Publications by authors named "T Ackernley"

17 Publications

Angular Analysis of the B^{+}→K^{*+}μ^{+}μ^{-} Decay.

Phys Rev Lett 2021 Apr;126(16):161802

Laboratoire Leprince-ringuet (llr), Palaiseau, France.

We present an angular analysis of the B^{+}→K^{*+}(→K_{S}^{0}π^{+})μ^{+}μ^{-} 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}μ^{+}μ^{-} decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.
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http://dx.doi.org/10.1103/PhysRevLett.126.161802DOI Listing
April 2021

Observation of a New Excited D_{s}^{+} Meson in B^{0}→D^{-}D^{+}K^{+}π^{-} Decays.

Phys Rev Lett 2021 Mar;126(12):122002

Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France.

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^{+}π^{-} decay is studied. A new excited D_{s}^{+} meson is observed decaying into the D^{+}K^{+}π^{-} 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, Γ_{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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http://dx.doi.org/10.1103/PhysRevLett.126.122002DOI Listing
March 2021

Observation of Multiplicity Dependent Prompt χ_{c1}(3872) and ψ(2S) Production in pp Collisions.

Phys Rev Lett 2021 Mar;126(9):092001

Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France.

The production of χ_{c1}(3872) and ψ(2S) hadrons is studied as a function of charged particle multiplicity in pp 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 χ_{c1}(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 χ_{c1}(3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the χ_{c1}(3872) state are discussed.
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http://dx.doi.org/10.1103/PhysRevLett.126.092001DOI Listing
March 2021

Measurement of CP Violation in the Decay B^{+}→K^{+}π^{0}.

Phys Rev Lett 2021 Mar;126(9):091802

Physik-Institut, Universität Zürich, Zürich, Switzerland.

A measurement of CP violation in the decay B^{+}→K^{+}π^{0} is reported using data corresponding to an integrated luminosity of 5.4  fb^{-1} collected with the LHCb experiment at a center-of-mass energy of sqrt[s]=13  TeV. The CP asymmetry is measured to be 0.025±0.015±0.006±0.003, where the uncertainties are statistical, systematic, and due to an external input. This is the most precise measurement of this quantity. It confirms and significantly enhances the observed anomalous difference between the direct CP asymmetries of the B^{0}→K^{+}π^{-} and B^{+}→K^{+}π^{0} decays, known as the Kπ puzzle.
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http://dx.doi.org/10.1103/PhysRevLett.126.091802DOI Listing
March 2021

Proton path reconstruction for pCT using neural networks.

Phys Med Biol 2021 Mar 18. Epub 2021 Mar 18.

FBK, Trento, 38100, ITALY.

The Most Likely Path formalism (MLP) is widely established as the most statistically precise method for proton path reconstruction in proton computed tomography (pCT). However, while this method accounts for small-angle Multiple Coulomb Scattering (MCS) and energy loss, inelastic nuclear interactions play an influential role in a significant number of proton paths. By applying cuts based on energy and direction, tracks influenced by nuclear interactions are largely discarded from the MLP analysis. In this work we propose a new method to estimate the proton paths based on a Deep Neural Network (DNN). Through this approach, estimates of proton paths equivalent to MLP predictions have been achieved in the case where only MCS occurs, together with an increased accuracy when nuclear interactions are present. Moreover, our tests indicate that the DNN algorithm can be considerably faster than the MLP algorithm.
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http://dx.doi.org/10.1088/1361-6560/abf00fDOI Listing
March 2021