Instituto Galego de Física de Altas Enerxías (IGFAE)

Permanent URI for this collectionhttps://hdl.handle.net/10347/34305

O Instituto Galego de Física de Altas Enerxías (IGFAE) é un centro de investigación creado oficialmente o 2 de xullo de 1999. O seu labor investigador está enfocado nas áreas da Física de Altas Enerxías, Física de Astropartículas e Física Nuclear, nas que o persoal investigador do IGFAE se sitúa nos máis altos estándares de impacto, excelencia, liderado e éxito internacional, tanto na vertente teórica como na experimental destas disciplinas.

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Towards an optimally sensitive temperature probe in heavy-ion collisions
(Elsevier, 2025-12) López Pardo, Víctor; Rothkopf, Alexander; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
The high-precision heavy quarkonium data from LHC Run 2 and the ongoing Run 3 provide a unique window into the properties of hot nuclear matter and the Quark-Gluon Plasma (QGP). To make full use of this data, it is crucial to go beyond traditional observables such as the nuclear modification factor 𝑅𝐴𝐴 and elliptic flow 𝑣2, and instead develop new probes that are more directly sensitive to the characteristics of the medium. We adopt the open quantum systems perspective for in-medium quarkonium and take inspiration from cold atom metrology techniques to construct observables with optimal sensitivity to specific QGP parameters. Focusing on the bulk temperature, we develop such optimal observables based on the Caldeira-Leggett master equation as a simplified setup, with the goal of extending it to a full Quantum Brownian Motion Lindblad equation.
Primary scintillation yields induced by α particles in gas mixtures of Argon/CF4 at 9.5 bar
(Springer Nature, 2025-02-14) Amedo, Pablo; Leardini, Sara; Saá Hernández, Ángela; González Díaz, Diego; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
We report time and band -resolved scintillation from α-particles in Ar/CF4 mixtures at a pressure of 9.5 bar. Our results show that %-level addition of CF4 enables strong wavelength-shifted scintillation in the visible range, with yields at the level of 1000 ph/MeV, scintillation decay times of 9–25 ns and formation times well below 10 ns. Such a performance is a priori sufficient for accurate time-tagging of MeV-particles, without the need to resort to a pure noble gas, thus opening an appealing technological path for next-generation time projection chambers.
Strangeness production in pp and pPb collisions at LHCb
(EDP Sciences, 2025-01-27) Landesa Gómez, Clara; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Strange hadron production provides information about the hadronisation process in high-energy hadron collisions. Strangeness enhancement has been interpreted as a signature of quark-gluon plasma formation in heavy-ion collisions, and recent observations of strangeness enhancement in small collision systems have challenged conventional hadronisation models. With its forward geometry and excellent particle identification capabilities, the LHCb detector is well-suited to study strangeness production in a unique kinematic region. Recent studies of strangeness production with the LHCb detector are presented, including measurements of strangeness enhancement in the charm- and beauty-hadron systems.
Automatic Optimization of a Parallel-Plate Avalanche Counter with Optical Readout
(MDPI, 2025) Pereira Martínez, Maria; Cid Vidal, Xabier; Vischia, Pietro; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
An automatic optimization procedure is proposed for some operational parameters of a Parallel-Plate Avalanche Counter with Optical Readout, a detector designed for heavy-ion tracking and imaging. Exploiting differentiable programming and automatic differentiation, we model the reconstruction of the position of impinging 5.5 MeV alpha particles for different detector configurations and build an optimization cycle that minimizes an objective function. We analyze the performance improvement using this method, exploring the potential of these techniques in detector design.
Hot wormholes and chaos dynamics in a two-coupled SYK model
(Springer, 2025-03-14) Berenguer Mimó, Martí; Mas Solé, Javier; Santos Suárez, Juan; Vázquez Ramallo, Alfonso; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
We study the dynamics of chaos across the phase transition in a 2-coupled Sachdev-Ye-Kitaev (SYK) model, with a focus on the unstable “hot wormhole” phase. Using the Schwinger-Keldysh formalism, we employ two non-equilibrium protocols that allow access to this phase, which is inaccessible through equilibrium simulations: one involves cooling the system via a coupling to a thermal bath, while in the other we periodically drive the coupling parameter between the two sides. We numerically compute the Lyapunov exponents of the hot wormhole for the two cases. Our results uncover a rich structure within this phase, including both thermal and non-thermal solutions. These behaviors are analyzed in detail, with partial insights provided by the Schwarzian approximation, which captures certain but not all aspects of the observed dynamics.
Measurement of forward tt, W + bb and W + cc production in pp collisions at √s = 8 TeV
(Elsevier, 2017-02-06) LHCb Collaboration; Adeva Andany, Bernardo; Borsato, Martino; Chobanova, Veronika; Cid Vidal, Xabier; Dosil Suárez, Álvaro; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Pardiñas, Julián; Hernando Morata, José Ángel; Lemos Cid, Edgar; Lucio Martínez, Miriam; Martínez Santos, Diego; Pló Casasús, Máximo; Prisciandaro, Jessica; Ramos Pernas, Miguel; Romero Vidal, Antonio; Saborido Silva, Juan José; Sanmartín Sedes, Brais; Santamarina Ríos, Cibrán; Vázquez Regueiro, Pablo; Vieites Díaz, María; Vázquez Sierra, Carlos; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE); Universidade de Santiago de Compostela. Departamento de Física de Partículas
The production of tt, W + bb and W + cc is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 ± 0.02 fb−1. The W bosons are reconstructed in the decays W → ν, where denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions
Development of a silicon bulk radiation damage model for Sentaurus TCAD
(Elsevier, 2017-12-01) Folkestad, Å.; Akiba, K.; Beuzekom, M. van; Buchanan, E.; Collins, P.; Dall'Occo, E.; Canto, A. Di; Evans, T.; Franco Lima, V.; García Pardiñas, Julián; Schindler, H.; Vicente, M.; Vieites Díaz, María; Williams, M.; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
This article presents a new bulk radiation damage model for p-type silicon for use in Synopsys Sentaurus TCAD. The model is shown to provide agreement between experiment and simulation for the voltage dependence of the leakage current and the charge collection efficiency, for fluences up to 8 × 1015 1 MeV neq∕cm2 .
Confusing Head-On Collisions with Precessing Intermediate-Mass Binary Black Hole Mergers
(APS, 2021-05-17) Calderón Bustillo, Juan; Sanchis-Gual, Nicolas; Torres-Forné, Alejandro; Font, José A.; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
We report a degeneracy between the gravitational-wave signals from quasicircular precessing black-hole mergers and those from extremely eccentric mergers, namely, head-on collisions. Performing model selection on numerically simulated signals of head-on collisions using models for quasicircular binaries, we find that, for signal-to-noise ratios of 15 and 25, typical of Advanced LIGO observations, head-on mergers with respective total masses of 𝑀 ∈(125,300)⁢𝑀⊙ and 𝑀 ∈(200,440)⁢𝑀⊙ would be identified as precessing quasicircular intermediate-mass black-hole binaries located at a much larger distance. Ruling out the head-on scenario would require us to perform model selection using currently nonexistent waveform models for head-on collisions, together with the application of astrophysically motivated priors on the (rare) occurrence of those events. We show that in situations where standard parameter inference of compact binaries may report component masses inside (outside) the pair-instability supernova gap, the true object may be a head-on merger with masses outside (inside) this gap. We briefly discuss the potential implications of these findings for GW190521, which we analyze in detail in J.
GW190521 as a Merger of Proca Stars: A Potential New Vector Boson of 8.7 x 10 -13 eV
(APS, 2021-02-24) Calderón Bustillo, Juan; Sanchis-Gual, Nicolas; Torres-Forné, Alejandro; Font, José A.; Vajpeyi, Avi; Smith, Rory; Herdeiro, Carlos; Radu, Eugen; Leong, Samson H. W.; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Advanced LIGO-Virgo have reported a short gravitational-wave signal (GW190521) interpreted as a quasicircular merger of black holes, one at least populating the pair-instability supernova gap, that formed a remnant black hole of 𝑀𝑓 ∼142 𝑀⊙ at a luminosity distance of 𝑑𝐿 ∼5.3 Gpc. With barely visible pre-merger emission, however, GW190521 merits further investigation of the pre-merger dynamics and even of the very nature of the colliding objects. We show that GW190521 is consistent with numerically simulated signals from head-on collisions of two (equal mass and spin) horizonless vector boson stars (aka Proca stars), forming a final black hole with 𝑀𝑓 =23⁢1+13−17 𝑀⊙, located at a distance of 𝑑𝐿 =57⁢1+348−181 Mpc. This provides the first demonstration of close degeneracy between these two theoretical models, for a real gravitational-wave event. The favored mass for the ultralight vector boson constituent of the Proca stars is 𝜇V =8.7⁢2+0.73−0.82 ×10−13 eV. Confirmation of the Proca star interpretation, which we find statistically slightly preferred, would provide the first evidence for a long sought dark matter particle.
Mapping the Universe Expansion: Enabling Percent-level Measurements of the Hubble Constant with a Single Binary Neutron-star Merger Detection
(American Astronomical Society | IOP Publishing, 2021-04-30) Calderón Bustillo, Juan; Leong, Samson H. W.; Dietrich, Tim; Lasky, Paul D.; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
The joint observation of the gravitational-wave (GW) and electromagnetic (EM) signal from the binary neutron-star merger GW170817 allowed for a new independent measurement of the Hubble constant H0, albeit with an uncertainty of about 15% at 1σ. Observations of similar sources with a network of future detectors will allow for more precise measurements of H0. These, however, are currently largely limited by the intrinsic degeneracy between the luminosity distance and the inclination of the source in the GW signal. We show that the higher-order modes in gravitational waves can be used to break this degeneracy in astrophysical parameter estimation in both the inspiral and post-merger phases of a neutron star merger. We show that for systems at distances similar to GW170817, this method enables percent-level measurements of H0 with a single detection. This would permit the study of time variations and spatial anisotropies of H0 with unprecedented precision. We investigate how different network configurations affect measurements of H0, and discuss the implications in terms of science drivers for the proposed 2.5- and third-generation GW detectors. Finally, we show that the precision of H0 measured with these future observatories will be solely limited by redshift measurements of EM counterparts.
Gravitational-wave parameter inference with the Newman-Penrose scalar
(APS, 2023-12-12) Calderón Bustillo, Juan; Wong, Isaac C. F.; Sanchís Gual, Nicolás; Leong, Samson H. W.; Torres Forné, Alejandro; Chandra, Koustav; Font, José A.; Herdeiro, Carlos; Radu, Eugen; Li, Tjonnie G. F.; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Detection and parameter inference of gravitational-wave signals from compact mergers rely on the comparison of the incoming detector strain data 𝑑⁡(𝑡) to waveform templates for the gravitational-wave strain ℎ⁡(𝑡) that ultimately rely on the resolution of Einstein’s equations via numerical relativity simulations. These, however, commonly output a quantity known as the Newman-Penrose scalar 𝜓4⁡(𝑡) which, under the Bondi gauge, is related to the gravitational-wave strain by 𝜓4⁡(𝑡) =𝑑2⁢ℎ⁡(𝑡)/𝑑⁢𝑡2. Therefore, obtaining strain templates involves an integration process that introduces artifacts that need to be treated in a rather manual way. By taking second-order finite differences on the detector data and inferring the corresponding background noise distribution, we develop a framework to perform gravitational-wave data analysis directly using 𝜓4⁡(𝑡) templates. We first demonstrate this formalism, and the impact of integration artifacts in strain templates, through the recovery of numerically simulated signals from head-on collisions of Proca stars injected in Advanced LIGO noise. Next, we reanalyze the event GW190521 under the hypothesis of a Proca-star merger, obtaining results equivalent to those previously published [Phys. Rev. Lett. 126, 081101 (2021)], where we used the classical strain framework. We find, however, that integration errors would strongly impact our analysis if GW190521 was 4 times louder. Finally, we show that our framework fixes significant biases in the interpretation of the high-mass gravitational-wave trigger S200114f arising from the usage of strain templates. We remove the need to obtain strain waveforms from numerical relativity simulations, avoiding the associated systematic errors
Centrality dependence of multistrange baryon production in high-energy heavy-ion collisions
(SciPost, 2024-04-03) Arakelyan, Gevorg H.; Merino Gayoso, Carlos Miguel; Shabelski, Yuli M.; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
We consider the experimental data on the production of strange Λ′s, and multistrange baryons (Ξ, Ω), and antibaryons, on nuclear targets, at the energy region from SPS up to LHC, in the framework of the Quark-Gluon String Model. One remarkable result of this analysis is the significant dependence on the centrality of the collision of the experimental Ξ+/Λ and Ω+/Λ ratios in heavy-ion collisions, at SPS energies.
Search for A' -> mu+mu- Decays
(American Physical Society, 2020-01-29) Aaij, Roel; Adeva Andany, Bernardo; Alves Junior, Antonio Augusto; Boente García, Óscar; Brea Rodríguez, Alexandre; Casais Vidal, Adrián; Chobanova, Veronika; Cid Vidal, Xabier; Dalseno, Jeremy; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Plana, Beatriz; Gioventù, Alessandra; Lomba Castro, Julián; Martínez Santos, Diego; Pló Casasús, Máximo; Prouve, Claire; Ramos Pernas, Miguel; Romero Lamas, Marcos; Romero Vidal, Antonio; Saborido Silva, Juan José; Sanmartín Sedes, Brais; Santamarina Ríos, Cibrán; Vázquez Regueiro, Pablo; Zucchelli, Stefano; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Searches are performed for both promptlike and long-lived dark photons, 𝐴′, produced in proton-proton collisions at a center-of-mass energy of 13 TeV. These searches look for 𝐴′ →𝜇+⁢𝜇− decays using a data sample corresponding to an integrated luminosity of 5.5 fb−1 collected with the LHCb detector. Neither search finds evidence for a signal, and 90% confidence-level exclusion limits are placed on the 𝛾–𝐴′ kinetic mixing strength. The promptlike 𝐴′ search explores the mass region from near the dimuon threshold up to 70 GeV and places the most stringent constraints to date on dark photons with 214 <𝑚⁡(𝐴′) ≲740 MeV and 10.6 <𝑚⁡(𝐴′) ≲30 GeV. The search for long-lived 𝐴′ →𝜇+⁢𝜇− decays places world-leading constraints on low-mass dark photons with lifetimes 𝒪⁡(1) ps.
Unleashing the full power of LHCb to probe stealth new physics
(IOP Publishing, 2022-02-16) Borsato, Martino; Cid Vidal, Xabier; Zupan, Jure; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
In this paper, we describe the potential of the LHCb experiment to detect Stealth physics. This refers to dynamics beyond the Standard Model that would elude searches that focus on energetic objects or precision measurements of known processes. Stealth signatures include long-lived particles and light resonances that are produced very rarely or together with overwhelming backgrounds. We will discuss why LHCb is equipped to discover this kind of physics at the Large Hadron Collider and provide examples of well-motivated theoretical models that can be probed with great detail at the experiment.
Search for Lepton-Flavor Violating Decays B+ --> K+ mu± e∓
(American Physical Society, 2019-12-12) LHCb Collaboration; R. Aaij; Adeva Andany, Bernardo; Alves, António Augusto; Boente García, Óscar; Brea Rodríguez, Alexandre; Casais Vidal, Adrián; Chobanova, Veronika; Cid Vidal, Xabier; Dalseno, Jeremy; Dosil Suárez, Álvaro; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Plana, Beatriz; Gioventù, Alessandra; Lomba Castro, Julián; Martínez Santos, Diego; Pló Casasús, Máximo; Prouve, Claire; Ramos Pernas, Miguel; Romero Vidal, Antonio; Saborido Silva, Juan José; Sanmartín Sedes, Brais; Santamarina Ríos, Cibrán; Vázquez Regueiro, Pablo; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE); Universidade de Santiago de Compostela. Departamento de Física de Partículas
A search for the lepton-flavor violating decays 𝐵+ →𝐾+⁢𝜇±⁢𝑒∓ is performed using a sample of proton-proton collision data, collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponding to an integrated luminosity of 3 fb−1. No significant signal is observed, and upper limits on the branching fractions are set as ℬ⁡(𝐵+→𝐾+⁢𝜇−⁢𝑒+)<7.0⁢(9.5)×10−9 and ℬ⁡(𝐵+→𝐾+⁢𝜇+⁢𝑒−)<6.4⁢(8.8)×10−9 at 90% (95)% confidence level. The results improve the current best limits on these decays by more than one order of magnitude
Measurement of CP-averaged observables in the B0 -> K*0 mu+ mu- Decay
(American Physical Society, 2020-07-02) LHCb Collaboration; R. Aaij; Adeva Andany, Bernardo; Alves, António Augusto; Boente García, Óscar; Brea Rodríguez, Alexandre; Casais Vidal, Adrián; Chobanova, Veronika; Cid Vidal, Xabier; Dalseno, Jeremy; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Plana, Beatriz; Gioventù, Alessandra; Lomba Castro, Julián; Martínez Santos, Diego; Pló Casasús, Máximo; Prouve, Claire; Ramos Pernas, Miguel; Romero Lamas, Marcos; Romero Vidal, Antonio; Saborido Silva, Juan José; Santamarina Ríos, Cibrán; Vázquez Regueiro, Pablo; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE); Universidade de Santiago de Compostela. Departamento de Física de Partículas
An angular analysis of the 𝐵0→𝐾*0⁡(→𝐾+⁡𝜋−)⁢𝜇+⁢𝜇− decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb−1 of 𝑝⁢𝑝 collision data collected with the LHCb experiment. The full set of 𝐶⁢𝑃-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the 𝐾+⁢𝜋− system in an 𝑆-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters
Observation of a new Ξ0b state
(American Physical Society, 2021-01-06) Aaij, Roel; Adeva Andany, Bernardo; Álvarez Cartelle, Paula; Baladrón Rodríguez, Pablo; Boente García, Óscar; Brea Rodríguez, Alexandre; Casais Vidal, Adrián; Chobanova, Veronika; Cid Vidal, Xabier; Dalseno, John; Dieste Maroñas, Lorena; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Plana, Beatriz; Gioventù, Alessandra; Lomba Castro, Julián; Martínez Santos, Diego; Parkinson, C.J.; Pló Casasús, Máximo; Prouve, Claire; Romero Lamas, Marcos; Romero Vidal, Antonio; Saborido Silva, Juan José; Santamarina Ríos, Cibrán; Sellam, Sara; Vázquez Gómez, Ricardo; Vázquez Regueiro, Pablo; Vieites Díaz, María; Zunica, Gianluca; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Using 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 Ξ0b 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+1.4−1.5+-0.5 MeV and Γ(Ξb(6227)0) =18,6+5.0−4.1+-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)0/fΞb−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.
Amplitude analysis of the B0→K∗0K∗0 decays and measurement of the branching fraction of the B0(s)→K∗0K∗0 decay
(Springer, 2019-07-05) LHCb Collaboration; Adeva Andany, Bernardo; Álvarez Cartelle, Paula; Alves, António Augusto; Boente García, Óscar; Chobanova, Veronika; Cid Vidal, Xabier; Dalseno, Jeremy; Dosil Suárez, Álvaro; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Plana, Beatriz; Lucio Martínez, M.; Martínez Santos, Diego; Pló Casasús, Máximo; Prouve, Claire; Ramos Pernas, Miguel; Romero Vidal, Antonio; Saborido Silva, Juan José; Sanmartín Sedes, Brais; Santamarina Ríos, Cibrán; Vázquez Regueiro, Pablo; Vieites Díaz, María; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE); Universidade de Santiago de Compostela. Departamento de Física de Partículas
The B0 → K∗0K∗0 and Bs0 → K∗0K∗0 decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3fb−1. An untagged and time- integrated amplitude analysis of B0 → (K+π−)(K−π+) decays in two-body invariant (s) mass regions of 150MeV/c2 around the K∗0 mass is performed. A stronger longitudinal polarisation fraction in the B0 → K∗0K∗0 decay, fL = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to fL = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the Bs0 → K∗0K∗0 decay. The ratio of branching fractions of the two decays is measured and used to determine B(B0 → K∗0K∗0) = (8.0 ± 0.9 (stat) ± 0.4 (syst)) × 10−7
First measurement of the CP -violating phase φdd ̄ in s Bs0→(K+π−)(K−π+) decays
(Springer, 2018-03-23) LHCb Collaboration:; Adeva Andany, Bernardo; Álvarez Cartelle, Paula; Borsato, Martino; Chobanova, Veronika; Cid Vidal, Xabier; Dosil Suárez, Álvaro; Fernández Prieto, Antonio; Gallas Torreira, Abraham; García Pardiñas, Julián; Lemos Cid, Edgar; Lucio Martinez, M.; Martínez Santos, Diego; Pló Casasús, Máximo; Prisciandaro, Jessica; Ramos Pernas, Miguel; Romero Vidal, Antonio; Saborido Silva, Juan José; Sanmartín Sedes, Brais; Santamarina Ríos, Cibrán; Vázquez Regueiro, Pablo; Vieites Díaz, María; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE); Universidade de Santiago de Compostela. Departamento de Física de Partículas
A flavour-tagged decay-time-dependent amplitude analysis of Bs0 →(K+π−)(K−π+) decays is presented in the K±π∓ mass range from 750 to 1600MeV/c2. The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8TeV, corresponding to an integrated luminosity of 3.0fb−1. Several quasi-two-body decay modes are considered, corresponding to K±π∓ combinations with spin 0, 1 and 2, which are dominated by the K0∗ (800)0 and K0∗ (1430)0 , the K ∗ (892)0 and the K2∗(1430)0 resonances, respectively. The longitudinal polarisation fraction for the Bs0 → K ∗ (892)0 K ∗ (892)0 decay is measured as fL = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the dd mixing-induced CP-violating phase, φs , in b → dds transitions is performed, yielding a value of φdd ̄ = −0.10 ± 0.13 (stat) ± 0.14 (syst) rad
Precise determination of the B0 s –B 0 s oscillation frequency
(Springer Nature, 2022-01-06) LHCb collaboration; Aaij, R.; Adeva Andany, Bernardo; Baladrón Rodríguez, Pablo; Boente García, Óscar; Brea Rodríguez, Alexandre; Casais Vidal, Adrián; Chobanova, Veronika; Cid Vidal, Xabier; Dalseno, Jeremy; Dieste Maronas, L.; Fernández Prieto, Antonio; Gallas Torreira, Abraham; Garcia Plana, Beatriz; Gioventù, Alessandra; Lomba Castro, Julián; Martínez Santos, Diego; Parkinson, C. J.; Pló Casasús, Máximo; Prouve, Claire; Romero Lamas, Marcos; Romero Vidal, Antonio; Saborido Silva, Juan José; Santamarina Ríos, Cibrán; Sellam, Sara; Vázquez Gómez, Ricardo; Vázquez Regueiro, Pablo; Álvarez Cartelle, Paula; Borsato, Martino; Vieites Díaz, María; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
Mesons comprising a beauty quark and strange quark can oscillate between particle (B0s) and antiparticle (B0s) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Delta(ms). Here we present a measurement of Delta(ms) using B0s --> D−s pi+ decays produced in proton–proton collisions collected with the LHCb detector at the Large Hadron Collider. The oscillation frequency is found to be Delta(ms) = 17.7683±0.0051±0.0032 ps−1, where the first uncertainty is statistical and the second is systematic. This measurement improves on the current Delta(ms) precision by a factor of two. We combine this result with previous LHCb measurements to determine Delta(ms) = 17.7656±0.0057 ps−1, which is the legacy measurement of the original LHCb detector

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