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Free, publicly-accessible full text available September 1, 2025
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A bstract A comprehensive study of the local and nonlocal amplitudes contributing to the decay
B 0→K *0(→K +π − )μ +μ − is performed by analysing the phase-space distribution of the decay products. The analysis is based onpp collision data corresponding to an integrated luminosity of 8.4 fb− 1collected by the LHCb experiment. This measurement employs for the first time a model of both one-particle and two-particle nonlocal amplitudes, and utilises the complete dimuon mass spectrum without any veto regions around the narrow charmonium resonances. In this way it is possible to explicitly isolate the local and nonlocal contributions and capture the interference between them. The results show that interference with nonlocal contributions, although larger than predicted, only has a minor impact on the Wilson Coefficients determined from the fit to the data. For the local contributions, the Wilson Coefficient , responsible for vector dimuon currents, exhibits a 2.1$$ {\mathcal{C}}_9 $$ σ deviation from the Standard Model expectation. The Wilson Coefficients ,$$ {\mathcal{C}}_{10} $$ and$$ {\mathcal{C}}_9^{\prime } $$ are all in better agreement than$$ {\mathcal{C}}_{10}^{\prime } $$ with the Standard Model and the global significance is at the level of 1.5$$ {\mathcal{C}}_9 $$ σ . The model used also accounts for nonlocal contributions fromB 0→ K *0[τ +τ − → μ +μ − ] rescattering, resulting in the first direct measurement of thebsττ vector effective-coupling .$$ {\mathcal{C}}_{9\tau } $$ Free, publicly-accessible full text available September 1, 2025 -
A search for hidden-charm pentaquark states decaying to a range ofandfinal states, as well as doubly charmed pentaquark states toand, is made using samples of proton-proton collision data corresponding to an integrated luminosity ofrecorded by the LHCb detector at. Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of thebaryon in thedecay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases.
© 2024 CERN, for the LHCb Collaboration 2024 CERN Free, publicly-accessible full text available August 1, 2025 -
The ALICE Collaboration reports measurements of the semi-inclusive distribution of charged-particle jets recoiling from a high transverse momentum (high) charged hadron, inand central Pb-Pb collisions at center-of-mass energy per nucleon–nucleon collisionTeV. The large uncorrelated background in central Pb-Pb collisions is corrected using a data-driven statistical approach which enables precise measurement of recoil jet distributions over a broad range inand jet resolution parameter. Recoil jet yields are reported for, 0.4, and 0.5 in the rangeand, whereis the azimuthal angular separation between hadron trigger and recoil jet. The low-reach of the measurement explores unique phase space for studying jet quenching, the interaction of jets with the quark–gluon plasma generated in high-energy nuclear collisions. Comparison ofdistributions fromand central Pb-Pb collisions probes medium-induced jet energy loss and intra-jet broadening, while comparison of their acoplanarity distributions explores in-medium jet scattering and medium response. The measurements are compared to theoretical calculations incorporating jet quenching.
©2024 CERN, for the ALICE Collaboration 2024 CERN Free, publicly-accessible full text available July 1, 2025 -
The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high) hadron trigger in proton-proton and central Pb-Pb collisions at. A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb-Pb collisions. Recoil jet distributions are reported for jet resolution parameter, 0.4, and 0.5 in the rangeand trigger-recoil jet azimuthal separation. The measurements exhibit a marked medium-induced jet yield enhancement at lowand at large azimuthal deviation from. The enhancement is characterized by its dependence on, which has a slope that differs from zero by. Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation.
© 2024 CERN, for the ALICE Collaboration 2024 CERN Free, publicly-accessible full text available July 1, 2025 -
A bstract A search for the fully reconstructed
$$ {B}_s^0 $$ → μ +μ − γ decay is performed at the LHCb experiment using proton-proton collisions at = 13 TeV corresponding to an integrated luminosity of 5$$ \sqrt{s} $$ . 4 fb− 1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set$$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left[2{m}_{\mu },1.70\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<7.7\times {10}^{-8},&\ m\left({\mu}^{+}{\mu}^{-}\right)\in \left[\textrm{1.70,2.88}\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{-}\gamma \right)<4.2\times {10}^{-8},& m\left({\mu}^{+}{\mu}^{-}\right)\in \left[3.92,{m}_{B_s^0}\right]\textrm{GeV}/{c}^2,\end{array}} $$ at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2
m μ , 1. 70] GeV/c 2dimuon mass region excluding the contribution from the intermediateϕ (1020) meson, and in the region combining all dimuon-mass intervals.Free, publicly-accessible full text available July 1, 2025 -
Free, publicly-accessible full text available June 1, 2025
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Measurements of the-dependent flow vector fluctuations in Pb–Pb collisions atusing azimuthal correlations with the ALICE experiment at the Large Hadron Collider are presented. A four-particle correlation approach [ALICE Collaboration, ] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the-dependent flow vector fluctuations atwith two-particle correlations. Significant-dependent fluctuations of theflow vector in Pb–Pb collisions are found across different centrality ranges, with the largest fluctuations of up tobeing present in the 5% most central collisions. In parallel, no evidence of significant-dependent fluctuations oforis found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more thansignificance in central collisions. These observations incollisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high, which might be biased by-dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be reexamined to improve our understanding of initial conditions, quark–gluon plasma properties, and the dynamic evolution of the created system.
©2024 CERN, for the ALICE Collaboration 2024 CERN Free, publicly-accessible full text available June 1, 2025 -
pairs may be produced in photonuclear collisions, either from the decays of photoproducedmesons or directly as nonresonantpairs. Measurements ofphotoproduction probe the couplings between theand charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction ofpairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of directproduction. There is significantproduction at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass rangeabove theresonance, for rapidityand, the measured coherent photoproduction cross section is. The center-of-mass energy per nucleon of the photon-nucleus (Pb) systemranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected forphotoproduction alone. The mass spectrum is fit to a cocktail consisting ofdecays, directphotoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for directphotoproduction are presented.
© 2024 CERN, for the ALICE Collaboration 2024 CERN Free, publicly-accessible full text available May 1, 2025