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Baryonic B decays at LHCb

Baryonic B decays at LHCb. Baryon 2013, Glasgow, 25 June 2013, Paul Soler on behalf of the LHCb Collaboration. Introduction. In this talk, we will present LHCb results on a variety of baryonic B decays The talk will consist of the following three topics:

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Baryonic B decays at LHCb

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  1. Baryonic B decays at LHCb Baryon 2013, Glasgow, 25 June 2013, Paul Soler on behalf of the LHCb Collaboration

  2. Introduction • In this talk, we will present LHCb results on a variety of baryonic B decays • The talk will consist of the following three topics: • Measurements of the branching fractions of and prospects for , where • A search for the decays and • Measurement of the baryonic decays: • and • We will follow closely the following publications: arXiv:1303.7133, arXiv:1306.4489, arXiv:1306.2577 and arXiv:1109.6831 • Other LHCb talks at Baryon 2013: Alexander Bien, Daniel Hynds, Patrick Spradlin, Marco Pappagallo Baryon 2013, Glasgow, 25 June 2013

  3. LHCb detector • LHCb detector: designed for heavy flavour physics at the LHC • Forward geometry to maximise acceptance to b and c quarks • Unique detector capabilities at LHC: • Vertex Locator: s~40 fs • Particle identification: p, K, p, e, g, m • Momentum resolution: ~0.5% • Trigger: • Efficient selection hadronic and leptonic final states • Luminosity: 4x1032 cm-2s-1 • Collected: 38 pb-1in 2010, 1 fb-1in 2011 (7 TeV) and 2 fb-1in 2012 (8 TeV) JINST 3 S08005 (2008) velo rich1 rich2 Baryon 2013, Glasgow, 25 June 2013

  4. _ Measurements of B+K+p p • Measurement of allow study of states that decay into , and study excited decays • Babar and Belle measured with contributions from and • LHCb collected 1.0 fb-1 at 7 TeV increasing statistics by a factor of 10 for , allowing to probe the intermediate resonant structure of this decay: • where mode = arXiv:hep-ex/05070127 arXiv:0706.4167 arXiv:1303.7133 Baryon 2013, Glasgow, 25 June 2013

  5. _ Measurements of B+K+p p • Selection of events • Three tracks c2/ndf<3, p>1.5 GeV/c, pT>100 MeV/c, IP c2>1 • PID DlnLpp>-5, 5079<mB+<5579 MeV/c2, vertex c2/ndf<12, d>3mm • Max DOCA<0.2 mm, cos qfl<0.99998 • Final selection with multi-variate boosted decision tree arXiv:1303.7133 All K+pp Baryon 2013, Glasgow, 25 June 2013

  6. _ Measurements of B+K+p p arXiv:1303.7133 • Invariant mass distributions of system: Baryon 2013, Glasgow, 25 June 2013

  7. _ Measurements of B+K+p p • Signal yields and branching fractions: • Total yield in 1.0 fb-1: decays • Branching fractions: • Upper limit (95% CL) on X(3872) production: • Challenges predictions on molecular (vs cc1(2P) state) interpretation of X(3872), according to this paper: arXiv:0711.1854 arXiv:1303.7133 See Pappagallo talk, at Baryon 2013 Baryon 2013, Glasgow, 25 June 2013

  8. _ Prospects for B+h+p p, h=p, K • Further studies are ongoing in LHCb to study more generically all the decays: • This allows to measure forward-backward asymmetry: • One can also measure CP violation globally and in regions of the Dalitz plane: • Additionally, one can search for other decays, ie. Tree Penguin _ (angle of the meson in pp reference frame) Baryon 2013, Glasgow, 25 June 2013

  9. _ Search for BJ/y p p (h) • B decays to charmonia and dibaryons not studied extensively: • In tension with theoretical prediction: Best limit: Belle, PRD 72, (2005), 051105 No CKM phase PRD 86, (2012), 052006 CKM phase from Vtd • Other B decays to dibaryons have been observed: Bccs transition _ B0D0pp PRD 74, (2006), 051101(R) Pronounced enhancement in threshold region

  10. _ Search for BJ/y p p (h) • Search for and in LHCb, using 1.0 fb-1data from 2011 • No significant signal observed (small hint in B0s mode) arXiv:1306.4489 Baryon 2013, Glasgow, 25 June 2013

  11. _ Search for BJ/y p p (h) • Results on branching fractions with respect to: • Confidence levels at 90% and 95% set by integrating likelihood function in positive region of yield arXiv:1306.4489 Statistics limited (world’s most precise) (first measurement) (first measurement) Further tension with theory in B0 mode Hints in B0s mode are intriguing

  12. Measurements of Lb decays • Studies of rare Lb baryon decays can also be carried out at LHCb due to the large cross-sections • Searches for the rare decays: were carried out using 35 pb-1 LHCb data taken in 2010 • Feynman diagrams for and • Yields: 174±18 and 853±36 , • Final branching ratio fraction: with intermediate resonance states: arXiv:1109.6831 Colour-suppressed tree Tree Baryon 2013, Glasgow, 25 June 2013

  13. Measurements of Lb decays • A search for the rare Lb baryon decay: was carried out at LHCb using 1.0 fb-1of 2011 data • This is rare flavour changing neutral current bs process • Yields: 2680±64 and 78±12 decays arXiv:1306.2579 See also Spradlin talk at Baryon 2013 Baryon 2013, Glasgow, 25 June 2013

  14. Measurements of Lb decays arXiv:1306.2579 • Differential branching fraction: • Relative branching fraction: • Absolute branching fraction: • Blue points: LHCb data • Red dashed line and yellow band: SM prediction • LHCb 90% CL upper limit • Evidence for decay when arXiv:1301.3737 PRD87 (2013) 074031 Baryon 2013, Glasgow, 25 June 2013

  15. Conclusions • LHCb provides a rich programme of baryonic physics • Baryonic decays of B mesons and decays of b baryons can be carried out at LHCb with great precision, due to the large cross-sections at the LHC and efficient triggering in LHCb • We reported on: • Measurements of the branching fractions of and prospects for , where • A search for the decays and • Measurement of the baryonic decays: and Baryon 2013, Glasgow, 25 June 2013

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