2,283 research outputs found
Description of the resonance as the atom
We discuss the possibility that the recently reported resonance in the spectrum can be described in terms of residual interactions.Comment: 3 pages, 1 figur
Hadronic Decays of Excited Heavy Mesons
We studied the hadronic decays of excited states of heavy mesons (D, D_s, B
and B_s) to lighter states by emission of pi, eta or K. Wavefunctions and
energy levels of these excited states are determined using a Dirac equation for
the light quark in the potential generated by the heavy quark (including first
order corrections in the heavy quark expansion). Transition amplitudes are
computed in the context of the Heavy Chiral Quark Model.Comment: 4 pages (incl. figures), proceedings of the IV International
Conference on "Hyperons, Charm and Beauty Hadrons", Valencia (Spain
Mass of D*_sJ(2317) and Coupled Channel Effect
The resonance D*_sJ (2317) which is considered to be the 1^3P_0 state
composed of charm and strange quarks has been discovered recently. The measured
mass, which is about 160 MeV lower than the mass of the 1^3P_0 state obtained
from the potential model calculation by Godfrey and Isgur, was considered
surprisingly low and attracted a lot of theoretical investigations. We
calculate the mass shift of the 1^3P_0 state by using the coupled channel
e#ect. Our result shows that the coupled channel e#ect naturally explains the
low mass of D*_sJ (2317)
Testing the Nature of the D_{sJ}^*(2317)^+ and D_{sJ}(2463)^+ States Using Radiative Transitions
The Babar and CLEO collaborations have recently observed states decaying to
D_s^+\pi^0 and D_s^{*+}\pi^0 respectively and suggest the possible explanation
that they are the missing P-wave c\bar{s} states with J^P=0^+ and 1^+. In this
note we compare the properties of the D_{sJ}^*(2317)^+ and D_{sJ}(2463)^+
states to those expected of the c\bar{s} D_{s0}^* and D_{s1} states. We expect
the D_{s0}^* and D_{s1} with the reported masses to be extremely narrow, \Gamma
\sim {\cal O}(10\hbox{keV}), with large branching ratios to D^*_s\gamma for the
D_{s0}^* and to D^*_s\gamma and D_s\gamma for the D_{s1}. Crucial to this
interpretation of the Babar and CLEO observations is the measurement of the
radiative transitions. We note that it may be possible to observe the
in radiative transitions to the .Comment: Major revisions to include recent observation by CLEO of
D_{sJ}(2463)^+ including change of title and additional radiative transitions
included in results. Conclusions are not change
Chiral shifts in heavy-light mesons
The mass shifts of the -wave and mesons due to coupling to
and channels are calculated in the coupling channel model without
fitting parameters. The strong mass shifts down for and states
have been obtained, while and states remain almost in situ. The
masses of and states of mesons have been predicted.Comment: to be published in the Proceedings of the 14th International QCD
Conference, 7th-12th July 2008, Montpellier, Franc
B Decays as Spectroscope for Charmed Four-quark States
The state recently observed by BaBar in the channel
may be the first of a host of four-quark states. We give a
phenomenological account of the masses and decay modes. The isosinglet
state is the only narrow one, dominated by the observed isospin
violating decay and less than 100 keV in width. All other states are
expected to decay hadronically. Notable resonances are in doubly charged
, , wrong pairing , and also ,
channels. We propose B decays as searching ground for such 4-quark states,
which recoil against meson from B decay, or , mesons from decay. Exotic
charmonia could also be produced, and may be behind the slow bump in
inclusive decay.Comment: 6 pages and 2 figure
Perforin-mediated cytotoxicity is critical for surveillance of spontaneous lymphoma
Immune surveillance by cytotoxic lymphocytes against cancer has been postulated for decades, but direct evidence for the role of cytotoxic lymphocytes in protecting against spontaneous malignancy has been lacking. As the rejection of many experimental cancers by cytotoxic T lymphocytes and natural killer cells is dependent on the pore-forming protein perforin (pfp), we examined pfp-deficient mice for increased cancer susceptibility. Here we show that pfp-deficient mice have a high incidence of malignancy in distinct lymphoid cell lineages (T, B, NKT), indicating a specific requirement for pfp in protection against lymphomagenesis. The susceptibility to lymphoma was accentuated by simultaneous lack of expression of the p53 gene, mutations in which also commonly predispose to human malignancies, including lymphoma. In contrast, the incidence and age of onset of sarcoma was unaffected in p53-deficient mice. Pfp-deficient mice were at least 1,000-fold more susceptible to these lymphomas when transplanted, compared with immunocompetent mice in which tumor rejection was controlled by CD8(+) T lymphocytes. This study is the first that implicates direct cytotoxicity by lymphocytes in regulating lymphomagenesis
Decay Constants of (2317) and (2460)
The resonances (2317) and (2460) which are considered to be
the doublet composed of charm and strange quarks have been
discovered recently. Using the method of Rosner which is based on the
factorization hypothesis, we calculate the lower bounds of the decay constants
of these states from the branching ratios of measured by Belle
and Babar.Our result shows that the decay constant of (2460) is about
twice that of (2317) on the contrary to the naive expectation of the
heavy quark symmetry which gives their equality. We show that this big
deviation originates from the large internal motion of quarks inside these
-wave states and that our result is in good accord with the relativistic
quark model calculation
Dynamically generated 1^+ heavy mesons
By using a heavy chiral unitary approach, we study the wave interactions
between heavy vector meson and light pseudoscalar meson. By searching for poles
of the unitary scattering amplitudes in the appropriate Riemann sheets, several
heavy states are found. In particular, a bound state with a mass
of GeV which should be associated with the recently observed
state is obtained. In the same way, a bound state
() with mass of GeV in the bottom sector is predicted.
The spectra of the dynamically generated and states in the
channel are also calculated. One broad state and one narrow state are found in
both the charmed and bottom sectors. The coupling constants and decay widths of
the predicted states are further investigated.Comment: 17 pages, 3 figures. Version accepted for publication in Phys. Lett.
Comment on the new resonances
We propose an explanation of the new resonances observed in decays. We suggest that the data can be explained by the mixing of
conventional p-wave excited mesons with 4-quark states. The narrow
states observed in and are primarily p-wave
states, while the predominantly 4-quark states are shifted above
threshold and should be broad. Ranges for the mixing parameter and
mass of the 4-quark state in this scenario are given. Other experimental
consequences are discussed.Comment: 4 pages, 2 figures. Updated references. To appear in Phys. Lett.
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