Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

Search for Lepton Flavour Violation in four-body charm decays at LHCb

This dissertation presents a search for physics beyond the standard model by the study of lepton flavour violation in four-body charm decays. A search for the decays $D^0 \to \pi^- \pi^+ \mu^\pm e^\mp$ , $D^0 \to K^- \pi^+ \mu^\pm e^\mp$ and $D^0 \to K^- K^+ \mu^\pm e^\mp$ using data collected by the LHCb experiment is performed. These decays provide a unique opportunity to search for new physics in the up-type quark sector, similar to multiple searches performed in the down-type quark sector in other works. The decays are studied using proton-proton collision data corresponding to $6\,fb^{−1}$ of integrated luminosity recorded at a centre-of-mass energy of 13 TeV during the years 2015-2018. An expected upper limit on the branching fraction for these decays is estimated at the order of $10^{−8}$ . Furthermore, separate expected limits for decays with different relative charge constellations in the final dilepton state in respect to the flavour of the $D^0$ meson are reported, providing increased sensitivity to new physics scenarios. It is shown that the current best limit on the branching ratios can be improved by two orders of magnitude with the LHCb dataset. This analysis is performed on a blind dataset with possible $D^0 \to \pi^- \pi^+ \mu^\pm e^\mp$ , $D^0 \to K^- \pi^+ \mu^\pm e^\mp$ and $D^0 \to K^- K^+ \mu^\pm e^\mp$ candidates removed from the dataset. The results are therefore validated by performing an updated measurement of the branching fraction for $D^0 \to \pi^- \pi^+ \mu^- \mu^+$ and $D^0 \to K^- K^+ \mu^- \mu^+$ decays

LHCb - Updated measurement of decay-time-dependent CP asymmetries in D0→K+K− and D0→π+π− decays at LHCb

The measurement of the decay-time dependent charge parity (CP) asymmetry in \D^0 \to \pi^+ \pi^- and \D^0 \to K^+ K^- is presented using proton-proton collisions. The data was recorded at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 $fb^{-1}$, with the LHCb detector. Neutral $D$ mesons which arise from semi-leptonic decays of b-flavoured hadrons are used

Molecular recognition of complex-­type biantennary N-­glycans by protein receptors: a 3D view by using NMR

16 p.-14 fig.The current surge in defining glycobiomarkers by applying lectins rekindles interest in definition of the sugar-binding sites of lectins at high resolution.Natural complex-type N-glycans can present more than one potential binding motif,posing the question of the actual mode of interaction when interpreting, for example,lectin array data. By strategically combining N-glycan preparation with saturation-transfer difference NMR and modeling, we illustrate that epitope recognition depends on the structural context of both the sugar and the lectin (here, wheat germ agglutinin and a single hevein domain) and cannot always be predicted from simplified model systems studied in the solid state. We also monitor branch-end substitutions by this strategy and describe a three-dimensional structure that accounts for the accommodation of the α2,6- sialylated terminus of a biantennary N-glycan by viscumin. In addition, we provide a structural explanation for the role of terminal α2,6-sialylation in precluding the interaction of natural N-glycans with lectin from Maackia amurensis. The approach described is thus capable of pinpointing lectin-binding motifs in natural N-glycans and providing detailed structural explanations for lectin selectivity.Competitiveness of Spain (Grants CTQ2011-22514,CTQ2009-08536, and CTQ2012-30820), from Comunidad de Madrid (MHit project), and from the EU (Projects GlycoHit and GlycoPharm, and COST action CM1102) is acknowledged.Peer reviewe

Molecular Recognition of Complex-Type Biantennary <i>N</i>‑Glycans by Protein Receptors: a Three-Dimensional View on Epitope Selection by NMR

The current surge in defining glycobiomarkers by applying lectins rekindles interest in definition of the sugar-binding sites of lectins at high resolution. Natural complex-type <i>N</i>-glycans can present more than one potential binding motif, posing the question of the actual mode of interaction when interpreting, for example, lectin array data. By strategically combining <i>N</i>-glycan preparation with saturation-transfer difference NMR and modeling, we illustrate that epitope recognition depends on the structural context of both the sugar and the lectin (here, wheat germ agglutinin and a single hevein domain) and cannot always be predicted from simplified model systems studied in the solid state. We also monitor branch-end substitutions by this strategy and describe a three-dimensional structure that accounts for the accommodation of the α2,6-sialyl­ated terminus of a biantennary <i>N</i>-glycan by viscumin. In addition, we provide a structural explanation for the role of terminal α2,6-sialyl­ation in precluding the interaction of natural <i>N</i>-glycans with lectin from Maackia amurensis. The approach described is thus capable of pinpointing lectin-binding motifs in natural <i>N</i>-glycans and providing detailed structural explanations for lectin selectivity