The number concentration of cloud particles is a
key quantity for understanding aerosol–cloud interactions and describing
clouds in climate and numerical weather prediction models. In contrast with
...recent advances for liquid clouds, few observational constraints exist
regarding the ice crystal number concentration (Ni). This study
investigates how combined lidar–radar measurements can be used to provide
satellite estimates of Ni, using a methodology that constrains
moments of a parameterized particle size distribution (PSD). The operational
liDAR–raDAR (DARDAR) product serves as an existing base for this method,
which focuses on ice clouds with temperatures Tc<-30 ∘C. Theoretical considerations demonstrate the capability for accurate retrievals
of Ni, apart from a possible bias in the concentration in small
crystals when Tc≳−50 ∘C, due to the assumption of
a monomodal PSD shape in the current method. This is verified via a
comparison of satellite estimates to coincident in situ measurements, which additionally
demonstrates the sufficient sensitivity of lidar–radar observations to
Ni. Following these results, satellite estimates of
Ni are evaluated in the context of a case study and a preliminary
climatological analysis based on 10 years of global data. Despite a lack
of other large-scale references, this evaluation shows a reasonable physical
consistency in Ni spatial distribution patterns. Notably,
increases in Ni are found towards cold temperatures and, more
significantly, in the presence of strong updrafts, such as those related to
convective or orographic uplifts. Further evaluation and improvement of this
method are necessary, although these results already constitute a first encouraging
step towards large-scale observational constraints for Ni. Part 2
of this series uses this new dataset to examine the controls on
Ni.
A
bstract
The production cross-sections of Υ mesons, namely Υ(1
S
), Υ(2
S
) and Υ(3
S
), in
pp
collisions at
$$ \sqrt{s} $$
s
= 5 TeV are measured with a data sample corresponding to an integrated ...luminosity of 9
.
13
±
0
.
18 pb
−
1
collected by the LHCb detector. The Υ mesons are reconstructed in the decay mode Υ →
μ
+
μ
−
. Double differential cross-sections times branching fractions, as functions of the transverse momentum
p
T
and the rapidity
y
of the Υ mesons, are measured in the range
p
T
<
20 GeV/
c
and 2
.
0
< y <
4
.
5. The results integrated over these
p
T
and
y
ranges are
$$ \sigma \left(\textrm{Y}(1S)\right)\times \mathcal{B}\left(\textrm{Y}(1S)\to {\mu}^{+}{\mu}^{-}\right)=2101\pm 33\pm 83\ \textrm{pb}, $$$ \sigma \left(\textrm{Y}(2S)\right)\times \mathcal{B}\left(\textrm{Y}(2S)\to {\mu}^{+}{\mu}^{-}\right)=526\pm 20\pm 21\ \textrm{pb}, $$$ \sigma \left(\textrm{Y}(3S)\right)\times \mathcal{B}\left(\textrm{Y}(3S)\to {\mu}^{+}{\mu}^{-}\right)=242\pm 16\pm 10\ \textrm{pb}, $$
σ
Υ
1
S
×
B
Υ
1
S
→
μ
+
μ
−
=
2101
±
33
±
83
pb
,
σ
Υ
2
S
×
B
Υ
2
S
→
μ
+
μ
−
=
526
±
20
±
21
pb
,
σ
Υ
3
S
×
B
Υ
3
S
→
μ
+
μ
−
=
242
±
16
±
10
pb
,
where the first uncertainties are statistical and the second are systematic. The ratios of cross-sections between measurements of two different Υ states and between measurements at different centre-of-mass energies are determined. The nuclear modification factor of Υ(1
S
) at
$$ \sqrt{s} $$
s
= 5 TeV is updated as well using the directly measured cross-section results from this analysis.
A
bstract
The ratio of branching fractions of
$$ {B}_c^{+}\to {B}_s^0{\pi}^{+} $$
B
c
+
→
B
s
0
π
+
and
$$ {B}_c^{+}\to J/\psi {\pi}^{+} $$
B
c
+
→
J
/
ψ
π
+
decays is measured with proton-proton ...collision data of a centre-of-mass energy of 13 TeV. The data were collected with the LHCb experiment during 2016–2018, corresponding to an integrated luminosity of 5
.
4 fb
−
1
. The
$$ {B}_s^0 $$
B
s
0
mesons are reconstructed via the decays
$$ {B}_s^0\to J/\psi \phi $$
B
s
0
→
J
/
ψϕ
and
$$ {B}_s^0\to {D}_s^{-}{\pi}^{+} $$
B
s
0
→
D
s
−
π
+
. The ratio of branching fractions is measured to be
$$ \mathcal{B}\left({B}_c^{+}\to {B}_s^0{\pi}^{+}\right)/\mathcal{B}\left({B}_c^{+}\to J/\psi {\pi}^{+}\right)=91\pm 10\pm 8\pm 3 $$
B
B
c
+
→
B
s
0
π
+
/
B
B
c
+
→
J
/
ψ
π
+
=
91
±
10
±
8
±
3
where the first uncertainty is statistical, the second is systematic and the third is due to the knowledge of the branching fractions of the intermediate state decays.
A
bstract
Evidence for the decays
B
0
→
$$ \overline{D} $$
D
¯
0
ϕ
and
B
0
→
$$ \overline{D} $$
D
¯
*0
ϕ
is reported with a significance of 3.6
σ
and 4.3
σ
, respectively. The analysis employs
pp
...collision data at centre-of-mass energies
$$ \sqrt{s} $$
s
= 7, 8 and 13 TeV collected by the LHCb detector and corresponding to an integrated luminosity of 9 fb
−
1
. The branching fractions are measured to be
$$ {\displaystyle \begin{array}{l}\mathcal{B}\left({B}^0\to {\overline{D}}^0\phi \right)=\left(7.7\pm 2.1\pm 0.7\pm 0.7\right)\times {10}^{-7},\\ {}\mathcal{B}\left({B}^0\to {\overline{D}}^{\ast 0}\phi \right)=\left(2.2\pm 0.5\pm 0.2\pm 0.2\right)\times {10}^{-6}.\end{array}} $$
B
B
0
→
D
¯
0
ϕ
=
7.7
±
2.1
±
0.7
±
0.7
×
10
−
7
,
B
B
0
→
D
¯
∗
0
ϕ
=
2.2
±
0.5
±
0.2
±
0.2
×
10
−
6
.
In these results, the first uncertainty is statistical, the second systematic, and the third is related to the branching fraction of the
B
0
→
$$ \overline{D} $$
D
¯
0
K
+
K
−
decay, used for normalisation. By combining the branching fractions of the decays
B
0
→
$$ {\overline{D}}^{\left(\ast \right)0}\phi $$
D
¯
∗
0
ϕ
and
B
0
→
$$ {\overline{D}}^{\left(\ast \right)0}\omega $$
D
¯
∗
0
ω
, the
ω
-
ϕ
mixing angle
δ
is constrained to be tan
2
δ
= (3
.
6 ± 0
.
7 ± 0
.
4) × 10
−
3
, where the first uncertainty is statistical and the second systematic. An updated measurement of the branching fractions of the
$$ {B}_s^0 $$
B
s
0
→
$$ {\overline{D}}^{\left(\ast \right)0}\phi $$
D
¯
∗
0
ϕ
decays, which can be used to determine the CKM angle
γ
, leads to
$$ {\displaystyle \begin{array}{c}\mathcal{B}\left({B}_s^0\to {\overline{D}}^0\phi \right)=\left(2.30\pm 0.10\pm 0.11\pm 0.20\right)\times {10}^{-5},\\ {}\mathcal{B}\left({B}_s^0\to {\overline{D}}^{\ast 0}\phi \right)=\left(3.17\pm 0.16\pm 0.17\pm 0.27\right)\times {10}^{-5}.\end{array}} $$
B
B
s
0
→
D
¯
0
ϕ
=
2.30
±
0.10
±
0.11
±
0.20
×
10
−
5
,
B
B
s
0
→
D
¯
∗
0
ϕ
=
3.17
±
0.16
±
0.17
±
0.27
×
10
−
5
.
A
bstract
The associated production of prompt
J/ψ
and
Υ
mesons in
pp
collisions at a centre-of-mass energy of
$$ \sqrt{s} $$
s
= 13 TeV is studied using LHCb data, corresponding to an integrated ...luminosity of 4 fb
−
1
. The measurement is performed for
J/ψ
(
Υ
) mesons with a transverse momentum
p
T
<
10 (30) GeV/
c
in the rapidity range 2
.
0
< y <
4
.
5. In this kinematic range, the cross-section of the associated production of prompt
J/ψ
and
Υ
(1
S
) mesons is measured to be 133 ± 22 ± 7 ± 3 pb, with a significance of 7
.
9
σ
, and that of prompt
J/ψ
and
Υ
(2
S
) mesons to be 76 ± 21 ± 4 ± 7 pb, with a significance of 4
.
9
σ
. The first uncertainty is statistical, the second systematic, and the third due to uncertainties on the used branching fractions. This is the first observation of the associated production of
J/ψ
and
Υ
(1
S
) in proton-proton collisions. Differential cross-sections are measured as functions of variables that are sensitive to kinematic correlations between the
J/ψ
and
Υ
(1
S
) mesons. The effective cross-sections of the associated production of prompt
J/ψ
and
Υ
mesons are obtained and found to be compatible with measurements using other particle productions.
A
bstract
The first observation of the
$$ {B}_s^0 $$
B
s
0
→
(
χ
c
1
(3872)
→ J/ψπ
+
π
−
)
π
+
π
−
decay is reported using proton-proton collision data, corresponding to integrated luminosities of 1, ...2 and 6 fb
−
1
, collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ratio of branching fractions relative to the
$$ {B}_s^0 $$
B
s
0
→
(
ψ
(2
S
)
→ J/ψπ
+
π
−
)
π
+
π
−
decay is measured to be
$$ \frac{\mathcal{B}\left({B}_s^0\to {\chi}_{c1}(3872){\pi}^{+}{\pi}^{-}\right)\times \mathcal{B}\left({\chi}_{c1}(3872)\to J/\psi {\pi}^{+}{\pi}^{-}\right)}{\mathcal{B}\left({B}_s^0\to \psi (2S){\pi}^{+}{\pi}^{-}\right)\times \mathcal{B}\left(\psi (2S)\to J/\psi {\pi}^{+}{\pi}^{-}\right)}=\left(6.8\pm 1.1\pm 0.2\right)\times {10}^{-2}, $$
B
B
s
0
→
χ
c
1
3872
π
+
π
−
×
B
χ
c
1
3872
→
J
/
ψ
π
+
π
−
B
B
s
0
→
ψ
2
S
π
+
π
−
×
B
ψ
2
S
→
J
/
ψ
π
+
π
−
=
6.8
±
1.1
±
0.2
×
10
−
2
,
where the first uncertainty is statistical and the second systematic. The mass spectrum of the
π
+
π
−
system recoiling against the
χ
c
1
(3872) meson exhibits a large contribution from
$$ {B}_s^0 $$
B
s
0
→ χ
c
1
(3872) (
f
0
(980)
→ π
+
π
−
) decays.
A
bstract
The first observation of the
$$ {\Lambda}_b^0\to {D}_s^{-}p $$
Λ
b
0
→
D
s
−
p
decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass ...energy of
$$ \sqrt{s} $$
s
= 13 TeV, corresponding to a total integrated luminosity of 6 fb
−
1
. Using the
$$ {\Lambda}_b^0\to {\Lambda}_c^{+}{\pi}^{-} $$
Λ
b
0
→
Λ
c
+
π
−
decay as the normalisation mode, the branching fraction of the
$$ {\Lambda}_b^0\to {D}_s^{-}p $$
Λ
b
0
→
D
s
−
p
decay is measured to be
$$ \mathcal{B}\left({\Lambda}_b^0\to {D}_s^{-}p\right)=\left(12.6\pm 0.5\pm 0.3\pm 1.2\right)\times {10}^{-6} $$
B
Λ
b
0
→
D
s
−
p
=
12.6
±
0.5
±
0.3
±
1.2
×
10
−
6
, where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the
$$ {\Lambda}_b^0\to {\Lambda}_c^{+}{\pi}^{-} $$
Λ
b
0
→
Λ
c
+
π
−
,
$$ {D}_s^{-}\to {K}^{-}{K}^{+}{\pi}^{-} $$
D
s
−
→
K
−
K
+
π
−
and
$$ {\Lambda}_c^{+}\to p{K}^{-}{\pi}^{+} $$
Λ
c
+
→
p
K
−
π
+
decays.
A
bstract
A search for direct
CP
violation in the Cabibbo-suppressed decay
$$ {D}_s^{+} $$
D
s
+
→ K
−
K
+
K
+
and in the doubly Cabibbo-suppressed decay
D
+
→
K
−
K
+
K
+
is reported. The analysis ...is performed with data collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb
−
1
. The search is conducted by comparing the
$$ {D}_{(s)}^{+} $$
D
s
+
and
$$ {D}_{(s)}^{-} $$
D
s
−
Dalitz-plot distributions through a model-independent binned technique, based on fits to the
K
−
K
+
K
+
invariant-mass distributions, with a total of 0.97 (1.27) million
$$ {D}_s^{+} $$
D
s
+
(
D
+
) signal candidates. The results are given as
p
-values for the hypothesis of
CP
conservation and are found to be 13.3% for the
$$ {D}_s^{+} $$
D
s
+
→ K
−
K
+
K
+
decay and 31.6% for the
D
+
→ K
−
K
+
K
+
decay. No evidence for
CP
violation is observed in these decays.
The algorithm presented in this paper was developed to retrieve ice water content (IWC) profiles in cirrus clouds. It is based on optimal estimation theory and combines ground-based visible lidar and ...thermal infrared (TIR) radiometer measurements in a common retrieval framework in order to retrieve profiles of IWC together with a correction factor for the backscatter intensity of cirrus cloud particles. As a first step, we introduce a method to retrieve extinction and IWC profiles in cirrus clouds from the lidar measurements alone and demonstrate the shortcomings of this approach due to the backscatter-to-extinction ambiguity. As a second step, we show that TIR radiances constrain the backscattering of the ice crystals at the visible lidar wavelength by constraining the ice water path (IWP) and hence the IWC, which is linked to the optical properties of the ice crystals via a realistic bulk ice microphysical model. The scattering phase function obtained from the microphysical model is flat around the backscatter direction (i.e., there is no backscatter peak). We show that using this flat backscattering phase function to define the backscatter-to-extinction ratio of the ice crystals in the retrievals with the lidar-only algorithm results in an overestimation of the IWC, which is inconsistent with the TIR radiometer measurements. Hence, a synergy algorithm was developed that combines the attenuated backscatter profiles measured by the lidar and the measurements of TIR radiances in a common optimal estimation framework to retrieve the IWC profile together with a correction factor for the phase function of the bulk ice crystals in the backscattering direction. We show that this approach yields consistent lidar and TIR results. The resulting lidar ratios for cirrus clouds are found to be consistent with previous independent studies.
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