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arXiv · 2605.04348

Observation of the charmless purely baryonic decay $\mathinner{\mathit{\Lambda}^0_b\!\to \mathit{\Lambda} p \overline{p}}$

LHCb collaboration·R. Aaij·M. Abdelfatah·A. S. W. Abdelmotteleb·C. Abellan Beteta·F. Abudinén·T. Ackernley·A. A. Adefisoye·B. Adeva·M. Adinolfi·P. Adlarson·C. Agapopoulou·C. A. Aidala·S. Akar·K. Akiba·P. Albicocco·J. Albrecht·R. Aleksiejunas·F. Alessio·P. Alvarez Cartelle·S. Amato·J. L. Amey·Y. Amhis·L. An·L. Anderlini·M. Andersson·P. Andreola·M. Andreotti·S. Andres Estrada·A. Anelli·D. Ao·C. Arata·F. Archilli·Z. Areg·M. Argenton·S. Arguedas Cuendis·L. Arnone·M. Artuso·E. Aslanides·R. Ataíde Da Silva·M. Atzeni·B. Audurier·J. A. Authier·D. Bacher·I. Bachiller Perea·S. Bachmann·M. Bachmayer·J. J. Back·Z. B. Bai·V. Balagura·A. Balboni·W. Baldini·Z. Baldwin·L. Balzani·H. Bao·J. Baptista de Souza Leite·C. Barbero Pretel·M. Barbetti·I. R. Barbosa·R. J. Barlow·M. Barnyakov·S. Barsuk·W. Barter·J. Bartz·S. Bashir·B. Batsukh·P. B. Battista·A. Bavarchee·A. Bay·A. Beck·M. Becker·F. Bedeschi·I. B. Bediaga·N. A. Behling·S. Belin·A. Bellavista·I. Belov·I. Belyaev·G. Bencivenni·E. Ben-Haim·R. Bernet·A. Bertolin·F. Betti·J. Bex·O. Bezshyyko·S. Bhattacharya·M. S. Bieker·N. V. Biesuz·A. Biolchini·M. Birch·F. C. R. Bishop·A. Bitadze·A. Bizzeti·T. Blake·F. Blanc·J. E. Blank·S. Blusk·J. A. Boelhauve·O. Boente Garcia·T. Boettcher
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Abstract

A search for the charmless purely baryonic decay $\mathinner{\mathit{\Lambda}^0_b\!\to \mathit{\Lambda} p \overline{p}}$ is performed using proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=13\,\text{TeV}$ and corresponding to an integrated luminosity of $6.0\,\text{fb}^{-1}$. The signal decay is observed with a significance of 5.1 standard deviations. Its branching fraction is measured for the first time, relative to that of the topologically similar decay $\mathinner{\mathit{\Lambda}^0_b\!\to \mathit{\Lambda} K^+ K^-}$. Contributions from intermediate charmonium resonances decaying to the $p \overline{p}$ and $K^+ K^-$ final states are explicitly excluded with a requirement on the invariant mass of the companion hadron system, $m(h\bar{h}) < 2.85\,\text{GeV}$, where $h$ stands for a proton or a charged kaon. The relative branching fraction is found to be $$ \frac{B(\mathinner{\mathit{\Lambda}^0_b\!\to \mathit{\Lambda} p \overline{p}})}{B(\mathinner{\mathit{\Lambda}^0_b\!\to \mathit{\Lambda} K^+ K^-})} = (5.1 \pm 1.3_{\text{(stat)}} \pm 0.3_{\text{(syst)}}) \times 10^{-2} \,. $$

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LHCb collaboration, R. Aaij, M. Abdelfatah, A. S. W. Abdelmotteleb, C. Abellan Beteta, F. Abudinén, T. Ackernley, A. A. Adefisoye, B. Adeva, M. Adinolfi, P. Adlarson, C. Agapopoulou, C. A. Aidala, S. Akar, K. Akiba, P. Albicocco, J. Albrecht, R. Aleksiejunas, F. Alessio, P. Alvarez Cartelle, S. Amato, J. L. Amey, Y. Amhis, L. An, L. Anderlini, M. Andersson, P. Andreola, M. Andreotti, S. Andres Estrada, A. Anelli, D. Ao, C. Arata, F. Archilli, Z. Areg, M. Argenton, S. Arguedas Cuendis, L. Arnone, M. Artuso, E. Aslanides, R. Ataíde Da Silva, M. Atzeni, B. Audurier, J. A. Authier, D. Bacher, I. Bachiller Perea, S. Bachmann, M. Bachmayer, J. J. Back, Z. B. Bai, V. Balagura, A. Balboni, W. Baldini, Z. Baldwin, L. Balzani, H. Bao, J. Baptista de Souza Leite, C. Barbero Pretel, M. Barbetti, I. R. Barbosa, R. J. Barlow, M. Barnyakov, S. Barsuk, W. Barter, J. Bartz, S. Bashir, B. Batsukh, P. B. Battista, A. Bavarchee, A. Bay, A. Beck, M. Becker, F. Bedeschi, I. B. Bediaga, N. A. Behling, S. Belin, A. Bellavista, I. Belov, I. Belyaev, G. Bencivenni, E. Ben-Haim, R. Bernet, A. Bertolin, F. Betti, J. Bex, O. Bezshyyko, S. Bhattacharya, M. S. Bieker, N. V. Biesuz, A. Biolchini, M. Birch, F. C. R. Bishop, A. Bitadze, A. Bizzeti, T. Blake, F. Blanc, J. E. Blank, S. Blusk, J. A. Boelhauve, O. Boente Garcia, T. Boettcher. 2026-05-05. Observation of the charmless purely baryonic decay $\mathinner{\mathit{\Lambda}^0_b\!\to \mathit{\Lambda} p \overline{p}}$. https://doi.org/10.1007/jhep08(2026)040

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