Light-Meson Spectroscopy. at Jefferson Lab

Transcription

1 Light-Meson Spectroscopy at Jefferson Lab ( (GlueX and CLAS) ) Carlos W. Salgado Norfolk State University and The Thomas Jefferson National Accelerator Facility Carlos Salgado APS-Baltimore Meeting April,

2 Outline Jefferson Lab Meson Spectroscopy and QCD Status: Spectroscopy of (Exotic) Light-Mesons Photoproduction -Tools of Analysis - JPAC Past Jefferson Lab: CLAS6 Future Jefferson Lab: GlueX and CLAS12 Conclusions Carlos Salgado APS-Baltimore Meeting April,

3 GeV CEBAF Upgrade is designed to build on existing facility: vast majority of accelerator and experimental equipment have continued use. new Hall Upgrade magnets and power supplies CHL-2 Two GeV linacs Enhanced capabilities in existing Halls Maintain capability to deliver lower pass beam energies: 2.2, 4.4, 6.6. Carlos Salgado APS-Baltimore Meeting April, 2015

4 Jefferson Lab Newport News, VA Hall B Hall D Carlos Salgado APS-Baltimore Meeting April,

5 Carlos Salgado APS-Baltimore Meeting April,

6 Gluons and The Meson Spectrum At high energies the gluon is externally observed in three-jets events The gluons and the meson spectrum At lower (intermediate energies) the Understanding gluonic excitations of mesons hadron and the spectrum origin of confinement provides information about the gluons that bind quarks At high energy experimental evidence is (CONFINEMENT) found in jet production At lower energies the hadron spectrum carries information about the gluons that bind quarks The properties of confinement are them related to the gluon binding of hadrons Can we find hints of the glue in the meson glue spectrum? in the hadron spectrum? Search for non-standard states with explicit gluonic degrees of freedom Can we find a simple manifestation of the Exotic nonets regular meson tetraquarks glueball q q hybrid mesons Not-allowed J PC = 0 --, 0 +-, 1 -+, Unambiguous experimental signature for the presence of gluonic degrees of freedom in the spectrum of mesonic states L = (qq-angular momentum) hybrid Carlos Salgado APS-Baltimore Meeting April,

7 Lattice QCD - LQCD Numerical solutions of (almost) QCD-Lagrangian (Path Integrals) hypercubic space-time lattice quarks reside on sites, gluons reside on links between sites quarks Intensity of field gluons Hadron Spectrum Coll. Dudek, Edwards et al Jefferson Lab Effective Degrees of Freedom at intermediate energies Carlos Salgado APS-Baltimore Meeting April,

8 LQCD able to predict hybrids (exotics) exotics J PC normal Isovector mesons, m π ~700 hybrid Dudek PRD 83 (2011) Dudek PRD 84 (2011) Carlos Salgado APS-Baltimore Meeting April, 2015

9 Two of today s most relevant topics in Meson Spectroscopy: 1) Search for Exotic Mesons Search for non-standard - outside CQM (hybrid and exotic quantum numbers) states with explicit gluonic degrees of freedom q g q Understanding the relevant degrees of freedom to describe hadrons Predicted by several phenological models (flux tube, bag model,...) Validate LQCD predictions on hybrids 2) Study of Strangeonia Intermediate states between light and heavy mesons (a bridge to PQCD?). Of about 22 resonances expected below a mass of 2.5 GeV, only 7 are relatively well established. Strangeonia hybrids have been predicted just above a mass of 2 GeV. s s Carlos Salgado APS-Baltimore Meeting April,

10 Why photons? We see the photons in the Vector Dominance Model (VMD) " T Afanasev, Page! c.m. 100 Q 2, GeV Prediction of larger cross-sections a low-q 2 (Q 2 =0) Figure 1: Structure function σ T at W =3GeVwithstandardparameters. Q 2 is varied within its kinematically allowed range for E = 6GeV. Carlos Salgado APS-Baltimore Meeting April,

11 Status of Hybrid (Exotic) Search Carlos Salgado APS-Baltimore Meeting April,

12 Status of Hybrid (Exotic) Search Unlikely Hybrid Dynamical origin? Carlos Salgado APS-Baltimore Meeting April,

13 Status of Hybrid (Exotic) Search Unlikely Hybrid Dynamical origin? May be hybrid Challenge in 3π to separate exotic π 1 from π 2 Cleaner η π signal Carlos Salgado APS-Baltimore Meeting April,

14 Status of Hybrid (Exotic) Search Unlikely Hybrid Dynamical origin? May be hybrid Challenge in 3π to separate exotic π 1 from π 2 Cleaner η π signal Listed among further states Needs confirmation Carlos Salgado APS-Baltimore Meeting April,

15 E events/1997 π p π π π + p PRL 81, 5760 (1998) PRD 65, (2002) M = 1593 ± MeV Γ = 168 ± MeV Carlos Salgado APS-Baltimore Meeting April,

16 D98- > G-'; <D(.. % ( C % Before any strong conclusion: More systematic studies Mass-dependent fit &'()*+,-'./) (8'9) 4:;</=< >,-?-<@ A-<B.@<!"#!$#"!%" Carlos Salgado APS-Baltimore Meeting April,

17 ISOBAR MODEL 1) Helicity formalism 2) Isobar Model M, t Fitted parameters (production amplitudes) Minimize Extended Likelihood or where Normalization integral Carlos Salgado APS-Baltimore Meeting April,

18 What resonances are hidden under the mass distribution? Φ? Overlapping interfering wide small cross-sections non-resonant backgrounds... Carlos Salgado APS-Baltimore Meeting April,

19 Search Strategies at JLab Use GeV linearly polarized photons (12 GeV electron beam) Identify (naturality) production mechanisms Open phase space to separate meson/baryon production products Use hermetic detector with large acceptance Decay modes expected to have multiple particles Hermetic coverage for charged and neutral particles Medium resolution: momentum (~ 1-4%), energy (2-20%) High data acquisition rate to enable amplitude analysis Perform amplitude analysis Identify wide and rare (small cross sections) resonances Identify the J PC of resonances -phase motions -interference patterns Check consistency of results in different decay modes Event based (unbinned) acceptance corrections Carlos Salgado APS-Baltimore Meeting April,

20 Join Physics Analysis Center (JPAC) 1.1 Why JPAC? 12 GeV upgrade at JLab: CLAS, GlueX, etc. Jefferson Lab, Indiana U., GWU, Peking U. Aim:! Complete understanding of the hadron spectrum! discover new resonances e.g, gluonic excitations (states where glue builds their J PC ) Tools: Amplitude analyses of data To find new resonances not bump-hunting, but search for poles must build in S-Matrix constraints + state-of-the-art knowledge of reaction dynamics Hadron spectrum, exotics ChPT + Analyticity + Unitarity Dispersion Relations Regge Theory, Models Experimental Data CLAS, GlueX, JEF, COMPASS, BESS, LHCb, PANDA,! FFs, resonance parameters: M R,!, couplings Emilie Passemar 8 Carlos Salgado APS-Baltimore Meeting April,

21 Software Carlos Salgado APS-Baltimore Meeting April,

22 6 Carlos Salgado APS-Baltimore Meeting April,

23 Unpolarised GeV photon beam γp π + π + π (n) Clear evidence of non-exotic 2 ++ state a 2 (1320) No-evidence of exotic 1 -+ state π 1 (1600) at the expected yield σ π1 < 13.5 nb Carlos Salgado APS-Baltimore Meeting April,

24 CLAS6 - g12 run Search for new forms of hadronic matter in photoproduction Data taking completed in 2008 Photon Energy up to 5.5 GeV More than 26 billion triggers (2-prong + 3-prong) Total Luminosity: 68 pb -1 Data processing completed and physics analysis in progress Several exclusive channels are being analyzed γp π + π + π (n) γp (π 0 )π + π p γp K + K + (Ξ )(1530) γp pk + K - (ηφ) γp (pπ + π (η) γp π + K + K (n) γp e + e p... Meson Spectroscopy Search for exotic mesons Study of Strangeonia Baryon Spectroscopy Cascades Carlos Salgado APS-Baltimore Meeting April,

25 Search for π 1 (1600) C. Bookwalter thesis - FSU p t' e -3.9t' CLAS6-g12 Sharp t dependence consistent with!-exchange production Baryon background cuts: t' < 0.1 & " lab (! + ) < 25 o 4 Carlos Salgado APS-Baltimore Meeting April,

26 a 2 (1320) - Equal population of both reflectivity states - no observation in M=0 wave a 1 (1260)! 2 (1670) 7! Large signal in M=0 wave unpolarized beam! Photon beam is a coherent mixture of both parity eigenstates! Final states of different reflectivity do not interfere! exchange dominance! Equal production of M " = 1 + and 1 - (ambiguity)! No M " = 0 " " No J=0 meson production (spin zero filter) 5 eliminary 9 Carlos Salgado APS-Baltimore Meeting April,

27 No clear resonance signal High mass results fluctuate Accounts for at most 2% of total intensity preliminary 12! No evidence for exotic 1! No evidence for exotic 1 -+ phase motion -+ phase motion! Phase motion consistent with resonating 2! Phase motion consistent with resonating Carlos Salgado APS-Baltimore Meeting April,

28 Meson spectroscopy with photons at JLab-12 GeV Determination of JPC of meson states requires PWA Decay and production of exclusive reactions Good acceptance, energy resolution, particle identification Hall-D - GlueX Detector Good hermeticity Uniform acceptance Limited resolution Limited pid Hall-B - CLAS12 Detector Good resolution Good pid Reasonable hermeticity Un-uniform acceptance 8 12 Carlos Salgado M.Battaglieri - INFN GE Meson spectroscopy at JLab APS-Baltimore Meeting April,

29 GlueX Hermetic detection of charged and neutral particles in solenoid magnet Target (LH 2 ) Barrel Calorimeter (Bcal) Timeof-flight (tof) Pb-glass detector (Fcal) Initial Flux 10 7 γ/s 18,000 FADCs 4,000 pipeline TDCs 20 KHz L1 trigger 300 MB/s to tape Tagger Spectrometer (Upstream) Superconducting 2 T solenoid Tracking Cathode strips Drift chambers Straw tubes Carlos Salgado APS-Baltimore Meeting April, 2015

30 4 Diamond Radiator nominal tagging Top View δe/e = 0.1% Pol = 40% Coherent Bremsstrahlung photon beam Pair Spectrometer Counting House B 75 m 12 GeV e - Electron beam / dump Collimator Solenoid- Based detector Tagger Area Radiation e - Z γ e - Z Collimator Cave Selection θ<25µr polarized photons Experimental Hall D Target, Spectrometer Carlos Salgado APS-Baltimore Meeting April,

31 Carlos Salgado APS-Baltimore Meeting April,

32 GlueX GlueX will study the spectrum of mesons up to M ~ 2.8 GeV with a linearly polarized photon beam, a large acceptance (neutrals and charged final particles) spectrometer, and search for mesons with sensitivities of a few percent of the total cross section. GlueX status Civil construction of accelerator is completed. Hall D experimental equipment is mostly completed. Most GlueX systems are installed. Hall D is being commissioned ( ). First physics beam expected for Carlos Salgado APS-Baltimore Meeting April,

33 First look: ω and Ks Carlos Salgado APS-Baltimore Meeting April,

34 Hall B: CLAS12 Forward Detector: - TORUS magnet - Forward SVT tracker - HT Cherenkov Counter - Drift chamber system - LT Cherenkov Counter - Forward ToF System - Preshower calorimeter - E.M. calorimeter (EC) Central Detector: - SOLENOID magnet - Barrel Silicon Tracker - Central Time-of-Flight Proposed upgrades: - Micromegas (CD) - Neutron detector (CD) - RICH detector (FD) - Forward Tagger (FD) Carlos Salgado APS-Baltimore Meeting April,

35 Meson Spectroscopy with low Q2 electron scattering in CLAS12 M.Battaglieri, R.Devita, D.Glazier, C.Salgado, S.Stepanyan, D.Weygand Electro-production a very Low -Q 2 Experiments using unpolarized leptons are equivalent in the small Q 2 limit to those using partially linearly polarized photons {Dombey 69} Measured electron scattering at very low forward angles low-q 2 virtual photon real photon (well known technique from high energy experiments) detection of the scattered electron allows to determine the photon energy and linear polarization polarization is essential to isolate the exchange production mechanisms high luminosity allows the use of thin (gas)- targets Carlos Salgado APS-Baltimore Meeting April,

36 The Forward Tagger for CLAS12 Calorimeter Tracker HTCC Moller cup Scintillation Hodoscope Moller Shield CAD implementation FT-Cal: PbWO4 calorimeter FT-Hodo: Scintillator tiles FT-Trck: MicroMegas detectors electron energy/momentum Photon energy (ν=e-e') Polarization ε ν2/2ee veto for photons Edinburgh+JMU+NSU electron angles and polarization plane Saclay + Ohio 18 Quasi-real photons will be tagged by detection of scattered electrons at low forward angles electron beam on target, scattered electrons at small angles are detected by the forward detector Meson spectroscopy at JLab High- Forward Tagger Carlos Salgado M.Battaglieri - INFN GE Forward Drift Forward APS-Baltimore Meeting Preshower April,

37 CLAS12+Forward Tagger Detector CLAS12 will study the spectrum of mesons up to M ~ 2.8 GeV with a virtual photon beam, a large acceptance (neutrals and charged final particles) spectrometer, and search for mesons with sensitivities of a few percent of the total cross section. Project status Civil construction of accelerator is completed. CLAS12 experimental equipment is being completed. The Forward Tagger Detector is planned for installation in 2016 Hall B commissioning by the end of First physics beam expected for Carlos Salgado APS-Baltimore Meeting April,

38 Conclusions Meson Spectroscopy together with LQCD calculations promise to provide a window to detailed studies of strong interactions at intermediate energies High-statistics experiments : (GlueX/CLAS12 - Compass - Panda) Two Meson Spectroscopy programs at Jefferson Lab CLAS12 using a beam of quasi-real photons GlueX using a linearly polarized real photon beam Analysis progress : Theory: improve models - include more constraints in PWA Computing: increase computer efficiency - Parallel computing - vectorization of existing code (GPU, Xeon Phi). Faster / user friendly. Algorithms: Minimization/Optimization (Genetic Algorithms,...) For a good understanding of the meson spectrum we will need to analyze data from different beams (production mechanisms), different channels (coupled channel analysis) and consider an improvement in our analysis tools accordingly with the expected high statics experiments. Thank you for listening! Carlos Salgado APS-Baltimore Meeting April,