Charmonium and Charmonium-Like States with BaBar Page: 2 of 4
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
The BABAR experiment - which is described in detail elsewhere [1, 2] - has recently obtained
several important results in charmonium and charmonium-like physics. Below the DD threshold,
the expected charmonium states are well established and their properties, when measured, are in
good agreement with predictions. Nevertheless, in the last years, a plethora of unexpected states
has been observed above the DD threshold. This non-regular charmonium genealogy started with
the observation of the X(3872) resonance , and the interpretation of these states is still unclear.
In the studies of the charmonium(-like) spectrum, the complete data sample collected at the
PEP-II asymmetric energy e+e- collider has been used. This sample consists of integrated lumi-
nosities of 425.6 fb recorded at an energy in the e+e- center-of-mass (CM) frame equal to the
T(4S) mass, 28.0 fb at the T(3S), and 13.6 fb at the T(2S). Samples collected at CM energy
30-40 MeV below each T peak, which correspond to ~10% of the total luminosity are used as well.
Here we present two recent results obtained by BABAR. The first concerns the evidence for the
decay X(3872) -> J/yio reported in the study of the B ,+ _* J/1Iw+w-oKo,+ processes , while
the second involves the study of the charmonium resonances produced in two-photon interactions,
resulting in the K K wT and K+K-+- final states .
2. Evidence for the decay X(3872) -- J/iyw
The X(3872) state has been primarily observed in decays to J/iy'+ - . Evidence for
X(3872) -> J/ypydecay has established positive C-parity for the resonance . Moreover, analyses
of the w+- mass distribution and of the angular distribution have restricted the available JP values
for X(3872) to 1+ or 2- .
Here we analyze the decays BO,+ _ J/1p+w-oKo,+, selecting the mass window for the
three-pion (3w) system in the o region as 0.740 < m,1 < 0.795 GeV/c2. The same processes
have already been analyzed in , but selecting 0.770 < m,1 < 0.795 GeV/c2, with the aim of
confirming the Y(3490) -> J/yio decays. Apart from the enlarged o mass window for the 3w
system, the same selection criteria as in  are applied. )
We look at the J/ypo mass distribution on data collected at the T(4S) energy, corresponding e
to ~ 467 x 106 BB pairs, for both charged and neutral B decays. The mass spectra are shown in
Fig. 1 (a, c), with a zoom in the low-mass region in (b). The fit components are the X(3872)
resonance, the Y(3940) resonance, and a non-peaking background contribution. We find evi-
dence for the X(3872) decaying to J/yio with a 4.0- significance, when considering both sta-
tistical and systematic uncertainties. The mass of this resonance is measured to be: mx(3872) =
3873.0 1 (stat.) 1.3(syst.) MeV/c2. We also measure mass and width of the Y(3940) resonance:
my(394O) = 3919.1+34(stat.) t 2.0(syst.) MeV/c2 and -y(394o) = 31(g Statt.) 5(syst.) MeV.
In Fig. 1 (d, e, f) the mass distribution for the 3w system is shown for charged decays, neutral
decays, and combining them, respectively. Monte Carlo (MC) simulated events with either S- or
P-wave distributions are superimposed on the distribution obtained when combining charged and
neutral B decays. The analysis favors the P-wave description, so that among the JP values still
allowed for the X(3872) meson, 2- is preferred. For this assignment, the X(3872) mass falls
within the broad range available to the 1c2 (1D) charmonium state.
Charmonium and charmonium-like states with BABAR
Here’s what’s next.
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.
Guido, Elisa. Charmonium and Charmonium-Like States with BaBar, article, March 14, 2014; United States. (digital.library.unt.edu/ark:/67531/metadc864635/m1/2/: accessed May 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.