# EP Articles

Nyeste elementer:
2022-09-02
14:26
 First measurement of $Z \to \mu^+\mu^-$ angular coefficients in the forward region of $pp$ collisions at $\sqrt{s} = 13$ TeV / LHCb Collaboration The first study of the angular distribution of $\mu^+ \mu^-$ pairs produced in the forward rapidity region via the Drell-Yan reaction $pp \rightarrow \gamma^{*}/Z +X \rightarrow l^+ l^- + X$ is presented, using data collected with the LHCb detector at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.1 $\rm{fb}^{-1}$. The coefficients of the five leading terms in the angular distribution are determined as a function of the dimuon transverse momentum and rapidity. [...] arXiv:2203.01602; LHCb-PAPER-2021-048; CERN-EP-2022-030; LHCB-PAPER-2021-048.- 2022-08-24 - 11 p. - Published in : Phys. Rev. Lett. 129 (2022) 091801 Fulltext: 2203.01602 - PDF; LHCb-PAPER-2021-037-paper - PDF; Related data file(s): ZIP; External link: Previous draft version

2022-02-21
17:10
 Measurement of the charm mixing parameter $y_{CP} - y_{CP}^{K\pi}$ using two-body $D^0$ meson decays / LHCb Collaboration A measurement of the ratios of the effective decay widths of $D^0 \to \pi^-\pi^+$ and $D^0 \to K^-K^+$ decays over that of $D^0 \to K^-\pi^+$ decays is performed with the LHCb experiment using proton-proton collisions at a centre-of-mass energy of $13\,\mathrm{TeV}$, corresponding to an integrated luminosity of $6\,\mathrm{fb^{-1}}$. These observables give access to the charm mixing parameters $y_{CP}^{\pi\pi} - y_{CP}^{K\pi}$ and $y_{CP}^{KK} - y_{CP}^{K\pi}$, and are measured as $y_{CP}^{\pi\pi} - y_{CP}^{K\pi} = (6.57 \pm 0.53 \pm 0.16) \times 10^{-3}$, $y_{CP}^{KK} - y_{CP}^{K\pi} = (7.08 \pm 0.30 \pm 0.14) \times 10^{-3}$, where the first uncertainties are statistical and the second systematic. [...] arXiv:2202.09106; LHCb-PAPER-2021-041; CERN-EP-2022-022; LHCB-PAPER-2021-041.- 2022-05-01 - 27 p. - Published in : Phys. Rev. D 105 (2022) 092013 Fulltext: PhysRevD.105.092013 - PDF; 2202.09106 - PDF; LHCb-PAPER-2021-041 - PDF; Related data file(s): ZIP; Supplementary information: ZIP;

2022-02-18
14:54
 Observation of the doubly charmed baryon decay ${\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+}$ / LHCb Collaboration The $\it{\Xi_{cc}^{++}\to \Xi_{c}^{'+}\pi^{+}}$ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of $13\mathrm{\,Te\kern -0.1em V}$, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. The $\it{\Xi_{cc}^{++}\to \Xi_{c}^{'+}\pi^{+}}$ decay is reconstructed partially, where the photon from the $\it{\Xi_{c}^{'+} \to \Xi_{c}^{+}\gamma}$ decay is not reconstructed and the $pK^-\pi^+$ final state of the $\it{\Xi_{c}^{+}}$ baryon is employed. [...] arXiv:2202.05648; LHCb-PAPER-2021-052; CERN-EP-2022-016.- 2022-05-06 - 19 p. - Published in : JHEP 2205 (2022) 038 Fulltext: LHCb-PAPER-2021-052_to_arXiv_ - PDF; document - PDF; 2202.05648 - PDF; Related data file(s): ZIP; Supplementary information: ZIP;

2022-02-10
15:35
 Study of charmonium and charmonium-like contributions in $B^+ \rightarrow J/\psi \eta K^+$ decays / LHCb Collaboration A study of $B^+ \rightarrow J/\psi \eta K^+$ decays, followed by $J/\psi \rightarrow \mu^+ \mu^-$ and $\eta \rightarrow \gamma \gamma$, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{-1}$. The $J/\psi\eta$ mass spectrum is investigated for contributions from charmonia and charmonium-like states. [...] arXiv:2202.04045; CERN-EP-2022-009; LHCb-PAPER-2021-047; LHCB-PAPER-2021-047.- Geneva : CERN, 2022 - 31 p. - Published in : JHEP 2022 (2020) 046 Fulltext: PDF; Related data file(s): LHCb-PAPER-2021-047-figures - ZIP; LHCb-PAPER-2021-047 - PDF;

2022-01-10
15:35
 Observation of the decay $\Lambda_b^0\rightarrow \Lambda_c^+\tau^-\overline{\nu}_{\tau}$ / LHCb Collaboration The first observation of the semileptonic $b$-baryon decay $\Lambda_b^0 \rightarrow \Lambda_c^+ \tau^-\overline{\nu}_{\tau}$, with a significance of $6.1\,\sigma$, is reported using a data sample corresponding to 3 fb$^{-1}$ of integrated luminosity, collected by the LHCb experiment at centre-of-mass energies of 7 and 8~TeV at the LHC. The $\tau^-$ lepton is reconstructed in the hadronic decay to three charged pions. [...] arXiv:2201.03497; LHCb-PAPER-2021-044; CERN-EP-2021-265; LHCB-PAPER-2021-044.- Geneva : CERN, 2022-05-13 - 21 p. - Published in : Phys. Rev. Lett. 128 (2022) 191803 Fulltext: 2201.03497 - PDF; PhysRevLett.128.191803 - PDF; Related data file(s): ZIP; Supplementary material: ZIP;

2022-01-07
13:56
 Observation of the $B^0\rightarrow\overline{D}^{*0}K^{+}\pi^{-}$ and $B_s^0\rightarrow\overline{D}^{*0}K^{-}\pi^{+}$ decays / LHCb Collaboration The first observations of $B^0\rightarrow\overline{D}^{*}(2007)^{0}K^{+}\pi^{-}$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^{0}K^{-}\pi^{+}$ decays are presented, and their branching fractions relative to that of the $B^0\rightarrow\overline{D}^{*}(2007)^{0}\pi^{+}\pi^{-}$ decay are reported. These modes can potentially be used to investigate the spectroscopy of charm and charm-strange resonances and to determine the angle $\gamma$ of the CKM unitarity triangle. [...] arXiv:2112.11428; LHCb-PAPER-2021-043; CERN-EP-2021-262; LHCB-PAPER-2021-043.- Geneva : CERN, 2022-04-01 - 32 p. - Published in : Phys. Rev. D 105 (2022) 072005 Fulltext: LHCb-PAPER-2021-043 - PDF; 2112.11428 - PDF; Publication - PDF; Related data file(s): ZIP;

2022-01-05
13:53
 Constraints on the CKM angle $\gamma$ from $B^\pm\rightarrow Dh^\pm$ decays using $D\rightarrow h^\pm h^{\prime\mp}\pi^0$ final states / LHCb Collaboration A data sample collected with the LHCb detector, corresponding to an integrated luminosity of $9~{\rm fb}^{-1}$, is used to measure $CP$ observables in $B^\pm \to D h^\pm$ decays, where $h^{(\prime)}$ is either a kaon or a pion, and the neutral $D$ meson decay is reconstructed in the three-body final states $K^\pm \pi^\mp \pi^0$, $\pi^\pm \pi^\mp \pi^0$, and $K^\pm K^\mp \pi^0$. The most suppressed of these modes, $B^\pm \to [\pi^\pm K^\mp \pi^0]_D K^\pm$, is observed with a significance greater than seven standard deviations and constraints on the CKM angle $\gamma$ are calculated from the combination of the measurements.. arXiv:2112.10617; LHCb-PAPER-2021-036; CERN-EP-2021-255; LHCB-PAPER-2021-036.- Geneva : CERN, 2022-07-15 - 24 p. - Published in : JHEP 2207 (2022) 099 Fulltext: LHCb-PAPER-2021-036 - PDF; document - PDF; 2112.10617 - PDF; Related data file(s): ZIP;

2021-12-15
11:01
 Precision measurement of forward $Z$ boson production in proton-proton collisions at $\sqrt{s} = 13$ TeV / LHCb Collaboration A precision measurement of the $Z$ boson production cross-section at $\sqrt{s} = 13$ TeV in the forward region is presented, using $pp$ collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb$^{-1}$. The production cross-section is measured using $Z\rightarrow\mu^+\mu^-$ events within the fiducial region defined as pseudorapidity $2.0<\eta<4.5$ and transverse momentum $p_{T}>20$ GeV/$c$ for both muons and dimuon invariant mass $60 < M_{\mu\mu}<120$ GeV/$c^2$. [...] arXiv:2112.07458; LHCb-PAPER-2021-037; CERN-EP-2021-246; LHCB-PAPER-2021-037.- Geneva : CERN, 2022-07-05 - 57 p. - Published in : JHEP 2207 (2022) 026 Fulltext: LHCb-PAPER-2021-037 - PDF; 2112.07458 - PDF; Related data file(s): ZIP;

2021-12-06
12:17
 Observation of $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ decays / LHCb Collaboration The multihadron decays $\Lambda_b^0\rightarrow D^+ p \pi^-\pi^-$ and $\Lambda_b^0\rightarrow D^{*+} p \pi^-\pi^-$ are observed in data corresponding to an integrated luminosity of 3fb$^{-1}$, collected in proton-proton collisions at centre-of-mass energies of 7 and 8TeV by the LHCb detector. Using the decay $\Lambda_b^0\rightarrow \Lambda_c^+ \pi^+ \pi^-\pi^-$ as a normalisation channel, the ratio of branching fractions is measured to be arXiv:2112.02013; LHCb-PAPER-2021-040; CERN-EP-2021-237; LHCB-PAPER-2021-040.- Geneva : CERN, 2022-03-23 - 30 p. - Published in : JHEP 2203 (2022) 153 Fulltext: LHCb-PAPER-2021-040 - PDF; document - PDF; 2112.02013 - PDF; Related data file(s): ZIP;

2021-11-23
12:08
 Measurement of the photon polarization in $\Lambda_{b}^{0}$ $\to$ $\Lambda$ $\gamma$ decays / LHCb Collaboration The photon polarization in $b\to s\gamma$ transitions is measured for the first time in radiative b-baryon decays exploiting the unique spin structure of $\Lambda_{b}^{0}\to\Lambda\gamma$ decays. A data sample corresponding to an integrated luminosity of $6\;\mathrm{fb^{-1}}$ collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of $13\;\mathrm{TeV}$ is used. [...] arXiv:2111.10194; LHCb-PAPER-2021-030; CERN-EP-2021-230.- 2022-03-01 - 11 p. - Published in : Phys. Rev. D 105 (2022) L051104 Fulltext: 2111.10194 - PDF; Lb2L0Gamma_Angular_Paper - PDF; Related data file(s): ZIP; Supplementary information: ZIP;