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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