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$DK$ and $D^* K$ scattering near threshold

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 نشر من قبل Christian B. Lang
 تاريخ النشر 2014
  مجال البحث
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We study the three $D_s$ quantum channels $J^P = 0^+$, $1^+$ and $2^+$ where experiments have identified the charm-strange states $D^*_{s0} (2317)$, $D_{s1}(2460)$, $D_{s1}(2536)$ near the $DK$ and $D^*K$ thresholds, and $D^*_{s2}(2573)$. We consider correlation functions for sets of $overline q q$ operators and, for $J^P = 0^+$, $1^+$, also the $DK$ and $D^*K$ meson-meson interpolators and determine for these cases values of the elastic scattering amplitude. Constructing the full set of correlators requires propagators which connect any pair of lattice sites. For one ensemble of gauge configurations ($32^3times 64$, $m_piapprox 156$ MeV) a stochastic distillation variant is employed and for another ensemble ($16^3times 32$, $m_piapprox 266$ MeV) we use the full distillation method. Both, $D^*_{s0} (2317)$ and $D_{s1}(2460)$, are found as bound states below threshold, whereas $D_{s1}(2536)$, and $D^*_{s2}(2573)$ are identified as narrow resonances close to the experimental masses.



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$D_s$ mesons are studied in three quantum channels ($J^P=0^+$, $1^+$ and $2^+$), where experiments have identified the very narrow $D_{s0}^*(2317)$, $D_{s1}(2460)$ and narrow $D_{s1}(2536)$, $D_{s2}^*(2573)$. We explore the effect of nearby $DK$ and $D^*K$ thresholds on the subthreshold states using lattice QCD. Our simulation is done on two very different ensembles of gauge configurations (2 or 2+1 dynamical quarks, Pion mass of 266 or 156 MeV, lattice size $16^3times 32$ or $32^3times 64$). In addition to $bar{q}q$ operators we also include meson-meson interpolators in the correlation functions. This clarifies the identification of the states above and below the scattering thresholds. The ensemble with $m_pi simeq 156~$MeV renders the $D_{s1}(2460)$ as a strong interaction bound state 44(10)MeV below $D^*K$ threshold, which is in agreement with the experiment. The $D_{s0}^*(2317)$ is found 37(17)MeV below $DK$ threshold, close to experiment value of 45MeV. The narrow resonances $D_{s1}(2536)$ and $D_{s2}^*(2573)$ are also found close to the experimental masses.
Using the Fixed Center Approximation to Faddeev equations we have investigated the $DKK$ and $DKbar{K}$ three-body systems, considering that the $D^*_{s0}(2317)$ acts as the heavy cluster in both cases, generated from the $DK$ interaction in isospin 0. For the $DKbar{K}$ system we have found evidence of a state with $I(J^P)=1/2(0^-)$ and mass about $2833 - 2858$ MeV, above the threshold of $D^*_{s0}(2317)bar{K}$. Our results indicate that this state is dominated by a $Df_0(980)$ component, then it could be searched for in the $pi pi D$ invariant mass. On the other hand, no clear evidence related to a state from the $DKK$ interaction is found.
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