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Klaus Rith

Deep-inelastic scattering – an overview. (A collection of my favourite highlights). Klaus Rith.

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Klaus Rith

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  1. Deep-inelastic scattering – an overview (A collection of my favourite highlights) Klaus Rith IWHSS2013 Erlangen, July 22-24, 2013

  2. Deep-inelastic lepton nucleon scattering - DIS k‘= (E‘,k‘) hadrons e () e  Q2 = - q2 = -(k-k‘)2  1 GeV2  = Pq/M x=Q2/(2Pq)= fraction of nucleon‘s four-momentum P, carried by struck quark W2= (q +P)2  Q2(1/x-1) > (3M)2  q xP *, Z0 W ()  e   P nucleon k= (E, k) From angular and momentum distributions of scattered leptons Internal structure of the nucleon Structure functions F1,2,3(x,Q2) Parton distribution functions q(x,Q2), g(x,Q2) () K.R. 2

  3. First DIS measurements SLAC: 1969 … M. Breidenbach et al., PRL 23 (1969) 935 Scaling:F2(x,Q2) Quark parton model pointlike constituents fractional charge (F2p  F2n) spin-1/2 (2xF1  F2) F2(x) = q eq2x (q(x) + q(x)) F2d(x)dx  0.5 *5/18 total quark-momentum fraction  1/2 Ee = 7-17 GeV gluons QCD 3 K.R.

  4. HERA measurements of F2p(x,Q2) - I 40 years later C. Diaconu et al., Ann. Rev. Nucl. Part. Sci. 60 (2010) 259 SLAC: 1969 … Ee = 27.6 GeV, Ep = 920 GeV K.R. 4

  5. HERA measurements of F2p(x,Q2) - II H1, F.D. Aaron et al., JHEP 09 (2012) 061 Pattern of scalebreaking perfectly described by NNLO-QCD (DGLAP) No evidence for non-linear QCD effects (saturation) EIC, LHeC 5 K.R.

  6. F2p,d(x,Q2) from stationary-target experiments From global fit: HERMES relative normalisation ~2% for p and d and ~0.5% for the ratio Exploring perturbative to non-perturbative regime in an unmeasured x-Q2 region 0.006 < x < 0.9 0.1 GeV2 < Q2 < 20 GeV2 HERMES, A. Airapetian et al., JHEP 05 (2011) 126 Ratio d/p (F2d/F2p) Proton Deuteron New region covered by HERMES Good agreement with world data in the overlap region 6 K.R.

  7. Q2 evolution of PDFs Q2 = 104 GeV2 Q2 = 10 GeV2 Q2 = 2 GeV2 Need additional information (, , DY, SIDIS) H1, F.D. Aaron et al., JHEP 09 (2012) 061 HERAfitter 7 K.R.

  8. Q2 dependence of NC and CC cross sections H1, F.D. Aaron et al., JHEP 09 (2012) 061 e W- u,.. e- elm  e4/Q4 e W+ d,.. e+ weak  g4/(Q2 + M2W,Z)2 (e2=g2sin2W) 8 K.R.

  9. Total polarised CC cross section L R W- W+ e-L q e+R q H1, F.D. Aaron et al., JHEP 09 (2012) 061 e- CCep (Pe) = (1  Pe)CCep (Pe=0) R No sign of r.h currents W- e-R q Chiral structure of SM confirmed e+ Convert to 90% CL on heavy WR: mW,R > 208 GeV (H1) 9 K.R.

  10. More Accomplishments from HERA collider C. Diaconu et al., Ann. Rev. Nucl. Part. Sci. 60 (2010) 259 QCDtests, s(Q2), Jet production Charm and beauty production Diffraction DVCS Searches for new physics • But unfortunately • noed • noeA • noep EIC, LHeC   10 K.R.

  11. Nuclear effects in DIS EMC, J.J. Aubert et al., PL B123 (1983) 275 30th Anniversary So far 982citations 11 K.R.

  12. Nuclear effects in DIS: x dependence Depletion of qV(x) Depletion of q(x) ‚Shadowing‘ Small enhancement Anti-‚Shadowing‘ Fermi motion 12 K.R.

  13. Nuclear effects at low x EMC-NA28, M. Arneodo et al., PLB 211 (1988) 493 EIC-bible,A. Accardi et al., arXiv: 1212.1701 E665,M.R. Adams et al., PRL 68 (1992) 3266; Z. Phys. C 67 (1995) 403 NMC, M. Arneodo et al., Nucl. Phys. B 441 (1995) 3; Nucl. Phys. B 481 (1996) 3 Prospects for EIC A Q2 < 1 GeV2 ? Q2 < 1 GeV2 Origin (infinite momentum frame): overlap of low-x partons from various nucleons  parton-partonfusion Possibly earlier onset of saturation More data needed for x < 0.01 to constrain nPDFs, especially g(x) in nuclei EIC, LHeC 13 K.R.

  14. Nuclear effects for x > 1 • A(e,e‘) @ x > 1 sensitive to • high momentum tail of nuclear wavefunction • NN short-range correlations (SRC) • (multiquark clusters) 4He/3He Cross section ratios show plateaus, Height of plateaus denoted as a2 and a3 12C/3He a2, a3 = (A/A)/(D/2) 56Fe/3He L. Frankfurt et al., PRC 48 (1993) 2451 K. Egyan et al., PRC 68 (2003) 014313 K. Egyan et al., PRL 96 (2006) 082501 N. Fomin et al., PRL 108 (2012) 092502 14 K.R.

  15. Correlation between EMC effect and SRC L.B. Weinstein et al., PRL 106 (2011) 052301 xA = xp (Amp/mA) (L. Frankfurt and M. Strikman, Int. J. Mod. Phys. E21 (2012)1230002) EMC effect and SRC are highly correlated SRC seem to be the origin of the EMC effect for x = 0.3-0.7 15 K.R.

  16. Polarised DIS EMC, J. Ashman et al., PLB 206 (1988) 364 (so far1669 citations) Proton q+(x) = q q-(x) = q q(x) = q+(x) – q-(x) Helicity DF g1(x) = ½ q eq2q(x) q = 01 q(x) dx   0.12  0.09  0.14   qq Quark spin contribution consistent with zero spin crises 16 K.R.

  17. Polarised DIS 25 years later Proton q+(x) = q q-(x) = q Deuteron q(x) = q+(x) – q-(x) Helicity DF g1(x) = ½ q eq2q(x) q = 01 q(x) dx   qq Deuteron data:   0.33  0.03  0.03 See talk by K. Kurek 17 K.R.

  18. Q2 dependence of g1(x,Q2) EIC-bible,A. Accardi et al., arXiv: 1212.1701 Prospects for EIC Proton Deuteron Scaling violations for g1(x,Q2) much smaller than for F2(x,Q2) Determination of gluon helicity DF g(x,Q2) ‚challenging‘ See talk by K. Kurek K.R. 18

  19. N Gluon helicity distribution from polarised DIS COMPASS, C. Adolph et al., arXiv:1211.6849 Photon-gluon fusion e‘ e DIS measurements are compatible with 0, large values of G excluded Hadrons with high pt But: sign and shape still badly known, Need additional info, e.g., from pp Charm production See talk by K. Kurek 19 K.R.

  20. Semi-inclusive DIS - SIDIS z = Eh/ eqeq  FactorisationeNehX = DFNq FFqh DF(x,Q2): Parton Distribution Function – q(x,Q2)  f1q(x,Q2), q(x,Q2)  g1Lq(x,Q2), Tq(x,Q2) )  h1q(x,Q2), … FF(z,Q2): FragmentationFunction– D1qh(z,Q2), H1qh(z,Q2), … 20 K.R.

  21. Charged-hadron multiplicities in SIDIS UU  f1q  D1qh Determination ofDFsandFFs Disentanglement of z and Ph dependences Access to intrinsic quark kT and fragmentation pT <Ph2> = z2<kT2> + <pT2> HERMES, A. Airapetian et al., PR D 87 (2013) 074029 COMPASS, C. Adolph et al., arXiv:1305.7317 See talks by E. Aschenauer & M. Stratmann 21 K.R.

  22. Semi-inclusive logitudinal double-spin asymmetries pions kaons COMPASS, PLB 693 (2010) 227 PLB 680 (2009) 217 HERMES, PR D 71 (2005) 012003 SMC, PLB 420 (1998) 180 Proton Deuteron See talk by K. Kurek 22 K.R.

  23. Quark helicity distributions q(x) COMPASS, PL B 693 (2010) 227 Prospects for EIC 5-flavour fit, assuming s = s DSSV, Phys. Rev. D 80 (2009) 034030 See talk by K. Kurek 23 K.R.

  24. Nucleon tomography • - transverse quark momenta kT • - spatial quark position r • quark orbital angular momenta (OAM) • spin-orbit correlations 24 K.R.

  25. OAM in atomic physics Atom: non-relativisticelectronsin nucleon‘sCoulomb potential Rutherford Bohr, Schrödinger, .. Add angular momentum n, l, ml(r,,) 25 K.R.

  26. OAM and nucleon structure Nucleon: relativisticquarks in strong colourfield Inclusive DIS kT r xP P Add angular and transverse momentum Wigner DF W(r,kT, x) no probabilistic interpretation due to Heisenberg u.r. [kT, r] 0  … dkT  … dr TMDs GPDs Number density of quarks with fraction x of longitudinal nucleon momentum P (kT-dependence) (r-dependence) See talk by B. Pasquini at IWHSS12 26 K.R.

  27. Quark Leading twist TMDs long. pol. unpol. trans. pol. number density Boer-Mulders f1 h1 kT unpol. (U) T-odd h1L g1L helicity worm-gear 2 kT long. pol. (L) Nucleon transversity h1 f1T g1T Sivers worm-gear 1 trans. pol. ( T) kT kT h1T pretzelosity kT T-odd See talks by G. Schnell & M. Radici chiral-odd  27 K.R.

  28. d6 Quark First glimpse by dx dy dz d ds dP2h long. pol. unpol. trans. pol. number density Boer-Mulders f1 h1 kT unpol. (U) Cahn cos 2 T-odd h1L helicity g1L worm-gear 2 kT long. pol. (L) sin 2 Nucleon transversity h1 H1u-(z) < 0 Non-zero, need OAM f1T g1T Sivers worm-gear 1 sin(+s) trans. pol. T) kT kT h1T pretzelosity kT sin(-s) cos(-s) sin(3-s) T-odd See talks by G. Schnell & M. Radici chiral-oddhi(x)H1(z) 28 K.R.

  29. Extracted TMDs and FFs Transversity DF Sivers DF Prospects for EIC M. Anselmino et al., PRD 87 (2013) 094019 M. Anselmino et al., arXiv:1107.4446 u Data from COMPASS HERMES u BELLE d xh1(x) xf1T(x) d Collins FF Orbital angular momenta ofupand down quarkshaveoppositesign u+ zH1(z) u- See talks by G. Schnell, M. Radici & M. Boglione 29 K.R.

  30. Hard Exclusive Measurements 30 K.R.

  31. Generalised Parton Distributions (GPDs) Generalised description of nucleon structure in 2+1 dim Number density of quarks with longitudinal momentum fraction x at radial position r Spin-½ target: 4 chiral-even (+ 4 chiral-odd) leading-twist quarkGPDs H,H (E,E) conserve (flip) nucleon helicity require quark OAMLq    x +1 Access: hard exclusive processes Ji: Jq= ½ lim-1dx x [Hq(x,,t) + Eq(x,,t) ] ,t0 Vector mesons (, , ) H, E Pseudoscalar mesons(,) H, E DVCS () H, E, H, E     31 K.R.

  32. Deeply Virtual Compton Scattering Theoretically cleanest way to access GPDs TDVCS << TBH@ HERMES Interference between DVCS and Bethe-Heitler amplitude DVCS Bethe-Heitler AXY Access to GPD combinations through azimuthal asymmetries First example:Beam-spin asymmetry beam target HERMES,PRL 87 (2001) 182001 CLAS,PRL 87 (2001) 182002 polarisation 32 K.R.

  33. HERMES results for DVCS Beam chargeasymmetry GPD H AC ALU Beam helicityasymmetry GPD H Transverse target-spinasymmetries GPD E AUT ALT Shift due to E AUL Longitudinal targetspinasymmetries GPD H ~ ALL  +1 q= lim-1dx x [Hq(x,,t) ,t0 f =  33 K.R.

  34. Example: DVCS – Beam Charge Asymmetry HERMES, JHEP 07(2012) 032 constantterm:  -ACcos  Re[F1H] higher twist gluon leading twist resonant fraction ( 12%) ep e+ Complete data set including 2006-07 MX2 = (Pe + Pp – Pe´- P)2 34 K.R.

  35. DVCS with Recoil Detector A. Airapetian et al., JINST 8 (2013) P05012 kinematic fitting ep ep  - All particles in final state detected  4 constraints from energy-momentum conservation - Selectionofpure BH/DVCS (ep ep) withhighefficiency ( 83%) - Allows to suppress background from associated and semi-inclusive processes to a negligible level 35 K.R.

  36. DVCS with Recoil Detector HERMES, JHEP 10 (2012) 042 1.96% scale uncertainty Basically no contamination  Clear interpretation Rather good agreement with models Indicationthatleadingamplitudefor pure elasticprocessisslightly larger thanforunresolvedsignal (elastic + associated) ( Assoc. in traditional analysismainlydilution) More: H. Moutarde 36 K.R.

  37. Outlook Past 44 years: DIS has provided the crucial ingredients for our understanding of nucleon structure Near future: More exciting results to come from COMPASS II, JLAB12, … Far future: Thanks 37 K.R.

  38. Backups

  39. Transverse double-spin asymmetry ALT: A2, g2  -  ALT = = AT cos  +  A2 = kin1 AT+ kin2g1/F1 g2 = kin3 F1AT– F1 kin4 g1/F1 EPJ C 72 (2012) 1921 twist-2 twist-3 g2 (x,Q2) = g2 WW(x,Q2) + g2(x,Q2) 1 new g2 WW(x,Q2) = - g1(x,Q2) +  g1(y,Q2) dy x 1 d2 (Q2) = 3  x2g2(x,Q2) dx 0 1 Burkhardt-Cottinham SR:  g2(x,Q2) dx = 0 0 HERMES (@ Q2 = 5 GeV2): d2 = 0.0148  0.0096(stat)  0.0048(sys) 0.9  g2(x,Q2) dx = 0.006 0.024  0.017 0.023 PBHERAII << PBHERAI

  40. Explanation of shadowing – infinite momentum frame Parton-parton fusion (property of nucleus) parton Saturation at very low x - - non-linear QCD dynamics? K.R.

  41. Proton: transverse target pol. asymmetry Sensitive to GPD E JHEP 06 (2008) 066 Model: VGG with variation of Ju, while Jd=0

  42. K.R.

  43. Fragmentation in nuclear matter typical hadronisation length  (1-z)  is of order of nucleus size (1-10 fm) time development of hadronisation can be studied with nuclei of increasing size struck quark or qq-pair propagate through ‚cold‘ nuclear matter interaction signature: reduction of the numer of hadrons per DIS event and per nucleon Courtesy of J. Rubin) Useful for understanding the fundamental aspects of hadronisation Input for calculations of nuclear PDFs and FF Multi-dimensional study

  44. Fragmentation in nuclear matter Example: -dependence recent EPJ A 47 (2011) 113 less pronounced trends in Ne compared to Kr and Xe +, -, K-: increase of RA with  K+: increaseof RAwith forlowest z-slize, flatter behaviourforhigher z p: weak -dependence p: RA exceeding unity at high  and low z (apart from hadronisation other production mechanisms contribute)

  45. HERMES detector (2006-07) detection of recoiling proton

  46. GPD extraction M. Murray, DIS12

  47. Spatial quark densities from GPDs - model From C. Lorce, B. Pasquini, PR D 84 (2011) 014015  Nq (bx,y = r), See talk by B. Pasquini at IWHSS11

  48. Deeply Virtual Compton Scattering Theoretically cleanest way to access GPDs Interference between DVCS and Bethe-Heitler amplitude TDVCS << TBH@ HERMES DVCS Bethe-Heitler AXY Access to GPD combinations through azimuthal asymmetries beam target HERMES: Complete set of asymmetries polarisation Bothbeam charges Both beam helicities Unpolarised H,D and nuclear targets Longitudinally polarised H and D targets Transversely polarised H target Recoildetector

  49. Azimuthal asymmetries in DVCS Beam-spin asymmetry HERMES,PRL 87 (2001) 182001 CLAS,PRL 87 (2001) 182002 CLAS,PRL 97 (2006) 072002 Longitudinal target-spin asymmetry

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