First experience and results with the LHCb Silicon Tracker Fave, V.; Bay, A.; Blanc, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2010, Letnik:
617, Številka:
1
Journal Article
Recenzirano
The LHCb experiment is designed to perform high-precision measurements of CP violation and rare decays of b hadrons. The construction and installation of the Silicon Tracker (ST) was completed by the ...summer of 2008. Here, we report on first results obtained using the data taken during injection tests (‘TED’ run) in August and September 2008.
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.
The difference in total widths between the Bc+ and B+ mesons is measured using a data sample corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment in 7 and 8 TeV ...centre-of-mass energy proton–proton collisions at the LHC. Through the study of the time evolution of Bc+→J/ψπ+ and B+→J/ψK+ decays, the width difference is measured to beΔΓ≡ΓBc+−ΓB+=4.46±0.14±0.07 mm−1c, where the first uncertainty is statistical and the second systematic. The known lifetime of the B+ meson is used to convert this to a precise measurement of the Bc+ lifetime,τBc+=513.4±11.0±5.7 fs, where the first uncertainty is statistical and the second is systematic.
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 search for the rare decays Bs0→π+π−μ+μ− and B0→π+π−μ+μ− is performed in a data set corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb detector in proton–proton collisions ...at centre-of-mass energies of 7 and 8 TeV. Decay candidates with pion pairs that have invariant mass in the range 0.5–1.3 GeV/c2 and with muon pairs that do not originate from a resonance are considered. The first observation of the decay Bs0→π+π−μ+μ− and the first evidence of the decay B0→π+π−μ+μ− are obtained and the branching fractions, restricted to the dipion-mass range considered, are measured to be B(Bs0→π+π−μ+μ−)=(8.6±1.5 (stat)±0.7 (syst)±0.7(norm))×10−8 and B(B0→π+π−μ+μ−)=(2.11±0.51(stat)±0.15(syst)±0.16(norm))×10−8, where the third uncertainty is due to the branching fraction of the decay B0→J/ψ(→μ+μ−)K⁎(892)0(→K+π−), used as a normalisation.
A model-dependent amplitude analysis of B±→DK± with D→KS0π+π− decays is performed using proton–proton collision data, corresponding to an integrated luminosity of 1 fb−1, recorded by LHCb at a ...centre-of-mass energy of 7 TeV in 2011. Values of the CP violation observables x± and y±, which are sensitive to the CKM angle γ, are measured to bex−=+0.027±0.044−0.008+0.010±0.001,y−=+0.013±0.048−0.007+0.009±0.003,x+=−0.084±0.045±0.009±0.005,y+=−0.032±0.048−0.009+0.010±0.008, where the first uncertainty is statistical, the second systematic and the third arises from the uncertainty of the D→KS0π+π− amplitude model. The value of γ is determined to be (84−42+49)°, including all sources of uncertainty. Neutral D meson mixing is found to have negligible effect.
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.
LHCb Silicon Tracker DAQ and ECS Online Systems Esperante, Daniel; Rodriguez, P; Buchler, A ...
IEEE transactions on nuclear science,
2010-April, 2010-04-00, 20100401, Letnik:
57, Številka:
2
Journal Article
Recenzirano
The LHCb experiment at CERN is designed to perform precision measurements of b quark decays. The Silicon Tracker plays a crucial role in reconstructing particle trajectories and consists of two ...silicon micro-strip detectors, the Tracker Turicensis and the Inner Tracker. The radiation environment and the magnetic field represent new challenges for the implementation of the Experiment Control System (ECS) and the data acquisition (DAQ). The DAQ has to deal with ~272 000 analog read-out channels and real-time DAQ at a rate of ~ 1.1 MHz with data processing at the Trigger Electronics and L1 (TELL1) board level. The TELL1 real-time algorithms for clustering thresholds and other computations run on dedicated FPGAs. After data processing the total throughput amounts to about 6.4 GB from an input data rate of ~ 337 GB per second. The ECS is based on the hierarchical finite state machine paradigm and allows distributed control access and multi-platform use. The ECS is able to control and monitor the detector hardware infrastructure (power supplies, DAQ electronics ...) as well as monitor the environmental parameters. It can also take automated actions on warnings or alarms. Finally a completely independent, hardware based safety system ensures the detector safe operation.
Abstract A structure is observed in the $${B} ^{\pm }{K} ^{\mp }$$ B ± K ∓ mass spectrum in a sample of proton–proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the ...LHCb detector and corresponding to a total integrated luminosity of 9 $$\,\text {fb} ^{-1}$$ fb - 1 . The structure is interpreted as the result of overlapping excited $${B} ^0_{s} $$ B s 0 states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to $${B} ^{\pm }{K} ^{\mp }$$ B ± K ∓ , are determined to be $$\begin{aligned} m_1&= 6063.5 \pm 1.2 \text { (stat)} \pm 0.8\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _1&= 26 \pm 4 \text { (stat)} \pm 4\text { (syst)}\,\text {Me}\text {V}, \\ m_2&= 6114 \pm 3 \text { (stat)} \pm 5\text { (syst)}\,\text {Me}\text {V}, \\ \Gamma _2&= 66 \pm 18 \text { (stat)} \pm 21\text { (syst)}\,\text {Me}\text {V}. \end{aligned}$$ m 1 = 6063.5 ± 1.2 (stat) ± 0.8 (syst) Me , Γ 1 = 26 ± 4 (stat) ± 4 (syst) Me , m 2 = 6114 ± 3 (stat) ± 5 (syst) Me , Γ 2 = 66 ± 18 (stat) ± 21 (syst) Me . Alternative values assuming a decay through $${B} ^{*\pm }{K} ^{\mp }$$ B ∗ ± K ∓ , with a missing photon from the $$B^{*\pm } \rightarrow B^{\pm }\gamma $$ B ∗ ± → B ± γ decay, which are shifted by approximately 45 $$\,\text {Me}$$ Me V, are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed $$B_{s2}^{*0}$$ B s 2 ∗ 0 state is determined to be $$0.87 \pm 0.15 \text { (stat)} \pm 0.19 \text { (syst)}$$ 0.87 ± 0.15 (stat) ± 0.19 (syst) .
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