Description of the Ds∗(2320)D^*_s(2320) resonance as the DπD\pi atom

We discuss the possibility that the recently reported resonance in the $D_s \pi^0$ spectrum can be described in terms of residual $D\pi$ 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 $D_{s1}(2536)$ in radiative transitions to the $D_s^*$.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 $P$-wave $D_s$ and $B_s$ mesons due to coupling to $DK$ and $BK$ channels are calculated in the coupling channel model without fitting parameters. The strong mass shifts down for $0^+$ and ${1^+}'$ states have been obtained, while ${1^+}"$ and $2^+$ states remain almost in situ. The masses of $0^+$ and ${1^+}'$ states of $B_s$ 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 $D_s(2320)$ state recently observed by BaBar in the $D_s^+\pi^0$ channel may be the first of a host of $cq\bar q\bar q$ four-quark states. We give a phenomenological account of the masses and decay modes. The isosinglet $D_s(2320)$ state is the only narrow one, dominated by the observed isospin violating decay and less than $\sim$ 100 keV in width. All other states are expected to decay hadronically. Notable resonances are in doubly charged $D_s^+\pi^+$, $D^+K^+$, wrong pairing $D^+K^-$, and also $D_s^+K^-$, $D\eta$ channels. We propose B decays as searching ground for such 4-quark states, which recoil against $\bar D^{(*)}$ meson from B decay, or $\pi^+$ $\bar D^{(*)}$, $\bar K$ mesons from $\bar B$ decay. Exotic $qc\bar c\bar q$ charmonia could also be produced, and may be behind the slow $J/\psi$ bump in inclusive $B\to J/\psi+X$ 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 DsJ∗D_{sJ}^*(2317) and DsJD_{sJ}(2460)

The resonances $D_{sJ}^*$(2317) and $D_{sJ}$(2460) which are considered to be the $(0^+,1^+)$ 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 $B\to D D_{sJ}$ measured by Belle and Babar.Our result shows that the decay constant of $D_{sJ}$(2460) is about twice that of $D_{sJ}^*$(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 $P$-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 $S$ 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 $1^+$ heavy states are found. In particular, a $D^*K$ bound state with a mass of $2.462\pm0.010$ GeV which should be associated with the recently observed $D_{s1}(2460)$ state is obtained. In the same way, a $B^*{\bar K}$ bound state ($B_{s1}$) with mass of $5.778\pm0.007$ GeV in the bottom sector is predicted. The spectra of the dynamically generated $D_1$ and $B_1$ states in the $I=1/2$ 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 Ds(∗)+π0D_s^{(*)+} \pi^0 resonances

We propose an explanation of the new resonances observed in $D_s^{(*)+} \pi^0$ decays. We suggest that the data can be explained by the mixing of conventional p-wave excited $D_s^+$ mesons with 4-quark states. The narrow states observed in $D_s^+ \pi^0$ and $D_s^{*+}\pi^0$ are primarily p-wave $D_{sJ}^{*}$ states, while the predominantly 4-quark states are shifted above $D^{(*)} K$ 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.