arXiv subjects

Eluned Smith

Publications and source records attributed to Eluned Smith.

4 recordsLinked to original sources

arXiv2025

Flavor-physics benchmarks for tracker-based particle identification at the FCC-ee

The correct identification of charged hadrons plays a crucial role in flavor-physics measurements. The final detector configurations at the proposed Future Circular Collider are yet to be determined and this study aims to contribute to this discussion by benchmarking the particle-identification (PID) performance of the proposed CLD and IDEA detectors using fully simulated events. At present, neither detector proposal includes dedicated PID systems, relying instead on information from the tracking subsystems. We estimate the expected level of contamination due to misidentified charged hadrons for $b$-flavor tagging, rare $b\to s$ transitions, and $s$-jet tagging. The PID information provided by silicon trackers, namely time-of-flight and energy-deposit measurements, leads to significant background suppression with high signal efficiency for the low-momentum hadrons considered for same-side $b$-flavor tagging. In order to improve the contamination in rare decays where momenta are in the medium range, only good timing resolution of 30ps and below can yield an improvement of one order of magnitude below the level achieved by kinematic criteria alone. Light-quark jet-flavor tagging requires identification of particles with very large momentum, which is not possible using only time-of-flight or energy-deposit information in silicon. Access to the number of clusters in a drift-chamber setup, as proposed for the IDEA detector however, results in strong background suppression in every case. This suppression can be further improved in some scenarios by time-of-flight resolution of 30-50ps or better. The PID quality generally exhibits only a small dependence on the cluster-counting efficiency. Whether dedicated PID detectors could further enhance flavor-physics sensitivity should be the subject of future study.

hep-ex↗

arXiv2025

Prospects for Measuring $CP$-Violation in $B_s^0 \rightarrow \phi \mu^+\mu^-$ via Time-Dependent Angular Analysis

This work investigates the prospects for performing a time-dependent angular analysis of $B_s^0 \rightarrow \phi \mu^+\mu^-$ decays at hadron colliders, and introduces new optimised angular observables associated with $B_s^0$-mixing in the decay rate. The time-dependent normalised decay rate and corresponding probability density function is presented both for when the flavour of the $B_s^0$ meson at production is tagged and when it is untagged. The normalised angular terms linked to $B_s^0$-mixing in the tagged (untagged) case are denoted $\mathcal{Z}_i$ ($\mathcal{H}_i$), and their optimised counterparts as $Q_i$ ($\mathcal{M}_i$). The expected sensitivities of these observables at the end of Run 3, Run 4, and Run 5 of the LHC are determined using pseudoexperiments generated with a decay-time resolution, background level, and signal yield similar to those reported by the LHCb collaboration. It is found that all observables can be extracted with Run 3 statistics, and that the $\mathcal{H}_i$ and $\mathcal{Z}_i$ observables have similar sensitivity, despite the former being suppressed by mixing terms. Moreover, the angular observables only accessible via flavour tagging, such as the equivalent of $P_5^{\prime}$ in the $B^0_s$ system, are found to exhibit sensitivities comparable to current measurements in $B^0 \rightarrow K^{\ast 0} \mu^+\mu^-$ decays once Run 5 datasets are available. Fits to the observables to extract the Wilson coefficients show a significant increase in precision when either the observables accessible via time-dependent analysis, or flavour tagging, are included. A marked increase in sensitivity to $CP$-violating short-distance effects is observed for a subset of the new optimised $M_i$ and $Q_i$ observables.

hep-ex↗

arXiv2025

Constraints on new physics from decays of polarized $\Lambda_b^0$ baryons at the FCC-ee

The $Z^0$ bosons produced in electron-positron collisions at the potential Future Circular Collider (FCC-ee) provide unique opportunities for flavour physics. The non-zero polarization of \Lb baryons produced in $Z^0$ decays enables access to a much larger set of observables than at the LHC, where the $\Lambda_b^0$ baryons are produced unpolarized. This paper presents a toy angular analysis of $\Lambda_b^0\to \Lambda(\to p\pi^-)\mu^+\mu^-$ decays using simulation samples of collisions at the FCC-ee reconstructed using the IDEA detector concept and assuming a dataset of $6\times 10^{12}$ $Z^0$ bosons. While the statistical sensitivity achieved for individual angular observables is not expected to significantly exceed that from the LHCb Upgrade II experiment, the addition of the polarized observables leads to a significant improvement of the knowledge on the Wilson coefficients $C_{9^{(\prime)}}$ and $C_{10^{(\prime)}}$.

hep-ex↗

arXiv2025

Non-parametric and continuous extraction of amplitudes in electroweak penguin decays

We introduce a novel approach to extract the decay-amplitudes in $B\to V(\to M_1M_2)\ell^+\ell^-$ processes, where $V$ represents a meson with either $J = 0$ (S-wave) or $J = 1$ (P-wave). This approach enables the decay-amplitudes across the dihadron and dilepton invariant-masses to be extracted from data in a model-independent and continuous way. To achieve this, the angular decay rate is expressed in a way that allows the application of the \sPlot technique to likelihood fits of the decay angles. We illustrate the abilities of this method on simulated $B^0\to K^+\pi^-\ell^+\ell^-$ data, containing both S- and P-wave contributions to the $K^+\pi^-$ system. We provide the weight functions and show that they allow the extraction of the absolute value of the P-wave and S-wave transversity amplitudes as a function of the dihadron and dimuon invariant-masses in a continuous, unbiased, and statistically-powerful way, while only relying on the angular distribution. As a consequence, the extracted amplitude shapes are model-independent -- up to the angular terms included in the fit -- and can be directly compared to theoretical predictions. A measurement using this technique can improve the sensitivity to potential new physics effects in $b\to s\ell^+\ell^-$ transitions, as well as the understanding of hadronic form factors, particularly in the S-wave system.

hep-ex↗