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 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.
Precision measurement of the Bc+ meson mass Alexander, M.; Alkhazov, G.; Aslanides, E. ...
The journal of high energy physics,
07/2020, Letnik:
2020, Številka:
7
Journal Article
Recenzirano
Odprti dostop
A
bstract
A precision measurement of the
B
c
+
meson mass is performed using proton- proton collision data collected with the LHCb experiment at centre-of-mass energies of 7
,
8 and 13 TeV, ...corresponding to a total integrated luminosity of 9
.
0 fb
−
1
. The
B
c
+
mesons are reconstructed via the decays
B
c
+
→ J/ψπ
+
,
B
c
+
→ J/ψπ
+
π
−
π
+
,
B
c
+
→
J
/
ψp
p
¯
π
+
,
B
c
+
→
J
/
ψ
D
s
+
,
B
c
+
→ J/ψ D
0
K
+
and
B
c
+
→
B
s
0
π
+
. Combining the results of the individual decay channels, the
B
c
+
mass is measured to be 6274
.
47
±
0
.
27 (stat)
±
0
.
17 (syst) MeV
/c
2
. This is the most precise measurement of the
B
c
+
mass to date. The difference between the
B
c
+
and
B
s
0
meson masses is measured to be 907
.
75
±
0
.
37 (stat)
±
0
.
27 (syst) MeV
/c
.
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.
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 time-dependent CP asymmetries in B0→π+π− and Bs0→K+K− decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0 fb−1, collected with the LHCb ...detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π− and Bs0→π+K− decays. The results are Cπ+π−=−0.34±0.06±0.01, Sπ+π−=−0.63±0.05±0.01, CK+K−=0.20±0.06±0.02, SK+K−=0.18±0.06±0.02, AK+K−ΔΓ=−0.79±0.07±0.10, ACPB0=−0.084±0.004±0.003, and ACPBs0=0.213±0.015±0.007, where the first uncertainties are statistical and the second systematic. Evidence for CP violation is found in the Bs0→K+K− decay for the first time.
A simultaneous analysis of the B thorn & RARR; K thorn e thorn e- and B0 & RARR; K & DBLBOND;0e thorn e- decays is performed to test muonelectron universality in two ranges of the square ...of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. 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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