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Register a new user$D_{s}$ mesons with $DK$ and $D^{*}K$ scattering near threshold
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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.
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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.
We present results for the $SU(3)$ breaking ratios of decay constants $f_{D_s}/f_D$ and $f_{B_s}/f_B$ and - for the first time with physical pion masses - the ratio of bag parameters $B_{B_s}/B_{B_d}$, as well as the ratio $xi$, forming the ratio of the nonpeturbative contributions to neutral $B_{(s)}$ meson mixing. Our results are based on Lattice QCD simulations with chirally symmetric 2+1 dynamical flavors of domain wall fermions. Eight ensembles at three different lattice spacing in the range $a = 0.11 - 0.07,mathrm{fm}$ enter the analysis two of which feature physical light quark masses. Multiple heavy quark masses are simulated ranging from below the charm quark mass to half the bottom quark mass. The $SU(3)$ breaking ratios display a very benign heavy mass behaviour allowing for extrapolation to the physical bottom quark mass. The results in the continuum limit including all sources of systematic errors are $f_{D_s}/f_D = 1.1740(51)_mathrm{stat}(^{+68}_{-68})_mathrm{sys}$, $f_{B_s}/f_B = 1.1949(60)_mathrm{stat}(^{+hphantom{0}95}_{-175})_mathrm{sys}$, $B_{B_s}/B_{B_d} = 0.9984(45)_mathrm{stat}(^{+80}_{-63})_mathrm{sys}$ and $xi = 1.1939(67)_mathrm{stat}(^{+hphantom{0}95}_{-177})_mathrm{sys}$. Combining these with experimentally measured values we extract the ratios of CKM matrix elements $|V_{cd}/V_{cs}| = 0.2164(57)_mathrm{exp}(^{+12}_{-12})_mathrm{lat}$ and $|V_{td}/V_{ts}| = 0.20329(41)_mathrm{exp}(^{+162}_{-301})_mathrm{lat}$.
The scalar meson $D_{s0}^*(2317)$ is found 37(17)MeV below DK threshold in a lattice simulation of the $J^P=0^+$ channel using, for the first time, both DK as well as $bar sc$ interpolating fields. The simulation is done on $N_f=2+1$ gauge configurations with $m_pisimeq 156 $MeV, and the resulting $M_{D_{s0}^*}-tfrac{1}{4}(M_{D_s}+3M_{D_s^*})=266(16)$ MeV is close to the experimental value 241.5(0.8)MeV. The energy level related to the scalar meson is accompanied by additional discrete levels due to DK scattering states. The levels near threshold lead to the negative DK scattering length $a_0=-1.33(20)$ fm that indicates the presence of a state below threshold.
The recently discovered $D_{s0}(2590)$ state by the LHCb collaboration was regarded as the first excited state of $^1S_{0}$ charmed-strange meson. Its mass is, however, lower than the Godfrey-Isgur quark model prediction by about 80 MeV. In this work, we take into account the $D^{ast}K$ contribution to the bare $cbar{s}$ state, and show that the coupled-channel interaction induces an 88 MeV shift with respect to the conventional quark model $cbar{s}$ state, which is much closer to the experimental mass. Our study shows that in addition to $S$-wave, $P$-wave coupled-channel interactions also play a role for hadrons located close to two-hadron thresholds. We further scrutinize the unquenched quark model results with a model independent approach. It is shown that the two-body $D^*K$ decay width is proportional to the weight of the $D^*K$ component. To saturate the experimental total decay width with the $D^*K$ partial decay width we need a weight of about 60% while to reproduce the unquenched quark model result a weight of about 5% is needed. Therefore, we encourage future experimental studies on the two-body $D^*K$ partial decay of $D_{s0}(2590)$.
We present the first lattice QCD study of coupled isoscalar $pipi,Koverline{K},etaeta$ $S$- and $D$-wave scattering extracted from discrete finite-volume spectra computed on lattices which have a value of the quark mass corresponding to $m_pisim391$ MeV. In the $J^P=0^+$ sector we find analogues of the experimental $sigma$ and $f_0(980)$ states, where the $sigma$ appears as a stable bound-state below $pipi$ threshold, and, similar to what is seen in experiment, the $f_0(980)$ manifests itself as a dip in the $pipi$ cross section in the vicinity of the $Koverline{K}$ threshold. For $J^P=2^+$ we find two states resembling the $f_2(1270)$ and $f_2(1525)$, observed as narrow peaks, with the lighter state dominantly decaying to $pipi$ and the heavier state to $Koverline{K}$. The presence of all these states is determined rigorously by finding the pole singularity content of scattering amplitudes, and their couplings to decay channels are established using the residues of the poles.
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