Beauty Baryon LHCb Steven Blusk Beauty 2014, Edinburgh, Scotland, July 14-18, 2014 On behalf of the LHCb collaboration Syracuse University

Beauty LHCb Beauty baryons are produced copiously in LHCb, opening up new avenues for study and improved precision of their properties and decays. Production Mass Lifetime New decay modes CP asymmetries Other studies, for a future BEAUTY meeting… Rare decays, e.g.  b   +  -. 1 fb -1 result (PLB 725, 2013) being updated to 3 fb -1. Probe CKM elements V cb, V ub in  b   c l and  b  p l decays Excited b-baryon states bc-baryons 2

Detector & data sets 3  Precision vertex detector (  ip ~ 20 um), tracking  p /p ≈ 0.5%  Excellent particle identification, including hadron separation to ~100 GeV  High bandwidth trigger, ~2-5 kHz to tape, hadronic, EM and muonic final states.  Wide & flexible physics scope: b, c, quarkonia, W, Z’s, exotics, jets, etc.  Analyses based on:  2011, 1 fb 7 TeV  2012, 2 fb 8 TeV

Menu for this talk 4 B(  b   c  ) arXiv: arXiv:  b  and  b   lifetimes arXiv: arXiv:  b 0 mass, lifetime & production properties arXiv: arXiv:  b /  b 0  D 0 ph ± decays arXiv: arXiv:  b  J/  pK - and  b  J/  p  - arXiv: arXiv: Search for  b /  b 0  K S ph ± arXiv: arXiv: First observation of  b   c + D (s)   arXiv: arXiv:

Reconstructing hyperons from b decay 5  Average b-momentum in LHCb ~ 100 GeV  E.g.  b  J/ , 30 GeV    ≈30  ≈ 2.5 m 2.3 m “Long”

Reconstructing hyperons from b decay 6  Average b-momentum in LHCb ~ 100 GeV  E.g.  b  J/ , 30 GeV    ≈30  ≈ 2.5 m  Hyperons reconstructed if they decay upstream of TT. 2.3 m “Downstream”

Reconstructing hyperons from b decay 7  Going beyond  b..  Example:  b   J/  ,       Get hit 2X ….  (  - )~164 ps,  (  )~260 ps 2.3 m “Downstream”

Production, BFs Mass and Lifetimes 8

 b   c  BF LHCb-PAPER arXiv: arXiv: submitted to JHEP 1 fb -1 State of affairs, pre-2014: – “Golden mode” for  b decays only known to ≈ 70% precision! Use 45,000 fully reco’d  b   c  + and 106,000 B 0  D -  + decays. 9

 b   c  BF LHCb-PAPER arXiv: arXiv: submitted to JHEP 1 fb -1 State of affairs, pre-2014: – “Golden mode” for  b decays only known to ≈ 70% precision! Use 45,000 fully reco’d  b   c  + and 106,000 B 0  D -  + decays. Anatomy: Scale factor between the two analyses 10 LHCb, PRD 85, (2012) Measured in semileptonic analysis Measured here, in  b   c  decays

 b   c  BF LHCb-PAPER arXiv: arXiv: submitted to JHEP 1 fb -1 State of affairs, pre-2014: – “Golden mode” for  b decays only known to ≈ 70% precision! Use 45,000 fully reco’d  b   c  + and 106,000 B 0  D -  + decays. Anatomy: Scale factor between the two analyses 11 BF measured to 8% precision! Huge leap forward in precision! B(  c  pK  ) common to both analyses  cancelation of large syst. error LHCb, PRD 85, (2012) Measured in semileptonic analysis Measured here, in  b   c  decays

 b  and  b   lifetimes Reconstruct  b   J/  ,       and  b   J/  ,         with   p    12 LHCb-PAPER arXiv: arXiv: submitted to PLB 3 fb ±2058±8

 b  and  b   lifetimes Reconstruct  b   J/  ,       and  b   J/  ,         with   p    13 LHCb-PAPER arXiv: arXiv: submitted to PLB 3 fb ±2058±8  Best precision to date.  Consistent with the recent CDF results CDF, PRD 89, (2014) (See talk by J. Rosner)

Studies of the  b 0 baryon - 1 Until recently, little known about the  b 0 baryon. – Lifetime unmeasured – Mass only known to ~2.5 MeV (  b mass known to ~0.3 MeV) – Relative production rates ? Are prod. properties (p T,  ) similar to  b ? LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb -1 14

Studies of the  b 0 baryon - 1 Until recently, little known about the  b 0 baryon. – Lifetime unmeasured – Mass only known to ~2.5 MeV (  b mass known to ~0.3 MeV) – Relative production rates ? Are prod. properties (p T,  ) similar to  b ? In  b,  b studies, decays with J/  +hyperons have been ‘the work horse’. – Use CF decays, J/  for triggering, well-displaced vertices from hyperons with narrow widths. Hadron ID helpful, but not crucial. – In LHCb, large boosts, large c  leads to a reduction in total efficiency for hyperon reco. LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb -1 15

Studies of the  b 0 baryon - 1 Until recently, little known about the  b 0 baryon. – Lifetime unmeasured – Mass only known to ~2.5 MeV (  b mass known to ~0.3 MeV) – Relative production rates ? Are prod. properties (p T,  ) similar to  b ? In  b,  b studies, decays with J/  +hyperons have been ‘the work horse’. – Use CF decays, J/  for triggering, well-displaced vertices from hyperons with narrow widths. Hadron ID helpful, but not crucial. – In LHCb, large boosts, large c  leads to a reduction in total efficiency for hyperon reco. To play into LHCb’s strengths, use Cabibbo-suppressed decays … no hyperons! Despite 3 X lower BF, still win big in total acceptance. LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb CFCS

Studies of the  b 0 baryon - 1 Until recently, little known about the  b 0 baryon. – Lifetime unmeasured – Mass only known to ~2.5 MeV (  b mass known to ~0.3 MeV) – Relative production rates ? Are prod. properties (p T,  ) similar to  b ? In  b,  b studies, decays with J/  +hyperons have been ‘the work horse’. – Use CF decays, J/  for triggering, well-displaced vertices from hyperons with narrow widths. Hadron ID helpful, but not crucial. – In LHCb, large boosts, large c  leads to a reduction in total efficiency for hyperon reco. To play into LHCb’s strengths, use Cabibbo-suppressed decays … no hyperons! Despite 3 X lower BF, still win big in total acceptance. Excellent normalization mode (identical final state):  b   c ,  c  pK  ! – Most systematics cancel at 1 st order in relative measurements. – Small differences in momentum spectra and lifetime of  c vs  c  pK  LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb CFCS

Studies of the  b 0 baryon bc+bc+ b0c+b0c+ ~188,000  b   c +   ~3,800  b 0   c +   Mass of  b 0 ~5X more precise than prev. best from LHCb  Precision mass LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb -1

Studies of the  b 0 baryon bc+bc+ b0c+b0c+ ~188,000  b   c +   ~3,800  b 0   c +   Mass of  b 0 ~5X more precise than prev. best from LHCb  Lifetime of  b 0 baryon measured relative to that of  b.   b lifetime now known to high precision (see talk by P. Gandini)  Perform sim. fit in bins of decay time, correct by relative efficiency (from simulation) 1 st measurement of  b 0 lifetime   b and  b 0 lifetimes equal to within 2%  Consistent with expectations from HQE  Precision mass LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb -1

Studies of the  b 0 baryon  Can also study the relative production rate vs (p T,  ) Steep p T dependence of  b /B 0 production also in  b 0 ! (see talk by Maria Zangoli)  Relative production rate, integrated. ≈1≈0.1 Semileptonic  b   c  + scaled LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb -1

Studies of the  b 0 baryon  We also have a VERY CLEAN sample of  c + decays Mass of  c + ≈4X more precise than WA  Can also study the relative production rate vs (p T,  ) Steep p T dependence of  b /B 0 production also in  b 0 ! (see talk by Maria Zangoli)  Relative production rate, integrated. ≈1≈0.1 Semileptonic  b   c  + scaled LHCb-PAPER arXiv: arXiv: Accepted in PRL 3 fb -1

New decay modes & CPV studies 22

 b /  b 0  D 0 ph ± 23 LHCb-PAPER arXiv: arXiv: PRD 89, (2014) 1 fb -1  The  b  D 0 pK decay can be used to measure the weak phase , ala B 0  D 0 K *0. Usual trick.. Both diagrams are O( 3 ) Exploit interference for final states common to D 0 and D 0.

 b /  b 0  D 0 ph ± 24 LHCb-PAPER arXiv: arXiv: PRD 89, (2014) 1 fb -1  The  b  D 0 pK decay can be used to measure the weak phase , ala B 0  D 0 K *0. Usual trick.. Both diagrams are O( 3 ) Exploit interference for final states common to D 0 and D 0.  Start with CF D 0  K  decay, to first observe these decays.

 b /  b 0  D 0 ph ± 25 LHCb-PAPER arXiv: arXiv: PRD 89, (2014) 1 fb -1  The  b  D 0 pK decay can be used to measure the weak phase , ala B 0  D 0 K *0. Usual trick.. Both diagrams are O( 3 ) Exploit interference for final states common to D 0 and D 0.  Several first observations in  b and  b 0 decays!  Start with CF D 0  K  decay, to first observe these decays.  Good prospects for  with larger data set

 b  J/  pK - and  b  J/  p  - 26  CP violation not yet observed in the baryon sector.  The decay  b  J/  pK recently observed by LHCb  most precise  (  b ) (see P. Gandini talk).  The CS decay,  b  J/  p  , unobserved prior to this analysis, has 2 amplitudes, tree & penguin with different weak phase  NP can enter in the penguin and give rise to direct CPV. LHCb-PAPER arXiv: arXiv: | Submitted to JHEP 3 fb -1

 b  J/  pK - and  b  J/  p  - 27  CP violation not yet observed in the baryon sector.  The decay  b  J/  pK recently observed by LHCb  most precise  (  b ) (see P. Gandini talk).  The CS decay,  b  J/  p  , unobserved prior to this analysis, has 2 amplitudes, tree & penguin with different weak phase  NP can enter in the penguin and give rise to direct CPV.  First observation of  b  J/  p    Direct CPV wrt favored mode (|P/T| SM <<1) LHCb-PAPER arXiv: arXiv: | Submitted to JHEP 3 fb -1

Charmless: Search for  b /  b 0  K S ph ± Prior to this analysis, no 3-body charmless decays of b-baryons had been observed. Like B decays, 3-body charmless b-baryon decays contains penguin contributions  NP can enter. Opens up an interesting window to explore CPV in the b-baryon sector across the Dalitz plot. BFs normalized to the kinematically similar B 0  K S  +  - decay. 28 LHCb-PAPER arXiv: arXiv: JHEP 04 (2014) fb -1 Signal channels M(K S p  ) [ MeV ] M(K S p  ) [ MeV ] Norm. mode M(K S  ) [ MeV ] First Observation

Charmless: Search for  b /  b 0  K S ph ± Prior to this analysis, no 3-body charmless decays of b-baryons had been observed. Like B decays, 3-body charmless b-baryon decays contains penguin contributions  NP can enter. Opens up an interesting window to explore CPV in the b-baryon sector across the Dalitz plot. BFs normalized to the kinematically similar B 0  K S  +  - decay. 29 LHCb-PAPER arXiv: arXiv: JHEP 04 (2014) fb -1 Signal channels M(K S p  ) [ MeV ] M(K S p  ) [ MeV ] Norm. mode M(K S  ) [ MeV ] See paper for additional  b BFs  Measure direct CPV relative to CF mode  b   c (pK S )  - (penguins should be negligible) Consistent with zero. First Observation

 b   c + D (s)  30 LHCb-PAPER arXiv: arXiv: PRL 112, (2014) 3 fb -1  First observation of b-baryons decaying to double-charm final states Consistent with expected Cabibbo suppression bc+Dsbc+Ds bc+Dbc+D Yield~4,600Yield~260 Bonus: Get most precise  b mass measurement from measured mass difference M(  b )– M(B 0 ):

 b   c + D (s)  31 LHCb-PAPER arXiv: arXiv: PRL 112, (2014) 3 fb -1  First observation of b-baryons decaying to double-charm final states Consistent with expected Cabibbo suppression  B(  b   c D s ): Normalize to B(B 0  D  D s + ), but relative yield strong function of p T.  Measure double ratio, same p T dependence, which cancels in ratio. Several world best BF measurements bc+Dsbc+Ds bc+Dbc+D Yield~4,600Yield~260 Bonus: Get most precise  b mass measurement from measured mass difference M(  b )– M(B 0 ): LHCb

Summary b-baryon rate at LHCb very large, 1  b for every 2 B 0 ! Production, decays, b-baryon properties and CPV are beginning to be probed. – Lifetime of  b 0 went from unmeasured  2% precision (  (  b ) known to ~1%) – Mass of  b 0 went from ±2.5 MeV  ~0.4 MeV, almost on par with  b ! Other high yield modes of b-baryons are also being explored that exploit the excellent PID in LHCb. Expect more on rare decays, V cb, V ub, excited baryonic states soon.. The future is bright for b-baryon LHCb. 32