Study of $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ → J/ψπ+π−K+K− decays

Abstract

The decays $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → J/ψπ+π−K+K− are studied using a data set corresponding to an integrated luminosity of 9 fb−1, collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV. The decays $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → $$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 and $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 → χc1(3872)K+K−, where the K+K−pair does not originate from a ϕ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χc1(3872)ϕ, $$ \mathrm{J}/{\uppsi \mathrm{K}}^{\ast 0}{\overline{\mathrm{K}}}^{\ast 0} $$ J / ψK ∗ 0 K ¯ ∗ 0 , ψ(2S)ϕ and χc1(3872)K+K− states are reported. A structure, denoted as X(4740), is observed in the J/ψϕ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be$$ {\displaystyle \begin{array}{c}{m}_{\mathrm{X}(4740)}=4741\pm 6\pm 6\kern0.5em \mathrm{MeV}/{c}^2,\\ {}{\Gamma}_{\mathrm{X}(4740)}=53\pm 15\pm 11\kern0.5em \mathrm{MeV},\end{array}} $$ m X 4740 = 4741 ± 6 ± 6 MeV / c 2 , Γ X 4740 = 53 ± 15 ± 11 MeV , where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the $$ {\mathrm{B}}_{\mathrm{s}}^0 $$ B s 0 meson is performed and gives a value of$$ {m}_{{\mathrm{B}}_{\mathrm{s}}^0}=5366.98\pm 0.07\pm 0.13\kern0.5em \mathrm{MeV}/{c}^2. $$ m B s 0 = 5366.98 ± 0.07 ± 0.13 MeV / c 2 .

Observation of an exotic narrow doubly charmed tetraquark

“…• Difference in detector resolution due to imperfect modelling: a correction factor of 1.05 for the resolution is applied for the default fit to account for such a difference. This factor was studied for several other decays measured with the LHCb detector and found to lie between 1.0 and 1.1 [29,91,92,[119][120][121]. For decays with relatively low-momentum tracks, this factor is close to 1.05.…”

“…A follow-up study [90] investigates the underlying nature of the T + cc state, expanding on the modelling of the signal shape and determining its physical properties. The detector resolution is modelled by the sum of two Gaussian functions with a common mean, where the additional parameters are taken from simulation (see Methods) with corrections applied [29,91,92]. The root mean square of the resolution function is around 400 keV/c 2 .…”

Study of the doubly charmed tetraquark $T_{cc}^+$

“…Quark content X 0 (2900), X 1 (2900) [21,22] cdus χ c1 (3872) [6] ccqq Z c (3900) [23], Z c (4020) [24,25], Z c (4050) [26], X(4100) [27], Z c (4200) [28], Z c (4430) [29][30][31][32], R c0 (4240) [31] ccud Z cs (3985) [33], Z cs (4000), Z cs (4220) [34] ccus χ c1 (4140) [35][36][37][38], χ c1 (4274), χ c0 (4500), χ c0 (4700) [38], X(4630), X(4685) [34], X(4740) [39] ccss X(6900) [14] cccc Z b (10610), Z b (10650) [40] bbud P c (4312) [41], P c (4380) [42], P c (4440), P c (4457) [41], P c (4357) [43] ccuud P cs (4459) [44] ccuds analogous to an antiquark, and as a result the Q 1 Q 2 q1 q2 system has similar degrees of freedom for its light quarks as an antibaryon with a single heavy quark, e.g. the Λ − c or Λ 0 b antibaryons.…”

“…The detector mass resolution, R, is modelled with the sum of two Gaussian functions with a common mean, and parameters taken from simulation, see Methods. The widths of the Gaussian functions are corrected by a factor of 1.05, that accounts for a small residual difference between simulation and data [39,104,105]. The root mean square of the resolution function is around 400 keV/c 2 .…”

“…A correction factor of 1.05 is applied to account for known discrepancies in modelling the detector resolution in simulation. This factor was studied for different decays [39,104,105,[117][118][119] and found to lie between 1.0 and 1.1. For decays with relatively low momentum tracks, this factor is close to 1.05, which is the nominal value used in this analysis.…”