Upgraded breaking of the HLS model: a full solution to the τ−e + e − and ϕ decay issues and its consequences on g−2 VMD estimates

Abstract

The muon anomalous magnetic moment a μ and the hadronic vacuum polarization are examined using data analyzed within the framework of a suitably broken HLS model. The analysis relies on all available scan data samples and leaves provisionally aside the existing ISR data. Our HLS model based global fit approach allows for a better check of consistency between data sets and we investigate how results depend on different strategies which may be followed. Relying on global fit qualities, we find several acceptable solutions leading to ambiguities in the reconstructed value for (a μ ) th . Among these, the most conservative solution is a had,LO μ [HLS improved] = 687.72(4.63) × 10 −10 and (a μ ) th = 11 659 175.37(5.31) × 10 −10 corresponding to a 4.1σ significance for the difference a μ = (a μ ) exp − (a μ ) th . It is also shown that the various contributions accessible through the model yield uniformly a factor 2 improvement of their uncertainty. The breaking procedure implemented in the HLS model is an extension of the former procedure based on a mechanism defined by Bando, Kugo and Yamawaki (BKY). This yields a quite satisfactory simultaneous description of most e + e − annihilation channels up to and including the φ meson (and of a set of 10 (mostly radiative) decay widths of light mesons. It also allows to achieve the proof of consistency between the e + e − → π + π − annihilation and the τ ± → π ± π 0 ν decay and gives a solution to the reported problem concerning the measured partial width ratio Γ (φ → K + K − )/Γ (φ → K 0 K 0 ). Prospects for improving the VMD based estimates of a μ are emphasized. a

An update of the HLS estimate of the muon g−2

“…Using a symmetry breaking mechanism based on the simple BKY idea [16] and a vector meson mixing scheme, the model has been developed stepwise [17][18][19][20] and its most recent form [13] has been shown to provide a successful simultaneous description of the e + e − annihilation into the π + π − , π 0 γ , ηγ , π + π − π 0 , K + K − , K 0 K 0 final states as well as the τ ± → ν τ π ± π 0 decay spectrum. Some more decays of the form 2 V → P γ or P → γ γ are considered.…”

“…Up to now, the broken HLS model (BHLS) [13]basically an empty shell-has been fed with all existing data sets 4 for what concerns the annihilation channels π 0 γ , ηγ , π + π − π 0 , K + K − , K 0 K 0 , with the spectra from ALEPH [21], CLEO [22] and BELLE [23] for the τ dipion decay 5 and with the V P γ /P γ γ partial width information extracted from the Review of Particle Properties (RPP) [24]. This already represents more than 40 data sets collected by different groups with different detectors; one may thus consider that the systematics affecting these data sets wash out to a large extent within a global fit framework.…”

Flavour dependent gauged radiative neutrino mass model

“…It has been known that there is a discrepancy from the SM prediction by 3.2σ [92] to 4.1σ [93]: In our model, the dominant contribution to the muon g −2 is obtained through the one loop diagram where the muon and the extra neutral gauge boson Z ′ of the U(1) µ−τ symmetry are running in the loop. The resulting form is given by…”

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

“…Several groups, however, have reported an anomaly of the muon anomalous magnetic moment a µ = (g − 2)/2 (muon g-2), which has been precisely measured experimentally [3] and compared with state-of-the-art theoretical predictions (for example, see [4][5][6][7][8][9][10][11] and references therein). The estimated discrepancies between the SM predictions and the measured value are consistently more than 3σ, as listed in table 1.…”

“…Following this line, in [6] 31.6 ± 7.9 (4.0σ) [7] 11659208.9 ± 6. 3 33.5 ± 8.2 (4.1σ) [8] 28.3 ± 8.7 (3.3σ) [9] 29.0 ± 9.0 (3.2σ) [10] 28.7 ± 8.0 (3.6σ) [11] Table 1. Measured muon g-2 (a Exp µ ) and the estimated differences (δa µ ) from the recent SM predictions in several references.…”