Quarkonium and charmed baryon production at LHCb
Ronan McNulty (UCD Dublin) on behalf of the LHCb collaboration
XIIIth Quark Confinement and the Hadron Spectrum 31 July – 6 August 2018, Maynooth.
Quarkonium and double charged baryon production at LHCb 1 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Overview
• LHCb • Charmed baryons ++ • Observation of Ξ cc. Measurement of branching fractions and lifetime. 0 • Lifetime of Ω c • Quarkonium production • J/ψ and ϒ inclusive in pp • J/ψ and ψ(2S) exclusive in pp, PbPb • Summary
Quarkonium and double charged baryon production at LHCb 2 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ
Int. J. Mod. Phys. A 30 (2015) 1530022 The LHCb detector
(charged sensitivity -3.5<η<-1.5)
Fully instrumented from 2 < η < 5
Trigger on muons pT> 400 MeV, and on J/ψ pT > 0 MeV. Precise vertex reconstruction. Excellent particle identification
Quarkonium and double charged baryon production at LHCb 3 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ
Run1 (2010-2012): √s = 7,8 TeV (pp) Data-taking 2010-2018 Run2 (2015-2018) :√s = 13 TeV (pp) Also pA, AA , and fixed target typically 1.1 pp interactions per beam-crossing
Quarkonium and double charged baryon production at LHCb 4 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Double-charmed Baryons Weak decay expected for ground states P 1 + + ++ + of Ξ ccd Ξ ccu Ω ccs J = 2 Predictions Mass ~ 3500-3700 MeV + ++ Few MeV mass splitting Ξ ccd / Ξ ccu τ(Ξ++) ~ 200-700 fs Ξ+) ~ Ω+) ~ 50-250 fs τ( τ( P 3 + (PRD90, 094007 (2014) J = 2 arXiv:1706.0691, 9807354, 9901323)
Strong/EM decays for excited + ++ + Ξ ccd Ξ ccu Ω ccs
Quarkonium and double charged baryon production at LHCb 5 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ
+ JHEP 12 (2013) 090 Search for Ξ cc
History + - + SELEX (2002) observe (6.3σ) in Λc K π (4.8σ in D+K-p+): Mass~3520 MeV, τ< 33fs . FOCUS and BaBar: no evidence. 2013 LHCb (0.65fb-1) no evidence
(not inconsistent with SELEX)
Quarkonium and double charged baryon production at LHCb 6 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ ++ PRL 119, 112001 (2017) Search for Ξ cc
History SELEX: hep-ex/0702001, Charm 2007 + - + – 6.3σ excess in Λc K π π , Mass~3520 MeV + + + – Candidate in Ξc π π π , Mass~3452 MeV
LHCb (1.7fb-1, √s = 13 TeV)
• Local significance > 12σ • Resolution 6.6 ± 0.8 MeV (=detector resolution) • Signal yield 313 ± 33 • Mass: 3621.40 ± 0.72(stat) ± 0.31(sys) MeV
Quarkonium and double charged baryon production at LHCb 7 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ ++ arXiv:1807.01919 Other decay modes of Ξ cc
LHCb (1.7fb-1, √s = 13 TeV) Search in • Strategy similar to but more efficient due to fewer particles. • Analysis performed blind, using MC and sidebands to optimise selection. • Signal yield 91 ± 20 • Significance: 5.9 σ • Mass: 3620.56 ± 1.45(stat) ± 0.61(sys) MeV • Agrees with observation in
= 0.035 ± 0.008 (stat) ± 0.003 (sys)
Quarkonium and double charged baryon production at LHCb 8
++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ PRL 119, 112001 (2017) ++ Lifetime of Ξ cc arXiv: 1806.02744
Peak remains after requiring + − ++ → + − Ξcc Λ c K π π inconsistency with primary vertex. Measure: 0 + − + − Λ b→Λ cπ π π
τ ( ++) = 256+22 (stat)±14(sys)fs Ξcc −20 weakly decaying !
Quarkonium and double charged baryon production at LHCb 9 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Comparison of theory and experiment various predictions
Tricky but possible to reconcile both signals e.g. arXiv:1709.09903
Future for LHCb: Measure other decay modes of Ξ++ and observe Ξ+
Quarkonium and double charged baryon production at LHCb 10 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ P 1 + Omega Baryon J = 2 Lifetime arXiv: 1807.02024 usc udc
‘Expected’ hierarchy dsc ssc
Test of HQE but note spin of spectators and cèWs interference
0 − → + − Ωc pK K π Compare + − + + → D K π π Yield: 978+-60 in b meson/baryon decays
Much larger (and cleaner) signal than previous experiments Quarkonium and double charged baryon production at LHCb 11 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Omega Baryon Lifetime
arXiv: 1807.02024 (old PDG value)
Summary of Omega lifetime measurements
0 τ ( ) = 268± 24(stat)±10(sys)± 2(D+) fs Ωc Dominant systematic is MC stats usc udc dsc ssc .... something to understand theoretically in determining hierarchy of lifetimes.
Quarkonium and double charged baryon production at LHCb 12 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Inclusive quarkonia production
Prompt: direct and J/ψ hadroproduction is not completely understood - charmonia feed-down cross-section, pT dependence, polarisation J/ψ from-b (better theoretical agreement) ϒ hadroproduction: heavier mass should give better agreement with NRQCD predictions
i j ˆ H dσ[pp → H + X] = ∑ ∫ dx1 dx2GpGp × dσ[ij → (QQ)n X] ϑ n i, j,n
intermediary states long-distance matrix elements
LHCb: more data at new energies and forward rapidities. Compare ratios to remove experimental and theoretical uncertainties Examine in different productions modes: pPb PbPb and compare to other
quarkonia e.g. χc, ηc, J/ψJ/ψ etc (not covered in this talk)
Quarkonium and double charged baryon production at LHCb 13 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ JHEP 1510 (2015) 172, Err. JHEP 1706 (2017) 063 J/Ψ in pp at 13 TeV with 3pb-1
σ (
σ (prompt J/ψ, pT < 14 GeV, 2.0 σ (J/ψ-from-b, pT < 14 GeV, 2.0 σ (pp → bbX) = 495± 2 ± 52 µb Quarkonium and double charged baryon production at LHCb 14 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ JHEP 1510 (2015) 172, Err. JHEP 1706 (2017) 063 J/Ψ in pp at 13 TeV with 3pb-1 full double differential distributions as fn of pT and rapidity in paper Prompt J/ψ from b σ ( JHEP 05 (2015) 103 JHEP 05 (1998) 007 Quarkonium and double charged baryon production at LHCb 15 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ ϒ in pp at 13 TeV with 277pb-1 JHEP 07(2018)134 full double differential distributions in paper Chinese Physics C 39 (2015) 12. Quarkonium and double charged baryon production at LHCb 16 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ JHEP 1510 (2015) 172, Err. JHEP 1706 (2017) 063 JHEP 07(2018)134 J/Ψ and ϒ in pp: ratio of 13/8 TeV σ ( Quarkonium and double charged baryon production at LHCb 17 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Motivation: Photo-production of vector mesons (at HERA) Here QCD works nicely! Note: • soft/hard transition • σ ~ xλ • g(x,Q2) (down to x=2E-6) JHEP 11 (2013) 085 10.3204/DESY-PROC-2012-03/58 Quarkonium and double charged baryon production at LHCb 18 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Central Exclusive Production (CEP) QED Photo-production Double pomeron exchange Laboratory to study • physics of the vacuum • soft/hard QCD • saturation • exotics (tetraquarks, glueballs, hybrids) Experimentally: Reconstruct central system and identify rapidity gaps Quarkonium and double charged baryon production at LHCb 19 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Veto (Run 2) Rough LHCb coverage y=-10 y=-2 y=0 y=2 y=10 13 TeV Elastic Scattering Single Diffraction Double Diffraction Central Exclusive Production (elastic) Central Exclusive Production (inelastic) Quarkonium and double charged baryon production at LHCb 20 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ High Rapidity Shower Counters at LHCb (HeRSCheL) arXiv:1806.04079 JINST 13 (2018) P04017 “Activity in HeRSCheL” Quarkonium and double charged baryon production at LHCb 21 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ J/ψ and ψ(2S) candidate arXiv:1806.04079 Tag with Herschel Anti-Tag with Herschel dσ dσ ~ exp(b t) ~ exp(b t) dt sig dt bkg 2 −2 − bbkg ~ 1 GeV bsig ~ 6 GeV Quarkonium and double charged baryon production at LHCb 22 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ pp and γp cross-sections arXiv:1806.04079 JHEP 1311 (2013) 085. JPG41 (2014) 055009 J/ψ ψ(2S) Quarkonium and double charged baryon production at LHCb 23 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Pb-Pb collisions LHCb-CONF-2018-003 The photon comes from the (coherent) Pb nucleus The pomeron comes from the nucleus -> Nuclear PDFs Quarkonium and double charged baryon production at LHCb 24 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Pb-Pb collisions LHCb-CONF-2018-003 Coherent HeRSCheL suppresses Incoherent incoherent events Quarkonium and double charged baryon production at LHCb 25 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Pb-Pb collisions LHCb-CONF-2018-003 Quarkonium and double charged baryon production at LHCb 26 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Summary • A small selection of recent results • Charmed baryons ++ • Observation of Ξ cc. Measurement of branching fractions and lifetime. 0 • Lifetime of Ω c • Quarkonium production • J/ψ and ϒ inclusive in pp • J/ψ exclusive in pp, PbPb • More information at http://lhcbproject.web.cern.ch/ lhcbproject/Publications/LHCbProjectPublic/Summary_all.html Quarkonium and double charged baryon production at LHCb 27 backup Quarkonium and double charged baryon production at LHCb 28 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Sample 1: Response to CEP events arXiv:1806.04079 First bin is > 95% pure CEP QED di-muons. Quarkonium and double charged baryon production at LHCb 29 ++ 0 LHCb Ξ cc Ω c Inclusive J/ψ , ϒ Exclusive J/ψ Sample 2: Non-CEP events (J/ψ dissociation) arXiv:1806.04079 Quarkonium and double charged baryon production at LHCb 30