgsinos is preferred. In the case of universal slepton masses, the low mass regions with $m_{tilde{mu}}lesssim 230$ GeV can explain the $g-2$ anomaly while satisfying the LHC constraints. Furthermore, we checked that the stau-bino coannihilation works properly to realize the bino thermal relic dark matter. We also investigate heavy staus case for the bino-dominated scenario, where the parameter region that can explain the muon $g-2$ anomaly is stretched to $m_{tilde{mu}}lesssim 1.3$ TeV.
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