CODATA recommended values of the fundamental physical constants: 2014

Mohr, Peter J.; Newell, David B.; Taylor, Barry N.

doi:10.1103/revmodphys.88.035009

Cited by 959 publications

(993 citation statements)

References 285 publications

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“…While we got a suppression of the NP effects in the B 0 s,d → τ + τ − decays through the large τ mass, (see (4.6) and (4.7)), we get now a huge enhancement thanks to the tiny electron mass [21]: It is particularly interesting to consider the ratio between the B 0 s → e + e − and the B 0 s → µ + µ − branching ratios:…”

Section: New Physics Benchmark Scenariomentioning

confidence: 99%

“…Consequently, the NP correction to C 10 and those proportional to P s µµ and S s µµ are strongly suppressed through the ratio of the muon and tau masses, which is given as follows [21]: In view of the challenges related to the reconstruction of the τ leptons, the NP effects arising in the general flavour-universal NP scenario cannot be distinguished from the SM case, unless there is unexpected experimental progress.…”

Section: New Physics Benchmark Scenariomentioning

confidence: 99%

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In pursuit of new physics with B s,d 0 → ℓ + ℓ −

Fleischer

Tetlalmatzi-Xolocotzi

2017

J. High Energ. Phys.

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Abstract:Leptonic rare decays of B 0 s,d mesons offer a powerful tool to search for physics beyond the Standard Model. The B 0 s → µ + µ − decay has been observed at the Large Hadron Collider and the first measurement of the effective lifetime of this channel was presented, in accordance with the Standard Model. On the other hand, B 0 s → τ + τ − and B 0 s → e + e − have received considerably less attention: while LHCb has recently reported a first upper limit of 6.8 × 10 −3 (95% C.L.) for the B 0 s → τ + τ − branching ratio, the upper bound 2.8 × 10 −7 (90% C.L.) for the branching ratio of B 0 s → e + e − was reported by CDF back in 2009. We discuss the current status of the interpretation of the measurement of B 0 s → µ + µ − , and explore the space for New-Physics effects in the other B 0 s,d → + − decays in a scenario assuming flavour-universal Wilson coefficients of the relevant fourfermion operators. While the New-Physics effects are then strongly suppressed by the ratio m µ /m τ of the lepton masses in B 0 s → τ + τ − , they are hugely enhanced by m µ /m e in B 0 s → e + e − and may result in a B 0 s → e + e − branching ratio as large as about 5 times the one of B 0 s → µ + µ − , which is about a factor of 20 below the CDF bound; a similar feature arises in B 0 d → e + e − . Consequently, it would be most interesting to search for the B 0 s,d → e + e − channels at the LHC and Belle II, which may result in an unambiguous signal for physics beyond the Standard Model.

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Section: New Physics Benchmark Scenariomentioning

confidence: 99%

Section: New Physics Benchmark Scenariomentioning

confidence: 99%

In pursuit of new physics with B s,d 0 → ℓ + ℓ −

Fleischer

Tetlalmatzi-Xolocotzi

2017

J. High Energ. Phys.

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“…The long-standing discrepancy between the standard-model determination and the experimental measurement [1] (updated to the latest muon-proton magnetic moment ratio [2]) a exp µ = 116 592 089(63) × 10 −11 (1.1) of the anomalous magnetic moment of the muon (g − 2) µ has triggered substantial interest in the subject on both the theoretical and the experimental side. The ongoing E989 experiment at Fermilab [3] as well as complementary efforts by J-PARC E34 [4] aim at improving the precision by a factor of 4, see [5] for a detailed account of the experimental strategies in both cases.…”

Section: Introductionmentioning

confidence: 99%

Dispersion relation for hadronic light-by-light scattering: two-pion contributions

Colangelo

Hoferichter

Procura

et al. 2017

J. High Energ. Phys.

385

257

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In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon (g − 2) µ , including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of γ * γ * → ππ. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, a π-box µ = −15.9(2)×10 −11 . As an application of the partial-wave formalism, we present a first calculation of ππ-rescattering effects in HLbL scattering, with γ * γ * → ππ helicity partial waves constructed dispersively using ππ phase shifts derived from the inverse-amplitude method. In this way, the isospin-0 part of our calculation can be interpreted as the contribution of the f 0 (500) to HLbL scattering in (g − 2) µ . We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its S-wave rescattering corrections reads a π-box µ + a ππ,π-pole LHC µ,J=0 = −24(1) × 10 −11 .

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“…Although it has been obtained by extrapolation of numerical results, we aim to calculate it directly, in order to find out the best approach for the analogous two-loop contribution, which currently is the main source of the uncertainty of theoretical predictions. Due to extremely accurate measurements in hydrogenlike carbon [8], the bound electron g factor is presently used for the most accurate determination of the electron mass [9], and in the future it can be used for determination of the fine structure constant [10] and for precision tests of the Standard Model.…”

Section: Introductionmentioning

confidence: 99%