LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of a New Excited D-s(+) Meson in B-0 -> D- D+ K+ pi(-) Decays. Phys. Rev. Lett., 126(12), 122002–11pp.
Abstract: Using pp collision data corresponding to an integrated luminosity of 5.4 fb(-1) collected with the LHCb detector at a center-of-mass energy of 13 TeV, the B-0 -> D- D+ K+ pi(-) decay is studied. A new excited D-s(+) meson is observed decaying into the D+K+pi(-) final state with large statistical significance. The pole mass and width, and the spin parity of the new state are measured with an amplitude analysis to be m(R) = 2591 +/- 6 +/- 7 MeV, Gamma(R) = 89 +/- 16 +/- 12 MeV, and J(P) = 0(-), where the first uncertainty is statistical and the second systematic. Fit fractions for all components in the amplitude analysis are also reported. The new resonance, denoted as D-s0(2590)(+), is a strong candidate to be the D-s(2(1)S(0))(+) state, the radial excitation of the pseudoscalar ground-state D-s(+) meson.
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Aiola, S., Bandiera, L., Cavoto, G., De Benedetti, F., Fu, J., Guidi, V., et al. (2021). Progress towards the first measurement of charm baryon dipole moments. Phys. Rev. D, 103(7), 072003–15pp.
Abstract: Electromagnetic dipole moments of short-lived particles are sensitive to physics within and beyond the Standard Model of particle physics but have not been accessible experimentally to date. To perform such measurements it has been proposed to exploit the spin precession of channeled particles in bent crystals at the LHC. Progress that enables the first measurement of charm baryon dipole moments is reported. In particular, the design and characterization on beam of silicon and germanium bent crystal prototypes, the optimization of the experimental setup, and advanced analysis techniques are discussed. Sensitivity studies show that first measurements of Lambda(+)(c) and Xi(+)(c) baryon dipole moments can he performed in two years of data taking with an experimental setup positioned upstream of the LHCb detector.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Angular Analysis of the B+ -> K*(+)mu(+) mu(-) Decay. Phys. Rev. Lett., 126(16), 161802–11pp.
Abstract: We present an angular analysis of the B+ -> K*(+)(-> K-S(0)pi(+))mu(+) mu(-) decay using 9 fb(-1) of pp collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B-0 -> K*(0)mu(+)mu(-) decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Measurement of the prompt-production cross-section ratio sigma(chi(c2))/sigma(chi(c1)) in pPb collisions at root s(NN)=8.16 TeV. Phys. Rev. C, 103(6), 064905–10pp.
Abstract: This article reports the first measurement of prompt chi(c1) and chi(c2) charmonium production in nuclear collisions at Large Hadron Collider energies. The cross-section ratio sigma(chi(c2))/sigma(chi(c1)) is measured in pPb collisions at root s(NN) = 8.16 TeV, collected with the LHCb experiment. The chi(c1,2) states are reconstructed via their decay to a J/psi meson, subsequently decaying into a pair of oppositely charged muons, and a photon, which is reconstructed in the calorimeter or via its conversion in the detector material. The cross-section ratio is consistent with unity in the two considered rapidity regions. Comparison with a corresponding cross-section ratio previously measured by the LHCb Collaboration in pp collisions suggests that chi(c1) and chi(c2) states are similarly affected by nuclear effects occurring in pPb collisions.
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LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Observation of New Resonances Decaying to J=Psi K plus and J=Psi phi. Phys. Rev. Lett., 127(8), 082001–11pp.
Abstract: 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.
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