A measurement of the phase difference between the short- and long-distance contributions to the Formula: see text decay is performed by analysing the dimuon mass distribution. The analysis is based ...on
collision data corresponding to an integrated luminosity of 3Formula: see text collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the Formula: see text decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the Formula: see text and Formula: see text resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, Formula: see text and Formula: see text, and the branching fraction of the short-distance component is measured.
The production of B+, B0 and Λb0 hadrons is studied in proton-lead collisions at a center-of-mass energy per nucleon pair of sNN=8.16 TeV recorded with the LHCb detector at the LHC. The measurement ...uses a dataset corresponding to an integrated luminosity of 12.2±0.3 nb−1 for the case where the proton beam is projected into the LHCb detector (corresponding to measuring hadron production at positive rapidity) and 18.6±0.5 nb−1 for the lead beam projected into the LHCb detector (corresponding to measuring hadron production at negative rapidity). Double-differential cross sections are measured and used to determine forward-backward ratios and nuclear modification factors, which directly probe nuclear effects in the production of beauty hadrons. The double-differential cross sections are measured as a function of the beauty-hadron transverse momentum and rapidity in the nucleon-nucleon center-of-mass frame. Forward-to-backward cross section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity. The ratio of Λb0 over B0 production cross sections is reported and is consistent with the corresponding measurement in pp collisions.
We report a measurement of the lifetime of the Ωc0 baryon using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb−1 ...collected by the LHCb experiment. The sample consists of about 1000 Ωb−→Ωc0μ−ν¯μX signal decays, where the Ωc0 baryon is detected in the pK−K−π+ final state and X represents possible additional undetected particles in the decay. The Ωc0 lifetime is measured to be τΩc0=268±24±10±2 fs, where the uncertainties are statistical, systematic, and from the uncertainty in the D+ lifetime, respectively. This value is nearly four times larger than, and inconsistent with, the current world-average value.
Evidence for the decay X(3872)→ψ(2S)γ Ajaltouni, Z.; An, L.; Andreotti, M. ...
Nuclear physics. B,
09/2014, Letnik:
886, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Evidence for the decay mode X(3872)→ψ(2S)γ in B+→X(3872)K+ decays is found with a significance of 4.4 standard deviations. The analysis is based on a data sample of proton–proton collisions, ...corresponding to an integrated luminosity of 3 fb−1, collected with the LHCb detector, at centre-of-mass energies of 7 and 8 TeV. The ratio of the branching fraction of the X(3872)→ψ(2S)γ decay to that of the X(3872)→J/ψγ decay is measured to beB(X(3872)→ψ(2S)γ)B(X(3872)→J/ψγ)=2.46±0.64±0.29, where the first uncertainty is statistical and the second is systematic. The measured value does not support a pure DD¯⁎ molecular interpretation of the X(3872) state.
We report measurements of the lifetimes of the Λc+, Ξc+ and Ξc0 charm baryons using proton-proton collision data at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity ...of 3.0 fb−1, collected by the LHCb experiment. The charm baryons are reconstructed through the decays Λc+→pK−π+, Ξc+→pK−π+ and Ξc0→pK−K−π+, and originate from semimuonic decays of beauty baryons. The lifetimes are measured relative to that of the D+ meson, and are determined to be τΛc+=203.5±1.0±1.3±1.4 fs, τΞc+=456.8±3.5±2.9±3.1 fs, τΞc0=154.5±1.7±1.6±1.0 fs, where the uncertainties are statistical, systematic, and due to the uncertainty in the D+ lifetime. The measurements are approximately 3–4 times more precise than the current world average values. The Λc+ and Ξc+ lifetimes are in agreement with previous measurements; however, the Ξc0 baryon lifetime is approximately 3.3 standard deviations larger than the world average value.
Using pp collision data corresponding to an integrated luminosity of 5.4 fb−1 collected with the LHCb detector at a center-of-mass energy of 13 TeV, the B0 → D−D+K+π− decay is studied. A new excited ...Ds+ meson is observed decaying into the D+K+π− final state with large statistical significance. The pole mass and width, and the spin parity of the new state are measured with an amplitude analysis to be mR = 2591 ± 6 ± 7 MeV, ΓR = 89 ± 16 ± 12 MeV, and JP = 0−, where the first uncertainty is statistical and the second systematic. Fit fractions for all components in the amplitude analysis are also reported. The new resonance, denoted as Ds0(2590)+, is a strong candidate to be the Ds(21S0)+ state, the radial excitation of the pseudoscalar ground-state Ds+ meson.
The production fraction of the Bc− meson with respect to the sum of B− and B¯0 mesons is measured in both 7 and 13 TeV center-of-mass (c.m.) energy pp collisions produced by the Large Hadron Collider ...(LHC), using the LHCb detector. The rate, approximately 3.7 per mille, does not change with energy, but shows a transverse momentum dependence. The Bc−−Bc+ production asymmetry is also measured and is consistent with zero within the determined statistical and systematic uncertainties of a few percent.
The radiative decay Λb0→Λγ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of 1.7 fb−1 collected by the LHCb experiment at a ...center-of-mass energy of 13 TeV. Its branching fraction is measured exploiting the B0→K*0γ decay as a normalization mode and is found to be B(Λb0→Λγ)=(7.1±1.5±0.6±0.7)×10−6, where the quoted uncertainties are statistical, systematic, and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.
The production of the
η
c
(
1
S
)
state in proton-proton collisions is probed via its decay to the
p
p
¯
final state with the LHCb detector, in the rapidity range
2.0
<
y
<
4.5
and in the meson ...transverse-momentum range
p
T
>
6.5
GeV
/
c
. The cross-section for prompt production of
η
c
(
1
S
)
mesons relative to the prompt
J
/
ψ
cross-section is measured, for the first time, to be
σ
η
c
(
1
S
)
/
σ
J
/
ψ
=
1.74
±
0.29
±
0.28
±
0
.
18
B
at a centre-of-mass energy
s
=
7
TeV
using data corresponding to an integrated luminosity of 0.7 fb
-
1
, and
σ
η
c
(
1
S
)
/
σ
J
/
ψ
=
1.60
±
0.29
±
0.25
±
0
.
17
B
at
s
=
8
TeV
using 2.0 fb
-
1
. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the
η
c
(
1
S
)
and
J
/
ψ
decays to the
p
p
¯
final state. In addition, the inclusive branching fraction of
b
-hadron decays into
η
c
(
1
S
)
mesons is measured, for the first time, to be
B
(
b
→
η
c
X
)
=
(
4.88
±
0.64
±
0.29
±
0
.
67
B
)
×
10
-
3
, where the third uncertainty includes also the uncertainty on the
J
/
ψ
inclusive branching fraction from
b
-hadron decays. The difference between the
J
/
ψ
and
η
c
(
1
S
)
meson masses is determined to be
114.7
±
1.5
±
0.1
MeV
/
c
2
.
A search for CP violation in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays is performed using pp collision data, corresponding to an integrated luminosity of 3 fb(-1), collected using the LHCb detector at ...center-of-mass energies of 7 and 8 TeV. The flavor of the charm meson is inferred from the charge of the pion in D*(+) -> D-0 pi(+) and D*(-) -> (D) over bar (0)pi(-) decays. The difference between the CP asymmetries in D-0 -> K-K+ and D-0 -> pi(-)pi(+) decays, Delta A(CP) A(CP)(K-K+) - A(CP)(pi(-)pi(+)), is measured to be -0.10 +/- 0.08(stat) +/- 0.03(syst)%. This is the most precise measurement of a time-integrated CP asymmetry in the charm sector from a single experiment.
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