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Model-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:1079-7114APS2019-01-08Evidence for an ηc(1S)π- resonance in B0→ηc(1S)K+π- decays
https://repo.scoap3.org/record/29859
A Dalitz plot analysis of B0→ηc(1S)K+π- decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of s=7,8 and 13TeV , corresponding to a total integrated luminosity of 4.7fb-1 . A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S)π- resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096±20-22+18MeV and 152±58-35+60MeV , respectively. The spin-parity assignments JP=0+ and JP=1- are both consistent with the data. In addition, the first measurement of the B0→ηc(1S)K+π- branching fraction is performed and gives B(B0→ηc(1S)K+π-)=(5.73±0.24±0.13±0.66)×10-4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions.Aaij, R.Mon, 17 Dec 2018 13:33:25 GMThttps://repo.scoap3.org/record/29859urn:ISSN:1434-6052Springer/Società Italiana di Fisica2018-12-17Study of ϒ production in p Pb collisions at s N N = 8.16 $$ \sqrt{s_{\mathrm{NN}}}=8.16 $$ TeV
https://repo.scoap3.org/record/29774
The production of ϒ ( nS ) mesons ( n = 1, 2, 3) in p Pb and Pb p collisions at a centre-of-mass energy per nucleon pair s N N = 8.16 $$ \sqrt{s_{\mathrm{NN}}}=8.16 $$ TeV is measured by the LHCb experiment, using a data sample corresponding to an integrated luminosity of 31.8 nb −1 . The ϒ ( nS ) mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the ϒ (1 S ) and ϒ (2 S ) states, their forward-to-backward ratios and nuclear modification factors. The measurements are performed as a function of the transverse momentum p T and rapidity in the nucleon-nucleon centre-of-mass frame y * of the ϒ ( nS ) states, in the kinematic range p T < 25 GeV/ c and 1.5 < y * < 4.0 (−5.0 < y * < −2.5) for p Pb (Pb p ) collisions. In addition, production cross-sections for ϒ (3 S ) are measured integrated over phase space and the production ratios between all three ϒ ( nS ) states are determined. Suppression for bottomonium in proton-lead collisions is observed, which is particularly visible in the ratios. The results are compared to theoretical models.Aaij, R.Fri, 14 Dec 2018 13:23:15 GMThttps://repo.scoap3.org/record/29774urn:ISSN:1029-8479Springer/SISSA2018-11-29Search for lepton-flavour-violating decays of Higgs-like bosons
https://repo.scoap3.org/record/29701
A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/c2 decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV , collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1 . The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/c2 to 4 pb for a mass of 195 GeV/c2 .Aaij, R.Thu, 13 Dec 2018 14:44:42 GMThttps://repo.scoap3.org/record/29701urn:ISSN:1434-6052Springer/Società Italiana di Fisica2018-12-12Measurement of Antiproton Production in <math><mrow><mi>p</mi><mtext>−</mtext><mi>He</mi></mrow></math> Collisions at <math><mrow><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>110</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>
https://repo.scoap3.org/record/29588
The cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set corresponding to an integrated luminosity of 0.5 nb−1. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV/c, represent the first direct determination of the antiproton production cross section in p−He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.Aaij, R.Mon, 03 Dec 2018 17:19:30 GMThttps://repo.scoap3.org/record/29588urn:ISSN:1079-7114APS2018-11-29Measurement of the time-integrated CP asymmetry in D 0 → K S 0 K S 0 decays
https://repo.scoap3.org/record/29138
A measurement of the time-integrated CP asymmetry in D 0 → K S 0 K S 0 decays is reported. The data correspond to an integrated luminosity of about 2 fb −1 collected in 2015–2016 by the LHCb collaboration in pp collisions at a centre-of-mass energy of 13 TeV. The D 0 candidate is required to originate from a D *+ → D 0 π + decay, allowing the determination of the flavour of the D 0 meson using the pion charge. The D 0 → K + K − decay, which has a well measured CP asymmetry, is used as a calibration channel. The CP asymmetryfor D 0 → K S 0 K S 0 is measured to be A C P D 0 → K S 0 K S 0 = 4.3 ± 3.4 ± 1.0 % , $$ {\mathcal{A}}^{CP}\left({D}^0\to {K}_S^0{K}_S^0\right)=\left(4.3\pm 3.4\pm 1.0\right)\%, $$ where the first uncertainty is statistical and the second is systematic. This result is combined with the previous LHCb measurement at lower centre-of-mass energies to obtain A C P D 0 → K S 0 K S 0 = 2.3 ± 2.8 ± 0.9 % . $$ {\mathcal{A}}^{CP}\left({D}^0\to {K}_S^0{K}_S^0\right)=\left(2.3\pm 2.8\pm 0.9\right)\%. $$Aaij, R.Tue, 13 Nov 2018 04:20:31 GMThttps://repo.scoap3.org/record/29138urn:ISSN:1029-8479Springer/SISSA2018-11-08Observation of the decay <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo>→</mo><msup><mrow><mover><mrow><mi>D</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math>
https://repo.scoap3.org/record/29003
The first observation of the Bs0→D¯0K+K− decay is reported, together with the most precise branching fraction measurement of the mode B0→D¯0K+K−. The results are obtained from an analysis of pp collision data corresponding to an integrated luminosity of 3.0 fb−1. The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction of the B0→D¯0K+K− decay is measured relative to that of the decay B0→D¯0π+π− to be B(B0→D¯0K+K−)B(B0→D¯0π+π−)=(6.9±0.4±0.3)%, where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the Bs0→D¯0K+K− decay mode relative to that of the corresponding B0 decay is B(Bs0→D¯0K+K−)B(B0→D¯0K+K−)=(93.0±8.9±6.9)%. Using the known branching fraction of B0→D¯0π+π−, the values of B(B0→D¯0K+K−)=(6.1±0.4±0.3±0.3)×10−5 and B(Bs0→D¯0K+K−)=(5.7±0.5±0.4±0.5)×10−5 are obtained, where the third uncertainties arise from the branching fraction of the decay modes B0→D¯0π+π− and B0→D¯0K+K−, respectively.Aaij, R.Tue, 06 Nov 2018 13:18:41 GMThttps://repo.scoap3.org/record/29003urn:ISSN:2470-0029APS2018-10-31Observation of <math><mrow><msubsup><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo>→</mo><msup><mrow><mover><mrow><mi>D</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mo>*</mo><mn>0</mn></mrow></msup><mi>ϕ</mi></mrow></math> and search for <math><msup><mi>B</mi><mn>0</mn></msup><mo>→</mo><msup><mover><mi>D</mi><mo>¯</mo></mover><mn>0</mn></msup><mi>ϕ</mi></math> decays
https://repo.scoap3.org/record/28896
The first observation of the Bs0→D¯*0ϕ decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3 fb−1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B0→D¯0π+π− and is found to be B(Bs0→D¯*0ϕ)=(3.7±0.5±0.3±0.2)×10−5, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B0→D¯0π+π− decay. The fraction of longitudinal polarization in this decay is measured to be fL=(73±15±4)%. The most precise determination of the branching fraction for the Bs0→D¯0ϕ decay is also obtained, B(Bs0→D¯0ϕ)=(3.0±0.3±0.2±0.2)×10−5. An upper limit, B(B0→D¯0ϕ)<2.0 (2.3)×10−6 at 90% (95%) confidence level is set. A constraint on the ω−ϕ mixing angle δ is set at |δ|<5.2° (5.5°) at 90% (95%) confidence level.Aaij, R.Tue, 30 Oct 2018 21:16:10 GMThttps://repo.scoap3.org/record/28896urn:ISSN:2470-0029APS2018-10-30Central exclusive production of J/ψ and ψ (2 S ) mesons in pp collisions at s = 13 $$ \sqrt{s}=13 $$ TeV
https://repo.scoap3.org/record/28813
Measurements are reported of the central exclusive production of J/ψ and ψ (2 S ) mesons in pp collisions at a centre-of-mass energy of 13 TeV. Backgrounds are significantly reduced compared to previous measurements made at lower energies through the use of new forward shower counters. The products of the cross-sections and the branching fractions for the decays to dimuons, where both muons are within the pseudorapidity range 2 . 0 < η < 4 . 5, are measured to beAaij, R.Sat, 27 Oct 2018 23:20:09 GMThttps://repo.scoap3.org/record/28813urn:ISSN:1029-8479Springer/SISSA2018-10-26Search for CP violation in Λb0→pK− and Λb0→pπ− decays
https://repo.scoap3.org/record/28754
A search for CP violation in Λb0→pK− and Λb0→pπ− decays is presented using a sample of pp collisions collected with the LHCb detector and corresponding to an integrated luminosity of 3.0 fb−1 . The CP -violating asymmetries are measured to be ACPpK−=−0.020±0.013±0.019 and ACPpπ−=−0.035±0.017±0.020 , and their difference ACPpK−−ACPpπ−=0.014±0.022±0.010 , where the first uncertainties are statistical and the second systematic. These are the most precise measurements of such asymmetries to date.Aaij, R.Wed, 24 Oct 2018 16:08:29 GMThttps://repo.scoap3.org/record/28754urn:ISSN:0370-2693Elsevier2018-12-10Erratum to: Measurement of the CKM angle γ using B ± → DK ± with D → K S 0 π + π − , K S 0 K + K − decays
https://repo.scoap3.org/record/28709
The B + and B − labels of the confidence regions in figure 10 of the original paper [1] were erroneously swapped. The corrected figure is shown in figure 10.Aaij, R.Sat, 20 Oct 2018 04:06:39 GMThttps://repo.scoap3.org/record/28709urn:ISSN:1029-8479Springer/SISSA2018-10-16First Observation of the Doubly Charmed Baryon Decay <math><msubsup><mi>Ξ</mi><mrow><mi>c</mi><mi>c</mi></mrow><mrow><mo>+</mo><mo>+</mo></mrow></msubsup><mo>→</mo><msubsup><mi>Ξ</mi><mi>c</mi><mo>+</mo></msubsup><msup><mi>π</mi><mo>+</mo></msup></math>
https://repo.scoap3.org/record/28665
The doubly charmed baryon decay Ξcc++→Ξc+π+ is observed for the first time, with a statistical significance of 5.9σ, confirming a recent observation of the baryon in the Λc+K−π+π+ final state. The data sample used corresponds to an integrated luminosity of 1.7 fb−1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 13 TeV. The Ξcc++ mass is measured to be 3620.6±1.5(stat)±0.4(syst)±0.3(Ξc+) MeV/c2 and is consistent with the previous result. The ratio of branching fractions between the decay modes is measured to be [B(Ξcc++→Ξc+π+)×B(Ξc+→pK−π+)]/[B(Ξcc++→Λc+K−π+π+)×B(Λc+→pK−π+)]=0.035±0.009(stat)±0.003(syst).Aaij, R.Thu, 18 Oct 2018 00:16:19 GMThttps://repo.scoap3.org/record/28665urn:ISSN:1079-7114APS2018-10-17Search for beautiful tetraquarks in the ϒ (1 S ) μ + μ − invariant-mass spectrum
https://repo.scoap3.org/record/28593
The ϒ (1 S ) μ + μ − invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two b ¯ $$ \overline{b} $$ quarks, X b b ¯ b b ¯ $$ {X}_{b\overline{b}b\overline{b}} $$ . The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies s = 7 $$ \sqrt{s}=7 $$ , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb −1 . No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the X b b ¯ b b ¯ $$ {X}_{b\overline{b}b\overline{b}} $$ state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range [2 . 0 , 5 . 0], and the X b b ¯ b b ¯ $$ {X}_{b\overline{b}b\overline{b}} $$ state has rapidity in the range [2 . 0 , 4 . 5] and transverse momentum less than 15 GeV/ c .Aaij, R.Mon, 15 Oct 2018 20:50:03 GMThttps://repo.scoap3.org/record/28593urn:ISSN:1029-8479Springer/SISSA2018-10-12Measurement of Z → τ + τ − production in proton-proton collisions at s = 8 $$ \sqrt{\mathrm{s}}=8 $$ TeV
https://repo.scoap3.org/record/28303
A measurement of Z → τ + τ − production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb −1 , from pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV collected by the LHCb experiment. The τ + τ − candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for Z bosons with invariant mass between 60 and 120 GeV /c 2 , which decay to tau leptons with transverse momenta greater than 20 GeV /c and pseudorapidities between 2.0 and 4.5. The cross-section is determined to be σ pp → Z → τ + τ − = 95.8 ± 2.1 ± 4.6 ± 0.2 ± 1.1 $$ {\sigma}_{pp}{{}_{\to Z\to {\tau}^{+}}}_{\tau^{-}}=95.8 \pm 2.1 \pm 4.6 \pm 0.2 \pm 1.1 $$ pb, where the first uncertainty is statistical, the second is systematic, the third is due to the LHC beam energy uncertainty, and the fourth to the integrated luminosity uncertainty. This result is compatible with NNLO Standard model predictions. The ratio of the cross-sections for Z → τ + τ − to Z → μ + μ − ( Z → e + e − ), determined to be 1 . 01 ± 0 . 05 (1 . 02 ± 0 . 06), is consistent with the lepton-universality hypothesis in Z decays.Aaij, R.Sat, 29 Sep 2018 10:32:34 GMThttps://repo.scoap3.org/record/28303urn:ISSN:1029-8479Springer/SISSA2018-09-27Angular moments of the decay Λ b 0 → Λ μ + μ − at low hadronic recoil
https://repo.scoap3.org/record/28301
An analysis of the angular distribution of the decay Λ b 0 → Λ μ + μ − is presented, using data collected with the LHCb detector between 2011 and 2016 and corresponding to an integrated luminosity of approximately 5 fb −1 . Angular observables are determined using a moment analysis of the angular distribution at low hadronic recoil, corresponding to the dimuon invariant mass squared range 15 < q 2 < 20 GeV 2 / c 4 . The full basis of observables is measured for the first time. The lepton-side, hadron-side and combined forward-backward asymmetries of the decay are determined to be A F B ℓ = − 0.39 ± 0.04 stat ± 0.01 syst , A F B h = − 0.30 ± 0.05 stat ± 0.02 syst , A F B ℓ h = + 0.25 ± 0.04 stat ± 0.01 syst . $$ \begin{array}{l}{A}_{\mathrm{FB}}^{\ell }=-0.39\pm 0.04\left(\mathrm{stat}\right)\pm 0.01\left(\mathrm{syst}\right),\hfill \\ {}{A}_{\mathrm{FB}}^h=-0.30\pm 0.05\left(\mathrm{stat}\right)\pm 0.02\left(\mathrm{syst}\right),\hfill \\ {}{A}_{\mathrm{FB}}^{\ell h}=+0.25\pm 0.04\left(\mathrm{stat}\right)\pm 0.01\left(\mathrm{syst}\right).\hfill \end{array} $$Aaij, R.Sat, 29 Sep 2018 10:32:26 GMThttps://repo.scoap3.org/record/28301urn:ISSN:1029-8479Springer/SISSA2018-09-26