Showing papers by "C. Santamarina Rios published in 2022"
TL;DR: In this article , an exotic narrow state in the D 0 D 0 π + mass spectrum was reported, which lies just below the D *+ D 0 mass threshold produced in proton-proton collisions at the Large Hadron Collider.
Abstract: Abstract 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 D 0 D 0 π + mass spectrum just below the D *+ D 0 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 $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + tetraquark with a quark content of $${{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}\overline{{{{{{\rm{u}}}}}}}\overline{{{{{{\rm{d}}}}}}}$$ c c u ¯ d ¯ and spin-parity quantum numbers J P = 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 D 0 π + 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 $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + 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 $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.
67 citations
TL;DR: In this paper , an exotic narrow state in the D 0 D 0 π + mass spectrum was reported, which lies just below the D *+ D 0 mass threshold produced in proton-proton collisions at the Large Hadron Collider.
Abstract: Abstract 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 D 0 D 0 π + mass spectrum just below the D *+ D 0 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 $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + tetraquark with a quark content of $${{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}\overline{{{{{{\rm{u}}}}}}}\overline{{{{{{\rm{d}}}}}}}$$ c c u ¯ d ¯ and spin-parity quantum numbers J P = 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 D 0 π + 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 $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + 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 $${{{{{{\rm{T}}}}}}}_{{{{{{\rm{c}}}}}}{{{{{\rm{c}}}}}}}^{+}$$ T c c + state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.
67 citations
TL;DR: In this article , the first observation of lepton universality in B0→KS0e+e− and B+→K*+e + e+e+ e− decays is reported, where ℓ is either an electron or a muon.
Abstract: Tests of lepton universality in B0→KS0ℓ+ℓ− and B+→K*+ℓ+ℓ− decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B0→KS0e+e− and B+→K*+e+e− decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1 . The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B0→KS0e+e− and B+→K*+e+e− decays is reported.Received 19 October 2021Accepted 29 March 2022DOI:https://doi.org/10.1103/PhysRevLett.128.191802Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2022 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasBranching fractionFlavor changing neutral currentsLeptonic, semileptonic & radiative decaysParticle decaysParticle phenomenaRare decaysParticles & Fields
27 citations
TL;DR: In this paper , an improved measurement of the decay B 0 s → μ þ μ − and searches for the decays B 0 → ε − ε → δ − γ are performed at the LHCb experiment using data collected in proton-proton collisions at s p ¼ 7, 8 and 13 TeV.
Abstract: An improved measurement of the decay B 0 s → μ þ μ − and searches for the decays B 0 → μ þ μ − and B 0 s → μ þ μ − γ are performed at the LHCb experiment using data collected in proton-proton collisions at ffiffiffi s p ¼ 7 , 8 and 13 TeV, corresponding to integrated luminosities of 1, 2 and 6 fb − 1 , respectively. The B 0 s → μ þ μ − branching fraction and effective lifetime are measured to be B ð B 0 s → μ þ μ − Þ ¼ ð 3 . 09 þ 0 . 46 þ 0 . 15 − 0 . 43 − 0 . 11 Þ × 10 − 9 and τ ð B 0 s → μ þ μ − Þ ¼ ð 2 . 07 (cid:2) 0 . 29 (cid:2) 0 . 03 Þ ps, respectively, where the uncertainties include both statistical and systematic contributions. No significant signal for B 0 → μ þ μ − and B 0 s → μ þ μ − γ decays is found and the upper limits B ð B 0 → μ þ μ − Þ < 2 . 6 × 10 − 10 and B ð B 0 s → μ þ μ − γ Þ < 2 . 0 × 10 − 9 at 95% confidence level are determined, where the latter is limited to the range m μμ > 4 . 9 GeV =c 2 . Additionally, the ratio between the B 0 → μ þ μ − and B 0 s → μ þ μ − branching fractions is measured to be R μ þ μ − < 0 . 095 at 95% confidence level. The results are in agreement with the Standard Model predictions. DOI: 10.1103/PhysRevD.105.012010
27 citations
TL;DR: The first observation of the semileptonic b-baryon decay with a significance of 6.1σ was reported using a data sample corresponding to 3 fb−1 of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the CERN as discussed by the authors .
Abstract: The first observation of the semileptonic b-baryon decay Λb0→Λc+τ−ν¯τ, with a significance of 6.1σ, is reported using a data sample corresponding to 3 fb−1 of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The τ− lepton is reconstructed in the hadronic decay to three charged pions. The ratio K=B(Λb0→Λc+τ−ν¯τ)/B(Λb0→Λc+π−π+π−) is measured to be 2.46±0.27±0.40, where the first uncertainty is statistical and the second systematic. The branching fraction B(Λb0→Λc+τ−ν¯τ)=(1.50±0.16±0.25±0.23)% is obtained, where the third uncertainty is from the external branching fraction of the normalization channel Λb0→Λc+π−π+π−. The ratio of semileptonic branching fractions R(Λc+)≡B(Λb0→Λc+τ−ν¯τ)/B(Λb0→Λc+μ−ν¯μ) is derived to be 0.242±0.026±0.040±0.059, where the external branching fraction uncertainty from the channel Λb0→Λc+μ−ν¯μ contributes to the last term. This result is in agreement with the standard model prediction.Received 11 January 2022Accepted 29 March 2022DOI:https://doi.org/10.1103/PhysRevLett.128.191803Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2022 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasLeptonic, semileptonic & radiative decaysPhysical SystemsBottom baryonsHadron collidersPropertiesFlavor symmetriesParticles & Fields
15 citations
TL;DR: In this article , two narrow resonant states are observed in the Λ_{b}^{0}K^{-}π^{+} mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment.
Abstract: Two narrow resonant states are observed in the Λ_{b}^{0}K^{-}π^{+} mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb^{-1}. The minimal quark content of the Λ_{b}^{0}K^{-}π^{+} system indicates that these are excited Ξ_{b}^{0} baryons. The masses of the Ξ_{b}(6327)^{0} and Ξ_{b}(6333)^{0} states are m[Ξ_{b}(6327)^{0}]=6327.28_{-0.21}^{+0.23}±0.12±0.24 and m[Ξ_{b}(6333)^{0}]=6332.69_{-0.18}^{+0.17}±0.03±0.22 MeV, respectively, with a mass splitting of Δm=5.41_{-0.27}^{+0.26}±0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λ_{b}^{0} mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξ_{b}(6327)^{0}]<2.20(2.56) and Γ[Ξ_{b}(6333)^{0}]<1.60(1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξ_{b}^{0} resonances.
6 citations
TL;DR: In this article , the authors presented ameasurement of deltams using B0s2DsPi decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider.
Abstract: Mesons comprising a beauty quark and a strange quark can oscillate between particle (B0s) and antiparticle (B0s) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, deltams. Here we present ameasurement of deltams using B0s2DsPi decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be deltams = 17.7683 +- 0.0051 +- 0.0032 ps-1, where the first uncertainty is statistical and the second systematic. This measurement improves upon the current deltams precision by a factor of two. We combine this result with previous LHCb measurements to determine deltams = 17.7656 +- 0.0057 ps-1, which is the legacy measurement of the original LHCb detector.
6 citations
TL;DR: In this paper , the authors presented ameasurement of deltams using B0s2DsPi decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider.
Abstract: Mesons comprising a beauty quark and a strange quark can oscillate between particle (B0s) and antiparticle (B0s) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, deltams. Here we present ameasurement of deltams using B0s2DsPi decays produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be deltams = 17.7683 +- 0.0051 +- 0.0032 ps-1, where the first uncertainty is statistical and the second systematic. This measurement improves upon the current deltams precision by a factor of two. We combine this result with previous LHCb measurements to determine deltams = 17.7656 +- 0.0057 ps-1, which is the legacy measurement of the original LHCb detector.
6 citations
TL;DR: In this paper , a coherent production of J/ψ mesons was studied in ultra-peripheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of about 10 μb −1 .
Abstract: A bstract Coherent production of J/ψ mesons is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of about 10 μb −1 . The J/ψ mesons are reconstructed in the dimuon final state and are required to have transverse momentum below 1 GeV. The cross-section within the rapidity range of 2 . 0 < y < 4 . 5 is measured to be 4 . 45 ± 0 . 24 ± 0 . 18 ± 0 . 58 mb, where the first uncertainty is statistical, the second systematic and the third originates from the luminosity determination. The cross-section is also measured in J/ψ rapidity intervals. The results are compared to predictions from phenomenological models.
5 citations
TL;DR: In this paper , a measurement of the lifetimes of the X 0 c and N 0 c baryons is reported using proton-proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 : 4 fb (cid:1) 1 collected by the LHCb experiment.
Abstract: A measurement of the lifetimes of the X 0 c and N 0 c baryons is reported using proton–proton collision data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 : 4 fb (cid:1) 1 collected by the LHCb experiment. The X 0 c and N 0 c baryons are produced directly from proton interactions and recon- structed in the pK (cid:1) K (cid:1) p þ final state. The X 0 c lifetime is measured to be 276 : 5 (cid:3) 13 : 4 (cid:3) 4 : 4 (cid:3) 0 : 7 fs, and the N 0 c lifetime is measured to be 148 : 0 (cid:3) 2 : 3 (cid:3) 2 : 2 (cid:3) 0 : 2 fs, where the first uncertainty is statistical, the sec- ond systematic, and the third due to the uncertainty on the D 0 lifetime. These results confirm previous LHCb measurements based on semileptonic beauty-hadron decays, which disagree with earlier results of a four times shorter X 0 c lifetime, and provide the single most precise measurement of the X 0 c lifetime.
5 citations
TL;DR: In this article , the production of prompt charged particles in proton-lead collisions at the LHCb as a function of pseudorapidity (η) and transverse momentum (pT) with respect to the proton beam direction was investigated.
Abstract: The production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon center-of-mass energy sNN=5 TeV is studied at LHCb as a function of pseudorapidity (η) and transverse momentum (pT) with respect to the proton beam direction. The nuclear modification factor for charged particles is determined as a function of η between −4.8<η<−2.5 (backward region) and 2.0<η<4.8 (forward region), and pT between 0.2
23 Mar 2022
TL;DR: The photon polarization in radiative b-baryon decays exploiting the unique spin structure of Lambda_b \to \Lambda \gamma$ decays was measured for the first time in this paper .
Abstract: 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 $\Lambda_b \to \Lambda \gamma$ decays. A data sample corresponding to an integrated luminosity of $6\;fb^{-1}$ collected by the LHCb experiment in $pp$ collisions at a center-of-mass energy of $13\;TeV$ is used. The photon polarization is measured to be $\alpha_{\gamma}= 0.82^{\,+\,0.17\,+\,0.04}_{\,-\,0.26\,-\,0.13}$, where the first uncertainty is statistical and the second systematic. This result is in agreement with the Standard Model prediction and previous measurements in b-meson decays. Charge-parity breaking effects are studied for the first time in this observable and found to be consistent with $CP$ symmetry.
TL;DR: In this article , the angular distribution of the Drell-Yan reaction in the forward rapidity region was studied using data collected with the LHCb detector at a center-of-mass energy of 13-TeV, corresponding to an integrated luminosity of 5.1
Abstract: The first study of the angular distribution of μ^{+}μ^{-} pairs produced in the forward rapidity region via the Drell-Yan reaction pp→γ^{*}/Z+X→ℓ^{+}ℓ^{-}+X is presented, using data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 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. The results are compared to various theoretical predictions of the Z-boson production mechanism and can also be used to probe transverse-momentum-dependent parton distributions within the proton.
25 May 2022
TL;DR: In this article , a measurement of the effective decay widths of the LHCb experiment using proton-proton collisions at a centre-of-mass energy of $13 \, \mathrm{TeV} , corresponding to an integrated luminosity of $6 \,
Abstract: 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. The combination of the two measurements is $y_{CP} - y_{CP}^{K\pi} = (6.96 \pm 0.26 \pm 0.13) \times 10^{-3}$, which is four times more precise than the previous world average.
TL;DR: In this paper , the angular distribution of μ+μ− pairs produced in the forward rapidity region via the Drell-Yan reaction was studied using data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb−1.
Abstract: The first study of the angular distribution of μ+μ− pairs produced in the forward rapidity region via the Drell-Yan reaction pp→γ*/Z+X→ℓ+ℓ−+X is presented, using data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 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. The results are compared to various theoretical predictions of the Z-boson production mechanism and can also be used to probe transverse-momentum-dependent parton distributions within the proton.Received 7 March 2022Accepted 13 July 2022DOI:https://doi.org/10.1103/PhysRevLett.129.091801Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2022 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasElectroweak interactionPhysical SystemsMuonsW & Z bosonsTechniquesHadron collidersGeneral PhysicsParticles & Fields
TL;DR: The photo-production of mesons at low transverse momentum was studied in peripheral lead-lead collisions collected by the LHCb experiment at a centre-of-mass energy per nucleon pair of 5 TeV, corresponding to an integrated luminosity of 210 $\rm{\mu b}^{-1}$ as discussed by the authors .
Abstract: The photo-production of $J/\psi$ mesons at low transverse momentum is studied in peripheral lead-lead collisions collected by the LHCb experiment at a centre-of-mass energy per nucleon pair of 5 TeV, corresponding to an integrated luminosity of 210 $\rm{\mu b}^{-1}$. The $J/\psi$ candidates are reconstructed through the prompt decay into two muons of opposite charge in the rapidity region of $2.0
26 Oct 2022
TL;DR: In this paper , the first observation of the B 0 s → D ∗ + D − ∗− decay and the measurement of its branching ratio relative to B 0 → D − + D−− decay are presented.
Abstract: The first observation of the B 0 s → D ∗ + D ∗− decay and the measurement of its branching ratio relative to the B 0 → D ∗ + D ∗− decay are presented. The data sample used corresponds to an integrated luminosity of 9 fb − 1 of proton-proton collisions recorded by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV between 2011 and 2018. The decay is observed with a very high significance and the ratio of branching fractions is determined to be where the first uncertainty is statistical, the second systematic and the third due to the uncertainty of the fragmentation fraction ratio f s /f d . The B 0 s → D ∗ + D ∗− branching fraction is calculated to be where the fourth uncertainty is due to the B 0 → D ∗ + D ∗− branching fraction.
TL;DR: The first observation of the semileptonic b-baryon decay was reported in this paper , with a significance of 6.1σ, using a data sample corresponding to 3 fb^{-1} of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 ǫ.
Abstract: The first observation of the semileptonic b-baryon decay Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ}, with a significance of 6.1σ, is reported using a data sample corresponding to 3 fb^{-1} of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The τ^{-} lepton is reconstructed in the hadronic decay to three charged pions. The ratio K=B(Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ})/B(Λ_{b}^{0}→Λ_{c}^{+}π^{-}π^{+}π^{-}) is measured to be 2.46±0.27±0.40, where the first uncertainty is statistical and the second systematic. The branching fraction B(Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ})=(1.50±0.16±0.25±0.23)% is obtained, where the third uncertainty is from the external branching fraction of the normalization channel Λ_{b}^{0}→Λ_{c}^{+}π^{-}π^{+}π^{-}. The ratio of semileptonic branching fractions R(Λ_{c}^{+})≡B(Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ})/B(Λ_{b}^{0}→Λ_{c}^{+}μ^{-}ν[over ¯]_{μ}) is derived to be 0.242±0.026±0.040±0.059, where the external branching fraction uncertainty from the channel Λ_{b}^{0}→Λ_{c}^{+}μ^{-}ν[over ¯]_{μ} contributes to the last term. This result is in agreement with the standard model prediction.
20 Apr 2022
TL;DR: In this paper , the first observations of $B^0\rightarrow\overline{D}^{*}(2007)^{0}K^{+}\pi^{+}$ and their branching fractions relative to that of the $B_s^0 \rightarrow K^{+κpi^{-}$ decay are presented, and their decay modes can potentially be used to investigate the spectroscopy of charm and charmstrange resonances and to determine the angle of the CKM unitarity triangle.
Abstract: 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. It is also important to understand them as a source of potential background in determinations of $\gamma$ from $B^{+}\rightarrow DK^{+}$ and $B^{0}\rightarrow DK^{+}\pi^{-}$ decays. The analysis is based on a sample corresponding to an integrated luminosity of $5.4 ~\rm{fb}^{-1}$ of proton--proton collision data at $13 ~\rm{TeV}$ centre-of-mass energy recorded with the LHCb detector. The $\overline{D}^{*}(2007)^{0}$ mesons are fully reconstructed in the $\overline{D}^{0}\pi^{0}$ and $\overline{D}^{0}\gamma$ channels, with the $\overline{D}^{0} \rightarrow K^{+}\pi^{-}$ decay. A novel weighting method is used to subtract background while simultaneously applying an event-by-event efficiency correction to account for resonant structures in the decays.
01 Apr 2022
TL;DR: In this article , a search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks, and two kinds of LLP production processes were considered.
Abstract: Abstract A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 . The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at $$\sqrt{s} = 13\text {\,TeV} $$ s = 13 \,TeV , corresponding to an integrated luminosity of 5.4 $$\text {\,fb} ^{-1}$$ \,fb - 1 . No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.
TL;DR: In this paper , the multihadron decays are observed in data corresponding to an integrated luminosity of 3 fb − 1 , collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector.
Abstract: Abstract The multihadron decays $$ {\Lambda}_b^0 $$ Λ b 0 → D + pπ−π− and $$ {\Lambda}_b^0 $$ Λ b 0 → D * + pπ−π− are observed in data corresponding to an integrated luminosity of 3 fb − 1 , collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay $$ {\Lambda}_b^0 $$ Λ b 0 → $$ {\Lambda}_c^{+} $$ Λ c + π + π − π − as a normalisation channel, the ratio of branching fractions is measured to be $$ \frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}p{\pi}^{-}{\pi}^{-}\right)}{\mathcal{B}\left({\Lambda}_b^0\to {\Lambda}_c^0{\pi}^{+}{\pi}^{-}{\pi}^{-}\right)}\times \frac{\mathcal{B}\left({D}^{+}\to {K}^{-}{\pi}^{+}{\pi}^{+}\right)}{\mathcal{B}\left({\Lambda}_c^0\to {pK}^{-}{\pi}^{-}\right)}=\left(5.35\pm 0.21\pm 0.16\right)\%, $$ B Λ b 0 → D + p π − π − B Λ b 0 → Λ c 0 π + π − π − × B D + → K − π + π + B Λ c 0 → pK − π − = 5.35 ± 0.21 ± 0.16 % , where the first uncertainty is statistical and the second systematic. The ratio of branching fractions for the $$ {\Lambda}_b^0 $$ Λ b 0 → D *+ pπ − π − and $$ {\Lambda}_b^0 $$ Λ b 0 → D + pπ − π − decays is found to be $$ \frac{\mathcal{B}\left({\Lambda}_b^0\to {D}^{\ast +}p{\pi}^{-}{\pi}^{-}\right)}{\mathcal{B}\left({\Lambda}_b^0\to {D}^{+}p{\pi}^{-}{\pi}^{-}\right)}\times \left(\mathcal{B}\left({D}^{\ast +}\to {D}^{+}{\pi}^0\right)+\mathcal{B}\left({D}^{\ast +}\to {D}^{+}\gamma \right)\right)=\left(61.3\pm 4.3\pm 4.0\right)\%. $$ B Λ b 0 → D ∗ + p π − π − B Λ b 0 → D + p π − π − × B D ∗ + → D + π 0 + B D ∗ + → D + γ = 61.3 ± 4.3 ± 4.0 % .
TL;DR: The first full angular analysis and an updated measurement of the decay-rate CP asymmetry of the D^{0}→ππ+ππ^{+}π^{-}μ+}μ^{+})−μ^{-}) decays are reported in this article , which is consistent with expectations from the standard model and with CP symmetry.
Abstract: The first full angular analysis and an updated measurement of the decay-rate CP asymmetry of the D^{0}→π^{+}π^{-}μ^{+}μ^{-} and D^{0}→K^{+}K^{-}μ^{+}μ^{-} decays are reported. The analysis uses proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. The dataset corresponds to an integrated luminosity of 9 fb^{-1}. The full set of CP -averaged angular observables and their CP asymmetries are measured as a function of the dimuon invariant mass. The results are consistent with expectations from the standard model and with CP symmetry.