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First evidence of a structure in the J/ψΛ invariant mass distribution is obtained from an amplitude analysis of Ξb-→J/ψΛK- decays. The observed structure is consistent with being due ...to a charmonium pentaquark with strangeness with a significance of 3.1σ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be 4458.8±2.9-1.1+4.7MeV and 17.3±6.5-5.7+8.0MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited Ξ- states, Ξ1690- and Ξ1820-, are seen for the first time in a Ξb- decay, and their masses and widths are measured with improved precision. The analysis is performed using pp collision data corresponding to a total integrated luminosity of 9 fb-1, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.
A study of the lineshape of the χc1 ( 3872 ) state is made using a data sample corresponding to an integrated luminosity of 3 fb−1 collected in p p collisions at center-of-mass energies of 7 and ...8 TeV with the LHCb detector. Candidate χc1 ( 3872 ) and ψ ( 2S ) mesons from b -hadron decays are selected in the J / ψ π+ π− decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting between the χc1 ( 3872 ) and ψ ( 2S ) states, Δm, and the width of the χc1 ( 3872 ) state, ΓBW, are determined to be ..., where the first uncertainty is statistical and the second systematic. Using a Flatté-inspired model, the mode and full width at half maximum of the lineshape are determined to be ... . An investigation of the analytic structure of the Flatté amplitude reveals a pole structure, which is compatible with a quasibound D0 D*0 state but a quasivirtual state is still allowed at the level of 2 standard deviations. (ProQuest: ... denotes formulae omited.).
The first observation of exotic states with a new quark content ccus decaying to the J/Psi K+ final state is reported with high significance from an amplitude analysis of the B+-> J/ Psi phi K+ ...decay. The analysis is carried out using proton-proton collision data corresponding to a total integrated luminosity of 9 fb- 1 collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The most significant state, Z(cs)(4000)+, has a mass of 4003 +/- 6 (-14) (+4) MeV, a width of 131 +/- 15 +/- 26 MeV, and spin parity J(P) = 1(+), where the quoted uncertainties are statistical and systematic, respectively. A new 1(+) X(4685) state decaying to the J/Psi phi final state is also observed with high significance. In addition, the four previously reported J/Psi phi states are confirmed and two more exotic states, Z(cs) (4220) (+) and X(4630), are observed with significance exceeding 5 standard deviations.
The production of χc1(3872) and ψ(2S) hadrons is studied as a function of charged particle multiplicity in p p collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated ...luminosity of 2 fb−1. For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of χc1(3872) to ψ(2S) cross sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the χc1(3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the χc1(3872) state are discussed.
Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and ...mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the (DD0)-D-0 pi(+) mass spectrum just below the D*+D-0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T-cc(+), tetraquark with a quark content of cc (u) over bar(d) over bar and spin-parity quantum numbers J(P) =1(+). Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*(+) mesons is consistent with the observed D-0 pi(+) mass distribution. To analyse the mass of the resonance and its coupling to the DID system, a dedicated model is developed under the assumption of an isoscalar axial-vector T-cc(+), state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T-cc(+), state. In addition, an unexpected dependence of the production rate on track multiplicity is observed.
The TIMESPOT project aims at the construction of a mini-tracker demonstrator implementing both high space and time resolutions at the single pixel level. The pixels have a pitch of 55 × 55 μm2. ...Specified time resolution is equal or better than 50 ps. Developed sensors are based both on 3D silicon and diamond technologies, whose layout and fabrication process have been suitably optimized for best time resolution. Read-out pixel electronics is being developed in 28-nm CMOS technology. The first batch of 3D silicon sensors, containing several test structures based on different geometries of the electrodes, has been delivered in June 2019 and has been tested against its timing performance both under laser and minimum ionizing particle beams. In the present paper, the output of these starting measurements is presented. The sensors show very good timing performance, having σ¡30 ps (sigma), although operated with non-optimized front-end electronics and in noisy environment. These results represent an important step forward in the development of pixels with timing operating at extremely high interaction rates and fluences, as required in the next generation of upgraded colliders.
•A crucial challenge about future vertex detectors consists in realizing pixel with timing capabilities.•In this respect, we need sensors and electronics having at the same time the following requirements: space resolutions of O(10 μm), time resolutions below 50 ps, radiation resistance ¿ 1016 1 MeV neutron equivalent per cm2.•We have developed and fabricated dedicated fast silicon sensors in 3D technology with a pitch of 55 μm.•They have been proved to have time resolutions below 30 ps.
Observation of a new Ξb0 state Ackernley, T.; Alessio, F.; Amato, S. ...
Physical review. D,
01/2021, Letnik:
103, Številka:
1
Journal Article
Recenzirano
Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5 fb-1, the observation of a new excited $Ξ^{0}_{b}$ resonance decaying to ...the $Ξ^{-}_{b}$$π$+ final state is presented. The state, referred to as $Ξ_b$(6227)0, has a measured mass and natural width of $m$$(Ξ_b$(6227)0) = $6227.1^{+1.4}_{-1.5}$ ± 0.5 MeV and Γ($Ξ_b$(6227)0) = $18.6^{+5.0}_{-4.1}$ ± 1.4 MeV, where the uncertainties are statistical and systematic. The production rate of the $Ξ_b$(6227)0 state relative to that of the $Ξ^{-}_{b}$ baryon in the kinematic region 2 < $η$ < 5 and pT < 30 GeV is measured to be $\frac{f_{Ξ_b}(6227)^0}{f_{Ξ_b^-}}$ $\mathscr{B}$($Ξ_b$(6227)0 → $Ξ^-_b$$π^+$) = 0.045 ± 0.008 ± 0.004; where $\mathscr{B}$($Ξ_b$(6227)0 → $Ξ^-_b$$π^+$) is the branching fraction of the decay, and $f$$Ξ$$_{b}$$_{(6227)^0}$ and $f$$Ξ$$_{b}^-$ represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed $Ξ_b$$(6227)^-$ state, along with the mass of the $Ξ^{-}_{b}$ baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.
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