11,855 research outputs found
Search for charmonium and XYZ states in at BESIII
Within the framework of nonrelativistic quantum chromodynamics, we study the
production of charmonium states in at BESIII
with (n=1, 2, 3, and 4), (n=1, 2, and 3), and
(n=1 and 2). The radiative and relativistic corrections are
calculated to next-to-leading order for and wave states. We then argue
that the search for states such as , , ,
and in at BESIII may help clarify the nature
of these states. BESIII can search states through two body process
, where decay to , , or
. This result may be useful in identifying the nature of
states. For completeness, the production of charmonium in at B factories is also discussed.Comment: Comments and suggestions are welcome. References are update
Triggered massive and clustered stars formation by together H II regions G38.91-0.44 and G39.30-1.04
We present the radio continuum, infrared, and CO molecular observations of
infrared dark cloud (IRDC) G38.95-0.47 and its adjacent H II regions
G38.91-0.44 (N74), G38.93-0.39 (N75), and G39.30-1.04. The Purple Mountain
Observation (PMO) 13.7 m radio telescope was used to detect12CO J=1-0,13CO
J=1-0 and C18O J=1-0 lines. The carbon monoxide (CO) molecular observations can
ensure the real association between the ionized gas and the neutral material
observed nearby. To select young stellar objects (YSOs) associated this region,
we used the GLIMPSE I catalog. The13CO J=1-0 emission presents two large cloud
clumps. The clump consistent with IRDC G38.95-0.47 shows a triangle- like
shape, and has a steep integrated-intensity gradient toward H II regions
G38.91-0.44 and G39.30-1.04, suggesting that the two H II regions have expanded
into the IRDC. Four submillmeter continuum sources have been detected in the
IRDC G38.95-0.47. Only the G038.95-00.47-M1 source with a mass of 117 Msun has
outflow and infall motions, indicating a newly forming massive star. We
detected a new collimated outflow in the clump compressed by G38.93-0.39. The
derived ages of the three H II regions are 6.1*10^5yr, 2.5*10^5yr, and
9.0*10^5yr, respectively. In the IRDC G38.95-0.47, the significant enhancement
of several Class I YSOs indicates the presence of some recently formed stars.
Comparing the ages of these H II regions with YSOs (Class I sources and massive
G038.95-00.47-M1 source), we suggest that YSOs may be triggered by G38.91-0.44
and G39.30-1.04 together, which supports the radiatively driven implosion
model. It may be the first time that the triggered star formation has occurred
in the IRDC compressed by two H II regions. The new detected outflow may be
driven by a star cluster.Comment: 6 pages, 4 figures, Accepted for publication in A&
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