The problem of magnetic field generation by fluid motions driven by thermal buoyancy in a rotating spherical shell is considered. In extension of earlier work on this problem particular attention is ...devoted to questions of numerical convergence and of sequences of bifurcations. Finite amplitude convection and nonlinear dynamo solutions are found at Rayleigh numbers below the critical value for the onset of convection. Chaotic solutions appear to be preferred in large regions of the parameter space of the problem.
The CP-violating asymmetry asls is studied using semileptonic decays of Bs0 and B¯s0 mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample ...corresponding to an integrated luminosity of 1.0 fb−1. The reconstructed final states are Ds±μ∓, with the Ds± particle decaying in the ϕπ± mode. The Ds±μ∓ yields are summed over B¯s0 and Bs0 initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain asls=(−0.06±0.50±0.36)%, where the first uncertainty is statistical and the second systematic.
Search for the decay D0→π+π−μ+μ Amhis, Y.; Badalov, A.; Bowcock, T.J.V. ...
Physics letters. B,
01/2014, Letnik:
728
Journal Article
Recenzirano
Odprti dostop
A search for the D0→π+π−μ+μ− decay, where the muon pair does not originate from a resonance, is performed using proton–proton collision data corresponding to an integrated luminosity of 1.0fb−1 ...recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D0→π+π−ϕ(→μ+μ−), under the assumption of a phase-space model, is found to beB(D0→π+π−μ+μ−)/B(D0→π+π−ϕ(→μ+μ−))<0.96 at 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D0→π+π−μ+μ−)<5.5×10−7 at 90% confidence level. This is the most stringent to date.
We have made the first observation of B{sub s}{sup 0}{yields}D{sub s}{sup (*)+}D{sub s}{sup (*)-} decays using 23.6 fb{sup -1} of data recorded by the Belle experiment running on the {Upsilon}(5S) ...resonance. The branching fractions are measured to be B(B{sub s}{sup 0}{yields}D{sub s}{sup +}D{sub s}{sup -})=(1.03{sub -0.32-0.25}{sup +0.39+0.26})%, B(B{sub s}{sup 0}{yields}D{sub s}{sup *{+-}}D{sub s}{sup {-+}})=(2.75{sub -0.71}{sup +0.83}{+-}0.69)%, and B(B{sub s}{sup 0}{yields}D{sub s}{sup *+}D{sub s}{sup *-})=(3.08{sub -1.04-0.86}{sup +1.22+0.85})%; the sum is BB{sub s}{sup 0}{yields}D{sub s}{sup (*)+}D{sub s}{sup (*)-}=(6.85{sub -1.30-1.80}{sup +1.53+1.79})%. Assuming B{sub s}{sup 0}{yields}D{sub s}{sup (*)+}D{sub s}{sup (*)-} saturates decays to CP-even final states, the branching fraction determines the ratio {Delta}{Gamma}{sub s}/cos{phi}, where {Delta}{Gamma}{sub s} is the difference in widths between the two B{sub s}-B{sub s} mass eigenstates, and {phi} is a CP-violating weak phase. Taking CP violation to be negligibly small, we obtain {Delta}{Gamma}{sub s}/{Gamma}{sub s}=0.147{sub -0.030}{sup +0.036}(stat){sub -0.041}{sup +0.042}(syst), where {Gamma}{sub s} is the mean decay width.
We report results of a search for the invisible decay of the Upsilon(1S) via the Upsilon(3S)-->pi+ pi- Upsilon(1S) transition using a data sample of 2.9 fb-1 at the Upsilon(3S) resonance. The data ...were collected with the Belle detector at the KEKB asymmetric-energy e+ e- collider. No signal is found, and an upper limit for the branching fraction at the 90% confidence level is determined to be B(Upsilon(1S)-->invisible)<2.5 x 10(-3).
A
bstract
The first observation of the decay
$ B_s^0\to \phi \overline{K}{*^0} $
is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb
−1
of
pp
...collisions at
$ \sqrt{s}=7 $
TeV, collected with the LHCb detector. A yield of 30 ± 6
$ B_s^0\to \left( {{K^{+}}{K^{-}}} \right)\left( {{K^{-}}{\pi^{+}}} \right) $
decays is found in the mass windows 1012.5 <
M
(
K
+
K
−
) < 1026.5 MeV/
c
2
and 746 <
M
(
K
−
π
+
) < 1046 MeV/
c
2
. The signal yield is found to be dominated by
$ B_s^0\to \phi \overline{K}{*^0} $
decays, and the corresponding branching fraction is measured to be
$ \mathcal{B}\left( {B_s^0\to \phi \overline{K}{*^0}} \right) $
= (1.10 ± 0.24 (stat) ± 0.14 (syst) ± 0.08 (
f
d
/
f
s
)) × 10
−6
, where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions
f
d
/
f
s
which accounts for the different production rate of
B
0
and
$ B_s^0 $
mesons. The significance of
$ B_s^0\to \phi \overline{K}{*^0} $
signal is 6.1 standard deviations. The fraction of longitudinal polarization in
$ B_s^0\to \phi \overline{K}{*^0} $
decays is found to be
f
0
= 0.51 ± 0.15 (stat) ± 0.07 (syst).
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