Angular analysis of B 0 → D ∗ − D s ∗ + $$ {B}^0\to {D}^{\ast -}{D}_s^{\ast +} $$ with D s ∗ + → D s + γ $$ {D}_s^{\ast +}\to {D}_s^{+}\gamma $$ decays
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13130_2021_Article_16089.pdf
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Author(s)
Aaij, R.
Abellán Beteta, C.
Ackernley, T.
Adeva, B.
Adinolfi, M.
Afsharnia, H.
Aidala, C. A.
Aiola, S.
Ajaltouni, Z.
Akar, S.
Date Issued
June 29, 2021
Publisher
Springer Berlin Heidelberg
Citation
Journal of High Energy Physics. 2021 Jun 29;2021(6):177
Version
Final published version
Abstract
Abstract
The first full angular analysis of the
B
0
→
D
∗
−
D
s
∗
+
$$ {B}^0\to {D}^{\ast -}{D}_s^{\ast +} $$
decay is performed using 6 fb−1 of pp collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The
D
s
∗
+
→
D
s
+
γ
$$ {D}_s^{\ast +}\to {D}_s^{+}\gamma $$
and D*− →
D
¯
0
π
−
$$ {\overline{D}}^0{\pi}^{-} $$
vector meson decays are used with the subsequent
D
s
+
$$ {D}_s^{+} $$
→ K+K−π+ and
D
¯
0
$$ {\overline{D}}^0 $$
→ K+π− decays. All helicity amplitudes and phases are measured, and the longitudinal polarisation fraction is determined to be fL = 0.578 ± 0.010 ± 0.011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [ℬ(
B
0
→
D
∗
−
D
s
∗
+
$$ {B}^0\to {D}^{\ast -}{D}_s^{\ast +} $$
) × ℬ(
D
s
∗
+
→
D
s
+
γ
$$ {D}_s^{\ast +}\to {D}_s^{+}\gamma $$
)]/ℬ(B0 → D*−
D
s
+
$$ {D}_s^{+} $$
) is measured to be 2.045 ± 0.022 ± 0.071 with world-best precision. In addition, the first observation of the Cabibbo-suppressed Bs → D*−
D
s
+
$$ {D}_s^{+} $$
decay is made with a significance of seven standard deviations. The branching fraction ratio ℬ(Bs → D*−
D
s
+
$$ {D}_s^{+} $$
)/ℬ(B0 → D*−
D
s
+
$$ {D}_s^{+} $$
) is measured to be 0.049 ± 0.006 ± 0.003 ± 0.002, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1007/JHEP06(2021)177
