arXiv subjects

Evelina Gersabeck

Publications and source records attributed to Evelina Gersabeck.

6 recordsLinked to original sources

arXiv2026

Charm physics

50 years after the discovery of the first charmed particle, charm physics continues to be an extremely lively field of research and a cornerstone in particle physics. The study of charm, with its unique properties, is characterised by many challenging but also exciting peculiarities, making it an ideal testing ground for Standard Model (SM) predictions and a very sensitive probe of new physics. This chapter is intended to provide a pedagogical introduction to the physics of the charm quark and to its current theoretical and experimental status. Specifically, it discusses the main features of the charm sector of the SM, the theoretical and experimental challenges that arise when dealing with the charm quark, and the methods used to study it. An overview, both from a theoretical and experimental perspective, of fundamental observables such as lifetimes of charm hadrons, $D^0$-meson mixing, charm charge-parity violation (CPV) and rare charm decays is also presented.

hep-ph↗

arXiv2023

A novel unbinned model-independent method to measure the CKM angle $γ$ in $B^{\pm} \to DK^{\pm}$ decays with optimised precision

We present a novel unbinned method to combine $B^{\pm} \to DK^{\pm}$ and charm threshold data for the amplitude-model unbiased measurement of the CKM angle gamma in cases where the D meson decays to a three-body final state. The new unbinned approach avoids any kind of integration over the D Dalitz plot, to make optimal use the available information. We verify the method with simulated signal data where the D decays to $K_S π^+ π^-$. Using realistic sample sizes, we find that the new method reaches the statistical precision on gamma of an unbinned model-dependent fit, i.e. as good as possible and better than the widely used model-independent binned approach, without suffering from biases induced by a mis-modeled D decay amplitude.

hep-ph↗

arXiv2018

Amplitude analysis of $D^{0} \rightarrow π^{+} π^{-} π^{+} π^{-}$ decays using CLEO-c data

The resonant substructure of the decay $D^{0} \rightarrow π^{+} π^{-} π^{+} π^{-}$ is studied by performing a full five-dimensional amplitude analysis. Preliminary results based on data collected by the CLEO-c detector are presented. This is the largest dataset of $D^{0} \rightarrow π^{+} π^{-} π^{+} π^{-}$ decays analysed in this way to-date. The two most significant contributions are $D^{0} \rightarrow a_{1}(1260)^{+} π^{-}$ and $D^{0} \rightarrow ρ(770)^{0}ρ(770)^{0}$. The line shape, mass and width of the $a_{1}(1260)$ resonance are determined, and model-independent studies of the line shapes of several resonant contributions are preformed.

hep-ex↗

arXiv2017

Amplitude Analyses of $D^0 \to {π^+π^-π^+π^-}$ and $D^0 \to {K^+K^-π^+π^-}$ Decays

The resonant substructure of $D^0 \to π^+π^-π^+π^-$ decays is studied using data collected by the CLEO-c detector. An amplitude analysis is performed in order to disentangle the various intermediate state contributions. To limit the model complexity a data driven regularization procedure is applied. The prominent contributions are the decay modes $D^0\to a_1(1260)^+π^-$, $D^0\to σf_0(1370)$ and $D^0 \to ρ(770)^0 ρ(770)^0$. The broad resonances $a_1(1260)^+$, $π(1300)^+$ and $a_1(1640)^+$ are studied in detail, including quasi-model-independent parametrizations of their lineshapes. The mass and width of the $a_1(1260)^+$ meson are determined to be $m_{a_1(1260)^+}=[1225\pm9\text{(stat)}\pm17\text{(syst)}\pm10\text{(model)}]\text{MeV}/c^2$ and $Γ_{a_1(1260)^+}=[430\pm24\text{(stat)}\pm25 \text{(syst)}\pm18\text{(model)}]\text{MeV}$. The amplitude model of $D^0\to K^+K^-π^+π^-$ decays obtained from CLEO II.V, CLEO III, and CLEO-c data is revisited with improved lineshape parametrizations. The largest components are the decay modes $D^0\toϕ(1020)ρ(770)^0$, $D^0 \to K_1(1270)^+ K^-$ and $D^0 \to K(1400)^+ K^-$. The fractional $CP$-even content of the decay $D^0\to π^+π^-π^+π^-$ is calculated from the amplitude model to be $F_+^{4π}=[72.9\pm0.9\text{(stat)}\pm1.5\text{(syst)}\pm1.0\text{(model)}]\%$, consistent with that obtained from a previous model-independent measurement. For $D^0 \to K^+K^-π^+π^-$ decays, the $CP$-even fraction is measured for the first time and found to be $F_+^{KKππ}=[75.3\pm1.8\text{(stat)}\pm3.3\text{(syst)}\pm3.5\text{(model)}]\%$. The global decay rate asymmetries between $D^0$ and $\overline{D}^0$ decays are measured to be $A^{4π}_{CP}=[+0.54\pm1.04\text{(stat)}\pm0.51\text{(syst)}]\%$ and $A^{KKππ}_{CP}=[+1.84\pm1.74\text{(stat)}\pm0.30\text{(syst)}]\%$.

hep-ex↗

arXiv2016

Measurement of CP asymmetries in $D^0 \rightarrow hh$ decays

The latest measurements of the individual time-integrated CP asymmetry in the Cabibbo-suppressed decays $D^0\rightarrow hh$ decays are presented. The results are based on $pp$ collision data, corresponding to an integrated luminosity of $3 fb^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. A combination of the asymmetries using both prompt and secondary charm decays is presented $A_{CP}(K^-K^+) = (0.04 \pm 0.12(stat) \pm 0.10(syst))%$; $A_{CP}(π^-π^+) = (0.07 \pm 0.14(stat) \pm 0.11(syst))$. These are the most precise measurements from a single experiment. The result for $A_{CP}(K^-K^+)$ is the most precise determination of a time-integrated CP asymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry.

hep-ex↗

arXiv2014

Direct CPV in two-body and multi-body charm decays at LHCb

The Standard Model predicts CP asymmetries in charm decays of $O(10^{-3})$ and the observation of significantly larger CP violation could indicate non-Standard Model physics effects. During 2011 and 2012, the LHCb experiment collected a sample corresponding to 3/fb yielding the world's largest sample of decays of charmed hadrons. This allowed the CP violation in charm to be studied with unprecedented precision in many two- body and multibody decay modes. The most recent LHCb searches for direct CP violation are presented in these proceedings.

hep-ex↗