Proceedings of the talk Study of CP violation in charm meson decays for XXX Epiphany conference

Basic idea of $CP$ violation and its importance for cosmology, Standard Model and possible New Physics are introduced. Recent (2019) discovery of CP violation in charm in the $ΔA_{CP}$ between $D^0\rightarrow K^-K^+$ and $D^0\rightarrow π^+π^-$ decay channels and evidence for direct CP violation in $D^0\rightarrow π^-π^+$ decays in 2023 is discussed. Motivation and brief outline for search of CP violation in the $D^0\rightarrow Vγ$, where $V=ϕ,ρ^0, \bar{K}^{*0}$ decays is given.Submitted to Acta Physica Polonica B. Accepted for publication on 7th of May, 202

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

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 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. 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.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ 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 $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. 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.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

First observation of the Λ0 b → Λ+ c D− s K+K− decay and search for pentaquarks in the Λ+ c D− s system

The Λ0 b → Λþ c D− s KþK− decay is observed for the first time using the data sample from proton-proton collisions recorded at a center-of-mass energy of 13 TeV with the LHCb detector, corresponding to an integrated luminosity of 6 fb−1. The ratio of branching fraction to that of Λ0 b → Λþ c D− s decays is measured as 0.0141 0.0019 0.0012, where the first uncertainty is statistical and the second systematic. A search for hidden-charm pentaquarks with strangeness is performed in the Λþ c D− s system. No evidence is found, and upper limits on the production ratio of Pccs¯ ð4338Þ0 and Pccs¯ ð4459Þ0 pentaquarks relative to the Λþ c D− s final state are set at the 95% confidence level as 0.12 and 0.20, respectively

Measurement of CPCP asymmetry in radiative charm decays at LHCb

This thesis presents a measurement of $CP$ asymmetry, $A_{CP}$, for radiative decays of charm mesons $D^0 \to V \gamma$, and their charge conjugates, where $V$ denotes vector meson $\bar{K}^{*0}$, $\phi$ or $\rho^0$. The study is based on the proton-proton collision data collected at a centre-of-mass energy of $\sqrt{s} = 8$~TeV by the LHCb experiment in 2012, during Run-1 of the LHC. This data sample corresponds to an integrated luminosity of 2 fb$^{-1}$. Reconstructed neutral $D$ mesons originate from strong decays of the $D^{*\pm}$ states, $D^{*+}\to D^0 \pi^+_s$ and $D^{*-}\to \bar{D}^0 \pi^-_s$, with the soft-pion $\pi_s$ charge used for tagging of a $D$ flavour at the production. The presented analysis is the first study of radiative charm decays at LHCb. \\ Large and irreducible background from decays involving $\pi^0$ mesons, $D^0\to V \pi^0$, is suppressed using a multivariate classifier based on distinguished shapes of energy clusters produced by photons and $\pi^0$ mesons in the LHCb calorimeter system. The signal decays are separated from residual background with the three-dimensional fit to $D^0$ invariant mass $M(D^0)$, the difference between invariant masses of $D^{*+}$ and $D^0$, $\Delta M = M(D^{*+})-M(D^0)$, and $V$-meson helicity angle $\cos{\theta}$, as observables. Correlations observed between $M(D^0)$ and $\Delta M$ observables for both signal and background channels, are modelled based on the corresponding simulation samples. The total $D^0$ and $\bar{D}^0$ signal yields are measured to be: $4263 \pm 193$ events for $D^0\to \bar{K}^{*0}\gamma$ decay, and $216 \pm 29$ events for the $D^0\to \phi\gamma$ decay; no significant signal is observed for the $D^0\to \rho\gamma$ decay. \\ Nuisance asymmetries due to asymmetric charm production and asymmetric detection of positively and negatively charged hadrons, are constrained with high-statistics and high-purity reference channels. The pion-tagged $D^0 \to K^+K^-$ and $D^0 \to \pi^+\pi^-$ decays are chosen as reference channels for $D^0 \to \phi \gamma$ and $D^0 \to \rho^0 \gamma$ signal decays, respectively, whereas $D^0 \to K^- \pi^+ \pi^0$ is used as a reference channel for $D^0 \to \bar{K}^{*0} \gamma$. The nuisance asymmetries are measured to be about $(-1.0 \pm 0.2)\%$ in $D^0 \to K^+K^-$ and $D^0 \to \pi^+\pi^-$ channels, and $(-1.7 \pm 0.3)\%$ in $D^0 \to K^- \pi^+ \pi^0$. They are subtracted from asymmetries measured for the signal channels in order to access $A_{CP}$. \\ The asymmetries for the signal channels are measured by performing the three-dimensional fits in $M(D^0)$ vs. $\Delta M$ vs. $\cos{\theta}$ space, simultaneously to the separated $D^0$ and $\bar{D}^0$ samples. The central values of the asymmetries are still blinded, while their statistical uncertainties are measured to be 5\% for $D^0 \to \bar{K}^{*0} \gamma$ and 12\% for $D^0 \to \phi \gamma$; the Run-1 analysis is not sensitive to the asymmetry in the $D^0 \to \rho^0 \gamma$ decay. The presented measurement is statistically limited. The total systematic uncertainties on the signal $A_{CP}$'s are expected to be below 1\%, and dominated by statistical uncertainties on the asymmetries measured in the reference channels. Unblinding is planned together with the Run-2 measurement, which is currently ongoing

Proceedings of the talk "Study of CP violation in charm meson decays" for XXX Epiphany conference

Basic idea of $CP$ violation and its importance for cosmology, Standard Model and possible New Physics are introduced. Recent (2019) discovery of CP violation in charm in the $\Delta A_{CP}$ between $D^0\rightarrow K^-K^+$ and $D^0\rightarrow \pi^+\pi^-$ decay channels and evidence for direct CP violation in $D^0\rightarrow \pi^-\pi^+$ decays in 2023 is discussed. Motivation and brief outline for search of CP violation in the $D^0\rightarrow V\gamma$, where $V=\phi,\rho^0, \bar{K}^{*0}$ decays is given

Modification of Vibrational Parameters of a CO₂ Molecule by a Laser Field: Impact on Tunnel Ionization

In this paper, we theoretically study the laser-induced modification of the vibrational parameters of a carbon dioxide molecule regarding its tunnel ionization. Our study predicts a 5% increase in the ionization rate in anti-Stokes channels that corresponds to pumping the Σu mode up to vai=10. The molecule is imparted with an additional energy from the pre-pumped vibrational states, which is absorbed during ionization. As a result, the tunneling rate increases. This amplification of tunnel ionization of the CO2 gas target can potentially be used for the laser separation of carbon isotopes

Research of Changes of Value of Potential Barrier at the Metal/Polymer Interface during Phase Transitions in Metal

The article is devoted to the study of influence of the first-order phase transition in a metal (In) on changes in the metal/polymer potential barrier. The metal that undergoes the phase transition is not in direct contact with the polymer film. Analysis of the current-voltage characteristics allows to calculate the changes in the magnitude of the metal/polymer potential barrier at the phase transitions in In.</jats:p