56 research outputs found
Semi-leptonic -physics anomalies: a general EFT analysis within flavor symmetry
We analyse the recent hints of Lepton Flavor Universality violations in
semi-leptonic decays within a general EFT based on a flavor
symmetry acting on the light generations of SM fermions. We analyse in
particular the consistency of these anomalies with the tight constraints on
various low-energy observables in and physics. We show that, with a
moderate fine-tuning, a consistent picture for all low-energy observables can
be obtained under the additional dynamical assumption that the NP sector is
coupled preferentially to third generation SM fermions. We discuss how this
dynamical assumption can be implemented in general terms within the EFT, and we
identify a series of observables in decays which could provide further
evidences of this NP framework.Comment: 25 pages, late
Impact of leptonic decays on the distribution of decays
We calculate the fully-differential rate of the decays where , which is a background to the
semimuonic decays . The decays with a final state can
have a sizeable impact on the experimental analyses of the ratios and
, depending on the event selection in the analysis. We outline a
strategy which permits the extraction of from the neutrino-inclusive rate. Our analytic results can also
be used to test both existing and upcoming experimental analyses. We further
provide Monte Carlo samples of the 5D rate of the neutrino-inclusive decays
.Comment: 14 pages, 6 figures, 3 ancillary files; v2 (as published): Corrected
error in d^5Gamma, updated all numerical results; summary unchange
Probing Lepton Flavour Universality with decays
We analyse the rare processes in view of the recent
hints of violations of Lepton Flavour Universality (LFU) observed in B meson
decays. If, as suggested by present data, the new interactions responsible for
LFU violations couple mainly to the third generation of left-handed fermions,
decays turn out to be particularly interesting: these are
the only kaon decays with third-generation leptons (the neutrinos) in
the final state. In order to relate B-physics anomalies and K decays we adopt
an Effective Field Theory approach, assuming that the new interactions satisfy
an approximate flavour symmetry. In this framework we
show that O(1) deviations from the Standard Model predictions in branching ratios, closely correlated to similar effects in , are naturally expected. The correlation of
, , and
the LFU violations in B decays would provide a very valuable tool to shed more
light on this interesting phenomenon.Comment: 11 pages, 2 figure
Minimal muon anomalous magnetic moment
We classify all possible one-particle (scalar and fermion) extensions of the
Standard Model that can contribute to the anomalous magnetic moment of leptons.
We review the cases already discussed in the literature and complete the
picture by performing the calculation for a fermionic doublet with hypercharge
-3/2. We conclude that, out of the listed possibilities, only two scalar
leptoquarks and the pseudoscalar of a peculiar two-Higgs-doublet model could be
the responsibles for the muon anomalous magnetic moment discrepancy. Were this
the case, this particles could be seen in the next LHC run. To this aim,
especially to test the leptoquark hypothesis, we suggest to look for final
states with tops and muons.Comment: 15 pages, uses axodra
Massive vectors and loop observables: the case
We discuss the use of massive vectors for the interpretation of some recent
experimental anomalies, with special attention to the muon . We restrict
our discussion to the case where the massive vector is embedded into a
spontaneously broken gauge symmetry, so that the predictions are not affected
by the choice of an arbitrary energy cut-off. Extended gauge symmetries,
however, typically impose strong constraints on the mass of the new vector
boson and for the muon they basically rule out, barring the case of
abelian gauge extensions, the explanation of the discrepancy in terms of a
single vector extension of the standard model. We finally comment on the use of
massive vectors for -meson decay and di-photon anomalies.Comment: 25 pages, 1 figure. References added, to appear in JHE
A three-site gauge model for flavor hierarchies and flavor anomalies
We present a three-site Pati-Salam gauge model able to explain the Standard
Model flavor hierarchies while, at the same time, accommodating the recent
experimental hints of lepton-flavor non-universality in decays. The model
is consistent with low- and high-energy bounds, and predicts a rich spectrum of
new states at TeV scale that could be probed in the near future by the
high- experiments at the LHC.Comment: 8 pages, 2 figures. v2: Added section II.B, matching the PLB versio
and confront new physics in
Several new physics scenarios that address anomalies in -physics predict
an enhancement of with respect to its Standard
Model prediction. Such scenarios necessarily imply modifications of the
lifetime ratio and the lifetime difference
. In this work, we explore indirect bounds provided by these
observables over new physics scenarios. We also estimate future projections,
showing that future experimental and theoretical improvements on both
and have the potential to
provide bounds competitive with those directly extracted from transitions. After performing a model-independent analysis, we apply
our results to the particular case of leptoquark mediators proposed to address
the anomalies.Comment: 12 pages + Appendix, 4 Figure
Exploiting dijet resonance searches for flavor physics
In this work, we reinterpret ATLAS and CMS dijet resonance searches to set
robust constraints on all hypothetical tree-level scalar and vector mediators
with masses up to 5 TeV, assuming a diquark or a quark-antiquark coupling with
an arbitrary flavor composition. To illustrate the application of these general
results, we quantify the permissible size of new physics in consistent with the absence of signal in dijet
resonance searches. Along the way, we perform a full SMEFT analysis of the
aforementioned non-leptonic meson decays at leading-order in .
Our findings uncover a pressing tension between the new physics explanations of
recently reported anomalies in these decays and the dijet resonant searches.
The high- constraints are crucial to drain the parameter space consistent
with the low- flavor physics data.Comment: 42 pages, 9 figures, 3 tables. v2: Version accepted in JHE
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