[PPT] - Spin-Density Matrix Elements for Vector-Meson Photoproduction at PowerPoint Presentation

SLIDE 1

Spin-Density Matrix Elements for Vector-Meson Photoproduction at GlueX

Alexander Austregesilo for the GlueX Collaboration 15th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2019) Carnegie Mellon University, Pittsburgh, PA June 3rd, 2019

SLIDE 2

Introduction Method Results Outlook

Outline

1

Introduction

2

Method Extended Maximum-Likelihood Fit Fit Evaluation

3

Results ρ(770) → π+π− ω(782) → π+π−π0 φ(1020) → K +K −

4

Outlook

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SLIDE 3

Introduction Method Results Outlook

GlueX Detector

barrel calorimeter time-of

flight

forward calorimeter photon beam electron beam electron beam superconducting magnet target tagger magnet tagger to detector distance is not to scale diamond wafer

GlueX

central drift chamber forward drift chambers start counter

Light quark meson spectroscopy with full angular coverage Data

L

Status (pb−1) 2016 1 analyzed 2017 20 analyzed 2018 ∼ 80 processing

2 T

→ S. Dobbs, Searching for Exotic Hadrons at GlueX (Monday morning)

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SLIDE 4

Introduction Method Results Outlook

Photon Beam Line

7.5 8 8.5 9 9.5 10 10.5 11 11.5

Photon Flux (Arb. Units)

1000 2000 3000 4000 5000 6000 7000

(a) Diamond: PARA Diamond: PERP Aluminum

Photon Beam Energy (GeV)

7.5 8 8.5 9 9.5 10 10.5 11 11.5

Polarization

0.1 0.2 0.3 0.4 0.5 3% Syst. Uncert.

PARA PERP (b)

9 GeV Polarized Photon Beam Coherent Bremsstrahlung on thin diamond Energy tagged by scattered electrons Collimator to suppress incoherent part Linear polarization in peak Pγ ∼ 40%, measured by Triplet polarimeter: γe− → e−e+e− Rotate polarization into 4 different orientations Beam intensity: 1 − 5 · 107 γ/s in peak

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SLIDE 5

Introduction Method Results Outlook

Photoproduction

p P, π, ρ, ... X p, n, ∆, ... γ (ρ, ω, φ)

Complementary Production Mechanism Photon coupling via vector meson dominance Wide variety of quantum numbers IGJPC accessible Photon polarization provides constraints on produced systems Understanding of production mechanism is prerequisite for interpretation Very limited photoproduction data existing at these energies Exchange Exotic Final States P 0++ b, h, h′ 2+−, 0+− π0 0−+ b2, h2, h′

2

2+− π± 0−+ π±

1

1−+ ω 1−− π1, η1, η′

1

1−+

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SLIDE 6

Introduction Method Results Outlook

Production Mechanism

Spin-Density Matrix Elements

Full angular distribution of vector meson production and decay is described by spin-density matrix elements ρk

ij

Linear beam polarization provides access to nine linearly independent SDMEs Intensity W is expressed as function of angles cos ϑ, ϕ, Φ and degree of polarization Pγ

z x y p γ ρ p′ Pγ Φ φ π+ π−

W(cos ϑ, ϕ, Φ) = W 0(cos ϑ, ϕ) − Pγ cos(2Φ)W 1(cos ϑ, ϕ) − Pγ sin(2Φ)W 2(cos ϑ, ϕ) W 0(cos ϑ, ϕ) = 3 4π 1 2 (1 − ρ0

00) +

1 2 (3ρ0

00 − 1) cos2 ϑ −

√ 2Reρ0

10 sin 2ϑ cos ϕ − ρ0 1−1 sin2 ϑ cos 2ϕ

W 1(cos ϑ, ϕ) =

3 4π

ρ1

11 sin2 ϑ + ρ1 00 cos2 ϑ −

√ 2Reρ1

10 sin 2ϑ cos ϕ − ρ1 1−1 sin2 ϑ cos 2ϕ

W 2(cos ϑ, ϕ) =

3 4π √ 2Imρ2

10 sin 2ϑ sin ϕ + Imρ2 1−1 sin2 ϑ sin 2ϕ

Schilling et al. [Nucl. Phy. B, 15 (1970) 397]
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SLIDE 7

Introduction Method Results Outlook

Previous Measurements

SLAC, Ballam et al. [Phy. Rev. D, 7 (1973) 3150]

ρ(770) Few thousand events, 7 bins in t s-channel helicity conservation: ρ1

1−1 = −Imρ2 1−1 = 0.5

in helicity frame, all others = 0 Parity asymmetry: Pσ = 2ρ1

1−1 − ρ1 00

Dominated by natural parity exchange P = (−1)J ω(782) Several hundred events, 3 bins in t φ(1020) Few hundred events, not binned in t

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SLIDE 8

Introduction Method Results Outlook

JPAC Model

Regge model, fit to SLAC data Detailed prediction for t-dependence of ρ, ω and φ meson production s-channel helicity conservation at t = 0

Mathieu et al. [Phy. Rev. D, 97 (2018) 094003] → Single and Double Meson Production at JLab (Tuesday)

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SLIDE 9

Introduction Method Results Outlook

Vector-Meson Photoproduction

γp → ρ(770)p

p ρ(770) π− π+ p γ

2

)

2

p Missing Mass Squared (GeV/c

−

π

+

π → p γ 50 − 40 − 30 − 20 − 10 − 10 20 30 40 50

3 −

10 ×

2

)

2

Events / 100 (MeV/c 0.5 1 1.5 2 2.5 3 3.5 4

6

10 × )

2

Invariant Mass (GeV/c

−

π

+

π 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2

2

Events / 2.5 MeV/c 0.1 0.2 0.3 0.4 0.5 0.6 0.7

6

10 ×

2

Squared 4-Momentum Transfer -t (GeV/c) 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

2

Events / 0.004 (GeV/c)

3

10

4

10

5

10

6

10

Full 2017 data: >10M signal events in each of the 4 orientations

A. Austregesilo (aaustreg@jlab.org) — Vector Meson SDMEs

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SLIDE 10

Introduction Method Results Outlook

Extraction of SDMEs

W(cos ϑ, ϕ, Φ) = W 0(cos ϑ, ϕ) − Pγ cos(2Φ)W 1(cos ϑ, ϕ) − Pγ sin(2Φ)W 2(cos ϑ, ϕ) Measured Intensity I(Ω) ∝ W(cos ϑ, ϕ, Φ) Extended Maximum-Likelihood Fit ln L =

N

i=1

ln I(Ωi)

Signal Events

−

M

j=1

ln I(Ωj)

Background

−

dΩ I(Ω) η(Ω)
Normalization Integral

Maximize by choosing SDMEs such that the intensity fits the observed N events Accidental background subtracted in likelihood Normalization integral evaluated by a phase-space Monte Carlo sample with the acceptance η(Ω) = 0/1

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SLIDE 11

Introduction Method Results Outlook

Fit Evaluation

γp → ρ(770)p, −t ∈ [0.05, 0.15] GeV2/c2

0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 5000 10000 15000 20000 25000 30000 35000 40000 45000

π

+

π Invariant Mass of

3 − 2 − 1 − 1 2 3 5000 10000 15000 20000 25000 30000

ϕ

Φ

= ψ

1 − 0.8 − 0.6 − 0.4 − 0.2 − 0.2 0.4 0.6 0.8 1 5000 10000 15000 20000 25000 30000

ϑ cos

3 − 2 − 1 − 1 2 3 5000 10000 15000 20000 25000

ϕ

black: measured distribution green: accepted MC, weighted with fit result red: accidental background

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SLIDE 12

Introduction Method Results Outlook

Result in Bins of Momentum Transfer t

γp → ρ(770)p

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 SCHC JPAC Model GlueX 2017 SLAC (Ballam et al.)

1 1-1

ρ

0.05 GeV2/c2 bin width in t Average of 4 orientations Errors dominated by systematics SCHC valid for t → 0 GeV2/c2 Agree with JPAC to ∼ 0.5 GeV2/c2

A. Austregesilo (aaustreg@jlab.org) — Vector Meson SDMEs

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SLIDE 13

Introduction Method Results Outlook

Result in Bins of Momentum Transfer t

γp → ρ(770)p

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 00

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

10

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 SCHC JPAC Model GlueX 2017 SLAC (Ballam et al.) 1-1

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

1 11

ρ )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 1 00

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

1 10

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

1 1-1

ρ )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

2 10

ρ Im )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 − 0.9 − 0.8 − 0.7 − 0.6 − 0.5 − 0.4 − 0.3 − 0.2 − 0.1 −

2 1-1

ρ Im

0.05 GeV2/c2 bin width in t Average of 4 orientations Errors dominated by systematics SCHC valid for t → 0 GeV2/c2 Agree with JPAC to ∼ 0.5 GeV2/c2

A. Austregesilo (aaustreg@jlab.org) — Vector Meson SDMEs

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SLIDE 14

Introduction Method Results Outlook

Result in Bins of Momentum Transfer t

γp → ρ(770)p

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 00

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

10

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 SCHC JPAC Model GlueX 2017 SLAC (Ballam et al.) 1-1

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

1 11

ρ )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 1 00

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

1 10

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

1 1-1

ρ )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

2 10

ρ Im )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 − 0.9 − 0.8 − 0.7 − 0.6 − 0.5 − 0.4 − 0.3 − 0.2 − 0.1 −

2 1-1

ρ Im

0.05 GeV2/c2 bin width in t Average of 4 orientations Errors dominated by systematics SCHC valid for t → 0 GeV2/c2 Agree with JPAC to ∼ 0.5 GeV2/c2

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 SCHC JPAC Model GlueX 2017 SLAC (Ballam et al.)

σ

P

Pσ = σN−σU

σN+σU = 2ρ1 1−1−ρ1 00

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SLIDE 15

Introduction Method Results Outlook

Parity Exchange

Ballam et al. [Phy. Rev. D, 7 (1973) 3150]

Spin-density matrix can be separated in contributions from natural and unnatural parity exchange in the t channel ρN,U

ik

= 1

2 (ρ0 ik ∓ (−1)iρ1 −ik) Schilling et al. [Nucl. Phy. B, 15 (1970) 397]

Only significant contribution from ρN

11

⇒ Dominant natural parity exchange

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SLIDE 16

Introduction Method Results Outlook

Parity Exchange

γp → ρ(770)p

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 11 N

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2 00 N

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2 SCHC JPAC Model GlueX 2017 SLAC (Ballam et al.) 1-1 N

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2

10 N

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2 11 U

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2 00 U

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2 1-1 U

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.2 − 0.15 − 0.1 − 0.05 − 0.05 0.1 0.15 0.2

10 U

ρ Re

Good agreement with JPAC for natural parity exchange at below 0.5 GeV2/c2 Excellent agreement for unnatural parity exchange

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SLIDE 17

Introduction Method Results Outlook

γp → ω(782)p

π+π−π0

p ω(782) π− π+ π0 p γ

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SLIDE 18

Introduction Method Results Outlook

ω(782) SDMEs

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

SCHC JPAC Model GlueX 2016 SLAC (Ballam et al.)

1 1−1

ρ

Only data of commissioning run 4 t bins in [0.1,0.8] GeV2/c2 Average of 2 orientations Good agreement with prediction Radiative decay also analyzed

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SLIDE 19

Introduction Method Results Outlook

ω(782) SDMEs

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 00

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

10

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 SCHC JPAC Model GlueX 2016 SLAC (Ballam et al.) 1-1

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

1 11

ρ )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5 1 00

ρ

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

1 10

ρ Re )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

1 1-1

ρ )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 − 0.4 − 0.3 − 0.2 − 0.1 − 0.1 0.2 0.3 0.4 0.5

2 10

ρ Im )

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 − 0.9 − 0.8 − 0.7 − 0.6 − 0.5 − 0.4 − 0.3 − 0.2 − 0.1 −

2 1-1

ρ Im

Only data of commissioning run 4 t bins in [0.1,0.8] GeV2/c2 Average of 2 orientations Good agreement with prediction Radiative decay also analyzed

)

2

/c

2

t (GeV

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 SCHC JPAC Model GlueX 2016 SLAC (Ballam et al.)

σ

P

Pσ = σN−σU

σN+σU = 2ρ1 1−1−ρ1 00

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SLIDE 20

Introduction Method Results Outlook

γp → φ(1020)p

K +K −

p φ(1020) K− K+ p γ

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SLIDE 21

Introduction Method Results Outlook

φ(1020) SDMEs

Only fraction of 2017 data 8 t bins in [0.2,1.0] GeV2/c2 Average of 4 orientations Good agreement with model

Titov et al. [Phys. Rev. C 60 (1999) 035205]

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SLIDE 22

Introduction Method Results Outlook

φ(1020) SDMEs

Only fraction of 2017 data 8 t bins in [0.2,1.0] GeV2/c2 Average of 4 orientations Good agreement with model

Titov et al. [Phys. Rev. C 60 (1999) 035205]

Pσ = σN−σU

σN+σU = 2ρ1 1−1−ρ1 00

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SLIDE 23

Introduction Method Results Outlook

Summary and Outlook

Summary Spin-density matrix elements extracted for ρ(770), ω(782) and φ(1020) Statistical precision increased by orders of magnitude Natural parity exchange dominates at Eγ = 9 GeV for t → 0 General agreement with models for t 0.5 GeV/2c2 Analysis also used to tune and confirm MC simulation

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SLIDE 24

Introduction Method Results Outlook

Summary and Outlook

Summary Spin-density matrix elements extracted for ρ(770), ω(782) and φ(1020) Statistical precision increased by orders of magnitude Natural parity exchange dominates at Eγ = 9 GeV for t → 0 General agreement with models for t 0.5 GeV/2c2 Analysis also used to tune and confirm MC simulation Outlook Full GlueX-I data set will be available this summer Results serve as input to improved model of production process Prerequisite for interpretation of exotic signals

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