nov. 25-26, 2010 annual meeting of gdr nucleon - k. park · pp j/ @ gsi pp t

Nov. 25-26, 2010 Annual Meeting of GDR Nucleon - K. Park

Pert.

hard part

soft part

Successful factorization

@ Q2 ∞ , t << fixed


Pert. Pert.

hard part

soft part

What about u <<, DVCS ?

Non-pert. Part does not describe the Hadron Hadron transition

Need a Transition DA (TDAs)

???

???


Non-pertubative transition between pion and baryon in backward angle

Investigation of Transition Distribution Amplitude

B. Pire, L. Szymanowski PRD71, 111501 (2005)Pert. Pert.

Amplitude = Correlation between meson → transition

Mesonic TDA

pp @ GSI

e+e- B-factories

Large Q2 would provide hard scale with pert. expansion

pp J/ @ GSI

pp t << @ GSI


Non-pertubative transition between pion and baryon in backward angle

Investigation of Transition Distribution Amplitude

J.P. Lansberg, B. Pire, PRD75,074004 (2007)

GPD can not describe Non-perturbative part Baryon →π transition

Pert. Pert.

Amplitude = Meson almost stay at rest in the target(baryon) rest frame

Pert.Baryonic TDA

e’ n u << , t >> @ CLAS

at 180o @ Hall-C

e’p e’p o @ CLAS

JLAB 12GeV

*p pJ/ @ COMPASS


• The kinematics imposes the exchange of 3 quarks in the u -channel

• Factorization in the generalized Bjorken limit:

• The object factorized from the hard part is a Transition Distribution Amplitude

• Interpretation at the amplitude

Amplitude of probability to find a meson within the proton

Baryonic TDA


2 2

TQ

2W G eV


Kinematical variables Unpol. CRS w/ one-photon exchange approx.


The CLAS Collaboration

Old Dominion University, Norfolk, VA

Rensselaer Polytechnic Institute, Troy, NY

Rice University, Houston, TX

University of Richmond, Richmond, VA

University of Rome Tor Vergata, Italy

University of South Carolina, Columbia, SC

Thomas Jefferson National Accelerator Facility, Newport News, VA

Union College, Schenectady, NY

Virginia Polytechnic Institute, Blacksburg, VA

University of Virginia, Charlottesville, VA

College of William and Mary, Williamsburg, VA

Yerevan Institute of Physics, Yerevan, Armenia

Brazil, Germany, Morocco and Ukraine,

, have individuals or groups involved with CLAS,

but with no formal collaboration at this stage.

Arizona State University, Tempe, AZ

University Bari, Bari, Italy

University of California, Los Angeles, CA

California State University, Dominguez Hills, CA

Carnegie Mellon University, Pittsburgh, PA

Catholic University of America

CEA-Saclay, Gif-sur-Yvette, France

Christopher Newport University, Newport News, VA

University of Connecticut, Storrs, CT

Edinburgh University, Edinburgh, UK

University Ferrara, Ferrara, Italy

Florida International University, Miami, FL

Florida State University, Tallahassee, FL

George Washington University, Washington, DC

University of Glasgow, Glasgow, UK

University of Grenoble, Grenoble, France

Idaho State University, Pocatello, Idaho

INFN, Laboratori Nazionali di Frascati, Frascati, Italy

INFN, Sezione di Genova, Genova, Italy

Institut de Physique Nucléaire, Orsay, France

ITEP, Moscow, Russia

James Madison University, Harrisonburg, VA

Kyungpook University, Daegu, South Korea

University of Massachusetts, Amherst, MA

Moscow State University, Moscow, Russia

University of New Hampshire, Durham, NH

Norfolk State University, Norfolk, VA

Ohio University, Athens, OH


CLAS

Emax

6 GeV

Imax 200 A

Duty Factor 100%

E/E 2.5 10-5

Beam P ~ 85%

Eg(tagged) ~ 0.8-5.5GeV

e-

π+

e-


Kinematical variables Unpol. CRS w/ one-photon exchange approx.


Particle Identification

Acceptance Calculation

Radiative Correction

Background Subtraction

Kinematical Correction

Extract CRS & structure functions

Acceptance cross check after more simulation in backward angle

with Modification of GENEV vs. FSGEN

Bin corrections

Systematic error studies

E1-6 data set was used. E0=5.754GeV, B =3375A, LH2

…….


1. No (s-) resonance

access (= no event

below 2GeV of W)

2. No missing mass cut


1. No (s-) resonance

access (= no event

below 2GeV of W)

2. No missing mass cut

3. Automatically,

accessible small -u

large –t

u

t


Requirement

W>2GeV


Requirement

W>2GeV

cos * <0.0

T2 <0.5GeV 2


Requirement

W>2GeV

cos * <0.0

T2 <0.5GeV 2

TOF mass 3sigma cut


Requirement

W>2GeV

cos * <0.0

T2 <0.5GeV 2

TOF mass 3sigma cut

: 2sigma cut


Blue bullets : _T2 < 0.5GeV2 cut

Red hist. : _T2 < 1.0GeV2 cut

u

t

cos *


Black bullets : exp. Data before

BG subtraction

Red bullets : exp. Data before

BG subtraction

Blue solid lines : nominal MMx

3 cut


Blue bullets : exp. Data after

BG subtraction

Red hist. : GPP + w/o (left) &

with (right) correction

applied MC


1. Two event generators

were tested

2. cos cut was applied on

top of T2 cut


1. Two event generators

were tested

2. cos cut was applied on

top of T2 cut

Nov. 12, 2010 DPWG K. Park

W>2GeV

MMx cut

cos * <0.0

T2 <0.5GeV 2


W>2GeV

T2 <1.0GeV 2

+ GPP+corr.

T2 <0.5GeV 2

MMx cut


Blue square : data with stat. err. only

Red triangle : fit with cos2

Average Chi2 ~ 1.74

except last Q2 bin


σT+εσLσT+εσL


σT+εσLσT+εσL

J.P. Lansberg, B. Pire, PRD75,074004 (2007)

But 0 – calculation for =0.8, =180o


σT+εσLσT+εσL

< 1/2 < 1/2 ~1

- range is about 0.4-0.7


• Hard exclusive process of meson in the backward angle opens a new window in the

understand of hadronic physics in the framework of the collinear-factorization

approach of QCD.

• Measurement of cross sections and asymmetries are crucial to develop a realistic

model for the TDAs.

• Careful study has been performed by communicating with theory group (kinematic

binning, corrections, acceptance(GENEV/FSGEN), cuts, etc.)

• We measured the differential cross sections on backward angle in the kinematic

range of W > 2GeV, high “t” and low “u”.

• We extracted the structure functions from differential cross sections,

TT has a similar amplitude of LT

T+ L is ~2x larger than TT and LT .

Open questions ?


Thank you ! Questions/comments ?


Black bullets : exp. Data before

BG subtraction

Red bullets : exp. Data before

BG subtraction

Blue solid lines : nominal MMx

3sigma cut


W>2GeV

T2 <0.5GeV 2

+ 18 bins of

MMx cut

T2 <0.5GeV 2

+ 9 bins of


W>2GeV

T2 <0.5GeV 2

MMx : +/- 4 cut

MMx : +/- 2 cut


nov. 25-26, 2010 annual meeting of gdr nucleon - k. park · pp j/ @ gsi pp t

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