This report details the capabilities of LHCb and its upgrades towards the study of kaons and hyperons. The analyses performed so far are reviewed, elaborating on the prospects for some key decay ...channels, while proposing some new measurements in LHCb to expand its strangeness research program.
This paper reports world averages of measurements of \(b\)-hadron, \(c\)-hadron, and \(\tau\)-lepton properties obtained by the Heavy Flavour Averaging Group using results available before April ...2021. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, parameters of semileptonic decays, and Cabibbo-Kobayashi-Maskawa matrix elements.
We perform a likelihood analysis of the constraints from accelerator experiments and astrophysical observations on supersymmetric (SUSY) models with SU(5) boundary conditions on soft SUSY-breaking ...parameters at the GUT scale. The parameter space of the models studied has 7 parameters: a universal gaugino mass \(m_{1/2}\), distinct masses for the scalar partners of matter fermions in five- and ten-dimensional representations of SU(5), \(m_5\) and \(m_{10}\), and for the \(\mathbf{5}\) and \(\mathbf{\bar 5}\) Higgs representations \(m_{H_u}\) and \(m_{H_d}\), a universal trilinear soft SUSY-breaking parameter \(A_0\), and the ratio of Higgs vevs \(\tan \beta\). In addition to previous constraints from direct sparticle searches, low-energy and flavour observables, we incorporate constraints based on preliminary results from 13 TeV LHC searches for jets + MET events and long-lived particles, as well as the latest PandaX-II and LUX searches for direct Dark Matter detection. In addition to previously-identified mechanisms for bringing the supersymmetric relic density into the range allowed by cosmology, we identify a novel \({\tilde u_R}/{\tilde c_R} - \tilde{\chi}^0_1\) coannihilation mechanism that appears in the supersymmetric SU(5) GUT model and discuss the role of \({\tilde \nu_\tau}\) coannihilation. We find complementarity between the prospects for direct Dark Matter detection and SUSY searches at the LHC.
We perform a likelihood analysis of the minimal Anomaly-Mediated Supersymmetry Breaking (mAMSB) model using constraints from cosmology and accelerator experiments. We find that a wino-like or a ...Higgsino-like neutralino LSP, \(m_{\tilde \chi^0_{1}}\), may provide the cold dark matter (DM) with similar likelihood. The upper limit on the DM density from Planck and other experiments enforces \(m_{\tilde \chi^0_{1}} \lesssim 3~TeV\) after the inclusion of Sommerfeld enhancement in its annihilations. If most of the cold DM density is provided by the \(\tilde \chi_0^1\), the measured value of the Higgs mass favours a limited range of \(\tan \beta \sim 5\) (or for \(\mu > 0\), \(\tan \beta \sim 45\)) but the scalar mass \(m_0\) is poorly constrained. In the wino-LSP case, \(m_{3/2}\) is constrained to about \(900~TeV\) and \({m_{\tilde \chi^0_{1}}}\) to \(2.9\pm0.1~TeV\), whereas in the Higgsino-LSP case \(m_{3/2}\) has just a lower limit \(\gtrsim 650TeV\) (\(\gtrsim 480TeV\)) and \(m_{\tilde \chi^0_{1}}\) is constrained to \(1.12 ~(1.13) \pm0.02~TeV\) in the \(\mu>0\) (\(\mu<0\)) scenario. In neither case can the anomalous magnetic moment of the muon, \({(g-2)_\mu}\), be improved significantly relative to its Standard Model (SM) value, nor do flavour measurements constrain the model significantly, and there are poor prospects for discovering supersymmetric particles at the LHC, {though there} are some prospects for direct DM detection. On the other hand, if the \({m_{\tilde \chi^0_{1}}}\) contributes only a fraction of the cold DM density, {future LHC \(E_T\)-based searches for gluinos, squarks and heavier chargino and neutralino states as well as disappearing track searches in the wino-like LSP region will be relevant}, and interference effects enable \({\rm BR}(B_{s, d} \to \mu^+\mu^-)\) to agree with the data better than in the SM in the case of wino-like DM with \(\mu > 0\).
We report on a search for heavy neutrinos in B-meson decays. The results are obtained using a data sample that contains 772x10^6 BB-bar pairs collected at the Upsilon(4S) resonance with the Belle ...detector at the KEKB asymmetric-energy e+e- collider. No signal is observed and upper limits are set on mixing of heavy neutrinos with left-handed neutrinos of the Standard Model in the mass range 0.5 - 5.0 GeV/c^2.
Phys. Rev. D 95, 011102 (2017) We report the result from the first search for $D^0$ decays to invisible
final states. The analysis is performed on a data sample of 924 $\rm{fb}^{-1}$
collected at and ...near the $\Upsilon(4S)$ and $\Upsilon(5S)$ resonances with the
Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. The
absolute branching fraction is determined using an inclusive $D^0$ sample,
obtained by fully reconstructing the rest of the particle system including the
other charmed particle. No significant signal yield is observed and an upper
limit of $9.4\times 10^{-5}$ is set on the branching fraction of $D^0$ to
invisible final states at 90\% confidence level.
Phys. Rev. D 94, 092006 (2016) We report a search for a dark vector gauge boson $U^\prime$ that couples to
quarks in the decay chain $D^{*+} \to D^0 \pi^+, D^0 \to K^0_S \eta, \eta \to
U^\prime ...\gamma$, $U^\prime \to \pi^+ \pi^-$. No signal is found and we set a
mass-dependent limit on the baryonic fine structure constant of $10^{-3} -
10^{-2}$ in the $U^\prime$ mass range of 290 to 520 MeV/$c^2$. This analysis is
based on a data sample of 976 fb$^{-1}$ collected by the Belle experiment at
the KEKB asymmetric-energy $e^+e^-$ collider.
Phys. Rev. D 94, 072007 (2016) We report a measurement of the ratio ${\cal R}(D^*) = {\cal B}(\bar{B}^0
\rightarrow D^{*+} \tau^- \bar{\nu}_{\tau})/{\cal B}(\bar{B}^0 \rightarrow
D^{*+} \ell^- ...\bar{\nu}_{\ell})$, where $\ell$ denotes an electron or a muon.
The results are based on a data sample containing $772\times10^6$ $B\bar{B}$
pairs recorded at the $\Upsilon(4S)$ resonance with the Belle detector at the
KEKB $e^+ e^-$ collider. We select a sample of $B^0 \bar{B}^0$ pairs by
reconstructing both $B$ mesons in semileptonic decays to $D^{*\mp} \ell^{\pm}$.
We measure ${\cal R}(D^*)= 0.302 \pm 0.030({\rm stat)} \pm 0.011({\rm syst)}$,
which is within $1.6 \sigma$ of the Standard Model theoretical expectation,
where the standard deviation $\sigma$ includes systematic uncertainties. We use
this measurement to constrain several scenarios of new physics in a
model-independent approach.
Phys. Rev. D 94, 052004 (2016) We report a measurement of the CP violation parameter $\varphi_1$ obtained in
a time-dependent analysis of $B^0\to\bar{D}{}^{(*)0}h^0$ decays followed by
...$\bar{D}{}^0\to K_S^0\pi^+\pi^-$ decay. A model-independent measurement is
performed using the binned Dalitz plot technique. The measured value is
$\varphi_1 = 11.7^{\circ}\pm7.8^{\circ}({\rm stat.})\pm 2.1^{\circ}({\rm
syst.})$. Treating $\sin{2\varphi_1}$ and $\cos{2\varphi_1}$ as independent
parameters, we obtain $\sin{2\varphi_1} = 0.43\pm 0.27({\rm stat.})\pm
0.08({\rm syst.})$ and $\cos{2\varphi_1} = 1.06\pm 0.33({\rm
stat.})^{+0.21}_{-0.15}({\rm syst.})$. The results are obtained with a full
data sample of $772 \times 10^6 B\bar{B}$ pairs collected near the
$\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy
$e^+e^-$ collider.
Phys. Rev. D 94, 012003 (2016) We present a search for a non-Standard-Model invisible particle $X^0$ in the
mass range $0.1\textrm{-}1.8 \,{\rm GeV}/{c^2}$ in $B^{+}\to e^{+} X^{0}$ and
$B^{+}\to ...\mu^{+} X^{0}$ decays. The results are obtained from a $711~{\rm
fb}^{-1}$ data sample that corresponds to $772 \times 10^{6} B\bar{B}$ pairs,
collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB
$e^+ e^-$ collider. One $B$ meson is fully reconstructed in a hadronic mode to
determine the momentum of the lepton of the signal decay in the rest frame of
the recoiling partner $B$ meson. We find no evidence of a signal and set upper
limits on the order of $10^{-6}$.
