# Presentation: 528585

## 1

**Notes:**
doc

## Science of Confinement

**Science of Confinement**

**•****  ****The spectroscopy of light mesons  led to the quark model and QCD: mesons are quark-antiquark color singlet bound states held together by gluons. **

## Science of Confinement

**Science of Confinement**

**•**** ****The excitations of these flux tubes give rise to new hybrid mesons and their spectroscopy will provide the essential experimental data that will lead to an understanding of the confinement mechanism of QCD.  **

**•**** ****A subset of these mesons - *****exotic hybrid mesons***** - have unique experimental signatures.  Their spectrum has not yet been uncovered but there is strong reason to believe that photons are the ideal probe to map out the spectrum of this new form of matter.  **

***This is  the goal of the GlueX Experiment***

**•**** ****The gluons are thought to form flux tubes which are responsible for confinement – flux tubes are predicted by both models and lattice QCD.  **

## Normal Mesons – qq color singlet bound states

**Spin/angular momentum configurations & radial excitations generate our known spectrum of light quark mesons.**

**Starting with ****u**** - ****d**** - ****s****  we expect to find mesons grouped in ****nonets**** - each**
**characterized by a given ****J****, ****P**** and ****C****. **

## Early Notion of Flux Tubes

## Early Lattice Calculations Also Predict Flux Tubes

**From G. Bali:  quenched QCD with heavy quarks**

## Exciting the Flux Tube

**Normal meson:****flux tube in ground state**

## Quantum Numbers for Hybrid Mesons

**Quantum Numbers for Hybrid Mesons**

**Quarks**

**Excited ****Flux Tube**

**Hybrid Meson**

**like**

**like**

**So only parallel quark spins lead to exotic J****PC**

## Hybrid Mesons

## Hybrid Masses

**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****2**

- 1-+
- 0+-
- 2+-

- Splitting  0.20

**Notes:**
Splitting = 0.20 GeV between 1-+ and 0+- comes from?

## Meson Map

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

**Radial **
**excitations**

** ****(L = qq angular momentum)**

**Meson Map**

## First Evidence for an Exotic Hybrid from E852

**At 18 GeV/c**

## Results of Partial Wave Analysis

**Benchmark**
**resonances**

## An Exotic Signal in E852

**Exotic**
**Signal**

## Experiment E852 Used  Probes

**Exotic hybrids**** suppressed**

**Extensive search with some evidence ****but a tiny part of the signal**

**Quark spins ****anti-aligned**

## Exotic Hybrids Will Be Found More Easily in Photoproduction

**Production of exotic****hybrids favored.****Almost no data available**

**Quark spins**** already aligned**

## Comparing

**Due to:****	****Coupling at both vertices****	****t-dependence of exchanges**

**Szczepaniak and Swat**

## Photoproduction and Pion Data

**BNL**

**SLAC**

**18 GeV/c**

**19 GeV**

**a****2**

**a****2**

**We will use for comparison – the yields for production ****of the well-established and understood a****2**** meson **

## Hybrid Candidates?

**Hybrid Candidates?**

**Confirmed by VES**
**More E852 3******** data to be analyzed**

**Confirmed by****Crystal Barrel****similar mass, width**

**Being re-analyzed**

**New results: No consistent B-W resonance interpretation for the P-wave**

**In all E852 sightings the P-wave is small ****compared to a2.  For CB P-wave and a2 similar in strength**

## E852 Experiment at BNL

- After PWA:

**Conclusion: an exotic signal at**
**a mass of 1400 MeV and width**
**of about 385 MeV**

## Neutral 

**Neutral ******

**Neutral vs charged production:**
**   ****C is a good quantum number**
**   ****a****o**** and a****2**** are produced ****(helps with ambiguities)**
**   ****only one detector involved**** **

## Neutral 

**Neutral ******

**Angular distributions fitted****to obtain PWA fits - ****mathematical ambiguities****present **
**Moments of spherical ****harmonics also fitted - these****are not ambiguous**

**Waves included:**

**Details of D-wave solutions:**

**Conclusion:****  A P-wave is present but there is****no consistent BW-resonance behavior but it****consistent with final state interactions.**

## Leakage Studies

**It is essential to understand the detector**

**Monte Carlo studies - E852**

## 3 Studies

**to continue with**
**10M event sample**

**amplitude**

**amplitude**

**phase**

**Sample results:**

## Physics Analysis Center

****** ****challenge an example**

**GlueX and CLEO-c (Cornell) are collaborating on proposals to DOE and NSF ITR to fund physics analysis center to solve common problems:**
**Large datasets**
**Understanding PWA**

## Complementarity

**Glueballs**** & ****CLEO-c**

**Hybrids**
**&**
**Hall D****GlueX**

## Goal: Map out Nonets

**Goal: ****Map out Nonets**

**The candidate states have ****couplings to vector + meson**

**Note that |S| = 1 states****do not have well-defined C**

## Decays of Hybrids

- Decay calculations are model dependent -  the 3P0  describes  normal meson decays.

- 0++ quantum numbers (3P0)

- The angular momentum in the flux tube stays in one of
- the daughter mesons  (L=1) and (L=0) meson.

- L=0: ,,,,...
- L=1: a,b,h,f,...

- ,, ...  not preferred.

**Notes:**
The statement about where angular momentum goes does not come from the 3P0 model?

## Strangeonium

**Mapping out the hybrid spectrum requires an understanding of normal mesons as well**
**Strangeonium is a bridge between lighter quark sector and charmonium**
**Only 5 strangeonium states are well-established.**
**In contrast to ******** and K beams, photoproduction will be particularly effective in producing strangeonium.  **

## Strangeonium Decays

**OZI-favored modes:**

**Known states:**

## What is Needed?

**What is Needed?**

**  ****PWA requires that the entire event be kinematically identified  - all ****    particles detected, measured and identified. It is also important ****    that there be sensitivity to a wide variety of decay channels to test****    theoretical predictions for decay modes.**

**    ****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:**

**Polarization  is required by the PWA - linearly polarized photons are  eigenstates of parity. **

**Linearly Polarized, CW  Photon Beam:**

**CW beam minimizes detector deadtime, permitting dramatically higher rates**

**Notes:**
Mention duty factor and emittance
9 GeV linearly polarized photon -->> .ge. 12 geV electrons

## What Photon Beam Energy is Needed?

**What Photon Beam Energy is Needed?**

**The mass reach of GlueX is up to about 2.5 GeV/c****2**** so the photon energy must at least be 5.8 GeV.  But the energy must be higher than this so that:**
**Mesons have enough boost so decay products are detected and measured with sufficient accuracy.**
**Line shape distortion for higher mass mesons is minimized.**
**Meson and baryon resonance regions are kinematically distinguishable. **

**But the photon energy should be low enough so that:**
**An all solenoidal geometry (ideal for hermeticity) can still measure decay products with sufficient accuracy.**
**Background processes are minimized.**

**9 GeV photons ideal**

## What Electron Beam Characteristics  Are Required?

**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. **

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

**The detector must operate with minimum dead time **

## Linear Polarization - I

**Suppose we produce a vector via exchange**
**of spin 0 particle and then V ******** SS**

**Loss in degree**
**of polarization**
**requires corresponding**
**increase in stats**

**V**

**J=0**

## Linear Polarization - II

**Suppose we want to determine**
**exchange: O****+**** from 0****- ****or A****N**** from A****U**

**X**

**J=0****–**** or 0****+**

**V**

## Coherent Bremsstrahlung

**flux**

**photon energy (GeV)**

**12 GeV electrons**

**Coherent ****Bremsstrahlung**

**This technique provides requisite energy, flux and polarization**

**electrons in**

**Linearly polarized**
**photons out**

**spectrometer**

**diamond**
**crystal**

**Notes:**
Make wiggly line - label polarized photon - show strips

## Detector

- Lead Glass

- 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

**Project was externally reviewed and recognized as being ****definitive and technically sound.**
**JLab is ****unique for this study****.**

**Notes:**
Space between 180 and kk
Cosmetics on tagger

## Solenoid & Lead Glass Array

- At SLAC

**Now at JLab**

**MEGA magnet at LANL**

**Lead glass array**

**Magnet arrives in Bloomington**

## Computational Challenge

**Computational Challenge**

**•****  ****GlueX will collect data at 100 MB/sec or 1 Petabyte/year - comparable to LHC-type experiments.**

**• ****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.**

## Experiment/Theory Collaboration

**Experiment/Theory Collaboration**

**•****  ****From the very start of the GlueX collaboration, theorists have worked closely with experimentalists on the design of the experiment, analysis issues and plans for extracting and interpreting physics from the data.**

**•**** ****The PWA formalism is being developed with the goal of understanding how to minimize biases and systematic errors due to dynamical uncertainties - e.g. overlap of meson and baryon resonance production.**

**•**** ****INT (Seattle) will sponsor a joint workshop with JLab in early 2003 devoted to the physics of GlueX and a proposal for a 3-month program at INT in 2004 on GlueX physics has been submitted.**

**•**** ****Lattice QCD and model calculations of the hybrid spectrum and decay modes will guide the experimental search priorities. The Lattice QCD group computers at JLab should move into the 10 Teraflop/year regime by 2005 - in time to impact GlueX planning. **

## Testing the Capabilities of theGlueX Experiment Design

**Testing the Capabilities of the****GlueX Experiment Design**

**Double-blind ****Monte Carlo exercise**

**Starting assumption:****  ****An exotic signal mixed in with 7 other states to mimic the BNL yield – **
**a factor of 20 down from what is expected in photoproduction.**

**Even if the hybrids are produced at a rate well below expectation, we will see them easily**

## How GlueX Fares Compared to Existing Data

**BNL**

**SLAC**

**18 GeV/c**

**19 GeV**

**a****2**

**a****2**

**We will use for comparison – the yields for production ****of the well-established and understood a****2**** meson **

## How GlueX Fares Compared to Existing Data

| Experiment | a2 yield | Exotic Yield |
| --- | --- | --- |
| SLAC | 102 | -- |
| BNL (published) | 104 | 250 |
| BNL (in hand - to be analyzed) | 105 | 2500 |
| GlueX | 107 | 5x 106 |

**GlueX estimates are based on 1 year of low intensity running (10****7**** photons/sec)**

**We will use for comparison – the yields for production ****of the well-established and understood a****2**** meson **

**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**

## Conclusions

**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.**

**•**** ****And the GlueX Detector will be a versatile tool for all meson production**
**      ****and decay studies - ****an electronic bubble chamber.**

## Backups

**Backups**

**The following****slides are backups**

## LQCD

*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***

*10**0*

*10**-1*

*10**-4*

*10**-6*

*1974*

***Lattice Meson spectrum agrees with Experiment.**** *

*10**1*

*10**2*

*10**-3*

*10**-5*

***Flux tubes between Heavy Quarks  ***

***FY03 Clusters  0.5 TFlop/sec***

***FY06 Clusters ***
***8 Tflop/sec***

**LQCD**

**Notes:**
Hybrid mixing instead of decays
Hybrid in full qcd instead of full hybrid spectrum and remove ‘hints of confining potential’

## Phenomenology

**Model predictions for ****regular**** vs ****exotic**** meson prodution with photon and pion probes**

***Szczepaniak & Swat***

## Photoproduction of 3π at SLAC and JLab

**SLAC**

*similar cuts*

**SLAC**

**19 GeV**

**CLAS**

**5.7 GeV**

## 12 GeV Electrons  Suffice for GlueX

- photon energy = 9 GeV

**Given that 9 GeV photons are ideal**** - ****12 GeV electron energy**
**suffices**** but dropping below that energy seriously degrades ****the polarization and tagged hadronic rate (for a fixed total ****hadronic rate in the detector).**