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New results from

New results from. Delia Hasch. (on behalf of the HERMES Collaboration). DPG Spring Meeting 2004 – Nuclear Physics. Cologne (Germany) March, 8-12 2004. Exotic baryons: the HERMES pentaquark Spin: first measurement of Transversity Nuclear matter: production and transport of hadrons.

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New results from

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  1. New results from Delia Hasch (on behalf of the HERMES Collaboration) DPG Spring Meeting 2004 – Nuclear Physics Cologne (Germany) March, 8-12 2004 • Exotic baryons: the HERMES pentaquark • Spin: first measurement of Transversity • Nuclear matter: production and transport of hadrons

  2. [PLB 585(2004),213] Events / (8 MeV) ( < 1.0cm) decay ( < 0.6cm) ( > 7cm) direct reconstruction: detection of each decay particle, invariant mass reconstuction Exotic baryonic states

  3. [PLB 585(2004),213] Pythia6 + mixed event background M = 1528 MeV s = 8 MeV mixed event background Pythia6 excited S* hyperons (not included in Pythia6)  + The signal and the background Monte Carlo • gen: M=1450 MeV , s=2 MeV • reco: M=1450 MeV , s=7 MeV

  4. SPIN: even they were puzzled N. Bohr  W. Pauli

  5. relevant kinematic variables fragmentation function distribution function Semi-inclusive deep inelasting scattering

  6. Collaboration of 180 phys., 33 Inst., 12 Countries HERMES @ DESY

  7. HERA e+/e- beam of 27.6 GeV, I~40 mA, beam-pol~55% HERMES in 1 slide polarisation by Sokolov-Ternov effect:

  8. HERA e+/e- beam of 27.6 GeV, I~40 mA, beam-pol~55% HERMES in 1 slide • pure polarised gas targets: 3He, H, D ~1015 n/cm2 • pure UNpolar. gas targets: H, D, He, N, Ne, Kr ~1017 n/cm2 polarised targets: spin reversal every 120 sec

  9. HERA e+/e- beam of 27.6 GeV, I~40 mA, beam-pol~55% HERMES in 1 slide • pure polarised gas targets: 3He, H, D ~1015 n/cm2 • pure UNpolar. gas targets: H, D, He, N, Ne, Kr ~1017 n/cm2 • forward spectrometer: dp/p~2%, dq<0.6 mrad, 40-220 mrad • kinematics: 0.02<x<0.6, 1.0<Q2<15 GeV2

  10. hadron separation double radiator RICH for p, K, p ID Particle identification hadron/positron separation combining signals from: TRD, calorimeter, preshower, RICH

  11. The quark contents of the nucleon

  12. The quark contents of the nucleon

  13. CHIRAL ODD NOT ALLOWED IN E.M. INTERACTIONS single helicity flip The quark contents of the nucleon

  14. high sensitivity to the valence quark polarisation q and q have opposite sign. _ peculiarity of transversity relativistic nature of quark: in absence of relativistic effects h1(x)=g1(x) chiral odd FF: Collins FF Q2 –evolution: unlike for g1p(x), the gluon doesn’t mix with quark in h1p(x) double helicity flip single helicity flip tensor charge: first moment of h1 calculations from lattice QCD The quark contents of the nucleon

  15. angle of hadron relative to initial quark spin (Sivers) • chiral-even naïve T-odd DF • related to parton orbital momentum • violates naïve universality of PDF • - different sign of in DY peculiarity of (Sivers) (Collins) Azimuthal angles and asymmetries angle of hadron relative to final quark spin (Collins)

  16. fit amplitudes simultanously (prevents mixing effects of acceptance) Azimuthal angles and asymmetries

  17. Azimuthal angles and asymmetries

  18. kind of brainstorm is under way for model interpretation Sivers moments Collins moments Transverse asymmetry for p+, p-, p0 • first measurement of naïve T-odd DF • in DIS (orbital momentum) • opposite sign from DY (RHIC…)? • large p+ expected puzzle (?) • surprisingly large disfavoured p-

  19. FF on nucleon: DF and FF on nucleon & nuclear medium What happens in a nuclear medium ?

  20. Nuclear attenuation observation: reduction of multiplicity of fast hadrons due to both hard partonic and soft hadron interaction

  21. significant attenuation of fast forward hadrons [PLB577(2003),37] Nuclear attenuation observation: reduction of multiplicity of fast hadrons due to both hard partonic and soft hadron interaction

  22. Experimental findings: p+ = p- = p0 ~ K- Hadron separation vs n [PLB577(2003), 37] K + > K- - p > p, p > p, p > K

  23. Fragmentation function modification (parton energy loss) [X.N.Wang et al., NPA696(2001)788, PRL89(2002)162301] • 1 free parameter tuned on 14N (quark-gluon correlation strength inside nuclei) • dE/dx for HERMES  dE/dx for PHENIX (Au) @RHIC

  24. fixed by HERMES data Gluon density [X.N.Wang et al., NPA696(2001)788, PRL89(2002)162301] • cold <--> hot nuclear matter correlation • gluon density in Au+Au~15 times higher than in cold matter

  25. narrow exotic baryon resonance has been directly reconstructed { M= 1528 ± 2.6 ± 2.1 MeV s= 8 ± 2 MeV precise determination of the mass background description by Monte Carlo simulation ongoing data taking with 3 tracks trigger for exotics search exotics Conclusion & outlook Delia Hasch

  26. narrow exotic baryon resonance has been directly reconstructed { M= 1528 ± 2.6 ± 2.1 MeV s= 8 ± 2 MeV precise determination of the mass background description by Monte Carlo simulation first observation of non-zero Sivers effect ongoing data taking with transversely polarised target sizeable Collins asymmetries measured for p0 and p-;p+puzzle a kind of brain storm is underway for model interpretation exotics Conclusion & outlook spin: transversity Delia Hasch

  27. narrow exotic baryon resonance has been directly reconstructed { M= 1528 ± 2.6 ± 2.1 MeV s= 8 ± 2 MeV precise determination of the mass background description by Monte Carlo simulation first observation of non-zero Sivers effect GOAL: obtain unambiguous information on hadron formation and transport in cold nuclear matter sizeable Collins asymmetries measured for p0 and p-;p+puzzle a kind of brain storm is underway for model interpretation significant hadron suppression in a wide kinematic region first observation of hadron-type dependence of attenuation exotics Conclusion & outlook spin: transversity nuclear matter Delia Hasch

  28. narrow exotic baryon resonance has been directly reconstructed { M= 1528 ± 2.6 ± 2.1 MeV s= 8 ± 2 MeV precise determination of the mass background description by Monte Carlo simulation first observation of non-zero Sivers effect sizeable Collins asymmetries measured for p0 and p-;p+puzzle a kind of brain storm is underway for model interpretation significant hadron suppression in a wide kinematic region Stay tuned … New exiting results will come soon ! first observation of hadron-type dependence of attenuation exotics Conclusion & outlook spin: transversity nuclear matter Delia Hasch

  29. Uncertainty from diffractive VM contribution desired process: SIDIS ep pX different physics: diffractive r0 production

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