LHCb

Abstract:

The polarization of photons produced in radiative B_{s}^{0} decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3  fb^{-1} at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B_{s}^{0}→ϕγ decay rate is conducted to determine the parameter A^{Δ}, which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of A^{Δ}=-0.98_{-0.52}^{+0.46}_{-0.20}^{+0.23} is measured. This result is consistent with the standard model prediction within 2 standard deviations.

Abstract:

+The production of tt‾, W+bb‾ and W+cc‾ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fb −1 . The W bosons are reconstructed in the decays W→ℓν, where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.

Abstract:

Differences in the behaviour of matter and antimatter have been observed in K and B meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as CP violation. Here, using data from the LHCb experiment at the Large Hadron Collider, we search for CP-violating asymmetries in the decay angle distributions of Λ b 0 baryons decaying to pπ - π + π - and pπ - K + K - final states. These four-body hadronic decays are a promising place to search for sources of CP violation both within and beyond the standard model of particle physics. We find evidence for CP violation in Λ b 0 to pπ - π + π - decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for CP violation in the baryon sector.

Abstract:

The first observation of the rare decay B0s to φπ+π- and evidence for B0 to φπ+π- are reported, using pp collision data recorded by the LHCb detector at centre-of-mass energies √s = 7 and 8 TeV, corresponding to an integrated luminosity of 3fb^-1. The branching fractions in the π+π- invariant mass range 400 < m(π+π-) < 1600 MeV/c2 are [3.48 ± 0.23 ± 0.17 ± 0.35] X 10^-6 and [1.82 ± 0.25 ± 0.41 ± 0.14] X 10^-7 for B0s to φπ+π- and B0 to φπ+π- respectively, where the uncertainties are statistical, systematic and from the normalisation mode B0s to φπ+π-. A combined analysis of the π+π- mass spectrum and the decay angles of the final-state particles identifies the exclusive decays B0s to φf0(980), B0s to φf2(1270), and B0s →ϕρ0 with branching fractions of [1.12 ± 0.16^+0.09-0.08 ± 0.11] X 10^-6, [0.61 ± 0.13^+0.12-0.05 ± 0.06] X 10^-6 and [2.7 ± 0.7 ± 0.2 ± 0.2] X 10^-7, respectively.

Abstract:

© 2016 Equation (5) contained an error; the correct expression is: (5) Yi=HK3π(Ki+(rDK3π)2K−i−2rDK3πKiK−iRK3π[cicos⁡δDK3π−sisin⁡δDK3π]). This correction leads to changes in the results and associated correlations for the fit to the CLEO-c observables reported in Tables 6 and 7, respectively. The reduced χ2 of this fit is 29.5/33. Changes are also observed in the Δχ2 scans presented in Fig. 3. When performing an updated global fit to the CLEO-c and LHCb observables a reduced χ2 of 33.5/36 is obtained. Changes occur to the values reported in Tables 9 and 10, and the scans presented in Fig. 5. In addition a typographical error was introduced into Eq. (1). The correct expression is(1)RK3πe−iδDK3π=∫AK−π+π+π−⁎(x)AK+π−π+π−(x)dxAK−π+π+π−AK+π−π+π−. The results presented in the paper are unaffected by this error.