Entropy production and Kullback-Leibler divergence between stationary trajectories of discrete systems

The irreversibility of a stationary time series can be quantified using the Kullback-Leibler divergence (KLD) between the probability to observe the series and the probability to observe the time-reversed series. Moreover, this KLD is a tool to estimate entropy production from stationary trajectories since it gives a lower bound to the entropy production of the physical process generating the series. In this paper we introduce analytical and numerical techniques to estimate the KLD between time series generated by several stochastic dynamics with a finite number of states. We examine the accuracy of our estimators for a specific example, a discrete flashing ratchet, and investigate how close is the KLD to the entropy production depending on the number of degrees of freedom of the system that are sampled in the trajectories.Comment: 14 pages, 7 figure

First evidence of direct CP violation in charmless two-body decays of Bs0 mesons

Using a data sample corresponding to an integrated luminosity of 0.35  fb-1 collected by LHCb in 2011, we report the first evidence of CP violation in the decays of Bs0 mesons to K±π∓ pairs, ACP(Bs0→Kπ)= 0.27±0.08(stat)±0.02(syst), with a significance of 3.3σ. Furthermore, we report the most precise measurement of CP violation in the decays of B0 mesons to K±π∓ pairs, ACP(B0→Kπ)=-0.088±0.011(stat)±0.008(syst), with a significance exceeding 6σ

Strong constraints on the rare decays Bs0 -> μ+μ- and B0 -> μ+μ-

A search for Bs0→μ+μ- and B0→μ+μ- decays is performed using 1.0  fb-1 of pp collision data collected at √s=7  TeV with the LHCb experiment at the Large Hadron Collider. For both decays, the number of observed events is consistent with expectation from background and standard model signal predictions. Upper limits on the branching fractions are determined to be B(Bs0→μ+μ-)<4.5(3.8)×10-9 and B(B0→μ+μ-)<1.0(0.81)×10-9 at 95% (90%) confidence level

Measurement of b-hadron branching fractions for two-body decays into charmless charged hadrons

Based on data corresponding to an integrated luminosity of 0.37 fb−1 collected by the LHCb experiment in 2011, the following ratios of branching fractions are measured: B(B0→π+π−)/B(B0→K+π−)=0.262±0.009±0.017,(fs/fd)⋅B(B0s→K+K−)/B(B0→K+π−)=0.316±0.009±0.019,(fs/fd)⋅B(B0s→π+K−)/B(B0→K+π−)=0.074±0.006±0.006,(fd/fs)⋅B(B0→K+K−)/B(B0s→K+K−)=0.018+0.008−0.007±0.009,(fs/fd)⋅B(B0s→π+π−)/B(B0→π+π−)=0.050+0.011−0.009±0.004,B(Λ0b→pπ−)/B(Λ0b→pK−)=0.86±0.08±0.05, where the first uncertainties are statistical and the second systematic. Using the current world average of B(B0→K+π−) and the ratio of the strange to light neutral B meson production f s /f d measured by LHCb, we obtain: B(B0→π+π−)=(5.08±0.17±0.37)×10−6,B(B0s→K+K−)=(23.0±0.7±2.3)×10−6,B(B0s→π+K−)=(5.4±0.4±0.6)×10−6,B(B0→K+K−)=(0.11+0.05−0.04±0.06)×10−6,B(B0s→π+π−)=(0.95+0.21−0.17±0.13)×10−6. The measurements of B(B0s→K+K−) , B(B0s→π+K−) and B(B0→K+K−) are the most precise to date. The decay mode B0s→π+π− is observed for the first time with a significance of more than 5σ

Measurement of relative branching fractions of B decays to ψ(2S) and J/ψ mesons

The relative rates of B-meson decays into J/ψ and ψ(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions (B) are measured to be B(B +→ψ(2S)K + ) B(B+→J/ψK+) = 0.594±0.006(stat)±0.016(syst)±0.015(Rψ), B(B0→ψ(2S)K ∗0) B(B0→J/ψK∗0) = 0.476±0.014(stat)±0.010(syst)±0.012(Rψ), B(B0 s →ψ(2S)φ) B(B0 s →J/ψφ) = 0.489±0.026(stat)±0.021(syst)±0.012(Rψ), where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ + μ −. 1 Introductio

Search for the rare decays B0s→μ+μ− and B0→μ+μ−

A search for the decays and B0→μ+μ− is performed with 0.37 fb−1 of pp collisions at collected by the LHCb experiment in 2011. The upper limits on the branching fractions are and B(B0→μ+μ−)<3.6×10−9 at 95% confidence level. A combination of these results with the LHCb limits obtained with the 2010 dataset leads to and B(B0→μ+μ−)<3.2×10−9 at 95% confidence level

Searches for Majorana neutrinos in B-decays

Searches for heavy Majorana neutrinos in B- decays in final states containing hadrons plus a μ-μ- pair have been performed using 0.41  fb-1 of data collected with the LHCb detector in proton-proton collisions at a center-of-mass energy of 7 TeV. The D+μ-μ- and D*+μ-μ- final states can arise from the presence of virtual Majorana neutrinos of any mass. Other final states containing π+, Ds+, or D0π+ can be mediated by an on-shell Majorana neutrino. No signals are found and upper limits are set on Majorana neutrino production as a function of mass, and also on the B- decay branching fractions

Measurements of Bc+ production and mass with the Bc+ -> J/Ψπ+ decay

Measurements of B-c(+) production and mass are performed with the decay mode B-c(+) -> J/psi pi(+) using 0.37 fb(-1) of data collected in pp collisions at root s = 7 TeV by the LHCb experiment. The ratio of the production cross section times branching fraction between the B-c(+) -> J/psi pi(+) and the B+ -> J/psi K+ decays is measured to be (0.68 +/- 0.10(stat) +/- 0.03(syst) +/- 0.05(lifetime))% for B-c(+) and B+ mesons with transverse momenta p(T) > 4 GeV/c and pseudorapidities 2.5 < eta < 4.5. The B-c(+) mass is directly measured to be 6273.7 +/- 1.3(stat) +/- 1.6(syst) MeV/c(2), and the measured mass difference with respect to the B+ meson is M(B-c(+)) - M(B+) = 994.6 +/- 1.3(stat) +/- 0.6(syst) MeV/c(2)

Measurement of the forward energy flow in pp collisions at √s=7 TeV

The energy flow created in pp collisions at √s = 7 TeV is studied within the pseudorapidity range 1.9 < η < 4.9 with data collected by the LHCb experiment. The measurements are performed for inclusive minimum-bias interactions, hard scattering processes and events with an enhanced or suppressed diffractive contribution. The results are compared to predictions given by PYTHIA-based and cosmic-ray event generators, which provide different models of soft hadronic interactions