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This study presents an approach to determine non-perturbative corrections for event shape variables in Deep Inelastic Scattering (DIS). It separates out the soft QCD effects and provides correction factors for any infrared safe event shape variable. The analysis compares previous event shape variables and introduces new variables in DIS, showing good agreement between different analyses.
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Event Shape Variables in DIS Update A. Everett, A. Savin University of Wisconsin S. Hanlon, I. Skillicorn, A. Doyle University of Glasgow June 18, 2003
Used to determine the hadronization corrections Approach to Non-Perturbative Calculations • pQCD prediction → measured distribution • Correction factors for non-perturbative (soft) QCD effects • Separates out non-perturbative corrections for any infrared safe event shape variable, F: • Power Correction • independent of any fragmentation assumptions • “non-perturbative parameter” – (Dokshitzer, Webber, Phys. Lett. B 352(1995)451)
Event Shape Variables • Previous event shape variables not well correlated with • Study: • New Variables in DIS* • Kout • Azimuthal Correlation (following slides) *hep-ph/0111157 and hep-ph/0207072 • Previous Variables from previous event shape analysis (differential distributions)
Kinematic Bins • Mean of Event Shape Variables has a Q dependence. • Analysis done in bins of x and Q2.
Breit Frame Cuts Multiplicitycurrent ≥ 2 Ecurrent/Q > 0.25 For KOut, Acorr: At least 2 Jets in Breit Frame: E1,T > 6 GeV E2,T > 5 GeV PT,i,Lab 2 GeV Zufo Cuts Pt>0.15 GeV |η|<2.2 good acceptance region Selection Cuts Q2DA 80 GeV2 yJB > 0.04 yel < 0.95 Vertex with |z| < 40 cm |x| > 14 cm or |y| > 14 cm 38 < E-pZ < 65 GeV 44 < E-pZ for forward electron Good positron Sinistra Probability > 0.9 Ee’> 10 GeV Event Selection
C Parameter • Compare previous event shape variables between two analyses • Some small disagreement for uncorrected monte carlo at the detector level, perfect agreement at the “truth” level Uncorrected Ariadne at detector level Everett • Hanlon ┌ • Collimated: values tend towards minimum • Isotropic: values tend towards maximum
Invariant Jet Mass Everett • Hanlon ┌ Analyses Comparison Detector level Ariadne • Collimated: values tend towards minimum • Isotropic: values tend towards maximum
axis TT axis TZ axis TM axis Tm axis Energy Flow and Dijets: TT Everett • Hanlon ┌ Detector Level Ariadne • Collimated: values tend towards maximum • Isotropic: values tend towards minimum
axis TT axis TZ axis TM axis Tm axis Energy Flow and Dijets: T Detector Level Ariadne Everett • Hanlon ┌ • Collimated: values tend towards maximum • Isotropic: values tend towards minimum
BT 0 Thrust Axis BT 0.5 Broadening: BT • Broadening of particles in transverse momentum wrt. thrust axis Everett • Hanlon ┌ Detector Level Ariadne • Collimated: values tend towards minimum • Isotropic: values tend towards maximum
B 0 Photon Axis B 0.5 Broadening: B • Broadening of particles in transverse momentum wrt. photon axis Detector Level Ariadne Everett • Hanlon ┌ • Collimated: values tend towards minimum • Isotropic: values tend towards maximum
Out-of-plane Momentum • Examine New Variable: • Energy flow out of event plane defined by proton direction and thrust major axis • Sensitive to perturbative &non-perturbative contributions
Prediction by Banfi, Marchesini, Smye, Zanderighi (hep-ph/0111157) Plot ln(Kout/Q) since powers of ln(Kout/Q) used in resummation. Theoretical Prediction for Kout xB = 0.1 Q = 30 GeV y- = 0.1 < ykt < 2.5
Kout/Q Comparison • Good agreement between Data and Ariadne ’98 – ’00 Data (Everett) • Ariadne ┌ Kout/Q 0.0024 < x < 0.010 320 < Q2 < 640 GeV2
h h’ pth’ pth Azimuthal Correlation • Examine New Variable: • Momentum weighted function of the azimuthal angle around the photon-proton axis in the Breit frame between pairs (h,h’) of hadrons.
ACorr Comparison • Good initial agreement between Data and Ariadne ’98 – ’00 Data (Everett) • Ariadne ┌ Add Data vs MC Plots Here 0 /2 0.0024 < x < 0.6 80 < Q2 < 10240 GeV2
Summary • Good agreement between Glasgow and Wisconsin Analyses • Complementary analyses • Agreement of differential distributions • Early look at new variables • Acceptable level of agreement • Plan : • Systematic studies • Different monte carlo models • Extract S,