Heavy Quark Spectroscopy at LHCb

Transcription

1 Heavy Quark Spectroscopy at LHCb Tomasz Skwarnicki On behalf of the LHCb Collaboration Moriond QCD, LaThuile, 2015

2 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 2 Outline of the talk Masses of χ b (3 3 P J ) states LHCb-PAPER July 2014, LHCb-PAPER Sept Orbital angular momentum in X(3872) ρ 0 J/ψ and X(3872) J PC LHCb-PAPER new Radiative decays of X(3872) LHCb-PAPER Apr 2014 Z(4430) + π + ψ(2s) in B 0 decays LHCb-PAPER Apr 2014, new in B s decays LHCb-PAPER Results on D s ** states LHCb-PAPER and -037 July 2014 Results on D** states LHCb-PAPER Mar Results on B** states LHCb-PAPER Feb Results on Ξ b * states LHCb-PAPER Nov new new

3 MeV Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki í 1977 h b 2012 h b h b 2008 Long-lived heavy quarkonia and χ b (3 3 P J ) states n 2S+1 L J 1985 r n h b 2012 χ b 2012 χ b 1982 c b 1983 Hyperfine splitting: Fine splitting: ur ur L S, ur uur ur uur s r$ s r$ s s uur uur S S 1 2 S= L= Non-relativistic system s 1 2M B r r r S=s 1+s2 Theoretical approaches: potential models, NRQCD, lattice QCD L r J = L r + S r L S J L+S P = (-1) C = (-1) Since χ b (3 3 P J ) states are very near the open flavor threshold, it has been speculated that couplings to virtual B ( * ) B ( * ) pairs could drastically affect their masses and decay properties with respect to the expectations for pure bb states (see e.g. Ferretti, Galata, PRD90, (2014) ). Karliner, Rosner PRD91, (2015) proposed that χ b (3 3 P 1 ) could have a substantial component of I=0 BB* molecule (X b ) s 2 L+1 L+S

4 pp χ b (n 3 P J )+ γ E1 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 4 Masses of χ b (3 3 P J ) states Photons detected in calorimeter LHCb-PAPER Eur.Phys.J. C74, 3092 (2014) χ b (1 3 P J ) γ (1 3 S 1 ) χ b (2 3 P J ) γ (1 3 S 1 ) χ b (2 3 P J ) γ (1 3 S 1 ) χ b (3 3 P J ) γ (2 3 S 1 ) χ b (3 3 P J ) γ (1 3 S 1 ) LHCb 7 TeV 1 fb -1 χ b (1 3 P J ) γ (1 3 S 1 ) χ b (2 3 P J ) γ (1 3 S 1 ) χ b (2 3 P J ) γ (1 3 S 1 ) χ b (3 3 P J ) γ (2 3 S 1 ) χ b (3 3 P J ) γ (1 3 S 1 ) LHCb 8 TeV 2 fb -1 Converted photons LHCb-PAPER JHEP 1410, 88 (2014) LHCb 3 fb -1 LHCb 3 fb -1 χ b (3 3 P J ) γ (1 3 S 1 ) χ b (3 3 P J ) γ (2 3 S 1 ) (m 3 S 1 ) µ + µ χ b (3 3 P J ) γ (3 3 S 1 ) χ b (3 3 P J ) γ (3 3 S 1 ) 2M B The measured mass of the χ b (3 3 P 1 ) state is within a few MeV of the potential model predictions which are up to 26 years old! It appears that coupled-channel corrections are either small or well absorbed into an effective potential adjusted to the experimental data on the other bb states The measured ratios of transition rates also consistent with the expectations

5 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 5 predicted measured X(3872): state at the D 0 D 0 * threshold ψ(2s) DD DD* Belle X(3872) 34±7 events PRL 91, (2003) B X(3872)K, X(3872) J/ψ π + π, J/ψ l + l C=+ since X(3872) J/ψγ (and ψ(2s)γ) have been observed Mass shifted χ c (2 3 P 1++ )? 4-quark state? DD* Molecule? 2 3 S 0 η c (2 1 D 2-+ )? 1 D D D S 1 OK 1 3 D 3 short-lived long-lived 1 3 P P P P 2 X(3872) 1 3 P P 2 DsDs * DD DD lattice DD experiment 1 3 S 1 Hadron Spectrum Collaboration (L. Liua et al.) JHEP 1207, 126 (2012). Unquenched Reasonably lattice accurate QCD calculations predictions of for the the long-lived states Discrepancies with the data above the open flavor threshold charmonium masses with dynamical charm quarks. Sensitive to hybrid (qqg) contributions but not to 4- quark structures. 1 1 S 0 η c ψ η c ψ χ c h c χ c χ c

6 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 6 L in X(3872) ρ 0 J/ψ and determinations of X(3872) J P LHCb preliminary 3 fb -1 LHCb data X(3872) ρ (770)J/ψ MC All previous determinations of J P (CDF PRL 98(2007)132002, LHCb-PAPER PRL 110 (2013) fb -1 ) assumed the lowest possible orbital angular momentum in X(3872) π + π J/ψ decays 2 m π m π+π Q<250 MeV selection cut low Q π+π = m X(3872) m J/ψ Q [MeV] /ψ Q=0 low p of decay products Standard charmonium small r Molecule large r low L L =? Orbital angular momentum: L = r p Conservation of parity: L = L min, L min +2,... (L min value depends on J P ) Significant L > L min could: invalidate the previous J P =1 + assignment hint molecular structure of X(3872)

7 B + X(3872)K +, X(3872) J/ψ π + π, J/ψ µ + µ Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 7 Determination of X(3872) J PC : formalism φ φ x,j/ψ ρ φ φ x,ρ 5 independent angles describing the decay in helicity formalism Matrix element Relation of the helicity couplings to LS amplitudes Parity conservation LHCb 2015 L CDF 2007 Many more amplitudes to fit LHCb 2013 LS amplitudes to be determined from the data

8 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 8 New determination of X(3872) J PC LHCb-PAPER new B + X(3872)K +, X(3872) J/ψ π + π, J/ψ µ + µ Likelihood-ratio test: data vs simulated experiments LHCb preliminary 3 fb -1 X(3872) 1011±38 events t data LHCb preliminary 3 fb -1 t = Data unambiguously prefers 1 ++ hypothesis (new: no assumptions about L) t t

9 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 9 Determination of D-wave fraction in X(3872) ρ 0 J/ψ for J PC = Fit to the real data: B2 1 B22 = ± = ± B B LHCb-PAPER new D-wave significance using Wilks theorem applied to the likelihood ratio with/without D: 0.8σ D-wave amplitudes are consistent with zero. Gaussian part of the likelihood: f D peak =0.4% (σ=0.3%) LHCb preliminary 3 fb -1 Non-Gaussian tail f D <4% at 95% CL 5% prob. No hints for a large size of X(3872) from the studies of the orbital angular momentum in X(3872) ρ 0 J/ψ decays (-) Also the observations of X(3872) in prompt pp production hint the typical charmonium size

10 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 10 Radiative decays of X(3872) in LHCb LHCb-PAPER NP B886, 665 (2014) X(3872) ψ(2s)γ 4.4σ LHCb 90% CL UL LHCb 2014 Measurement of R ψγ =BR(X(3872) ψ(2s)γ)/br(x(3872) J/ψγ) a good probe for internal structure of X(3872) LHCb Signal significance: B + X(3872)K +, X(3872) ψ(2s)γ, J/ψγ 3.6σ, 3.5σ 0.4σ, 4.9σ 4.4σ, 12.0σ BR(X(3872) ψ(2s)γ)/br(x(3872) J/ψγ) = 2.48±0.64±0.29 The LHCb results are consistent with, but more precise than, the BaBar and Belle results The results are not consistent with the expectations for purely molecular X(3872) Mounting evidence that X(3872) has a very significant χ c (2 3 P 1++ ) component

11 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 11 Z c (4430) + : charged four-quark candidate Cannot be confused with a charmonium state because it is charged. The first observed state of that type [Belle PRL 100, (2008)] K* veto region Z(4430) + LHCb-PAPER PRL 112, (2014) K* Kπ + bkg. 4D amplitude fit to Z + K * B 0 ψ π + K - Argand diagram data phase M( Z) = 4475 ± 7 MeV Γ ( Z) = 172 ± 13 MeV 13. 9σ Confirming existence of this state and improving over Belle D amplitude fit results (PR D88, ) No Z(4430) +? LHCb-PAPER J P =1 + preferred by >9.7σ Consistent with a resonant amplitude new Phasespace No significant ψ π + contributions to the amplitude, however the Fit with K* Kπ + only B s0 ψ π + K - statistics are too small to rule out contributions at the level observed in B 0 decays First demonstration of that type for an exotic hadron candidate First observation of such decays

12 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 12 Z c+ (4430) as molecule or rescattering effect?. Z(4430) + ψ(2s) D(2S). +. D*+ B 0 D 0 π + B 0 D D 0 s- (2S) D(2S)=D(2600) Molecular models Recent: L. Ma, X. -H. Liu, X. Liu and S. -L. Zhu, arxiv: T. Barnes, F. E. Close E. S. Swanson, arxiv: K - phase Phase of Breit-Wigner amplitude A Z 2 Phase in the rescattering model. ψ(2s) π + K - Rescattering model by P. Pakhlov, T. Uglov arxiv: Expect Breit-Wigner amplitude in any bound-state model The phase from rescattering runs in the opposite way to the Breit-Wigner amplitude i.e. in disagreement with the Argand diagram obtained by LHCb. Similar mechanisms can be constructed for many exotic hadron candidates, due to various excitations of D,D s systems importance of spectroscopy of heavy-light mesons: Relativistic system L The same number of states expected for r r r j = L+ s q q r r r J = j q + s Q s q r j q s Q r n L+1 P = (-1) each nl as for heavy-heavy systems, but the mass splittings have a different origin Higher excitations have single pion (kaon) transitions to the lower ones Theoretical approaches: semi-relativistic potential models, HQET, lattice QCD

13 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 13 New results on cs states 2 (2573) J (2860) 2 (2573) Pure J=2 confirmed 1P 2 state LHCb-PAPER and -037 PRL 113, (2014) PRD90, (2014) J (2860) 1D 1,3 states Dalitz analysis of The 2860 peak resolved into J=1 and 3 resonances (first J=3 state observed in B decays) Good illustration of the power of the amplitude analysis

14 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 14 New results on cq (q=u,d) states J=2 confirmed 1P 2 state J (2860) LHCb-PAPER Mar new 1D 1 state Dalitz analysis of First observation of this final state J=1 established

15 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 15 New results on bq states LHCb-PAPER Feb new Simultaneous fit to all 6 histograms

16 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 16 New results on bq states High-Q peaks: LHCb-PAPER Low-Q peaks: Well established before. Improved m,γ measurements.

17 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 17 New results on bsq baryons Predicted L=0 bqq SU(3) flavor multiplets: qq qq qq LHCb-PAPER Nov PRL 114 (2015) Fully reconstructed cascade decays: Two missing states discovered. Angular analysis consistent with the expected J P, but cannot rule out other options. Masses precisely determined. Width of Ξ* b- measured. Upper limit on Ξ b- width.

18 Heavy Quark Spectroscopy at LHCb; Moriond QCD 2015 T.Skwarnicki 18 Summary of LHCb results Studies of prompt production of radiatively decaying χ b (3 3 P J ) states: These just below the BB threshold states have masses and photon transition rates consistent with the expectations for pure bb states Studies of radiative decays of X(3872) and of orbital angular momentum in ρ 0 J/ψ decays: This at the DD* threshold state has properties consistent with a significant χ c (2 3 P 1 ) component Amplitude analysis of Z(4430) + : This state exists and its amplitude phase variation with the mass is consistent with an exotic four-quark bound state Many new results on heavy-light states: D s **,D**,B** Understanding of their mass spectra is important for meson pair contributions in theoretical models related to the exotic hadron candidates Two new beautiful and strange baryons observed: Demonstrate still largely untapped potential of LHC for baryon spectroscopy (do baryonic exotic hadrons exist?)

19 Status of heavy quark exotic hadron spectroscopy 5min summary on request by the organizers

20 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 20 Abundance of QQqq candidates Very reach experimental field: data from 6 different colliders DD * D*D From S. Olsen, arxiv: DD 1 D s* D * s D s D s * CLEO 12 years after the discovery of X(3872) we have ~9 neutral and ~7 charged QQqq candidates. Some states observed by more than one experiment or in more than one decay/production Most masses are close to M[Qq(nL Jj )]+M[Qq(n L J j )] values: Molecules? Scattering cusps? Coincidence?

21 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 21 XYZ states: some of the proposed bound state models Plain Tertaquark Hybrid Diaqonium Very reach phenomenological field Hydrocharmonium Meson molecule Many calculations tailored to specific states. Often qualitative rather than quantitative predictions. No definite theoretical picture emerging. More than one mechanism can be at play. Only immature lattice QCD calculations so far.

22 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 22 Roadmap Experiments: clean-up and survey of existing states: confirmations, new decay modes (non-observations are also important) there must be more states to discover precision phase evolution studies (amplitude fits, PWA) as improvement over peakology (though there are also dangers of fitology ) need high statistics data pursue heavy-light spectroscopy since it impacts heavy-heavy states (including exotics) above the open flavor threshold All existing and new facilities will contribute (higher luminosity charm and beauty e + e -, upgraded LHCb, ) Theory: phenomenological models are helpful, especially if they have predictive rather than postdictive power, but need serious effort to move lattice QCD with dynamical charm quarks and 4-quark couplings way above the open flavor threshold

23 Light hadrons Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 23 Summary

24 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 24 Summary Light hadrons x3= qq, qqq,

25 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 25 Light hadrons x3= 8+1 Summary 1964 qq, qqq, Long-lived charm & beauty onia qq! Precision spectroscopy from the fundamental theory: lattice (NR)QCD

26 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 26 Light hadrons x3= 8+1 Summary 1964 qq, qqq, Long-lived charm & beauty onia qq! XYZ states Back to the ZOO Precision spectroscopy from the fundamental theory: lattice (NR)QCD

27 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 27 Light hadrons x3= 8+1 Summary 1964 qq, qqq, Long-lived charm & beauty onia qq! XYZ states 2003-, qqqq Back to the ZOO Precision spectroscopy from the fundamental theory: lattice (NR)QCD

28 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 28 Light hadrons x3= 8+1 Summary 1964 qq, qqq, Long-lived charm & beauty onia qq! XYZ states 2003-, qqqq Back to the ZOO qqg?, qqqqq? Precision spectroscopy from the fundamental theory: lattice (NR)QCD Pentaquarks

29 Exotic Heavy Quark Spectroscopy; Moriond QCD 2015 T.Skwarnicki 29 Light hadrons x3= 8+1 Summary 1964 qq, qqq, Long-lived charm & beauty onia qq! XYZ states 2003-, qqqq Back to the ZOO qqg?, qqqqq? Precision spectroscopy from the fundamental theory: We still have to face all the lattice (NR)QCD consequences of the Quark Model and strongly coupled QCD Heavy flavor hadrons (QQ,QQqq,QQg,QQqqq) offer the best playground to face this challenge Pentaquarks