Status Report of Single Pion Electroproduction in the Deep Inelastic Scattering Region Kijun Park Univ. of South Carolina Kijun Park Univ. of South Carolina and CLAS Collaboration and CLAS Collaboration Deep Process Working Group May. 30, 2008

Physics Motivation t-channel scaling behavior at large angle Non-pertubative transition between pion and baryon in backward angle Deep Process Working Group May.30, 2008 K. Park Generalized scaling law appears at above resonance region and large angle( θ=90 o ) Investigation of Transition Distribution Amplitude u-channel scaling at backward angle Generalized scaling law appears at large angle related to isospin (3/2 or 1/2) L.Y. Zhu, PRL 91, (2003) J.P. Lansberg, B. Pire, PRD75, (2007) J. Phys. G : Nucl. Phys. Vol4 No 11, (1978)

Physics Motivation t-channel scaling behavior at large angle Non-pertubative transition between pion and baryon in backward angle Generalized scaling law appears at above resonance region and large angle( θ=90 o ) Investigation of Transition Distribution Amplitude u-channel scaling at backward angle Generalized scaling law appears at large angle related to isospin (3/2 or 1/2) L.Y. Zhu, PRL 91, (2003) J.P. Lansberg, B. Pire, PRD75, (2007) J. Phys. G : Nucl. Phys. Vol4 No 11, (1978) Deep Process Working Group May.30, 2008 K. Park

VariableUnitRange# BinWidth Q2 GeV ~ ~ Xbj0.16 ~ t GeV ~ ~ ~ Kinematical Coverage E1-6 data Deep Process Working Group May.30, 2008 K. Park

Cross section in the t- channel

Particle Identification Acceptance Calculation Radiative Correction Background Subtraction Kinematical Correction Analysis Steps Extract CRS in extended t-range Systematic Study Acceptance cross check after generating more backward angle simulated events Investigated at low -t region but ongoing at high -t Deep Process Working Group May.30, 2008 K. Park

Analysis Steps for 9 xbj bins CRS with low t ACC CRS with high t ACC Preliminary Deep Process Working Group May.30, 2008 K. Park

Analysis Steps for 9 xbj bins CRS with low t ACC CRS with high t ACC Preliminary Deep Process Working Group May.30, 2008 K. Park

No.SourceContents[%]DescriptionLink [1]eletron PID Sampling Fraction cut on EC4.0%EC tot =0.29p e +/ √(p e )+/-0.01 The PID is important as it turned out in the resonance study. [2]Fiducial cut (e) Cross section dependence of various electron fiducial volumn 10% reduced in its width [C 4 ] 2.5% Δφ e = C 4 (sin(θ-θ 0 )) expon expon = C 3 (p e B max /B cur ) C 3 θ 0 = C 1 +C 2 /p scale Since, we used the same fiducial function from resonance study, we expected similar sys. uncertainties as we got. [3]π PID particle identification for pion on TOF mass cut (3σ to3.5σ) 1.73%different resolution of TOF massphi-dependent [4]Fiducial cut (π) Cross section dependence of various π fiducial volumn 10% reduced in its width [A sec,θ ] 3.5% Function : Δφ π +/- = A sec,θ (Exp(B sec,θ *θ(p π ))+C sec,θ Since, we used the same fiducial function from resonance study, we expected similar sys. uncertainties as we got. [5] Missing mass (neutron) cut missing mass cut based on width (2.5σ to 3.5σ) Ref. 25MeV of MMx resol. 1.04% simulation event has negligible amount of event change under the condition between 2.5σ and 3.5σ Q2-dependence t-dependence X-dependence [6]vertex cut particel vertex cut (reduced 5% of original value) 1.57% From -8.0cm < v z < -0.8cm to -7.82cm < v z <-0.98cm phi-dependent [7]Target target density/length< 1.% measurement of fluctuation (target density and length) uncertainty comes from measurement of taget length/density in term of run time [8]Radiative Radiative correction factor based on different models(EG) 0.6% compare with ExcluRad (resonance, extrapolation) or other model for EG Model dependent sys. error from ExcluRad < 0.5% comparison [9] Background Subtraction various fit function range to describe the background 0.15% mmx= GeV to Gaussian to polyno.(3) Q2-dependence t-dependence X-dependence [*]Total overall6.51% Analysis Steps Systematic Uncertainties [%] from the sources Deep Process Working Group May.30, 2008 K. Park

Resonance contribution in the u-channel

Analysis Steps Communications with B. Pire [1] Most of papers are old and based on photo-PROD [2] It is much valuable to search for difference when Q2 grows from 0 to a few GeV [3] We will be able to see for some channels a definite change on the behavior of the cross section(Q 2, u) [4] It would be interesting to see a 1/Q 8 law appearing for W min large enough, which might be interpreted as a first manifestation of scaling in the case of backward electroproduction Deep Process Working Group May.30, 2008 K. Park

Analysis Steps Fit function Extracting power factor : B Preliminary Slope of fit : B Deep Process Working Group May.30, 2008 K. Park

Analysis Steps Fit function in log scale Extracting power factor : B Preliminary Slope of fit : B Deep Process Working Group May.30, 2008 K. Park

Preliminary Analysis Steps Slope parameter vs. -t Horizontal red line = -8 “Indeed a power-like behavior is much more in the spirit of QCD factorization !” -B. pire Deep Process Working Group May.30, 2008 K. Park

Analysis Steps “We would like to stress that the Q² behavior (1/Q 8 ) of dσ/du (or equivalently of d σ/ d Ω as we discussed in our paper ) is a signature of scaling ONLY IF the SKEWEDNESS variable ξ is fixed, which means (at small Δ T 2 ) W²/Q² is fixed. Since we have W² +t+u = -Q² +2M² +mπ², at small mπ² this means at fixed (2M²-t-u)/Q². ” -B. pire “However, ….” Deep Process Working Group May.30, 2008 K. Park

Analysis Steps Cross section vs. Q 2 in different u- bin at fixed R=(2M²-t-u)/Q² “Doesn’t make sense to B. Pire !” “It seems to make sense for R’(=2M²-t-u) fixed” Deep Process Working Group May.30, 2008 K. Park

Analysis Steps Cross section vs. Q 2 in different u- bin at fixed R=(2M²-t-u)/Q² Deep Process Working Group May.30, 2008 K. Park No Scaling of Q -8 observed !

Analysis Steps “if R’(=2M²-t-u) is fixed ??” Preliminary Deep Process Working Group May.30, 2008 K. Park

Analysis Steps “if R’(=2M²-t-u) is fixed ??” Preliminary Deep Process Working Group May.30, 2008 K. Park

Analysis Steps “if R’(=2M²-t-u) is fixed ??” Preliminary Deep Process Working Group May.30, 2008 K. Park

Analysis Steps “if R’(=2M²-t-u) is fixed ??” Preliminary Deep Process Working Group May.30, 2008 K. Park

Transition Distribution Amplitude

Kinematical variables : Backward angle constraint Deep Process Working Group May.30, 2008 K. Park

1.Clearly s-channel removed 2.Automatically, accessible small -u large –t 3.No (s-) resonance access (= no event below 2Gev of W) Quick view Deep Process Working Group May.30, 2008 K. Park

Analysis Steps Communications with theory people More comprehensible analysis approach [1]π-mass correction for lowerξin DGLAP region [2] new model approach in this region by Barbara Pasquiri [3] Detail discussion had been made in “Backward Electroproduction of Mesons” at Ecole Polytech. - Nov.2007 Deep Process Working Group May.30, 2008 K. Park

Different Cuts Independent analysis with u,t and Q 2 Cross sections Preliminary Deep Process Working Group May.30, 2008 K. Park

Different Cuts Independent analysis with u,t and Q 2 Cross sections No Scaling of Q -8 observed ! Preliminary Deep Process Working Group May.30, 2008 K. Park

We measured the differential cross section with extended –t region Systematic uncertainties has been studied at low –t region and ongoing at high –t region. We looked at the backward angle pion electroproduction in the u- channel by extracting the cross section (dσ/du) We tried to see 1/Q 8 law appearing for large W(>2GeV), which might be interpreted as a first manifestation of scaling in backward electroproduction and linked to TDA. However, … More careful studies needed in both theoretical calculation (realistic) and experimental analysis. We measured the differential cross section with extended –t region Systematic uncertainties has been studied at low –t region and ongoing at high –t region. We looked at the backward angle pion electroproduction in the u- channel by extracting the cross section (dσ/du) We tried to see 1/Q 8 law appearing for large W(>2GeV), which might be interpreted as a first manifestation of scaling in backward electroproduction and linked to TDA. However, … More careful studies needed in both theoretical calculation (realistic) and experimental analysis. Summary and future plans Deep Process Working Group May.30, 2008 K. Park

BACKUP SLIDES

GPD can not describe Non-perturbative part Baryon →π transition Deep Process Working Group May.30, 2008 K. Park J.P. Lansberg, B. Pire, PRD75, (2007) Pert.