A
bstract
A search for the
$$ {B}_{\mathrm{s}}^0 $$
B
s
0
→ D
*±
D
∓
decay is performed using proton-proton collision data at centre-of-mass energies of 7, 8 and 13 TeV collected by the LHCb ...experiment, corresponding to an integrated luminosity of 9 fb
−
1
. The decay is observed with a high significance and its branching fraction relative to the
B
0
→ D
*±
D
∓
decay is measured to be
$$ \frac{\mathrm{\mathcal{B}}\left({B}_s^0\to {D}^{\ast \pm }{D}^{\mp}\right)}{\left({B}^0\to {D}^{\ast \pm }{D}^{\mp}\right)}=0.137\pm 0.017\pm 0.002\pm 0.006, $$
ℬ
B
s
0
→
D
∗
±
D
∓
B
0
→
D
∗
±
D
∓
=
0.137
±
0.017
±
0.002
±
0.006
,
where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the
$$ {B}_{\mathrm{s}}^0 $$
B
s
0
and
B
0
hadronisation fractions.
Abstract
High-precision measurements of flow coefficients
$$v_{n}$$
v
n
(
$$n = 1 - 4$$
n
=
1
-
4
) for protons, deuterons and tritons relative to the first-order spectator plane have been performed ...in Au+Au collisions at
$$\sqrt{s_{_{{\text {NN}}}= 2.4$$
s
NN
=
2.4
GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at the SIS18/GSI. Flow coefficients are studied as a function of transverse momentum
$$p_{{\text {t}}}$$
p
t
and rapidity
$$y_{{\text {cm}}}$$
y
cm
over a large region of phase-space and for several classes of collision centrality. A clear mass hierarchy, as expected by relativistic hydrodynamics, is found for the slope of
$$v_{1}$$
v
1
,
$$d v_{1}/d y^{\prime }|_{y^{\prime } = 0}$$
d
v
1
/
d
y
′
|
y
′
=
0
where
$$y^{\prime }$$
y
′
is the scaled rapidity, and for
$$v_{2}$$
v
2
at mid-rapidity. Scaling with the number of nucleons is observed for the
$$p_{{\text {t}}}$$
p
t
dependence of
$$v_{2}$$
v
2
and
$$v_{4}$$
v
4
at mid-rapidity, which is indicative for nuclear coalescence as the main process responsible for light nuclei formation.
$$v_{2}$$
v
2
is found to scale with the initial eccentricity
$$\langle \epsilon _{2} \rangle $$
⟨
ϵ
2
⟩
, while
$$v_{4}$$
v
4
scales with
$$\langle \epsilon _{2} \rangle ^{2}$$
⟨
ϵ
2
⟩
2
and
$$\langle \epsilon _{4} \rangle $$
⟨
ϵ
4
⟩
. The multi-differential high-precision data on
$$v_{1}$$
v
1
,
$$v_{2}$$
v
2
,
$$v_{3}$$
v
3
, and
$$v_{4}$$
v
4
provides important constraints on the equation-of-state of compressed baryonic matter.
A
bstract
The decays
$$ {\mathrm{B}}_{\mathrm{s}}^0 $$
B
s
0
→ J
/
ψπ
+
π
−
K
+
K
−
are studied using a data set corresponding to an integrated luminosity of 9 fb
−
1
, collected with the LHCb ...detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays
$$ {\mathrm{B}}_{\mathrm{s}}^0 $$
B
s
0
→
$$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$
J
/
ψK
∗
0
K
¯
∗
0
and
$$ {\mathrm{B}}_{\mathrm{s}}^0 $$
B
s
0
→ χ
c1
(3872)K
+
K
−
, where the K
+
K
−
pair does not originate from a ϕ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χ
c1
(3872)ϕ,
$$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$
J
/
ψK
∗
0
K
¯
∗
0
, ψ(2S)ϕ and χ
c1
(3872)K
+
K
−
states are reported. A structure, denoted as X(4740), is observed in the J
/
ψϕ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be
$$ {\displaystyle \begin{array}{c}{m}_{\mathrm{X}(4740)}=4741\pm 6\pm 6\kern0.5em \mathrm{MeV}/{c}^2,\\ {}{\Gamma}_{\mathrm{X}(4740)}=53\pm 15\pm 11\kern0.5em \mathrm{MeV},\end{array}} $$
m
X
4740
=
4741
±
6
±
6
MeV
/
c
2
,
Γ
X
4740
=
53
±
15
±
11
MeV
,
where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the
$$ {\mathrm{B}}_{\mathrm{s}}^0 $$
B
s
0
meson is performed and gives a value of
$$ {m}_{{\mathrm{B}}_{\mathrm{s}}^0}=5366.98\pm 0.07\pm 0.13\kern0.5em \mathrm{MeV}/{c}^2. $$
m
B
s
0
=
5366.98
±
0.07
±
0.13
MeV
/
c
2
.
A
bstract
A measurement of
CP
-violating observables is performed using the decays
B
±
→
DK
±
and
B
±
→
Dπ
±
, where the
D
meson is reconstructed in one of the self-conjugate three-body final states
...$$ {K}_{\mathrm{S}}^0 $$
K
S
0
π
+
π
−
and
$$ {K}_{\mathrm{S}}^0 $$
K
S
0
K
+
K
−
(commonly denoted
$$ {K}_{\mathrm{S}}^0 $$
K
S
0
h
+
h
−
). The decays are analysed in bins of the
D
-decay phase space, leading to a measurement that is independent of the modelling of the
D
-decay amplitude. The observables are inter- preted in terms of the CKM angle
γ
. Using a data sample corresponding to an integrated luminosity of 9 fb
−
1
collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment,
γ
is measured to be
$$ \left({68.7}_{-5.1}^{+5.2}\right){}^{\circ} $$
68.7
−
5.1
+
5.2
°
. The hadronic parameters
$$ {r}_B^{D K},{r}_B^{D\pi},{\delta}_B^{D K},\kern0.5em \mathrm{and}\kern0.5em {\delta}_B^{D\pi} $$
r
B
DK
,
r
B
Dπ
,
δ
B
DK
,
and
δ
B
Dπ
, which are the ratios and strong-phase differences of the suppressed and favoured
B
±
decays, are also reported.
Abstract
A search is performed for heavy neutrinos in the decay of a
W
boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately
$$3.0\, \text {fb} ^{-1} ...$$
3.0
fb
-
1
of proton–proton collision data at centre-of-mass energies of 7 and
$$8\, \text {TeV} $$
8
TeV
collected with the LHCb experiment. Both same-sign and opposite-sign muons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at
$$95\%$$
95
%
confidence level in the heavy-neutrino mass range from 5 to
$$50\, \text {GeV/}c^2 $$
50
GeV/
c
2
. These are of the order of
$$10^{-3}$$
10
-
3
for lepton-number-conserving decays and of the order of
$$10^{-4}$$
10
-
4
for lepton-number-violating heavy-neutrino decays.
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