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First Observation of the Radiative Decay <math><msubsup><mi>Λ</mi><mi>b</mi><mn>0</mn></msubsup><mo>→</mo><mi>Λ</mi><mi>γ</mi></math>
https://repo.scoap3.org/record/33845
The radiative decay Λb0→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(Λb0→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.Mon, 15 Jul 2019 20:16:06 GMThttps://repo.scoap3.org/record/33845APS2019-07-15Near-threshold D D ¯ $$ \mathrm{D}\overline{\mathrm{D}} $$ spectroscopy and observation of a new charmonium state
https://repo.scoap3.org/record/33757
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb −1 , collected with the LHCb detector between 2011 and 2018, a new narrow charmonium state, the X(3842) resonance, is observed in the decay modes X 3842 → D 0 D ¯ 0 $$ \mathrm{X}(3842)\to {D}^0{\overline{D}}^0 $$ and X(3842) → D + D − . The mass and the natural width of this state are measured to beAaij, R.Wed, 10 Jul 2019 10:43:47 GMThttps://repo.scoap3.org/record/337572019-07-08Amplitude analysis of the B s 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}_{(s)}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ decays and measurement of the branching fraction of the B 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ decay
https://repo.scoap3.org/record/33700
The B 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ and B s 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ 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/ c 2 around the K ∗0 mass is performed. A stronger longitudinal polarisation fraction in the B 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ decay, f L = 0 . 724 ± 0 . 051 (stat) ± 0 . 016 (syst), is observed as compared to f L = 0 . 240 ± 0 . 031 (stat) ± 0 . 025 (syst) in the B s 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} $$ decay. The ratio of branching fractions of the two decays is measured and used to determine ℬ B 0 → K ∗ 0 K ¯ ∗ 0 = 8.0 ± 0.9 stat ± 0.4 syst × 10 − 7 $$ \mathrm{\mathcal{B}}\left({B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}\right)=\left(8.0\pm 0.9\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)\right)\times {10}^{-7} $$ .Aaij, R.Mon, 08 Jul 2019 11:50:11 GMThttps://repo.scoap3.org/record/337002019-07-05Amplitude analysis of B s 0 → K S 0 K ± π ∓ decays
https://repo.scoap3.org/record/33523
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 B s 0 → K * — 892 0 K 0 — $$ {B}_s^0\to \overset{\left(\hbox{---} \right)}{K^{*}}{(892)}^0\overset{\left(\hbox{---} \right)}{K^0} $$ are in agreement with, and more precise than, previous results. The decays B s 0 → K 0 * (1430) ± K ∓ and B s 0 → K 0 * — 1430 0 K 0 — $$ {B}_s^0\to \overset{\left(\hbox{---} \right)}{K_0^{*}}{(1430)}^0\overset{\left(\hbox{---} \right)}{K^0} $$ are observed for the first time, each with significance over 10 standard deviations.Aaij, R.Mon, 24 Jun 2019 09:44:32 GMThttps://repo.scoap3.org/record/335232019-06-21Measurement of the Mass Difference Between Neutral Charm-Meson Eigenstates
https://repo.scoap3.org/record/33380
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→KS0π+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.Aaij, R.Tue, 18 Jun 2019 14:03:09 GMThttps://repo.scoap3.org/record/33380APS2019-06-14Observation of an Excited <math><msubsup><mi>B</mi><mi>c</mi><mo>+</mo></msubsup></math> State
https://repo.scoap3.org/record/33246
Using pp collision data corresponding to an integrated luminosity of 8.5 fb−1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π− invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc*(2S31)+ state reconstructed without the low-energy photon from the Bc*(1S31)+→Bc+γ decay following Bc*(2S31)+→Bc*(1S31)+π+π−. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date.Aaij, R.Wed, 12 Jun 2019 00:18:11 GMThttps://repo.scoap3.org/record/33246APS2019-06-11Observation of a Narrow Pentaquark State, <math><mrow><msub><mrow><mi>P</mi></mrow><mrow><mi>c</mi></mrow></msub><mo>(</mo><mn>4312</mn><msup><mrow><mo>)</mo></mrow><mrow><mo>+</mo></mrow></msup></mrow></math>, and of the Two-Peak Structure of the <math><msub><mi>P</mi><mi>c</mi></msub><mo>(</mo><mn>4450</mn><msup><mo>)</mo><mo>+</mo></msup></math>
https://repo.scoap3.org/record/33152
A narrow pentaquark state, Pc(4312)+, decaying to J/ψp, is discovered with a statistical significance of 7.3σ in a data sample of Λb0→J/ψpK− decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The Pc(4450)+ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, Pc(4440)+ and Pc(4457)+, where the statistical significance of this two-peak interpretation is 5.4σ. The proximity of the Σc+D¯0 and Σc+D¯*0 thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.Aaij, R.Wed, 05 Jun 2019 20:16:33 GMThttps://repo.scoap3.org/record/33152APS2019-06-05Measurement of the relative <math><mrow><msup><mrow><mi>B</mi></mrow><mrow><mo>−</mo></mrow></msup><mo>→</mo><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>/</mo><msup><mrow><mi>D</mi></mrow><mrow><mo>*</mo><mn>0</mn></mrow></msup><mo>/</mo><msup><mrow><mi>D</mi></mrow><mrow><mrow><mo>*</mo><mo>*</mo></mrow><mn>0</mn></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>μ</mi></mrow></msub></mrow></math> branching fractions using <math><msup><mi>B</mi><mo>−</mo></msup></math> mesons from <math><mrow><msubsup><mrow><mover><mrow><mi>B</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>s</mi><mn>2</mn></mrow><mrow><mo>*</mo><mn>0</mn></mrow></msubsup></mrow></math> decays
https://repo.scoap3.org/record/33101
The decay of the narrow resonance B¯s2*0→B−K+ can be used to determine the B− momentum in partially reconstructed decays without any assumptions on the decay products of the B− meson. This technique is employed for the first time to distinguish contributions from D0, D*0, and higher-mass charmed states (D**0) in semileptonic B− decays by using the missing-mass distribution. The measurement is performed using a data sample corresponding to an integrated luminosity of 3.0 fb−1 collected with the LHCb detector in pp collisions at center-of-mass energies of 7 and 8 TeV. The resulting branching fractions relative to the inclusive B−→D0Xμ−ν¯μ are fD0=B(B−→D0μ−ν¯μ)/B(B−→D0Xμ−ν¯μ)=0.25±0.06,fD**0=B(B−→(D**0→D0X)μ−ν¯μ)/B(B−→D0Xμ−ν¯μ)=0.21±0.07, with fD*0=1−fD0−fD**0 making up the remainder.Aaij, R.Fri, 31 May 2019 16:16:56 GMThttps://repo.scoap3.org/record/33101urn:ISSN:2470-0029APS2019-05-31Observation of <math><mi>C</mi><mi>P</mi></math> Violation in Charm Decays
https://repo.scoap3.org/record/33069
A search for charge-parity (CP) violation in D0→K−K+ and D0→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)+→D0π+ decays or from the charge of the muon in B¯→D0μ−ν¯μX decays. The difference between the CP asymmetries in D0→K−K+ and D0→π−π+ decays is measured to be ΔACP=[−18.2±3.2(stat)±0.9(syst)]×10−4 for π-tagged and ΔACP=[−9±8(stat)±5(syst)]×10−4 for μ-tagged D0 mesons. Combining these with previous LHCb results leads to ΔACP=(−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.Aaij, R.Wed, 29 May 2019 20:21:40 GMThttps://repo.scoap3.org/record/33069urn:ISSN:1079-7114APS2019-05-29Observation of <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow><mrow><mn>0</mn></mrow></msubsup><mo>→</mo><mi>J</mi><mo>/</mo><mi>ψ</mi><mi>p</mi><mover><mrow><mi>p</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math> Decays and Precision Measurements of the <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow><mrow><mn>0</mn></mrow></msubsup></mrow></math> Masses
https://repo.scoap3.org/record/32992
The first observation of the decays B(s)0→J/ψpp¯ is reported, using proton-proton collision data corresponding to an integrated luminosity of 5.2 fb−1, collected with the LHCb detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are B(B0→J/ψpp¯)=[4.51±0.40(stat)±0.44(syst)]×10−7, B(Bs0→J/ψpp¯)=[3.58±0.19(stat)±0.39(syst)]×10−6. For the Bs0 meson, the result is much higher than the expected value of O(10−9). The small available phase space in these decays also allows for the most precise single measurement of both the B0 mass as 5279.74±0.30(stat)±0.10(syst) MeV and the Bs0 mass as 5366.85±0.19(stat)±0.13(syst) MeV.Aaij, R.Tue, 28 May 2019 09:41:15 GMThttps://repo.scoap3.org/record/32992urn:ISSN:1079-7114APS2019-05-17Search for <math><mi>C</mi><mi>P</mi></math> Violation in <math><msubsup><mi>D</mi><mi>s</mi><mo>+</mo></msubsup><mo>→</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>π</mi><mo>+</mo></msup></math>, <math><msup><mi>D</mi><mo>+</mo></msup><mo>→</mo><msubsup><mi>K</mi><mi>S</mi><mn>0</mn></msubsup><msup><mi>K</mi><mo>+</mo></msup></math>, and <math><msup><mi>D</mi><mo>+</mo></msup><mo>→</mo><mi>ϕ</mi><msup><mi>π</mi><mo>+</mo></msup></math> Decays
https://repo.scoap3.org/record/32991
A search for charge-parity (CP) violation in Cabibbo-suppressed Ds+→KS0π+, D+→KS0K+, and D+→ϕπ+ decays is reported using proton-proton collision data, corresponding to an integrated luminosity of 3.8 fb−1, collected at a center-of-mass energy of 13 TeV with the LHCb detector. High-yield samples of kinematically and topologically similar Cabibbo-favored D(s)+ decays are analyzed to subtract nuisance asymmetries due to production and detection effects, including those induced by CP violation in the neutral kaon system. The results are ACP(Ds+→KS0π+)=(1.3±1.9±0.5)×10−3,ACP(D+→KS0K+)=(−0.09±0.65±0.48)×10−3,ACP(D+→ϕπ+)=(0.05±0.42±0.29)×10−3,where the first uncertainties are statistical and the second systematic. They are the most precise measurements of these quantities to date, and are consistent with CP symmetry. A combination with previous LHCb measurements, based on data collected at 7 and 8 TeV, is also reported.Aaij, R.Tue, 28 May 2019 09:41:07 GMThttps://repo.scoap3.org/record/32991urn:ISSN:1079-7114APS2019-05-17Search for Lepton-Universality Violation in <math><msup><mi>B</mi><mo>+</mo></msup><mo>→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> Decays
https://repo.scoap3.org/record/32989
A measurement of the ratio of branching fractions of the decays B+→K+μ+μ− and B+→K+e+e− is presented. The proton-proton collision data used correspond to an integrated luminosity of 5.0 fb−1 recorded with the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. For the dilepton mass-squared range 1.1<q2<6.0 GeV2/c4 the ratio of branching fractions is measured to be RK=0.846−0.054+0.060−0.014+0.016, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of RK to date and is compatible with the standard model at the level of 2.5 standard deviations.Aaij, R.Tue, 28 May 2019 09:40:59 GMThttps://repo.scoap3.org/record/32989urn:ISSN:1079-7114APS2019-05-13Erratum to: Measurement of ϒ production in pp collisions at s $$ \sqrt{\mathrm{s}} $$ = 13 TeV
https://repo.scoap3.org/record/32739
The top plot shown in figure 3 of ref. [1] is the result of 8 TeV.Aaij, R.Mon, 27 May 2019 15:30:59 GMThttps://repo.scoap3.org/record/32739urn:ISSN:1029-8479Springer/SISSA2019-05-15Study of the B 0 → ρ (770)° K * (892) 0 decay with an amplitude analysis of B 0 → ( π + π − )( K + π − ) decays
https://repo.scoap3.org/record/32692
An amplitude analysis of B 0 → ( π + π − )( K + π − ) decays is performed in the two-body invariant mass regions 300 < m ( π + π − ) < 1100 MeV/ c 2 , accounting for the ρ 0 , ω , f 0 (500), f 0 (980) and f 0 (1370) resonances, and 750 < m ( K + π − ) < 1200 MeV/ c 2 , which is dominated by the K * (892) 0 meson. The analysis uses 3 fb −1 of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The CP averages and asymmetries are measured for the magnitudes and phase differences of the con- tributing amplitudes. The CP -averaged longitudinal polarisation fractions of the vector-vector modes are found to be f ˜ ρ K * 0 $$ {\tilde{f}}_{\rho {K}^{*}}^0 $$ = 0 . 164 ± 0 . 015 ± 0 . 022 and f ˜ ω K * 0 $$ {\tilde{f}}_{\omega {K}^{*}}^0 $$ = 0 . 68 ± 0 . 17 ± 0 . 16, and their CP asymmetries, A ρ K * 0 $$ {\mathcal{A}}_{\rho {K}^{*}}^0 $$ = −0 . 62 ± 0 . 09 ± 0 . 09 and A ω K * 0 $$ {\mathcal{A}}_{\omega {K}^{*}}^0 $$ = −0 . 13 ± 0 . 27 ± 0 . 13, where the first uncertainty is statistical and the second systematic.Aaij, R.Mon, 27 May 2019 15:22:58 GMThttps://repo.scoap3.org/record/32692urn:ISSN:1029-8479Springer/SISSA2019-05-06Model-Independent Observation of Exotic Contributions to <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow><msup><mi>K</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> Decays
https://repo.scoap3.org/record/32365
An angular analysis of B0→J/ψK+π− decays is performed, using proton-proton collision data corresponding to an integrated luminosity of 3 fb−1 collected with the LHCb detector. The m(K+π−) spectrum is divided into fine bins. In each m(K+π−) bin, the hypothesis that the three-dimensional angular distribution can be described by structures induced only by K* resonances is examined, making minimal assumptions about the K+π− system. The data reject the K*-only hypothesis with a large significance, implying the observation of exotic contributions in a model-independent fashion. Inspection of the m(J/ψπ−) vs m(K+π−) plane suggests structures near m(J/ψπ−)=4200 and 4600 MeV.Aaij, R.Thu, 18 Apr 2019 04:16:44 GMThttps://repo.scoap3.org/record/32365urn:ISSN:1079-7114APS2019-04-17Observation of the doubly Cabibbo-suppressed decay Ξ c + → pϕ
https://repo.scoap3.org/record/32281
The doubly Cabibbo-suppressed decay Ξ c + → pϕ with ϕ → K + K − is observed for the first time, with a statistical significance of more than fifteen standard deviations. The data sample used in this analysis corresponds to an integrated luminosity of 2 fb −1 recorded with the LHCb detector in pp collisions at a centre-of-mass energy of 8 TeV. The ratio of branching fractions between the decay Ξ c + → pϕ and the singly Cabibbo-suppressed decay Ξ c + → pK − π + is measured to be ℬ Ξ c + → p ϕ ℬ Ξ c + → p K − π + = 19.8 ± 0.7 ± 0.9 ± 0.2 × 10 − 3 , $$ \frac{\mathrm{\mathcal{B}}\left({\varXi}_c^{+}\to p\phi \right)}{\mathrm{\mathcal{B}}\left({\varXi}_c^{+}\to p{K}^{-}{\pi}^{+}\right)}=\left(19.8\pm 0.7\pm 0.9\pm 0.2\right)\times {10}^{-3}, $$Aaij, R.Sat, 13 Apr 2019 16:01:19 GMThttps://repo.scoap3.org/record/32281urn:ISSN:1029-8479Springer/SISSA2019-04-10Dalitz plot analysis of the D + → K − K + K + decay
https://repo.scoap3.org/record/32245
The resonant structure of the doubly Cabibbo-suppressed decay D + → K − K + K + is studied for the first time. The measurement is based on a sample of pp -collision data, collected at a centre-of-mass energy of 8 TeV with the LHCb detector and corresponding to an integrated luminosity of 2 fb −1 . The amplitude analysis of this decay is performed with the isobar model and a phenomenological model based on an effective chiral Lagrangian. In both models the S-wave component in the K − K + system is dominant, with a small contribution of the ϕ (1020) meson and a negligible contribution from tensor resonances. The K + K − scattering amplitudes for the considered combinations of spin (0,1) and isospin (0,1) of the two-body system are obtained from the Dalitz plot fit with the phenomenological decay amplitude.Aaij, R.Fri, 12 Apr 2019 14:27:01 GMThttps://repo.scoap3.org/record/32245urn:ISSN:1029-8479Springer/SISSA2019-04-08First Measurement of Charm Production in its Fixed-Target Configuration at the LHC
https://repo.scoap3.org/record/32041
The first measurement of heavy-flavor production by the LHCb experiment in its fixed-target mode is presented. The production of J/ψ and D0 mesons is studied with beams of protons of different energies colliding with gaseous targets of helium and argon with nucleon-nucleon center-of-mass energies of sNN=86.6 and 110.4 GeV, respectively. The J/ψ and D0 production cross sections in pHe collisions in the rapidity range [2, 4.6] are found to be σJ/ψ=652±33(stat)±42(syst) nb/nucleon and σD0=80.8±2.4(stat)±6.3(syst) μb/nucleon, where the first uncertainty is statistical and the second is systematic. No evidence for a substantial intrinsic charm content of the nucleon is observed in the large Bjorken-x region.Aaij, R.Tue, 09 Apr 2019 15:06:37 GMThttps://repo.scoap3.org/record/32041urn:ISSN:1079-7114APS2019-04-02Measurement of <math><msup><mi>B</mi><mo>+</mo></msup></math>, <math><msup><mi>B</mi><mn>0</mn></msup></math> and <math><msubsup><mi>Λ</mi><mi>b</mi><mn>0</mn></msubsup></math> production in <math><mrow><mi>p</mi><mi>Pb</mi></mrow></math> collisions at <math><msqrt><msub><mi>s</mi><mrow><mi>NN</mi></mrow></msub></msqrt><mo>=</mo><mn>8.16</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>
https://repo.scoap3.org/record/31887
The production of B+, B0 and Λb0 hadrons is studied in proton-lead collisions at a center-of-mass energy per nucleon pair of sNN=8.16 TeV recorded with the LHCb detector at the LHC. The measurement uses a dataset corresponding to an integrated luminosity of 12.2±0.3 nb−1 for the case where the proton beam is projected into the LHCb detector (corresponding to measuring hadron production at positive rapidity) and 18.6±0.5 nb−1 for the lead beam projected into the LHCb detector (corresponding to measuring hadron production at negative rapidity). Double-differential cross sections are measured and used to determine forward-backward ratios and nuclear modification factors, which directly probe nuclear effects in the production of beauty hadrons. The double-differential cross sections are measured as a function of the beauty-hadron transverse momentum and rapidity in the nucleon-nucleon center-of-mass frame. Forward-to-backward cross section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity. The ratio of Λb0 over B0 production cross sections is reported and is consistent with the corresponding measurement in pp collisions.Aaij, R.Wed, 27 Mar 2019 21:17:25 GMThttps://repo.scoap3.org/record/31887urn:ISSN:2470-0029APS2019-03-27Measurement of the ratio of branching fractions of the decays Λ b 0 → ψ (2 S )Λ and Λ b 0 → J / ψ Λ
https://repo.scoap3.org/record/31810
Using pp collisions corresponding to 3 fb −1 integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, the ratio of branching fractions ℬ Λ b 0 → ψ 2 S Λ / ℬ Λ b 0 → J / ψ Λ = 0.513 ± 0.023 stat ± 0.016 syst ± 0.011 ℬ $$ \mathrm{\mathcal{B}}\left({\Lambda}_b^0\to \psi (2S)\Lambda \right)/\mathrm{\mathcal{B}}\left({\Lambda}_b^0\to J/\psi \Lambda \right)=0.513\pm 0.023\left(\mathrm{stat}\right)\pm 0.016\left(\mathrm{syst}\right)\pm 0.011\left(\mathrm{\mathcal{B}}\right) $$ is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.Aaij, R.Mon, 25 Mar 2019 20:20:58 GMThttps://repo.scoap3.org/record/31810urn:ISSN:1029-8479Springer/SISSA2019-03-22Measurement of the mass and production rate of <math><msubsup><mi>Ξ</mi><mi>b</mi><mo>−</mo></msubsup></math> baryons
https://repo.scoap3.org/record/31714
The first measurement of the production rate of Ξb− baryons in pp collisions relative to that of Λb0 baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and 1.6 fb−1 at s=7, 8 and 13 TeV, respectively. In the kinematic region 2<η<6 and pT<20 GeV/c, we measure fΞb−fΛb0B(Ξb−→J/ψΞ−)B(Λb0→J/ψΛ)=(10.8±0.9±0.8)×10−2 [s=7,8 TeV], fΞb−fΛb0B(Ξb−→J/ψΞ−)B(Λb0→J/ψΛ)=(13.1±1.1±1.0)×10−2 [s=13 TeV], where fΞb− and fΛb0 are the fragmentation fractions of b quarks into Ξb− and Λb0 baryons, respectively; B represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of fΞb−/fΛb0 are obtained by invoking SU(3) symmetry in the Ξb−→J/ψΞ− and Λb0→J/ψΛ decays. Production asymmetries between Ξb− and Ξ¯b+ baryons are also reported. The mass of the Ξb− baryon is also measured relative to that of the Λb0 baryon, from which it is found that m(Ξb−)=5796.70±0.39±0.15±0.17 MeV/c2, where the last uncertainty is due to the precision on the known Λb0 mass. This result represents the most precise determination of the Ξb− mass.Aaij, R.Sat, 23 Mar 2019 01:16:07 GMThttps://repo.scoap3.org/record/31714urn:ISSN:2470-0029APS2019-03-22Search for CP violation through an amplitude analysis of D 0 → K + K − π + π − decays
https://repo.scoap3.org/record/31200
A search for CP violation in the Cabibbo-suppressed D 0 → K + K − π + π − decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb −1 . The D 0 mesons are reconstructed from semileptonic b -hadron decays into D 0 μ − X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D 0 decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered.Aaij, R.Sat, 23 Feb 2019 15:19:12 GMThttps://repo.scoap3.org/record/31200urn:ISSN:1029-8479Springer/SISSA2019-02-20Prompt Λ c + production in p Pb collisions at s N N = 5.02 $$ \sqrt{s_{\mathrm{NN}}}=5.02 $$ TeV
https://repo.scoap3.org/record/31052
The prompt production of Λ c + baryons is studied in proton-lead collisions collected with the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of 1.58 nb −1 recorded at a nucleon-nucleon centre-of-mass energy of s N N = 5.02 $$ \sqrt{s_{\mathrm{NN}}}=5.02 $$ TeV. Measurements of the differential cross-section and the forwardbackward production ratio are reported for Λ c + baryons with transverse momenta in the range 2 < p T < 10 GeV/c and rapidities in the ranges 1.5 < y ∗ < 4.0 and −4.5 < y ∗ < −2.5 in the nucleon-nucleon centre-of-mass system. The ratio of cross-sections of Λ c + baryons and D 0 mesons is also reported. The results are compared with next-to-leading order calculations that use nuclear parton distribution functions.Aaij, R.Mon, 18 Feb 2019 20:22:14 GMThttps://repo.scoap3.org/record/31052urn:ISSN:1029-8479Springer/SISSA2019-02-15Observation of Two Resonances in the <math><msubsup><mi>Λ</mi><mi>b</mi><mn>0</mn></msubsup><msup><mi>π</mi><mo>±</mo></msup></math> Systems and Precise Measurement of <math><msubsup><mi>Σ</mi><mi>b</mi><mo>±</mo></msubsup></math> and <math><msubsup><mi>Σ</mi><mi>b</mi><mrow><mo>*</mo><mo>±</mo></mrow></msubsup></math> Properties
https://repo.scoap3.org/record/30225
The first observation of two structures consistent with resonances in the final states Λb0π− and Λb0π+ is reported using samples of pp collision data collected by the LHCb experiment at s=7 and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. The ground states Σb± and Σb*± are also confirmed and their masses and widths are precisely measured.Aaij, R.Fri, 11 Jan 2019 15:17:58 GMThttps://repo.scoap3.org/record/30225urn:ISSN:1079-7114APS2019-01-11Measurement of the Charm-Mixing Parameter <math><msub><mi>y</mi><mrow><mi>C</mi><mi>P</mi></mrow></msub></math>
https://repo.scoap3.org/record/30222
A measurement of the charm-mixing parameter yCP using D0→K+K−, D0→π+π−, and D0→K−π+ decays is reported. The D0 mesons are required to originate from semimuonic decays of B− and B¯0 mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb−1. The yCP parameter is measured to be (0.57±0.13(stat)±0.09(syst))%, in agreement with, and as precise as, the current world-average value.Aaij, R.Fri, 11 Jan 2019 15:17:46 GMThttps://repo.scoap3.org/record/30222urn:ISSN:1079-7114APS2019-01-08