Challenges in semileptonic B decays Gambino, P.; Kronfeld, A. S.; Rotondo, M. ...
The European physical journal. C, Particles and fields,
10/2020, Letnik:
80, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Two of the elements of the Cabibbo–Kobayashi–Maskawa quark mixing matrix,
|
V
ub
|
and
|
V
cb
|
, are extracted from semileptonic
B
decays. The results of the
B
factories, analysed in the light of ...the most recent theoretical calculations, remain puzzling, because for both
|
V
ub
|
and
|
V
cb
|
the exclusive and inclusive determinations are in clear tension. Further, measurements in the
τ
channels at Belle, Babar, and LHCb show discrepancies with the Standard Model predictions, pointing to a possible violation of lepton flavor universality. LHCb and Belle II have the potential to resolve these issues in the next few years. This article summarizes the discussions and results obtained at the MITP workshop held on April 9–13, 2018, in Mainz, Germany, with the goal to develop a medium-term strategy of analyses and calculations aimed at solving the puzzles. Lattice and continuum theorists working together with experimentalists have discussed how to reshape the semileptonic analyses in view of the much higher luminosity expected at Belle II, searching for ways to systematically validate the theoretical predictions in both exclusive and inclusive
B
decays, and to exploit the rich possibilities at LHCb.
Based on analysis of texture and in-grain misorientation axes (IGMA) distribution, we investigate the effects of initial orientation and deformation temperature on the rollability of magnesium alloy ...AZ31 and the associated deformation mechanisms. Plate samples oriented favorably for basal 〈
a
〉 slip exhibited the best rollability at room temperature, whereas under the warm-rolling condition, surprisingly, the plate oriented for prism 〈
a
〉 slip exhibited the best rollability. The enhanced rollability of the latter plate is attributed to increased activity of prism 〈
a
〉 slip, which exhibits a lower texture hardening rate than basal 〈
a
〉 slip. The increased activity of prism 〈
a
〉 slip is shown experimentally by the development of the
//RD texture and 〈0001〉-type IGMA distribution. Asymmetric texture is also suggested to impair the rollability of plate oriented for basal 〈
a
〉 slip.
A
bstract
We present a comprehensive study of high-energy double logarithms in inclusive DIS. They appear parametrically as
α
s
n
ln
2
n−k
x
at the
n
-th order in perturbation theory in the splitting ...functions for the parton evolution and the coefficient functions for the hard scattering process, and represent the leading corrections at small
x
in the flavour non-singlet case. We perform their resummation, in terms of modified Bessel functions, to all orders in full QCD up to NNLL accuracy, and partly to N
3
LL and beyond in the large-
n
c
limit, and provide fixed-order expansions up to five loops. In the flavour-singlet sector, where these double logarithms are sub-dominant at small
x
compared to single-logarithmic
α
s
n
x
−
1
ln
n−k
x
BFKL contributions, we construct fixed-order expansions up to five loops at NNLL accuracy in full QCD. The results elucidate the analytic small-
x
structure underlying inclusive DIS results in fixed-order perturbation theory and provide important information for present and future numerical and analytic calculations of these quantities.
The primary causes for the onset of major, midwinter, stratospheric sudden warming events remain unclear. In this paper, we report that 25 of the 27 events objectively identified in the ERA‐40 ...dataset for the period 1957–2001 are preceded by blocking patterns in the troposphere. The spatial characteristics of tropospheric blocks prior to sudden warming events are strongly correlated with the type of sudden warming event that follows. Vortex displacement events are nearly always preceded by blocking over the Atlantic basin only, whereas vortex splitting events are preceded by blocking events occurring in the Pacific basin or in both basins contemporaneously. The differences in the geographical blocking distribution prior to sudden warming events are mirrored in the patterns of planetary waves that are responsible for producing events of either type. The evidence presented here, suggests that tropospheric blocking plays an important role in determining the onset and the type of warmings.
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