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D + Leptonic and D 0 Semileptonic Decays First Results from BESIII. Ron Poling School of Physics and Astronomy College of Science and Engineering University of Minnesota. Window on Weak and Strong Physics. Leptonic Decay.

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D+Leptonic and D0Semileptonic Decays First Results from BESIII

Ron Poling

School of Physics and Astronomy

College of Science and Engineering

University of Minnesota

window on weak and strong physics
Window on Weak and Strong Physics

Leptonic Decay

  • Decay constant fD incorporates the strong interaction effects (wave function at the origin)
  • Use charm leptonic decays to validate theory (LQCD) and apply to B mixing, which requires fB
  • Multiple tests with charm: fD, fDs (esp. ratios)
  • Sensitivity to New Physics

Ron Poling - ICHEP 2012

window on weak and strong physics1
Window on Weak and Strong Physics

Semileptonic Decay

  • Use Strong Interaction theory (LQCD) for form factor, extract CKM
  • Use other measurements and unitarity for CKM and test theory
  • Theoretical uncertainties can be reduced in determinations of |Vub| if FF calculations can be validated with charm
  • Multiple tests available, semileptonicD decays to pseudoscalar mesons are cleanest

Ron Poling - ICHEP 2012

window on weak and strong physics2
Window on Weak and Strong Physics
  • Widths of mixing and |Vub| bands will be reduced as charm validates LQCD
  • Long-term goal: Over-constrain CKM and search for New Physics

Ron Poling - ICHEP 2012

charm physics at threshold
Charm Physics at Threshold
  • At ψ(3770) charm production is and
  • Fully reconstruct about 15% of D decays
  • Hadronic tag on one side gives “beam” of D0 or D+ on the other side for leptonic/semileptonic studies. Neutrino is reconstructed from missing energy and momentum

Ron Poling - ICHEP 2012

besiii at bepcii
BESIII at BEPCII
  • Comparable capabilities to CLEO-c, plus muon ID
  • The big advantage: BEPCII is a two-ring machine designed for charm
    • Design (achieved) luminosity at ψ(3770): 1 (0.65) x 1033

Ron Poling - ICHEP 2012

besiii data
BESIII Data
  • World’s largest ψ(3770) sample
  • Tools/techniques for precision charm physics still under development – all results are PRELIMINARY
    • analysis is “partially blind” – 0.92 fb-1 analyzed so far. Full 2.9 fb-1 later for final results

Ron Poling - ICHEP 2012

tag selection
- Tag Selection
  • Nine D- tag modes

BESIII Preliminary

Ron Poling - ICHEP 2012

signal selection
- Signal Selection

BESIII Preliminary

  • Exactly one track in addition to tag, with the right charge
  • Positive muon identification
  • No extra photon
  • Select on consistency with leptonic decay:

BESIII Preliminary

425 signal candidates:

small BG, mom. dist.

consistent with

Ron Poling - ICHEP 2012

sample events
- Sample Events
  • Positive muon ID requirement reduces background at the expense of a ~20% efficiency loss

Ron Poling - ICHEP 2012

backgrounds
- Backgrounds

BESIII Preliminary

MC

MC BG est.:

Indep. data est.:

Ron Poling - ICHEP 2012

results
- Results

BESIII Preliminary

  • Excellent agreement with CLEO-c
  • Still statistics limited – need more data!

Ron Poling - ICHEP 2012

comparisons from g rong
- Comparisons (from G. Rong)

LQCD (HPQCD 2012)

(208.3±1.0±3.3) MeV

LQCD (FNAL/MILC 2012)

(219±11) MeV

Ron Poling - ICHEP 2012

tag selection1
- Tag Selection
  • Four D0 tag modes

Ron Poling - ICHEP 2012

signal selection1
- Signal Selection

BESIII Preliminary

  • Tag plus exactly two oppositely-charged tracks
  • Kaon/pion/electron ID
  • Electron has right charge
  • No extra neutral energy
  • Select on consistency with semileptonic decay

BESIII Preliminary

  • Fit U distribution to extract yield

Ron Poling - ICHEP 2012

branching fraction
- Branching Fraction
  • Systematic uncertainties are preliminary
  • Good consistency with CLEO-c, statistical precision is comparable with only 1/3 data analyzed

BESIII Preliminary

Ron Poling - ICHEP 2012

q 2 distribution
- q2distribution

with

  • Partition D0semileptonic candidates in bins of
  • Fit U distribution in each q2 bin

BESIII Preliminary

BESIII Preliminary

Ron Poling - ICHEP 2012

project f q 2
- Project f(q2)
  • Points are data with statistical errors only
  • Curves are Fermilab/MILC (arXiv:1111.5471) with ±1σ (statististical) bands

BESIII Preliminary

BESIII Preliminary

Ron Poling - ICHEP 2012

ff parameterizations
- FF Parameterizations

Simple Pole Model

Modified Pole Model

Becirevic and Kaidalov PLB 478, 417 (‘00)

Series Expansion

Becher and Hill PLB 633, 61 (‘06)

Ron Poling - ICHEP 2012

ff fits
- FF Fits

Ron Poling - ICHEP 2012

ff results
- FF Results
  • Reasonable consistency with CLEO-c, comparable precision with 2/3 of data still to analyze

BESIII Preliminary

Ron Poling - ICHEP 2012

future charm prospects at besiii
Future Charm Prospects at BESIII
  • Finalize and on the 2.9 fb-1ψ(3770) sample
  • Extend to and other modes
  • Highlights of coming data runs:

2012-2013ECM=4260 and 4360 MeV for “XYZ”

studies (0.5 fb-1 each)

2013-2014ECM=4170 MeV for Ds (~2.4 fb-1)

TBD Additional ψ(3770) data

Ron Poling - ICHEP 2012

summary and conclusions
Summary and Conclusions
  • First results from the BESIII experiment have been presented on
  • D+Leptonic Decays
  • D0Semileptonic Decays
  • BESIII has arrived for precision charm physics, with more data and more measurements to come

Ron Poling - ICHEP 2012

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