XC Congresso Nazionale Brescia, Settembre 2004

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1 Beam-Spin zimuthal symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 Eduard vetisyan eduard.avetisyan@desy.de (Yerevan Physics Institute / INFN Frascati) E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 1/1

2 HER setup: Longitudinal Polarimeter Spin Rotator Spin Rotator Spin Rotator Spin Rotator Spin Rotator Transverse Polarimeter HER-e beam self-polarized due to emission of synchrotron radiation Sokolov-Ternov effect < P beam > 55% e p Spin Rotator Beam Direction E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 2/1

3 HERMES Spectrometer: m 2 FRONT MUON HODO FIELD CLMPS TRIGGER HODOSCOPE H1 DRIFT CHMBERS 27 mrad PRESHOWER (H2) 17 mrad 1 DRIFT CHMBERS 14 mrad TRGET CELL SILICON DVC FC 1/2 PROP. CHMBERS MC 1-3 MINOSITY MONITOR 27.5 GeV e+ -1 HODOSCOPE H BC 1/2 STEEL PLTE BC 3/4 TRD CLORIMETER 14 mrad -2 RICH 27 mrad IRON WLL 17 mrad MGNET WIDE NGLE MUON HODOSCOPE MUON HODOSCOPES m e + p e e + p e h E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 3/1

4 Semi Inclusive DIS: ep e h k k y x z q p had S φ uli Q 2 = 4EE sin 2 ( θ 2 ) ν = E E Q 2 2mν x = y = ν E = p q p k z = E h ν cosφ = [ q k][ q P h ] q k q P h 2 P σ(φ) = + 1 sin φ + B 1 cos φ + 2 sin 2φ + B 2 cos 2φ... d 3 σ UU dx dy dz dφ = 1 ( d 3 σ + 2 dx dy dz dφ + d 3 σ ) dx dy dz dφ d 3 σ dx dy dz dφ = 1 P + d 3 σ + dx dy dz dφ 1 P d 3 σ dx dy dz dφ E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 4/1

5 DFs and FFs: Factorization σ eheh = f Hq σ eqeq D qh Distribution Fragmentation σ unpol σ UU (1 y + y 2 /2) a,ā e2 axf a 1 (x)d a 1(z) σ pol = {σ UL, σ LL, σ UT, σ, σ LT } Beam Target polarization σ UL S L sin φ (2 y) 1 y M Q a,ā KNOWN! e 2 ax 2 h a L(x)H a 1 (z) σ UT S T (1 y) sin(φ + φ s ) a,ā e 2 axh a 1(x)H a 1 (z) σ λ e sin φ y 1 y M Q a,ā e 2 ax 2 [ e a (x)h a 1 (z) + h a 1 (x)e a (z) ] E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 5/1

6 DFs and FFs: Factorization σ eheh = f Hq σ eqeq D qh Distribution Fragmentation σ unpol σ UU (1 y + y 2 /2) a,ā e2 axf a 1 (x)d a 1(z) σ pol = {σ UL, σ LL, σ UT, σ, σ LT } Beam Target polarization σ UL S L sin φ (2 y) 1 y M Q a,ā KNOWN! e 2 ax 2 h a L(x)H a 1 (z) σ UT S T (1 y) sin(φ + φ s ) a,ā e 2 axh a 1(x)H a 1 (z) σ λ e sin φ y 1 y M Q a,ā e 2 ax 2 [ e a (x)h a 1 (z) + h a 1 (x)e a (z) ] E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 5/1

7 symmetries: = dσ+ dσ dσ + + dσ = dσ dσ UU e(x)h 1 (z) + h 1 (x)e(z) f 1 (x)d 1 (z) Distribution Fragmentation Twist-2 h 1 H1 Twist-3 e E E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 6/1

8 symmetries: = dσ+ dσ dσ + + dσ = dσ dσ UU e(x)h 1 (z) + h 1 (x)e(z) f 1 (x)d 1 (z) Distribution Fragmentation Twist-2 h 1 H1 Twist-3 e E NEWS FROM THEORY! σ λ e sin φ y 1 y M Q a,ā e 2 ax 2 [ xze a (x)h a 1 (z) + h a 1 (x)e a (z)+ + M h M f 1 a (x)g a (z) xz M g a (x)d M 1(z) a h m M zf 1 a (x)h1 a (z) m ] zh a 1 (x)d a M 1(z) h E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 6/1

9 Beam SS at HERMES HERMES PRELIMINRY 1.9% scale uncertainty not corrected for smearing and acceptance symmetry extraction: maximum possible effect from exclusive VM ± = 1 P ± N ± N ± i=1 sin φ z 1-1 x P t (GeV/c) 1 E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 7/1

10 Beam SS at HERMES HERMES PRELIMINRY 1.9% scale uncertainty not corrected for smearing and acceptance symmetry extraction: ± = 1 P ± N ± N ± i=1 sin φ Systematic error from VM e p W 2 Q 2 t estimated from Monte-Carlo. γ e p V z maximum possible effect from exclusive VM 1-1 x P t (GeV/c) 1 E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 7/1

11 Comparison with CLS: HERMES (Preliminary) CLS (E B =4.3 GeV) /f(y) HERMES (Preliminary) CLS (E B =4.3 GeV) z z In leading order (neglecting σ L /σ T ): f(y) = 2(1 y) 1 y + y 2 /2 Strong kinematic suppression factor in HERMES (.7.35 at higher z) roughly constant (f(y).7) in CLS. E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 8/1

12 Comparison with Theory: HERMES Preliminary Quark-diquark model verage kinematics: < P T >=.45GeV < Q 2 >= 2.4GeV z L.Gamberg, D.Hwang, K.Oganessyan, hep-ph/311221, Phys. Lett. B584 (24) 276. Quark-diquark spectator model prediction for at HERMES kinematics. E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 9/1

13 Conclusion: First measurement of beam-spin asymmetry for all pions Independent source of information about H 1 Collins function Possibility to access a set of new DFs and FFs greement with CLS measurement of BS for + (after kinematic range corrections) greement with theoretical model calculation E.vetisyan Beam-Spin symmetries in Pion Electroproduction at HERMES C Congresso Nazionale Brescia, 2-25 Settembre 24 page 1/1