Publications
865 results found
Aaij R, Beteta CA, Adeva B, et al., 2020, Updated measurement of decay-time-dependent <i>CP</i> asymmetries in <i>D</i><SUP>0</SUP> → <i>K</i><SUP>+</SUP> <i>K</i><SUP>-</SUP> and <i>D</i><SUP>0</SUP> → π<SUP>+</SUP>π<SUP>-</SUP> decays, Publisher: AMER PHYSICAL SOC
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- Citations: 9
Ahdida C, Albanese R, Alexandrov A, et al., 2020, The magnet of the scattering and neutrino detector for the SHiP experiment at CERN, Journal of Instrumentation, Vol: 15, Pages: 1-25, ISSN: 1748-0221
The Search for Hidden Particles (SHiP) experiment proposal at CERN demands a dedicated dipole magnet for its scattering and neutrino detector. This requires a very large volume to be uniformly magnetized at B>1.2 T, with constraints regarding the inner instrumented volume as well as the external region, where no massive structures are allowed and only an extremely low stray field is admitted. In this paper we report the main technical challenges and the relevant design options providing a comprehensive design for the magnet of the SHiP Scattering and Neutrino Detector.
Aaij R, Beteta CA, Adeva B, et al., 2020, Search for the doubly charmed baryon Xi(+)(cc), SCIENCE CHINA Physics, Mechanics and Astronomy, Vol: 63, ISSN: 1674-7348
A search for the doubly charmed baryon Ξ+cc is performed through its decay to the Λ+cK−π+ final state, using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV. The data correspond to a total integrated luminosity of 9 fb−1. No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c2. Upper limits are set at 95% credibility level on the ratio of the Ξ+cc production cross-section times the branching fraction to that of Λ+c and Ξ++cc baryons. The limits are determined as functions of the Ξ+cc mass for different lifetime hypotheses, in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of CP violation in the B-s(0)-> phi phi decay and search for the B-0 -> phi phi decay, The Journal of High Energy Physics, Vol: 2019, Pages: 1-34, ISSN: 1029-8479
A measurement of the time-dependent CP-violating asymmetry in B0s→ϕϕ decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.0 fb−1 collected by the LHCb experiment at centre-of-mass energies s√ = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 B0s→ϕϕ decays is obtained. The CP-violating phase ϕss¯¯¯ss is measured to be −0.073 ± 0.115(stat) ± 0.027(syst) rad, under the assumption it is independent of the helicity of the ϕϕ decay. In addition, the CP-violating phases of the transverse polarisations under the assumption of CP conservation of the longitudinal phase are measured. The helicity-independent direct CP-violation parameter is also measured, and is found to be |λ| = 0.99 ± 0.05(stat) ± 0.01(syst). In addition, T-odd triple-product asymmetries are measured. The results obtained are consistent with the hypothesis of CP conservation in b¯¯→s¯¯¯ss¯¯¯s transitions. Finally, a limit on the branching fraction of the B0 → ϕϕ decay is determined to be B(B0→ϕϕ)<2.7×10−8 at 90 % confidence level.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of the <i>B<sub>c</sub></i><SUP>-</SUP> meson production fraction and asymmetry in 7 and 13 TeV <i>pp</i> collisions, Publisher: AMER PHYSICAL SOC
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- Citations: 13
Aaij R, Beteta CA, Adeva B, et al., 2019, Search for Lepton-Flavor Violating Decays <i>B</i><SUP>+</SUP> → <i>K</i><SUP>+</SUP> μ<SUP>±</SUP> <i>e</i><SUP>∓</SUP>, PHYSICAL REVIEW LETTERS, Vol: 123, ISSN: 0031-9007
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- Citations: 13
Aaij R, Abellán Beteta C, Ackernley T, et al., 2019, Search for lepton-flavor violating decays B+→K+μ±e∓, Physical Review Letters, Vol: 123, Pages: 241802-1-241802-11, ISSN: 0031-9007
A search for the lepton-flavor violating decays B+→K+μ±e∓ is performed using a sample of proton-proton collision data, collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of 3 fb−1. No significant signal is observed, and upper limits on the branching fractions are set as B(B+→K+μ−e+)<7.0(9.5)×10−9 and B(B+→K+μ+e−)<6.4(8.8)×10−9 at 90% (95)% confidence level. The results improve the current best limits on these decays by more than one order of magnitude.
Aaij R, Beteta CA, Adeva B, et al., 2019, Amplitude Analysis of <i>B</i><SUP>±</SUP> → π<SUP>±</SUP><i>K</i><SUP>+</SUP><i>K</i><SUP>-</SUP> Decays, PHYSICAL REVIEW LETTERS, Vol: 123, ISSN: 0031-9007
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- Citations: 35
Aaij R, Abellán Beteta C, Adeva B, et al., 2019, Amplitude analysis of B^{±}→π^{±}K^{+}K^{-} decays., Physical Review Letters, Vol: 123, Pages: 231802-231802, ISSN: 0031-9007
The first amplitude analysis of the B^{±}→π^{±}K^{+}K^{-} decay is reported based on a data sample corresponding to an integrated luminosity of 3.0 fb^{-1} of pp collisions recorded in 2011 and 2012 with the LHCb detector. The data are found to be best described by a coherent sum of five resonant structures plus a nonresonant component and a contribution from ππ↔KK S-wave rescattering. The dominant contributions in the π^{±} K^{∓} and K^{+} K^{-} systems are the nonresonant and the B^{±}→ρ(1450)^{0}π^{±} amplitudes, respectively, with fit fractions around 30%. For the rescattering contribution, a sizable fit fraction is observed. This component has the largest CP asymmetry reported to date for a single amplitude of (-66±4±2)%, where the first uncertainty is statistical and the second systematic. No significant CP violation is observed in the other contributions.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of charged hadron production in Z-tagged jets in proton-Proton collisions at root s=8 TeV, Physical Review Letters, Vol: 123, Pages: 232001-1-232001-11, ISSN: 0031-9007
The production of charged hadrons within jets recoiling against a Z boson is measured in proton-proton collision data at √s=8 TeV recorded by the LHCb experiment. The charged-hadron structure of the jet is studied longitudinally and transverse to the jet axis for jets with transverse momentum pT>20 GeV and in the pseudorapidity range 2.5<η<4. These are the first measurements of jet hadronization at these forward rapidities and also the first where the jet is produced in association with a Z boson. In contrast to previous hadronization measurements at the Large Hadron Collider, which are dominated by gluon jets, these measurements probe predominantly light-quark jets which are found to be more longitudinally and transversely collimated with respect to the jet axis when compared to the previous gluon dominated measurements. Therefore, these results provide valuable information on differences between quarks and gluons regarding nonperturbative hadronization dynamics.
Ahdida C, Albanese R, Alexandrov A, et al., 2019, Fast simulation of muons produced at the SHiP experiment using generative adversarial networks, Journal of Instrumentation, Vol: 14, Pages: 1-19, ISSN: 1748-0221
This paper presents a fast approach to simulating muons produced in interactions of the SPS proton beams with the target of the SHiP experiment. The SHiP experiment will be able to search for new long-lived particles produced in a 400 GeV/c SPS proton beam dump and which travel distances between fifty metres and tens of kilometers. The SHiP detector needs to operate under ultra-low background conditions and requires large simulated samples of muon induced background processes. Through the use of Generative Adversarial Networks it is possible to emulate the simulation of the interaction of 400 GeV/c proton beams with the SHiP target, an otherwise computationally intensive process. For the simulation requirements of the SHiP experiment, generative networks are capable of approximating the full simulation of the dense fixed target, offering a speed increase by a factor of Script O(106). To evaluate the performance of such an approach, comparisons of the distributions of reconstructed muon momenta in SHiP's spectrometer between samples using the full simulation and samples produced through generative models are presented. The methods discussed in this paper can be generalised and applied to modelling any non-discrete multi-dimensional distribution.
Aaij R, Beteta CA, Adeva B, et al., 2019, Search for the Lepton-flavor-violating decays B-s(0) -> pi(+/-mu -/+) and B-0 -> tau(+/-mu -/+), Physical Review Letters, Vol: 123, Pages: 211801-1-211801-11, ISSN: 0031-9007
Results are reported from a search for the rare decays B0s→τ±μ∓ and B0→τ±μ∓, where the τ lepton is reconstructed in the channel τ−→π−π+π−ντ. These processes are effectively forbidden in the standard model, but they can potentially occur at detectable rates in models of new physics that can induce lepton-flavor-violating decays. The search is based on a data sample corresponding to 3 fb−1 of proton-proton collisions recorded by the LHCb experiment in 2011 and 2012. The event yields observed in the signal regions for both processes are consistent with the expected standard model backgrounds. Because of the limited mass resolution arising from the undetected τ neutrino, the B0s and B0 signal regions are highly overlapping. Assuming no contribution from B0→τ±μ∓, the upper limit B(B0s→τ±μ∓)<4.2×10−5 is obtained at 95% confidence level. If no contribution from B0s→τ±μ∓ is assumed, a limit of B(B0→τ±μ∓)<1.4×10−5 is obtained at 95% confidence level. These results represent the first limit on B(B0s→τ±μ∓) and the most stringent limit on B(B0→τ±μ∓).
Aaij R, Abellán Beteta C, Adeva B, et al., 2019, Search for the lepton-flavor-violating decays Bs0→τ±μ∓ and B0→τ±μ∓, Physical Review Letters, Vol: 123, Pages: 211801-1-211801-11, ISSN: 0031-9007
Results are reported from a search for the rare decays B0s→τ±μ∓ and B0→τ±μ∓, where the τ lepton is reconstructed in the channel τ−→π−π+π−ντ. These processes are effectively forbidden in the standard model, but they can potentially occur at detectable rates in models of new physics that can induce lepton-flavor-violating decays. The search is based on a data sample corresponding to 3 fb−1 of proton-proton collisions recorded by the LHCb experiment in 2011 and 2012. The event yields observed in the signal regions for both processes are consistent with the expected standard model backgrounds. Because of the limited mass resolution arising from the undetected τ neutrino, the B0s and B0 signal regions are highly overlapping. Assuming no contribution from B0→τ±μ∓, the upper limit B(B0s→τ±μ∓)<4.2×10−5 is obtained at 95% confidence level. If no contribution from B0s→τ±μ∓ is assumed, a limit of B(B0→τ±μ∓)<1.4×10−5 is obtained at 95% confidence level. These results represent the first limit on B(B0s→τ±μ∓) and the most stringent limit on B(B0→τ±μ∓).
Aaij R, Beteta CA, Ackernley T, et al., 2019, Measurement of the electron reconstruction efficiency at LHCb, Journal of Instrumentation, Vol: 14, Pages: 1-20, ISSN: 1748-0221
The single electron track-reconstruction efficiency is calibrated using a sample corresponding to 1.3 fb−1 of pp collision data recorded with the LHCb detector in 2017. This measurement exploits B+→ J/ψ(e+e−)K+ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the B meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below 1%.
Aaij R, Beteta CA, Ackernley T, et al., 2019, Observation of new resonances in th lambda(0)(b)pi(+)pi(-) system, Physical Review Letters, Vol: 123, Pages: 152001-1-152001-11, ISSN: 0031-9007
We report the observation of a new structure in the Λ0bπ+π− spectrum using the full LHCb data set of pp collisions, corresponding to an integrated luminosity of 9 fb−1, collected at √s=7, 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to bemΛb(6146)0=6146.17±0.33±0.22±0.16 MeV,mΛb(6152)0=6152.51±0.26±0.22±0.16 MeV,ΓΛb(6146)0=2.9±1.3±0.3 MeV,ΓΛb(6152)0=2.1±0.8±0.3 MeV,with a mass splitting of Δm=6.34±0.32±0.02 MeV, where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ0b baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λb(1D)0 states.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of the CP-violating phase phi(s) from B-s(0) -> J/psi pi(+)pi(-) decays in 13 TeV pp collisions, Physics Letters B: Nuclear Physics and Particle Physics, Vol: 797, ISSN: 0370-2693
Aaij R, Beteta CA, Adeva B, et al., 2019, A search for Xi(++)(cc) -> D(+)pK(-)pi(+) decays, The Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
A search for the Ξ++cc baryon through the Ξ++cc→ D+pK−π+ decay is performed with a data sample corresponding to an integrated luminosity of 1.7 fb−1 recorded by the LHCb experiment in pp collisions at a centre-of-mass energy of 13 TeV. No significant signal is observed in the mass range from the kinematic threshold of the decay to 3800 MeV/c2. An upper limit is set on the ratio of branching fractions R=B(Ξ++cc→D+pK−π+)B(Ξ++cc→Λ+cK−π+π+) with ℛ < 1.7 (2.1) × 10−2 at the 90% (95%) confidence level at the known mass of the Ξ++cc state.A search for the Ξ++cc baryon through the Ξ++cc→ D+pK−π+ decay is performed with a data sample corresponding to an integrated luminosity of 1.7 fb−1 recorded by the LHCb experiment in pp collisions at a centre-of-mass energy of 13 TeV. No significant signal is observed in the mass range from the kinematic threshold of the decay to 3800 MeV/c2. An upper limit is set on the ratio of branching fractions R=B(Ξ++cc→D+pK−π+)B(Ξ++cc→Λ+cK−π+π+) with ℛ < 1.7 (2.1) × 10−2 at the 90% (95%) confidence level at the known mass of the Ξ++cc state.
Aaij R, Beteta CA, Adeva B, et al., 2019, Observation of the Λ<sub>b</sub><SUP>0</SUP> → χ<sub>c1</sub> (3872)pK<SUP>-</SUP> decay, Publisher: SPRINGER
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- Citations: 6
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurements of CP asymmetries in charmless four-body Lambda(0)(b) and Xi(0)(b) decays, European Physical Journal C: Particles and Fields, Vol: 79, Pages: 1-19, ISSN: 1124-1861
A search for 𝐶𝑃 violation in charmless four-body decays of 𝛬0𝑏 and 𝛯0𝑏 baryons with a proton and three charged mesons in the final state is performed. To cancel out production and detection charge-asymmetry effects, the search is carried out by measuring the difference between the 𝐶𝑃 asymmetries in a charmless decay and in a decay with an intermediate charmed baryon with the same particles in the final state. The data sample used was recorded in 2011 and 2012 with the LHCb detector and corresponds to an integrated luminosity of 3 fb−1 . A total of 18 𝐶𝑃 asymmetries are considered, either accounting for the full phase space of the decays or exploring specific regions of the decay kinematics. No significant 𝐶𝑃 -violation effect is observed in any of the measurements.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of b hadron fractions in 13 TeV pp collisions, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, ISSN: 1550-2368
The production fractions of ¯B0s and Λ0b hadrons, normalized to the sum of B− and ¯B0 fractions, are measured in 13 TeV pp collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of 1.67 fb−1. These ratios, averaged over the b hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are 0.122±0.006 for ¯B0s, and 0.259±0.018 for Λ0b, where the uncertainties arise from both statistical and systematic sources. The Λ0b ratio depends strongly on transverse momentum, while the ¯B0s ratio shows a mild dependence. Neither ratio shows variations with pseudorapidity. The measurements are made using semileptonic decays to minimize theoretical uncertainties. In addition, the ratio of D+ to D0 mesons produced in the sum of ¯B0 and B− semileptonic decays is determined as 0.359±0.006±0.009, where the uncertainties are statistical and systematic.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of CP-violating and mixing-induced observables in B-s(0) -> phi gamma decays, Physical Review Letters, Vol: 123, ISSN: 0031-9007
A time-dependent analysis of the B0s→ϕγ decay rate is performed to determine the CP -violating observables Sϕγ and Cϕγ and the mixing-induced observable AΔϕγ. The measurement is based on a sample of pp collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3 fb−1 at center-of-mass energies of 7 and 8 TeV. The measured values are Sϕγ=0.43±0.30±0.11, Cϕγ=0.11±0.29±0.11, and AΔϕγ=−0.67+0.37−0.41±0.17, where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables S and C in radiative B0s decays. The results are consistent with the standard model predictions.
Aaij R, Beteta CA, Adeva B, et al., 2019, Search for the rare decay B+→ µ+µ−µ+νµ, European Physical Journal C: Particles and Fields, Vol: 79, ISSN: 1434-6044
A search for the rare leptonic decay B+→μ+μ−μ+νμ is performed using proton-proton collision data corresponding to an integrated luminosity of 4.7fb−1 collected by the LHCb experiment. The search is carried out in the region where the lowest of the two μ+μ− mass combinations is below 980MeV/c2 . The data are consistent with the background-only hypothesis and an upper limit of 1.6×10−8 at 95% confidence level is set on the branching fraction in the stated kinematic region.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of CP observables in the process B-0 -> DK*0 with two- and four-body D decays, The Journal of High Energy Physics, Vol: 41, Pages: 1-30, ISSN: 1029-8479
Measurements of CP observables in B0 → DK∗0 decays are presented, where D represents a superposition of D0 and 𝐷⎯⎯⎯⎯⎯0 states. The D meson is reconstructed in the two-body final states K+π−, π+K−, K+K− and π+π−, and, for the first time, in the fourbody final states K+π−π+π−, π+K−π+π− and π+π−π+π−. The analysis uses a sample of neutral B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 fb−1 collected with the LHCb detector at centre-of-mass energies of 𝑠√=7,8 and 13 TeV, respectively. First observations of the decays B0 → D(π+K−)K∗0 and B0 → D(π+π−π+π−)K∗0 are obtained. The measured observables are interpreted in terms of the CP -violating weak phase γ.
Aaij R, Beteta CA, Adeva B, et al., 2019, Precision measurement of the Λ<i><sub>c</sub></i><SUP>+</SUP>, Ξ<i><sub>c</sub></i><SUP>+</SUP>, and Ξ<sub>c</sub><SUP>0</SUP> baryon lifetimes, Publisher: AMER PHYSICAL SOC
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- Citations: 20
Aaij R, Beteta CA, Ackernley T, et al., 2019, Updated measurement of time-dependent CP -violating observables in B⁰s→J/ψK+K− decays, European Physical Journal C: Particles and Fields, Vol: 79, ISSN: 1124-1861
The decay-time-dependent CP asymmetry in B0s→J/ψK+K− decays is measured using proton–proton collision data, corresponding to an integrated luminosity of 1.9fb−1 , collected with the LHCb detector at a centre-of-mass energy of 13TeV in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant K+K− mass in the vicinity of the ϕ(1020) resonance, the CP -violating phase ϕs is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the B0s - B¯¯¯¯0s system, ΔΓs . The difference of the average B0s and B0 meson decay widths, Γs−Γd , is determined using in addition a sample of B0→J/ψK+π− decays. The values obtained are ϕs=−0.083±0.041±0.006rad , ΔΓs=0.077±0.008±0.003ps−1 and Γs−Γd=−0.0041±0.0024±0.0015ps−1 , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from B0s→J/ψπ+π− decays obtained using the same dataset as this analysis, and with previous independent LHCb results.
Aaij R, Beteta CA, Adeva B, et al., 2019, First Observation of the Radiative Decay Lambda(0 )(b)-> Lambda gamma, Physical Review Letters, Vol: 123, ISSN: 0031-9007
The radiative decay Λ0b→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(Λ0b→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.
Aaij R, Abellan Beteta C, Adeva B, et al., 2019, Near-threshold DD spectroscopy and observation of a new charmonium state, Publisher: SPRINGER
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- Citations: 30
Aaij R, Abellan Beteta C, Adeva B, et al., 2019, Amplitude analysis of the B0(s)→K∗0K¯¯¯¯¯∗0 decays and measurement of the branching fraction of the B0→K∗0K¯¯¯¯¯∗0 decay, The Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
The B0→K∗0K¯¯¯¯¯∗0 and B0s→K∗0K¯¯¯¯¯∗0 decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb−1. An untagged and timeintegrated amplitude analysis of B ( s) 0 → (K+π−)(K−π+) decays in two-body invariant mass regions of 150 MeV/c2 around the K∗0 mass is performed. A stronger longitudinal polarisation fraction in the B0→K∗0K¯¯¯¯¯∗0 decay, fL = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to fL = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the B0s→K∗0K¯¯¯¯¯∗0 decay. The ratio of branching fractions of the two decays is measured and used to determine B(B0→K∗0K¯¯¯¯¯∗0)=(8.0±0.9(stat)±0.4(syst))×10−7 .
Aaij R, Beteta CA, Adeva B, et al., 2019, Amplitude analysis of B s ⁰ → K S ⁰ K±π∓ decays, The Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
The first untagged decay-time-integrated amplitude analysis of B s 0 → K S 0 K±π∓ decays is performed using a sample corresponding to 3.0 fb−1 of pp collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances K*(892)0,+, K 2 * (1430)0,+ and K 0 * (1430)0,+, and their charge conjugates. Measurements of the branching fractions of the decay modes B s 0 → K*(892)±K∓ and B0s→K∗(---)(892)0K0(---) are in agreement with, and more precise than, previous results. The decays B s 0 → K 0 * (1430)±K∓ and B0s→K∗0(---)(1430)0K0(---) are observed for the first time, each with significance over 10 standard deviations.
Aaij R, Beteta CA, Adeva B, et al., 2019, Measurement of the mass difference between neutral charm-meson eigenstates, Physical Review Letters, Vol: 122, ISSN: 0031-9007
We report a measurement of the mass difference between neutral charm-meson eigenstates using a novel approach that enhances sensitivity to this parameter. We use 2.3×106 D0→K0Sπ+π− decays reconstructed in proton-proton collisions collected by the LHCb experiment in 2011 and 2012. Allowing for CP violation in mixing and in the interference between mixing and decay, we measure the CP-averaged normalized mass difference xCP=[2.7±1.6(stat)±0.4(syst)]×10−3 and the CP-violating parameter Δx=[−0.53±0.70(stat)±0.22(syst)]×10−3. The results are consistent with CP symmetry. These determinations are the most precise from a single experiment and, combined with current world-average results, yield the first evidence that the masses of the neutral charm-meson eigenstates differ.
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