Selected topics from Belle

The Belle experiment continues to explore the origin of CP violation and test all aspects of standard model inB meson decays. Recent results on CP violating paramter sin2ф₁ and other measurements are presented.     

A technique for improving the observation of CP-nonconservation inB 0 meson decays

In this paper, we show that it may be possible to increase the observability of the CP-violation inB ⁰-meson decays by measuring theB ⁰-meson decay rate as a function of time. We calculate the asymmetry in the time-dependent rate at which aB ⁰-meson and its conjugate particle decay to a given final state. We also calculate the time dependence of the decay rate asymmetry for a correlated \(B - \bar B\) pair. It is suggested that searches for CP-violation lose information by integrating away the time dependence. We then calculate the gain in signal strength from watching the evolution of theB-meson states as a function of time.     

Phenomenological applications of<Emphasis Type="Italic">k</Emphasis><Subscript>T</Subscript>factorization

We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two-bodyB-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approach. PQCD results are compatible with present experimental data for charmless B-meson decays. We predict the possibility of large direct CP asymmetry in B⁰ → π⁺π⁻ (23 +7%) and B⁰ →K ⁺π⁻ (− 17 ± 5%). We also investigate the branching ratios, CP asymmetry and isospin symmetry breaking in radiativeB →(K*/ρ)γ decays.     

QCD factorization for forward hadron scattering at high energies

We calculate the branching ratios and CP asymmetries of the B???Ц?, ?Ц? decays in the perturbative QCD factorization approach up to the next-to-leading-order contributions. We find that the next-to-leading-order contributions can interfere with the leading-order part constructively or destructively for different decay modes. Our numerical results have a much better agreement with current available data than previous leading-order calculations, e.g., the next-to-leading-order corrections enhance the B ⁰???? ⁰ ?? ⁰ branching ratios by a factor 2.5, which is helpful to narrow the gaps between theoretic predictions and experimental data. We also update the direct CP-violation parameters, the mixing-induced CP-violation parameters of these modes, which show a better agreement with experimental data than many of the other approaches.     

<Emphasis Type="Italic">B</Emphasis>-meson decays into charmonium states in the ATLAS experiment

The paper presents several recent ATLAS results on the analyses of B-meson decays into charmonium states. These include the measurements of B⁺ mass and the fractions of J/ψ mesons produced in b-hadron decays in pp collisions at \(\sqrt s\) = 13 TeV in the center of mass system. The measured partial widths and polarizations in B _c ⁺ → J/ψD _s ^(*)+ decays and CP-violation parameters in B _s ⁰ → J/ψ? decays in pp collisions at 7 and 8 TeV in the center of mass system are also presented.     

Studies of radiative penguinB decays at BaBar

We summarize results on a number of observations of penguin dominated radiative decays of theB meson. Such decays are forbidden at tree level and proceed via electroweak loops. As such they may be sensitive to physics beyond the standard model. The observations have been made at the BaBar experiment at PEP-II, the asymmetricB factory at SLAC.     

Determination of the b -quark mass and nonperturbative parameters in semileptonic B -meson decays at BABAR⋆

Knowing the mass of the b -quark is essential to the study of the structure and decays of B -mesons as well as to future tests of the Higgs mechanism of mass generation. We present recent preliminary measurements of the b -quark mass and related nonperturbative parameters from moments of kinematic distributions in charmed and charmless semileptonic B -meson decays. Their determination from charmless semileptonic B -meson decays is the first measurement in this mode. The data were collected by the BABAR detector at the PEP-II asymmetric-energy e ⁺ e ^- -collider at the Stanford Linear Accelerator Center at a center-of-mass energy of 10.58GeV. Original article based on material presented at HADRON 2007.     

The interplay between “low” and “high” energy CP-violation in leptogenesis

We analyse, within the “flavoured” leptogenesis scenario of baryon asymmetry generation, the interplay of “low energy” CP-violation, originating from the PMNS neutrino mixing matrix U, and “high energy” CP-violation, which can be present in the matrix of neutrino Yukawa couplings, λ, and can manifest itself only in “high” energy scale processes. The type I see-saw model with three heavy right-handed Majorana neutrinos having a hierarchical spectrum is considered. The “orthogonal” parameterisation of the matrix of neutrino Yukawa couplings, which involves a complex orthogonal matrix R, is employed. In this approach the matrix R is the source of “high energy” CP-violation. Results for normal hierarchical (NH) and inverted hierarchical (IH) light neutrino mass spectrum are derived in the case of decoupling of the heaviest right-handed Majorana neutrino. It is shown that taking into account the contribution to Y _B due to the CP-violating phases in the neutrino mixing matrix U can change drastically the predictions for Y _B , obtained assuming that only “high energy” CP-violation from the R-matrix is operative in leptogenesis. In the case of the IH spectrum, in particular, there exist significant regions in the corresponding parameter space where the purely “high energy” contribution in Y _B plays a subdominant role in the production of baryon asymmetry compatible with the observations. Also at Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 1784 Sofia, Bulgaria.     

B c meson properties and its leptonic radiative decays

The properties of the meson B _c are outlined. The leptonic radiative decays for B _c meson are presented. An outlook on the studies of the meson is given.     

Beauty-conserving strangeness-changing rare semileptonic decays ofB s meson

The beauty-conserving strangeness-changing decays ofB _s meson are examined. In the charm sector, charm-conserving strangeness changing (Δc = 0, Δs ≠ 0) decays are Cabibbo suppressed and are governed by the CKM elementV _us which is much smaller than the CKM diagonal elementV _cs, so may be of little interest. On the other hand, in theb-sector, beauty-conserving strangeness changing (Δb = 0, Δs ≠ 0) decays are CKM allowed as the CKM matrix elementV _us governing such decays is much larger thanV _bc orV _bu which govern respectively theb →c orb →u transitions. The phase space available, however, is too small for the decays considered here. The numerical estimates for the decay widths of two such modes ofB _s meson are presented.     

Measuring absolute branching ratios of charmed baryons in B decays

The B factories are expected to provide huge samples of single B decay events with little background by reconstructing one of the B mesons produced in decays. This represents a new experimental paradigm: such samples will allow to make measurements of a quality previously thought unrealistic. As example we discuss how absolute branching ratios for exclusive as well as inclusive charm baryon decays can be extracted. One starts out by observing decays like as a signature for etc. and then exploits various correlations of the flavour of the B meson with the baryon number of the (anti)proton and other observables like the charge of a lepton, baryon number of another baryon etc. An integrated luminosity of about 500 fb^-1 as could be available by 2005 should be sufficient for the task. Received: 21 December 2001 / Published online: 8 May 2002     

On the role of the final-state interactions in rare <Emphasis Type="Italic">B</Emphasis> decays

The effects of final-state interactions (FSI) in hadronic B decays are investigated. The model for FSI, based on Regge phenomenology of high-energy hadronic interactions, is proposed. It is shown that this model explains the pattern of phases in matrix elements of B → ππ and B → ρρ decays. These phases play an important role for CP violation in B decays. The most precise determination of the unitarity triangle angle α from B _d → ρπ decays is performed. The relation between CP asymmetries in B → Kπ decays is discussed. It is emphasized that the large-distance FSI can explain the structure of polarizations of the vector mesons in B decays and other puzzles like a very large branching ratio of the B decay to $ \bar \Xi $ \bar \Xi _c Λ _c .     

New physics effects from B meson decays

In this talk, we point out some of the present and future possible signatures of physics beyond the Standard Model from B-meson decays, taking R-parity conserving and violating supersymmetry as illustrative examples. An expanded version is available on hep-ph archive.     

Shape distortions of meson resonances produced in hadron interactions atP T≧2 GeV/c

Using the ARGUS detector at thee ⁺ e ^– storage ring DORIS II, flavour-dependent kaon production inB meson decays has been studied. Using the leptons as flavour tags, it has been possible to separately measure the multiplicities ofK ⁺,K ^– andK _s ⁰ in inclusiveB decays and in semileptonicB decays. The kaon production in semileptonicB decays was further used to estimate the ratio of charmed decays over all decays, and thus also the fraction of charmlessB decays.DESY, IfH Zeuthen     

ψ(3770) and B meson exclusive decay B → ψ(3770)K in QCD factorization

Belle has observed surprisingly copious production of ψ(3770) in the B meson decay B → ψ(3770)K, whose rate is comparable to that of B → ψ(3686)K. We study this puzzling process in the QCD factorization approach with the effect of the S-D mixing considered. We find that the soft scattering effects in the spectator interactions play an essential role. With a proper parametrization for the higher-twist soft end-point singularities associated with kaon, and with the S-D mixing angle θ = - 12^°, the calculated decay rates can be close to the data. Implications of these soft spectator effects to other charmonium production in B exclusive decays are also emphasized.     

Status ofV ub measurement with BELLE detector

Semileptonic decays ofB →X _u lv have great importance both from theoretical and experimental point of view, as they are useful for extracting the magnitude ofV _ub, one of the tiniest elements of CKM matrix. Similarly measurement ofB √ D_s×_u can be used to calculateV _ub The Belle Collaboration has measured these branching ratios and extractedV _ub for various theoretical models.     

New physics with beauty

We review the effects of new physics on CP asymmetries and decays of B mesons. Possible sources and corresponding signals for new physics are studied briefly. We discuss how the decay mode b → s ℓℓ (and B → K*ℓℓ) will enable us to understand the nature of new physics. We also examine the possibility of truly clean signature of new physics — a signature based on observables alone and without hadronic uncertainties.     

Puzzles in B physics

I discuss some puzzles observed in exclusive B-meson decays, concentrating on the large difference between the direct CP asymmetries in the B ⁰ → π⁻ K ⁼ and B ^± → π⁰ K ^± modes, the large B ⁰ → π⁰π⁰ branching ratio, and the large deviation of the mixing-induced CP asymmetries in the b → sqq penguins from those in the b → ccs trees.     

CP-violating asymmetries inη′K and direct CP violation searches with BABAR in charmless hadronicB meson decays

We present preliminary results of the measurement of branching fractions and CP violating asymmetries inB meson decays toη′K and ØK*. We update also the results of the direct CP violation searches with BABAR in charmless hadronicB meson decays.     

Search for new physics at a super-<Emphasis Type="Italic">B</Emphasis> factory

The importance of a super-B factory in the search for new physics, in particular, due to CP-odd phase(s) from physics beyond the standard model is surveyed. The first point to emphasize is that we now know how to directly measure all three angles of the unitarity triangle very cleanly, i.e. without theoretical assumptions with irreducible theory error ≲1%. However, this requires much more luminosity than is currently available atB-factories. Direct searches via penguin-dominated hadronic modes as well as radiative, pair-leptonic and semi-leptonic decays are also discussed. Null tests of the SM are stressed as these will play a crucial role especially if the effects of BSM phase(s) onB-physics are small.