Constrained pre-equalization accounting for multi-path fading emulated using large RC networks: applications to wireless and photonics communications

Multi-path propagation is modelled assuming a multi-layer RC network with randomly allocated resistors and capacitors to represent the transmission medium. Due to frequency-selective attenuation, the waveforms associated with each propagation path incur path-dependent distortion. A pre-equalization procedure that takes into account the capabilities of the transmission source as well as the transmission properties of the medium is developed. The problem is cast within a Mixed Integer Linear Programming optimization framework that uses the developed nominal RC network model, with the excitation waveform customized to optimize signal fidelity from the transmitter to the receiver. The objective is to match a Gaussian pulse input accounting for frequency regions where there would be pronounced fading. Simulations are carried out with different network realizations in order to evaluate the sensitivity of the solution with respect to changes in the transmission medium mimicking the multi-path propagation. The proposed approach is of relevance where equalization techniques are difficult to implement. Applications are discussed within the context of emergent communication modalities across the EM spectrum such as light percolation as well as emergent indoor communications assuming various modulation protocols or UWB schemes as well as within the context of space division multiplexing

First observation of a doubly charged tetraquark and its neutral partner

A combined amplitude analysis is performed for the decays $B^0 \rightarrow \overline{D}^0 D^+_s\pi^-$ and $B^+\rightarrow D^- D^+_s\pi^+$, which are related by isospin symmetry. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13$\,\rm{TeV}$. The full data sample corresponds to an integrated luminosity of 9$\,\rm{fb^{-1}}$. Two new resonant states with masses of $2.908\pm0.011\pm0.020\,\rm{GeV}$ and widths of $0.136\pm0.023\pm0.011\,\rm{GeV}$ are observed, which decay to $D^+_s\pi^+$ and $D^+_s\pi^-$ respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content $[c\bar{s}u\bar{d}]$, and the latter state is a neutral tetraquark composed of $[c\bar{s}\bar{u}d]$ quarks. Both states are found to have spin-parity $0^+$, and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-026.html (LHCb public pages

Search for rare decays of D0 mesons into two muons

A search for the very rare D 0 → μ + μ − decay is performed using data collected by the LHCb experiment in proton-proton collisions at √ s = 7 , 8, and 13 TeV, corresponding to an integrated luminosity of 9     fb − 1 . The search is optimized for D 0 mesons from D * + → D 0 π + decays but is also sensitive to D 0 mesons from other sources. No evidence for an excess of events over the expected background is observed. An upper limit on the branching fraction of this decay is set at B ( D 0 → μ + μ − ) < 3.1 × 10 − 9 at a 90% C.L. This represents the world’s most stringent limit, constraining models of physics beyond the standard model

Measurement of the ratios of branching fractions R(D*) and R(D0)

The ratios of branching fractions R ( D ∗ ) ≡ B ( ¯ B → D ∗ τ − ¯ ν τ ) / B ( ¯ B → D ∗ μ − ¯ ν μ ) and R ( D 0 ) ≡ B ( B − → D 0 τ − ¯ ν τ ) / B ( B − → D 0 μ − ¯ ν μ ) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0     fb − 1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ − → μ − ν τ ¯ ν μ . The measured values are R ( D ∗ ) = 0.281 ± 0.018 ± 0.024 and R ( D 0 ) = 0.441 ± 0.060 ± 0.066 , where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ = − 0.43 . The results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model

Thermal properties of WC-10 wt. (%) Co alloys

In this article, photothermal techniques were used in order to determine some thermal properties: diffusivity, conductivity, effusivity and specific heat capacity of WC-10 wt. (%) Co six samples subjected to different sintering processes. The samples were sintered using high pressure - high temperature (HPHT) sintering system. The open cell photoacoustic (OPC) used to measure thermal diffusivity is described in detail. The values of thermal properties here measured and evaluated are consistent to those previously reported in the literature

Measurement of the Time-Integrated <math display="inline"><mi>C</mi><mi>P</mi></math> Asymmetry in <math display="inline"><mrow><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>-</mo></mrow></msup><msup><mrow><mi>K</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow></math> Decays

International audienceThe time-integrated CP asymmetry in the Cabibbo-suppressed decay D0→K-K+ is measured using proton-proton collision data, corresponding to an integrated luminosity of 5.7  fb-1 collected at a center-of-mass energy of 13 TeV with the LHCb detector. The D0 mesons are required to originate from promptly produced D*+→D0π+ decays, and the charge of the companion pion is used to determine the flavor of the charm meson at production. The time-integrated CP asymmetry is measured to be ACP(K-K+)=[6.8±5.4±1.6]×10-4 where the first uncertainty is statistical and the second systematic. The direct CP asymmetries in D0→K-K+ and D0→π-π+ decays, aK-K+d and aπ-π+d, are derived by combining ACP(K-K+) with the time-integrated CP asymmetry difference, ΔACP=ACP(K-K+)-ACP(π-π+), and other inputs, giving aK-K+d=(7.7±5.7)×10-4,aπ-π+d=(23.2±6.1)×10-4,with a correlation coefficient corresponding to ρ=0.88. The compatibility of these results with CP symmetry is 1.4 and 3.8 standard deviations for D0→K-K+ and D0→π-π+ decays, respectively. This is the first evidence for direct CP violation in a specific D0 decay

Amplitude analysis of the Ds+ {D}_s^{+} → π−π+π+ decay

Abstract A Dalitz plot analysis of the $${D}_s^{+}$$ D s + → π−π+π+ decay is presented. The analysis is based on proton-proton collision data recorded by the LHCb experiment at a centre-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 1.5 fb−1. The resonant structure of the decay is obtained using a quasi-model-independent partial-wave analysis, in which the π+π− S-wave amplitude is parameterised as a generic complex function determined by a fit to the data. The S-wave component is found to be dominant, followed by the contribution from spin-2 resonances and a small contribution from spin-1 resonances. The latter includes the first observation of the $${D}_s^{+}$$ D s + → ω(782)π+ channel in the $${D}_s^{+}$$ D s + → π−π+π+ decay. The resonant structures of the $${D}_s^{+}$$ D s + → π−π+π+ and D+→ π−π+π+ decays are compared, providing information about the mechanisms for the hadron formation in these decays.</jats:p

Multidifferential study of identified charged hadron distributions in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math> -tagged jets in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>13</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:math>

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a Z boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20<pT<100 GeV and in the pseudorapidity range 2.5<η<4. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb-1. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks