A search for baryon-number violating Ξ0b oscillations is performed with a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 fb-1. The baryon ...number at the moment of production is identified by requiring that the Ξ0b come from the decay of a resonance Ξ*b- → Ξ0bπ- or Ξ'b- → Ξ0bπ-, and the baryon number at the moment of decay is identified from the final state using the decays Ξ0b → Ξ+cπ-, Ξ+c → pK-π+. No evidence of baryon-number violation is found, and an upper limit at the 95% confidence level is set on the oscillation rate of ω < 0.08 ps-1, where ω is the associated angular frequency.
At small Bjorken-x, the large gluon number density in the nucleon leads to gluon recombination competing with gluon splitting, which could result in saturation of the gluon PDF. This gluon saturation ...has yet to be conclusively observed. Direct photon production provides sensitivity to gluon densities in protons and nuclei, and the forward acceptance of LHCb detector allows for measurements of this process at low Bjorken-x, providing an ideal probe of saturation effects. Progress towards the measurement of forward direct photon production using the LHCb detector is presented.
A
bstract
A search for
B
+
→
D
s
+
K
+
K
−
decays is performed using
pp
collision data corresponding to an integrated luminosity of 4.8 fb
−1
, collected at centre-of-mass energies of 7, 8 and 13 ...TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to be
ℬ
B
+
→
D
s
+
K
+
K
−
=
7.1
±
0.5
±
0.6
±
0.7
×
1
0
−
6
,
where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode
B
+
→
D
s
+
D
¯
0
. A search is also performed for the pure annihilation decay
B
+
→
D
s
+
ϕ
. No significant signal is observed and a limit of
ℬ
B
+
→
D
s
+
ϕ
<
4.9
×
1
0
−
7
4.2
×
1
0
−
7
is set on the branching fraction at 95% (90%) confidence level.
A
bstract
A precision measurement of the
$$ {B}_c^{+} $$
B
c
+
meson mass is performed using proton- proton collision data collected with the LHCb experiment at centre-of-mass energies of 7
,
8 and ...13 TeV, corresponding to a total integrated luminosity of 9
.
0 fb
−
1
. The
$$ {B}_c^{+} $$
B
c
+
mesons are reconstructed via the decays
$$ {B}_c^{+} $$
B
c
+
→ J/ψπ
+
,
$$ {B}_c^{+} $$
B
c
+
→ J/ψπ
+
π
−
π
+
,
$$ {B}_c^{+}\to J/\psi p\overline{p}{\pi}^{+} $$
B
c
+
→
J
/
ψp
p
¯
π
+
,
$$ {B}_c^{+}\to J/\psi {D}_s^{+} $$
B
c
+
→
J
/
ψ
D
s
+
,
$$ {B}_c^{+} $$
B
c
+
→ J/ψ D
0
K
+
and
$$ {B}_c^{+}\to {B}_s^0{\pi}^{+} $$
B
c
+
→
B
s
0
π
+
. Combining the results of the individual decay channels, the
$$ {B}_c^{+} $$
B
c
+
mass is measured to be 6274
.
47
±
0
.
27 (stat)
±
0
.
17 (syst) MeV
/c
2
. This is the most precise measurement of the
$$ {B}_c^{+} $$
B
c
+
mass to date. The difference between the
$$ {B}_c^{+} $$
B
c
+
and
$$ {B}_s^0 $$
B
s
0
meson masses is measured to be 907
.
75
±
0
.
37 (stat)
±
0
.
27 (syst) MeV
/c
.
This paper presents an analysis of the \( {\Lambda}_b^0 \) → J/ψΛ angular distribution and the transverse production polarisation of \( {\Lambda}_b^0 \) baryons in proton-proton collisions at ...centre-of-mass energies of 7, 8 and 13 TeV. The measurements are performed using data corresponding to an integrated luminosity of 4.9 fb–1, collected with the LHCb experiment. The polarisation is determined in a fiducial region of \( {\Lambda}_b^0 \) transverse momentum and pseudorapidity of 1 < pT < 20 GeV/c and 2 < η < 5, respectively. The data are consistent with \( {\Lambda}_b^0 \) baryons being produced unpolarised in this region. The parity-violating asymmetry parameter of the Λ → pπ– decay is also determined from the data and its value is found to be consistent with a recent measurement by the BES III collaboration.
A
bstract
The Cabibbo-suppressed semileptonic decay
$$ {B}^{+}\to p\overline{p}{\mu}^{+}{\nu}_{\mu } $$
B
+
→
p
p
¯
μ
+
ν
μ
is observed for the first time using a sample of
pp
collisions ...corresponding to an integrated luminosity of 1.0, 2.0 and 1.7 fb
−
1
at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The differential branching fraction is measured as a function of the
$$ p\overline{p} $$
p
p
¯
invariant mass using the decay mode
B
+
→ J/ψK
+
for normalisation. The total branching fraction is measured to be
$$ \mathrm{\mathcal{B}}\left({B}^{+}\to p\overline{p}{\mu}^{+}{\nu}_{\mu}\right)=\left({5.27}_{-0.24}^{+0.23}\pm 0.21\pm 0.15\right)\times {10}^{-6}, $$
ℬ
B
+
→
p
p
¯
μ
+
ν
μ
=
5.27
−
0.24
+
0.23
±
0.21
±
0.15
×
10
−
6
,
where the first uncertainty is statistical, the second systematic and the third is from the uncertainty on the branching fraction of the normalisation channel.
PDF
