Experimental motivations for studying few-hadron systems on the - PowerPoint PPT Presentation

Experimental motivations for studying few-hadron systems on the lattice Alessandro Pilloni Scattering Amplitudes and Resonances properties from Latticd QCD MITP, Mainz, August 27 th , 2018

Outline • Introduction • The light sector: the 3𝜌 system • 𝜃 ′ , 𝜕 and 𝜚 • The 𝑏 1 (1260) • The hybrid 𝜌 1 • The 𝑏 1 (1420) • The heavy sector: XYZ • The 𝑌(3872) and the 𝑍 states • Two-body subchannels: 𝑎 𝑑 s and 𝑎 𝑐 s • Complicated Dalitz plots 2 A. Pilloni – Experimental motivation for multihadrons on the lattice

Hadron Spectroscopy Hybrids Tetraquark Meson Baryon Glueball 𝝆 𝑲/𝝎 𝝆 Hadroquarkonium 𝝆 Molecule Experiment Amplitude Properties, Data analysis Model building Lattice QCD Interpretations on the spectrum leads to understanding fundamental laws of nature 3

Experiment vs. Lattice QCD • Higher and higher statistics  • Lots of multiparticles Experiment decay channels available  • Scattering information entangled to production mechanisms  • Experiments happen at the physical point only  • Orthogonal systematics  • Scattering information separated from Lattice QCD production; unaccessible channels  • Although QCD is rigid, one can vary the input parameters (quark masses, 𝑂 𝑑 and 𝑜 𝑔 ) and study the effect on amplitudes  4

Experiment vs. Lattice QCD 𝜌 𝜐 𝜍 Experiment 𝜌 𝑏 1 (1260) 𝜌 𝜉 Intermediate step through a 2-body isobar (partial wave truncation) 𝜌 𝜌 Lattice QCD 𝜍 𝜍 𝜌 𝜌 𝑏 1 (1260) 𝜌 𝜌 5

Experiment vs. Lattice QCD 𝜌 𝜌 𝜍 Experiment 𝜌 𝑏 1 (1260) 𝜌 IP 𝑞 𝑞 Intermediate step through a 2-body isobar (partial wave truncation) 𝜌 𝜌 Lattice QCD 𝜍 𝜍 𝜌 𝜌 𝑏 1 (1260) 𝜌 𝜌 6

Light spectrum (1-particle correlators) HadSpec PRD88, 094505 𝜌 1 (1600) The higher the mass, the more channels open 𝑏 1 (1260) 𝑏 1 1420 ? 7 A. Pilloni – Experimental motivation for multihadrons on the lattice

3-body stuff Unitarity constraints on the Isobar-Spectator amplitude M. Mai, B. Hu, M. Doring, AP, A. Szczepaniak EPJA53, 9, 177 A. Jackura, et al. , to appear D. Sadasivan, et al. , in progress → See Michael’s talk on Friday 8 A. Jackura

The 𝑏 1 (1260) Despite it has been known since forever, the resonance parameters of the 𝑏 1 1260 are poorly determined The production (and model) dependence is affecting their extraction 9 A. Pilloni – Experimental motivation for multihadrons on the lattice

The 𝑏 1 (1260) The extraction of the resonance in the 𝜐 decay should be the cleanest, but the determination of the pole is still unstable (Lattice simulations with stable 𝜍 , Lang, Leskovec, Mohler, Prelovsek, JHEP 1404, 162) 10 A. Pilloni – Experimental motivation for multihadrons on the lattice

The 𝑏 1 (1260) M. Mikhasenko, A. Jackura, AP, et al. , to appear We can use these models to fit 𝜐 − → 2𝜌 − 𝜌 + 𝜉 and describe the 𝑏 1 (1260) The dispersed improved model describes better the data at threshold 11 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝜌𝑞 → 3𝜌 𝑞 diffractive production COMPASS, PRD95, 032004 (2017) Slide by B. Ketzer 12 A. Pilloni – Experimental motivation for multihadrons on the lattice

Deck amplitude 𝑆 𝜌𝜌 IP This production mechanism allows for a nonresonant contribution (Deck effect) Because of the light mass of the pion, the singularity is close to the physical region and generates a peaking background 13 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝜌 1 1600 → 𝜍𝜌 → 𝜌𝜌𝜌 The strength of the Deck effect depends on the momentum transferred 𝑢 , but the precise estimates rely on the model for the Deck amplitude (Deck) (Deck) 14 A. Pilloni – Experimental motivation for multihadrons on the lattice

Coupled channel 𝜌 1 1600 → 𝜃 (′) 𝜌 PLB740, 303-311 A strong signal is also observed in 𝜃 (′) 𝜌 , consistent with the naive expectation for a hybrid meson Having the 3𝜌 → 3𝜌 scattering data from Lattice will allow for a coupled channel analysis unaffected by the Deck effect 15 A. Pilloni – Experimental motivation for multihadrons on the lattice

Coupled channel 𝜌 1 1600 → 𝜃 (′) 𝜌 Coupled channel analysis of 𝜃𝜌 and 𝜃 ′ 𝜌 almost completed • A. Rodas, AP et al. (JPAC), to appear 𝜌 1 1400 ? 𝑏 2 (1320) ′ (1700) 𝑏 2 𝜌 1 1600 ? 16 A. Pilloni – Experimental motivation for multihadrons on the lattice

Coupled channel 𝜌 1 1600 → 𝜃 (′) 𝜌 Production amplitude 𝑢(𝑡) = 𝑂 𝑡 𝐸(𝑡) 𝑜(𝑡) 𝐸(𝑡) The 𝐸(𝑡) has only right hand cuts; it contains all the Final State Interactions Scattering amplitude constrained by unitarity → universal 𝐸(𝑡) 𝑂(𝑡) 17 A. Pilloni – Experimental motivation for multihadrons on the lattice

Coupled channel 𝜌 1 1600 → 𝜃 (′) 𝜌 Production amplitude 𝑢(𝑡) = 𝑂 𝑡 𝐸(𝑡) 𝑜(𝑡) 𝐸(𝑡) The 𝑜 𝑡 , 𝑂(𝑡) have left hand cuts only, process-dependent, smooth Scattering amplitude Having access to scattering directly can help reducing systematics 𝐸(𝑡) 𝑂(𝑡) 18 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝑏 1 1420 → 𝑔 0 980 𝜌 → 𝜌𝜌𝜌 COMPASS claimed the observation of another 𝑏 1 at a slightly higher mass • Narrower than the 𝑏 1 (1260) • Unexpected in quark model or lattice spectra • Only seen in 𝑔 0 980 𝜌 19 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝑏 1 1420 → 𝑔 0 980 𝜌 → 𝜌𝜌𝜌 It has been proposed that the peak is due to a triangle singularity i.e. a dynamical enhancement generated by rescattering Mikhasenko, Ketzer, Sarantsev, PRD91, 094015 Breit-Wigner Triangle If that is the case, the strength of the signal would dramatically depend on the mass of the exchanges: studying the amplitude at different pion/kaon masses will confirm whether this is true 20 A. Pilloni – Experimental motivation for multihadrons on the lattice

The heavy sector: XYZ states Esposito, AP, Polosa, Phys.Rept. 668 A host of unexpected resonances have appeared decaying mostly into charmonium + light Hardly reconciled with usual charmonium interpretation 21 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝑌(3872) • Discovered in 𝐶 → 𝐿 𝑌 → 𝐿 𝐾/𝜔 𝜌𝜌 • Quantum numbers 1 ++ • Very close to 𝐸𝐸 ∗ threshold • Too narrow for an above- treshold charmonium • Isospin violation too big Γ 𝑌→𝐾/𝜔 𝜕 Γ 𝑌→𝐾/𝜔 𝜍 ~0.8 ± 0.3 • Mass prediction not compatible with 𝜓 𝑑1 (2𝑄) 𝑁 = 3871.68 ± 0.17 MeV 𝑁 𝑌 − 𝑁 𝐸𝐸 ∗ = −3 ± 192 keV Γ < 1.2 MeV @90% 22 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝑌(3872) Large prompt production at hadron colliders 𝜏 𝐶 /𝜏 𝑈𝑃𝑈 = 26.3 ± 2.3 ± 1.6 % 𝜏 𝑄𝑆 × 𝐶(𝑌 → 𝐾/𝜔𝜌𝜌) = 1.06 ± 0.11 ± 0.15 nb CMS, JHEP 1304, 154 23 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝑌(3872) on the lattice Prelovsek, Leskovec, PRL111, 192001 • Three body dynamics 𝐸 𝐸𝜌 may play a role. Playing with lighter charm mass? • A full amplitude analysis is missing, and is now mandatory 24 A. Pilloni – Experimental motivation for multihadrons on the lattice

Vector 𝑍 states Lots of unexpected 𝐾 𝑄𝐷 = 1 −− states found in ISR/direct production (and nowhere else!) Seen in few final states, mostly 𝐾/𝜔 𝜌𝜌 and 𝜔 2𝑇 𝜌𝜌 Not seen decaying into open charm pairs Large HQSS violation Belle J/𝜔𝜌𝜌 BES ℎ 𝑑 𝜌𝜌 25 A. Pilloni – Experimental motivation for multihadrons on the lattice

𝑍(4260) BESIII, PRL118, 092002 (2017) 𝑓 + 𝑓 − → 𝐾/𝜔 𝜌𝜌 𝑓 + 𝑓 − → ℎ 𝑑 𝜌𝜌 BESIII, PRL118, 092001 (2017) 𝑓 + 𝑓 − → 𝜌 + 𝐸 0 𝐸 ∗− New BESIII data show a peculiar lineshape BESIII, arXiv:1808.02847 for the 𝑍(4260) , and suggest a state narrower and lighter than in the past The state is mature for a coupled channel analysis (on the lattice?) 26 A. Pilloni – Experimental motivation for multihadrons on the lattice

′ (4020) Charged 𝑎 states: 𝑎 𝑑 3900 , 𝑎 𝑑 In the Dalitz plot projections, two states appear slightly above 𝐸 (∗) 𝐸 ∗ thresholds 𝑓 + 𝑓 − → 𝑎 𝑑 3900 + 𝜌 − → 𝐾/𝜔 𝜌 + 𝜌 − and → 𝐸𝐸 ∗ + 𝜌 − 𝑁 = 3888.7 ± 3.4 MeV, Γ = 35 ± 7 MeV 𝑓 + 𝑓 − → 𝑎 𝑑 ′ 4020 + 𝜌 − → ℎ 𝑑 𝜌 + 𝜌 − and → 𝐸 ∗0 𝐸 ∗+ 𝜌 − 𝑁 = 4023.9 ± 2.4 MeV, Γ = 10 ± 6 MeV 27 A. Pilloni – Experimental motivation for multihadrons on the lattice