FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago1 A Measurement of Differential Cross Sections in Charged-Current Neutrino Interactions on Iron and a Global Structure Functions Analysis  Experimental work on the CCFR/NuTeV neutrino experiments.  Phenomenological studies with all deep inelastic scattering data. Un-Ki Yang Univ. of Rochester (currently, Univ. of Chicago) (CCFR-NuTeV Collaboration) 4 Phys. Rev. Lett. 1 Eur. Phys J. C. 1 Phys. Rev. D

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago2 Structure functions: QCD + PDFs for hadron collider  Low x region (0.01<x<0.1): F2( ) & F2(  ) have 10-20% discrepancy =>very large uncertainty in sea quarks. Tevatron p-p cross section is dominant.  d/u at high x (0.1<x<1) Disagreement with CDF W asymm data =>poor understanding of d/u at high x Important for precise measurements on W prod. at Tevatron, HERA and LHC  Very high x PDFS (x>0.7) Only SLAC data (low Q2) available, but dominated by non-perturbative QCD effects Crucial for high Q2 new physics at Tevatron, HERA, and LHC.  Neutrino scattering F2( ) = x[(u+u) + (d+d) + (s+s) ] xF3( ) = x[(u-u) + (d-d) ]  Charged-lepton (e,  ) scattering F2(p) = x[4/9(u+u) + 1/9(d+d) + 1/9(s+s) ] F2(n) = x[4/9(d+d) + 1/9(u+u) + 1/9(s+s) ] assuming d p = u n Deep inelastic scattering

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago3 Low x problem in F2 (0.01<x<0.1) Discrepancy in F2 between neutrino & muon experiments (left) Finally, resolved it using Physics-Model-Independent extraction approach (right) CCFR( ) NMC(  ) PRL 79, 1213 (1997) Seligman at al [CCFR] PRL 86, 2742 (2001) Yang et al [CCFR]  Large pdf uncertainties at low x  …..many efforts from world…  R(long) effect: - Bodek-Rock-Yang model - CCFR R (PRL 87, (2001)  Iso-spin symm. violation(d p =u n ) ( ruled out using CDF W asymm data ) PRL 83, 2829 (2001) Bodek et al (no heavy charm, strange sea corrections)

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago4 d/u problem at high x  A problem in d/u was indicated by the CDF W asymm. data and the NMC F2(d)/F2(p) data. - large uncertainty in nuclear effects on deuterium  A significant change in d/u after nuclear binding correction on deuteron data Excellent agreement with CDF W asymm. data d/u -> 0.2 at x=1 (QCD prediction) A high-pt jet rate is increased by 11%(evolution) A large increase in the HERA CC high Q2 PRL 82, 2467 (1999) Yang and Bodek

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago5 PDFs at high x?  Any additional valence quarks at very high x and low Q2 could produce a large increase to PDFs at high Q2 and intermediate x.  There are precise SLAC data, but not used by the MRS & CTEQ group, because of large non-perturbative QCD effects [ target mass effect, higher twist effects ] We find out that NLO pQCD + GP target mass + renomalon higher twist: describe the data very well. Very High x data ? PRL 82, 2467 (1999) Yang and Bodek

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago6 NNLO pQCD + TM + Higher twist Size of the higher twist effect with NNLO analysis is really small.  Most of the higher effects originate from the NNLO terms.  Estimation of the ratio of the NNLO and NLO PDFs indicates that the predctions fo the Z production will be increased by 2%. Eur Phys J C13, 241 (2000) Yang and Bodek Develop a modified GRV94 LO PDFs for neutrino cross sections at high and low Q2 region (down to 0): hep-ex/

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago7 Very high x F2 proton data (DIS + resonance) NLO pQCD + TM + higher twist describes very high x DIS F 2 and resonance F 2 data well up to x=0.98 Good understanding of u quark dist. 10% uncertainty up to x=0.9 only 10-20% uncertainty at 0.9<x<0.98 Impact on searches for new physics at proton colliders PRL 82, 2467 (1999) Yang and Bodek

FNAL Users meeting, 2002Un-ki Yang, Univ. of Chicago8 Conclusion: Ready to use the nucleon as a tool in searching for new physics in hadron colliders? My deep appreciation to everyone!!! Supervisor: A. Bodek My dear CCFR-NuTeV colleagues [ M. Shaevitz, W. Smith, R. Bernstein et al, especially SF group (Seligman, Conrad)] + MRST / CTEQ groups + many others friends who have helped on my journey + Rochester + Chicago + Fermilab / DOE / NSF + perhaps Korean military too(?) + definitely, my Lord and family