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CLEO-c A New Frontier in Weak Interactions

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Prelude for practice talk: I have outdated numbers for the D Hadronic BR analysis. I have the papers and a week so will fix soon. ... – PowerPoint PPT presentation

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Title: CLEO-c A New Frontier in Weak Interactions


1
  • Prelude for practice talk
  • ?I have outdated numbers for the D Hadronic BR
    analysis
  • ?I have the papers and a week so will fix soon.
  • ?Tables grabbed from recent talks but they will
    be replaced.
  • ?Figures will be as they are presented today.
  • Need to add preliminary in some places (WA).
  • Some fluff at beginning will be removed as I
    think of more important things to say.
  • Talk is 40 minutes.

2
D Hadronic Branching Fractions And Vub
Dan Cronin-Hennessy University of Minnesota CLEO
Collaboration May 27, 2005
3
Outline
  • CLEO-c Program
  • First Results on D Hadronic Branching Fractions
  • Weak Annihilation Limits from CLEOII/IIV

4
CESR
CESR _at_ Cornell
Cornell Electron-positron Storage Ring ?e e-
collisions sqrt(s) 1.8 5.6 GeV ?Low energy
running Natural damping of beam lost (1/20).
?CESR-c First demonstration of wiggler
dominant ring.
5
CLEO
6
RICH
Kaon eff 0.8 Kaon eff 0.85 Kaon eff 0.9
  • Ring Imaging Cherenkov Detector
  • Designed for B decays.
  • Clean separation in charm
  • region.
  • K-p separation shown.

B physics
CLEO-c
7
CLEO-c
?(3770) 3 fb-1 (?(3770) ?DD s6 nb) Hadronic
D decays Semileptonic D decay (D decay constant,
form factors, Vcs,Vcd, Mixing, CPV, rare/nonSM)
Accumulated Luminosity 280/pb Results Today
60/pb (pilot sample)

8
Hadronic D Branching Fractions
Motivation ?Provide most precise measurement of
D hadronic BRs. ?Many current measurements
determined with respect to normalizing modes
(e.g. D ? K p , D ? K p p). ?CLEO-c will provide
absolute measurements. ?Counting D mesons
provides DD production cross sections. ?First
step toward improved constraints on D mixing
parameters.
9
Hadronic D Branching Fractions
Basic Strategy (for most CLEO-c analyses) D
Tagging ?Full reconstruction of one D meson
(Tag D). ?Search remainder of event for signal
D decay. ?Continuum, t pair, radiative return
events suppressed significantly.
?Efficiency is analysis dependent -15 to 20.
(Large BR of D mesons and low
multiplicity)
Single tags are clean
10
Double Tags
S 2(eBR)NDD D (eBR)2NDD NDD S2/4D
sDD NDD/L (do not need e, BR)
Simple description
Doubly Tagged D?K-pp, D-?Kp-p-
Prelim. DATA 60 pb-1
11
Analysis
9 Decay modes measured
Single tags
Double tags
Syst unc cancels.
To first order Bi independent of tag modes and
efficiencies.
  • Simultaneous fit for all BR and cross sections.
  • All correlations taken into account.

12
Fits
D0
D
Line shapes include ISR, FSR, resolution, beam
energy spread. Efficiencies include FSR
correction.
13
Tracking systematic determined using recoil
mass Reconstruct y p from y?y pp-. Peak at p
mass2.
Systematics
Pion found
Pion not found
MC
Data
14
Results
D0 Modes
D Modes
15
Results
Results from CLEO-c pilot data
sample. Luminosity 60/pb Statistical and
Systematic unc comparable for some modes. Expect
systematics to scale with luminosity since many
of these are determined from data.
Agreement with PDG. PDG numbers are correlated
among modes. CLEO-c numbers correlated (from
simultaneous fit). CLEO-c include FSR correction.
16
Cross Sections
Branching fraction analysis fringe benfit
Precision measurement of DD production cross
sections.
Interesting to note PDG Gee and G ? s(y(3770)
? hadrons) 10 nb But only a 2 sigma effect at
this time. CLEO-c will provide a significantly
improved cross section measurement that will
allow measurement of non-DDbar y(3770) decays
at or below a nb.
17
Charge to Neutral Ratio
Prediction M. Voloshin (hep-ph/0402170) The
se (and other) data-theory discrepancies have
prompted speculation of 4-quark component of
y(3770). See hep-ph/0504197
Measured
Rc/n
Predicted
sqrt(s) MeV
18
Unitarity Constraints
Transition Slide
Today
CLEO-c will allow B factory measurements to
reach full potential by calibrating lattice QCD.
? form factor measurements (see Feng
Lius talk) ? D meson decay constant (fD)
(Zhongchao Lis talk)
With 1000/pb from B factories and CLEO-c lattice
calibration
CLEO II/IIV analyses at Y(4S) energies continue
to improve our knowledge of CKM constraints
19
B?Xu l n
  • Vub Inclusive
  • ?Isolating b?u component requires
  • measurement in restricted kinematic regions.
  • ?Must know fraction of b? u events in acceptance
  • region.
  • ?Progress has been made in last five years by
  • using b to s g to understand b quark fermi motion
  • and b quark mass. This essentially trades
    modeling
  • uncertainties for experimental uncertainties and
  • has resulted in precision Vub extraction.
  • Does not remove all sources of theoretical
  • uncertainties.
  • ?Must find other ways to limit these
    uncertainties
  • using additional measurements.

Lepton energy spectrum
PRL 88 231803 2002
20
Weak Annihilation
Annihilation of valence quarks
(leptonic). Hadronization of residual brown
muck. Estimates of rate suggest small
contribution from these processes. (Order
1/mH3) However, if rate is distributed
differently than the more dominant b?u production
processes then the impact on Vub can be
significant. Extreme example Leptonic decay,
B? l n, places rate at the kinematic endpoint.
21
Weak Annihilation
Are there methods of quantifying WA
experimentally? High statistics of B-factories
will allow comparison of charge and neutral
measurements. D meson analyses at CLEO-c
provide additional opportunities (m3 dependence
suggests effects may be larger in charm sector
(D0/D width difference) Or we can just look
directly for WA kinematic signature in available
B samples We have looked. Using CLEOII/IIV
data (10/fb). Approach Traditional inclusive
B semileptonic analysis.
Lepton identification plus neutrino
recontruction. Observable of
interest is lepton-neutrino mass (q2 spectrum).
Look for anomalous rate in high
q2 region. Bump hunting yes
but with a model as a guide.
22
WA Search
Expected Contributions B? Xc l n
Kinematically limited well below B? Xu l n
but still contributes due to
experimental resolution. Continuum B? Xu l
n (b ? u l n) Weak annihilation?
23
WA Search
DeFazio-Neubert JHEP 99, 017
b?u model Hybrid model which includes
resonant and non-resonant modes. Known
branching ratios and form factors for resonances.
Combined resonant and non-resonant modes follow
HQET expectations (with constraints on HQET
parameters imposed by b? s g measurements).
24
Weak annihilation model Invented for this
analysis. Leptons carry most momentum. Soft
hadronic component, X Ex, Mx, px LQCD
q2 MB2 - LMB
WA Search
q2 for various PDF parameters
Distribution function for Mx and px. Flat
distribution of width x. Exponential drop
dictated by L
25
WA Search
30 models used.
q2 for various PDF parameters
26
WA fits
Strategy Binned c2 fit. 30 bins in q2. 3 bins
in pl.. Fakes and continuum normalization
known/fixed. Normalizations for b?c, b?u, and
WA float. Results in N b?c, N b?u NWA.
27
WA fits
Sample fit projections.
28
WA fits
Sample fit projections. All but b?u and WA
subtracted
29
Key points 1)This is a lousy method for
measuring the WA rate. The WA model has too much
freedom in the kinematics. 2)This a good method
for quantifying the impact of WA on Vub.
This analysis is sensitive to WA when these
processes contribute significantly in the
endpoint region. When such is the case the
impact on Vub is large. If WA processes
are spread over a large region of phase space we
are not sensitive (and neither is the extraction
of Vub). We quote our results in terms of the
impact on a typical endpoint analysis rather
than in terms of WA rates. Ra Impact
Ratio
Results
30
Results
q2 and Mx q2gt8.0 GeV2 Mxlt1.7 GeV Plgt1.0 GeV/c
Mx Mxlt1.55 GeV Plgt1.0 GeV/c
Endpoint Elgt2.2 GeV
Shape function regime
31
Summary
  • D Hadronic Branching Fractions
  • I have presented first results from CLEO-c on D
    hadronic BR fractions.
  • With the pilot data sample (60/pb) we have
    agreement with PDG and comparable superior
    uncertainties.
  • Expect significant improvement with new data
    samples already accumulated (and future data).
  • We have measured 9 D decay modes with double
    tagging method which provides absolute BRs. We
    have provided new/improved measurements for
    critical normalizing modes.
  • We are at the level where careful treatment of
    radiative corrections is required.
  • DD cross sections and the charge to neutral
    ratios measured.
  • Future extensions of this analysis will provide
    new D mixing constraints.

32
Summary
  • Vub
  • I have presented a preliminary measurement from
    CLEOII/IIV (10/fb) that allow us to set
    experimental limits on WA contamination of
    analyses that extract Vub.
  • The measurement is statistics limited and we are
    adding data from CLEOIII.
  • We find that the impact on Vub is well below
    current uncertainties.
  • This approach could be improved with better WA
    modeling (need help from theory).
  • We have invented our own model which use LQCD as
    the relevant energy scale for the hadronic
    component.
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