# nLab V_cb puzzle

Contents

### Context

#### Fields and quanta

fields and particles in particle physics

and in the standard model of particle physics:

force field gauge bosons

scalar bosons

flavors of fundamental fermions in the
standard model of particle physics:
generation of fermions1st generation2nd generation3d generation
quarks ($q$)
up-typeup quark ($u$)charm quark ($c$)top quark ($t$)
down-typedown quark ($d$)strange quark ($s$)bottom quark ($b$)
leptons
chargedelectronmuontauon
neutralelectron neutrinomuon neutrinotau neutrino
bound states:
mesonslight mesons:
pion ($u d$)
ρ-meson ($u d$)
ω-meson ($u d$)
f1-meson
a1-meson
strange-mesons:
ϕ-meson ($s \bar s$),
kaon, K*-meson ($u s$, $d s$)
eta-meson ($u u + d d + s s$)

charmed heavy mesons:
D-meson ($u c$, $d c$, $s c$)
J/ψ-meson ($c \bar c$)
bottom heavy mesons:
B-meson ($q b$)
ϒ-meson ($b \bar b$)
baryonsnucleons:
proton $(u u d)$
neutron $(u d d)$

(also: antiparticles)

effective particles

hadrons (bound states of the above quarks)

solitons

in grand unified theory

minimally extended supersymmetric standard model

superpartners

bosinos:

dark matter candidates

Exotica

auxiliary fields

# Contents

## Idea

In particle physics, what is called the $V_{cb}$-puzzle (status updates in GJS 19, Ricciardi 21) is an observation about the semileptonic decay of B-mesons (by the Belle collaboration and other experiments) which implies a value of the element $\left\vert V_{c b}\right\vert$ in the CKM matrix that differs from the apparent prediction of the standard model of particle physics with a statistical significance of about $3 \sigma$. But the form factors involved in this prediction suffer from theoretical uncertainties of quark contributions, and further lattice QCD-computation is expected to be required to clarify the actual prediction of the standard model of particle physics (GJS 19, last sentence).

The $V_{c b}$-puzzle is different from, but related to, the flavour anomalies (GJS 19 (6))

## References

• Paolo Gambino, Martin Jung, Stefan Schacht, The $V_{c b}$ puzzle: an update (arXiv:1905.08209)

• Giulia Ricciardi, Semileptonic B decays and $\vert V_{x b}\vert$ update (arXiv:2103.06099)

With emphasis on lattice QCD-computations:

Last revised on April 1, 2021 at 00:33:28. See the history of this page for a list of all contributions to it.