Observation of the Ξb−→J/ψΛK− decay An, L.; Arnau Romeu, J.; Artamonov, A. ...
Physics letters. B,
09/2017, Letnik:
772, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The observation of the decay Ξb−→J/ψΛK− is reported, using a data sample corresponding to an integrated luminosity of 3fb−1, collected by the LHCb detector in pp collisions at centre-of-mass energies ...of 7 and 8TeV. The production rate of Ξb− baryons detected in the decay Ξb−→J/ψΛK− is measured relative to that of Λb0 baryons using the decay Λb0→J/ψΛ. Integrated over the b-baryon transverse momentum pT<25GeV/c and rapidity 2.0<y<4.5, the measured ratio isfΞb−fΛb0B(Ξb−→J/ψΛK−)B(Λb0→J/ψΛ)=(4.19±0.29 (stat)±0.15 (syst))×10−2, where fΞb− and fΛb0 are the fragmentation fractions of b→Ξb− and b→Λb0 transitions, and B represents the branching fraction of the corresponding b-baryon decay. The mass difference between Ξb− and Λb0 baryons is measured to beM(Ξb−)−M(Λb0)=177.08±0.47 (stat)±0.16 (syst)MeV/c2.
The production of tt‾, W+bb‾ and W+cc‾ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an ...integrated luminosity of 1.98±0.02 fb−1. The W bosons are reconstructed in the decays W→ℓν, where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.
Measurements of CP observables in B±→D(⁎)K± and B±→D(⁎)π± decays are presented, where D(⁎) indicates a neutral D or D⁎ meson that is an admixture of D(⁎)0 and D¯(⁎)0 states. Decays of the D⁎ meson to ...the Dπ0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the B candidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K±π∓, K+K− and π+π− final states. The analysis uses a sample of charged B mesons produced in pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb−1 taken at centre-of-mass energies of s=7, 8 and 13 TeV, respectively. The study of B±→D⁎K± and B±→D⁎π± decays using a partial reconstruction method is the first of its kind, while the measurement of B±→DK± and B±→Dπ± decays is an update of previous LHCb measurements. The B±→DK± results are the most precise to date.
Search for the decay B 0 → ϕμ + μ Aaij, R.; Eklund, Lars; Zunica, G.
The journal of high energy physics,
05/2022, Letnik:
2022, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A search for the decay B-0 -> phi mu(+) mu(-) 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 -> phi mu(+) mu(-) decay is found and an upper limit on the branching fraction, excluding the 0 and charmonium regions in the dimuon spectrum, of 4.4 x 10(-3) at a 90% credibility level, relative to that of the B-s(0) -> phi mu(+) mu(-) decay, is established. Using the measured B-s(0) -> phi mu(+) mu(-) branching fraction and assuming a phase-space model, the absolute branching fraction of the decay B-0 -> phi mu(+) mu(-) in the full q(2) range is determined to be less than 3.2 x 10(-9) at a 90% credibility level.
A
bstract
The resonant structure of the doubly Cabibbo-suppressed decay
D
+
→
K
−
K
+
K
+
is studied for the first time. The measurement is based on a sample of
pp
-collision data, collected at a ...centre-of-mass energy of 8 TeV with the LHCb detector and corresponding to an integrated luminosity of 2 fb
−1
. The amplitude analysis of this decay is performed with the isobar model and a phenomenological model based on an effective chiral Lagrangian. In both models the S-wave component in the
K
−
K
+
system is dominant, with a small contribution of the
ϕ
(1020) meson and a negligible contribution from tensor resonances. The
K
+
K
−
scattering amplitudes for the considered combinations of spin (0,1) and isospin (0,1) of the two-body system are obtained from the Dalitz plot fit with the phenomenological decay amplitude.
A search for decays of Bc+ mesons to two charm mesons is performed for the first time using data corresponding to an integrated luminosity of 3.0fb−1, collected by the LHCb experiment in pp ...collisions at centre-of-mass energies of 7 and 8 TeV. The decays considered are Bc+→D(s)(⁎)+D‾(⁎)0 and Bc+→D(s)(⁎)+D(⁎)0, which are normalised to high-yield B+→D(s)+D‾0 decays. No evidence for a signal is found and limits are set on twelve Bc+ decay modes.
A search is presented for a Higgs-like boson with mass in the range 45 to 195
GeV
/
c
2
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
/
c
2
to 4
pb
for a mass of 195
GeV
/
c
2
.
A
bstract
This article presents differential measurements of the asymmetry between
$$ {\varLambda}_b^0 $$
Λ
b
0
and
$$ {\overline{\varLambda}}_b^0 $$
Λ
¯
b
0
baryon production rates in proton-proton ...collisions at centre-of-mass energies of
$$ \sqrt{s} $$
s
= 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb
−
1
. The
$$ {\varLambda}_b^0 $$
Λ
b
0
baryons are reconstructed through the inclusive semileptonic decay
$$ {\varLambda}_b^0 $$
Λ
b
0
→
$$ {\varLambda}_c^{+} $$
Λ
c
+
μ
−
$$ \overline{\nu} $$
ν
¯
μ
X
. The production asymmetry is measured both in intervals of rapidity in the range 2
.
15
< y <
4
.
10 and transverse momentum in 2
< p
T
<
27 GeV/
c
. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both
$$ \sqrt{s} $$
s
= 7 and 8 TeV data, assuming no
CP
violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in P
ythia
and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in
b
-hadron production at LHC energies.
The Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected by the LHCb detector, corresponding to an ...integrated luminosity of 3fb−1. The ratio of branching fractions between the Λb0→Λc+K+K−π− and the Λb0→Λc+Ds− decays is measured to beB(Λb0→Λc+K+K−π−)B(Λb0→Λc+Ds−)=(9.26±0.29±0.46±0.26)×10−2, where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the Ds−→K+K−π− branching fraction. No structure on the invariant mass distribution of the Λc+K+ system is found, consistent with no open-charm pentaquark signature.
Abstract A flavour-tagged time-dependent angular analysis of $${{B} ^0_{s}} \!\rightarrow {{J /\psi }} \phi $$ B s 0 → J / ψ ϕ decays is presented where the $${J /\psi }$$ J / ψ meson is ...reconstructed through its decay to an $$e ^+e ^-$$ e + e - pair. The analysis uses a sample of pp collision data recorded with the LHCb experiment at centre-of-mass energies of 7 and $$8\text {\,Te V} $$ 8 \,Te V , corresponding to an integrated luminosity of $$3 \text {\,fb} ^{-1} $$ 3 \,fb - 1 . The $$C\!P$$ C P -violating phase and lifetime parameters of the $${B} ^0_{s} $$ B s 0 system are measured to be $${\phi _{{s}}} =0.00\pm 0.28\pm 0.07\text {\,rad}$$ ϕ s = 0.00 ± 0.28 ± 0.07 \,rad , $${\Delta \Gamma _{{s}}} =0.115\pm 0.045\pm 0.011\text {\,ps} ^{-1} $$ Δ Γ s = 0.115 ± 0.045 ± 0.011 \,ps - 1 and $${\Gamma _{{s}}} =0.608\pm 0.018\pm 0.012\text {\,ps} ^{-1} $$ Γ s = 0.608 ± 0.018 ± 0.012 \,ps - 1 where the first uncertainty is statistical and the second systematic. This is the first time that $$C\!P$$ C P -violating parameters are measured in the $${{B} ^0_{s}} \!\rightarrow {{J /\psi }} \phi $$ B s 0 → J / ψ ϕ decay with an $$e ^+e ^-$$ e + e - pair in the final state. The results are consistent with previous measurements in other channels and with the Standard Model predictions.
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