The MSSM confronts the precision electroweak data and the muon g − 2

In light of the discovery of a Higgs-like particle at the LHC, we revisit the status of the precision electroweak data, focusing on two discrepant observables: 1) the long-standing 2.4σ deviation in the forward-backward asymmetry of the bottom quark A b F B , and 2) the 2.3σ deviation in R b , the ratio of the Z → bb partial width to the inclusive hadronic width, which is now in tension after a recent calculation including new two-loop electroweak corrections. We consider possible resolutions of these discrepancies. Taking the data at face value, the most compelling scenario is that new physics directly affects A b F B and R b , bringing the prediction into accord with the measured values. We propose a modified 'Beautiful Mirrors' scenario which contains new vector-like quarks that mix with the b quark, modifying the Zbb vertex and thus correcting A b F B and R b . We show that this scenario can lead to modifications to the production rates of the Higgs boson in certain channels, and in particular a sizable enhancement in the diphoton channel. We also describe additional collider tests of this scenario.The ATLAS and CMS experiments have recently discovered a new boson with properties closely resembling those of the Standard Model (SM) Higgs boson [1,2]. The focus of the experimental collaborations now turns to determining the properties of this state, such as its quantum numbers and its couplings to other SM particles. This is an extremely important task since any deviation from the SM Higgs boson predictions will unambiguously point to new physics (NP) at the TeV scale. In this respect it is intriguing that both experiments observe a slight enhancement in the h → γγ channel, though with the current dataset this enhancement is not statistically significant [3, 4].If, as the current data suggest, this new state is indeed the Higgs boson, its mass m h ∼ 125 GeV will be in accord with the expectation indirectly suggested by the precision electroweak data, which favors a light SMlike Higgs boson. Of the many precision measurements used to test the electroweak sector, most of them are in good agreement with the SM predictions, see for example [5],[6], [7]. However, there are a couple of notable discrepancies. The forward-backward asymmetry of the bottom quark A b F B measured at the Z-pole at LEP1 constitutes a long-standing exception. The measured value and SM prediction are [5], [7],and thus exhibit a 2.4σ discrepancy. Furthermore, a recent calculation of R b , the ratio of the Z → bb partial width to the inclusive hadronic width, which includes new two-loop electroweak corrections, now puts the prediction in tension with the measured value [8]. The measurement and prediction read [5], [7],displaying a 2.3σ discrepancy.It is a matter of debate whether these deviations call for NP. Among a large ensemble of measurements, such as that used in the electroweak fit, one may expect an occasional discrepancy of this size, which could be the result of a statistical fluctuation or unknown systematic error. However, a possib...

“…We employ the numerical parameterizations of the Z boson partial widths in terms of the SM parameters (6) from Ref. [29] (updated from earlier work in Refs. [30]).…”

Section: Interpreting the Precision Electroweak Datamentioning

confidence: 99%

Higgs couplings and precision electroweak data

Batell

Gori

Wang

2013

“…We adopt formulas in, for example, refs. [39][40][41] for the calculation. We perform a χ 2 fit by varying input parameters m t , m h , ∆α (5) had and α s , in order to identify the parameter region consistent with the data.…”

Section: Muon G-2 and Electroweak Precision Observablesmentioning

confidence: 99%

Muon g-2 and LHC phenomenology in the L μ − L τ gauge symmetric model

Harigaya

Igari

Nojiri

et al. 2014

In this paper, we consider phenomenology of a model with an L µ − L τ gauge symmetry. Since the muon couples to the L µ − L τ gauge boson (called Z boson), its contribution to the muon anomalous magnetic moment (muon g-2) can account for the discrepancy between the standard model prediction and the experimental measurements. On the other hand, the Z boson does not interact with the electron and quarks, and hence there are no strong constraints from collider experiments even if the Z boson mass is of the order of the electroweak scale. We show an allowed region of a parameter space in the L µ − L τ symmetric model, taking into account consistency with the electroweak precision measurements as well as the muon g-2. We study the Large Hadron Collider (LHC) phenomenology, and show that the current and future data would probe the interesting parameter space for this model.

“…The current status of the MSSM prediction for a µ is as follows: the MSSM one-loop contributions to a µ have been computed and extensively documented in refs. [27,[45][46][47]. The twoloop corrections have been classified in ref.…”

Section: Current Status and Motivationmentioning

confidence: 99%

Two-loop corrections to the muon magnetic moment from fermion/sfermion loops in the MSSM: detailed results

Fargnoli

Gnendiger

Paßehr

et al. 2014

Recently, first results were presented for two-loop corrections to the muon (g − 2) from fermion/sfermion loops in the MSSM. These corrections were shown to be generally large and even logarithmically enhanced for heavy sfermions. Here, full details of the calculation and analytical results are presented. Also, a very compact formula is provided which can be easily implemented and serves as a good approximation of the full result as a function of the fourteen most important input parameters. Finally, a thorough discussion of the numerical behaviour of the fermion/sfermion-loop corrections to (g − 2) µ is given. The discussion includes the case of very heavy SUSY masses as well as experimentally allowed scenarios with very light SUSY masses.