A
bstract
Production cross-sections of prompt charm mesons are measured with the first data from
pp
collisions at the LHC at a centre-of-mass energy of 13 TeV. The data sample corresponds to an ...integrated luminosity of 4.98 ± 0.19 pb
−1
collected by the LHCb experiment. The production cross-sections of
D
0
,
D
+
,
D
s
+
, and
D
*+
mesons are measured in bins of charm meson transverse momentum,
p
T
, and rapidity,
y
, and cover the range 0 <
p
T
< 15GeV/c and 2.0 <
y
< 4.5. The inclusive cross-sections for the four mesons, including charge conjugation, within the range of 1 <
p
T
< 8 GeV/c are found to be
σ
pp
→
D
0
X
=
2460
±
3
±
130
μ
b
σ
pp
→
D
+
X
=
1000
±
3
±
110
μ
b
σ
pp
→
D
s
+
X
=
460
±
13
±
100
μ
b
σ
pp
→
D
∗
+
X
=
880
±
5
±
140
μ
b
where the uncertainties are due to statistical and systematic uncertainties, respectively.
The first full amplitude analysis of B+→J/ψϕK+ with J/ψ→μ+μ−, ϕ→K+K− decays is performed with a data sample of 3 fb−1 of pp collision data collected at s=7 and 8 TeV with the LHCb detector. The data ...cannot be described by a model that contains only excited kaon states decaying into ϕK+, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the K*(1680)+→ϕK+ transition.
The Dalitz plot analysis technique is used to study the resonant substructures of B−→D+π−π− decays in a data sample corresponding to 3.0 fb−1 of pp collision data recorded by the LHCb experiment ...during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D+π− mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D+π− S wave together with virtual contributions from the D*(2007)0 and B*0 states, and components corresponding to the D2*(2460)0, D1*(2680)0, D3*(2760)0 and D2*(3000)0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B−→D+π−π− decays. The D+π− S wave has phase motion consistent with that expected due to the presence of the D0*(2400)0 state. These results constitute the first observations of the D3*(2760)0 and D2*(3000)0 resonances, with significances of 10σ and 6.6σ, respectively.
Performance of the LHCb RICH detector at the LHC Adinolfi, M.; Aglieri Rinella, G.; Albrecht, E. ...
The European physical journal. C, Particles and fields,
05/2013, Letnik:
73, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The LHCb experiment has been taking data at the Large Hadron Collider (LHC) at CERN since the end of 2009. One of its key detector components is the Ring-Imaging Cherenkov (RICH) system. This ...provides charged particle identification over a wide momentum range, from 2–100 GeV/
c
. The operation and control, software, and online monitoring of the RICH system are described. The particle identification performance is presented, as measured using data from the LHC. Excellent separation of hadronic particle types (
π
, K, p) is achieved.
The B 0 s π ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to ...3 fb − 1 of p p collision data at √ s = 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X ( 5568 ) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B 0 s π ± final state. The same limits also apply to a possible exotic meson decaying through the chain B * 0 s π ± , B * 0 s → B 0 s γ where the photon is excluded from the reconstructed decays.
Two-particle angular correlations are studied in proton-lead collisions at a nucleon–nucleon centre-of-mass energy of sNN=5 TeV, collected with the LHCb detector at the LHC. The analysis is based on ...data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, Δη, and relative azimuthal angle, Δϕ, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, Δϕ≈0, is observed in the pseudorapidity range 2.0<η<4.9. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to η=4.9. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.
A search for heavy Majorana neutrinos produced in the B- → π+ μ- μ- decay mode is performed using 3 fb(-1) of integrated luminosity collected with the LHCb detector in pp collisions at ...center-of-mass energies of 7 and 8 TeV at the LHC. Neutrinos with masses in the range 250 to 5000 MeV and lifetimes from zero to 1000 ps are probed. In the absence of a signal, upper limits are set on the branching fraction B(B- → π+ μ- μ-) as functions of neutrino mass and lifetime. These limits are on the order of 10(-9) for short neutrino lifetimes of 1 ps or less. Limits are also set on the coupling between the muon and a possible fourth-generation neutrino.
The production of J/ψ mesons in proton–proton collisions at √s = 7 TeV is studied with the LHCb detector at the LHC. The differential cross-section for prompt J/ψ production is measured as a function ...of the J/ψ transverse
momentum pT and rapidity y in the fiducial region pT ∈ 0; 14 GeV/c and y ∈ 2.0; 4.5. The differential cross-section and fraction of J/ψ from b-hadron decays are also measured in the same pT and y ranges. The analysis is based on a data sample corresponding to an integrated luminosity of 5.2 pb−1. The measured cross-sections integrated over the fiducial region are 10.52 ± 0.04 ± 1.40+1.64 −2.20 µb for prompt J/ψ production and 1.14 ± 0.01 ± 0.16 µb for J/ψ from b-hadron decays, where the first uncertainty is statistical and the second systematic. The prompt J/ψ production cross-section is obtained assuming no J/ψ polarisation and the third error indicates the acceptance uncertainty due to this assumption.
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