Issues in hadron spectroscopy Stephen Lars Olsen Seoul

Issues in hadron spectroscopy Stephen Lars Olsen Seoul National University 2011 International Workshop on Nuclear, Particle and Astrophysics High-1, Korea, February 7 -10, 2011

Standard Model QCD Electroweak qj qj’ as~10 -1 qi QED gij eight “gluons” GF~10 -5 W±, Z a. QED ~10 -2 g photon qi • Perturb. calcs. are unreliable • Perturbative calculations are very reliable • Theoretically poorly understood • Theoretically well defined • Experimental tests minimal • Experimentally well tested

QCD diagrams for gg Higgs 2 nd order ~70% 1 st order +…

QCD calculations are difficult ● N=6 → 10860 Feynman diagrams ● N=7 → 168 925 Feynman diagrams

Compare to QED process (g-2)m 1 st order 2 nd order ~1% 3 rdorder ~0. 01%

Ultimate theory limitation: hadrons Don’t calculate use e+e- hadrons &/or t hadrons n data + dispersion rel’ns had Vacuum polarization had No similar accessible process (ultimate limit on theory precision? ) Light-by-light scattering

Neutrino mass AMo. RE expt, etc: “Only way to measure neutrino mass” This is what we’ll measure (if we are incredibly skillful & fortunate) This is what we want Phase-space integral Nuclear matrix element Now there is no way to relate to 2 from 1 st principles.

Quark model for hadrons (pre-QCD)

Original Quark Model 1964 The model was proposed independently by Gell-Mann and Zweig Three fundamental building blocks 1960’s (p, n, l) Þ 1970’s (u, d, s) mesons are bound states of a of quark and anti-quark: Can make up "wave functions" by combining quarks: baryons are bound state of 3 quarks: proton = (uud), neutron = (udd), L= (uds) anti-baryons are bound states of 3 anti-quarks: Λ= (uds) 9

Make mesons from quark-antiquark __ uss _ ds d _ du_ _ sd _ dd _ uu u ss s u __ d ud _ su _

Mesons come in octets JP=0498 JP=1 - 494 892 896 K*+ K*0 135 548 139 776 783 r- r 0 w 776 r+ 776 f 958 1020 494 K*- 498 892 (p+, p 0, p-)=lightest _ K*0 896 (r+, r 0, r-)=lightest nr=0 S w av e

Construct baryon octets and decuplets Fom combinations of three uds triplets duu uuu d d u u u d s uus s s HW: Finish the procedure

Answer: 8 -tet 10 -plet dud ddd sdd uud sud sud ssd ssu sss uud suusuu

Baryons come in octets & decuplets 939 938 M=1232 Me. V 1115 1189 M=1385 Me. V 1197 1192 M=1533 Me. V 1315 1321 M=1672 Me. V JP=1/2+ es all S av -w JP=3/2+ all nr=0 S all s ve a -w all nr=0 14

Problems with the quark model: • Individual quarks are not seen y b ” D C Q • why only qqq and qq combinations? “F d e x i • violation of spin-statistics theorem?

st 1 principle QCD bound state calculations are impossible. Hadron (& nuclear) physics processes occur here Pentaquark? At these distance scales, as≈0. 5 this is a minimal diagram; no penalty for adding any number of additional gluons

Is it hopeless?

no In principle, Lattice QCD can do it all But computing requirements are enormous Blue. Gene/L Supercomputer Currently available supercomputers are only able to solve simple problems & even these require approximation techniques Guidance (& encouragement) from experiments is critical

QCD-inspired “new” spectroscopies - from the symmetry structure of theory Pentaquarks: e. g. an S=+1 baryon u d_ u d s dibaryons: tightly bound 6 -quark state (only the anti-s quark has S=+1) Glueballs: gluon-gluon color singlet states _ Tetraquark mesons _ qq-gluon u _c c u hybrid mesons c _ c s ud u ds not a nuclear state

Pentaquarks & the H-dibaryon

quark antiquark? du dd d u s du ud d = s _ 3 3 = 6 3 _ 3 uu ds sd us su s diquark antitriplet attractive us = dd ud sd 6 repulsive uu su diquark antisextet ss ss

Pentaquarks? Exotics D. Diakonov, V. Petrov, and M. Polyakov, Z. Phys. A 359 (1997) 305. __ R. Jaffe & F. Wilczek PRL 91, 232003 (2003) du ds _ 3 antitriplet du _ 3 us ds us antitriplet N*(1440)? _ s _ u _ 3 10 N 0 S- = _ u antitriplet -- S 0 S+ 0 ---- S=-1 + - S=-2 N 0 S- N+ S 0 L L (1405)? See also: Y. S. Oh & H. C. Kim PRD 70, 094022 (2004) ---- S=0 N+ - _ 8 ----- S=+1 Q+ 0 0 ---- S=0 S+ -- S=-1 ------ S=-2 Prediction: M( - -) ≈ 1750~1850 Me. V - - p - | p - L 0

Q+ Pentaquark at Spring-8? Q+ decay modes: Q+ photo-production • Q + K + n • need to deal with the neutron • Q + K 0 p • cannot tag the strangeness K+ Q+ need a neutron target (1 st experiment used 12 C tgt) n u+2/3 s+1//3 -1/3 d u+2/3 d-1/3 S=+1

Results CLAS-D (2005) Q+ K + n ? ? ? ? Width consistent with (11 Me. V) resolution T. Nakano et al (LEPS) PRC 79, 025210 (2009) B. Mc. Kinnon et al (CLAS) PRL 96 212001 (2006)

- - in NA 49 Expt at CERN? L & signals are very clean -p- + -p+ + _ _ + p + +p- M( p)5 = 1862± 2 Me. V G 5<18 Me. V S = 4. 2 s

No sign of X- - in CDF 5 X*(1530) X-p+ No peaks around M(Xp) = 1860 Me. V/c 2 for X-p+ and X-p-

Pentaquark status “Seen” in many other experiments but not seen in just as many others Belle BES Ba. Bar CDF High interest: 1 st pentaquark paper has ~820 citations

Positive pentaquark sightings since 2003

Negative pentaquark sightings since 2003

“The story of pentaquark shows how poorly we understand QCD” – F. Wilczek, 2005

Pentaquarks in a gluon-rich environment less complicated than: (1 S) - - + X (1 S) anti-deuteron + X p n d d _ s u b (1 S) s d b (1 S) b b X X ARGUS: Bf( (1 S) anti-deuteron + X)=3 x 10 -5 an appropriate comparison process A limit on Bf( (1 S) - - + X) below 10 -5 would be “compelling evidence” that Pentaquarks do not exist. Belle data: ~108 (1 S) decays 10 -5 Bf ~1000 produced 10% effic ~100 detected

H dibaryon? d u d s _ 3 d u u s antitriplet _ 3 d s u s antitriplet d u s s u d R. L. Jaffee, PRL 38, 195 (1977): S=-2 di-hyperon with M<2 ML

H dibaryon decay modes MH(Me. V) H - p strong decay (probably wide) 12 C(K-, K+LLX) M + M N (2260 Me. V) C. J. Yoon et al (KEK-PS E 522) PRC 75, 022201 (2007) H LL strong decay 2 ML (2223 Me. V) H L n ML + Mn (2055 Me. V) weak decay most inter esti ng H n n weak decay

What mass is expected? LQCD long-lived ct > 3 cm!! • • 2010

The “Nagara” LL 6 He event 6 LLHe 5 He L H. Takahashi et al, PRL 87, 215502 (1977): MH > 2 ML-7. 7 Me. V

Recent Lattice QCD calculations MH= 2 ML – 16. 1 ± 2. 1 ± 4. 6 Me. V MH= 2 ML – “(30~40) Me. V

Production via gluons X Need to: produce 6 quark-antiquark pairs (including two ss quark pairs) very close in phase space d u s s u d Is this likely? ? ?

Anti-deuteron production Similar process!! d p n

Experimental signatures MH(Me. V) H ~2 Ge. V shower that doesn’t look like a g-ray -p M + Mp (2260 Me. V) x H L n L p n p+ H LL 2 ML (2223 Me. V) H Belle Cs. I detector weak decay 2215 Me. V Ruled out by Nagara? H L n is hard, but H L n is possible in Belle advantage of gluon production is equal rates for H and H

Pentaquark & H-dibaryon searches via gluonic systems with sensitivites below the d production rate should be conclusive.

The “XYZ” exotic meson candidates

Strategy: Search for a meson that decays to a final state containing a c and c quark, If it is a standard qq meson, it has to occupy one of the unfilled states indicated above. If not, it is exotic. predicted measured

cc production at B factories

The X(3872) Study p+p-J/ produced in B K p+p- J/ decays ? ?

The X(3872) B K p+p-J/ ’ p+p-J/ X(3872) p+p-J/ S. K. Choi et al PRL 91, 262001 M(pp. J/ ) – M(J/ )

Its existence is well established seen in 4 experiments CDF 9. 4 s 11. 6 s X(3872) D 0 Ba. Bar X(3872)

X 3872 JPC values Angular correlation analysis by CDF: §Fit to M(pp) favors r p+phep-ex/0505038 JPC = 1++ CDF: PRL 98 132002 PRL 96, 102002(2006) JPC = 1++ or 2 -+

Ba. Bar: X 3872 g. J/ & g ’ B+ K+g. J/ 3. 6 s G(X g. J/ ) 1/10 G(X p+p-J/ ) 1++ g J/ or g ’ Allowed E 1 2 -+ g. J/ or g ’ Suppressed E 2 B+ K+g ’ M(g. J/ ) JPC = 1++ favored over 2 -+ 3. 5 s PRL 102, 132001 M(g ’)

can it be the ++ 1 cc state? 1++ cc 1’ (the only charmonium possibility) M=3872 Me. V is low, cc 1’ p+p- J/ is 3872 Me. V g p +p - (Isospin violating) a forbidden decay cc 1’ g J/ is an allowed E 1 transition; should be stronger than p+p-J/ , not 10 x weaker. If it is not the c’c 1, what is it?

X(3872) looks like a molecule 0 0 D* D

CDF X(3872) p+p- J/ Mass recent results ~6000 events! ar. Xiv: 0906. 5218 MX = 3871. 61 ± 0. 16 ± 0. 19 Me. V

M X(3872) ≈ MD 0 +MD*0 = 3871. 46 ± 0. 19 Me. V new Belle meas. new CDF meas. MD 0 + MD*0 3871. 8± 0. 4 Me. V dm = -0. 35 ± 0. 41 Me. V

X 3872 couples to D*0 D 0 Belle X 3872 D 0 D*0 & ar. Xiv: 08100358 D*→Dγ 414 fb-1 D 0 D 0 p 0 D*→D 0π0 605 fb-1 Ba. Bar X 3872 D 0 D*0

Eric Braaten ar. Xiv: 0907. 3167 ≥ 6 fer mis !!

X(3872)-J/ relative sizes drms(X 3872) ≈ 6 fm drms(J/ ) ≈ 0. 4 fm Vol(J/ ) Vol(X 3872) Size similar to 11 Li & 19 C “halo” nuclei studied by Prof. Satoh ≈ 10 -3 _ • Overlap of the cc necessary to form the J/ in X p+p-J/ decays is rare _ • Probability forming such a fragile object in H. E. pp collisions is small -- ar. Xiv 0906. 0882: s. CDF(meas)>3. 1± 0. 7 nb vs stheory(molecule)<0. 11 nb

_ Produced like the ’ in pp collisions • Fraction from B decays – Long-lived fraction y(2 S) : (drms ≈ 0. 4 fm) 28. 3 1. 0(stat. ) 0. 7(syst. ) % X(3872) : (drms ≈ 6 fm? ? ) 16. 1 4. 9(stat. ) 1. 0(syst. ) % X(3872) behaves similarly to y(2 S). X(3872) mostly prompt.

X(3872)=diquark-diantiquark ? Expect SU(3) multiplets Isospin partners X-= d S=-1 partners Xs-= s doublet of “X(3872)” states DM=8± 3 Me. V Maiani et al PRD 71, 014028

No multiplet partners seen Ba. Bar search for “X-(3872)” p-p 0 J/ PRD 71, 031501 B 0 B- X(3872)– M(J/ π–π0) Bf(B 0 K+X-)Bf(X- p-p 0 J/y) Bf(B- K+X 0)Bf(X- p-p-J/y) X(3872)– M(J/ π–π0) < 0. 4 (expect 2)

Many (>10) other states poorly consistent with quark model observed last 6 years by B-factories

What are hadrons made of? • 40 years after Gell-Mann’s quarks, we still don’t know 2 B ES 3/B e lle DA PA N FA IR/ Possibilities Som en re ew to a b s e le trut n lex o arn h dr omp a ed c H o to – expected non-qq mesons &/or non-qqq baryons not seen – non-qq meson candidates that are seen defy any comprehensive theoretical understanding.

Z(4430) and Z 1(4050) & Z 2(4250) Smoking guns for charmed exotics: u c d c

B K p ’ (in Belle) M 2(p+ ’) ? ? K*(1430) K+p-? K*(890) K+p- M 2(K+p-)

The Z(4430)± p± ’ peak B K p+ ’ evts near M(p ’) 4430 Me. V M 2(p± ’) Ge. V 2 Z(4430) M(p± ’) Ge. V M (Kp’) Ge. V M 2(Kp’) Ge. V 2 “K* Veto”

Could the Z(4430) be due to a reflection from the Kp channel?

Cos qp vs M 2(p ’) qp p ’ K +1. 0 22 Ge. V 2 (4. 43)2 Ge. V 2 0. 25 cosqp M 2(p ’) 16 Ge. V 2 M (p ’) & cosqp are tightly correlated; a peak in cosqp peak in M(p ’) -1. 0

S- P- & D-waves cannot make a peak (+ nothing else) at cosqp≈0. 25 not without introducing other, even more dramatic features at other cosqp (i. e. , other Mp ’) values.

But…

Ba. Bar doesn’t see a significant Z(4430)+ “For the fit … equivalent to the Belle analysis…we obtain mass & width values that are consistent with theirs, … but only ~1. 9 s from zero; fixing mass and width increases this to only ~3. 1 s. ” Belle PRL: (4. 1± 1. 0± 1. 4)x 10 -5

Reanalysis of Belle’s B Kp ’ data using Dalitz Plot techniques

2 -body isobar model for Kp ’ Our default model B K* ’ k ’ K 2* ’ K*(890) ’ KZ+ Kpy’ K*(1410) ’ K 0*(1430) ’ K 2*(1430) ’ K*(1680) ’ KZ+

Results with no + KZ term 2 1 12 3 4 5 C B 3 A 4 A B 5 fit CL=0. 1% C 51

Results with a KZ+ term 1 3 2 4 1 2 3 4 5 A C B C A 5 fit CL=36% B

Compare with PRL results K* veto applied With Z(4430) Signif: 6. 4 s Published results Without Z(4430) Mass & significance similar, width & errors are larger Ba. Bar: Belle: No big contradiction -5 = (3. 2+1. 8+9. 6 0. 9 -1. 6 )x 10

Variations on a theme Z(4430)+ significance Others: Blatt f-f term 0 r=1. 6 fm 4 fm; Z+ spin J=0 J=1; incl K* in the bkg fcn

The Z 1(4050)+ & Z 2(4250)+ p+cc 1 peaks R. Mizuk et al (Belle), PRD 78, 072004 (2008)

Dalitz analysis of B 0 K-p+cc 1 DE Ge. V ? ? ? K 3*(1780) K*(1680) K*(1400)’s M (J/ g) Ge. V K*(890) G

B Kpcc 1 Dalitz-plot analyses Default Model B K*cc 1 kcc 1 K 2*cc 1 K*(890)cc 1 KZ+ Kpcc 1 K*(1410)cc 1 K 0*(1430)cc 1 K 2*(1430)cc 1 K*(1680)cc 1 K 3*(1780)cc 1 KZ+

Fit model: all low-lying K*’s (no Z+ state) a b c d g f e a b e c d g f C. L. =3 10 -10

Fit model: all K*’s + one Z+ state a b c d g f e a b e c d g f C. L. =0. 1%

Are there two? ? ? ? a b c d ?

Fit model: all K*’s + two Z+ states a b c d g f e a b e c d g f C. L. =42%

Two Z-states give best fit Projection with K* veto

XYZ Summary

What are hadrons made of? • 40 years after Gell-Mann’s prize, we still don’t know 2 B ES 3/B e lle DA PA N FA IR/ Possibilities Som en re ew to a b s e le trut n lex o arn h dr omp a ed c H o to – expected non-qq mesons &/or non-qqq baryons not seen – non-qq meson candidates that are seen defy any comprehensive theoretical understanding.

Quantum Chromodynamics QED: scalar charge e a. QED single photon QED gauge transform +ie. A 1 vector field (photon) QCD triplet charge: ej as Non-Abelian extension of QED ei er eb eg gij eight “gluons” QCD gauge transform + i a l i Gi eight 3 x 3 SU(3) matrices 8 vector fields (gluons)

Vacuum polarization QED vs QCD QED 2 nf 11 CA in QCD: CA=3, & this dominates as increases with distance QCD

QED: photons have no charge coupling decreases at large distances QCD: gluons carry color charges gluons interact with each other coupling increases at large distances a Coupling strengths distance

Test QCD with 3 -jet events (& deep inelastic scattering) as gluon rate for 3 -jet events should decrease with Ecm

“running” as Large distance short distance

The QCD particle spectrum hasn’t been computed Quark-binding into hadrons occurs here (Q≈mp≈140 Me. V) as (mp) ~ 0. 5 perturbation theory can’t be used Theorists make “QCD-motivated” models that must be tested by experiment

excited baryon octets? proton all S -wav es JP=1/2+ all nr=0 JP=1/2+ JP=1/2 - e e on P- v wa all nr=0 e on all S-wave =1 nr 1/2 - 1/2 + N*(1535) N*(1440) L(1405) ? ? ? L(1620) S(1580) S(1660) (? ) ? ? ?

1 st sign? Scalar meson nonet JP=0+ ~800 980 ao- k 0 k+ 980 f 0 ~600 nr=0 ~800 p- k - ao 0 980 ~800 ao+ 980 s _ k 0 ~800 w av e (a+o, a 0 o, ao-) = heaviest! Ma 0 =980 Me. V ; 2 m. K =990 Me. V does the a 0 meson have the same quark content as KK, i. e. usus? _

diquark diantiquark nonet? JP=0+ __ du ds __ sd _ 3 us diquark antitriplet ~800 su 3 = 980 a- k 0 k+ 980 o ~600 __ du diantiquark-triplet _ 3 3 = 8 1 f 0 ~800 k - a 0 980 o ~800 a+ o s _ k 0 ~800 980

_ _ _ Is the f 0(980) a (uu+dd)ss state? KK threshold BES sees an abrupt switch from f 0(980) pp to f 0(980) KK at threshold

The LEPS observation of Q+(1530)? Carbon target + K - K “n” g n M(K+“n”) g + “n” K- K+ “n” Physical Review Letters, 91, 012002 (2003) (“n” = neutron inside Carbon nucleus)

LEPS follow-up Expt L (1520)= control Q+ ? (with a deuterium target) undetected

Inferring the neutron’s 4 -mom They know the 4 -mom. of the n p system q e np ram f t s re But they don’t know q They chose q to be the angle that minimizes the spectator’s cm momentum

Shows up in all data subsamples

Lots of interest in the X(3872) line shape C. Hanhart et al ar. Xiv: 1002. 4097 also E. Braaten et al PRD 81 014019 Line shape and very precise mass measurement only possible at FAIR