It takes glue to study the “Glue”

Montreal Joint High Energy Physics Seminar November 28, 2002

It takes glue to study the “Glue”

Zisis Papandreou

Dept. of Physics University of Regina

Zisis Papandreou

Dept. of Physics University of Regina

Canadians:

Regina,Carleton

Re fe re nc es

Design Report will be available soon Nov 2002

Sept/Oct 2000

Feb 2001

Sept 2000 JLab whitepaper

Cover story article on exotics and Hall D

Article

on exotics and Hall D

All can be downloaded from the Hall D website

Scientific Goals and Means

• Definitive and detailed mapping of hybrid meson spectrum

• Quantitative understanding of confinement mechanism in Quantum Chromodynamics (QCD).

• Search for smoking gun signature of exotic J

hybrid mesons; these do not mix with qq states

• Tools for the GlueX Project:

– Accelerator: 12 GeV electrons, 9 GeV linearly polarized photons with high flux

– Detector: hermiticity, resolution, charged and neutrals, R&D – PWA Analysis: each reaction has multi-particle final states – Computing power: 1 Pb/year data collection, data grids,

distributed computing, web services…

-

u

d s c

b t

white white

Six Flavors of quarks

QCD is the theory of quarks and gluons

3 Colors

3 Anti-colors

8 Gluons, each with a color and

an anti-color charge.

) (

2 1 )

( 



 i D m tr G G

L

  

(colorless objects) confinement

GlueX Focus: “light-quark mesons”

qqq

q

q

Jets at High Energy

Direct evidence for gluons come from high energy jets.

But this doesn’t tell us anything about the “static”

properties of glue. We learn something about 

.

q

q

2-Jet

g q

q

3-Jet

gluon bremsstrahlung q ( q )  q ( q ) g

Deep Inelastic Scattering

As the nucleon is probed to smaller and smaller x, the gluons become more and more important. Much of the nucleon

momentum and most of its spin is carried by gluons!

Glue is important to hadronic structure.

x = q

/2M, 0<x<1

Strong QCD: See and systems. q q _qqq

white

white Nominally, glue is

not needed to

describe hadrons.

Allowed systems: , , gg , ggg q q g q q q q

Glueballs Hybrids Molecules

Gluonic Excitations

QCD and confinement

Large Distance Low Energy Small Distance

High Energy

Perturbative Regime

Non-Perturbative Regime

High Energy Scattering

Gluon ObservedJets

Spectroscopy

Gluonic

Degrees of Freedom Missing

Flux Tubes

Color Field: Gluons possess color charge: they couple to each other!

Dipole

Flux Tube

•1 electric charge

 carries no charge

•3 Color charges

•g carry charge

Notion of flux tubes comes about from model-independent

general considerations: observed linear dependence of m² on J.

Idea originated with Nambu in the ‘70s.

Flux Tubes and Confinement

Color Field: Because of self interaction, confining flux tubes form between static color charges

mesons

Linear potential: infinite energy required to separate qq.

-

Confinement arises from flux tubes !

Lattice QCD

Flux tubes realized

Flux tube forms between

qq

linear potential

0.4 0.8 1.2 1.6

1.0 2.0

0.0

r/fm Vo( r) [GeV]

From G. Bali

Lattice “measurement”

of quenched static potential

“Pluck” the Flux Tube

q

q

Normal meson:

flux tube in ground state

q

q

Hybrid meson:

flux tube in excited state

There are two degenerate first-excited transverse modes with J=1

– clockwise and counter-clockwise – and their linear combinations lead to J^PC = 1^{– +} or J^PC=1^{+ –} for

the excited flux-tube

How do we look for gluonic degrees of freedom in spectroscopy?

S L

S

1

2

S = S + S

J = L + S

C = (-1)

P = (-1)

Mass Difference

1 GeV/c² mass difference Hybrid mesons

Normal mesons r - quark separation

Normal Mesons

S L

S

1

2

S = S + S

J = L + S

C = (-1)

P = (-1)

Spin/angular momentum configurations

& radial excitations generate our known spectrum of light quark mesons

Nonets characterized by given J^PC

L=0, S=0: O^-+ pseudoscalar mesons L=0, S=1: 1^-- vector mesons

L=1, S=1: O⁺⁺ scalar, 1⁺⁺ axial vector, 2⁺⁺ tensor nonets

m=0 CP=(-1)

m=1 CP=(-1)

Flux-tube Model

ground-state flux-tube m=0

excited flux-tube m=1

built on quark-model mesons

CP={(-1)

}{(-1)

} ={(-1)

}

S=0,L=0,m=1 J=1 CP=+

J

=1

,1

non exotic

S=1,L=0,m=1 J=1 CP=-

J

=0

,0

1

,1

²

^,2

exotic

normal mesons

Hybrid Mesons

1

or 1





 , ,

exotic

 K

linear potential

ground-state flux-tube m=0

excited flux-tube m=1

Gluonic Excitations provide an experimental measurement of the excited QCD potential.

Observations of exotic quantum number nonets are the best experimental signal of gluonic excitations.

QCD Potential

Meson Map 1

Glueballs Hybrids

Mass (GeV)

1.0 1.5 2.0 2.5

qq Mesons

L = 0 1 2 3 4

S

I₃ K^

^

^– ^o

K^o K^o

K^–







Pseudoscalar

S

I₃

K *^o K *^

K *^o K *^–

^– ^o ^





Vector

J^PC = 1^-- J^PC = 0^-+

(L = qq angular momentum)

Each box corresponds to 4 nonets (2 for L=0)

(2S+1)

L

=

S

(2S+1)

L

=

S

Mass (GeV)

1.0 1.5 2.0 2.5

qq Mesons

L = 0 1 2 3 4

Each box corresponds to 4 nonets (2 for L=0)

Radial

excitations

(L = qq angular momentum)

exotic nonets

0

0

1

1

1

1

2

2

2

0

2

0

Glueballs Hybrids

Meson Map

0

1.6 GeV

^Lattice

1

1.9 GeV

Hybrid Predictions

Lattice calculations --- 1

nonet is the lightest UKQCD (97) 1.87  0.20

MILC (97) 1.97  0.30 MILC (99) 2.11  0.10 Lacock(99) 1.90  0.20 Mei(02) 2.01  0.10

~2.0 GeV/c

1

0

2

Splitting  0.20 Flux-tube model: 8 degenerate nonets

1

,1

0

,0

,1

,1

,2

,2

~1.9 GeV/c

S=0 S=1

Production of Exotics

A pion or kaon beam, when scattering occurs, can have its flux tube excited

or   beam

Quark spins anti-aligned

Much data in hand with some evidence for gluonic excitations (exotic hybrids are suppressed)

q

q

before

q

q

after

q

q

after

q

q

before



beam Almost no data in hand

in the mass region

where we expect to find exotic hybrids when flux tube is excited

Quark spins aligned

_ _

_ _

Phenomenology

Model predictions for regular vs exotic meson prodution with pion (S=0) and photon (S=1) probes

Szczepaniak & Swat

N N



e X

  ,  , 



I

(J

)=1

(1

)



I

(J

)=0

(1

)



I

(J

)=0

(1

)

K

I

(J

)= ½ ⁽¹

⁾



 



  b

, 







Couple to V.M + e

1

nonet

Exotics in Photoproduction

Hybrid Decays modes need to be measured

Partial Wave Analysis (PWA)

A simple example - identifying states which decay into 

Decay into ^^ implies J=L, P=(-1)^L and C=(-1)^L

Production and decay

point the way

N N

_

_

_e

_b

^p ^^n m_ p₁p₂²

t p_b p₁p₂²

_b _e

_

_



C.M.S.

dN

d cos ^{ YJ0 2}

Line shape and phase consistent with Breit-Wigner line shape

Low t

production

•Identify the J^PC of a meson

•Determine production amplitudes & mechanisms

•Include polarization of beam, target, spin and parity of resonances and daughters, relative angular momentum.

f()= (1/k) (C_l/l)sin_lP_l(cos) d = f()²d

cos

cos cos

Decay Angular Distributions

J^PC=2⁺⁺ J^PC=3^--

_b _e

_

_



C.M.S.

dN

d cos ^{ YJ0 2}

J^PC=1^--

Place PWA tools on firm footing, years before experiment

•effects of polarized and unpolarized beam

•detector acceptance (hermetic)

•Leakage of non-exotics into exotic signal

GlueX uses two parallel PWA codes for cross-checking!

500

400

300

200

100

0

1.8 1.6

1.4 1.2

PWA fit

Finding the Exotic Wave

The J exotic was in thePC

mix with other waves at the level of 2.5%

The generated mass and width are compared with those from PWA fits:

Mass

Input: 1600 MeV

Width

Input: 170 MeV

Output: 1598 +/- 3 MeV

Output: 173 +/- 11 MeV

500

400

300

200

100

0

1.8 1.6

1.4 1.2

Mass (3 pions) (GeV)

events/20 MeV generated

Statistics correspond to a few days of running

Double-blind MC exercise

 p 





n

J

=1



Current Evidence

Glueballs Hybrids

Overpopulation of the scalar nonet and LGT predictions suggest that the f₀(1500) is a glueball

See results from Crystal Barrel

J^PC = 1^-+ states reported

₁(1400) 

₁(1600) 

See results from BNL E852

Complication is

mixing with conventional qq states

Not without controversy

Have gluonic excitations

already been observed ?

f₀(1500) f₂(1270)

f₀(980) f₂(1565)+

700,000 ⁰⁰⁰ Events

Crystal Barrel Results

f₀(1500) 250,000 ⁰ Events

Discovery of the f₀(1500)

f

(1500)  ’, KK, 4

f

(1370)  

Crystal Barrel Results

Establishes the scalar nonet

Solidified the f₀(1370) Discovery of the a₀(1450)

p p3⁰

An Exotic Signal in E852

Leakage

Non-exotic WaveFrom

due to imperfectly understood acceptance

Exotic Signal

1 ^

Correlation of Phase

&

Intensity

M( 





) GeV / c 



3 m=1593+-8

=168+-20

’ m=1597+-10

=340+-40+-50

₁(1600)

What is Needed for the GlueX Experiment?



The detector should be hermetic for neutral and charged particles, with excellent resolution and particle identification capability. The way to achieve this is with a solenoidal-based detector.

Hermetic Detector:



Linearly Polarized, CW Photon Beam:



What Electron Beam Characteristics Are Required?

Coherent bremsstrahlung will be used to produce photons with linear polarization so the electron energy must be high enough to allow for a sufficiently high degree of polarization - which drops as the energy of the photons approaches the electron energy.

At least 12 GeV electrons

In order to reduce incoherent bremsstrahlung background collimation will be employed using 20 µm thick diamond wafers as radiators.

Small spot size and superior emittance

The detector must operate with minimum dead time

Duty factor approaching 1 (CW Beam)

What Photon Beam Energy is Needed?

The mass reach of GlueX is up to about 2.5 GeV/c² so the photon energy must at least be 5.8 GeV. Energy must be higher than this so that:

1. Mesons have enough boost so decay products are detected and measured with sufficient accuracy.

2. Line shape distortion for higher mass mesons is minimized.

3. Meson and baryon resonance regions are kinematically distinguishable.

But the photon energy should be low enough so that:

1. An all-solenoidal geometry (ideal for hermeticity) can still measure decay products with sufficient accuracy.

2. Background processes are minimized.

9 GeV photons ideal

Photon Beam Energy Figure of Merit

12

10

8

6

4

2

0

flux of photons: millions/sec

12 11

10 9

8 7

photon beam momentum (GeV)

endpoint energy = 12 GeV = 11 GeV

= 10 GeV Photon Flux in Coherent Peak

Total Hadronic Rate Constant at approx 20 KHz

0.6

0.5

0.4

0.3

0.2

0.1

0.0

linear polarization

12 11

10 9

8 7

photon beam momentum (GeV)

endpoint energy = 12 GeV = 11 GeV

= 10 GeV

Linear Polarization

electron energy

photon energy

Electron energy

Photon energy

Given that 9 GeV photons are ideal - 12 GeV electron energy suffices; lower than this seriously degrades polarization and tagged hadronic rate.

flux

photon energy (GeV) 12 GeV electrons

Coherent

Bremsstrahlung

This technique provides requisite

energy, flux and polarization

collimated

Incoherent &

coherent spectrum

tagged

with 0.1% resolution

40%

polarization in peak

electrons in

photons out

spectrometer diamond

crystal

Linear Polarization

Linear polarization is:









of parity. States of circular polarization are not.

M

SLAC BNL

18 GeV/c 19 GeV

 p  





n

^p  ^^^p a₂

a₂ We will use for comparison – the yields for production of the well-established and understood a₂ meson

Compare Pion and Photoproduction Data Rates

Photoproduction of 3π at SLAC and JLab

SLAC

similar cuts

 p  





n

SLAC 19 GeV CLAS

5.7 GeV

a₂ a₂

Experiment a₂ yield Exotic Yield

SLAC 10²

--

BNL (published) 10⁴ 250

BNL (in hand - to be analyzed) 10⁵ 2500

GlueX 10⁷ 5x 10⁶

More than 10⁴ increase

GlueX estimates are based on 1 year of low intensity running (10⁷ photons/sec)

Even if the exotics were produced at the suppressed rates measured in -production, we would have 250,000 exotic mesons in 1 year, and be able to carry out a full program of hybrid meson spectroscopy

How GlueX Compares to Existing Data

Computational Challenge

•

• GlueX will be able to make use of much of the infrastructure

developed for the LHC including the multi-tier computer architecture and the seamless virtual data architecture of the Grid.

• To get the physics out of the data, GlueX relies entirely on an

amplitude-based analysis - PWA – a challenge at the level necessary for GlueX. For example, visualization tools need to be designed and developed. Methods for fitting large data sets in parallel on processor farms need to be developed.

• Close collaboration with computer scientists has started and the collaboration is gaining experience with processor farms; Data Grid Workshop in Indiana in two weeks.

10^-2

1990 2000 2010

Lattice gauge theory invented

Quenched Hybrid Spectrum Hybrid Mixing Hybrids in Full QCD Exotic candidate

at BNL

First data from CEBAF @12 GeV Tflop-year

10⁰ 10^-1

10^-4

10^-6

1974

Lattice Meson spectrum agrees with Experiment.

10¹ 10²

10^-3

10^-5

Flux tubes between Heavy Quarks FY03 Clusters

0.5 TFlop/sec FY06 Clusters 8 Tflop/sec

LQCD

LRP

www.nscl.msu.edu/future/lrp2002.html

NSAC Long Range

Plan

LRP

www.nscl.msu.edu/future/lrp2002.html

Jefferson Lab Facility

Newport News, Virginia

A B C

Hall D will be

located here

D

6 GeV CEBAF 11

CHL-2 CHL-2

12

and power and power

supplies supplies

Two 0.6 GV linacs 1.1

Beam Power: 1MW Beam Current 5 µA Emittance: 10 nm-rad Energy Spread: 0.02%

GlueX Collaboration

US Experimental Groups

A. Dzierba (Spokesperson) - IU

C. Meyer (Deputy Spokesperson) - CMU E. Smith (JLab Hall D Group Leader)

L. Dennis (FSU) R. Jones (U Conn)

J. Kellie (Glasgow) A. Klein (ODU)

G. Lolos (Regina) (chair) A. Szczepaniak (IU)

Collaboration Board

Carnegie Mellon University Catholic University of America Christopher Newport University University of Connecticut

Florida International University Florida State University

Indiana University Jefferson Lab

Los Alamos National Lab Norfolk State University Old Dominion University Ohio University

University of Pittsburgh

Renssalaer Polytechnic Institute

University of Glasgow Institute for HEP - Protvino Moscow State University Budker Institute - Novosibirsk

University of Regina

CSSM & University of Adelaide Carleton University

Carnegie Mellon University

Insitute of Nuclear Physics - Cracow Hampton University

Indiana University Los Alamos

North Carolina Central University University of Pittsburgh

University of Tennessee/Oak Ridge

Other

Experimental Groups

Theory Group

100 collaborators 25 institutions

The impact of

• Chair of Collaboration board: George Lolos

• Hardware working group co-leader: Zisis Papandreou

• Software working group co-leader : Ed Brash

• Co-editors/co-authors of Conceptual Design Report:

– Physics (G. Lolos), Detector (Z. Papandreou), Software (E. Brash).

• Most recent Hall D Collaboration meeting was held at UofR.

• SPARRO has been tasked with the design and construction of the full barrel calorimeter: weight of 30 tons, 5,000 km of fibers, and a price tag of US$4,000,000.

• Initial R&D is ongoing at Regina; JLab discretionary funds

• Assembly and machining of full modules in Edmonton.

S ubatomic P hysics A t R egina with R esearch Offshore

GlueX Detector

Lead Glass Detector

Superconducting Solenoid

Electron Beam from CEBAF Coherent Bremsstrahlung

Photon Beam

Tracking Target

Cerenkov Counter

Time of Flight

Barrel Calorimeter

Note that tagger is 80 m upstream of

detector

Coils

Iron Yokes FDC

Barrel Calorimeter

CDC

Vertex Detector Target

GlueX Detector

Central Field:

2 Tesla

Detector Platform

Top View of the HALL

PLATFORM

• The Platform is 8 ft from the base

• Supports the extracted components

• Assists in assembling the parts

All Dimensions in Meters

Solenoid Assembly

Hall D

Barrel Calorimeter

Tracking Package

Rail System

Lead/scintillating fiber sandwich;

1-mm diameter fibers; 0.5mm sheets

PMT Readout

PMT Readout

Scintillating fiber

Barrel Calorimeter Design Issues

• Length of device (> 4 m)

• Shower containment/radiation lengths: ~16Xo

• Azimuthal granularity vs. PMT geometry & light collection

• Minimum energy deposition threshold: 20 MeV

• Neutral energy resolution balance (vs. FCAL)

– Fiber diameter & Pb thickness: uniform throughout?

• Charged vs. Neutral energy resolution balance

• Timing resolution vs. other subsystems

• Mechanical issues:

R&D at Regina:

•Monte Carlo

•Hardware: Readout, fibers, Pb/SciFi Matrix

BCAL Readout Configuration





Longitudinal View

K. Wolbaum

Even with SciFi bundling,

~540 HPMTs will be needed:

No of phi segments 54

Phi segment angle 0.116

HPD active area 5.07 cm²

HPD total area 20.3 cm²

Calorimeter thickness 20.27 cm

Outer calorimeter radius 89.71 cm

Calorimeter length 400 cm

No of HPMT’s 1080

o Length: 4.5 m

o Outer Radius: 90 cm o Thickness: 20-25 cm

$$ cost issue $$

Computational Tools for Simulations

 Energy resolution:

 Driving physics processes

 Detector subsystems relation

 Timing resolution:

 Detector subsystems relation

 Longitudinal position requirement?

 Detector subsystems relation

HDFast GEANT

Notes: use a₂ decay or fake to look at particle distributions; use known smearing from FCAL and KLOE to do the first order resolution

modeling. Is the missing mass resolution important?

 Neutral and charged particle energy deposition profile

 Readout granularity

 Lateral energy spread

 Verify back-of-the-envelope X₀

 Pb/SciFi/Glue detailed modeling

 Position resolution (vs. angle):

pos.res./N; shower algorithms Notes: results of simulations have to be reconciled with mechanical constraints (HPMT outer and inner diameter; area reduction factor from Winston cones).

Tools are now in place at Regina

What’s a Hybrid?

• Proximity-focused vacuum tube

• Fast rise- and fall-time (2, 12 ns)

• High QE for UV, Gain is 10⁵

• Insensitive to high magnetic fields

Fused silica window

 _{HV: -8kV}

 _{Bias: -80V}

 _Pre-amp

 _Shaper

2 Tesla Central Field means HPMTs

20m fiber or

light guides

Hybrid PMT

DEP PP0350G DEP PP0100Z

UofR HV regulator

• Gain 1600

• Discharging/RF solved

• Pre-amp selection

• Signals:

– NaI detector – Scintillator

• Parameters measured

• Personnel assigned

– V. Kovaltchouk – K. Wolbaum – B. Ramadan

• Moscow Institute

• Contact with DEP

• Light sources:

– NaI crystal and ²⁴¹Am, ¹³⁷Cs and ⁶⁰Co sources

– LED (pulsed): neutral density filter, fiber lightguide

• Measurements:

• HPD PP0350G with Multi- Channel Analyzer (Tektronix 5200) and DAQ System

• Bottom line: system works, needs a bit more R&D

HPMT Innards

CREMAT CR-101D

Optical Fiber Tests with 100MeV pions

• Properties:

– Light collection efficiency (cladding)

– Scintillation light production (doping)

– Light attenuation coefficient

– Timing resolution

• Fibers Types (single-, double-clad)

– Kuraray SCSF-81 – Pol.Hi.Tech. 0046

– Bicron (too expensive) M11 Experimental Area at TRIUMF August 2001

Attenuation Length

~3m

Fiber Optical Properties

• Quality Control

– Quick, reliable, reproducible – Optical source

– Dedicated spectrometer & DAQ – Transmission, attenuation, timing – Cross-check w/ ionization source

– Optical system: LED, optics, spectrometer, ADC

• Commercial system was used

• Components: SD2000 (dual channel)

spectrometer, ADC1000USB, laptop, fibers, neutral density filters, connectors, lenses, , optical grease, light source.

• Operation in Summer 2002 by L. Snook (NSERC Student).

• OOIBase32 software readout.

• Kuraray, PHT and Bicron 1mm-fibers have been tested for transmission and

attenuation.

”Cave” Optical System Setup

• Optical system

•Spectromet er •ADC

•Laptop

Master (Gold)

Slave (tests)

Master Branch (Gold fibers)

Slave Branch (Test fibers)

L. Snook

Coupling Reproducibility

Kuraray Multi-Clad 2002 Batch

4000

Wavelength (nm)

300 1100

Intensity

(from Aug. 8-12, 2002)

4000

Intensity

Wavelength (nm) ¹¹⁰⁰

1m (#2) 1m (#1) 2m

3m 4m 5m 10m

Kuraray Multi-Clad 2002 Batch

Attenuation Determination

Prototype Pb/SciFi Modules

Build in May 2002

with help from KLOE Folks

Prototype Module Construction

96 x 13 x 10 cm

70 kg

B. Klein, J. Kushniryk, T.Summers, G. Williams Lead Sheet Swaging

Matrix gluing & pressing

Inspection and cleaning

Conclusions

• An outstanding and fundamental question is the nature of confinement of quarks and gluons in QCD.

• Lattice QCD and phenomenology strongly indicate that the gluonic field between quarks forms flux-tubes and that these are responsible for confinement.

• The excitation of the gluonic field leads to an entirely new spectrum of mesons and their properties are predicted by lattice QCD.

• But data are needed to validate these predictions.

• Only now are the tools in place to carry out the definitive

experiment and JLab – with the energy upgrade – is unique for this search.

• If exotic hybrids are there, we will find them!

• In Regina, we will continue the R&D on MC, HPMTs and Pb/SciFi

We are eagerly awaiting CD-0 from the DOE.

The right people are in place - ready to make this happen

gluonic

Excitations

Workshop at JLab

May 14-16, 2003.