A
bstract
A search for the doubly heavy
$$ {\Xi}_{bc}^0 $$
Ξ
bc
0
baryon using its decay to the
D
0
pK
–
final state is performed using proton-proton collision data at a centre-of-mass energy of 13 ...TeV collected by the LHCb experiment between 2016 and 2018, corresponding to an integrated luminosity of 5.4 fb
−
1
. No significant signal is found in the invariant mass range from 6.7 to 7.2 GeV/
c
2
. Upper limits are set at 95% credibility level on the ratio of the
$$ {\Xi}_{bc}^0 $$
Ξ
bc
0
production cross-section times its branching fraction to
D
0
pK
−
relative to that of the
$$ {\Lambda}_b^0\to {D}^0{pK}^{-} $$
Λ
b
0
→
D
0
pK
−
decay. The limits are set as a function of the
$$ {\Xi}_{bc}^0 $$
Ξ
bc
0
mass and lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and in the transverse momentum region from 5 to 25 GeV/
c
. Upper limits range from 1
.
7
×
10
−
2
to 3
.
0
×
10
−
1
for the considered
$$ {\Xi}_{bc}^0 $$
Ξ
bc
0
mass and lifetime hypotheses.
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.
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.
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
.
Abstract
Long-lived particles decaying to
$${e ^\pm } {\mu ^\mp } {\nu } $$
e
±
μ
∓
ν
, with masses between 7 and
$$50 \,\text {GeV/}c^2 $$
50
GeV/
c
2
and lifetimes between 2 and
$$50 \,\text {ps} ...$$
50
ps
, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using
$$5.4 \,\text {fb} ^{-1} $$
5.4
fb
-
1
of
$$p $$
p
$$p $$
p
collisions collected with the LHCb detector at a centre-of-mass energy of
$$\sqrt{s} = 13 \,\text {TeV} $$
s
=
13
TeV
. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of
$$125 \,\text {GeV/}c^2 $$
125
GeV/
c
2
, and the charged current production from an on-shell
$$W $$
W
boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes.
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 first search for
CP
violation in the Cabibbo-suppressed
Ξ
c
+
→
p
K
-
π
+
decay is performed using both a binned and an unbinned model-independent technique in the Dalitz plot. The studies are ...based on a sample of proton-proton collision data, corresponding to an integrated luminosity of
3.0
fb
-
1
, and collected by the LHCb experiment at centre-of-mass energies of 7 and
8
TeV
. The data are consistent with the hypothesis of no
CP
violation.
Using a data sample corresponding to an integrated luminosity of 0.35 fb-1 collected by LHCb in 2011, we report the first evidence of CP violation in the decays of Bs0} mesons to K±π∓ pairs, ...ACP(Bs0→Kπ)=0.27±0.08(stat)±0.02(syst), with a significance of 3.3σ. Furthermore, we report the most precise measurement of CP violation in the decays of B0 mesons to K±π∓ pairs, ACP(B0→Kπ)=-0.088±0.011(stat)±0.008(syst), with a significance exceeding 6σ.
PDF
