A comprehensive study of the local and nonlocal amplitudes contributing to the decay
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A<sc>bstract</sc> B ^{0}→K ^{*0}(→K ^{+}π ^{−})μ ^{+}μ ^{−}is performed by analysing the phasespace distribution of the decay products. The analysis is based onpp collision data corresponding to an integrated luminosity of 8.4 fb^{−1}collected by the LHCb experiment. This measurement employs for the first time a model of both oneparticle and twoparticle 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$$ {\mathcal{C}}_9 $$ ${C}_{9}$σ deviation from the Standard Model expectation. The Wilson Coefficients ,$$ {\mathcal{C}}_{10} $$ ${C}_{10}$ and$$ {\mathcal{C}}_9^{\prime } $$ ${C}_{9}^{\prime}$ are all in better agreement than$$ {\mathcal{C}}_{10}^{\prime } $$ ${C}_{10}^{\prime}$ with the Standard Model and the global significance is at the level of 1.5$$ {\mathcal{C}}_9 $$ ${C}_{9}$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 effectivecoupling .$$ {\mathcal{C}}_{9\tau } $$ ${C}_{9\tau}$Free, publiclyaccessible full text available September 1, 2025 
A search for hiddencharm pentaquark states decaying to a range of${\mathrm{\Sigma}}_{c}\overline{D}$and${\mathrm{\Lambda}}_{c}^{+}\overline{D}$final states, as well as doubly charmed pentaquark states to${\mathrm{\Sigma}}_{c}D$and${\mathrm{\Lambda}}_{c}^{+}D$, is made using samples of protonproton collision data corresponding to an integrated luminosity of$5.7\text{\hspace{0.17em}}\text{\hspace{0.17em}}{\mathrm{fb}}^{1}$recorded by the LHCb detector at$\sqrt{s}=13\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathrm{TeV}$. Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the${\mathrm{\Lambda}}_{c}^{+}$baryon in the${\mathrm{\Lambda}}_{c}^{+}\to p{K}^{}{\pi}^{+}$decay 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, publiclyaccessible full text available August 1, 2025 
A<sc>bstract</sc> A search for the fully reconstructed
$$ {B}_s^0 $$ ${B}_{s}^{0}$→ μ ^{+}μ ^{−}γ decay is performed at the LHCb experiment using protonproton collisions at = 13 TeV corresponding to an integrated luminosity of 5$$ \sqrt{s} $$ $\sqrt{s}$. 4 fb^{−1}. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set$$ {\displaystyle \begin{array}{cc}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{}\gamma \right)<4.2\times {10}^{8},& m\left({\mu}^{+}{\mu}^{}\right)\in \left[2{m}_{\mu },1.70\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{}\gamma \right)<7.7\times {10}^{8},&\ m\left({\mu}^{+}{\mu}^{}\right)\in \left[\textrm{1.70,2.88}\right]\textrm{GeV}/{c}^2,\\ {}\mathcal{B}\left({B}_s^0\to {\mu}^{+}{\mu}^{}\gamma \right)<4.2\times {10}^{8},& m\left({\mu}^{+}{\mu}^{}\right)\in \left[3.92,{m}_{B_s^0}\right]\textrm{GeV}/{c}^2,\end{array}} $$ $\begin{array}{cc}B\left({B}_{s}^{0}\to {\mu}^{+}{\mu}^{}\gamma \right)<4.2\times {10}^{8},& m\left({\mu}^{+}{\mu}^{}\right)\in \left(2{m}_{\mu},1.70\right)\mathrm{GeV}/{c}^{2},\\ B\left({B}_{s}^{0}\to {\mu}^{+}{\mu}^{}\gamma \right)<7.7\times {10}^{8},& \phantom{\rule{0ex}{0ex}}m\left({\mu}^{+}{\mu}^{}\right)\in \left(\mathrm{1.70,\; 2.88}\right)\mathrm{GeV}/{c}^{2},\\ B\left({B}_{s}^{0}\to {\mu}^{+}{\mu}^{}\gamma \right)<4.2\times {10}^{8},& m\left({\mu}^{+}{\mu}^{}\right)\in \left(3.92,{m}_{{B}_{s}^{0}}\right)\mathrm{GeV}/{c}^{2},\end{array}$at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2
m _{μ}, 1. 70] GeV/c ^{2}dimuon mass region excluding the contribution from the intermediateϕ (1020) meson, and in the region combining all dimuonmass intervals.Free, publiclyaccessible full text available July 1, 2025 
The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an allsoftware trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the allsoftware trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software.more » « lessFree, publiclyaccessible full text available May 1, 2025

The production of 𝜂 and 𝜂′ mesons is studied in protonproton and protonlead collisions collected with the LHCb detector. Protonproton collisions are studied at centerofmass energies of 5.02 and 13TeV and protonlead collisions are studied at a centerofmass energy per nucleon of 8.16TeV. The studies are performed in centerofmass (c.m.) rapidity regions 2.5<𝑦c.m.<3.5 (forward rapidity) and −4.0<𝑦c.m.<−3.0 (backward rapidity) defined relative to the proton beam direction. The 𝜂 and 𝜂′ production cross sections are measured differentially as a function of transverse momentum for 1.5<𝑝T<10GeV and 3<𝑝T<10GeV, respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for 𝜂 and 𝜂′ mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of 𝜂 mesons are also used to calculate 𝜂/𝜋0 crosssection ratios, which show evidence of a deviation from the world average. These studies offer new constraints on massdependent nuclear effects in heavyion collisions, as well as 𝜂 and 𝜂′ meson fragmentation.more » « lessFree, publiclyaccessible full text available February 1, 2025

Garisto, R (Ed.)The ratios of branching fractions R(D*)= B(B0 > D*+tau nu(bar))/ B(B0> D*+mu nu(bar)) and R(D)= B(B0 > D0tau nu(bar))/ B(B0 > D0mu nu(bar)) are measured, assuming isospin symmetry, using a sample of protonproton 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 τ− → μ−ντν¯μ. The measured values are R*D*)= 0.281+/ 0.018+/ 0.024 and R(D0)=0.441+/ 0.060+/ 0.066, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is ρ= −0.43. The 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 modelmore » « less