An amplitude analysis of the B^{0}→K^{*0}μ^{+}μ^{-} decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb^{-1} of pp collision data collected with the LHCb ...experiment. For the first time, the coefficients associated to short-distance physics effects, sensitive to processes beyond the standard model, are extracted directly from the data through a q^{2}-unbinned amplitude analysis, where q^{2} is the μ^{+}μ^{-} invariant mass squared. Long-distance contributions, which originate from nonfactorizable QCD processes, are systematically investigated, and the most accurate assessment to date of their impact on the physical observables is obtained. The pattern of measured corrections to the short-distance couplings is found to be consistent with previous analyses of b- to s-quark transitions, with the largest discrepancy from the standard model predictions found to be at the level of 1.8 standard deviations. The global significance of the observed differences in the decay is 1.4 standard deviations.
Full text
Available for:
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The production rate of Λ_{b}^{0} baryons relative to B^{0} mesons in pp collisions at a center-of-mass energy sqrts=13 TeV is measured by the LHCb experiment. The ratio of Λ_{b}^{0} to B^{0} ...production cross sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity. At low multiplicity, the ratio measured at LHCb is consistent with the value measured in e^{+}e^{-} collisions, and increases by a factor of ∼2 with increasing multiplicity. At relatively low transverse momentum, the ratio of Λ_{b}^{0} to B^{0} cross sections is higher than what is measured in e^{+}e^{-} collisions, but converges with the e^{+}e^{-} ratio as the momentum increases. These results imply that the evolution of heavy b quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed.
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23.
The ASACUSA antihydrogen and hydrogen program: results and prospects Malbrunot, C.; Amsler, C.; Cuendis, S. Arguedas ...
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
03/2018, Volume:
376, Issue:
2116
Journal Article
Peer reviewed
The goal of the ASACUSA-CUSP collaboration at the Antiproton Decelerator of CERN is to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. A milestone ...was achieved in 2012 through the detection of 80 antihydrogen atoms 2.7 m away from their production region. This was the first observation of 'cold' antihydrogen in a magnetic field free region. In parallel to the progress on the antihydrogen production, the spectroscopy beamline was tested with a source of hydrogen. This led to a measurement at a relative precision of 2.7 × 10⁻⁹ which constitutes the most precise measurement of the hydrogen hyperfine splitting in a beam. Further measurements with an upgraded hydrogen apparatus are motivated by CPT and Lorentz violation tests in the framework of the Standard Model Extension. Unlike for hydrogen, the antihydrogen experiment is complicated by the difficulty of synthesizing enough cold antiatoms in the ground state. The first antihydrogen quantum states scan at the entrance of the spectroscopy apparatus was realized in 2016 and is presented here. The prospects for a ppm measurement are also discussed. This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.
Tuning is an essential requirement for the search of dark matter axions employing haloscopes since its mass is not known yet to the scientific community. At the present day, most haloscope tuning ...systems are based on mechanical devices which can lead to failures due to the complexity of the environment in which they are used. However, the electronic tuning making use of ferroelectric materials can provide a path that is less vulnerable to mechanical failures and thus complements and expands current tuning systems. In this work, we present and design a novel concept for using the ferroelectric Potassium Tantalate (\(KTaO_3\) or KTO) material as a tuning element in haloscopes based on coupled microwave cavities. In this line, the structures used in the Relic Axion Detector Exploratory Setup (RADES) group are based on several cavities that are connected by metallic irises, which act as interresonator coupling elements. In this article, we also show how to use these \(KTaO_3\) films as interresonator couplings between cavities, instead of inductive or capacitive metallic windows used in the past. These two concepts represent a crucial upgrade over the current systems employed in the dark matter axions community, achieving a tuning range of \(2.23 \, \%\) which represents a major improvement as compared to previous works (\(<0.1 \, \%\)) for the same class of tuning systems. The theoretical and simulated results shown in this work demonstrate the interest of the novel concepts proposed for the incorporation of this kind of ferroelectric media in multicavity resonant haloscopes in the search for dark matter axions.
We describe the results of a haloscope axion search performed with an 11.7 T dipole magnet at CERN. The search used a custom-made radio-frequency cavity coated with high-temperature superconducting ...tape. A set of 27 h of data at a resonant frequency of around 8.84 GHz was analysed. In the range of axion mass 36.5676 \(\mu\)eV to 36.5699 \(\mu\)eV, corresponding to a width of 554 kHz, no signal excess hinting at an axion-like particle was found. Correspondingly, in this mass range, a limit on the axion to photon coupling-strength was set in the range between g\(_{a\gamma}\gtrsim\) 6.2e-13 GeV\(^{-1}\) and g\(_{a\gamma}\gtrsim\) 1.54e-13 GeV\(^{-1}\) with a 95% confidence level.
First observation of the Λb0→ D+D−Λ decay Aidala, C. A.; Albrecht, J.; Aliouche, Z. ...
The journal of high energy physics,
16/7, Volume:
2024, Issue:
7
Journal Article
Peer reviewed
Open access
A
bstract
The
Λ
b
0
→
D
+
D
−
Λ decay is observed for the first time using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an ...integrated luminosity of 5
.
3 fb
−
1
. Using the
B
0
→
D
+
D
−
K
S
0
decay as a reference channel, the product of the relative production cross-section and decay branching fractions is measured to be
R
=
σ
Λ
b
0
σ
B
0
=
B
Λ
b
0
→
D
+
D
−
Λ
B
B
0
→
D
+
D
−
K
S
0
=
0.179
±
0.022
±
0.014
,
where the first uncertainty is statistical and the second is systematic. The known branching fraction of the reference channel,
B
B
0
→
D
+
D
−
K
S
0
, and the cross-section ratio,
σ
Λ
b
0
/
σ
B
0
, previously measured by LHCb are used to derive the branching fraction of the
Λ
b
0
→ D
+
D
−
Λ decay
B
Λ
b
0
→
D
+
D
−
Λ
=
1.24
±
0.15
±
0.10
±
0.28
±
0.11
×
10
−
4
,
where the third and fourth contributions are due to uncertainties of
B
B
0
→
D
+
D
−
K
S
0
and
σ
Λ
b
0
/
σ
B
0
, respectively. Inspection of the
D
+
Λ and
D
+
D
−
invariant-mass distributions suggests a rich presence of intermediate resonances in the decay. The
Λ
b
0
→
D
*+
D
−
Λ decay is also observed for the first time as a partially reconstructed component in the
D
+
D
−
Λ invariant mass spectrum.
Search for the Bs0→ μ+μ−γ decay Agapopoulou, C.; Alessio, F.; Amey, J. L. ...
The journal of high energy physics,
11/7, Volume:
2024, Issue:
7
Journal Article
Peer reviewed
Open access
A
bstract
A search for the fully reconstructed
B
s
0
→ μ
+
μ
−
γ
decay is performed at the LHCb experiment using proton-proton collisions at
s
= 13 TeV corresponding to an integrated luminosity of 5
....
4 fb
−
1
. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set
B
B
s
0
→
μ
+
μ
−
γ
<
4.2
×
10
−
8
,
m
μ
+
μ
−
∈
2
m
μ
1.70
GeV
/
c
2
,
B
B
s
0
→
μ
+
μ
−
γ
<
7.7
×
10
−
8
,
m
μ
+
μ
−
∈
1.70, 2.88
GeV
/
c
2
,
B
B
s
0
→
μ
+
μ
−
γ
<
4.2
×
10
−
8
,
m
μ
+
μ
−
∈
3.92
m
B
s
0
GeV
/
c
2
,
at 95% confidence level. Additionally, upper limits are set on the branching fraction in the 2
m
μ
,
1
.
70 GeV
/c
2
dimuon mass region excluding the contribution from the intermediate
ϕ
(1020) meson, and in the region combining all dimuon-mass intervals.
Amplitude analysis of the Λb0→pK−γ decay Amhis, Y.; Andersson, M.; Bachmayer, M. ...
The journal of high energy physics,
18/6, Volume:
2024, Issue:
6
Journal Article
Peer reviewed
Open access
A
bstract
The resonant structure of the radiative decay
Λ
b
0
→
pK
−
γ
in the region of proton-kaon invariant-mass up to 2.5 GeV/
c
2
is studied using proton-proton collision data recorded at ...centre-of-mass energies of 7, 8, and 13 TeV collected with the LHCb detector, corresponding to a total integrated luminosity of 9 fb
−
1
. Results are given in terms of fit and interference fractions between the different components contributing to this final state. Only Λ resonances decaying to
pK
−
are found to be relevant, where the largest contributions stem from the Λ(1520), Λ(1600), Λ(1800), and Λ(1890) states.
A
bstract
Measurements of the branching fraction ratio
B
ϕ
→
μ
+
μ
−
/
B
ϕ
→
e
+
e
−
with
D
s
+
→
π
+
ϕ
and
D
+
→ π
+
ϕ
decays, denoted
R
ϕπ
s
and
R
ϕπ
d
, are presented. The analysis is performed ...using a dataset corresponding to an integrated luminosity of 5
.
4 fb
−
1
of
pp
collision data collected with the LHCb experiment. The branching fractions are normalised with respect to the
B
+
→
K
+
J/ψ
(→
e
+
e
−
) and
B
+
→
K
+
J/ψ
(→
μ
+
μ
−
) decay modes. The combination of the results yields
R
ϕπ
=
1.022
±
0.012
stat
±
0.048
syst
.
The result is compatible with previous measurements of the
ϕ
→
ℓ
+
ℓ
−
branching fractions and predictions based on the Standard Model.
A
bstract
The cross-section of associated
J/ψ
-
ψ
(2
S
) production in proton-proton collisions at a centre-of-mass energy of
s
= 13 TeV is measured using a data sample corresponding to an integrated ...luminosity of 4
.
2 fb
−
1
, collected by the LHCb experiment. The measurement is performed for both
J/ψ
and
ψ
(2
S
) mesons having transverse momentum
p
T
<
14 GeV/
c
and rapidity 2
.
0
< y <
4
.
5, assuming negligible polarisation of the
J/ψ
and
ψ
(2
S
) mesons. The production cross-section is measured to be 4
.
5 ± 0
.
7 ± 0
.
3 nb, where the first uncertainty is statistical and the second systematic. The differential cross-sections are measured as functions of several kinematic variables of the
J/ψ
-
ψ
(2
S
) candidates. The results are combined with a measurement of
J/ψ
-
J/ψ
production, giving a cross-section ratio between
J/ψ
-
ψ
(2
S
) and
J/ψ
-
J/ψ
production of 0
.
274 ± 0
.
044 ± 0
.
008, where the first uncertainty is statistical and the second systematic.
