Introduction Hadron Spectroscopy at GlueX Other Aspects of the GlueX Physics Program Summary and Outlook

Hadron Spectroscopy at GlueX and the Search for Gluonic Excitations

Volker Credé

Florida State University, Tallahassee, Florida

Int. Workshop on Hadron Structure and Spectroscopy Trieste, Italy 11/16/2020

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Other Aspects of the GlueX Physics Program Summary and Outlook Outline

1 Introduction Non-Perturbative QCD The GlueX Experiment

2 Hadron Spectroscopy at GlueX First Results Search for Doubly-Strange Ξ Baryons J/ψ Photoproduction at Threshold

3 Other Aspects of the GlueX Physics Program

4 Summary and Outlook The Search for Hybrid Mesons

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook Outline

1 Introduction Non-Perturbative QCD The GlueX Experiment

2 Hadron Spectroscopy at GlueX First Results Search for Doubly-Strange Ξ Baryons J/ψ Photoproduction at Threshold

3 Other Aspects of the GlueX Physics Program

4 Summary and Outlook The Search for Hybrid Mesons

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook Strong-Coupling Quantum Chromodynamics (QCD)

X µ QCD = Theory of the strong nuclear force LQCD = q¯ (iγµD − mq) q q Strong processes at larger distances and at 1 µν small (soft) momentum transfers belong to − F Fµν 4 the realm of non-perturbative QCD.

“pQCD” §

§ Confinement & Strong QCD “World of Hadrons” Asymptotic Freedom

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook Non-Perturbative QCD

How does QCD give rise to excited hadrons?

1 What is the origin of confinement?

2 How are confinement and chiral symmetry breaking connected?

3 What role do gluonic excitations play in the spectroscopy of light mesons, and can they help explain quark confinement? Baryons: What are the fundamental degrees of freedom inside a nucleon? Constituent quarks? How do the degrees change with varying quark masses? Mesons: What are the properties of the predicted states beyond simple quark- antiquark systems (hybrid mesons, glueballs, tetraquarks, ...)? § Gluonic Excitations provide a measurement of the excited QCD potential. Hybrid baryons are also possible ...

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook

Hadron Spectroscopy π + Nucleus

γ p Photoproduction

e+ e− p¯ p

The GlueX Collaboration ∼ 135 members, 29 institutions (Armenia, Canada, Chile, China, Germany, Greece, Russia, UK, USA) GlueX phase-I complete (120 PAC days) First physics published in 2017

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook

May 2014

Hall D

Jefferson Lab Upgrade to 12 GeV 10.1 GeV achieved, Fall 2014 GlueX commissioning in 2015

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook

Study of light-flavor (hybrid) mesons and baryons: Box Linearly-polarized photons; Box coherent edge at 9 GeV. Box High intensity (2018+). Goal: 5 x 107 γ/s (coh. peak) Sophisticated analysis tools. § Partial Wave Analysis (PWA)

∼ 75 m

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Non-Perturbative QCD Other Aspects of the GlueX Physics Program The GlueX Experiment Summary and Outlook The GlueX Experiment: Photon Beamline

7000 (a) 6000 Diamond: PARA Diamond: PERP Polarized photon beam produced via coherent 5000 Aluminum 4000

3000 bremsstrahlung off thin diamond radiator: Photon Flux (arb. units) 2000 Tagging system with ∆E < 25 MeV. 1000 7.5 8 8.5 9 9.5 10 10.5 11 11.5 0.5 (b) EPS (GeV) PARA 0.4 PERP

Linear photon polarization of Pγ ≈ 40 % in Polarization 0.3 0.2

the coherent peak. 0.1

0 1.5% Syst. Uncert. Polarization Photon Flux (a. u.) 8 7.5 8 8.5 9 9.5 10 10.5 11 11.5 Design intensity of 10 γ/s in peak. Photon Beam Energy (GeV)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Outline

1 Introduction Non-Perturbative QCD The GlueX Experiment

2 Hadron Spectroscopy at GlueX First Results Search for Doubly-Strange Ξ Baryons J/ψ Photoproduction at Threshold

3 Other Aspects of the GlueX Physics Program

4 Summary and Outlook The Search for Hybrid Mesons

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Quark-Model Classification: Ordinary & Exotic Mesons

PC 2S+1 Quantum Numbers J ≡ L J L = 0, S = 0 : PC −+ Parity: P = (−1)L+1 e.g. π, η (J = 0 ) L+S Charge Conjugation: C = (−1) L = 0, S = 1 : (defined for neutral mesons) e.g. ρ, ω, φ (JPC = 1−−) G parity: G = C (−1)I

12 GeV CEBAF upgrade has high priority (DOE Office of Science, Long Range Plan) “[key area] is experimental verification of the powerful force fields (flux tubes) believed to be responsible for quark confinement.”

Forbidden States (Exotics): JPC = 0+−, 0−−, 1−+, 2+−, ··· (hybrid kaons do not have exotic QNs)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Meson Spectroscopy on the Lattice

negativenegative parity parity positive positive parity parity exoticsexotics

2.5

2.0

1.5

1.0 Big Box § 1−− Lattice QCD Predictionsisoscalar PC +− 0.5 Constituent glueisovector with J = 1 −+ § 0 § Lightest nonet:YM glueball 1−−, (0−+, 1−+, 2−+)

J. J. Dudek et al., PRD 84, 074023 (2011)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Gluonic Excitations on the Lattice

J. J. Dudek and R. G. Edwards, Phys. Rev. D 85, 054016 (2012)

2000

1500

1000

mπ = 524 MeV mπ = 396 MeV

500 The mass scale is m − mρ for

0 mesons and m−mN for baryons.

Common scale of ∼ 1.3 GeV for gluonic excitation.

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Spectroscopy and Amplitude Analysis

Courtesy of Sean Dobbs

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Spectroscopy and Amplitude Analysis

Courtesy of Sean Dobbs

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook

First GlueX “Physics:” Initial Analyses §

7000 (a) H. Al Ghoul et al., PRC 95, 042201 (2017) 6000 Diamond: PARA Diamond: PERP Detector Understanding: 5000 Aluminum 0 4000 γp → p π 3000 γp → p η Photon Flux (arb. units) § Beam Asymmetries 2000 0 1000 γp → p η γp → K + Σ0 Initial Exotic 7.5 8 8.5 9 9.5 10 10.5 11 11.5 − ++ 0.5 (b) EPS (GeV) PARA γp → π ∆ Hybrid Searches 0.4 PERP γp → p ργ p → ηπ (p, ∆++) Polarization 0.3 γp → p ωγ p → η 0π (p, ∆++) 0.2 ++ Polarization Photon Flux (a. u.) γp → p φγ p → ρπ (p, ∆ ) 0.1 ++ § γp → ωπ (p, ∆ ) 0 1.5% Syst. Uncert. ++ 7.5 8 8.5 9 9.5 10 10.5 11 11.5 γp → ωππ (p, ∆ ) Photon Beam Energy (GeV) cross sections γp → ηππ (p, ∆++) SDMEs

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook

First GlueX “Physics:” Initial Analyses §

7000 (a) H. Al Ghoul et al., PRC 95, 042201 (2017) 6000 Diamond: PARA Diamond: PERP Detector Understanding: 5000 Aluminum 0 4000 γp → p π 3000 γp → p η Photon Flux (arb. units) § Beam Asymmetries 2000 0 1000 γp → p η γp → K + Σ0 Initial Exotic 7.5 8 8.5 9 9.5 10 10.5 11 11.5 − ++ 0.5 (b) EPS (GeV) PARA γp → π ∆ Hybrid Searches 0.4 PERP γp → p ργ p → ηπ (p, ∆++) Polarization 0.3 γp → p ωγ p → η 0π (p, ∆++) 0.2 ++ Polarization Photon Flux (a. u.) γp → p φγ p → ρπ (p, ∆ ) 0.1 γp → ωπ (p, ∆++) 0 1.5% Syst. Uncert. ++ 7.5 8 8.5 9 9.5 10 10.5 11 11.5 γp → p J/ψγ p → ωππ (p, ∆ ) Photon Beam Energy (GeV) γp → p BB γp → ηππ (p, ∆++)

Strange Baryons: γp → K +Λ, K Σ, KK Ξ

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Measurement of Beam Asymmetries: γp → p π0

Beam Asymmetry, Σ, yields information on production mechanism

Exchange of JPC 1−− : ω, ρ 1+− : b, h

|ω + ρ | − |h + b | Σ = |ω + ρ | + |h + b |

V. Mathieu et al., Phys. Rev. D 92, no. 7, 074004 (2015)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Measurement of Beam Asymmetries: γp → p π0

Beam Asymmetry, Σ, yields information on production mechanism

Experimentally:

PC Exchange of J Y⊥ − FRYk −− = Pγ Σ cos 2φp 1 : ω, ρ Y⊥ + FRYk 1+− : b, h

|ω + ρ | − |h + b | Σ = |ω + ρ | + |h + b |

V. Mathieu et al., Phys. Rev. D 92, no. 7, 074004 (2015)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Measurement of Beam Asymmetries: γp → p π0/η

1.4 Σ

(a) 0 H. Al Ghoul et al., Phys. Rev. C 95, no. 4, 042201 (2017) 1.2 γp → pπ

1 2.1% Norm. Uncert. Significantly improved data quality 0.8

0.6 First measurement of the η beam 0.4 asymmetry for 8.4 < E < 9.0 GeV. GlueX 8.4

(b) § No dip around −t = 0.5 GeV for π 1.2 γp → pη 1 0.8 Laget [5,6] Comparison with Regge calculations JPAC [7,8] 0.6 Donnachie [9] contributes to understanding of production 0.4 Goldstein [4] 0.2 mechanisms in photoproduction. 0 § -0.2 Step toward search for exotic mesons. -0.4 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 -t [(GeV/c)2]

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Measurement of Beam Asymmetries: γp → p η/η 0

η 1.2 S. Adhikari et al., Phys. Rev. C 100, no.5, 052201 (2019) Σ 2.1% Relative Uncertainty 1.1 Significantly improved data quality 1 0 0.9 First measurement of the (η)/η beam This Work GlueX (2017) 0.8 Laget asymmetries for 8.2 < Eγ < 8.8 GeV. JPAC EtaMAID 0.7 Goldstein Beam asymmetry close to unity: Ση ≈ 1 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 § Dominance of vector-meson exchange -t (GeV2) § −− ' No indication for 2 exchange

η 1.2 Σ 2.1% Relative Uncertainty 1.1 Comparison with Regge calculations 1 contributes to understanding of production 0.9 mechanisms in photoproduction. 0.8 This Work JPAC 0.7 § Step toward search for exotic mesons. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 -t (GeV 2)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Measurement of Beam Asymmetries

S. Adhikari et al., [arXiv:2009.07326 [nucl-ex]] γp → K + Σ0 2.0 Charge exchange process GlueX SLAC Dominated by π exchange at low |t| 1.5 Corthals et al. Guidal et al.

Σ 1.0 γp → π− ∆++ 1.0 0.5 Σ 0.8

0.6 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.4 -t (GeV2/c2) 0.2 0.0 Phys. Rev. C 101, no.6, 065206 (2020) -0.2

-0.4 Nys et al. (JPAC), PLB 779, 77 (2018) Consistent with unity -0.6 Yu and Kong, PLB 769, 262 (2017) § Dominant natural parity -0.8 exchange -1.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 |t| [(GeV/c) ]

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook The Ξ∗ Resonance Spectrum from Lattice QCD

R. Edwards et al., PRD 87, 054506 (2013)  P  1  1 + Ξ(1320) **** → Λπ I J = 2 2  P  1  3 + Ξ(1530) **** → Ξπ I J = 2 2  P  1  1 + 1  Ξ(1620) * → Ξπ ? I J = 2 2 or 2 −  P  1  1  Ξ(1690) *** I J = 2 2 − ?  P  1  3  Ξ(1820) *** → ΛKI J = 2 2 −  P  1  3  Ξ(1950) *** I J = 2 2 − ?  P  1  5 ? Ξ(2030) *** → Y KI J = 2 ≥ 2

− Decuplet 1. Excitation Band: (70, 11 ) Octet 70 = 210 ⊕ 48 ⊕ 28 ⊕ 21

Exhibits broad features expected of SU(6) ⊗ O(3) symmetry § Counting of states of each flavor and spin consistent with QM for the lowest negative- and positive-parity bands.

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Possible Production Mechanisms

+ K K +(Ξ−K +), K +(Ξ0K 0), K 0(Ξ0K +) + +* a) K / K § Cross sections, beam asymmetries (similar to p ππ & p KK ∗) p * * / + K + At other facilities (for comparison): K − + ∗− + +* 0 K p → K Ξ J-PARC b) K / K * K p → K + Ξ∗0 Hall D L ∗ p * * p p → Ξ X LHCb / + K p p → Ξ∗ Ξ PANDA e+ e− → Ξ∗ X Belle II, BES III

∗ W. Roberts et al., Phys. Rev. C 71, 055201 (2005)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook CLAS g11a: Excited States in γp → K +K +π− (X)

From the paper: Although a small enhancement is observed in the Ξ0π− invariant mass spectrum near the controversial 1-star Ξ−(1620) resonance, it is not possible to determine its exact nature without a full partial wave analysis. Phys. Rev. C 76, 025208 (2007)

Need high-statistics, high-energy data from ) 2 35 an experiment designed to see Ξ states: 30 M:1.5392 ± 0.0014 3- or 4-track trigger Γ:0.015 ± 0.005 25 N: 71 ± 26

2 Reconstruction of full decay chain Counts/(10 MeV/c 20 χ /Ndf: 30.0/ 31.0

Higher photon energy 15 Improved detectors 10

5 § CLAS 12 and GlueX at Jefferson Lab 0 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 M(Ξ0π-) (GeV/c2)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook CLAS g11a: Excited States in γp → K +K +π− (X)

From the paper: Although a small enhancement is observed in the Ξ0π− invariant mass spectrum near the controversial 1-star Ξ−(1620) resonance, it is not possible to determine its exact nature without a full partial wave analysis. Phys. Rev. C 76, 025208 (2007) Belle: PRL 122, 072501 (2019) )

2 600 Need high-statistics, high-energy data from (a) Ξ0( )(∗) an experiment designed to see Ξ states: 500 1620 Ξ0(1690) (∗∗∗) 3- or 4-track trigger 400

Reconstruction of full decay chain Events/(0.003 GeV/c 300 Higher photon energy 200 Improved detectors 100 § CLAS 12 and GlueX at Jefferson Lab 0 1.5 1.55 1.6 1.65 1.7 1.75

M Ξ π+ [GeV] − (L)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Possible Production Mechanisms

+ XXXXXXXXXXX K Ξ(1320)− + +* a) K / K Spring 2017 p * * / + K + K M(Λπ−) [ GeV ] + +* 0 b) Λ K / K * Study and Measurement of K− p * * Cross sections / + K Beam asymmetry − 0 γp → K + (K + Ξ−∗) → K + (p π− K −) K + Ξ − Ξ mass splitting

Ashley Ernst, Dissertation (2020), Florida State University

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Possible Production Mechanisms

+ K ∗ First observation of excited Ξ state + +* in photoproduction with a) K / K ≈ 700 Ξ(1820)− signal events p * * / + Peak significance > 10σ K + K Ξ(1820)− + +* 0 b) Λ K / K * GlueX Phase-I K− p * * / + K

γp → K + (K + Ξ−∗) → K + (p π− K −) K +

M(ΛK −) [ GeV ] Ashley Ernst, Dissertation (2020), Florida State University

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook J/ψ Photoproduction Near Threshold

Photoproduction of J/ψ (near threshold) provides clean laboratory to study cc¯: Probes gluon distribution in proton (D. Kharzeev et al., Nucl. Phys. A 661, 568 (1999)) Sensitive to multi-quark correlations (S. Brodsky et al., Phys. Lett. B 498, 23 (2001))

c c γ _ γ _ c c g g g

g p p g

(a) (b)X leadingX twist higher twist

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook J/ψ Photoproduction Near Threshold § Photoproduction of J/ψ (near threshold) provides clean laboratory to study cc¯: Probes gluon distribution in proton Sensitive to multi-quark correlations Intriguing possibility of five-quark

interaction Σ + 0 Σ + 0 c D c D*

1200 data LHCb total fit 1000 Pc (4450) background 800

600 Weighted candidates/(2 MeV)

400 + + + P c(4440) P c(4457) P c(4312) 200

0 4200 4250 4300 4350 4400 4450 4500 4550 4600 mJ/ψp [MeV] mJ/ψ p [GeV] R. Aaij et al., PRL 122, 222001 (2019)

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Observation of J/ψ at GlueX

A. Ali et al. [ GlueX ], Phys. Rev. Lett. 123, no.7, 072001 (2019)

ψ ± 200 100 Number of J/ = 469 22 mean = 3.096 ± 0.001 GeV 180 80 SD = 0.013 ± 0.001 GeV 160 60

40

events/5 MeV 140 120 20 100 0 2.95 3 3.05 3.1 3.15 3.2 80 60 40 20 0 1 1.5 2 2.5 3 3.5 M(e+e-), GeV

First observation of J/ψ at Jefferson Lab in γp → p J/ψ → p e+e− First detailed look at cross section near threshold 2 Measurement of t slope (8.2 - 12 GeV): (2.01 ± 0.36 stat.) GeV Limits on pentaquark production

V. Credé Hadron Spectroscopy at GlueX Introduction First Results Hadron Spectroscopy at GlueX Search for Doubly-Strange Ξ Baryons Other Aspects of the GlueX Physics Program J/ψ Photoproduction at Threshold Summary and Outlook Observation of J/ψ at GlueX

A. Ali et al. [ GlueX ], Phys. Rev. Lett. 123, no.7, 072001 (2019)

10 p), nb ψ 2 χ2 / n.d.f. = 0.843 / 5 J/ ± -2 → slope = -1.67 0.35 GeV p γ ( σ

/dt, nb/GeV 1 1

σ GlueX d SLAC Cornell Kharzeev et al. x 2.3 + JPAC Pc(4440) incoherent sum of: 2g exch. Brodsky et al −1 10 3g exch. Brodsky et al 0 0.2 0.4 0.6 0.8 1 2 8 9 10 20 -(t-t ), GeV Eγ, GeV min

First observation of J/ψ at Jefferson Lab in γp → p J/ψ → p e+e− First detailed look at cross section near threshold −2 Measurement of t slope (at 10.7 GeV avg. Eγ ):( −1.67 ± 0.39) GeV Limits on pentaquark production

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Other Aspects of the GlueX Physics Program Summary and Outlook Outline

1 Introduction Non-Perturbative QCD The GlueX Experiment

2 Hadron Spectroscopy at GlueX First Results Search for Doubly-Strange Ξ Baryons J/ψ Photoproduction at Threshold

3 Other Aspects of the GlueX Physics Program

4 Summary and Outlook The Search for Hybrid Mesons

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Other Aspects of the GlueX Physics Program Summary and Outlook Planned Experiments at Jefferson Lab

Broad and rich physics program in Hall D using the GlueX detector: Mapping the Spectrum of Light-Quark Mesons and Gluonic Excitations with Linearly-Polarized Photons. (GlueX Phase-I) A study of decays to strange final states with GlueX in Hall D using components of the BaBar DIRC. (arXiv:1408.0215) Precision Measurement of η Radiative Decay Width via Primakoff Effect. Measuring the Charged-π/(π0) Polarizibility in the γγ → π+π− Reaction. Symmetry Tests of Rare η Decays to All-Neutral Final States.

Probing QCD in the nuclear medium with real photons and nuclear targets at GlueX Photoproduction of vector mesons on nuclei with GlueX

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX Other Aspects of the GlueX Physics Program Summary and Outlook Planned Experiments at Jefferson Lab

Broad and rich physics program in Hall D using the GlueX detector: Mapping the Spectrum of Light-Quark Mesons and Gluonic Excitations with Linearly-Polarized Photons. (GlueX Phase-I) A study of decays to strange final states with GlueX in Hall D using components of the BaBar DIRC. (arXiv:1408.0215) Precision Measurement of η Radiative Decay Width via Primakoff Effect. Measuring the Charged-π/(π0) Polarizibility in the γγ → π+π− Reaction. Symmetry Tests of Rare η Decays to All-Neutral Final States.

Probing QCD in the nuclear medium with real photons and nuclear targets at GlueX Photoproduction of vector mesons on nuclei with GlueX

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook Outline

1 Introduction Non-Perturbative QCD The GlueX Experiment

2 Hadron Spectroscopy at GlueX First Results Search for Doubly-Strange Ξ Baryons J/ψ Photoproduction at Threshold

3 Other Aspects of the GlueX Physics Program

4 Summary and Outlook The Search for Hybrid Mesons

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook Summary

Early GlueX data show rich prospects for hadron spectroscopy: § High-luminosity running (+ BaBar DIRC detectors) will extend the program to strange-quark states.

First observation of Charmonium at JLab!!

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook Outlook

The GlueX experiment is ideally suited to study the spectrum of light-flavor mesons up to M ≈ 2.8 GeV and – if existing – the pattern of the gluonic excitations produced in γp collisions: It is important to establish the existence and the nonet nature of the 1−+ state (and of 0+−, 2+−)

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook COMPASS Experiment: π− p → η(0) π− (p)

C. Adolph et al., PLB 740, 303 (2015)

2 1−+ Exotic Wave 2 /c 600 250

/c 5000 0 − 500 η π P-wave, 200 4000 = 400 16 L 1 [deg] 150 14 3000 2 300 12 100 Φ 2000 50 200 − 0 1 Acceptance [%] 1000 100 Φ -50 0

0 Events / 40 MeV Entries / 20 MeV 1.5 2 2.5 3 3.5 4 4.5 5 1.2 1.6 2 2.4 2.8 0.8 1.2 1.6 2 2.4 2.8 2 m(η π ) [GeV/c2] m(η( )π ) [GeV/c2] m(η0π−) [GeV/c ] 0 − 0 − Collaboration refrains from proposing resonance parameters for exotic P wave. Odd partial waves with L = 1, 3, 5 (non-qq¯ QN) suppressed in ηπ− with respect to η0π−. Even partial waves similar (intensity & phase behavior). Dominant 8 ⊗ 8 (ηπ) & 1 ⊗ 8 (η0π) nature of SU(3) flavor configurations § gqq¯ and qqq¯ q¯ configurations predicted to have 1 ⊗ 8 character.

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook Outlook

The GlueX experiment is ideally suited to study the spectrum of light-flavor mesons up to M ≈ 2.8 GeV and – if existing – the pattern of the gluonic excitations produced in γp collisions: It is important to establish the existence and the nonet nature of the 1−+ state (and of 0+−, 2+−) For a given produced resonance, linear polarization will allows us to distinguish between naturalities of exchanged particles. Analysis of ~γp → η(0) π− (p) priority for GlueX Sufficient data available to explore the ηπ and η 0π systems with competitive statistics Multiple charge combinations and decay modes accessible Close collaboration with JPAC

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook Outlook

The GlueX experiment is ideally suited to study the spectrum of light-flavor mesons up to M ≈ 2.8 GeV and – if existing – the pattern of the gluonic excitations produced in γp collisions: It is important to establish the existence and the nonet nature of the 1−+ state (and of 0+−, 2+−) For a given produced resonance, linear polarization will allows us to distinguish between naturalities of exchanged particles. About 70 % of the photoproduction cross section in the energy region Eγ ∼ 7 − 12 GeV has multiple neutrals and is completely unexplored. § Many opportunities for GlueX to make key experimental advances in our knowledge of excited mesons and baryons. Advances in both theory and experiment will allow us to finally understand QCD and confinement.

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook

Backup Slides

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook

Barrel CALorimeter (BCAL): 2.0 T superconducting solenoid 48 4-m long modules

§ § Coh. Peak: 8.4 - 9.0 GeV ~γσ E/E ∼ 0.1 %, P∼ 40 % h± σp/p ∼ 1- 3 % √

γσ E/E ∼ 6 %/ E ⊕ 2 % § FCAL: 2800 lead glass

§ § blocks Goniometer: 20 µm diamond

TOF: two planes of CDC: 28-layer FDC: four six-plane 2.5 cm scintillator bars straw-tube chamber forward drift chambers

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook The JPC = 1−+ Exotic Wave: E852 Experiment

There is convincing evidence for an exotic JPC = 1−+ wave.

1 π1(1400) → ηπ 0 2 π1(1600) → η π; f1(1285)π § Natural-parity exchange. ? π1(1600) → b1π § Unnatural-parity exchange dominates.

π1(1600) → ρπ M = 0−, 1− M = 1+

π(1600) → ρπ (E852 : π−p → π+2π− p) +29 M = 1598 ± 8−47 MeV +150 Γ = 168 ± 20−12 MeV

§ Better understanding requires a spectrum of hybrid mesons.

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook The JPC = 1−+ Exotic Wave: E852 Experiment

There is convincing evidence for an exotic JPC = 1−+ wave.

1 π1(1400) → ηπ 0 2 π1(1600) → η π; f1(1285)π § Natural-parity exchange. ? π1(1600) → b1π § Unnatural-parity exchange dominates.

π1(1600) → ρπ M = 0−, 1− M = 1+

π(1600) → ρπ (E852 : π−p → π+2π− p) +29 M = 1598 ± 8−47 MeV +150 Γ = 168 ± 20−12 MeV

§ Better understanding requires a spectrum of hybrid mesons.

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook COMPASS Experiment (1): π− Pb → π−π−π+ (Pb)

M. Alekseev et al., PRL 104, 241803 (2010)

×103 −+ ) 2 3.5 1 Exotic Wave

a (1320) ) 2 event distribution 2 -+ +ρπ 150 3 800 1 1−+ P + (d)P π , π → constant ∆φ?(b) background wave 1 1 ρπ P 1 2 700 100 2.5 a (1260) 1 600 50

2 π 500 Phase (degrees) 2(1670) 0 Events / (5 MeV/c 1.5 400

Intensity / (40 MeV/c -50 300 1 -100 200 −+ −+ 0.5 -150 ∆φ∆(φ1 -+ +ρπ− 2-+ + π) 100 (1 1 P - 2 0 f 2 S) 0 0 -200 0 0.5 1 1.5 2 2.5 3 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 Mass of π-π-π+ System (GeV/c2) Mass of π-π-π+ System (GeV/c2) Mass of π-π-π+ System (GeV/c2) Based on ∼ 420, 000 events using a 180 GeV π beam:

π1(1600): M = 1660 MeV π2(1670): M = 1658 MeV Γ = 269 MeV Γ = 271 MeV § Exotic 1−+ wave dominantly produced in natural-parity (M = 1+) exchange.

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook COMPASS Experiment (2): π− p → η(0) π− (p)

C. Adolph et al., PLB 740, 303 (2015)

2 1−+ Exotic Wave 2 /c 600 250

/c 5000 0 − 500 η π P-wave, 200 4000 = 400 16 L 1 [deg] 150 14 3000 2 300 12 100 Φ 2000 50 200 − 0 1 Acceptance [%] 1000 100 Φ -50 0

0 Events / 40 MeV Entries / 20 MeV 1.5 2 2.5 3 3.5 4 4.5 5 1.2 1.6 2 2.4 2.8 0.8 1.2 1.6 2 2.4 2.8 2 m(η π ) [GeV/c2] m(η( )π ) [GeV/c2] m(η0π−) [GeV/c ] 0 − 0 − Collaboration refrains from proposing resonance parameters for exotic P wave. Odd partial waves with L = 1, 3, 5 (non-qq¯ QN) suppressed in ηπ− with respect to η0π−. Even partial waves similar (intensity & phase behavior). Dominant 8 ⊗ 8 (ηπ) & 1 ⊗ 8 (η0π) nature of SU(3) flavor configurations § gqq¯ and qqq¯ q¯ configurations predicted to have 1 ⊗ 8 character.

V. Credé Hadron Spectroscopy at GlueX Introduction Hadron Spectroscopy at GlueX The Search for Hybrid Mesons Other Aspects of the GlueX Physics Program Summary and Outlook Meson Spectroscopy in Photoproduction: CLAS

Results on light mesons from CLAS at Jefferson Lab Search for the photo-excitation of exotic mesons in the π+π+π− system: (M. Nozar et al., Phys. Rev. Lett. 102, 102002 (2009))

3 ×10 70 a. -+ b. -+ − 60 2 ( ) 2 (f ) π P,F 2 S 50 40 P P? 30 p 20 Events/40 MeV 10 charge exchange neutral exchange

×103 50 CLAS E852 45 c. ++ d. -+ 40 1 ( ) 1 ( ) S P 35 1(1600)? 30 25 20 CLAS does not observe a resonant 15 −+ 10 Events/40 MeV structure in the 1 (ρπ)P partial wave. 5 0 1 1.2 1.4 1.6 1.8 2 1 1.2 1.4 1.6 1.8 2 M(++-) (GeV) M(++-) (GeV)

V. Credé Hadron Spectroscopy at GlueX