1 / 17

Quark pair production using dipole formalism in neutrino-proton scattering at high energies *

Quark pair production using dipole formalism in neutrino-proton scattering at high energies *. Mairon Melo Machado High Energy Phenomenology Group, GFPAE IF – UFRGS, Porto Alegre melo.machado@ufrgs.br www.if.ufrgs.br/gfpae. * In collaboration with M. B. Gay Ducati and M. V. T. Machado.

cais
Download Presentation

Quark pair production using dipole formalism in neutrino-proton scattering at high energies *

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. Quark pair production using dipole formalism in neutrino-proton scattering at high energies* Mairon Melo Machado High Energy Phenomenology Group, GFPAE IF – UFRGS, Porto Alegre melo.machado@ufrgs.br www.if.ufrgs.br/gfpae *In collaboration with M. B. Gay Ducati and M. V. T. Machado

  2. Outline • Lepton-nucleon collision • Color dipole formalism • Structure functions • Neutral Current (NC) process • Neutrino-nucleon cross section • Results and conclusions

  3. 1GAY DUCATI, M. B.,MACHADO, M. M., MACHADO, M. V. T. – PLB 644 (2007) 340; Motivations • Interaction of high energy neutrinos on hadron targets are an important probe to test QCD and to understand the parton properties of hadron structure • Combinations of neutrino and anti-neutrino scattering data used to determine the structure functions • The structure function F2 is the singlet distribution • Phenomenology using saturation models within the Color Dipole Approach successfully describes current small-x data 1 • Purpose of a new high-energy, ultra-high statistics neutrino scattering experiment (NuSOnG)

  4. Neutrino-nucleon collision Z (q) p’j pi • M is the nucleon mass • E is the neutrino energy • p and q are the nucleon and boson four-momenta pj pk

  5. 2 Neutrino-nucleon cross section • GF is the Fermi constant 1.166.10-5 GeV-2 • Mi is the boson mass • F2, FL and F3 are the structure functions 2 ROBERTS, R. G., “The structure of the proton”, Cambridge University Press (1993);

  6. Color dipole phenomenology • ’s are the wave functions for electroweak bosons • z is the momentum fraction of quark and (1-z) is the momentum fraction of the antiquark • 1 and 2 are the helicities of the quarks (1/2 or -1/2) • r is the transversal size of the dipole • dip is parametrized and fitted to the experiment.

  7. Structure functions sin 2θW = 0.23120 Chiral coupling K0,1 are the McDonald functions

  8. Quark distribution • Gluon emits a quark-antiquark pair changing the quark distribution in the nucleon • These quarks are called sea quarks • Quark content is given by the sum of valence quarks and sea quarks

  9. 3 GOLEC-BIERNAT, K; WUSTHOFF, M. PRD 60, 1140231 (1998); 4 IANCU, ITAKURA, MUNIER, PLB 590, 199 (2004); Dipole cross section • Golec-Biernat-Wusthoff (GBW) 3 • Iancu-Itakura-Munier (IIM) 4 , 0 = 23 mb,  ~ 0.288, x0 ~ 3.10-4 m,mf = 0.14 GeV Y=ln(1/x), BCGC = 5.5 GeV-2 HEP 08

  10. Neutrino-nuclei interaction 5 • Dipole cross section for bosons transversally or longitudinally polarized are extended for nuclei using Glauber-Gribov formalism • Nuclear profile function TA (b) • b is the impact parameter and n(r) is the nuclear matter density normalized as 5 WATT, G. KOWALSKI, H. PRD 78 (2008) 014016 HEP 08

  11. Structure functions (x fixed) Virtuality dependence for b-CGC and GBW models Small deviation more sizable at large Q2 Quarks (d,s) dominat over u Electroweak couplings Charm contribution 13%

  12. Structure functions (Q2 fixed b-CGC model) • Dependence approximatelly power-like with an effective power which growths on Q2 • λ(Q2=1 GeV2) ~ 0.12 • λ(Q2=M2Z) ~ 0.224 • Unusual behavior in the limit of large Q2 and large x

  13. Structure functions (Q2 fixed GBW model) • Estimates the uncertainty from the theoretical side • GBW model does not include the QCD evolution in the dipole cross sectin • Effective power is similar to the b-CGC model • FL being distinct at Q2=M2Z • Flattening in FL is stronger in b-CGC than in GBW

  14. NC charm structure functions F2 Q2 x F2 F3 F3

  15. Neutral Current Cross Section Results 6 neutrino-proton interaction • Contribution of sea quarks dominates at high energies 6 KWIECINSKI, J. et al. PRD 59 (1999) 093002

  16. Neutral Current Cross Section Results neutrino-nuclei interaction 0.23 fb

  17. Conclusions • Analysis of small-x neutral current neutrino-nucleus is performed within the color dipole formalism • Structure functions F2 and FL are investigated • Employement of two phenomenological parametrizations for the dipole cross sections which succesfully describe small-x data • Deviations among the models at very small-x data • Further investigations are requested • Computation of the charm content to the total NC neutrino cross section consistent with current experimental measurements

More Related