Summary of the Workshop on Exotic Hadrons Tomasz

Summary of the Workshop on Exotic Hadrons Tomasz Skwarnicki Syracuse University 6 th International Conference on New Frontiers in Physics, Κολυμβάρι, Ελλάδα, 26 August 2017

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 2 Workshop program Monday Aug 21: Light hadron exotics Wednesday Aug 23: Phenomenology of exotic hadrons Tuesday Aug 22: Heavy-quarkonium-like exotics (experimental)

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 3 Conveners: Alex Bondar, Budker Institute of Nuclear Physics, Novosibirsk, Russia Roman Mizuk, Lebedev Physical Institute, Moscow, Russia Tomasz Skwarnicki, Syracuse University, Syracuse, NY, USA This talk • Use elements of various talks given at the workshop to illustrate status of exotic hadron spectroscopy • Neither a complete review of the field nor of all the talks given at the workshop • I apologize to the workshop speakers not mentioned in the summary • All talks were interesting and we often had animated discussions Indicates the speaker’s name for material copied from a workshop talk See this talk for more details

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 4 “Exotic” multiquark states conceived already at the birth of Quark Model … … Murray Gell. Mann George Zweig

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 5 QCD = QCD q=u, d, s, 1 F q ( i D - m ) q - F q 4 c, b, t 1973 Hugh David Politzer Frank Wilczek David Gross SU(3)color Gluons with color-anticolor charge Asymptotic freedom Hadron sizes Confinement V(r) V~ r V~1/r Static qq potential in Lattice QCD LQCD O. Solovjeva’s talk We have to rely on data and QCD-motivated phenomenology when trying to understand more complex hadronic structures. 1/10 0. 5 1 1/0. 4 1. 0 [fm] 1/0. 2 [1/Ge. V]

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 6 Mesons from quarks & antiquarks in QCD color octet color triplet 3 color antitriplet _ 3 quark antiquark q q Color flux tube stretched between quark and antiquark with attractive potential color singlet 1 8 attractive color force (qq) meson e. g. K+ _ s u repulsive color force quarks will pull apart in any _ octet configuration gluons happen to belong to the color octet

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 7 (Colored) diquarks in QCD color sextet (symmetric) (antisymmetric) color antitriplet color triplet 3 quark q _ 3 3 6 quark q repulsive color force attractive color force _ quarks will pull apart in any sextet configuration (half as strong as in the meson) Color flux tube stretched between the quarks and extending to other color partners (qq) diquark s u Not a particle, just a building block in QCD Diquark can go in a place of antiquark in a hadron; antidiquark in place of quark. See Maiani’s talk

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Diaquarks can make tetraquarks! color triplet color antitriplet 8 color singlet _ 3 However, it is not clear if an efficient mechanisms to suppress the fall-apart mode to two mesons exists, especially when all quarks are light. 1 3 attractive color force _ attractive color force (qq) diantiquark (qq) diquark q q Color flux tube stretched between the diquark and diantiquark ((qq)) tetraquark _ s _ u d s d _ s _ u s

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Conventional and “exotic” hadrons Conventional Weak binding. Large systems. Strong binding. Compact systems. _ u s (sq) K meson s d n p K- d d u u d u (u(ud)) (u(dd)) deutron u p _ s u u d u (u(ud)) (su)) KN molecule K- K+ _ s u _ _u s ((sd)u) L baryon Meson and baryons motivated Quark Model and QCD Baryonic molecules exists! 9 “Exotic” Strong binding. Compact systems. u d _ d s u s ((q(sq))(qq)) pentaquark (sqg) Hybrid meson _ u _ _ u s s u (gg) ((sq)) Glueball tetraquark Are molecular forces in such QCD predicts attractive forces in Firmly some of such configurations. systems strong enough to expected Do they live long enough to produce create bound states, or in QCD observable states/effects ? pronounced effects? (sq) KK molecule

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 10 Tetraquarks vs meson-meson molecules • The same quark content can, in principle, create a meson-meson molecule or a tetraquark • However, mass spectrum from these two types of bindings are very different ((qq)) tetraquark (qq)-(qq) meson-meson molecule _ u d _ _ u u _ u d s V(r) We don’t know if either one exist (“exotic hadron”) Very rich mass spectrum expected! … However, states can be undetectable if extremely broad. r s See Karliner’s talk on Wed. Typically expect only one state n=1, L=0. Fall apart prevented by spatial separation – long-lived states if below threshold. Mass and JP fairly constrained from the constituents.

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 11

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 12 N(1685) confirmed, N(1728)? i. e. pentaquark blinded Studies in progress: Proton target

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 13 Defamed Q(1540)+ blinded A 2 experiment

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 14 d*(2380) dibaryon candidate d u d u ?

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 15 Double-pole structure of L(1405) A 2 expects to improve over earlier photo-production experiments n s d d d u u _ s d K 0 See also Noumi’s talk (J-PARC)

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 16

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 17

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 18 Glueball studies in BES III LQCD See also Y. M. Cho’s talk

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 19 Beginning of XYZ saga Preference for gy’ over g. J/y points to 23 P 1 component cc 1’ ? Phys. Rev. Lett. 91 (2003) 262001 The most cited Belle paper (1369 citations) due to m(D 0)-m(D-)? Molecule? … y(2 S) DD* Belle very narrow GX(3872) <1. 2 Me. V Molecule? DD X(3872) JPC=1++ Molecule? Large isospin violation in these decays, Molecule?

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 20 Prompt production of X(3872) Wednesday talks/discussion: Can’t be a molecule! It is a tightly bound-tetraquark. Agree, can’t be a pure molecule! It is a mixture of a molecule and 23 P 1 charmomium. and many others including: Talk by Constituent QM supplemented with couplings to meson-meson states Pablo Ortega See also Xiao’s talk Me. V % % %

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 21 Can a large molecule mix with a compact charmonium? 014019 Wednesday discussion session: For such a long-lived state as X(3872), even small overlap of wave functions can lead to mixing It is not plausible for such a large molecular state to mix with such a compact charmonium state Alex Bondar

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 22 Adopted from Michael Pennington’s slides at Modern Exotic Hadrons INT 15 -60 W workshop November 2015

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay 23

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay 24

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay 25

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay 26

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay 27

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay 28

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Resonance decay This can sometimes lead to Dynamically generated state; an extra pole in the scattering matrix 29

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki K Zc + 30 Discovery of Z(4430)+ y’ PRL 100, 142001 (2008) 1 D M(y’ -) mass fit K*(892) First charged charmonium-like state discovered! neutral charged Belle 2008 K* B y’ +K T. Skwarnicki (Tue. ) K*2(1430) “K* veto region”: suppress K*(892) and K*2(1430) Z(4430)+ K* K + bkg. Z(4430)+ non-B bkg [ y’ ≡ y(2 S) ] d Exotic tetraquark, molecule, … not Standard charmonium

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 31 LHCb confirmed Zc(4430)+ in 2014 Breit-Wigner amplitude Z(4430)- LHCb Belle Much wider, bigger errors, than in the naïve mass fit! 4344 = 4277 Me. V 4411 JP=1+ 9. 7 s 3. 4 s Excellent agreement ! 4475 (“K* veto region”) 4605 4541 2 nd Z- at lower mass? JP=0 - JP=1+ also possible G=660± 150 Me. V Two Zc 2 p-value =26% One Zc 2 p-value =12% Argand diagram of Zc(4430)+ is consistent with this structure being a resonance T. Skwarnicki (Tue. )

32 B 0® J/y p+K- in Belle 5. 1 s Belle PR D 90, 112009 (2014) 4 D amplitude analysis Zc(4430)+ J/y + Negative interference Zc(4200)+ J/y + Zc(4200)+ No Zc(3900)+! Belle 6. 2 s JP=1+ 4. 4 s Tetraquark or meson-meson molecule Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Small fit fractions! • • The Zc(4430)+ observed in the 2 nd decay mode! A broad but significant 2 nd 1+ resonances at the lower mass, Zc(4200)+ log scale – Possibly the same structure as observed by the LHCb in B 0 y’ +K- (1+ was not ruled out by LHCb) Kaon excitations T. Skwarnicki (Tue. )

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 33 Proliferation of near-threshold states: Zb+, 0 states in bottomonium 5 Mass Me. V Masses near the BB*, B*B* thresholds Zb(10650) Zb(10610) B*B* BB DMth=+3± 2 Me. V (3 S) Belle PRL 108, 122001 (2012) (2 S) M( (n. S)π+)max Me. V Both JP(C)=1+(-) Charged and neutral versions detected I G=1+ _ _u b 10, 650 Me. V 10, 610 Me. V G ⋎ ⋎ ⋎ (1 S) Large rate to fall-apart modes observed _ b d See Bondar’s talk ⋎ • Likely molecular states of BB*, B*B* (very weakly bound or slightly virtual) • Tightly bound diquark tetraquarks advocated by Maiani and collaborators Karliner’s talk Maiani’s talk

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki More near-threshold states: many of Zc+, 0 charmonium states Y(4260) 4200 D*D* DMth=+7± 2 Me. V DD* DMth=+11± 3 Me. V Zc(3900) 21 S 23 S 1 0 13 P 11 P 1 DD Expected from Zb states and Heavy Quark Symmetry G Me. V ⋎ ⋎ JP(C)=1+(-) (established only for Zc(3900)) ⋎ Large rate to fall-apart modes 0, 1, 2 ⋎ 3400 Zc(4020) BES-III 13 S 1 3000 • Masses a few Me. V above the DD*, D*D* thresholds Zc(4020) 3800 34 Zc(3900) _ _u c Zc(3900) 11 S 0 See Lyu’s talk _ c d Zc(3900) Charged and neutral versions detected I G=1+ (also seen be Belle) Molecular states of DD*, D*D* ? Diquark tetraquarks ? Karliner’s talk Maiani’s talk

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 35 Good discussion about Zb and corresponding Zc states • Why the differences in decay pattern of Zb and Zc states? – Some of it can be misinterpretations of the data e. g. Xiao-Rui Lyu New Zc states? y(2 S) + Alex Bondar

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki First observed by Ba. Bar in 2005 Anomalous 1 -- states above open charm threshold BESIII PRL 118, 092001 (2017) Belle PRL 110, 252002 (2013) + - Y(4260) J/y log scale y(2 S) 36 Y(4260) “Y(4222)” + - Y(4360) ? J/y Famous Y(4260) is now Y(4220)+Y(4320) Ba. Bar PRD 86, 051102 (2012) Y(4260) Belle PRD 91, 112007 (2015) + - Y(4360) J/y Y(4660) + - y(4020) y(4415) y(3770) y(4160) 33 S 1 3 1 D 1 23 D 1 43 S 1 BESIII PL B 660, 315 (2008) hadrons y(2 S) For much more on this see Z. Wang’s talk BESIII PRL 118, 092002 (2017) + hc Y(4660) ? Belle PRL 101, 172001 (2008) Lc + Lc -

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Anomalous behavior of 1 -- states above open bottom threshold bb _ 37 (5 S) (6 S) Roman Mizuk hb(1 P) + – (1 S) + – hb(2 P) + – (2 S) + – PRL 117, 142001(2016) PRD 93, 011101(2016) e+e– (1 S, 2 S, 3 S) + – and hb(1 P, 2 P) + – proceed via (5 S), (6 S) Unlike in charmonium! (3 S) + – However, (5 S), (6 S) (1 S, 2 S, 3 S) + – widths are 100 larger than (3 S), (2 S) (1 S) + – OZI-rule violation Also widths for (5 S), (6 S) hb(1 P), hb(2 P) + – are comparable, but require heavy quark spin flip HQSS violation Like in charmonium!

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki OZI light d. o. f. Interpretation? b _ q q _ b 38 + – Roman Mizuk compact tetraquark __ hadronic admixture _ _ hadroquarkonium _ _ – V V V – – (bq) Bottomonium-like states open flavor decays dominate transition to various bottomonia admixture + rescattering (bq) (bb)(qq) Enhanced if _ B (* ) Simonov JETP Lett 87, 147(2008) Meng Chao PRD 77, 074003(2008) Molecules are not eigenstates of the total bb spin _ Zb = BB* _ IG (JP ) = 1+ (1+ ) Zb = B*B* Zb Bondar, Garmash, Milstein, RM, Voloshin, PRD 84, 054010(2011) Decomposition hb(m. P) are on-shell (n. S) Decays via Zb states explain HQSS violation

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 39 Interpretations of Zc+ states observed in B decays GD(2600)=104± 20 Me. V D 11 S 0 D*(2600) 23 S 1 Radial excitation of the 3 S 1 meson inside meson molecule 1 D 1 S 0 _ _u c 3 D* 1 S 1 _ c d L. Ma et al PRD 90, 037502 (2014) T. Barnes et al, PRD 91, 014004 (2015) GZ(4430)=181± 31 Me. V Zc(4430)+ 1+ Radial excitation of tightly bound _ tetraquark (no neutral partner has been observed yet) _ Zc(4200)+ + 1 (needs confirmation) GZ(3900)= 28± 3 Me. V Zc(3900)+ 1+ u c L. Maiani et al PR D 89, 114010 (2014) [cu]S=1 [cd]S=0 - [cu]S=0 [cd]S=1 Absence of Zc(3900)+ in B decays makes it questionable to pair it up with Zc(4430)+ No molecular thresholds can explain Zc(4200)+ _ d c _ While it has been suggested Zc(4200)+ is a tetraquark, no tetraquark model can accommodate it together with Zc(4430)+ C. Deng et al PR D 92, 034027 (2015) Zc(4200)+ needs confirmation! T. Skwarnicki (Tue. )

B-®J/y f K- 6 D amplitude analysis 40 LHCb PRL 118, 022003 (2017) X(4700) J/yf 5. 6 s X(4140) first observed by CDF PRL 102, 242002 (2009) 6. 0 s 6. 1 s X(4500) J/yf X(4274) J/yf X(4140) was previously observed by CDF, CMS, D 0. Hints of X(4274) in CDF data. Kaon excitations Not enough data to test resonant amplitudes on Argand diagrams. See T. S. (Tue. ) _ _ s c S c X(4700) ++ No h-exchange 0 +69± 26 Me. V Ds 0+Ds 0*- Plenty of other thresholds, but no matching JPC numbers _ u s 8. 4 s X(4140) J/yf Tetraquarks or Ds. Ds molecules Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki _ _s c _ c s No -exchange forces! h-exchange OK Ds+Ds* - +66± 5 Me. V X(4500) 0++ X(4274) 1++ X(4140) 1++ Postdiction by L. Maiani, A. D. Polosa, V. Riquer PRD 94, 054026 (2016) Possibly radially excited 0++ tetraquarks. However, only one 1++ state with color triplet diquarks. F. Stancu, J. Phys. G 37, 075017 (2010) Predicted two 1++ tetraquarks in this mass range (S=0, 1 diquarks in color triplet and sextet)

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki Lb 0 J/yp. K- Pc(4450)+ J/y p Pc(4380)+ J/y p See Liming Zhang’s talk Karliner, Rosner PRL 115, 122001(2015) and others Pc(4380)+ + *0 p cc 1 Sc D +1± 3 Me. V s d Sc Pc broad to be a molecule + u Pc(4450)+ - 10± 3 Me. V (4380)+ is too d c L baryon excitations Pc(4450)+ No -exchange u _ 5 D amplitude analysis Pentaquark or baryon-meson molecule PRL 115, 07201 (2015) 41 _ u c D*0 Pc(4380)+ or JP “preferred” rather than definitely determined Maiani et al PLB 749, 289 (2015) and many others Such mass difference and the opposite parity can be explained by DL=1 u c _ c d u

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 42 Misha Mikhasenko Possibility of triangle anomalies should be explored via amplitude fits to the data which yielded XYZ, Pc states.

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 43 Doubly heavy systems c tetraquark d baryon b u b c u LHCb PRL 111, 180001 (2017) The lightest 1+ state Marek Karliner the same toolkit Karliner, Rosner ar. Xiv: 1707. 07666 Stable tetraquark, will decay weakly Karliner, Rosner PRD 90, 094007 (2014) See also Chen’s talk on quadruple-heavy tetraquarks Consistent results predicted by LQCD: Francis, Hudspith, Lewis, Maltman PRL 1118, 142001 (2017)

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 44 Summary I New narrative Old narrative (before 2003) (from: ar. Xiv: 1708. 04012)

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki _ _ u c d c Claim most (all? ) of XYZ states are tetraquarks or pentaquarks 45 Summary II (Aug 23, Wednesday session) Luciano Marek Sonja Maiani Karliner Kabana Predict prompt production of all XYZ states at hadron colliders No width predictions so far _ c u Proliferation of threshold states is the main feature of this model (supported also by lighter meson spectroscopy). Narrow widths expected! Necessarily claim there are many more to be discovered Proliferation of threshold states requires mixing with virtual hadron pairs _d c_ _ _ b b d u Everybody agrees, the lightest 1+ is stable Crucial difference. Lack of experimental reports on prompt production of most of XYZ, Pc states anecdotally favors molecular forces (need experiments to publish limits!) Cannot account for some observed XYZ, Pc states. Leave room for other dynamics to play a role. More threshold states expected, but predictive power somewhat limited. No agreement on exact dynamical model (only exchange? ). No prompt production, unless mix with compact hadron.

Summary of the Workshop on Exotic Hadrons, Kolymbari 2017, Tomasz Skwarnicki 46 Summary III • Need more data to settle the phenomenological BES III disputes See K. Zhu’s talk • More data are forthcoming! Upgraded LHCb CMS ATLAS CLAS 12 PANDA and other…