Properties of Exotic Charmonium-like States at CDF Page: 4 of 5
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spectrum in the mass range of 1.02 to 1.56 GeV/c2, with widths in the range of 1.7 (detector
resolution) to 120 MeV/c2 (ten times the observed width).
The resulting p-value from 3.1 million
simulations is 9.3 x 10-6, corresponding to a
significance of 4.3u. We repeat this process 6
with a flat combinatorial non-B background * 5
and three body PS for non-resonance B o
background and we still get a significance
of 3.8u. 1
One's eye tends to draw to a second clus- v 2
ter of events around 1.18 GeV/c2 in Fig. 5, or
around 4.28 GeV/c2 in J/pp mass as shown v 1
in Fig. 6. It is close to one pion mass above .1 4.2 4.3 4.4 4.5 4.6
the peak at the J/pp threshold. However, mJ/v9 (GeV/c2)
this cluster is statistically insufficient to in-
fer the presence of a second structure. To Figure 6: The J/pp mass distribution in the
investigate possible reflections, we examine B+ mass window.
the Dalitz plot and projections into pK+
and J/vK+ spectrum. We find no evidence for any other structure in the pK+ and J/vK+
3 Measurement of the mass of X(3872)
In studying our X(3872) sample we tested
the hypothesis of whether the observed sig- CDF II Preliminary 2.4 fb
nal stems from two different states, as pre-
dicted in four-quark models. We fit the 5
X(3872) mass signal with a BW function
convoluted with a resolution function . 4
Both functions contain a width scale fac- 1
tor that is a free parameter in the fit and 0 3
therefore sensitive to the shape of the mass
signal. The measured width scale factor 2 - 95% C.L. Upper Limit
is compared to the values seen in pseudo
experiments which assume two states with 1 - 90% C.L. Upper Limit
given mass difference and ratio of events.
The resolution in the simulated events is o
corrected for the difference between data Low-Mass Signa Fraction
and simulation measured for the p(2S).
The result of this hypotheses test shows
that the data is completely consistent with Figure 7: Dependence of the upper limit on
a single state. Under the assumption of the mass difference Am between two states on
two states with equal amount of observed the low-mass state signal fraction fi.
events, we set a limit of Am < 3.2(3.6)
MeV/c2at 90% (95%) C.L. The limit for other ratios of events in the two peaks is shown in
Since our signal is consistent with one peak, we proceed and measure the X(3872) mass
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Yi, Kai & U., /Iowa. Properties of Exotic Charmonium-like States at CDF, article, June 1, 2009; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc927346/m1/4/: accessed September 25, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.