A
bstract
The decay-time-dependent
CP
asymmetry in
B
0
→ D
∗±
D
∓
decays is mea- sured using a data set corresponding to an integrated luminosity of 9 fb
−
1
recorded by the LHCb detector in ...proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The
CP
parameters are measured as
S
D
∗
D
=
−
0.861
±
0.077
stat
±
0.019
syst
,
Δ
S
D
∗
D
=
0.019
±
0.075
stat
±
0.012
syst
,
C
D
∗
D
=
−
0.059
±
0.092
stat
±
0.020
syst
,
ΔC
D
∗
D
=
−
0.031
±
0.092
stat
±
0.016
syst
,
A
D
∗
D
=
0.008
±
0.014
stat
±
0.006
syst
.
The analysis provides the most precise single measurement of
CP
violation in this decay channel to date. All parameters are consistent with their current world average values.
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.
Abstract
Using a data sample corresponding to an integrated luminosity of 2.0
$$\, \text {fb} ^{-1}$$
fb
-
1
, collected by the LHCb experiment, the production of the
$${\eta _{c}} (1S)$$
η
c
(
1
S
)
...state in proton–proton collisions at a centre-of-mass energy of
$$\sqrt{s} =13$$
s
=
13
$$\, \text {TeV}$$
TeV
is studied in the rapidity range
$$2.0< y < 4.5$$
2.0
<
y
<
4.5
and in the transverse momentum range
$$6.5< p_{\mathrm {T}} < 14.0 \, \text {GeV} $$
6.5
<
p
T
<
14.0
GeV
. The cross-section for prompt production of
$${\eta _{c}} (1S)$$
η
c
(
1
S
)
mesons relative to that of the
$${J /\psi }$$
J
/
ψ
meson is measured using the
$$p $$
p
$$\overline{{p}}$$
p
¯
decay mode and is found to be
$${\sigma _{{\eta _{c}} (1S)}/\sigma _{{{J /\psi }}} = 1.69 \pm 0.15 \pm 0.10 \pm 0.18}$$
σ
η
c
(
1
S
)
/
σ
J
/
ψ
=
1.69
±
0.15
±
0.10
±
0.18
. The quoted uncertainties are, in order, statistical, systematic and due to uncertainties on the branching fractions of the
$${{J /\psi }} \!\rightarrow {p} {\overline{{p}}} $$
J
/
ψ
→
p
p
¯
and
$${\eta _{c}} \!\rightarrow {p} {\overline{{p}}} $$
η
c
→
p
p
¯
decays. The prompt
$${\eta _{c}} (1S)$$
η
c
(
1
S
)
production cross-section is determined to be
$${\sigma _{{\eta _{c}} (1S)} = 1.26 \pm 0.11\pm 0.08\pm 0.14 \,\upmu \text {b}}$$
σ
η
c
(
1
S
)
=
1.26
±
0.11
±
0.08
±
0.14
μ
b
, where the last uncertainty includes that on the
$${J /\psi }$$
J
/
ψ
meson cross-section. The ratio of the branching fractions of
$$b $$
b
-hadron decays to the
$${\eta _{c}} (1S)$$
η
c
(
1
S
)
and
$${J /\psi }$$
J
/
ψ
states is measured to be
$${{\mathcal {B}} _{{b} \!\rightarrow {\eta _{c}} X}/{\mathcal {B}} _{{b} \!\rightarrow {{J /\psi }} X} = 0.48 \pm 0.03 \pm 0.03 \pm 0.05}$$
B
b
→
η
c
X
/
B
b
→
J
/
ψ
X
=
0.48
±
0.03
±
0.03
±
0.05
, where the last uncertainty is due to those on the branching fractions of the
$${{J /\psi }} \!\rightarrow {p} {\overline{{p}}} $$
J
/
ψ
→
p
p
¯
and
$${\eta _{c}} \!\rightarrow {p} {\overline{{p}}} $$
η
c
→
p
p
¯
decays. The difference between the
$${J /\psi }$$
J
/
ψ
and
$${\eta _{c}} (1S)$$
η
c
(
1
S
)
masses is also determined to be
$$113.0 \pm 0.7 \pm 0.1 \, \text {MeV} $$
113.0
±
0.7
±
0.1
MeV
, which is the most precise single measurement of this quantity to date.
A
bstract
Using proton-proton collision data, collected with the LHCb detector and corresponding to 1.0, 2.0 and 1.9 fb
−1
of integrated luminosity at the centre-of-mass energies of 7, 8, and 13 TeV, ...respectively, the decay
$$ {\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1} $$
Λ
b
0
→
χ
c
1
(3872)pK
−
with χ
c1
(3872) → J
/
ψ π
+
π
−
is observed for the first time. The significance of the observed signal is in excess of seven standard deviations. It is found that (58 ± 15)% of the decays proceed via the two-body intermediate state χ
c1
(3872)Λ(1520). The branching fraction with respect to that of the
$$ {\Lambda}_{\mathrm{b}}^0 $$
Λ
b
0
→ ψ(2S)pK
−
decay mode, where the ψ(2S) meson is reconstructed in the J
/
ψ π
+
π
−
final state, is measured to be:
$$ \frac{\beta \left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}(3872){\mathrm{pK}}^{-}\right)}{\beta \left({\Lambda}_{\mathrm{b}}^0\to \uppsi \left(2\mathrm{S}\right){\mathrm{pK}}^{-}\right)}\times \frac{\beta \left({\upchi}_{\mathrm{c}1}(3872)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}{\beta \left(\uppsi \left(2\mathrm{S}\right)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}=\left(5.4\pm 1.1\pm 0.2\right)\times {10}^{-2}, $$
β
Λ
b
0
→
χ
c
1
3872
pK
−
β
Λ
b
0
→
ψ
2
S
pK
−
×
β
χ
c
1
3872
→
J
/
ψ
π
+
π
−
β
ψ
2
S
→
J
/
ψ
π
+
π
−
=
5.4
±
1.1
±
0.2
×
10
−
2
,
where the first uncertainty is statistical and the second is systematic.
Search for the doubly charmed baryon $\Xi_{cc} Ackernley, T.; Albrecht, J.; Arnau Romeu, J. ...
Science China. Physics, mechanics & astronomy,
11/2019, Letnik:
63, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A search for the doubly charmed baryon $\Xi_{cc}^+$ is performed through its decay to the $Λ$ $^{+}_{c}$ K–π+ final state, using proton-proton collision data collected with the LHCb detector at ...centre-of-mass energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb–1. No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c2. Upper limits are set at 95% credibility level on the ratio of the $\Xi_{cc}^+$ production cross-section times the branching fraction to that of $Λ$ $^{+}_{c}$ and $\Xi_{cc}^{++}$ baryons. The limits are determined as functions of the $\Xi_{cc}^+$ mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c.
A
bstract
A new baryon state is observed in the
Λ
b
0
π
+
π
−
mass spectrum with high significance using a data sample of pp collisions, collected with the LHCb detector at centre-of-mass energies
s
...= 7
,
8 and 13 TeV, corresponding to an integrated luminosity of 9 fb
−
1
. The mass and natural width of the new state are measured to be
m
=
6072.3
±
2.9
±
0.6
±
0.2
MeV
,
Γ
=
72
±
11
±
2
MeV
,
where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the
Λ
b
0
baryon mass. The new state is consistent with the first radial excitation of the
Λ
b
0
baryon, the Λ
b
(2S)
0
resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed Λ
b
(5912)
0
and Λ
b
(5920)
0
states are also reported.
A
bstract
The ratio of branching fractions of the decays
Λ
b
0
→
pK
−
e
+
e
−
and
Λ
b
0
→
pK
−
μ
+
μ
−
,
R
pK
−
1
, is measured for the first time using proton-proton collision data corresponding to ...an integrated luminosity of 4
.
7 fb
−
1
recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range 0
.
1
< q
2
<
6
.
0 GeV
2
/c
4
and the
pK
−
mass range
m
(
pK
−
)
<
2600 MeV
/c
2
, the ratio of branching fractions is measured to be
R
pK
−
1
=
1.17
−
0.16
+
0.18
±
0.07
, where the first uncertainty is statistical and the second systematic. This is the first test of lepton universality with
b
baryons and the first observation of the decay
Λ
b
0
→
pK
−
e
+
e
−
.
A
bstract
The Cabibbo-suppressed semileptonic decay
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
p
¯
invariant mass using the decay mode
B
+
→ J/ψK
+
for normalisation. The total branching fraction is measured to be
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
