# Presentation: 347577

## Rosenbluth Separation of electropion production cross-section from Hydrogen and Carbon

- Xin Qian
- Duke University, Durham, NC, USA
- On the behalf of Jefferson Laboratory E01-107 collaboration

-  Introduction
-  Overview of E01-107
-  Preliminary results
-  Summary

## Motivation of E01-107

- Search for Color-Transparency
**Colour Transparency**** is a phenomenon predicted by QCD in which hadrons produced at large momentum transfer can pass through nuclear matter with little or no interaction**

- qq or qqq that have small transverse size are preferentially selected at large Q2 **(Quantum mechanics)**
- The hadron can propagate out of the nucleus before returning to its equilibrium size **(Relativity)**
- Reduced interaction, PLC ∝ (rPLC)2**    **

## Motivation of Rosenbluth Separation

-  Measuring Nuclear Transparency
-  Nuclear Transparency is defined by :
-  Expected Yield can be calculated used realistic nucleon momentum distributions _**under quasi-free assumption**_.
-  Quasi-free assumption can be verified by carrying out Rosenbluth separation.

- RT =

- Kinematics

- Electro pion five-fold DXs can be written as:
-  Γ: virtual photon flux.
- Photo pion DXs can be decomposed by virtual photon polarization:

- ε:  virtual photon polarization

- In parallel kinematics (θπ= 0)

## Rosenbluth Separation

- By performing experiment at two values of virtual photon polarization, we can extract longitudinal and transverse electro-pion production DXs:

## Overview of E01-107

**Experiment ran at Jefferson Lab in Hall C in 2004**
**Standard Hall C equipment was used**

**Overview of E01-107**

**Electron beam energy**
**  ****(4.0 to 5.8 GeV)**
**Electron in the SOS**
**  ****(0.73 to 1.73 GeV/c)**
**Pion in the HMS **
**  ****(2.1 to 4.4 GeV/c)**

**(****e,e’ ****π****+****)**

## Kinematics

- 					**Q****2****	****	****W****	****	****-t****	****E****beam****	****θ****hms****	****P****hms****	****	****θ****sos****	****P****sos****	****	********	**x**BJ**
**	****	****	****	****	****(GeV****2****)****	****(GeV)****	****(GeV****2****)****	****(GeV)****	****(deg) (GeV/c) (deg)****	****(GeV/c)**
**	****	****	****	****	****1.1****	****	****2.3****	****	****0.05****	****4.0****	****10.6****	****2.8****	****	****27.8****	****-1.2****	****	****0.50****	****0.21**
**	****	****	****	****	****2.15****	****	****2.2****	****	****0.16****	****5.0****	****13.4****	****3.2****	****	****28.9****	****-1.7 ****	****0.56****	****0.35**
**	****	****	****	****	****3.0****	****	****2.1****	****	****0.29****	****5.0****	****12.7****	****3.4****	****	****37.8****	****-1.4 ****	****0.45****	****0.44**
**	****	****	****	****	****4.0****	****	****2.2****	****	****0.40****	****5.8****	****11.5****	****4.1****	****	****40.4****	****-1.5 ****	****0.39****	****0.50**
**	****	****	****	****	****4.8****	****	****2.2****	****	****0.52****	****5.8****	****10.6****	****4.4****	****	****52.7****	****-1.1 ****	****0.26****	****0.54**
**    ****L-T separation****	****2.15****	****	****2.2****	****	****0.16****	****4.0****	****10.6****	****3.2****	****	****50.8****	****-0.7 ****	****0.27 ****	****0.35**
**    ****L-T separation****	****4.0****	****	****2.1****	****	****0.44****	****5.0****	****10.6****	****3.9****	****	****55.9****	****-0.9 ****	****0.25****	****0.52**
**W vs k****π**** test point****	****2.15****	****	****1.7****	****	****0.37****	****4.0****	****20.0****	****2.1****	****	****32.3****	****-1.7 ****	****0.63****	****0.50**

**LH****2****, LD****2****, ****12****C, ****63****Cu and ****197****Au targets at each kinematic setting**

**Kinematics**

**( k****π********= momentum of the virtual pion)******

## Particle Identification (PID)

**Electron arm (SOS) at 1.4 GeV**
**Cerenkov effic = 99.4%**

- π+

**e****-**

**π****+**

**K****+**

**p**

**Pion arm (HMS) at 3.2 GeV**
**Cerenkov effic = 98.5%**

## Preliminary results at Q2 =2.15 GeV2

- Preliminary results at Q2 =2.15 GeV2

- Longitudinal

- statistical uncertainties only

- Carbon points have be shifted by 0.01 for clarity

## Preliminary results at Q2 =2.15 GeV2

- Longitudinal

- statistical uncertainties only

- Carbon points have be shifted by 0.01 for clarity

**Transverse**

## Preliminary results at Q2 =4.0 GeV2

- Preliminary results at Q2 =4.0 GeV2

**Longitudinal**

- statistical uncertainties only

- Carbon points have be shifted by 0.01 for clarity

- Preliminary results at Q2 =4.0 GeV2

**Transverse**

## Preliminary results on ratio

- statistical uncertainties only

- Carbon points have be shifted by 0.1 for clarity

## Summary

**E01-107 will provide the FIRST nuclear transparency data from (e,e****π****+****) reactions.**
**Rosenbluth separation has been carried out for the first time with (e,e’****π****+****) on Carbon at Q****2**** = 2.15 and 4.0 GeV****2**** and Hydrogen at Q****2**** = 4.0 GeV****2****.**
**Preliminary results are in good agreement with quasi-free assumptions for Q****2**** = 2.15 and 4.0 GeV****2****.**
**Rosenbluth separation for Copper and Gold targets will be carried out in the near future.**

## E01-107 collaboration

**Y. Liang**
*American University, Washington, DC*
**J. Arrington, L. El Fassi, X. Zheng**
*Argonne National Laboratory, Argonne, IL*
**T. Mertens, D. Rohe**
*Basel Univeristy, Basel, Switzerland*
**R. Monson**
*Central Michigan University, Mount Pleasant, MI*
**C. Perdrisat**
*College of William and Mary, Williamsburg, VA*
**D. Dutta (Spokesperson)****, H. Gao, K. Kramer, ****X. Qian**
*Duke University, Durham, NC*
**W. Boeglin, P. Markowitz**
*Florida International University, Miami, FL*
**M. E. Christy, C. E. Keppel, S. Malace, E. Segbefia, L. Tang, L. Yuan**
*Hampton University, Hampton, VA*
**J. Ferrer, G. Niculescu, I. Niculescu**
*James Madison University, Harrisonburg, VA*
**P. Bosted, A. Bruell, R. Carlini, E. Chudakov, V. Dharmawardane,**
**R.Ent (Spokesperson)****, H. Fenker. D. Gaskell, M. K. Jones, A. Lung, **
**D. G. Meekins, G. Smith, W. F. Vulcan, S. A. Wood**
*Jefferson Laboratory, Newport News, VA*
**B. Clasie****, J. Seely**
*Massachusetts Institute of Technology, Cambridge, MA*
**V. Punjabi**
*Norfolk State University, Norfolk, VA*

**A. K. Opper**
*Ohio University, Athens, OH*
**A. Villano**
*Rensselaer Polytechnic Institute, Troy, NY*
**F. Benmokhtar**
*Rutgers University, Piscataway, NJ and*
*Universite' des Sciences et de la Technologie, Algiers, Algeria*
**Y. Okayasu, A. Matsumura, T. Miyoshi, M. Sumihama**
*Tohoku University, Sendai, Japan*
**K. Garrow (Spokesperson)**
*TRIUMF, Vancouver, British Columbia, Canada*
**A. Daniel, N. Kalantarians, Y. Li, V. Rodriguez**
*University of Houston, Houston, TX*
**A. W. Rauf**
*University of Manitoba, Winnipeg, Manitoba, Canada*
**T. Horn**
*University of Maryland, College Park, MD*
**G. M. Huber**
*University of Regina, Regina, Saskatchewan, Canada*
**D. Day, N. Fomin**
*University of Virginia, Charlottesville, VA*
**M. Dalton, C. Gray**
*University of the Witwatersrand, Johannesburg, South Africa*
**R. Asaturyan, H. Mkrtchyan, T. Navasardyan, V. Tadevosyan**
*Yervan Physics Institute, Yervan, Armenia*

## Systematic uncertainty estimation

- SOS Cerenkov Efficiency  0.5 (pt to pt)
- HMS Cerenkov Efficiency  1.0 (pt to pt)
- Charge                    1.0 (Normalization)
- Target thickness      1.0 (Normalization)
- HMS and SOS trigger efficiency   2.0 (Pt to Pt)
- Computer dead time              0.1
- Coincidence blocking             0.1
- Tracking efficiency                  0.5
- Pion absorption                       3.0 (normalization)
- Pion absorption (between target)  1.0
- Kinematics Ebeam                  0.5
- Kinematics sstheta                  0.5

- Kinematics spcentral                0.5
- Kinematics  hstheta                 0.3
- Kinematics    hpcentral            0.3
- Pion decay                        2.0 (Pt to Pt)
- Collimator punch-through   3.0 (Pt to Pt)
- Radiative correction          2.5 (Pt to Pt)
- Acceptance                      5.0 (Pt to Pt)
- Dummy subtraction           0.2 (Pt to Pt)
- HMS electronic dead time        0.4
- SOS electronic dead time         0.3
- Target boiling          1.0 (Normalization)
- Carbon spectral function  1.0 (Normalization)
- Model dependence            10.0

- Hydrogen DXs:  7.99 %

- Carbon DXs:  12.84 %

- The estimated systematic uncertainties at this stage are 7% pt-pt, 3.6% normalization
- and 10% model dependent. We expect to improve several of these uncertainties.