Transcript CLEO-c A New Frontier in Weak Interactions

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I have outdated numbers for the D Hadronic BR analysis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.
D Hadronic Branching Fractions
And Vub
Dan Cronin-Hennessy
University of Minnesota
CLEO Collaboration
May 27, 2005
Outline

CLEO-c Program

First Results on D Hadronic Branching Fractions

Weak Annihilation Limits from CLEOII/IIV
CESR @ Cornell
CESR
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.
3560603-002
CsI
Electromagnetic
Calorimeter
CLEO
RICH
CsI
Electromagnetic
Calorimeter
(End Cap)
Drift Chamber
Outer Endplate
Drift Chamber Endplate
Small Radius Section
cos

= 0.93
CESR
ZD Inner Drift Chamber
Interaction Point
RICH
Kaon eff = 0.8
Kaon eff = 0.85
Kaon eff = 0.9
B physics
Ring Imaging Cherenkov Detector
Designed for B decays.
Clean separation in charm
region.
K-p separation shown.
CLEO-c
CLEO-c
(3770) – 3 fb-1 ((3770) DD ~ s=6 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)
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.
Hadronic D Branching Fractions
D
e
D  K p p 
Single tags
are clean
e

D
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)
Double Tags
S = 2*(e*BR)*NDD
D = (e*BR)2*NDD
NDD = S2/4D
Simple description
sDD = NDD/L (do not need e, BR)
Doubly
Tagged
D+K-p+p+,
D-K+p-p-
Prelim.
DATA
~60 pb-1
Analysis
9 Decay modes measured
Single tags:
N 2 N Be
Double tags:
N
Bi 
Ne
Ne
ij
j
j
ij
i
i
DD
ij
 N DD Bi B j e ij
N DD 
i
NNe
2 N ee
i
j
ij
ij
i
To first order Bi independent of tag modes
and efficiencies.
•Simultaneous fit for all BR and cross sections.
•All correlations taken into account.
Syst unc cancels.
j
D0
Fits
Line shapes include ISR, FSR, resolution,
beam energy spread.
Efficiencies include FSR correction.
D+
Tracking systematic determined using recoil mass:
Reconstruct  p from ’ pp.
Peak at p mass2.
Pion found
MC
Data
Pion not found
Systematics
Results
D0 Modes
D+ Modes
*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.
Results
Cross Sections
Branching fraction analysis fringe benfit:
Precision measurement of DD production cross sections.
Interesting to note:
PDG: Gee and G  s((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.
Charge to Neutral Ratio
Rc/n
Measured
Predicted
sqrt(s) MeV
Prediction:
M. Voloshin (hep-ph/0402170)
These (and other) data-theory
discrepancies have prompted
speculation of 4-quark component
of (3770). See hep-ph/0504197
Unitarity Constraints
Today
With 1000/pb from B factories and
CLEO-c lattice calibration
Transition Slide
CLEO-c will allow B factory
measurements to reach full potential
by calibrating lattice QCD.
 form factor measurements
(see Feng Liu’s talk)
 D meson decay constant (fD)
(Zhongchao Li’s talk)
CLEO II/IIV analyses at Y(4S) energies
continue to improve our knowledge
of CKM constraints…
BXu l n
Lepton energy spectrum
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.
PRL 88 231803 2002
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.
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.
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?
WA Search
bu model:
“Hybrid” model which includes resonant and nonresonant 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).
DeFazio-Neubert:
JHEP 99, 017
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
WA Search
30 models used.
q2 for various PDF parameters
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.
Sample fit projections.
WA fits
Sample fit projections.
All but bu and WA subtracted
WA fits
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
Results
Endpoint
El>2.2 GeV
Shape function regime
Mx
Mx<1.55 GeV
Pl>1.0 GeV/c
q2 and Mx
q2>8.0 GeV2
Mx<1.7 GeV
Pl>1.0 GeV/c
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.
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.