Mesons comprising a beauty quark and strange quark can oscillate between particle (Bs0) and antiparticle (B¯s0) flavour eigenstates, with a frequency given by the mass difference between heavy and ...light mass eigenstates, Δms. Here we present a measurement of Δms using Bs0→Ds−π+ decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Δms = 17.7683 ± 0.0051 ± 0.0032 ps−1, where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Δms precision by a factor of two. We combine this result with previous LHCb measurements to determine Δms = 17.7656 ± 0.0057 ps−1, which is the legacy measurement of the original LHCb detector.The LHCb collaboration reports an improved measurement of the oscillation frequency of mesons consisting of a bottom quark and strange quark, which is then combined with previous results.
Observation of new excited Bs0 states Alexander, M.; Baryshnikov, F.; Belov, I. ...
The European physical journal. C, Particles and fields,
07/2021, Letnik:
81, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A structure is observed in the
B
±
K
∓
mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a ...total integrated luminosity of 9
fb
-
1
. The structure is interpreted as the result of overlapping excited
B
s
0
states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to
B
±
K
∓
, are determined to be
m
1
=
6063.5
±
1.2
(stat)
±
0.8
(syst)
Me
,
Γ
1
=
26
±
4
(stat)
±
4
(syst)
Me
,
m
2
=
6114
±
3
(stat)
±
5
(syst)
Me
,
Γ
2
=
66
±
18
(stat)
±
21
(syst)
Me
.
Alternative values assuming a decay through
B
∗
±
K
∓
, with a missing photon from the
B
∗
±
→
B
±
γ
decay, which are shifted by approximately 45
Me
V, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed
B
s
2
∗
0
state is determined to be
0.87
±
0.15
(stat)
±
0.19
(syst)
.
The cross-sections of
ψ
(
2
S
)
meson production in proton-proton collisions at
s
=
13
TeV
are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of
...275
pb
-
1
. The production cross-sections for prompt
ψ
(
2
S
)
mesons and those for
ψ
(
2
S
)
mesons from
b
-hadron decays (
ψ
(
2
S
)
-from-
b
) are determined as functions of the transverse momentum,
p
T
, and the rapidity,
y
, of the
ψ
(
2
S
)
meson in the kinematic range
2
<
p
T
<
20
GeV/
c
and
2.0
<
y
<
4.5
. The production cross-sections integrated over this kinematic region are
σ
(
prompt
ψ
(
2
S
)
,
13
TeV
)
=
1.430
±
0.005
(stat)
±
0.099
(syst)
μ
b
,
σ
(
ψ
(
2
S
)
-from-
b
,
13
TeV
)
=
0.426
±
0.002
(stat)
±
0.030
(syst)
μ
b
.
A new measurement of
ψ
(
2
S
)
production cross-sections in
pp
collisions at
s
=
7
TeV
is also performed using data collected in 2011, corresponding to an integrated luminosity of
614
pb
-
1
. The integrated production cross-sections in the kinematic range
3.5
<
p
T
<
14
GeV/
c
and
2.0
<
y
<
4.5
are
σ
(
prompt
ψ
(
2
S
)
,
7
TeV
)
=
0.471
±
0.001
(stat)
±
0.025
(syst)
μ
b
,
σ
(
ψ
(
2
S
)
-from-
b
,
7
TeV
)
=
0.126
±
0.001
(stat)
±
0.008
(syst)
μ
b
.
All results show reasonable agreement with theoretical calculations.
A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like ...boson with mass from 30 to 200
\,GeV\!/
c
2
is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10
\,GeV\!/
c
2
up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90
\,GeV\!/
c
2
. The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at
s
=
13
\,TeV
, corresponding to an integrated luminosity of 5.4
\,fb
-
1
. No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.
A branching fraction measurement of the
B
0
→
D
s
+
π
-
decay is presented using proton–proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of
5.0
fb
-
...1
. The branching fraction is found to be
B
(
B
0
→
D
s
+
π
-
)
=
(
19.4
±
1.8
±
1.3
±
1.2
)
×
10
-
6
, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the
B
0
→
D
-
π
+
,
D
s
+
→
K
+
K
-
π
+
and
D
-
→
K
+
π
-
π
-
branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a
b
→
u
charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo–Kobayashi–Maskawa matrix element
V
ub
. Additionally, the collision energy dependence of the hadronisation-fraction ratio
f
s
/
f
d
is measured through
B
¯
s
0
→
D
s
+
π
-
and
B
0
→
D
-
π
+
decays.
The production of J/ψ pairs in proton–proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb−1 collected with the LHCb detector. The ...production cross-section for pairs with both J/ψ in the rapidity range 2<yJ/ψ<4.5 and transverse momentum pTJ/ψ<10 GeV/c isσJ/ψJ/ψ=5.1±1.0±1.1 nb, where the first uncertainty is statistical and the second systematic.
A
bstract
A search for the rare two-body charmless baryonic decay
B
+
→
p
Λ
¯
is performed with
pp
collision data, corresponding to an integrated luminosity of 3 fb
−1
, collected by the LHCb ...experiment at centre-of-mass energies of 7 and 8 TeV. An excess of
B
+
→
p
Λ
¯
candidates with respect to background expectations is seen with a statistical significance of 4.1 standard deviations, and constitutes the first evidence for this decay. The branching fraction, measured using the
B
+
→
K
S
0
π
+
decay for normalisation, is
ℬ
B
+
→
p
Λ
¯
=
2
.
4
−
0.8
+
1.0
±
0.3
×
1
0
−
7
,
where the first uncertainty is statistical and the second systematic.
An analysis of B±→DK± and B±→Dπ± decays is presented where the D meson is reconstructed in the two-body final states: K±π∓, K+K− and π+π−. Using 1.0 fb−1 of s=7TeVpp collisions, measurements of ...several observables are made including the first observation of the suppressed mode B±→π±K∓DK±. CP violation in B±→DK± decays is observed with 5.8σ significance.
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.
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