HERMES status and future running

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1 HERMES status and future running Benedikt Zihlmann University of Gent on behalf of the collaboration DESY PRC Mai 24 p.1/18

2 Access to Transversity Single spin azimuthal asymmetries on a transverse polarized Target ep e πx σ ep eπx = q f N q σ eq eq D q π k k q S φ S Distributionfunction h 1 Fragmentat.- function (Collins) H 1 z y x p had φ A h UT(φ, φ s ) = 1 S T N h (φ, φ s) N h (φ, φ s) N h (φ, φ s) + N h (φ, φ s) uli A Collins UT q e2 q δq(x) H,q 1 (z) q e2 q q(x) Dq 1(z) DESY PRC Mai 24 p.2/18

3 Data on Transversity x 1 3 Integrated DIS HERA Run II (polarized) Number of pol. DIS events Statistics 2:.94 M DIS 3:.5 M DIS 4: 1.3 M DIS TOTAL 2.8 M DIS GOAL 6 M DIS 2 22/ Day of Running DESY PRC Mai 24 p.3/18

4 Very First Results on TRANSVERSITY.5 π + HERMES PRELIMINARY not corrected for smearing and acceptance effects P h /M π weighted 8% scale uncertainty sin(φ+φs) A UT π - Collins angle sin(φ+φs) A UT π Maximum possible effect of exclusive vector mesons x-dependence δq z-dependence FF more data for 2-dim. analysis 6 Million DIS sin(φ+φs) A UT x B z DESY PRC Mai 24 p.4/18

5 Beam spin azimuthal asymmetries Access to Collins e p e πx σ ep eπx = q f N q σ eq eq D q π k k q Distributionfunction e Fragmentat.- function H 1 z y x p had S φ uli A h LU(φ) = 1 S L N h (φ) N h (φ) N h (φ)+ N h (φ) A Collins LU q e2 q e(x) H,q 1 (z) q e2 q q(x) Dq 1(z) DESY PRC Mai 24 p.5/18

6 Beam Spin Asymmetry sinφ A LU e p e e p e π + π - X X HERMES PRELIMINARY 1.9% scale uncertainty not corrected for smearing and acceptance maximum possible effect from exclusive VM sinφ A /f(y) LU e p e π + X HERMES (Preliminary) CLAS (E B =4.3 GeV) sinφ A LU z sinφ A LU e p e π X more results on Deuterium target to come z 1-1 x P t (GeV/c) 1 DESY PRC Mai 24 p.6/18

7 The Hermes Quest for L q deeply virtual Compton scattering wide angle Compton scattering form factors Study of hard exclusive processes leads to a new class of PDFs Generalised Parton Distributions H q, E q, H q, Ẽ q timelike Compton scattering GPDs orbital angular momentum transverse localisation possible access to orbital angular momentum p p annihilation γγ ππ, γγ KK exclusive meson production deep virtual/large t deep inelastic scattering PDFs J q = 1 2 ( 1 1 xdx(hq + E q )) t J q = 1 2 Σ + L q exclusive: all products of a reaction are detected = missing energy ( E) and missing Mass (M x ) = DESY PRC Mai 24 p.7/18

8 GPDs Introduction quantum numbers of final state select different GPDs γ x - ξ x + ξ γ γ x - ξ x + ξ π +, π γ x - ξ q ρ, Φ, ω q x + ξ P - 2 GPD P + 2 P - 2 GPD P + 2 P - 2 GPD P + 2 DVCS: pseudo-scalar mesons vector mesons H q, E q, H q, Ẽq Hq, Ẽq H q, E q What does GPDs characterize? unpolarized polarized H q (x, ξ, t) Hq (x, ξ, t) conserve nucleon helicity H q (x,, ) = q, H q (x,, ) = q E q (x, ξ, t) Ẽ q (x, ξ, t) flip nucleon helicity not accessible in DIS x, t, ξ defined on the light cone x: longitudinal momentum fraction t: momentum transfer (t = 2 ) ξ: exchanged longitudinal momentum fraction (ξ = x Bj/2 1 x Bj /2 ) DESY PRC Mai 24 p.8/18

9 How to Measure E, Ẽ? meson production σ Hermes kinematics: vector mesons pseudoscalar mesons σ L A UT σ L A UT (nominator) (nominator) ξ x B 2 x B H (1 ξ 2 ) 1 ξ 2 H (1 ξ 2 ) E (ξ 2 + t 4M 2 ) 1 ξ 2 Ẽ ξ 2 t 4m 2 1 ξ2 ξ 1 ξ2 ξ ξ.1.3 ξ x=.1.5 t.2.1 4M 2 DESY PRC Mai 24 p.9/18

10 Exclusive π + result γ * p π + n HERMES PRELIMINARY 1 2 uncorrected for radiative effects cross section in 3 x-bins σ tot (nb) < x < < x <.26 sensitivity to complete new data Ẽ at higher x comparison with theory in progress.26 < x < Q 2 ( GeV 2 ) DESY PRC Mai 24 p.1/18

11 How to Measure E, Ẽ? DVCS A C, A LU A UL A UT (twist-2 amplitudes of the interference terms only) H F 1 ξ(f 1 + F 2 ) ξ 2 F 1 + t 4M 2 (1 ξ 2 )F 2 H ξ(f 1 + F 2 ) F 1 ξ 2 (F 1 + F 2 ) E Ẽ t ξ 4M F ξ (F 1 + F 2 ) ξ 2 F 1 + t 4M (F ξ 2 F 2 ) ξ 2 1+ξ F 1 + ξ t 4M 2 F 2 ξ 2 t 4M 2 (F 1 + F 2 ) F 1 and F 2...Dirac and Pauli form factor to access E transverse target polarisation is essential DESY PRC Mai 24 p.11/18

12 Exclusive Scattering Missing Mass to select exclusive events rate Unpol. Hyd. (2) Monte Carlo rate M x 2 (GeV 2 ) Monte Carlo (all) exclusive BH+DVCS BH with resonance exc. semi-inclusive + VMs exclusive π Background from Resonances SIDIS tag recoil Nucleon M x 2 (GeV 2 ) DESY PRC Mai 24 p.12/18

13 Recoil Detector Measure the recoiling target nucleon SciFi/Lightguide Connector Ring Photon Detector (3 layers tungsten/scintillator) C3 Collimator (Tungsten) Water Cooling for Si Det. Si Det. Connectors Si Det. Hybrid SciFi 2 SciFi 1 Thin walled Scattering Chamber TIGRE Sensors Si Det. Frame (Aln) Target Cell DESY PRC Mai 24 p.13/18

14 p [GeV/c] Measure the recoiling target nucleon Silicon (position only) Silicon SciFi Recoil Detector 135 to 14 MeV/c momentum coverage low p cut off due to E-loss in target cell 76% acceptance in φ π-p separation via de/dx θ [rad] DESY PRC Mai 24 p.13/18

15 Silicon Detector Silicon strip detector in HERA machine vacuum 2-sided readout two layers for de/dx 496 channels 135 to 4 MeV/c momentum coverage HELIX chip with HADC charge division (2 gain ranges) DESY PRC Mai 24 p.14/18

16 Silicon Detector Silicon strip detector in HERA machine vacuum 2-sided readout two layers for de/dx 496 channels 135 to 4 MeV/c momentum coverage HELIX chip with HADC charge division (2 gain ranges) All modules necessary at hand. DESY PRC Mai 24 p.14/18

17 Silicon Detector Silicon strip detector in HERA machine vacuum 2-sided readout two layers for de/dx 496 channels 135 to 4 MeV/c momentum coverage HELIX chip with HADC charge division (2 gain ranges) DESY PRC Mai 24 p.14/18

18 Silicon Detector Silicon strip detector DESY test beam (e+ beam) S/N = 6.2 Erlangen test beam (< 11 MeV p) in HERA machine vacuum 2-sided readout two layers for de/dx 496 channels 135 to 4 MeV/c momentum coverage HELIX chip with HADC charge division (2 gain ranges) DESY PRC Mai 24 p.14/18

19 Scintillating Fiber Detector 3 to 14 MeV/c momentum range Two separate planes (barrel) each plane two cylinders of stacks two layers of scintillation fibers 4992 channels 64-pixel PMTs for light conversion DESY PRC Mai 24 p.15/18

20 Scintillating Fiber Detector counts 4 Protons 35 Pions photo electrons momentum 3 MeV/c response of the sum of the two layers DESY PRC Mai 24 p.15/18

21 Scintillating Fiber Detector DESY PRC Mai 24 p.15/18

22 Photon Detector detect neutral particles photons from π o decay 3 layers of scintillator strips fiber light guides tungsten as pre-shower gain monitoring system DESY PRC Mai 24 p.16/18

23 Photon Detector momentum 6 MeV/c use detector response for PID Number of Events Pions Protons QDC Channel DESY PRC Mai 24 p.17/18

24 Coffee is approaching Collins FF with transverse pol. target or BSA GPDs give access to orbital angular momentum of quarks transverse pol. target needed to access E exclusive π production access to H, Ẽ DVCS access to H install the Recoil Detector in sumer 25 focus on DVCS with e- and e+ beam other topics: Hyperon (strange quark), Penta-quark, exclusive VM, target fragmentation... DESY PRC Mai 24 p.18/18