We present an angular analysis of the B^{+}→K^{*+}(→K_{S}^{0}π^{+})μ^{+}μ^{-} decay using 9 fb^{-1} of pp collision data collected with the LHCb experiment. For the first time, the full set of ...CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B^{0}→K^{*0}μ^{+}μ^{-} decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
First observation of the decay B+ → π+μ+μ Adametz, A.; Adrover, C.; Ajaltouni, Z. ...
The journal of high energy physics,
12/2012, Letnik:
2012, Številka:
12
Journal Article
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A
bstract
A discovery of the rare decay
B
+
→
π
+
μ
+
μ
−
is presented. This decay is observed for the first time, with 5.2
σ
significance. The observation is made using
pp
collision data, ...corresponding to an integrated luminosity of 1.0 fb
−1
, collected with the LHCb detector. The measured branching fraction is (2.3 ± 0.6 (stat.) ± 0.1 (syst.))×10
−8
, and the ratio of the
B
+
→
π
+
μ
+
μ
−
and
B
+
→
K
+
μ
+
μ
−
branching fractions is measured to be 0.053 ± 0.014 (stat.) ± 0.001 (syst.).
A
bstract
A search for the doubly charmed baryon
$ \Xi_{cc}^{+} $
in the decay mode
$ \Xi_{cc}^{+}\to \Lambda_c^{+}{K^{-}}{\pi^{+}} $
is performed with a data sample, corresponding to an integrated ...luminosity of 0.65 fb
−1
, of
pp
collisions recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300-3800 MeV
/c
2
. Upper limits at the 95% confidence level on the ratio of the
$ \Xi_{cc}^{+} $
production cross-section times branching fraction to that of the
$ \Lambda_c^{+} $
,
R
, are given as a function of the
$ \Xi_{cc}^{+} $
mass and lifetime. The largest upper limits range from
R
< 1.5 × 10
−
2 for a lifetime of 100 fs to
R <
3
.
9 × 10
−4
for a lifetime of 400 fs.
Searches are performed for both promptlike and long-lived dark photons, A^{'}, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for A^{'}→μ^{+}μ^{-} ...decays using a data sample corresponding to an integrated luminosity of 5.5 fb^{-1} collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the γ-A^{'} kinetic mixing strength. The promptlike A^{'} search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 214<m(A^{'})≲740 MeV and 10.6<m(A^{'})≲30 GeV. The search for long-lived A^{'}→μ^{+}μ^{-} decays places world-leading constraints on low-mass dark photons with lifetimes O(1) ps.
Differences in the behaviour of matter and antimatter have been observed in K and B meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of ...fundamental interactions under the combined charge-conjugation and parity transformations, known as CP violation. Here, using data from the LHCb experiment at the Large Hadron Collider, we search for CP-violating asymmetries in the decay angle distributions of Λb0 baryons decaying to pπ-π+π- and pπ-K+K- final states. These four-body hadronic decays are a promising place to search for sources of CP violation both within and beyond the standard model of particle physics. We find evidence for CP violation in Λb0 to pπ-π+π- decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for CP violation in the baryon sector.
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First evidence of a structure in the J/ψΛ invariant mass distribution is obtained from an amplitude analysis of Ξb-→J/ψΛK- decays. The observed structure is consistent with being due ...to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8±2.9-1.1+4.7MeV and 17.3±6.5-5.7+8.0MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Ξ- states, Ξ1690- and Ξ1820-, are seen for the first time in a Ξb- decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb-1, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.
The relative rates of
B
-meson decays into
J
/
ψ
and
ψ
(2
S
) mesons are measured for the three decay modes in
pp
collisions recorded with the LHCb detector. The ratios of branching fractions (
) are ...measured to be
where the third uncertainty is from the ratio of the
ψ
(2
S
) and
J
/
ψ
branching fractions to
μ
+
μ
−
.
The first simultaneous test of muon-electron universality using B+→K+ℓ+ℓ− and B0→K*0ℓ+ℓ− decays is performed, in two ranges of the dilepton invariant-mass squared, q2. The analysis uses beauty mesons ...produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb−1. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
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