# Presentation: 905956

## Hadronic Multi-particle Final State Measurements with CLAS at Jefferson Lab

- Laird Kramer
- Florida International University
- Neutrino Scattering, March 2003

**Notes:**
Goal is to familiarize audience with CLAS capabilities so as to appropriately plan next steps.

## Outline

- Overview of CLAS Physics Program
- Description of CLAS
- Samples of CLAS data and analysis
- Future nuclear target experiments
- Conclusions

## CLAS: the CEBAF Large Acceptance Spectrometer in Hall B at JLAB

- International collaboration of 160 scientists
- Physics data taking began end of 1997
- 17 major production runs completed
- Wide variety of run conditions:
- Electron/photon beams, 0.5<E<6 GeV (polarized)
- Targets: 1,2H (including polarized), 3,4He, 12C, 56Fe, etc.
- 50 PhD theses underway or completed
- More info at http://www.jlab.org/Hall-B

## CLAS Physics HighlightsBroad program: over 50 experiments

- Physics of excited nucleons (N* program)
- Neutron electromagnetic form factor
- Polarized structure functions
- Deep virtual Compton scattering (GPD’s)
- Quark/hadron propagation through nuclei
- Semi-inclusive deep inelastic scattering
- Exotic meson searches
- Elementary hyperon photoproduction
- Two-nucleon correlations in light nuclei

**Notes:**
How many collaborators, how many institutions
Extension to resnoance production and propagation in nuclei
Do we do proton structure functions? We do deuteron structure functions, hope to extract neutron
What physics do we learn from the elementary hyperon photoproduction? Missing resonances?
Give examples of N* experiments
I only have time to emphasize what I think is of interest for this conference.
N-delta transition, higher resonance region, missing quark model states

## Slide 5

**Notes:**
‘4-pi’ spectrometer
Typically accepts any particle down to few hundred MeV, scattering angles from 8-142 degrees, full range in phi (esp. center of mass system)
Good when low current is needed (photon tagging, polarized targets) or with multiple final state particles with little correlation
Flexible target configuration

## Charged particle angles 8° - 144°

- Neutral particle angles 8° - 70°
- Momentum resolution ~0.5% (charged)
- Angular resolution ~0.5 mr (charged)
- Identification of p, +/-, K+/K-, e-/e+

## Slide 7

**Notes:**
About 8 meters diameter

## Typical Run Conditions

- Luminosity of 1034 cm-2s-1 (LH2 target)
- 106 hadronic interactions/second
- Up to 4000 Hz event rate
- Trigger: single electron
- Data transfer rate: up to 20 MByte/s         (~ 1 TByte/day)
- Acquire 10 – 30 billion triggers/year

## Physics of Excited NucleonsN* program

- Resonance transition form factors
-  N- transition
-  Second resonance region (e.g. S11)
-  N- axial form factor
- Quark model ‘missing resonances’
-  Can find them in unexplored decay channels?
-  Models have correct degrees of freedom?

**Notes:**
Symmetric quark model vs quark-diquark model?

## Inclusive scattering in the resonance region

## CLAS: ep     eX, E = 4 GeV

- Q2 (GeV2)

- W (GeV)

**N(940)**

******(1232)**

**N(1520)**

**N(1680)**

## CLAS: ep        epX, E = 4 GeV

******o**

****

****

- W(GeV)

- Missing Mass (GeV)

## ep     eX, E = 4 GeV 

- ep     eX, E = 4 GeV

**Inclusive**

- 2 hadrons

- 2 hadrons

- 2 hadrons

- 3 hadrons

- 4 hadrons

## 

- cos(*)

## N- transition amplitudes

- N- transition amplitudes

## Quark/Hadron Propagation through Nuclei

- Space-time properties of hadronization
- Mass, size, pT, , z, Q2, and flavor dependences of hadron formation lengths
- Gluon emission
- Transverse momentum broadening
- Quark-gluon correlations
- Quark energy loss
- 6 GeV experiment coming in June 2003
*New collaborators welcome*
- 11 GeV experiment (in 2010-2012?)

**Notes:**
Gluon emission as a fundamental process, and its role in hadronization.

## Space-time Picture of Hadronization

## Nuclear Quark/Hadron Propagation Experimental Method

- Use a range of targets, light to heavy
- 1H, 2H, 14N, 56Fe, 84Kr, 197Au
- DIS kinematics + measure hadrons
- Single electron trigger
- Nuclear medium modifies fragmentation functions and pT distributions
- 6 GeV beam:   Q2 ≤ 4 GeV2,  ≤ 5 GeV
- 12 GeV beam: Q2 ≤ 9 GeV2,  ≤ 9 GeV
- Measure , ’, p,

## Recent Data from HERMES at HERA

- Data: Eur. Phys. J. C20 (2001) 479.
- Theory: nucl-th/9607036 for gluon bremsstrahlung model,
- Phys. Rev. Lett. 89 (2002) for twist-4 pQCD model.

## Anticipated CLAS Data at 6 GeV

## Kinematic Coverage, 12 GeV

##  Neutral particle detection for fragmentation events at 11 GeV (LEPTO simulation, no vertex cut)

-  Neutral particle detection for fragmentation events at 11 GeV (LEPTO simulation, no vertex cut)

## Arie Bodek, Rochester
Jorge Morfin, FNAL
Ingo Schienbein, DESY
Jan Sobczyk, U. Wroclaw
Makoto Sakuda, KEK
Emmanuel Paschos, U. Dortmund
Shri Singh, Aligargh Moslem U.

- Interested Collaborators

- Will Brooks, Jlab
- Maurik Holtrop, UNH
- David Ireland, Glasgow
- Mauro Taiuti, INFN
- Larry Weinstein, ODU
- Steve Wood, Jlab
- Laird Kramer, FIU
-  ...

- Arie Bodek, Rochester
- Jorge Morfin, FNAL
- Ingo Schienbein, DESY
- Jan Sobczyk, U. Wroclaw
- Makoto Sakuda, KEK
- Emmanuel Paschos, U. Dortmund
- Shri Singh, Aligargh Moslem U.

**Notes:**
Much of the data you’re interested in is under analysis.
How do they take advantage of CLAS data – amplitude level, parameterization, etc?

## Conclusion

- CLAS has taken a huge volume of new data including multi-hadron final states
- N* and nuclear data likely to be of interest to neutrino community
- Collaborative connection likely to be most fruitful – many potential opportunities for collaboration

**Notes:**
Much of the data you’re interested in is under analysis.
How do they take advantage of CLAS data – amplitude level, parameterization, etc?

## Hadrons accessible for formation length studies

- CLAS at 11 GeV