Robuste Parameterschätzung für reale Anwendungen

Altmannshofer, Simon; Endisch, Christian

doi:10.1007/978-3-662-55327-5_12

Cited by 2 publications

(3 citation statements)

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“…As the FCCC b → c − ν transition occurs at tree level in the SM, NP explanations also occur typically at tree level. Various models with single mediators have been proposed, with heavy charged vector bosons (W ) [179][180][181][182], heavy charged scalars (H ) [183][184][185][186][187][188][189][190], or coloured vector or scalar bosons (leptoquarks) [145,176,177,[191][192][193][194][195][196][197][198][199][200][201][202][203][204]. A last possibility allowed by the quantum numbers of the fermions involved consists in vector-like quarks that mix with chiral SM quarks and change the couplings to the W boson (including right-handed couplings), but unless light right-handed neutrinos are introduced, they do not affect the couplings to the leptons and thus yield LU contributions which are not of interest here.…”

Section: B → C − νmentioning

confidence: 99%

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Review of lepton universality tests in B decays

Bifani

Descotes-Genon

Vidal

et al. 2018

J. Phys. G: Nucl. Part. Phys.

189

188

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Several measurements of tree-and loop-level b-hadron decays performed in the recent years hint at a possible violation of Lepton Universality. This article presents an experimental and theoretical overview of the current status of the field. References 47ii t bDespite its tremendous success in describing all present measurements, the SM can only be regarded as the low-energy, effective, incarnation of a more global theory. For example, the SM cannot account for the matter-antimatter asymmetry currently present in the Universe, it does not provide a Dark Matter candidate and it does not explain its own gauge group structure, the charge assignment of the fermions or the mass hierarchy between the different families. A more global theory that extends the SM at higher energies and shorter distances could provide an answer to some of these questions, which are at the core of modern particle physics.Searches for signs of New Physics (NP) existing beyond the SM are performed in two ways. The first one looks for the direct production of new particles. The key ingredient for this so-called "relativistic path" is the amount of energy available in the collision, which drives the maximum mass range that can be probed. For this reason, the vast majority of the most stringent limits on the mass of NP particles have been obtained at the Large Hadron Collider (LHC) by the ATLAS and CMS experiments, as shown for example in Ref. [1]. The second method, the so-called "quantum path", exploits the presence of virtual states in the decays of SM particles. Due to quantum mechanics, these intermediate states can be much heavier than the initial and final particles, and can affect the rate of specific decay modes as well as their angular distributions. The most evident example is the β decay of the neutron that probes physics at the W -boson scale. Flavour physics, which studies the properties of s-, c-and b-hadrons, has been extremely successful in providing information on the virtual particles involved in the processes examined. A famous example is the observation of CP violation in K decays [2] that could be interpreted as a sign of the existence of three quark families in the SM [3], several years before the discovery of the third generation [4,5]. Similarly, the first observation of the B 0 -B 0 mixing phenomenon [6] revealed that the t-quark mass was much larger than anticipated, eight years before its direct measurement [7,8]. The investigation of the effects induced by virtual particles on SM decays requires very large data samples, since (for a given coupling to NP) the larger the NP scale, the smaller the influence on the process. While the relativistic path probes the scale of potential NP contributions in a direct way through specific signatures, the quantum path provides constraints correlating the scale and the coupling to NP.In the SM, the leptonic parts of the three families of fermions are identical, except for the different masses of the constituent particles. In particular, the photon, the W and the Z bosons couple in ...

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Section: B → C − νmentioning

confidence: 99%

“…The extension of this discussion to more general frameworks is possible and leaves room for other types of models. For instance, one may consider supersymmetric models allowing for couplings violating R-parity [204].…”

Section: B → C − νmentioning

confidence: 99%

Review of lepton universality tests in B decays

Bifani

Descotes-Genon

Vidal

et al. 2018

J. Phys. G: Nucl. Part. Phys.

189

188

View full text Add to dashboard Cite

show abstract

“…During these low excitation periods, few valuable information for the parameter estimation is introduced while old information is forgotten. This originates the so-called covariance ''wind-up'', which makes the parameter estimation highly sensitive to sensor noise and numerical errors, and therefore utterly unreliable (Altmannshofer & Endisch, 2017;Cao & Schwartz, 2000). In this context, a criterion to limit the growth of the parameter covariance 𝑺 𝑘 is employed (Rao Sripada & Grant Fisher, 1987).…”

Section: 𝑷 −mentioning

confidence: 99%