FNAL Users meeting, 2002 Un-ki Yang, Univ. of Chicago 1

A Measurement of Differential Cross Sections A Measurement of Differential Cross Sections in Charged-Current Neutrino Interactions on in Charged-Current Neutrino Interactions on

Iron and a Global Structure Functions AnalysisIron 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, 2002 Un-ki Yang, Univ. of Chicago 2

Structure functions: QCD + PDFs for hadron collider

Low x region (0.01<x<0.1):

F2(F2() & F2() & F2() have 10-20% discrepancy) have 10-20% discrepancy =>very large uncertainty in sea quarks.=>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 dp = un

Deep inelastic scattering

FNAL Users meeting, 2002 Un-ki Yang, Univ. of Chicago 3

Low x problem in F2 (0.01<x<0.1)

Discrepancy in F2between 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, 251802 (2001)Iso-spin symm. violation(dp=un) (ruled out using CDF W asymm data)

PRL 83, 2829 (2001) Bodek et al

(no heavy charm, strange sea corrections)

FNAL Users meeting, 2002 Un-ki Yang, Univ. of Chicago 4

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 Q2PRL 82, 2467 (1999) Yang and Bodek

FNAL Users meeting, 2002 Un-ki Yang, Univ. of Chicago 5

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, 2002 Un-ki Yang, Univ. of Chicago 6

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/0203009

FNAL Users meeting, 2002 Un-ki Yang, Univ. of Chicago 7

Very high x F2 proton data (DIS + resonance)

NLO pQCD + TM + higher twist describes very high x DIS F2 and resonance F2 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, 2002 Un-ki Yang, Univ. of Chicago 8

Conclusion:Ready to use the nucleon as a tool in searching for new physics in hadron colliders?

My deep appreciation to everyone!!!

Supervisor: A. BodekMy 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