Properties of Exotic Charmonium-like States at CDF Page: 3 of 5
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select B+ signal candidates with a mass within 3- of the nominal B+ mass; the purity of
the B+ signal in that mass window is about 80%.
The combinatorial background under
the B+ peak includes B hadron decays
such as B -> p(2S)p -> J/gr+r-c, in
which the pions are misidentified as kaons.
However, background events with misiden-
tified kaons cannot yield a Gaussian peak
at the B+ mass consistent with the 5.9
MeV/c2mass resolution. Figure 3 shows the
K+K- mass from p+-K+K--K+ candi-
dates within 3- of the nominal B+ mass
with B sidebands subtracted and before ap-
plying p mass window requirement. Using
a smeared P-wave relativistic Breit-Wigner
(BW)  line-shape fit to the spectrum re-
turns a X2 probability of 28%. This shows
that the B+ - J/vK+K--K+ final state is
well described by J/ppK+.
We then examine the effects of detector
acceptance and selection requirements using
B+ - J/ppK+ MC events simulated by a
phase space distribution. The MC events
are smoothly distributed in the Dalitz plot
and in the J/pp mass spectrum. No arti-
facts were observed from MC events. Fig-
ure 4 shows the Dalitz plot of mn2(pK+)
versus m2(J/pp), and Fig. 5 shows the
mass difference, AM m(p+-K+K-) -
m(pp--), for events in the B+ mass win-
dow in our data sample. We examine the en-
hancement in the AM spectrum just above
J/pp threshold. We exclude the high
mass part of the spectrum beyond 1.56
GeV/c2 to avoid combinatorial backgrounds
that would be expected from misidentified
B - 2 (2S) -> (J/v72r+r--)# decays. We
model the enhancement by an S-wave rela-
CDF II Preliminary, 2.7 fb-1
16 18 20 22 24
Figure 4: The Dalitz plot of mn2(pK+) ver-
sus m2(J/pp) in the B+ mass window. The
boundary shows the kinematic allowed region.
CDF II Preliminary, 2.7 fb-1
1 1'.1 1A2 1.3 1. 1.5
Figure 5: The mass difference, AM, between
p+/-K+K- and p/+f-, in the B+ mass win-
dow. The dash-dotted curve is the background
contribution and the red solid curve is the to-
tal unbinned fit.
tivistic BW function  convoluted with a Gaussian resolution function with the RMS fixed
to 1.7 MeV/c2 obtained from MC, and use three body phase space  to describe the back-
ground shape. An unbinned likelihood fit to the AM distribution, as shown in Fig. 5, returns
a yield of 14 5 events, a AM of 1046.3 2.9 MeV/c2, and a width of 11.7+8 MeV/c2.
We use the log-likelihood ratio of -21n(Co/max) to determine the significance of the
enhancement, where Go and max are the likelihood values for the null hypothesis fit and
signal hypothesis fit. The -21n(Co/Lmax) value is 5.3 for a pure three body phase space
background shape assumption. We generate AM spectra using the background distribution
alone, and search for the most significant fluctuation with -21n(Lo/ma) > 5.3 in each
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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/m1/3/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.