$D^0 \bar{D}^0$ Mixing at BaBar Page: 3 of 4
4 pagesView a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
fit with all parameters fixed to their previously determined values. The fitted D0 lifetime is
found to be consistent with the world-average lifetime [20].
The measured proper-time distribution for the WS signal is modeled by Eq. (1) convolved
with the resolution function determined in the RS proper-time fit. The random grf and mis-
reconstructed D0 backgrounds are described by the RS signal proper-time distribution since
they are real D0 decays. The proper-time distribution for WS data is shown in Fig. 1. The fit
results with and without mixing are shown as the overlaid curves.
The fit with mixing provides a substantially better description of the data than the fit with
no mixing. The significance of the mixing signal is evaluated based on the change in negative
log likelihood with respect to the minimum. The likelihood maximum is at the unphysical value
of '2 = -2.2 x 10-4 and y' = 9.7 x 10-3. The value of -2A1n G at the most likely point in the
physically allowed region (a'2 = 0 and y' = 6.4 x 10-3) is 0.7 units. The value of -2A ln for
no-mixing is 23.9 units. Including systematic uncertainties, this corresponds to a significance
equivalent to 3.9 standard deviations (1 - CL = 1 x 10-4) and thus constitutes evidence for
mixing.
Allowing for the possibility for CP violation, the values for D0 and D0 decay-time dependence
are fit separately.No evidence for CP violation is seen. The best fit in each case is more than
three standard deviations away from the no mixing hypothesis.
As a cross-check for the mixing signalthe fitted WS branching fractions are are extrapolated
and are seen to increase as a function of time. The slope is consistent with the measured mixing
parameters and inconsistent with the no-mixing hypothesis1600
1400
a 1200
c 1000
800
> 600
w
400
20050
0
-s0-2 -1 0 1
t(ps)2 3
00 1
0.015
0.01
0.005
0
-0.005
-0.01
-0.015-0.001 -0.0005
0 0.0005 0.001
x2Figure 1. a) The proper-time distribu-
tion of combined D0 and D0 WS candi-
dates. b) The points represent the differ-
ence between the data and the no-mixing
fit. The solid curve shows the difference
between fits with and without mixing.Figure 2. BABAR and BELLE combined
average of the ( 2, y') projection
mapped liklehood -> (, y), assuming
CP conservation.To evaluate the systematic uncertainties in RD and the mixing parameters, variations in the
fit model and the selection criteria have been considered. Alternative forms of the mp>, Am,
t, and At PDF's are also considered. The t and At requirements were varied. In addition,
variations that keep or reject all D*+ candidates sharing tracks with other candidates were
considered.- Data --
- a) 0 Mixing it
- Randomrzs -
Msrecon D
-- M Combinatonial_
- , -_, - T "X'9 t -
b)
- t
--l,6
3a
$6FP2O207
' " - ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
_
N
a
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Coleman, Jonathon. $D^0 \bar{D}^0$ Mixing at BaBar, article, October 26, 2011; United States. (https://digital.library.unt.edu/ark:/67531/metadc846481/m1/3/: accessed May 30, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.