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Photoproduction of Exotic Hadrons Exotic Mesons Photoproduction + Photoproduction of LHCB Pentaquarks

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Photoproduction of Exotic Hadrons Exotic Mesons Photoproduction + Photoproduction of LHCB Pentaquarks Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions Photoproduction of exotic hadrons Exotic mesons photoproduction + photoproduction of LHCB pentaquarks Andrea Celentano INFN-Genova Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions Introduction 1 Introduction 2 The MesonEx experiment 3 The GlueX experiment 4 Hidden-charm pentaquark search 5 Conclusions 2 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions Exotic mesons QCD does not prohibit the existence of unconventional meson states such as hybrids (qqg), tetraquarks (qqqq), and glueballs. Exotic quantum numbers: J PC 6= qq The discovery of states with manifest gluonic component, behind the CQM, would be the opportunity to directly “look” inside hadron dynamics. Exotic quantum numbers would provide an unambiguous evidence of these states. Lattice QCD calculations1provided a first hint on the spectrum and mass range of exotics. Mass range: 1.4 GeV - 3.0 GeV CQM mesons Exotics Lightest exotic is a 1-+ state. Negative parity Positive parity 1 J. J. Dudek et al, Phys. Rev. D82, 034508 (2010) 3 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions Exotic mesons photoproduction Traditionally, meson spectroscopy was studied trough different experimental techinques: peripheral hadron production, NN annihiliation, ... Photo-production measurements were limited by the lack of high-intensity, high-energy, high-quality photon beams. Today, this limitation is no longer present. Advantages: • Photon spin: exotic quantum numbers are more likely produced by S = 1 probe • Linear polarization: acts like a filter to disentangle the production mechanisms and suppress backgrounds • Production rate: for exotics is expected to be comparable as for regular meson 4 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions Results from past experiments See P. Eugenio talk on Thursday! 5 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions Jefferson Laboratory Jefferson Laboratory (Newport News, VA, USA): home of the Continuous Electron Beam Accelerator Facility (CEBAF) 12-GeV e− machine based on superconducting technology. • 4 experimental Halls: A, B, C, D • Multi-pass acceleration scheme, 2.2 GeV / pass • Max. current: ' 100µA / Hall (A and C) • CW beam, ' 100% duty-cycle • Beam polarization ' 80% 6 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions MesonEx (E12-12-005) in Hall-B at Jefferson Laboratory Meson Spectroscopy program with quasi-real photons: low Q2 electron scattering on a hydrogen target. Goals: • Measure the light-quarks mesons spectrum in the mass range 1.0 - 3.0 GeV • Determine masses and properties of rare qq states • Search for exotic mesons Q2 vs ν Low Q2 electron scattering: • Provides a high-flux of high-energy, linearly polarized, quasi-real photons. • Complementary and competitive to real photo-production • Virtual photon kinematics and polarization determined event-by-event measuring εT vs ν scattered electron variables Experimental technique: coincidence measurement between CLAS12 (final state hadrons) and Forward Tagger facility (low-angle scattered electron) 7 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions CLAS12 / Forward tagger detectors CLAS12: multi-purpouse, large acceptande, detector optimized for multi-particles final states (charged/neutrals) • Nominal luminosity: L = 1035cm−2s−1 • Charged particles tracking: toroidal magnet + drift chambers system • Particle ID: TOF, Cerenkov, RICH • Neutral particles: lead/plastic scintillator calorimeter Forward tagger: forward spectrometer optimized for detection of e− scattered at low angle. • Lead-tungstate calorimeter (FT-Cal): measure scattered electrons energy (σE ' %) • Hodoscope (FT-Hodo): distinguish photons from electrons. • Tracker (FT-Trck): determine the electron scattering plane. ◦ ◦ Nominal acceptance: 2.5 < θe < 4.5 , 0.5 < Ee(GeV ) < 4.5 8 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions MesonEx: expected results. Benchmark reaction: γp → nπ+π+π− MC study Isobar model for 3-pions production, Black: generated, Red: t=-0.5 GeV2, Blue: t=-0.2 GeV2 σ ' 10 µbarn a2 to πρ D Wave a1 to πρ S Wave a1 to πρ D Wave T ot 40000 70000 2000 1800 35000 60000 1600 30000 50000 1400 25000 1200 40000 20000 1000 30000 15000 800 20000 600 10000 400 5000 10000 200 0 0 0 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0.8 1 1.2 1.4 1.6 1.8 2 2.2 State JPC L Decay Mode 3π Invariant Mass [GeV/c2] 3π Invariant Mass [GeV/c2] 3π Invariant Mass [GeV/c2] a (1260) 1++ D ρπ π2 to πρ P Wave π2 to πρ F Wave π2 to f2π S Wave 1 25000 3000 20000 ++ a2 (1320) 2 D ρπ 18000 −+ 2500 π2 (1670) 2 P ρπ 20000 16000 14000 −+ 2000 π2 (1670) 2 F ρπ 15000 12000 −+ π2 (1670) 2 S f2π 1500 10000 −+ 10000 8000 π2 (1670) 2 D f2π 1000 −+ 6000 π1 (1600) 1 P ρπ 5000 4000 500 2000 0 0 0 • 3π channel PWA 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0.8 1 1.2 1.4 1.6 1.8 2 2.2 3π Invariant Mass [GeV/c2] 3π Invariant Mass [GeV/c2] 3π Invariant Mass [GeV/c2] feasible in MesonEx π2 to f2π D Wave π1 to πρ P Wave π1 exotic 3π All Waves 800 3000 80000 700 70000 • Sensitivity to 2500 600 60000 2000 π1(1600): 500 50000 σ ≥ 0.01σT ot 400 1500 40000 300 30000 1000 200 20000 • Leakage 500 100 10000 contribution to 0 0 0 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0.8 1 1.2 1.4 1.6 1.8 2 2.2 0.8 1 1.2 1.4 1.6 1.8 2 2.2 exotic waves from 3π Invariant Mass [GeV/c2] 3π Invariant Mass [GeV/c2] 3π Invariant Mass [GeV/c2] others: < 1% 9 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions MesonEx: expected results. Benchmark reaction γp → pπ0η MC study Ad-hoc model for reaction cross-section, Generated Events ×103 2 σtot ' 1µbarn: 900 a2 • Known resonances: a0(980), a2(1320), 800 a0 a2(1700) 700 • Exotic contribution: π1(1400) 600 Events per 25 MeV/c 500 • Large-Mπ0η: double-Regge exchange 400 Results: 300 • 200 Average acceptance: 3%, 180 k events/day a2(1320) • Non-exotic contributions properly 100 0 reconstructed from PWA procedure 1 1.5 2 2.5 3 2 Mπ0 η (GeV/c ) • Sensitivity to π1(1400) signal down to 5% of dominant a2(1320) signal 10 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions MesonEx: expected results. Benchmark reaction γp → pπ0η MC study Ad-hoc model for reaction cross-section, 3 Reconstructed Events ×10 2 σtot ' 1µbarn: 30 a2 • Known resonances: a0(980), a2(1320), 25 a0 a2(1700) • Exotic contribution: π1(1400) 20 Events per 25 MeV/c • Large-Mπ0η: double-Regge exchange 15 Results: 10 • Average acceptance: 3%, 180 k events/day a (1320) 5 2 • Non-exotic contributions properly 0 reconstructed from PWA procedure 1 1.5 2 2.5 3 3.5 2 Mπ0 η (GeV/c ) • Sensitivity to π1(1400) signal down to 5% of dominant a2(1320) signal 11 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions The GlueX experiment in Hall-D at Jefferson Laboratory Photo-production experiment (real photons) on a fixed LH2 target GlueX detector: • Hermetic detector optimized for multi-particle final state measurement • Charged particle tracking: 2.2 T solenoidal field + drift chambers (central/forward) • Calorimetry: FCAL (lead glass) / central (lead + fibers) • Particle ID: Time of flight, Start counter (future upgrade: DIRC detector) Hall-D photon beam: coherent Bremmstrahlung on diamond target • 12 GeV e− beam, 0.05 - 2.2 µA • Coherent peak 8.4 - 9 GeV, P' 40% • Tagger spectrometer (Elbek-type) σE /E ' 0.1% • Pair spectrometer: σP /P' 5% 12 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions GlueX recent results2 GlueX 2016 spring run: 12 GeV beam - 60 days GlueX engineering run. Data for early physics results. Promising preliminary results for exotic mesons spectroscopy: • ππ spectroscopy • Multi-photon final states (golden channel π0η: 4γs) 2 Plots from A. Austregelsilo talk at PWA8/Athos4 13 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions GlueX future perspectives GlueX physics runs: • GlueX-I: 2017-2018. Started in February, 10x more data than 2016 planned: data for physics analysis. • GlueX-II: 2019+. Upgraded detector (better PID), higher luminosity MC study of benchmark reaction γp → nπ+π+π− • PWA MC study performed with exotic state strenght: σπ1 = 1.6% · σ3π • Thanks to the high acceptance and good resolution of the GlueX detector a complete Partial Wave Analysis is feasible. • The contribution of small signals to the invariant mass spectrum can be clearly isolated and measured. 14 / 24 Introduction The MesonEx experiment The GlueX experiment Hidden-charm pentaquark search Conclusions LHCB hidden-charm pentaquark LHCb in 2015 announced3the discovery of two exotic structures in the J/ψ - p channel: Pc(4380) and Pc(4450), by measuring the 0 − decay Λb → pJ/ψK . They claimed that the minimum quark content is ccuud. Widths: • Pc(4450): Γ = 39 MeV • Pc(4380): Γ = 205 MeV Quantum numbers (PWA most probable solution) 5 − • Pc(4450): JP = 2 3 + • Pc(4380): Jp = 2 Altough: “Acceptable solutions are also found for additional cases with opposite parity” 3 Phys.
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