Resonant structures in the dipion mass spectrum from χc1(3872)→π+π−J/ψ decays, produced via B+→K+χc1(3872) decays, are analyzed using proton-proton collision data collected by the LHCb experiment, ...corresponding to an integrated luminosity of 9 fb−1. A sizeable contribution from the isospin conserving χc1(3872)→ωJ/ψ decay is established for the first time, (21.4±2.3±2.0)%, with a significance of more than 7.1σ. The amplitude of isospin violating decay, χc1(3872)→ρ0J/ψ, relative to isospin conserving decay, χc1(3872)→ωJ/ψ, is properly determined, and it is a factor of 6 larger than expected for a pure charmonium state.
A
bstract
The polarimeter vector field for multibody decays of a spin-half baryon is introduced as a generalisation of the baryon asymmetry parameters. Using a recent amplitude analysis of the
$$ ...{\Lambda}_c^{+} $$
Λ
c
+
→
pK
−
π
+
decay performed at the LHCb experiment, we compute the distribution of the kinematic-dependent polarimeter vector for this process in the space of Mandelstam variables to express the polarised decay rate in a model-agnostic form. The obtained representation can facilitate polarisation measurements of the
$$ {\Lambda}_c^{+} $$
Λ
c
+
baryon and eases inclusion of the
$$ {\Lambda}_c^{+} $$
Λ
c
+
→ pK
−
π
+
decay mode in hadronic amplitude analyses.
A
bstract
A Dalitz plot analysis of the
$$ {D}_s^{+} $$
D
s
+
→
π
−
π
+
π
+
decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a ...centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 1.5 fb
−
1
. The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the
π
+
π
−
S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the
$$ {D}_s^{+} $$
D
s
+
→ ω
(782)
π
+
channel in the
$$ {D}_s^{+} $$
D
s
+
→ π
−
π
+
π
+
decay. The resonant structures of the
$$ {D}_s^{+} $$
D
s
+
→ π
−
π
+
π
+
and
D
+
→ π
−
π
+
π
+
decays are compared, providing information about the mechanisms for the hadron formation in these decays.
A
bstract
Four decay modes of the
$$ {B}_c^{+} $$
B
c
+
meson into a
J/ψ
meson and multiple charged kaons or pions are studied using proton-proton collision data, collected with the LHCb detector at ...centre-of-mass energies of 7, 8, and 13 TeV and corresponding to an integrated luminosity of 9 fb
−
1
. The decay
$$ {B}_c^{+} $$
B
c
+
→ J/ψK
+
K
−
π
+
π
+
π
−
is observed for the first time, and evidence for the
$$ {B}_c^{+} $$
B
c
+
→ J/ψ
4
π
+
3
π
−
decay is found. The decay
$$ {B}_c^{+} $$
B
c
+
→ J/ψ
3
π
+
2
π
−
is observed and the previous observation of the
$$ {B}_c^{+} $$
B
c
+
→ ψ
(2
S
)
π
+
π
+
π
−
decay is confirmed using the
ψ
(2
S
) →
J/ψπ
+
π
−
decay mode. Ratios of the branching fractions of these four
$$ {B}_c^{+} $$
B
c
+
decay channels are measured.
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.
Abstract
The first study of
$$C\!P$$
C
P
violation in the decay mode
$${{B} ^\pm } \rightarrow {{K} ^+} {{K} ^-} {{\uppi } ^+} {{\uppi } ^-} _{D} h^\pm $$
B
±
→
K
+
K
-
π
+
π
-
D
h
±
, with
...$$h=K,\pi $$
h
=
K
,
π
, is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of
$$9\text {\,fb} ^{-1} $$
9
\,fb
-
1
. The analysis is performed in bins of phase space, which are optimised for sensitivity to local
$$C\!P$$
C
P
asymmetries.
$$C\!P$$
C
P
-violating observables that are sensitive to the angle
$$\gamma $$
γ
of the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for
$${{B} ^\pm } \rightarrow {{K} ^+} {{K} ^-} {{\uppi } ^+} {{\uppi } ^-} _{D} h^\pm $$
B
±
→
K
+
K
-
π
+
π
-
D
h
±
and
$${{B} ^\pm } \rightarrow {{\uppi } ^+} {{\uppi } ^-} {{\uppi } ^+} {{\uppi } ^-} _{D} h^\pm $$
B
±
→
π
+
π
-
π
+
π
-
D
h
±
decays.
Abstract
The interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between ...primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5
$$\,\text {Te\hspace{-1.00006pt}V}$$
Te
V
incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and
$$110\,\text {Ge\hspace{-1.00006pt}V\!/}c $$
110
Ge
V\!/
c
. The dominant antihyperon contribution, namely
$${\overline{\varLambda }} \rightarrow {\overline{{p}}} {{\pi } ^+} $$
Λ
¯
→
p
¯
π
+
decays from promptly produced
$$\overline{\varLambda }$$
Λ
¯
particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.
