The flavour anomalies are a set of experimental deviations from the Standard Model (SM) predictions in several observables involving decays of bottom quarks. In particular, tensions between theory ...and experiment in measurements involving a bottom quark decaying into a strange quark and a pair of muons have motivated much theoretical work to explore possible new physics explanations. This review summarises the tumultuous evolution of these tensions, focusing on the most recent experimental results and their implications for physics beyond the SM. We also discuss the prospects for future measurements and tests of the flavour anomalies at the LHC and other facilities.
A
bstract
In this paper we present a detailed study of the four-body decay
B
0
→
K
+
π
−
ℓ
+
ℓ
−
, where tensions with the Standard Model predictions have been observed. Our analysis of the decay ...with P- and S-wave contributions to the
K
+
π
−
system develops a complete understanding of the symmetries of the distribution, in the case of massless and massive leptons. In both cases, the symmetries determine relations between the observables in the
B
0
→
K
+
π
−
ℓ
+
ℓ
−
decay distribution. This enables us to define the complete set of observables accessible to experiments, including several that have not previously been identified. The new observables arise when the decay rate is written differentially with respect to
m
K
π
. We demonstrate that experiments will be able to fit this full decay distribution with currently available data sets and investigate the sensitivity to new physics scenarios given the experimental precision that is expected in the future.
The symmetry relations provide a unique handle to explore the behaviour of S-wave observables by expressing them in terms of P-wave observables, therefore minimising the dependence on poorly-known S-wave form factors. Using this approach, we construct two theoretically optimized S-wave observables and explore their sensitivity to new physics. By further exploiting the symmetry relations, we obtain the first bounds on the S-wave observables using two different methods and highlight how these relations may be used as cross-checks of the experimental methodology and the parametrization of the
B
0
→
K
+
π
−
ℓ
+
ℓ
−
differential decay rate. We identify a zero-crossing point that would be at a common dilepton invariant mass for a subset of P- and S-wave observables, and explore the information on new physics and hadronic effects that this zero point can provide.
Abstract In this paper we present a detailed study of the four-body decay B 0 → K + π − ℓ + ℓ − , where tensions with the Standard Model predictions have been observed. Our analysis of the decay with ...P- and S-wave contributions to the K + π − system develops a complete understanding of the symmetries of the distribution, in the case of massless and massive leptons. In both cases, the symmetries determine relations between the observables in the B 0 → K + π − ℓ + ℓ − decay distribution. This enables us to define the complete set of observables accessible to experiments, including several that have not previously been identified. The new observables arise when the decay rate is written differentially with respect to m K π $$ {m}_{K_{\pi }} $$ . We demonstrate that experiments will be able to fit this full decay distribution with currently available data sets and investigate the sensitivity to new physics scenarios given the experimental precision that is expected in the future. The symmetry relations provide a unique handle to explore the behaviour of S-wave observables by expressing them in terms of P-wave observables, therefore minimising the dependence on poorly-known S-wave form factors. Using this approach, we construct two theoretically optimized S-wave observables and explore their sensitivity to new physics. By further exploiting the symmetry relations, we obtain the first bounds on the S-wave observables using two different methods and highlight how these relations may be used as cross-checks of the experimental methodology and the parametrization of the B 0 → K + π − ℓ + ℓ − differential decay rate. We identify a zero-crossing point that would be at a common dilepton invariant mass for a subset of P- and S-wave observables, and explore the information on new physics and hadronic effects that this zero point can provide.
We present the results of searches for the Standard Model Higgs boson decaying predominantly to W+W− pairs, at a center-of-mass energy of √s = 1.96 TeV, using up to 8.2 fb−1 of data collected with ...the CDF and D0 detectors at the Fermilab Tevatron collider. The analysis techniques and the various channels considered are discussed. These searches result in exclusions across the Higgs mass range of 156.5< mH <173.7 GeV for CDF and 161< mH <170 GeV for D0.
Phys. Rev. D 109, 116013 (2024) We present a method that maximises the experimental sensitivity to new
physics contributions in $B^\pm\to\pi^\pm\mu^+\mu^-$ decays. This method relies
on performing an ...unbinned maximum likelihood fit to both the measured dimuon
$q^2$ distribution of $B^\pm\to\pi^\pm\mu^+\mu^-$ decays, and theory
calculations at spacelike $q^2$, where QCD predictions are most reliable. We
exploit the known analytic properties of the decay amplitude and employ a
dispersion relation to describe the non-local hadronic contributions across
spacelike and timelike $q^2$ regions. The fit stability and the sensitivity to
new physics couplings and new sources of $CP$-violation are studied for current
and future data-taking scenarios, with the LHCb experiment as an example. The
proposed method offers a precise and reliable way to search for new physics in
these decays.
We present a method that maximises the experimental sensitivity to new physics contributions in \(B^\pm\to\pi^\pm\mu^+\mu^-\) decays. This method relies on performing an unbinned maximum likelihood ...fit to both the measured dimuon \(q^2\) distribution of \(B^\pm\to\pi^\pm\mu^+\mu^-\) decays, and theory calculations at spacelike \(q^2\), where QCD predictions are most reliable. We exploit the known analytic properties of the decay amplitude and employ a dispersion relation to describe the non-local hadronic contributions across spacelike and timelike \(q^2\) regions. The fit stability and the sensitivity to new physics couplings and new sources of \(CP\)-violation are studied for current and future data-taking scenarios, with the LHCb experiment as an example. The proposed method offers a precise and reliable way to search for new physics in these decays.
JHEP 12 (2021) 085 In this paper we present a detailed study of the four-body decay $B^0\to
K^{+}\pi^{-}\ell^{+}\ell^{-}$, where tensions with the Standard Model
predictions have been observed. Our ...analysis of the decay with P- and S-wave
contributions to the $K^{+}\pi^{-}$ system develops a complete understanding of
the symmetries of the distribution, in the case of massless and massive
leptons. In both cases, the symmetries determine relations between the
observables in the $B^0\to K^{+}\pi^{-}\ell^{+}\ell^{-}$ decay distribution.
This enables us to define the complete set of observables accessible to
experiments, including several that have not previously been identified. The
new observables arise when the decay rate is written differentially with
respect to $m_{K\pi}$. We demonstrate that experiments will be able to fit this
full decay distribution with currently available data sets and investigate the
sensitivity to new physics scenarios given the experimental precision that is
expected in the future. The symmetry relations provide a unique handle to
explore the behaviour of S-wave observables by expressing them in terms of
P-wave observables, therefore minimising the dependence on poorly-known S-wave
form factors. Using this approach, we construct two theoretically clean S-wave
observables and explore their sensitivity to new physics. By further exploiting
the symmetry relations, we obtain the first bounds on the S-wave observables
using two different methods and highlight how these relations may be used as
cross-checks of the experimental methodology. We identify a zero-crossing point
that would be at a common dilepton invariant mass for a subset of P- and S-wave
observables, and explore the information on new physics and hadronic effects
that this zero point can provide.
We present the results of searches for the Standard Model Higgs boson decaying predominantly to WW pairs, at a center-of-mass energy of sqrt(s)=1.96 TeV, using up to 8.2 fb^{-1} of data collected ...with the CDF and D0 detectors at the Fermilab Tevatron collider. The analysis techniques and the various channels considered are discussed. These searches result in exclusions across the Higgs mass range of 156.5<mH<173.7 GeV for CDF and 161<mH<170 GeV for D0.
JHEP 06 (2015) 084 A method for determining the $q^2$ dependent $\bar{K}^{*0}$ spin amplitudes
of $\bar{B}^{0}\to \bar{K}^{*0}\mu^+\mu^-$ decays through a maximum likelihood
fit to data is presented. ...While current experimental techniques extract a
limited set of observables in bins of $q^2$, our approach allows for the
determination of all observable quantities as continuous distributions in
$q^2$. By doing this, the method eliminates the need to correct theory
predictions of these observables for $q^2$ averaging effects, thus increasing
the sensitivity to the effects of physics beyond the Standard Model. Accounting
for the symmetries of the angular distribution and using a three parameter
ansatz for the $q^2$ dependence of the amplitudes, the precision of the angular
observables and the sensitivity to new physics is estimated using simulated
events. These studies are based on the sample sizes collected by the LHCb
experiment during Run-I and expected for Run-II.
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