1 / 13

Hadron Formation in Nuclei in Deep-inelastic Scattering

Hadron Formation in Nuclei in Deep-inelastic Scattering. Erika Garutti (NIKHEF) On behalf of the HERMES collaboration. Nuclear Attenuation on 14 N and 84 Kr Kinematics Dependences Attenuation for Different hadron types Hadron Formation Times Conclusion and Outlook.

zahir-melendez
Télécharger la présentation

Hadron Formation in Nuclei in Deep-inelastic Scattering

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Hadron Formation in Nuclei in Deep-inelastic Scattering Erika Garutti (NIKHEF) On behalf of the HERMES collaboration • Nuclear Attenuation on 14N and 84Kr • Kinematics Dependences • Attenuation for Different hadron types • Hadron Formation Times • Conclusion and Outlook Erika Garutti

  2. Hadron Production in DIS on nuclei • Nuclear Attenuation: • Reduction of multiplicity of the • fast forward hadrons due to: • Hard partonic interactions • Soft hadron interactions. • Formation time: tf = lf / c Fragmentation functions from SIDIS multiplicities DF FF Erika Garutti

  3. Motivation • Why is formation time of interest? • Dependence on hadron type • Comparison to model predictions • Link to Heavy Ion physics • Formation time in Heavy Ion physics: • Initial energy density in Quark Gluon Plasma plasma formation time  Estimate t0 ~ tf (?) • Impact of tpf in dilepton spectrum (P.Filip,J.Pisut Phys. Lett. B 411 (1997) 187) Predictions for in Pb-Pb (LHC, @ 160 GeV) depend on tpf mT = transverse mass A = collision area of two nuclei dN/dy = rapidity density Erika Garutti

  4. HERMES experiment dP/P = (0.7-1.3)%, dq < 0.6 mrad detector eff. 99% (e+), RICH eff. 95% (p), 85% (K), 73% (p) r ~ 1015-1016nucl/cm-2 , gas: 2H, 3He, 14N, 20Ne, 84Kr • Tracking: • Particle ID: • Target: Erika Garutti

  5. Hadron Attenuation 14N z > 0.8 Unexplored region • Data Selection • Kr: p, K, (p) from RICH • 2.5 (4) < Ph < 15 GeV • x > 0.06 , y < 0.85 • Q2 > 1 GeV2 , W2 > 4 GeV2 N: h, p from Cerenkov • Ph < 1.4, 4 < Pp < 13.5 GeV Erika Garutti

  6. Fragmentation Function Modification Model • (Guo & Wang , PRL 85 (2000) 3592) • Modification of Dhf(z) in medium due to • multiple parton scattering (in QCD) • Dhf(z) modification increases for small n • Dhf(z) modification scales with A2/3 Erika Garutti

  7. Parton Energy Loss (X.N. Wang, hep-ph/0111404) Calculated from DIS data: cold matter Compared to hadron yield in Au-Au collisions: expanding system (QGP)  dE/dx ~ 0.25GeV/fm  dE/dx ~ 0.3GeV/fm Erika Garutti

  8. Gluon Bremsstrahlung Model • (B.Kopeliovich et al., hep-ph/9511214) • pQCD based model for high-z mesons: • Highly virtual quark looses energy via gluon • emission till final meson is formed • nuclear suppression + • induced radiation •  • Suppression of high-z mesons • high-z: quarks emit only few gluons • correspond to small tf • long time for hadron-Nucleus interaction: Strong Suppression Erika Garutti

  9. Hadron Separation vsn • Observations: • Ratt|p+/p- ~ Ratt|K+/K- •  tfp+/p- ~ tfp+/p- • R att|p< Ratt|p : • s(pd) @ 3s(pd) @ E = 1 GeV (?) • R att|p< Ratt|p/K •  tfp> tfp/K (?) • Average kinematics Erika Garutti

  10. Hadron Separation vs z • R att(z)|p ~ Ratt (z)|K •  • R att|p >1 for low z: • rescattering (?) • R att|p at high z: • information on Dpq(z) • (Guo & Wang , PRL 85 (2000) 3592) Erika Garutti

  11. Cronin Effect In Heavy Ion Collisions: Enhancement at high pt in AA collisions relative to pp collisions. In DIS on nuclei: Agreement with multiple parton scattering model (E.Wang and X.N.Wang nucl-th/0104031)  Transition at pt ~ 1-2 GeV/c • Similar pt2-enhancement • Clean information on quark • transport in cold nuclear matter Erika Garutti

  12. Conclusions & Outlook • Strong nuclear attenuation at high z • Similar attenuation for p and K • Observed: R att|p< Ratt|p/K • Interpretation: tfp> tfp/K (?) • Gluon bremsstrahlumg model describes n and z dependence of nuclear attenuation for pions. • Comparison between 14N and 84Kr in agreement with Dhf(z) modification model. • Observed Cronin effect with a transition between hard and soft processes around pt = 1 GeV. more to come: • additional HERMES data on 4He and 20Ne • comparison to theory for separate hadron type Erika Garutti

  13. Formation Time Extraction • Model used: • one time scale with • sq = 0, sh = 25 mb • i.e. n = 14 GeV, z = 0.5 •  tpf = 3 10–23 sec Erika Garutti

More Related