Abstract The resonant substructure of D 0 → π+π−π+π− decays is studied using data collected by the CLEO-c detector. An amplitude analysis is performed in order to disentangle the various intermediate ...state contributions. To limit the model complexity a data driven regularization procedure is applied. The prominent contributions are the decay modes D 0 → a 1(1260)+ π−, D 0 → σ f 0(1370) and D 0 → ρ(770)0 ρ(770)0. The broad resonances a 1(1260)+, π(1300)+ and a 1(1640)+ are studied in detail, including quasi-modelindependent parametrizations of their lineshapes. The mass and width of the a 1(1260)+ meson are determined to be m a1(1260)+ = 1225 ± 9 (stat) ± 17 (syst) ± 10 (model) MeV/c 2 and Γa1(1260)+ = 430 ± 24 (stat) ± 25 (syst) ± 18 (model) MeV. The amplitude model of D 0 → K + K −π+π− decays obtained from CLEO II.V, CLEO III, and CLEO-c data is revisited with improved lineshape parametrizations. The largest components are the decay modes D 0 → ϕ(1020)ρ(770)0, D 0 → K 1(1270)+ K − and D 0 → K(1400)+ K −. The fractional CP -even content of the decay D 0 → π+π−π+π− is calculated from the amplitude model to be F + 4π = 72.9 ± 0.9(stat) ± 1.5(syst) ± 1.0(model) %, consistent with that obtained from a previous model-independent measurement. For D 0 → K + K −π+π− decays, the CP -even fraction is measured for the first time and found to be F + KKππ = 75.3 ± 1.8 (stat) ± 3.3 (syst) ± 3.5 (model) %. The global decay rate asymmetries between D 0 and D ¯ 0 $$ {\overline{D}}^0 $$ decays are measured to be A C P 4 π = + 0.54 ± 1.04 stat ± 0.51 syst % $$ {\mathcal{A}}_{CP}^{4\uppi}=\left+0.54\pm 1.04\ \left(\mathrm{stat}\right)\pm 0.51\ \left(\mathrm{syst}\right)\right\% $$ and A C P KKππ = + 1.84 ± 1.74 stat ± 0.30 syst % $$ {\mathcal{A}}_{CP}^{KK\pi \pi}=\left+1.84\pm 1.74\ \left(\mathrm{stat}\right)\pm 0.30\ \left(\mathrm{syst}\right)\right\% $$ . A search for CP asymmetries in the amplitude components yields no evidence for CP violation in either decay mode.
Abstract
The performance of the ring-imaging Cherenkov detectors at
the LHCb experiment is determined during the LHC Run 2 period
between 2015 and 2018. The stability of the Cherenkov angle
...resolution and number of detected photons with time and running
conditions is measured. The particle identification performance is
evaluated with data and found to satisfy the requirements of the
physics programme.
Quantum-correlated ψ(3770)→DD‾ decays collected by the CLEO-c experiment are used to perform a first measurement of F+4π, the fractional CP-even content of the self-conjugate decay D→π+π−π+π−, ...obtaining a value of 0.737±0.028. An important input to the measurement comes from the use of D→KS0π+π− and D→KL0π+π− decays to tag the signal mode. This same technique is applied to the channels D→π+π−π0 and D→K+K−π0, yielding F+πππ0=1.014±0.045±0.022 and F+KKπ0=0.734±0.106±0.054, where the first uncertainty is statistical and the second systematic. These measurements are consistent with those of an earlier analysis, based on CP-eigenstate tags, and can be combined to give values of F+πππ0=0.973±0.017 and F+KKπ0=0.732±0.055. The results will enable the three modes to be included in a model-independent manner in measurements of the unitarity triangle angle γ using B∓→DK∓ decays, and in time-dependent studies of CP violation and mixing in the D0D‾0 system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the ...electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and ...mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar Tcc+ tetraquark with a quark content of ccu¯d¯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector Tcc+ state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the Tcc+ state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.The existence and properties of tetraquark states with two heavy quarks and two light antiquarks have been widely debated. Here, the authors use a unitarized model to study the properties of an exotic narrow state compatible with a doubly charmed tetraquark.
The only anticipated resonant contributions to B^{+}→D^{+}D^{-}K^{+} decays are charmonium states in the D^{+}D^{-} channel. A model-independent analysis, using LHCb proton-proton collision data ...taken at center-of-mass energies of sqrts=7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb^{-1}, is carried out to test this hypothesis. The description of the data assuming that resonances only manifest in decays to the D^{+}D^{-} pair is shown to be incomplete. This constitutes evidence for a new contribution to the decay, potentially one or more new charm-strange resonances in the D^{-}K^{+} channel with masses around 2.9 GeV/c^{2}.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
We present an angular analysis of the B^{+}→K^{*+}(→K_{S}^{0}π^{+})μ^{+}μ^{-} decay using 9 fb^{-1} of pp collision data collected with the LHCb experiment. For the first time, the full set of ...CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B^{0}→K^{*0}μ^{+}μ^{-} decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
A measurement is reported of the ratio of branching fractions R(J/ψ)=B(B_{c}^{+}→J/ψτ^{+}ν_{τ})/B(B_{c}^{+}→J/ψμ^{+}ν_{μ}), where the τ^{+} lepton is identified in the decay mode ...τ^{+}→μ^{+}ν_{μ}νover ¯_{τ}. This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb^{-1} of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B_{c}^{+}→J/ψτ^{+}ν_{τ} at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R(J/ψ)=0.71±0.17(stat)±0.18(syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
A search for charge-parity (CP) violation in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb^{-1} collected at a ...center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D^{*}(2010)^{+}→D^{0}π^{+} decays or from the charge of the muon in Bover ¯→D^{0}μ^{-}νover ¯_{μ}X decays. The difference between the CP asymmetries in D^{0}→K^{-}K^{+} and D^{0}→π^{-}π^{+} decays is measured to be ΔA_{CP}=-18.2±3.2(stat)±0.9(syst)×10^{-4} for π-tagged and ΔA_{CP}=-9±8(stat)±5(syst)×10^{-4} for μ-tagged D^{0} mesons. Combining these with previous LHCb results leads to ΔA_{CP}=(-15.4±2.9)×10^{-4}, where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than 5 standard deviations. This is the first observation of CP violation in the decay of charm hadrons.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
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