A
bstract
The first observation of the
$$ {\Lambda}_b^0\to {D}_s^{-}p $$
Λ
b
0
→
D
s
−
p
decay is presented using proton-proton collision data collected by the LHCb experiment at a centre-of-mass ...energy of
$$ \sqrt{s} $$
s
= 13 TeV, corresponding to a total integrated luminosity of 6 fb
−
1
. Using the
$$ {\Lambda}_b^0\to {\Lambda}_c^{+}{\pi}^{-} $$
Λ
b
0
→
Λ
c
+
π
−
decay as the normalisation mode, the branching fraction of the
$$ {\Lambda}_b^0\to {D}_s^{-}p $$
Λ
b
0
→
D
s
−
p
decay is measured to be
$$ \mathcal{B}\left({\Lambda}_b^0\to {D}_s^{-}p\right)=\left(12.6\pm 0.5\pm 0.3\pm 1.2\right)\times {10}^{-6} $$
B
Λ
b
0
→
D
s
−
p
=
12.6
±
0.5
±
0.3
±
1.2
×
10
−
6
, where the first uncertainty is statistical, the second systematic and the third due to uncertainties in the branching fractions of the
$$ {\Lambda}_b^0\to {\Lambda}_c^{+}{\pi}^{-} $$
Λ
b
0
→
Λ
c
+
π
−
,
$$ {D}_s^{-}\to {K}^{-}{K}^{+}{\pi}^{-} $$
D
s
−
→
K
−
K
+
π
−
and
$$ {\Lambda}_c^{+}\to p{K}^{-}{\pi}^{+} $$
Λ
c
+
→
p
K
−
π
+
decays.
Asymmetries in the time-dependent rates of D-0 -> K+K- and D-0 -> pi(+)pi(-)decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an ...integrated luminosity of 3 fb(-1). The asymmetries in effective decay widths between D-0 and (D) over bar (0) decays, sensitive to indirect CP violation, are measured to be A(r)(K+K-) = (-0.30 +/- 0.32 0.10) x 10(-3) and A(r) pi(+)pi(-)) = (0.46 +/- 0.58 +/- 0.12) x 10(-3), where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.
An angular analysis of B0 → J / ψ K+ π− decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected with the LHCb detector. The m (K+ π−) ...spectrum is divided into fine bins. In each m(K+ π−) bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by K* resonances is examined, making minimal assumptions about the K+ π− system. The data reject the K*-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the m(J / ψπ−) vs m(K+ π−) plane suggests structures near m(J / ψπ−) = 4200 and 4600 MeV.
A search for the flavor-changing neutral-current decay Λc+→pμ+μ− is reported using a data set corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb Collaboration. No significant ...signal is observed outside of the dimuon mass regions around the ϕ and ω resonances, and an upper limit is placed on the branching fraction of B(Λc+→pμ+μ−)<7.7(9.6)×10−8 at 90%(95%) confidence level. A significant signal is observed in the ω dimuon mass region for the first time.
The ratio of the B0s and B+ fragmentation fractions fs and fu is studied with B0s → J/ψ ϕ and B+ → J/ψK+ decays using data collected by the LHCb experiment in proton-proton collisions at 7, 8, and 13 ...TeV center-of-mass energies. The analysis is performed in bins of B -meson momentum, longitudinal momentum, transverse momentum, pseudorapidity, and rapidity. The fragmentation-fraction ratio fs/fu is observed to depend on the B -meson transverse momentum with a significance of 6.0σ . This dependency is driven by the 13 TeV sample (8.7σ), while the results for the other collision energies are not significant when considered separately. Furthermore, the results show a 4.8σ evidence for an increase of fs/fu as a function of collision energy.
Mesons comprising a beauty quark and strange quark can oscillate between particle (B-s(0)) and antiparticle (B-s(-0)) flavour eigenstates, with a frequency given by the mass difference between heavy ...and light mass eigenstates, Delta m(s). Here we present a measurement of Delta m(s) using B-s(0) -> D-s(-)pi(+) decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Delta m(s) = 17.7683 +/- 0.0051 +/- 0.0032 ps(-1), where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Delta m(s) precision by a factor of two. We combine this result with previous LHCb measurements to determine Delta m(s) = 17.7656 +/- 0.0057 ps(-1), which is the legacy measurement of the original LHCb detector.
Resonant contributions in B0 & RARR; over bar D0D+s & pi;- and B+ & RARR; D-D+s & pi;+ decays are determined with an amplitude analysis, which is performed both separately and ...simultaneously, where in the latter case isospin symmetry between the decays is assumed. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV. The full data sample corresponds to an integrated luminosity of 9 fb-1. A doubly charged spin-0 open-charm tetraquark candidate together with a neutral partner, both with masses near 2.9 GeV, are observed in the Ds & pi; decay channel.
A time-dependent analysis of the Bs0→ϕγ decay rate is performed to determine the CP -violating observables Sϕγ and Cϕγ and the mixing-induced observable AϕγΔ. The measurement is based on a sample of ...pp collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3 fb−1 at center-of-mass energies of 7 and 8 TeV. The measured values are Sϕγ=0.43±0.30±0.11, Cϕγ=0.11±0.29±0.11, and AϕγΔ=−0.67−0.41+0.37±0.17, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables S and C in radiative Bs0 decays. The results are consistent with the standard model predictions.
The production of charged hadrons within jets recoiling against a Z boson is measured in proton-proton collision data at √s = 8 TeV recorded by the LHCb experiment. The charged-hadron structure of ...the jet is studied longitudinally and transverse to the jet axis for jets with transverse momentum pT > 20 GeV and in the pseudorapidity range 2.5 < η < 4. These are the first measurements of jet hadronization at these forward rapidities and also the first where the jet is produced in association with a Z boson. In contrast to previous hadronization measurements at the Large Hadron Collider, which are dominated by gluon jets, these measurements probe predominantly light-quark jets which are found to be more longitudinally and transversely collimated with respect to the jet axis when compared to the previous gluon dominated measurements. Therefore, these results provide valuable information on differences between quarks and gluons regarding nonperturbative hadronization dynamics.
A
bstract
The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at ...a centre-of-mass energy of
s
= 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5
.
4 nb
−
1
. The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges
p
T
∈ 80
,
10 000) MeV
/c
and
η
∈ 2
.
0
,
4
.
8) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
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