Chaotic Combustion in Spark Ignition Engines

We analyse the combustion process in a spark ignition engine using the experimental data of an internal pressure during the combustion process and show that the system can be driven to chaotic behaviour. Our conclusion is based on the observation of unperiodicity in the time series, suitable stroboscopic maps and a complex structure of a reconstructed strange attractor. This analysis can explain that in some circumstances the level of noise in spark ignition engines increases considerably due to nonlinear dynamics of a combustion process.Comment: 5 pages, figures can be obtained from http://archimedes.pol.lublin.pl/~raf/graf/figures.pd

First measurement of the Z→μ+μ−Z\rightarrow \mu^+ \mu^- angular coefficients in the forward region of pppp collisions at s=13\sqrt{s}=13 TeV

The first study of the angular distribution of $\mu^+ \mu^-$ pairs produced in the forward rapidity region via the Drell-Yan reaction $pp \rightarrow \gamma^{*}/Z +X \rightarrow l^+ l^- + X$ is presented, using data collected with the LHCb detector at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.1 $\rm{fb}^{-1}$. The coefficients of the five leading terms in the angular distribution are determined as a function of the dimuon transverse momentum and rapidity. The results are compared to various theoretical predictions of the $Z$-boson production mechanism and can also be used to probe transverse-momentum-dependent parton distributions within the proton

Precision measurement of forward ZZ boson production in proton-proton collisions at s=13\sqrt{s} = 13 TeV

A precision measurement of the $Z$ boson production cross-section at $\sqrt{s} = 13$ TeV in the forward region is presented, using $pp$ collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb$^{-1}$. The production cross-section is measured using $Z\rightarrow\mu^+\mu^-$ events within the fiducial region defined as pseudorapidity $2.020$ GeV/$c$ for both muons and dimuon invariant mass $60<M_{\mu\mu}<120$ GeV/$c^2$. The integrated cross-section is determined to be \begin{equation*} \sigma(Z\rightarrow\mu^+\mu^-) = 195.3 \pm 0.2 \pm 1.5 \pm 3.9~pb, \end{equation*} where the first uncertainty is statistical, the second is systematic, and the third is due to the luminosity determination. The measured results are in agreement with theoretical predictions, including a prediction at next-to-next-to-leading order in perturbative quantum chromodynamics and a prediction with resummation

Study of the lineshape of the χc1(3872)\chi_{c1}(3872) state

A study of the lineshape of the $\chi_{c1}(3872)$ state is made using a data sample corresponding to an integrated luminosity of 3 fb$^{-1}$ collected in pp collisions at center-of-mass energies of 7 and 8 TeV with the LHCb detector. Candidate $\chi_{c1}(3872)$ and $ψ(2S)$ mesons from $b$-hadron decays are selected in the $J/ψπ^+π^-$ decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting between the $\chi_{c1}(3872)$) and $ψ(2S)$ states, $Δm$, and the width of the $\chi_{c1}(3872)$ state, $Γ_{BW}$, are determined to be $\frac {Δm=185.598±0.067±0.068 \, MeV,} {Γ_{BW}=1.39±0.24±0.10 \, MeV}$, where the first uncertainty is statistical and the second systematic. Using a Flatté-inspired model, the mode and full width at half maximum of the lineshape are determined to be $\frac {mode=3871.69_{-0.04-0.13}^{+0.00+0.05} MeV,} {FWHM=0.22_{-0.06-0.13}^{+0.07+0.11} MeV}$. An investigation of the analytic structure of the Flatté amplitude reveals a pole structure, which is compatible with a quasibound $D^0\bar{D}^{*0}$ state but a quasivirtual state is still allowed at the level of 2 standard deviations

Observation of a new Ξb0\Xi_b^0 state

International audienceUsing a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5  fb-1, the observation of a new excited Ξb0 resonance decaying to the Ξb-π+ final state is presented. The state, referred to as Ξb(6227)0, has a measured mass and natural width of m(Ξb(6227)0)=6227.1-1.5+1.4±0.5  MeV and Γ(Ξb(6227)0)=18.6-4.1+5.0±1.4  MeV, where the uncertainties are statistical and systematic. The production rate of the Ξb(6227)0 state relative to that of the Ξb- baryon in the kinematic region 2<η<5 and pT<30  GeV is measured to be fΞb(6227)0fΞb-B(Ξb(6227)0→Ξb-π+)=0.045±0.008±0.004, where B(Ξb(6227)0→Ξb-π+) is the branching fraction of the decay, and fΞb(6227)0 and fΞb- represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed Ξb(6227)- state, along with the mass of the Ξb- baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values