64 research outputs found

### Using $\Lambda_b\to \Lambda\mu^+\mu^-$ data within a Bayesian analysis of $|\Delta B| = |\Delta S| = 1$ decays

We study the impact of including the baryonic decay $\Lambda_b\to \Lambda(\to
p \pi^-)\mu^+\mu^-$ in a Bayesian analysis of $|\Delta B | = |\Delta S| = 1$
transitions. We perform fits of the Wilson coefficients $C_{9}$, $C_{9'}$,
$C_{10}$ and $C_{10'}$, in addition to the relevant nuisance parameters. Our
analysis combines data for the differential branching fraction and three
angular observables of $\Lambda_b\to \Lambda(\to p \pi^-)\mu^+\mu^-$ with data
for the branching ratios of $B_s \to \mu^+\mu^-$ and inclusive $b \to
s\ell^+\ell^-$ decays. Newly available precise lattice QCD results for the full
set of $\Lambda_b \to \Lambda$ form factors are used to evaluate the
observables of the baryonic decay. Our fits prefer shifts to $C_{9}$ that are
opposite in sign compared to those found in global fits of only mesonic decays,
and the posterior odds show no evidence of physics beyond the Standard Model.
We investigate a possible hadronic origin of the observed tensions between
theory and experiment.Comment: 9 pages, 2 figures; v2 as published: added some clarifications,
changed setup for model comparisons, expanded conclusion

### Zero-Recoil Sum Rules for $\Lambda_b \to \Lambda_c$ Form Factors

We set up a zero recoil sum rule to constrain the form factors of the
$\Lambda_b \to \Lambda_c$ transition. Our results are compared with the recent
lattice calculation for these transitions. We find the same situation as in the
case for $B \to D^*$: The lattice results practically saturate the sum rules,
leaving basically no room for excited states.Comment: 8 pages, 5 figure

### Impact of leptonic $\tau$ decays on the distribution of $B \to P \mu\bar\nu$ decays

We calculate the fully-differential rate of the decays $B\to P\tau(\to
\mu\bar\nu\nu)\bar\nu$ where $P = D,\pi$, which is a background to the
semimuonic decays $B\to P\mu\bar\nu$. The decays with a $3\nu$ final state can
have a sizeable impact on the experimental analyses of the ratios $R_D$ and
$R_\pi$, depending on the event selection in the analysis. We outline a
strategy which permits the extraction of $R_P \mathcal{B}(\tau \to
\mu\bar\nu\nu)$ 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
$B\to P\mu X_{\bar\nu}$.Comment: 14 pages, 6 figures, 3 ancillary files; v2 (as published): Corrected
error in d^5Gamma, updated all numerical results; summary unchange

### Extracting Angular Observables without a Likelihood and Applications to Rare Decays

Our goal is to obtain a complete set of angular observables arising in a
generic multi-body process. We show how this can be achieved without the need
to carry out a likelihood fit of the angular distribution to the measured
events. Instead, we apply the method of moments that relies both on the
orthogonality of angular functions and the estimation of integrals by Monte
Carlo techniques. The big advantage of this method is that the joint
distribution of all observables can be easily extracted, even for very few
events. The method of moments is shown to be robust against mismodeling of the
angular distribution. Our main result is an explicit algorithm that accounts
for systematic uncertainties from detector-resolution and acceptance effects.
Finally, we present the necessary process-dependent formulae needed for direct
application of the method to several rare decays of interest.Comment: 13 pages, 4 figure

### Long-distance effects in $B\to K^*\ell\ell$ from Analyticity

We discuss a novel approach to systematically determine the long-distance
contribution to $B\to K^*\ell\ell$ decays in the kinematic region where the
dilepton invariant mass is below the open charm threshold. This approach
provides the most consistent and reliable determination to date and can be used
to compute Standard Model predictions for all observables of interest,
including the kinematic region where the dilepton invariant mass lies between
the $J/\psi$ and the $\psi(2S)$ resonances. We illustrate the power of our
results by performing a New Physics fit to the Wilson coefficient $C_9$. This
approach is systematically improvable from theoretical and experimental sides,
and applies to other decay modes of the type $B\to V\ell\ell$, $B\to P\ell\ell$
and $B\to V\gamma$.Comment: 10 pages, 5 figure

### $1/m$ Corrections for Orbitally Excited Heavy Mesons and the $1/2$ - $3/2$ Puzzle

We re-investigate the effects of the $1/m_c$ corrections on the spectrum of
the lowest orbitally excited $D$-meson states. We argue that one should expect
the $1/m_c$ corrections to induce a significant mixing between the two lowest
lying $1^+$ states. We discuss the implications of this mixing and compute its
effect on the semileptonic decays $B \to D^{**} \ell \bar{\nu}$ and the strong
$D^{**}$ decays.Comment: 9 pages, 3 figure

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