128 research outputs found

    DPU-ASW Management of the DCU ERROR REG content with possible off-line recovery actions

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    A new strategy is defined for the management of the errors in the DCU science interface dedicated to the scientific data acquisitio

    First detection of X-ray polarization from the accreting neutron star 4U 1820-303

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    This paper reports the first detection of polarization in the X-rays for atoll-source 4U 1820-303, obtained with the Imaging X-ray Polarimetry Explorer (IXPE) at 99.999% confidence level (CL). Simultaneous polarimetric measurements were also performed in the radio with the Australia Telescope Compact Array (ATCA). The IXPE observations of 4U 1820-303 were coordinated with Swift-XRT, NICER, and NuSTAR aiming to obtain an accurate X-ray spectral model covering a broad energy interval. The source shows a significant polarization above 4 keV, with a polarization degree of 2.0(0.5)% and a polarization angle of -55(7) deg in the 4-7 keV energy range, and a polarization degree of 10(2)% and a polarization angle of -67(7) deg in the 7-8 keV energy bin. This polarization also shows a clear energy trend with polarization degree increasing with energy and a hint for a position-angle change of about 90 deg at 96% CL around 4 keV. The spectro-polarimetric fit indicates that the accretion disk is polarized orthogonally to the hard spectral component, which is presumably produced in the boundary/spreading layer. We do not detect linear polarization from the radio counterpart, with a 99.97% upper limit of 50% at 7.25 GHz

    Studies of beauty baryon decays to D0ph− and Λ+ch− final states

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    Measurement of the (eta c)(1S) production cross-section in proton-proton collisions via the decay (eta c)(1S) -> p(p)over-bar

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    Observation of the B0 → ρ0ρ0 decay from an amplitude analysis of B0 → (π+π−)(π+π−) decays

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    Proton–proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb−1 , are analysed to search for the charmless B0→ρ0ρ0 decay. More than 600 B0→(π+π−)(π+π−) signal decays are selected and used to perform an amplitude analysis, under the assumption of no CP violation in the decay, from which the B0→ρ0ρ0 decay is observed for the first time with 7.1 standard deviations significance. The fraction of B0→ρ0ρ0 decays yielding a longitudinally polarised final state is measured to be fL=0.745−0.058+0.048(stat)±0.034(syst) . The B0→ρ0ρ0 branching fraction, using the B0→ϕK⁎(892)0 decay as reference, is also reported as B(B0→ρ0ρ0)=(0.94±0.17(stat)±0.09(syst)±0.06(BF))×10−6

    Search for CP violation using T-odd correlations in D-0 -> K+K-pi(+)pi(-) decays

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    A search for CPCP violation using TT-odd correlations is performed using the four-body D0K+Kπ+πD^0 \to K^+K^-\pi^+\pi^- decay, selected from semileptonic BB decays. The data sample corresponds to integrated luminosities of 1.0fb11.0\,\text{fb}^{-1} and 2.0fb12.0\,\text{fb}^{-1} recorded at the centre-of-mass energies of 7 TeV and 8 TeV, respectively. The CPCP-violating asymmetry aCPT-odda_{CP}^{T\text{-odd}} is measured to be (0.18±0.29(stat)±0.04(syst))%(0.18\pm 0.29\text{(stat)}\pm 0.04\text{(syst)})\%. Searches for CPCP violation in different regions of phase space of the four-body decay, and as a function of the D0D^0 decay time, are also presented. No significant deviation from the CPCP conservation hypothesis is found

    Measurement of CP asymmetry in B-s(0) -> D-s(-/+) K--/+ decays

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    We report on measurements of the time-dependent CP violating observables in Bs0DsK±B^0_s\rightarrow D^{\mp}_s K^{\pm} decays using a dataset corresponding to 1.0 fb1^{-1} of pp collisions recorded with the LHCb detector. We find the CP violating observables Cf=0.53±0.25±0.04C_f=0.53\pm0.25\pm0.04, AfΔΓ=0.37±0.42±0.20A^{\Delta\Gamma}_f=0.37\pm0.42\pm0.20, AfˉΔΓ=0.20±0.41±0.20A^{\Delta\Gamma}_{\bar{f}}=0.20\pm0.41\pm0.20, Sf=1.09±0.33±0.08S_f=-1.09\pm0.33\pm0.08, Sfˉ=0.36±0.34±0.08S_{\bar{f}}=-0.36\pm0.34\pm0.08, where the uncertainties are statistical and systematic, respectively. We use these observables to make the first measurement of the CKM angle γ\gamma in Bs0DsK±B^0_s\rightarrow D^{\mp}_s K^{\pm} decays, finding γ\gamma = (11543+28_{-43}^{+28})^\circ modulo 180^\circ at 68% CL, where the error contains both statistical and systematic uncertainties.We report on measurements of the time-dependent CP violating observables in Bs0_{s}^{0}  → Ds_{s}^{∓} K±^{±} decays using a dataset corresponding to 1.0 fb1^{−1} of pp collisions recorded with the LHCb detector. We find the CP violating observables Cf_{f} = 0.53±0.25±0.04, AfΔΓ_{f}^{ΔΓ}  = 0.37 ± 0.42 ± 0.20, AfΔΓ=0.20±0.41±0.20 {A}_{\overline{f}}^{\varDelta \varGamma }=0.20\pm 0.41\pm 0.20 , Sf_{f} = −1.09±0.33±0.08, Sf=0.36±0.34±0.08 {S}_{\overline{f}}=-0.36\pm 0.34\pm 0.08 , where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the Bs0_{s}^{0} mixing phase −2βs_{s} leads to the first extraction of the CKM angle γ from Bs0_{s}^{0}  → Ds_{s}^{∓} K±^{±} decays, finding γ = (11543+28_{− 43}^{+ 28} )° modulo 180° at 68% CL, where the error contains both statistical and systematic uncertainties.We report on measurements of the time-dependent CP violating observables in Bs0DsK±B^0_s\rightarrow D^{\mp}_s K^{\pm} decays using a dataset corresponding to 1.0 fb1^{-1} of pp collisions recorded with the LHCb detector. We find the CP violating observables Cf=0.53±0.25±0.04C_f=0.53\pm0.25\pm0.04, AfΔΓ=0.37±0.42±0.20A^{\Delta\Gamma}_f=0.37\pm0.42\pm0.20, AfˉΔΓ=0.20±0.41±0.20A^{\Delta\Gamma}_{\bar{f}}=0.20\pm0.41\pm0.20, Sf=1.09±0.33±0.08S_f=-1.09\pm0.33\pm0.08, Sfˉ=0.36±0.34±0.08S_{\bar{f}}=-0.36\pm0.34\pm0.08, where the uncertainties are statistical and systematic, respectively. Using these observables together with a recent measurement of the Bs0B^0_s mixing phase 2βs-2\beta_s leads to the first extraction of the CKM angle γ\gamma from Bs0DsK±B^0_s \rightarrow D^{\mp}_s K^{\pm} decays, finding γ\gamma = (11543+28_{-43}^{+28})^\circ modulo 180^\circ at 68% CL, where the error contains both statistical and systematic uncertainties

    Angular analysis of the B-0 -> K*(0) e(+) e(-) decay in the low-q(2) region

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    An angular analysis of the B0K0e+eB^0 \rightarrow K^{*0} e^+ e^- decay is performed using a data sample, corresponding to an integrated luminosity of 3.0 {\mbox{fb}^{-1}}, collected by the LHCb experiment in pppp collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared (q2q^2) interval between 0.002 and 1.120GeV2 ⁣/c4{\mathrm{\,Ge\kern -0.1em V^2\!/}c^4}. The angular observables FLF_{\mathrm{L}} and ATReA_{\mathrm{T}}^{\mathrm{Re}} which are related to the K0K^{*0} polarisation and to the lepton forward-backward asymmetry, are measured to be FL=0.16±0.06±0.03F_{\mathrm{L}}= 0.16 \pm 0.06 \pm0.03 and ATRe=0.10±0.18±0.05A_{\mathrm{T}}^{\mathrm{Re}} = 0.10 \pm 0.18 \pm 0.05, where the first uncertainty is statistical and the second systematic. The angular observables AT(2)A_{\mathrm{T}}^{(2)} and ATImA_{\mathrm{T}}^{\mathrm{Im}} which are sensitive to the photon polarisation in this q2q^2 range, are found to be AT(2)=0.23±0.23±0.05A_{\mathrm{T}}^{(2)} = -0.23 \pm 0.23 \pm 0.05 and ATIm=0.14±0.22±0.05A_{\mathrm{T}}^{\mathrm{Im}} =0.14 \pm 0.22 \pm 0.05. The results are consistent with Standard Model predictions.An angular analysis of the B0^{0} → K^{*}^{0} e+^{+} e^{−} decay is performed using a data sample, corresponding to an integrated luminosity of 3.0 fb1^{−1}, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared (q2^{2}) interval between 0.002 and 1.120 GeV2^{2} /c4^{4}. The angular observables FL_{L} and ATRe_{T}^{Re} which are related to the K^{*}^{0} polarisation and to the lepton forward-backward asymmetry, are measured to be FL_{L} = 0.16 ± 0.06 ± 0.03 and ATRe_{T}^{Re}  = 0.10 ± 0.18 ± 0.05, where the first uncertainty is statistical and the second systematic. The angular observables AT(2)_{T}^{(2)} and ATIm_{T}^{Im} which are sensitive to the photon polarisation in this q2^{2} range, are found to be AT(2)_{T}^{(2)}  = − 0.23 ± 0.23 ± 0.05 and ATIm_{T}^{Im}  = 0.14 ± 0.22 ± 0.05. The results are consistent with Standard Model predictions.An angular analysis of the B0K0e+eB^0 \rightarrow K^{*0} e^+ e^- decay is performed using a data sample, corresponding to an integrated luminosity of 3.0 {\mbox{fb}^{-1}}, collected by the LHCb experiment in pppp collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared (q2q^2) interval between 0.002 and 1.120GeV2 ⁣/c4{\mathrm{\,Ge\kern -0.1em V^2\!/}c^4}. The angular observables FLF_{\mathrm{L}} and ATReA_{\mathrm{T}}^{\mathrm{Re}} which are related to the K0K^{*0} polarisation and to the lepton forward-backward asymmetry, are measured to be FL=0.16±0.06±0.03F_{\mathrm{L}}= 0.16 \pm 0.06 \pm0.03 and ATRe=0.10±0.18±0.05A_{\mathrm{T}}^{\mathrm{Re}} = 0.10 \pm 0.18 \pm 0.05, where the first uncertainty is statistical and the second systematic. The angular observables AT(2)A_{\mathrm{T}}^{(2)} and ATImA_{\mathrm{T}}^{\mathrm{Im}} which are sensitive to the photon polarisation in this q2q^2 range, are found to be AT(2)=0.23±0.23±0.05A_{\mathrm{T}}^{(2)} = -0.23 \pm 0.23 \pm 0.05 and ATIm=0.14±0.22±0.05A_{\mathrm{T}}^{\mathrm{Im}} =0.14 \pm 0.22 \pm 0.05. The results are consistent with Standard Model predictions

    Search for the lepton flavour violating decay tau(-) -> mu(-)mu(+)mu(-)

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    A search for the lepton flavour violating decay τμμ+μ\tau^-\rightarrow\mu^-\mu^+\mu^- is performed with the LHCb experiment. The data sample corresponds to an integrated luminosity of 1.0 fb1^{−1} of proton-proton collisions at a centre-of-mass energy of 7 TeV and 2.0 fb1^{−1} at 8 TeV. No evidence is found for a signal, and a limit is set at 90% confidence level on the branching fraction, B(τμμ+μ)<4.6×108\mathcal{B}(\tau^-\rightarrow\mu^-\mu^+\mu^-)<4.6\times10^{−8}.A search for the lepton flavour violating decay τ^{−} → μ^{−} μ+^{+} μ^{−} is performed with the LHCb experiment. The data sample corresponds to an integrated luminosity of 1.0 fb1^{−1} of proton-proton collisions at a centre-of-mass energy of 7 TeV and 2.0 fb1^{−1} at 8 TeV. No evidence is found for a signal, and a limit is set at 90% confidence level on the branching fraction, B(τμμ+μ)<4.6×108 \mathrm{\mathcal{B}}\left({\tau}^{-}\to {\mu}^{-}{\mu}^{+}{\mu}^{-}\right)<4.6\times {10}^{-8} .A search for the lepton flavour violating decay τμμ+μ\tau^-\to \mu^-\mu^+\mu^- is performed with the LHCb experiment. The data sample corresponds to an integrated luminosity of 1.0fb11.0\mathrm{\,fb}^{-1} of proton-proton collisions at a centre-of-mass energy of 7TeV7\mathrm{\,Te\kern -0.1em V} and 2.0fb12.0\mathrm{\,fb}^{-1} at 8TeV8\mathrm{\,Te\kern -0.1em V}. No evidence is found for a signal, and a limit is set at 90%90\% confidence level on the branching fraction, B(τμμ+μ)<4.6×108\mathcal{B}(\tau^-\to \mu^-\mu^+\mu^-) < 4.6 \times 10^{-8}
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