NuTeV and the Strange Sea

1. NuTeV and the Strange Sea • NuTeV/CCFR dimuon datais uniquely sensitive to strange sea • m± from semi-leptonic charm decay • NuTeV Paschos-Wolfenstein sin2qW would agree with SM if strange sea had 30% momentum asymmetry Kevin McFarland, University of Rochester

2. The Data • Forward dimuon d2s(E)/dxdy • To extract strange sea, need: • fragmentation and decay, down quarks • Neutrino and anti-neutrino difference(after removing Cabbibo suppressed contribution)is signature of Kevin McFarland, University of Rochester

3. Neutrino Data Kevin McFarland, University of Rochester

4. Anti-Neutrino Data Kevin McFarland, University of Rochester

5. Previous Results • Dimuon fits to CCFR/NuTeV data • Goncharov et al [NuTeV] LO“+” QCDZero asymmetry(CTEQ, GRV d-quark PDFs)or Small asymmetry, -(9±5)%(NuTeV internal LO+ d-quark PDFs on iron) • Mason et al [NuTeV] NLO [ICHEP02] • Zero asymmetry (CTEQ, GRV d-quark PDFs) • Inclusive data fits • Portheault et al [BPZ update] NLOZero asymmetry [DIS03] Kevin McFarland, University of Rochester

6. Last Week… • Olness, Tung et alia [CTEQ] LO QCDSmall asymmetry, ~+10%(CTEQ d-quark PDFs) • inconsistency with zero not claimed • uses inclusive data and dimuons • Paper speculates that ad hoc NuTeV parameterization may be problem? • Strangeness not conserved at x below charm production threshold • It’s a good point: does it matter? Kevin McFarland, University of Rochester

7. Any asymmetry in Dimuons? • Collapse the data in E, y as function of x • Solid line assumes symmetric sea • Dashed is CTEQ asymmetry effect • Independent of parameterization, no significant asymmetry Kevin McFarland, University of Rochester

8. Dimuons and Asymmetry • x region of CTEQ asymmetry is covered by NuTeV dimuon data CTEQ Asymmetry NuTeV Dimuons Kevin McFarland, University of Rochester

9. Conclusions • Large strange sea asymmetry can explain NuTeV Paschos-Wolfenstein sin2qW • Gambino’s conclusion“RPW is not a place for precision”based on two flawed assumptions • that recent CTEQ central value is right and others are wrong • that data can’t control the difference • Neither assumption is proven correct Kevin McFarland, University of Rochester

10. Rumors of the demise of the Paschos-Wolfenstein R- have been greatly exaggerated Kevin McFarland, University of Rochester

11. Backup: Internal Iron PDF fit Kevin McFarland, University of Rochester

12. Backup: Isospin Violation • Isospin violation in PDFs plausible at level of mq/LQCD~1% • 5% solves NuTeV sin2qW puzzle • MRST have opened a new window! • Global PDF fits with isospin violation • Early days… • Form of parameterization? Other PDFs? • Interesting to note: constraints come from CCFR, F2d/F2p used in NuTeV analysis Kevin McFarland, University of Rochester

13. Backup: Isospin Violation (2) • Naïve analysis (ad hoc addition) of MRST central value suggests dsin2qW of -0.0011 • 2/3 of a sigma towards Standard Model • But sadly, MRST conclude both signs of effect are still allowed by data • Empirically, isospin violating PDFs are still a viable explanation • but theory is still our best guide about size • MRST has given us a great start on testing this. Can it be improved? Kevin McFarland, University of Rochester

14. Backup: K+e3 • Dr. Gambino pointed out that BNL-E865 K+e3 fixes us the 1st row CKM unitarity problem • This also has the uncomfortable side effect of exacerbating the NuTeV sin2qW • easy to see why: electron neutrinos from K+e3 are a major background to neutral current! • naïve estimate is that this is +1/2 sigma in sin2qW if KLOE confirms BNL-E865 Kevin McFarland, University of Rochester