254 research outputs found
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Search for lepton-flavour-violating decays of Higgs-like bosons.
A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV , collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1 . The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/c2 to 4 pb for a mass of 195 GeV/c2
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Measurement of CP observables in the process B <sup>0</sup> â DK <sup>*0</sup> with two- and four-body D decays
Measurements of observables in decays are presented,
where represents a superposition of and states. The
meson is reconstructed in the two-body final states , ,
and , and, for the first time, in the four-body final
states , and .
The analysis uses a sample of neutral mesons produced in proton-proton
collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 collected with the LHCb detector at centre-of-mass energies of
7, 8 and 13 TeV, respectively. First observations of the decays
and are
obtained. The measured observables are interpreted in terms of the
-violating weak phase
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Updated measurement of time-dependent CP -violating observables in Bs0âJ/Ï<sup>K+</sup><sup>K-</sup> decays
The decay-time-dependent asymmetry in
decays is measured using proton-proton collision data, corresponding to an
integrated luminosity of , collected with the LHCb
detector at a centre-of-mass energy of in 2015 and 2016.
Using a sample of approximately 117\,000 signal decays with an invariant mass in the vicinity of the resonance, the -violating
phase is measured, along with the difference in decay widths of the
light and heavy mass eigenstates of the - system,
. The difference of the average and meson
decay widths, , is determined using in addition a sample of
decays. The values obtained are , and , where the first uncertainty is statistical and the
second systematic. These are the most precise single measurements of these
quantities to date and are consistent with expectations based on the Standard
Model and with a previous LHCb analysis of this decay using data recorded at
centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with
recent results from decays obtained using
the same dataset as this analysis, and with previous independent LHCb results
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Observation of the Îb0âÏc1 (3872) pK<sup>â</sup> decay
Using proton-proton collision data, collected with the LHCb detector and
corresponding to 1.0, 2.0 and 1.9fb of integrated luminosity at the
centre-of-mass energies of 7, 8, and 13 TeV, respectively, the decay
with is
observed for the first time. The significance of the observed signal is in
excess of seven standard deviations. It is found that of the
decays proceed via the two-body intermediate state
. The~branching fraction with respect to that of
the decay mode, where the
~meson is reconstructed in the final state, is
measured to be: \begin{equation*}
\frac{\Lambda_b^0\to\chi_{c1}(3872)pK^-}{\Lambda_b\to\psi(2S)p K^-} \times
\frac{\mathcal{B}(\chi_{c1} \to J/\psi \pi^+\pi^-)}{\mathcal{B}(\psi(2S)\to
J/\psi \pi^+\pi^-)} = \left(5.4 \pm 1.1 \pm 0.2\right)\times 10^{-2}\,,
\end{equation*} where the first uncertainty is statistical and the second is
systematic
Observation of Two New Excited Îb0 States Decaying to Îb0 K-Ï+
Two narrow resonant states are observed in the Îb0K-Ï+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb-1. The minimal quark content of the Îb0K-Ï+ system indicates that these are excited Îb0 baryons. The masses of the Îb(6327)0 and Îb(6333)0 states are m[Îb(6327)0]=6327.28-0.21+0.23±0.12±0.24 and m[Îb(6333)0]=6332.69-0.18+0.17±0.03±0.22 MeV, respectively, with a mass splitting of Îm=5.41-0.27+0.26±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Îb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Î[Îb(6327)0]<2.20(2.56) and Î[Îb(6333)0]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Îb0 resonances
Search for CP violation in Îb0âpKâ and Îb0âpÏâ decays
A search for CP violation in Îb0âpKâ and Îb0âpÏâ decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0fbâ1. The CP -violating asymmetries are measured to be ACPpKâ=â0.020±0.013±0.019 and ACPpÏâ=â0.035±0.017±0.020, and their difference ACPpKââACPpÏâ=0.014±0.022±0.010, where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date
Test of lepton universality in decays
The first simultaneous test of muon-electron universality using
and decays is performed, in two ranges of the dilepton
invariant-mass squared, . 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 . Each
of the four lepton universality measurements reported is either the first in
the given interval or supersedes previous LHCb measurements. The
results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb
public pages
Precision measurement of violation in the penguin-mediated decay
A flavor-tagged time-dependent angular analysis of the decay
is performed using collision data collected
by the LHCb experiment at % at TeV, the center-of-mass energy of
13 TeV, corresponding to an integrated luminosity of 6 fb^{-1}. The
-violating phase and direct -violation parameter are measured
to be rad and
, respectively, assuming the same values
for all polarization states of the system. In these results, the
first uncertainties are statistical and the second systematic. These parameters
are also determined separately for each polarization state, showing no evidence
for polarization dependence. The results are combined with previous LHCb
measurements using collisions at center-of-mass energies of 7 and 8 TeV,
yielding rad and . This is the most precise study of time-dependent violation
in a penguin-dominated meson decay. The results are consistent with
symmetry and with the Standard Model predictions.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-001.html (LHCb
public pages
Observation of B(s)0âJ/ÏppÂŻ decays and precision measurements of the B(s)0 masses
The first observation of the decays
B
0
(
s
)
â
J
/
Ï
p
ÂŻ
p
is reported, using proton-proton collision data corresponding to an integrated luminosity of
5.2
â
â
fb
â
1
, collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are
B
(
B
0
â
J
/
Ï
p
ÂŻ
p
)
=
[
4.51
±
0.40
(
stat
)
±
0.44
(
syst
)
]
Ă
10
â
7
,
B
(
B
0
s
â
J
/
Ï
p
ÂŻ
p
)
=
[
3.58
±
0.19
(
stat
)
±
0.39
(
syst
)
]
Ă
10
â
6
. For the
B
0
s
meson, the result is much higher than the expected value of
O
(
10
â
9
)
. The small available phase space in these decays also allows for the most precise single measurement of both the
B
0
mass as
5279.74
±
0.30
(
stat
)
±
0.10
(
syst
)
â
â
MeV
and the
B
0
s
mass as
5366.85
±
0.19
(
stat
)
±
0.13
(
syst
)
â
â
MeV
- âŠ