Learning on real robots from experience and simple user feedback

In this article we describe a novel algorithm that allows fast and continuous learning on a physical robot working in a real environment. The learning process is never stopped and new knowledge gained from robot-environment interactions can be incorporated into the controller at any time. Our algorithm lets a human observer control the reward given to the robot, hence avoiding the burden of defining a reward function. Despite the highly-non-deterministic reinforcement, through the experimental results described in this paper, we will see how the learning processes are never stopped and are able to achieve fast robot adaptation to the diversity of different situations the robot encounters while it is moving in several environments.This work was supported by the research grant TIN2009-07737 of the Spanish Ministerio de Economía y Competitividad, and María Barbeito program of the Xunta de Galicia

Simulation of electron transport and secondary emission in a photomultiplier tube and experimental validation

[EN] The electron amplification and transport within a photomultiplier tube (PMT) has been investigated by developing an in-house Monte Carlo simulation code. The secondary electron emission in the dynodes is implemented via an effective electron model and the Modified Vaughan¿s model, whereas the transport is computed with the Boris leapfrog algorithm. The PMT gain, rise time and transit time have been studied as a function of supply voltage and external magnetostatic field. A good agreement with experimental measurements using a Hamamatsu R13408-100 PMT was obtained. The simulations have been conducted following different treatments of the underlying geometry: three-dimensional, two-dimensional and intermediate (2.5D). The validity of these approaches is compared. The developed framework will help in understanding the behavior of PMTs under highly intense and irregular illumination or varying external magnetic fields, as in the case of prompt gamma-ray measurements during pencil-beam proton therapy; and aid in optimizing the design of voltage dividers with behavioral circuit models.This work was supported by Conselleria de Educación, Investigación, Cultura y Deporte (Generalitat Valenciana) under grant numbers CDEIGENT/2019/011 and CDEIGENT/2021/012. P. Martín-Luna is supported by the Ministerio de Universidades (Gobierno de España), Spain under Grant Number FPU20/04958. We thank Hamamatsu (V. Sánchez, D. Castrillo) for technical support and guidance; R. Carrasco (IFIC) and P. Wohlfahrt (Siemens Healthineers) for the CT scanning; D. Calvo and D. Real (KM3net-IFIC) for their LED test platform, the electronics and maintenance services at IFIC for excellent support; and K. Albiol, J. V. Casaña-Copado, A. Gallas Torreira, E. Lemos Cid, G. Pausch, A. Pazos Álvarez, E. Pérez Trigo, S. Rit, A. Ros, J. Roser, J. Stein, J. L. Taín and R. Viegas for useful discussions.Martín-Luna, P.; Esperante, D.; Fernández Prieto, A.; Fuster-Martínez, N.; García Rivas, I.; Gimeno, B.; Ginestar Peiro, D.... (2024). Simulation of electron transport and secondary emission in a photomultiplier tube and experimental validation. Sensors and Actuators A Physical. 365:1-10. https://doi.org/10.1016/j.sna.2023.11485911036

Study of the kinematic dependences of Λ 0b production in pp collisions and a measurement of the Λ 0b → Λ +c π − branching fraction

The kinematic dependences of the relative production rates, fΛ0b/fd, of Λ 0b baryons and B 0 mesons are measured using Λ 0b → Λ +c π − and B¯0 →D+π− decays. The measurements use proton-proton collision data, corresponding to an integrated luminosity of 1 fb−1 at a centre-of-mass energy of 7 TeV, recorded in the forward region with the LHCb experiment. The relative production rates are observed to depend on the transverse momentum, p T, and pseudorapidity, η, of the beauty hadron, in the studied kinematic region 1.5 < p T < 40 GeV/c and 2 < η < 5. Using a previous LHCb measurement of fΛ0b/fd in semileptonic decays, the branching fraction ℬ(Λ 0b → Λ +c π −) = (4.30 ± 0.03 + 0.12− 0.11 ± 0.26 ± 0.21) × 10− 3 is obtained, where the first uncertainty is statistical, the second is systematic, the third is from the previous LHCb measurement of fΛ0b/fd and the fourth is due to the b B¯0 →D+π− branching fraction. This is the most precise measurement of a Λ 0b branching fraction to date.S

Search for the decay D0→π+π−μ+μ−

A search for the D0→π+π−μ+μ− decay, where the muon pair does not originate from a resonance, is performed using proton–proton collision data corresponding to an integrated luminosity of 1.0 fb−1 recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D0→π+π− φ(→μ+μ− ), under the assumption of a phase-space model, is found to be B D0→π + π − μ + μ − /B D0→π + π − φ →μ + μ − < 0.96 at 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D0→π+π−μ+μ− ) < 5.5×10−7 at 90% confidence level. This is the most stringent to date.S

Evidence for the decay X(3872) →ψ(2S)γ

Evidence for the decay mode X(3872) →ψ(2S)γin B+→X(3872)K+decays is found with a sig-nificance of 4.4 standard deviations. The analysis is based on adata sample of proton–proton collisions, corresponding to an integrated luminosity of3fb−1, collected with the LHCb detector, at centre-of-mass energies of 7and8TeV. The ratio of the branching fraction of the X(3872) →ψ(2S)γdecay to that of the X(3872) →J/ψγdecay is measured to be B(X(3872)→ψ(2S)γ) B(X(3872)→J/ψγ) = 2.46± 0.64±0.29, where the first uncertainty is statistical and the second is systematic. The measured value does not support apureD¯ D∗molecular interpretation of the X(3872)state.S

Measurement of indirect CP asymmetries in D0 → K−K+ and D0 → π−π+ decays using semileptonic B decays

Time-dependent CP asymmetries in the decay rates of the singly Cabibbo-suppressed decays D0 → K−K+ and D0 → π−π+ are measured in pp collision data corresponding to an integrated luminosity of 3.0 fb−1 collected by the LHCb experiment. The D0 mesons are produced in semileptonic b-hadron decays, where the charge of the accompanying muon is used to determine the initial state as D0 or D¯0. The asymmetries in effective lifetimes between D0 and D¯0 decays, which are sensitive to indirect CP violation, are determined to be AΓ(K−K+)=(−0.134±0.077−0.026−0.034)%,AΓ(π−π+)=(−0.092±0.145−0.025−0.033)%, where the first uncertainties are statistical and the second systematic. This result is in agreement with previous measurements and with the hypothesis of no indirect CP violation in D0 decays.S

A study of CP violation in B± →DK± and B±→Dπ± decays with D→K0SK±π∓ final states

A first study of CP violation in the decay modes B±→[KS 0 K±π∓] D h±and B±→[KS 0 K∓ π±] D h±, where h labels a K or π meson and D labels a D 0 or D‾ 0 meson, is performed. The analysis uses the LHCb data set collected in pp collisions, corresponding to an integrated luminosity of 3 fb− 1. The analysis is sensitive to the CP-violating CKM phase γ through seven observables: one charge asymmetry in each of the four modes and three ratios of the charge-integrated yields. The results are consistent with measurements of γ using other decay modesS

Measurement of the B+c meson lifetime using B+c→J/ψμ+νμX decays

The lifetime of the B+c meson is measured using semileptonic decays having a J/ψ meson and a muon in the final state. The data, corresponding to an integrated luminosity of 2 fb −1, are collected by the LHCb detector in pp collisions at a centre-of-mass energy of 8 TeV. The measured lifetime is τ=509±8±12 fs, where the first uncertainty is statistical and the second is systematic.S

Search for CP violation in the decay D+→π−π+π+

A search for CP violation in the phase space of the decay D+→π−π+π+ is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment at a centreof- mass energy of 7 TeV. The Dalitz plot distributions for 3.1×106 D+ and D− candidates are compared with binned and unbinned model-independent techniques. No evidence for CP violation is foundS