ransverse target spin asymmetries in exclusive ρ muoproduction MENU 3 Rome Sep 3 - Oct 4 COMPSS ransverse target spin asymmetries in exclusive ρ muoproduction
COMPSS experiment 4 physicists 8 institutions ransverse target spin asymmetries in exclusive ρ muoproduction
COMPSS experiment ECL ECL SM SM 5m µ + 6 GeV beam from CERN SPS ransversely polarized solid state target ransverse target spin asymmetries in exclusive ρ muoproduction
COMPSS experiment ECL ECL SM SM 5m dilution refrigerator ( 6mK superconducting solenoid (.5 µ + 6 GeV beam from CERN SPS ransversely polarized solid state target dipole magnet (.5 ransverse target spin asymmetries in exclusive ρ muoproduction
Hard exclusive ρ production " transversely polarized target transversely polarized target + α em y 8π 3 ε x B x B Q # dσ dx B dq dφ dψ = σ ++ ++ + σ ++ + εσ ++ ε cos(φre σ++ + p ε( + ε cos φ Re (σ ++ + + σ + P p l ε( ε sin φ Im (σ ++ + + σ + " S L ε sin(φ Im σ + ++ + p # ε( + ε sin φ Im (σ ++ + σ + + S L P l " p ε S " longitudinally polarized beam σ ++ ++ σ ++ p # ε( ε cos φ Re (σ ++ + σ + sin(φ φ S Im (σ ++ + + εσ+ + ε sin(φ + φ S Im σ + + + ε sin(3φ φ S Im σ + + + p ε( + ε sin φ S Im σ + + + p ε( + ε sin(φ φ S Im σ + + " p + S P l ε cos(φ φ S Re σ ++ + p ε( ε cos φ S Re σ + + ɛ = virtual photon polarization parameter p # ε( ε cos(φ φ S Re σ + σmn ij = spin dependent photoabsorption cross sections, + Diehl & Sapeta Eur.Phys.J.C 4 (5 ransverse target spin asymmetries in exclusive ρ muoproduction interference terms m,n = virtual-photon helicity i,j = target nucleon helicity #
Hard exclusive ρ production Factorisation valid for σ L Leading twist term σ + sensitive to sin(φ φs Im (σ+ U = ++ + ε σ + σ Im dσ+ dt Im (E H E & H are convolution integrals of hard scattering kernels and the ρ distribution amplitude with GPDs E & H where: E ρ = ( 3 E u + 3 E d + 3 4 E g Constrain GPD E v S dditional asymmetries contain higher twist terms k S q z k ' y x ransverse target spin asymmetries in exclusive ρ muoproduction
Exclusive ρ production at COMPSS ll measurements done with µ + 6 GeV beam with polarization P B 8% and a transversely polarized target 6 LiD target (polarized deuterons 3&4 Dilution factor f.45 Polarization P 5% NH 3 target (polarized protons 7& Dilution factor f.5 Polarization P 8% events/.6 cm events/.6 cm 5 5 5 5 - -5 [cm] COMPSS 3 4 deuteron z V COMPSS 7& proton -5 5 [cm] z V change of polarization weekly ransverse target spin asymmetries in exclusive ρ muoproduction
events/. GeV Exclusive ρ production - event selection 3 µ + N µ + N + ρ ρ π + + π COMPSS 7& proton..4.6.8..4 M [GeV π + ] π - Peak at ρ mass.775 GeV ransverse target spin asymmetries in exclusive ρ muoproduction events/. GeV P µ 4 γ µ GPDs COMPSS 7& proton π detected ρ π + - -5 5 5 [GeV] E miss P not detected Signature for exclusivity E miss E miss = (p + q ρ p M p = M X M p M p
Semi-inclusive background estimation LEPO MC (COMPSS tuning. Parameterization of MC: MC weighted with the like sign sample events/.5 GeV 3 COMPSS 7& proton.4 < Q w = Nh+ h + data (E miss + N h h data N h+ h + MC (E miss + N h h MC (E miss (E miss Parameterize the E miss shape of weighted MC Binning appropriate for asymmetry extraction (x Bj, Q or p, target cell events/.5 GeV 3 COMPS S 3-4.4 < deuteron Q - -5 5 5 E miss [GeV] - -5 5 5 E miss [GeV] ransverse target spin asymmetries in exclusive ρ muoproduction
Semi-inclusive background estimation LEPO MC (COMPSS tuning. Fit to data: Normalize MC E miss shape to data by performing a two component signal (gauss + background fit φ, φ S distribution for 7 < E miss < GeV scaled with the number of background events and subtracted from φ, φ S distribution in signal range.5 < E miss <.5 GeV symmetry extraction with corrected φ, φ S distribution otal amout of SIDIS background: 8% ( 6 LiD, % (NH 3 ransverse target spin asymmetries in exclusive ρ muoproduction events/.5 GeV events/.5 GeV 3 3 COMPS S 3-4.4 < deuteron Q COMPSS 7& proton.4 < Q - -5 5 5 E miss [GeV] - -5 5 5 E miss [GeV]
events/.9 (GeV Exclusive ρ production - kinematical distributions 5 3 protons COMPSS 7& proton 4 Q.5(GeV 3 4 5 6 7 8 9 Q [(GeV ] events 3 COMPSS 7& proton x Bj.4-3 - - x Bj events/. (GeV 5 p.8(gev 4 3 COMPSS 7& proton..4.6.8. p [(GeV ] deuterons events/.9 (GeV COMPSS 3 4 deuteron 4 3 Q.99(GeV 3 4 5 6 7 8 9 Q [(GeV ] events 3 x Bj.3 COMPSS 3 4 deuteron -3 - - x Bj events/. (GeV 4 3 COMPSS 3 4 deuteron p.3(gev..4.6.8. p [(GeV ] ransverse target spin asymmetries in exclusive ρ muoproduction
symmetry,l - NH 3 target (7& as a function of x Bj sin (φ φ S. COMPSS proton sin (φ + φ S.. COMPSS proton. sin sin ( (φ φ + φ S U U.. COMPSS proton. sin sin ( (3 (φ φ + φ S U.. COMPSS proton............5. x Bj.5 4. x Bj..5.4 4. x p Bj..5.4 4. x p Bj sin φ S. COMPSS proton cos (φ sin φ S S L. COMPSS proton.5 cos cos ( (φ φ sin φ S S L L. COMPSS proton.5 cos cos ( (φ φ cos φ S S L L L COMPSS proton.5..5. x Bj.5. symmetry extraction using a D binned maximum likelihood fit after subtracting the SIDIS background.5 4. x Bj ransverse target spin asymmetries in exclusive ρ muoproduction.5...5.4 4. x p Bj.5..5.4 4. x p Bj
symmetry,l - NH 3 target (7& as a function of Q sin (φ + φ S.. COMPSS proton. sin sin ( (φ φ + φ S U U.. COMPSS proton. sin sin ( (3 (φ φ + φ S U.. COMPSS proton. sin ( (3 φ φ S.. COMPSS proton..............5 4. x Bj..5.4 4. x p Bj..5.4 4. x p Bj..4 4 p cos (φ sin φ S S L. COMPSS proton.5 cos cos ( (φ φ sin φ S S L L. COMPSS proton.5 cos cos ( (φ φ cos φ S S L L L COMPSS proton.5 cos ( φ cos φ S S L L COMPSS proton.5.5..5..5.5.5 4. x Bj..5.4 4. x p Bj..5.4 4. x p Bj..4 4 p ransverse target spin asymmetries in exclusive ρ muoproduction
symmetry,l - NH 3 target (7& as a function of p sin sin ( (φ φ + φ S U U.. COMPSS proton. sin sin ( (3 (φ φ + φ S U.. COMPSS proton. sin ( (3 φ φ S.. COMPSS proton. sin (3 φ φ S.. COMPSS proton.............5.4 4. x p Bj..5.4 4. x p Bj..4 4 p..4 p (GeV cos cos ( (φ φ sin φ S S L L. COMPSS proton.5 cos cos ( (φ φ cos φ S S L L L COMPSS proton.5 cos ( φ cos φ S S L L COMPSS proton.5 cos φ S L.5 COMPSS proton.5..5.5.5..5.4 4. x p Bj..5.4 4. x p Bj..4 4 p..4 p (GeV ransverse target spin asymmetries in exclusive ρ muoproduction
Mean asymmetries - NH 3 target (7& sin (φ φ S sin (φ + φ S COMPSSproton sin ( φ φ S sin (3 φ φ S sin φ S cos (φ φ S L cos ( φ φ S L cos φ S L.... ransverse target spin asymmetries in exclusive ρ muoproduction
Comparison with a phenomenological GPD-based model phenomenological handbag approach based on k factorisation includes twist-3 meson wave functions Goloskokov & Kroll Eur.Phys.J.C 59 (9 includes contributions from γ L and γ σ νλ µσ = M µ ν,µν M µ ν,σλ sin(φ φs U σ = Im hɛm,+m +,+ + M +,++M ++,++ + i M,++M +,++ i sin(φs U σ = Im hm,++m +,+ M +,++M,+ i sin(φ φs U σ = Im hm +,++M,+ i cos(φs L σ = Re hm,++m +,+ M +,++M,+ ransverse target spin asymmetries in exclusive ρ muoproduction M δγ,βα = helicity amplitudes α = initial-state proton helicity β = virtual-photon helicity γ = final-state proton helicity δ = meson helicity
Comparison with a phenomenological GPD-based model Up to now mainly used to describe DVCS and HEMP: chiral-even GPDs γ L ρ L M +,+ H; M,+ E dominant γ ρ M ++,++ H; M +,++ E suppressed Recently introduced: chiral-odd (transverse GPDs γ ρ L M,++ H ; M +,++ E = H + E γl ρ, γ ρ known to be suppressed, neglected in the model ransverse target spin asymmetries in exclusive ρ muoproduction
symmetry,p - NH 3 target (7& sin (φ φ S sin (φ + φ S sin ( φ φ S sin (3 φ φ S sin φ S U..5.5.......5.5.......5.5..5..5. x Bj.5. 5 5 4 Q..5 (GeV.5...4 5 5..4 p (GeV COMPSS proton Blue line: Model from Goloskokov and Kroll Predictions for COMPSS kinematic W = 8. GeV, p =. (GeV, Q =. (GeV ransverse target spin asymmetries in exclusive ρ muoproduction
symmetry L,p - NH 3 target (7& cos (φ φ S L.5.5 5 5 COMPSS proton cos ( φ φ S L.5.5 5 5 cos φ S L.5.5 5 5.5. x Bj Q 4 (GeV..4 p (GeV ransverse target spin asymmetries in exclusive ρ muoproduction
symmetry sin(φ φ S U,d sin(φ-φ S U,d.. Goloskokov and Kroll Eur.Phys.J.C59-6 LiD target (3&4 COMPSS 3 4 deuteron -. -. - -..4 x Q [(GeV ] p [(GeV ] Bj Contribution from GPDs E u and E d approx. cancel in exclusive ρ production (different in exclusive ω production ransverse target spin asymmetries in exclusive ρ muoproduction Nucl.Phys. B865 (
Summary Exclusive ρ production in high energy muon scattering off transversely polarized protons and deuterons was studied Results for 5 transverse target single-spin asymmetries,p and 3 transverse target double-spin asymmetries L,p for transversely polarized protons were presented Most of the modulations are small, consistent with zero within experimental uncertainties = -.9 ±.8 ±.3 evidence for existence of chiral-odd GPD H sin(φ S U,p ransverse target spin asymmetries in exclusive ρ muoproduction