A
bstract
A data sample collected with the LHCb detector corresponding to an integrated luminosity of 9 fb
−
1
is used to measure eleven
CP
violation observables in
B
±
→ Dh
±
decays, where
h
is ...either a kaon or a pion. The neutral
D
meson decay is reconstructed in the three-body final states:
K
±
π
∓
π
0
;
π
+
π
−
π
0
;
K
+
K
−
π
0
and the suppressed
π
±
K
∓
π
0
combination. The mode where a large
CP
asymmetry is expected,
B
±
→
π
±
K
∓
π
0
D
K
±
, is observed with a significance greater than seven standard deviations. The ratio of the partial width of this mode relative to that of the favoured mode,
B
±
→
K
±
π
∓
π
0
D
K
±
, is
R
ADS(
K
)
= (1
.
27
±
0
.
16
±
0
.
02)
×
10
−
2
. Evidence for a large
CP
asymmetry is also seen:
A
ADS(
K
)
= −0
.
38
±
0
.
12
±
0
.
02. Constraints on the CKM angle
γ
are calculated from the eleven reported observables.
The first full amplitude analysis of B^{+}→J/ψϕK^{+} with J/ψ→μ^{+}μ^{-}, ϕ→K^{+}K^{-} decays is performed with a data sample of 3 fb^{-1} of pp collision data collected at sqrts=7 and 8 TeV with ...the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK^{+}, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.
Amplitude analysis of the Ds+→ π−π+π+ decay Amhis, Y.; Andersson, M.; Bachmann, S. ...
The journal of high energy physics,
07/2023, Letnik:
2023, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
A Dalitz plot analysis of the
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
+
→ ω
(782)
π
+
channel in the
D
s
+
→ π
−
π
+
π
+
decay. The resonant structures of the
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.
The multihadron decays
Λ
b
0
→
D
+
pπ−π−
and
Λ
b
0
→
D
*
+
pπ−π−
are observed in data corresponding to an integrated luminosity of 3 fb
−
1
, collected in proton-proton collisions at centre-of-mass ...energies of 7 and 8 TeV by the LHCb detector. Using the decay
Λ
b
0
→
Λ
c
+
π
+
π
−
π
−
as a normalisation channel, the ratio of branching fractions is measured to be
B
Λ
b
0
→
D
+
p
π
−
π
−
B
Λ
b
0
→
Λ
c
0
π
+
π
−
π
−
×
B
D
+
→
K
−
π
+
π
+
B
Λ
c
0
→
pK
−
π
−
=
5.35
±
0.21
±
0.16
%
,
where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the
Λ
b
0
→
D
*+
pπ
−
π
−
and
Λ
b
0
→
D
+
pπ
−
π
−
decays is found to be
B
Λ
b
0
→
D
∗
+
p
π
−
π
−
B
Λ
b
0
→
D
+
p
π
−
π
−
×
B
D
∗
+
→
D
+
π
0
+
B
D
∗
+
→
D
+
γ
=
61.3
±
4.3
±
4.0
%
.
Search for the decay B0→ ϕμ+μ Alfonso Albero, A.; Anderlini, L.; Bachmayer, M. ...
The journal of high energy physics,
11/5, Letnik:
2022, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A
bstract
A search for the decay
B
0
→ ϕμ
+
μ
−
is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an ...integrated luminosity of 9 fb
−
1
. No evidence for the
B
0
→ ϕμ
+
μ
−
decay is found and an upper limit on the branching fraction, excluding the
ϕ
and charmonium regions in the dimuon spectrum, of 4
.
4
×
10
−
3
at a 90% credibility level, relative to that of the
B
s
0
→ ϕμ
+
μ
−
decay, is established. Using the measured
B
s
0
→ ϕμ
+
μ
−
branching fraction and assuming a phase-space model, the absolute branching fraction of the decay
B
0
→ ϕμ
+
μ
−
in the full
q
2
range is determined to be less than 3
.
2
×
10
−
9
at a 90% credibility level.
A
bstract
The
Ξ
cc
+
+
→
Ξ
c
′
+
π
+
decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity ...of 5
.
4 fb
−
1. The
Ξ
cc
+
+
→
Ξ
c
′
+
π
+
decay is reconstructed partially, where the photon from the
Ξ
c
′
+
→
Ξ
c
+
γ
decay is not reconstructed and the
pK
−
π
+
final state of the
Ξ
c
+
baryon is employed. The
Ξ
cc
+
+
→
Ξ
c
′
+
π
+
branching fraction relative to that of the
Ξ
cc
+
+
→
Ξ
c
+
π
+
decay is measured to be 1
.
41
±
0
.
17
±
0
.
10, where the first uncertainty is statistical and the second systematic.
A search for a long-lived scalar particle χ is performed, looking for the decay B+→K+χ with χ→μ+μ− in pp collision data corresponding to an integrated luminosity of 3 fb−1, collected by the LHCb ...experiment at center-of-mass energies of s=7 and 8 TeV. This new scalar particle, predicted by hidden sector models, is assumed to have a narrow width. The signal would manifest itself as an excess in the dimuon invariant mass distribution over the Standard Model background. No significant excess is observed in the accessible ranges of mass 250<m(χ)<4700 MeV/c2 and lifetime 0.1<τ(χ)<1000 ps. Upper limits on the branching fraction B(B+→K+χ(μ+μ−)) at 95% confidence level are set as a function of m(χ) and τ(χ), varying between 2×10−10 and 10−7. These are the most stringent limits to date. The limits are interpreted in the context of a model with a light inflaton particle.
After rapid approval and installation, the SND@LHC Collaboration was able to gather data successfully in 2022 and 2023. Neutrino interactions from νμs originating at the LHC IP1 were observed. Since ...muons constitute the major background for neutrino interactions, the muon flux entering the acceptance was also measured. To improve the rejection power of the detector and to increase the fiducial volume, a third Veto plane was recently installed. The energy resolution of the calorimeter system was measured in a test beam. This will help with the identification of νe interactions that can be used to probe charm production in the pseudo-rapidity range of SND@LHC (7.2 < η < 8.4). Events with three outgoing muons have been observed and are being studied. With no vertex in the target, these events are very likely from muon trident production in the rock before the detector. Events with a vertex in the detector could be from trident production, photon conversion, or positron annihilation. To enhance SND@LHC’s physics case, an upgrade is planned for HL-LHC that will increase the statistics and reduce the systematics. The installation of a magnet will allow the separation of νμ from ν¯μ
A
bstract
The production cross-sections of Υ mesons, namely Υ(1
S
), Υ(2
S
) and Υ(3
S
), in
pp
collisions at
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
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
s
= 5 TeV is updated as well using the directly measured cross-section results from this analysis.
Measurement of τL using the Bs0→J/ψη decay mode Adeva, B.; Cartelle, P. Alvarez; Artuso, M. ...
The European physical journal. C, Particles and fields,
07/2023, Letnik:
83, Številka:
7
Journal Article
Recenzirano
Odprti dostop
Using a proton–proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of
5.7
fb
-
1
, the lifetime of the light
B
s
0
mass eigenstate,
τ
L
, is ...measured using the
B
s
0
→
J
/
ψ
η
decay mode to be
τ
L
=
1.445
±
0.016
(stat)
±
0.008
(syst)
ps
.
A combination of this result with a previous LHCb analysis using an independent dataset corresponding to 3 fb
-
1
of integrated luminosity gives
τ
L
=
1.452
±
0.014
±
0.007
±
0.002
ps
,
where the first uncertainty is statistical, the second due to the uncorrelated part of the systematic uncertainty and the third due to the correlated part of the systematic uncertainty.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
PDF
