Meson Spectroscopy Methods, Measurements & Machines

Meson Spectroscopy Methods, Measurements & Machines Aug. 31 Sep. 4, Groningen Klaus Götzen GSI Darmstadt

Mesons are they really interesting? Look at the American Physical Society Highlights 2013! [http://physics.aps.org/articles/v6/139]... Three quarks for Muster Mark!? 2

Mesons are they really interesting? Look at the American Physical Society Highlights 2013! [http://physics.aps.org/articles/v6/139] Z c (3900) + Z c (3900)... Three quarks for Muster Mark!? Four 3

What is a meson? Definition: Meson Hadron with B = 0 in contrast to simple quark anti-quark (q ) allows a huge variety of states! q Meson 4

What is a meson? Definition: Meson Hadron with B = 0 in contrast to simple quark anti-quark (q ) allows a huge variety of states! q You can basically add whatever you want... Meson 5

What is a meson? Definition: Meson Hadron with B = 0 in contrast to simple quark anti-quark (q ) allows a huge variety of states! q You can basically add whatever you want...... as long as you add something with the opposite baryon number Meson 6

Meson Variations Commonly discussed: Conventional (q ) 1 Hybrid (q ) 8 g Molecule (q ) 1 (q ) 1 Tetraquark (q q ) 1 Hadro-quarkonium (Q ) 1 (q ) 1 Diquarkonium (qq) 3 ( ) 3 Glueball (gg) 1 or (ggg) 1 [e.g. Braaten, PRD90(2014)014044] 7

Identify Exotic Mesons 1 st order exotic Simple to spot: QN invalid for q states (e.g. Q, S, C >1...) 2 nd order exotic (spin exotic) Special for q states: some spin-parity values (J PC ) are forbidden J PC = 0, 0 +, 1 +, 2 +, 3 +,... exotic meson q L S 1 S 2 3 rd order exotic (crypto exotic) No (obvious) difference to q states hard to identify! Can mix with conventional states Carefully study the decays & properties! q q 8

φ[rad] Properties and Dynamics of Mesons I = T 2 Line shape Phase motion Decay angles J PC m 0 Main properties: Mass m, width, Spin-Parity J PC, decays B(M f i ) Complex dynamics, e.g., I = T 2 Interference of multiple resonances T i I = Σc i T i 2 (strength c i ) Typically: Amplitude Analysis (or Partial Wave Analysis) needed to disentangle signals and determine resonance properties 9

φ[rad] Properties and Dynamics of Mesons I = T 2 Line shape m 0 Intensity Phase motion resonance 1 resonance 2 constructive destructive Decay angles J PC Main properties: Mass m, width, Spin-Parity J PC, decays B(M f i ) 2π Complex dynamics, e.g., I = T 2 Relative phase (c 2 T 2 c 1 T 1 ) Interference of multiple π resonances T i I = Σc i T i 2 (strength c i ) π Typically: Amplitude Analysis (or Partial Wave Analysis) needed to disentangle signals and determine resonance properties 10

Light Quark Sector

Light Meson Spectrum Many states found (u,d,s quarks) 12

Light Meson Spectrum Many states found Predictions not perfect (u,d,s quarks) 13

Light Meson Spectrum Many states found Predictions not perfect Broad states Strong overlap + mixing (u,d,s quarks) 14

Light Meson Spectrum - Multiplets Many states found Predictions not perfect Broad states Strong overlap + mixing Apply ordering to identify supernumerary states J PC Multiplets (Nonets) S 1 0-1 -1 0 1 I 3 m [GeV] π(1800) K(1830) η(1760) π(1300) K(1460) η(1295) η(1405) 0 + π(140) K(495) η(548) η'(958) 0 + n = 3 0 + 1 n = 2 n = 1 ρ(1450) K*(1410) ω(1420) φ(1680) 1 ρ(770) K*(892) ω(782) φ(1020) 1 0 ++ 1 + a 2 (1320) K 2 *(1430) f 2 (1270) f 2 '(1525) a 0 (1450) K 0 *(1430) f 0 (1370) f 0 (1710) 0 ++ n = 2 2 ++ a 2 (1700) a 1 (1640) K 2 *(1980) f 2 (2010) f 2 (1950) n = 1 1 ++ 1 ++ 2 ++ a 1 (1260) K 1a f 1 (1285) f 1 (1420) b 1 (1235) K 1b h 1 (1170) h 1 (1380) 1 + 3 ρ 3 (1690) K 3 *(1780) ω 3 (1670) φ 3 (1850) π 2 (1670) K 2 (1770) η 2 (1645) η 2 (1870) 2 + n = 1 0 1 2 n L 2 K 2 (1820) ρ(1700) K*(1680) ω(1650) 1 [Amsler, 2007] L 15

Light Meson Spectrum - Multiplets Many states found Predictions not perfect Broad states Strong overlap + mixing Apply ordering to identify supernumerary states J PC Multiplets (Nonets) S 1 0-1 -1 0 Avoid mixing with q by looking for spin-exotic states 1 I 3 m [GeV] π(1800) K(1830) η(1760) 0 + 1 π(1300) K(1460) η(1295) η(1405) 0 + π(140) K(495) η(548) η'(958) 0 + n = 3 n = 2 n = 1 ρ(1450) K*(1410) ω(1420) φ(1680) 1 ρ(770) K*(892) ω(782) φ(1020) 1 0 ++ 1 + a 2 (1320) K 2 *(1430) f 2 (1270) f 2 '(1525) a 0 (1450) K 0 *(1430) f 0 (1370) f 0 (1710) 0 ++ n = 2 2 ++ a 2 (1700) a 1 (1640) K 2 *(1980) f 2 (2010) f 2 (1950) n = 1 1 ++ 1 ++ 2 ++ a 1 (1260) K 1a f 1 (1285) f 1 (1420) b 1 (1235) K 1b h 1 (1170) h 1 (1380) 1 + 3 ρ 3 (1690) K 3 *(1780) ω 3 (1670) φ 3 (1850) π 2 (1670) K 2 (1770) η 2 (1645) η 2 (1870) 2 + n = 1 0 1 2 n 1 + L 2 K 2 (1820) ρ(1700) K*(1680) ω(1650) π 1 (1400) π 1 (1600)? 1 [Amsler, 2007] L 16

Dalitz Plot Analysis π 1 (1400) (Crystal Barrel) Analyse 3-body reaction: n π π 0 η @ rest [PL B423 (1998) 175] Dalitz Plot Dalitz Plot Analysis 2D intensity study in 3 body reactions 2 variables describe complete dynamics reveals 2-body resonances in the system Find set of resonances T i and coefficients c i, so that I = Σc i T i 2 describes data Flat χ 2 distributions Fit demands X ηπ (both 0 + ) with L=1 (m X = 1400±30 MeV, X = 310±70 MeV) J PC (X) = 1 +, X called π 1 (1400) 17

Dalitz Plot Analysis π 1 (1400) (Crystal Barrel) Analyse 3-body reaction: n π π 0 η @ rest [PL B423 (1998) 175] Dalitz Plot Dalitz Plot Analysis 2D intensity study in 3 body reactions 2 variables describe complete dynamics reveals 2-body resonances in the system Find set of resonances T i and coefficients c i, so that I = Σc i T i 2 describes data Bad fit without π 1 (1400) Fit demands X ηπ (both 0 + ) with L=1 (m X = 1400±30 MeV, X = 310±70 MeV) J PC (X) = 1 +, X called π 1 (1400) 18

Partial Wave Analysis π 1 (1600) (COMPASS) Observation of hybrid candidate @ COMPASS: π 1 (1600) Diffractive dissociation π π π π + with π beam (p=190 GeV/c) on Pb Partial Wave Analysis (PWA) - 2 stages 1. Mass independent fit in m 3π slices Contributions & interferences of different X (π + π ) ib π 2. Fit with model assumptions for the observed partial waves (resonances) [PRL 104 (2010) 241803] 19

COMPASS PWA Fit 1. Mass independent fit 5 observables τ (m isobar + 4 angles) Offer 42 partial waves to the fit Fit production amplitudes to describe distributions of τ [PRL 104 (2010) 241803] Intensities of partial waves (PW) Relative phases between PW 2. Mass dependent fit Select significant partial waves Fit model amplitudes to these PW to extract parameters of resonances 1 ++ 2 ++ 22

Fit Result Significant intensity in 1 + wave Physical motion of relative phase to other resonances 10 47 Exotic resonance π 1 (1600) (m X = 1660 ± MeV, X = 269 ± MeV) π 1 (1600) 1 + Δφ(1 +, 1 ++ ) 64 67 [PRL 104 (2010) 241803] 1 ++ a 1 (1260) mass independent fit mass dependent fit resonances non-resonant terms Δφ(1 +, 2 + ) 2 + π 2 (1670) 23

Heavy Quarks - Charmonium

Charmonium Advantages: Lower level density Longer lifetime (small width) Charmonium predictions fitted well until 2003 (c ) 25

Charmonium Advantages: Lower level density Longer lifetime (small width) Charmonium predictions fitted well until 2003 (c ) Since 2003: 20 new charmonium-like states not fitting well the predictions Five (almost) 1 st order exotics Z(3900) +... Z(4430) + Some very close to DD-like thresholds X(3872), Z(3900), Z(4020),... 26

The charged Z +' s Z +' s all decay to c π + Charged and too heavy for excited light meson Minimum quark content c u (first time proof of exotic matter!!) Z(3900) + Z(4020) + Z(4050) + Z(4250) + Z(4430) + [PRL 110 (2013) 252001] [PRL 111 (2013) 242001] [PR D78 (2008) 072004] [PRL 100 (2008) 142001] Name [MeV] c decay open charm closeby DD Δm to DD [MeV] Z(3900) + 35 ± 7 J/ψ π + (D * ) + D 0 *+ 9.3 ± 3.4 Z(4020) + 10 ± 6 h c π + (D * * ) + D *0 *+ 6.7 ± 2.4 Z(4050) + 82 ± 40 χ c (1P) π +? D 0 *+ 34 ± 2.4 Z(4250) + 177 ± 100 χ c (1P) π +? D 0 *+ -38 ± 50 Z(4430) + 200 ± 50 ψ(2s) π +? D *+ 1 12 ± 40 27

Nature of the Z's Some of the possibilities ruled out, but many still possible Conventional (q ) 1 Hybrid (q ) 8 g Molecule (q ) 1 (q ) 1 Tetraquark (q q ) 1 Hadro-quarkonium (Q ) 1 (q ) 1 Diquarkonium (qq) 3 ( ) 3 Glueball (gg) 1 or (ggg) 1 28

The mysterious X(3872) Seen by 7 experiments in 6 channels (J/ψρ, J/ψω, J/ψγ, ψ'γ, D π 0, D* ) J PC = 1 ++ natural candidate for χ c1 (2P) Oddities 50-100 MeV to light for χ c1 (2P) Extremly narrow: < 1.2 MeV Extremly close to D 0 0 * threshold: m X - m D * = 0.11 ± 0.21 MeV Molecule?! If molecule d 10 fm How to re-arrange quarks to form c ρ? Why is this loosely bound state produced so abundantly @ CDF in TeV reactions? u [arxiv:0906.5218] CDF m(j/ψππ) [GeV/c 2 ] [arxiv:hep-ex/0606055] Belle 29 c

Theory about X(3872) To clarify nature: line shape + width measurements essential D 0 0 * D π 0 bound virtual [Hanhart, PRD76 (2007) 034007] [Braaten, PRD77 (2008) 014029] Need p scan experiment to get access to the line shape 30

Measure Multiplets to solve XYZ Puzzle Different structure assumptions (models) Different multiplet patterns Diquarkonium Molecule Hadro-charmonium cu cd cs + D + D *+ D 0 D 2 D 1 D + s... + D - D *- 0 2 1 D - s... J/ψ h c η c... χ c ψ' π 0 K + 0 ρ φ K + π- f 0... a 0 [Drenska, Riv. Nuovo Cim. 033 (2010) 633] cs cs / cd cs / cu 1 + X(3872)? Z(3900)? Z(3900) 0? Z(3900) +? cd cu / cd cu Z(4020)? X(3872), Z(3900)? h c 0 + ψ' 0 ++ χ c1 0 + χ c2 0 + η c ' 0 ++ χ c0 0 + [Cleven et al., arxiv:1505.01771] 31

'Machines' Present & Future Experiments

Meson Production (1) Hadron/gamma beam on fixed target [GlueX: γ p (9 GeV/c), COMPASS: π/k/p p/nucl. (160-270 GeV/c)] h/γ X running Q 2 Target recoil started Light sector only Direct access to exotic QN Always a recoil present (complicates analysis) 33

Meson Production (2) B-meson decays X running B 0/+ recoil future Light & charmonium sector Exclusive systems for Dalitz plot analysis Suppression of higher spins J 34

Meson Production (3) Formation/production in e + e [BESIII: E 4.6 GeV, Belle2: E 11 GeV] e + (ISR) γ* X running e - Formation or Production (w/ recoil) (recoil) future Light, charmonium & bottomonium sector High mass resolution by beam energy precision (Formation) J PC limited to 1 (Formation) Suppression of higher spins J 35

Meson Production (4) Formation/production in p [PANDA: E 5.5 GeV] X FermiLab E835 past p Formation or Production (w/ recoil) (recoil) future Light & charmonium sector High mass resolution with all ( q) J PC possible Currently no running experiment 36

Summary and Prospects Meson spectroscopy Tool to understand and quantify QCD binding Many new exotic states discovered in last decade Proof validity of fundamental QCD principle Great opportunity to refine and adapt models Many running and new experiments in planning Understand conventional states binding Complete the exotic multiplets Still some way to go...... stay tuned for more interesting discoveries! 37