12 August 2003Kevin McFarland, University of Rochester

NuTeV and the Strange Sea NuTeV/CCFR dimuon data

is uniquely sensitive to strange sea ± from semi-leptonic charm decay

NuTeV Paschos-Wolfenstein sin2W would agree with SM if strange sea had 30% momentum asymmetry

( )

N X

(Cabbibo supp.) beam: , cs d (Cabbibo supp.) beam: , cs d

12 August 2003Kevin McFarland, University of Rochester

The Data

Forward dimuon d2(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( ) ( )s x s x

12 August 2003Kevin McFarland, University of Rochester

Neutrino Data

12 August 2003Kevin McFarland, University of Rochester

Anti-Neutrino Data

12 August 2003Kevin McFarland, University of Rochester

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 fitsPortheault et al [BPZ update] NLO

Zero asymmetry [DIS03]

( ) ( )xs x xs x

12 August 2003Kevin McFarland, University of Rochester

Last Week…

Olness, Tung et alia [CTEQ] LO QCD Small asymmetry, ~+10% (CTEQ d-quark PDFs)

inconsistency with zero not claimeduses 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?

( ) ( )xs x xs x

12 August 2003Kevin McFarland, University of Rochester

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

12 August 2003Kevin McFarland, University of Rochester

Dimuons and Asymmetry

x region of CTEQ asymmetry is covered by NuTeV dimuon data

CTEQ Asymmetry

NuTeV Dimuons

12 August 2003Kevin McFarland, University of Rochester

Conclusions

Large strange sea asymmetry can explain NuTeV Paschos-Wolfenstein sin2W

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

12 August 2003Kevin McFarland, University of Rochester

Rumors of the demise of the Paschos-Wolfenstein R- have

been greatly exaggerated

12 August 2003Kevin McFarland, University of Rochester

Backup: Internal Iron PDF fit

12 August 2003Kevin McFarland, University of Rochester

Backup: Isospin Violation

Isospin violation in PDFs plausible at level of mq/QCD~1%5% solves NuTeV sin2W 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, F2

d/F2p used in NuTeV analysis

12 August 2003Kevin McFarland, University of Rochester

Backup: Isospin Violation (2)

Naïve analysis (ad hoc addition) of MRST central value suggests sin2W 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?

12 August 2003Kevin McFarland, University of Rochester

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 sin2W

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

sin2W if KLOE confirms BNL-E865