Hadron Spectroscopy, exotics and Bc physics at LHCb. Biplab Dey

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1 Hadron Spectroscopy, exotics and Bc physics at LHCb Biplab Dey on behalf of the LHCb collaboration BEACH 2016, Fairfax, VA Biplab Dey Hadron Spectroscopy & Bc June 16th, / 26

2 Introduction Introduction: exotics Tetra/pentaquarks were predicted by Gell-Mann/Zweig in 1964 Yet, only a handful seen, only in the heavy-quark sector. LHCb: first dedicated b/c-physics detector at a hadron collider. Excellent vertexing and PID. B : Λ 0 b : B s 4 : 2 : 1 within acceptance. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

3 Introduction The charmonia XYZ states and exotics Olsen Exotics revolution in mesonic sector since Belle discovery of X (3872) in Several XYZ BESIII, Belle/BaBar, CDF/D0, LHCb/CMS. No clear organising principle yet. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

4 Introduction The charmonia XYZ states and exotics Olsen Exotics revolution in mesonic sector since Belle discovery of X (3872) in Several XYZ BESIII, Belle/BaBar, CDF/D0, LHCb/CMS. No clear organising principle yet. Baryonic sector: LHCb discovery of two pentaquarks in Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

5 Outline of spectroscopy results Some selected LHCb Pentaquarks in Λ 0 b J/ψ pk: model-independent evidence NEW! Pentaquark evidence in Λ 0 b J/ψ pπ NEW! Exotic structures in B + X ( J/ψ φ)k + NEW! LHCb non-confirmation of D0 tetraquark X (5568) + B s π + Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

6 Model-independent pentaquark evidence in Λ 0 b J/ψ pk Pentaquarks in Λ 0 b J/ψ pk PRL 115, : LHCb discovers two pentaquark states P c J/ψ p. Amplitude fit in full 6d. 9 σ and 12 σ evidence for two P c states. Phase-motion distinctive of a resonant structure (for P c (4450)) P c (4380) 3/2 -, 9σ Im A Pc (a) (b) P c (4450) 5/2 +, 12σ P c(4450) P c(4380) LHCb Re A Pc Re A Pc However, the large number of poorly known Λ states makes the amplitude fits inherently model-dependent. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

7 Model-independent pentaquark evidence in Λ 0 b J/ψ pk Model-independent P c evidence (NEW!) , Test null hypothesis H 0 : no P c s are needed and Λ resonances can alone explain data. Signature of each spin-j Λ J pk: moments expansion in cos θ Λ. dn d cos θ Λ P U l k = l max = Pl U P l (cos θ Λ ) l=0 n k cand (w i /ɛ i )P l (cos θλ i ) i=0 Λ b J/Ψ θ Λ* If J max is the highest Λ J spin in the k th m pk bin, l max = 2J max. Since the Legendre polynomials P l forms an orthonormal complete basis; l max can describe any distribution. Data model: hypothesis H 1 with large l max = 31. p Λ * K Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

8 Model-independent pentaquark evidence in Λ 0 b J/ψ pk Testing the Λ -only hypothesis H For a given m pk bin, limit J max. Loring (hep-th/ ) High spins not expected at low Λ masses. l max = 2J max Higher moments can only be produced by P c reflections. Λ -only model H 0 : l max (m pk ). Experimental LHCb no Λ* expected here Test statistic for compatibility check between l max = 31 (H 1 ) and l max (m pk ) (H 0 ), determined using toys: N events [ ] PDF (mj/ψ p H 0 )/I H0 ( 2lnL) 2 w i ln PDF (m J/ψ p H 1 )/I H1 i=1 Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

9 Model-independent pentaquark evidence in Λ 0 b J/ψ pk # of toys Quantitative test of the null hypothesis H 0 Toys generated with l max (m pk ) (H 0 ) show a 9σ deviation wrt Data. Null hypothesis rejected with minimal assumption on the Λ s. Consistent with the P c evidence from amplitude fits σ Λ* only hypothesis, H 0 Same analysis for Z c (4200) + claimed by Belle in B 0 J/ψ K + π is in the pipeline. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

10 Pentaquark evidence in Λ 0 b J/ψ pπ Pentaquarks in Λ 0 b J/ψ pπ (NEW!) LHCb-PAPER Observation in a new mode: genuine resonances and not kinematic effects. Cabibbo-suppressed mode: 15 less statistics, 3 more background. Additional internal W -exchange, compared to Λ 0 b J/ψ pk. Λ b J/ψ p π N sig = 1885± 50 ~18% bkgd LHCb Λ 0 b b u d W N resonances c c d u d J/ψ N Λ 0 b b u d W external W ex. dū u c c u d π P + c Λ 0 b b u d W internal W ex. c c d u ū d P + c π Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

11 Pentaquark evidence in Λ 0 b J/ψ pπ Λ 0 b J/ψ pπ : amplitude models LHCb-PAPER No obvious structure in m(j/ψ p). Need full amplitude analysis. 15 established N states. Reduced (RM): central values. Extended (EM): syst. + signif. Breit-Wigners for all resonances; Flatte for N(1535) Significant pπ S-wave at threshold: non-resonant component. Check consistency with the two P c states from Λ 0 b J/ψ pk. Λ 0 b Z c(4200) ( J/ψ π )p also considered from Belle ( ). Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

12 Pentaquark evidence in Λ 0 b J/ψ pπ Fit results LHCb-PAPER N + 2P c + Z c gives good fit. Exotic significance is 3.1σ (EM N s). preliminary preliminary LHCb preliminary m pπ > 1.8 GeV P c (4450) P c (4380) Z c (4200) Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

13 Pentaquark evidence in Λ 0 b J/ψ pπ Fit results LHCb-PAPER N + 2P c + Z c gives good fit. Exotic significance is 3.1σ (EM N s). preliminary preliminary LHCb preliminary m pπ > 1.8 GeV P c (4450) P c (4380) Z c (4200) R π/k B(Λ0 b π P + c ) B(Λ 0 b K P + c ) tests P+ c production mechanism. R π/k 0.05(4380), R π/k (4450) Consistent w/ Cabibbo suppression (Cheng, ): Overall outlook: J/ψ pπ data is consistent with P c s seen in J/ψ pk. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

14 Exotic structures in B + J/ψ φk + The X (4140) chronology 5σ narrow CDF(2011) X(4140) unpublished N(B) ~ 115 possible X(4274) PRD 85, R LHCb 0.37/fb (2012) N(B) ~382 CDF extrapol. PLB 734, 261 (2014) 5σ, wider X(4140) N(B) ~ MeV higher than CDF (2014) N(B) ~ σ 2 nd peak not significant Also 4.7σ in prompt p p (2015) X (4140): some disagreements over the years from hadron colliders. Also some results from the B-factories. Not too significant, but neither in contradiction with hadron colliders. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

15 Exotic structures in B + J/ψ φk + X states in 3/fb LHCb (NEW!) LHCb-Paper LHCb preliminary Selection similar to 0.37/fb analysis, with some re-optimization. N sig = 4289 ± 151, background fraction 23 ± 6% inside signal band. Largest world dataset for this mode. First amplitude analysis in 6d: m φk and 5 angular variables Three contributing amplitudes that can interfere: B + J/ψ K + ( φk + ) (poorly understood K states) B + X ( J/ψ φ)k + ( exotic X states) B + Z + c ( J/ψ K + )φ ( exotic Z states) Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

16 Exotic structures in B + J/ψ φk + Fit results LHCb-Paper No obvious peaking structure in m φk, but rich K structure underneath. LHCb preliminary Adding Z + J/ψ K + doesn t have much effect. Only adding X states improves fit. LHCb preliminary p=22% X(4140) 8.4σ LHCb preliminary X(4700) 5.6σ no exotics X(4274) 6.0σ X(4400) 6.1σ Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

17 Exotic structures in B + J/ψ φk + Fit results for K φk LHCb-Paper K : within kinematic limits, red circles are the LHCb fit results. 1 + : NR (1900) (1930). FF is 42%. Godfrey-Isgur Default Established Unconfirmed 2 : 1777(1770) (1820). FF is 11%. 1 : 1717(1680). FF is 6.7%. Good agreement with both theory (Godfrey-Isgur) and previous experiments. 2 + : 2073(1980). FF is 2.9%. 0 : consistent with unconfirmed 1874(1830). FF is 2.6%. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

18 Exotic structures in B + J/ψ φk + Fit results for X J/ψ φ LHCb-Paper X (4140) mass consistent with previous measurements. Width larger. X (4274) mass/width consistent with unpub. CDF results. X (4140) and X (4274): J PC = 1 ++ determined for the 1st time. X (4140) can be a possible D s ± Ds cusp (rescattering). High m J/ψ φ mass region probed for the 1st time. Dominated by 0. NR + new X (4500) and X (4700) resonances. State J PC signif. Mass Width fit frac. X (4140) σ 4165 ± ± ± X (4274) σ ± ± ± X (4500) σ 4506 ± ± ± X (4700) σ 4704 ± ± ± Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

19 Exotic structures in B + J/ψ φk + Interpretations already... postdiction: Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

20 LHCb non-confirmation of D0 tetraquark D0 claim of X (5568) ± B s π ± D0: 5 σ evidence for new 4-flavored (bsud) exotic X (5568). Fraction of B s s from X decay: ρ D0 X = (8.6 ± 1.9 ± 1.4)% N(B s ) ~ 5500 σ res ~ 30 Bs J/ψ Φ J/ψ μμ Φ KK N(X) = 133 ± 31 M = 5567±2.9 Г = 21.9± 6.4 LHCb should see this. Large and clean samples. B s D s- π + N(B s ) ~ 65k σ res ~ 15 MeV S/B ~ 10 Bs J/ψ Φ N(B s ) ~ 45k σ res ~ 6 MeV S/B ~ 50 Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

21 LHCb non-confirmation of D0 tetraquark LHCb X (5568) non-confirmation LHCb-CONF B s and π from the same PV. Mass-constrained {B s, D s, J/ψ }. No significant signal seen in full Run I. ρ LHCb X < 95% CL p T (B s ) > 5 GeV N(X) = 8± 66 p T (B s ) > 10 GeV N(X) = 81±57 Checks done in bins of rapidity. Expected B structures seen w/ similar analysis chain for B 0. B 1 *(5747) B*π B 2 *(5747) Bπ B 2 *(5721) B*π D0 structure remains yet to be confirmed by another experiment. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

22 LHCb non-confirmation of D0 tetraquark LHCb X (5568) non-confirmation LHCb-CONF Expected signal if 8.6% of B s s came from X (5568): Candidates / ( 4 MeV/c 2 ) LHCb Preliminary Claimed X(5568) state Combinatorial m(bsπ 0 ) [MeV/c 2 ] ± Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

23 B c LHCb B + c LHCb Lowest bound state of b and c quarks. Unlike bb, cc; decays only weakly. Unique, flavor asymmetry: t is too heavy. Either the b or c can decay: (a) b cw + : J/ψ l + ν, J/ψ π + (b) c sw + : B s l + ν, B s π + (c) Weak annihilation (WA), bc W + : τ + ν τ, K 0 K + Experimentally, b c is clearer (due to the J/ψ ) but Cabibbo suppressed. c s is challenging but Cabibbo favored (B 70%). First seen in B + c B 0 s π + by LHCb ( ) WA is sensitive to H +. CF over B + by V cb V ub Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

24 B c LHCb B + c LHCb LHCb results dominate many of the measurements, including the world s best measurements on B c + mass and lifetime. Physics mode L (fb 1 ) Production, Mass Production Production σ(b + c )B(B+ c J/ψ π+ ) σ(b + )B(B + J/ψ K + ) σ(b + c ) 0.37 PRL , 2 PRL σ(b + ) B(B+ c B 0 s π + ) 3 PRL B(B + c ψ(2s)π+ ) B(B + c J/ψ π + ) 1 PRD , 3 PRD Decay, Mass B c + J/ψ D s ( )+ 3 PRD Decay, Mass B c + J/ψ p pπ + 3 PRL Decay B c + J/ψ π + π π PRL Decay B c + J/ψ K + 1 JHEP Decay B c + J/ψ K + K π + 3 JHEP Decay B c + J/ψ 3π + 3π 3 JHEP05(2014)148 Decay B(B + c J/ψ π+ ) B(B + c J/ψ µ + ν µ) 1 PRD Lifetime B + c J/ψ µ + ν µ 2 EPJC, Lifetime B + c J/ψ π + 3 PLB Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

25 B c LHCb WA studies via charmless B c h + h h B c decays to charmless states proceeds only via bc W + u{d, s}. V ud > V us implies S = 0 dominates over S = 1. LHCb is studying B c {KKK, πππ, KKπ, p pk, p pπ}. Large available phase-space! Intermediate D 0, B s,d and c c also contribute. Some theory ( ) estimates for (quasi) 2-body decays. B < Expect few events in Run I. Utlimately, Dalitz analysis, A CP,... Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

26 B c LHCb Search for B + c p pπ + (NEW!) LHCb-PAPER m(p p) < 2.85 GeV: near-threshold p p production expected. Also [2.85, 3.15] GeV for the J/ψ region. Measured R p fc f u B(B c + p pπ + ), with B + p pπ + as norm. mode No signal detected. UL s for 95% CL set as: R p < and R J/ψ p < Compatible with LHCb B(B + c J/ψ π + ). Hoping for some signal with Run II data. B + c K + K π + in the immediate pipeline. Signal mode N(B + ) = 1644 ±83 BDT > 0.04 LHCb BDT [0.04,0.12] Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

27 Summary Summary: LHCb Λ 0 b J/ψ pk : model-independent approach confirms Λ reflections can t explain data. Exotics present. Λ 0 b J/ψ pπ : P c s consistent with the J/ψ pk mode. R π/k consistent with Cabibbo suppression. X J/ψ φ: confirms 1 + for X (4140) and X (4274). X (4140) width larger than CDF. Two new high-mass 0 + resonances. LHCb does not confirm D0 X (5568). Inputs from ATLAS/CMS? Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

28 Summary Summary: B + c LHCb LHCb has performed many measurements in B + c physics in Run I Most precise mass and lifetime measurements. Many decay modes observed: J/ψ 3π, J/ψ K, ψ(2s)π, J/ψ D ( )+ s, J/ψ 2Kπ, J/ψ 3π2π, B s π,... New modes being investigated, especially charmless weak annihilation types. Searches for excited B c states ongoing as well. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

29 Summary Summary: B + c LHCb LHCb has performed many measurements in B + c physics in Run I Most precise mass and lifetime measurements. Many decay modes observed: J/ψ 3π, J/ψ K, ψ(2s)π, J/ψ D ( )+ s, J/ψ 2Kπ, J/ψ 3π2π, B s π,... New modes being investigated, especially charmless weak annihilation types. Searches for excited B c states ongoing as well. 5 statistics after Run II (end-2018). Much more data coming!. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

30 Backup The LHCb Detector components Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

31 Backup A Λ 0 b J/ψ pk event Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

32 Backup A Λ 0 b J/ψ pk event in the VeLo Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

33 Backup The LHCb Detector components Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

34 Backup Pentaquarks in Λ 0 b J/ψ pk PRL 115, Λ b J/ψKp Dalitz plane LHCb P c 's Λ*'s LHCb LHCb Original goal was precise measurement of the Λ 0 b lifetime (PRL ) Unexpected structure seen in m(j/ψ p). Λ reflections or true resonance(s)? Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

35 Backup The extracted moments in the data filter out maximum spin depending depending on m Kp bin Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

36 Backup Λ 0 b J/ψ pπ : N resonance models LHCb-PAPER N(1535) is a Flatte for nη opening All others are Breit-Wigners with masses and widths fixed to PDG (varied in systematic studies). 15 N states. Reduced (RM): central values. Extended (EM): syst. + signif. NR S-wave pπ for threshold enhancement. 1/m 2 mass-dependence. K-matrix model for 1 2 S-wave from Bonn-Gatchina ( ). Λ 0 b J/ψ ( pπ ) is isospin violating and supressed is [ud] in Λ 0 b is spectator I = 0 diquark. Not considered. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

37 Backup Λ 0 b J/ψ pπ : resonance models LHCb-PAPER Each N has 4(6) individual LS coupling for spin 1/2(higher) Extended Model : all 15 3-star and 4-star resonances and maximal LS couplings. Used for quoting minimum significances and systematics. Reduced model : 6 well-established N s and L s that are significant. Used for nominal results. P c and Z c (4200): mass, widths and couplings to J/ψ p/j/ψ π fixed from previous higher statistics analyses. Z c (4300): only 0.6σ significant and goes into systematics. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

38 Backup Λ 0 b J/ψ pπ : only N states LHCb-PAPER LHCb preliminary m pπ >1.8 Extended model, only N states. 6.6σ exotic significance if only established states are used. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

39 Backup Λ 0 b J/ψ pπ : K-matrix S-wave LHCb-PAPER LHCb preliminary m pπ >1.8 Instead of isobar model, K-matrix model for the dominant S-wave from Bonn-Gatchina. Conclusions invariant on significances. Goes into systematics. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

40 Backup Λ 0 b J/ψ pπ : N angles LHCb-PAPER Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

41 Backup Λ 0 b J/ψ pπ : P + c angles LHCb-PAPER Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

42 Backup Λ 0 b J/ψ pπ : Z c angles LHCb-PAPER Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

43 Backup Λ 0 b J/ψ pπ : Z c angles LHCb-PAPER Efficiency Corrected Signal Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

44 Backup Λ 0 b J/ψ pπ : Fit fractions LHCb-PAPER Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

45 Backup Λ 0 b J/ψ pπ : fit quality LHCb-PAPER Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

46 Backup Λ 0 b J/ψ pπ : significances LHCb-PAPER EM : includes two high mass, low-spin N states observed by BES III (PRL 110 (2013), ), but excludes spin > 9/2, which are suppressed at high m pπ. Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

47 Backup Pentaquark interpretations and outlook Tightly bound quarks? Colored diquark-triquark (Lebed), colored diquark+anti-quark (Maiani). Meson-baryon molecules with meson-exchange binding? Karliner-Rosner: narrow P c (4450) very close to Σ c D. Rescattering effects: P c (4450) just above [χ c1 p] threshold (Guo). Reproduces phase-motion of P c (4450), but what about P c (4380)? Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

48 Backup Pentaquark outlook (cntd.) Experimental program: new decay modes and production mechanisms. Confirmation by other experiments. Where are the ground states? Different final states: Υ J/ψ p p, B 0 J/ψ p p, Λ 0 b J/ψ pπk 0 S. New open-charm and charmless decay modes of P c : Λ 0 b χ c1(1p)pk, Λ 0 b Λ+ c D 0 K, Λ 0 b Σ+ c D 0 K Pentaquark multiplets: Λ 0 b J/ψ pπk S 0. Λ0 b J/ψ Λφ Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

49 Backup B + J/ψ φk + angles Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

50 Backup B + J/ψ φk + fit quality in the angles Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

51 Backup B + J/ψ φk + : cusps Opening of threshold, not necessary bound molecular states can cause peaking -like structures. Coupled-channel cusp models, Swanson: , Internal L = 0, so Isobar Cusp Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26

52 Backup K + summary for B + J/ψ φk + Robust tapestry of K states from amplitude analysis 1 + : dominant, w/ K 1 (1650) at 7.6σ. 2 : two resonances consistent w/ K 2 (1770) and K 2 (1820) 1 : First observation of K (1680) φk 2 + : 5.4σ evidence for a broad resonance consistent w/ K (1980) 0 : 3.5σ evidence for the earlier observed K0 (1830) Biplab Dey Hadron Spectroscopy & B c June 16 th, / 26