CP Violation Bigi, I. I.; Sanda, A. I.
04/2009, Letnik:
28
eBook
Why didn't the matter in our Universe annihilate with antimatter immediately after its creation? The study of CP violation may help to answer this fundamental question. This book presents theoretical ...tools necessary to understand this phenomenon. Reflecting the explosion of new results over the last decade, this second edition has been substantially expanded. It introduces charge conjugation, parity and time reversal, before describing the Kobayashi-Maskawa (KM) theory for CP violation and our understanding of CP violation in kaon decays. It reveals how the discovery of B mesons has provided a new laboratory to study CP violation with KM theory predicting large asymmetries, and discusses how these predictions have been confirmed since the first edition of this book. Later chapters describe the search for a new theory of nature's fundamental dynamics. This book is suitable for researchers in high energy, atomic and nuclear physics and the history and philosophy of science.
We present predictions based on the heavy quark expansion in QCD. We find SU(3) breaking in
B
mesons suppressed in the framework of the HQE.
B
s
is expected to have the semileptonic width about 1% ...lower and Λ
b
about 3% higher when compared to Γ
sl
(
B
d
). The largest partial-rate preasymptotic effect is Pauli interference in the
b
→
uℓν
channel in Λ
b
, about +10%. We point out that the Ω
b
semileptonic width is expected not to exceed that of
B
d
and may turn out to be the smallest among stable
b
hadrons despite the large mass. The underlying differences with phase-space models are briefly addressed through the heavy mass expansion.
We point out that dynamics known from the observed CP violation in
K
L
→
π
∓
l
±
ν
coupled with CPT invariance generate a CP asymmetry of
3.3
×
10
−3
in
τ
±
→
ν
K
S
π
±
→
ν
π
+
π
−
K
π
±
. The ...equality of the
τ
+
and
τ
−
lifetimes required by CPT symmetry is restored in an intriguing way as the combined effect of long-lived
K
→
π
+
π
−
as well as contributions from
K
L
–
K
S
interference. While little new can be learnt from this CP asymmetry, the latter has to be accounted for, since CP asymmetries in
τ
→
ν
K
π
channels are prime candidates for revealing the intervention of New Physics. This ‘known’ CP asymmetry provides a very useful calibration point in such searches. It also provides a test of CPT symmetry (as well as the
Δ
Q
=
Δ
S
selection rule).
The key quantity of the heavy quark theory is the quark mass ital msub ital Q. Since quarks are unobservable one can suggest different definitions of ital msub ital Q. One of the most popular choices ...is the pole quark mass routinely used in perturbative calculations and in some analyses based on heavy quark expansions. We show that no precise definition of the pole mass can be given in the full theory once nonperturbative effects are included. Any definition of this quantity suffers from an intrinsic uncertainty of order Lambdasub QCD/ital msub ital Q. This fact is succinctly described by the existence of an infrared renormalon generating a factorial divergence in the high-order coefficients of the alphasub ital s series; the corresponding singularity in the Borel plane is situated at 2pi/ital b. A peculiar feature is that this renormalon is not associated with the matrix element of a local operator. The difference bar Lambdaequivalent toital Msub ital Hital Q-ital msub ital Qsup pole can still be defined by heavy quark effective theory, but only at the price of introducing an explicit dependence on a normalization point mu: bar Lambda(mu). Fortunately the pole mass ital msub ital Q(0) ital per ital se does not appear in calculable observable quantities.
We derive the lepton spectrum in semileptonic ital b decays from a nonperturbative treatment of QCD; it is based on an expansion in 1/ital msub ital Q with ital msub ital Q being the heavy flavor ...quark mass. The leading corrections arising on the 1/ital msub ital Q level are completely expressed in terms of the difference in the mass of the heavy hadron and the quark. Nontrivial effects appear in 1/ital msub ital Qsup 2 terms affecting mainly the end-point region; they are different for meson and baryon decays as well as for bottom and charm decays.
ASPECTS OF HEAVY-QUARK THEORY Bigi, I.; Shifman, M.; Uraltsev, N.
Annual review of nuclear and particle science,
12/1997, Letnik:
47, Številka:
1
Journal Article
Recenzirano
Odprti dostop
▪ Abstract Recent achievements in heavy-quark theory are critically reviewed. The emphasis is put on those aspects that either did not attract enough attention or cause heated debates in the current ...literature. Among other topics we discuss (a) basic parameters of the heavy-quark theory; (b) a class of exact QCD inequalities; (c) new heavy quark sum rules; (d) the virial theorem; (e) applications (|V
cb
| from the total semileptonic width and from the B → D* transition at zero recoil). In some instances new derivations of previously known results are given, or new aspects addressed. In particular, we dwell on the exact QCD inequalities. Furthermore, a toy model is considered that may shed light on the controversy regarding the value of the kinetic energy of heavy quarks obtained by different methods.
A
bstract
Indirect and direct CP violations have been established in
K
L
and
B
d
decays. They have been found in two-body decay channels — with the exception of
K
L
→
π
+
π
−
e
+
e
−
transitions. ...Evidence for direct CP asymmetry has just appeared in LHCb data on
A
CP
(
D
0
→
K
+
K
−
) −
A
CP
(
D
0
→
π
+
π
−
) with 3.5
σ
significance. Manifestations of New Dynamics (ND) can appear in CP asymmetries just below experimental bounds. We discuss
,
and
D
L
/
D
S
transitions to 2-, 3- and 4-body final states with a comment on predictions for inclusive vs. exclusive CP asymmetries. In particular we discuss T asymmetries in
D
→
h
1
h
2
l
+
l
−
in analogy with
K
L
→
π
+
π
−
e
+
e
−
transitions due to interference between M1, internal bremsstrahlung and possible E1 amplitudes. Such an effect depends on the strength of CP violation originating from the ND — as discussed here for Little Higgs Models with T parity and non-minimal Higgs sectors — but also in the interferences between these amplitudes even in the Standard Model. More general lessons can be learnt for T asymmetries in non-leptonic
D
decays like
D
→
h
1
h
2
h
3
h
4
. Such manifestations of ND can be tested at LHCb and other Super-Flavour Factories like the projects at KEK near Tokyo and at Tor Vergata/Frascati near Rome.
We know that our Universe is composed of only ～4.5% “known” matter; therefore, our understanding is incomplete. This can be seen directly in the case of neutrino oscillations (without even ...considering potential other universes). Charm quarks have had considerable impact on our understanding of known matter, and quantum chromodynamics (QCD) is the only local quantum field theory to describe strong forces. It is possible to learn novel lessons concerning strong dynamics by measuring rates around the thresholds of Q ¯ Q states with Q = b, c. Furthermore, these states provide us with gateways towards new dynamics (ND), where we must transition from “accuracy” to “precision” eras. Finally, we can make connections with τ transitions and, perhaps, with dark matter. Charm dynamics acts as a bridge between the worlds of light- and heavy-flavor hadrons (namely, beauty hadrons), and finding regional asymmetries in many-body final states may prove to be a “game changer”. There are several different approaches to achieving these goals: for example, experiments such as the Super Tau-Charm Factory, Super Beauty Factory, and the Super Z 0 Factory act as gatekeepers – and deeper thinking regarding symmetries.
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