arXiv subjects

M. Andreotti

Publications and source records attributed to M. Andreotti.

At least 55 records · Page 3Linked to original sources

arXiv2026

New measurements of $B^+_c$ decays into single charm final states

Using proton-proton collision data corresponding to an integrated luminosity of $9 \,\textrm{fb}^{-1}$ collected by the LHCb experiment, searches are performed for $B^+_c$ mesons decaying to a charm and a charmless meson pair. Five products of branching fraction, ${\cal B}(B^+_c\!\to DX)$, and fragmentation ratio $f_c\big/f_u$ are reported, \begin{align*} R_{D^+ K^{*0}} &= ( 1.42 \pm 0.23 \pm 0.07 \pm 0.11 ) \times 10^{-6}, \\ R_{D^{*0} K^+} &= (1.46 \pm 0.30 \pm 0.11 \pm 0.05 ) \times 10^{-6}, \\ R_{D^+_s ϕ}\ \ \ &= ( 4.0\pm 1.3 \pm 0.2 \pm 0.5) \times 10^{-7 }, \\ R_{D^0 K^+}\ &= ( 9.7 \pm 1.0 \pm 0.4 \pm 0.3 ) \times 10^{-7}, \\ R_{D^0 π^+}\ &<\ 1.4 \times 10^{-7}\ \text{at 95\% CL}. \end{align*} In each case, the first uncertainty is statistical, the second is systematic and the third includes external uncertainties. The first result is a first observation, the second and third exhibit clear evidence and the fourth improves the precision of previous measurements by a factor two. Additionally, the $CP$ asymmetry in $B^+_c\!\to D^0 K^+$ decays is measured and found to be compatible with zero.

hep-ex↗

arXiv2026

A Bayesian approach to the long-baseline neutrino oscillation sensitivity of DUNE

The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is evaluated using a Bayesian Markov Chain Monte Carlo (MCMC) approach. This analysis uses the same underlying sensitivity inputs as previous DUNE studies [Eur. Phys. J. C 80, 978 (2020)], and therefore does not present updated DUNE sensitivities, but instead explores the additional inferences accessible using a Bayesian approach. We present four-dimensional posterior probability distributions of the oscillation parameters, highlighting the breadth of correlation in the parameter space of interest, especially between $\sin^2 θ_{23}$ and $\sin^2 θ_{13}$. We exploit the flexibility of the Bayesian framework to incorporate parameter constraints post hoc and assess the impact of applying a reactor short-baseline $θ_{13}$ constraint. A significant increase in the sensitivity to the $θ_{23}$ octant is found when including the constraint. Posterior distributions of derived quantities can be easily constructed from MCMC results. This work presents the first study of DUNE's sensitivity to the Jarlskog invariant, $J$, a quantity that provides a parametrisation-independent measure of charge-parity violation in the leptonic sector.

hep-ex↗

arXiv2026

Modification of $Υ$ production in $p$O and OO collisions at LHCb

The production rates of $\mathitΥ(2S)$ and $\mathitΥ(3S)$ mesons relative to that of the $\mathitΥ(1S)$ state are measured in $pp$, $p$O, and OO collisions by the LHCb collaboration. The ratios measured in $pp$ data are consistent with previous LHCb measurements at different center-of-mass energies. Only slight relative suppression of the $\mathitΥ(2S)$ and $\mathitΥ(3S)$ states is found in $p$O collisions, while in OO collisions the $\mathitΥ(2S)$ is suppressed by a factor of $\sim2$, with evidence for suppression of the $\mathitΥ(3S)$. The significant suppression in OO data, compared to the small effect in $p$O data, shows the emergence of additional suppression mechanisms in the relatively small OO collision system. Models incorporating quark-gluon plasma formation in OO collisions successfully describe the data. Implications for the interplay between cold nuclear matter effects and color screening in a deconfined quark-gluon plasma are discussed.

nucl-ex↗

arXiv2026

Test of lepton flavour universality with $B^0\to K^{*0}\ell^+\ell^-$ decays at large dilepton invariant mass

Muon-electron universality is tested in $B^0 \to K^{*0} \ \ell^+ \ell^-$ decays, in the dilepton-invariant-mass region above the $ψ(2S)$ resonance. The analysis uses beauty mesons produced in proton-proton collisions recorded by the LHCb detector at center-of-mass energies of 7, 8, and 13 $\text{TeV}$, corresponding to an integrated luminosity of 9 $\text{fb}^{-1}$. The ratio of branching fractions between the muon and electron channels $R_{K^{*0}}$ is measured to be $1.08\,^{+0.14}_{-0.12}\text{(stat)} \ \pm 0.07\text{(syst)}$ for a dilepton-invariant-mass squared above 14.0 $\text{GeV}^{2}/\text{c}^{4}$, consistent with the standard model prediction. This result represents the most precise measurement of $R_{K^{*0}}$ in this region and the first such measurement performed at a hadron collider.

hep-ex↗

arXiv2026

Evidence for the rare decay $B^{+} \to \bar Λp μ^{+} μ^{-}$

A search for the rare decay $B^{+} \to \bar Λp μ^{+} μ^{-}$ is performed using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of $\sqrt{s}= 13$ TeV, corresponding to an integrated luminosity of 5.4 fb$^-1$. An excess of events is found with respect to the background-only expectation, with a signal significance of 3.5 standard deviations, in the low invariant-mass region of $m(\bar Λp)<2.8$ GeV/$c^2$. The branching fraction is measured to be ${\cal B}_{\rm low}({B^{+}}\to {\bar Λp μ^{+} μ^{-}})=\left(1.70 ^{+0.65}_{-0.56}(\rm stat) \pm 0.17(\rm syst) \pm 0.14(\rm ext)\right) \times 10^{-8}$, where the last uncertainty is due to external inputs on ${\cal B}(B^+\to{J/ψ\bar Λp})\times {\cal B}({J/ψ}\to{μ^+μ^-})$. With no significant signal observed in the high $m(\bar Λp)$ region above 2.8 GeV/$c^2$, an upper limit is set to be ${\cal B}_{\rm high}(B^{+}\to {\bar Λp μ^{+} μ^{-}})<2.8\,(3.7) \times 10^{-9}$ at the $90\%$ ($95\%$) confidence level.

hep-ex↗

arXiv2026

Search for $C\!P$ violation in $D^+ \to ϕπ^+$ decays

A search for charge-parity ($C\!P$) violation in the Cabibbo-suppressed $D^+ \to ϕπ^+$ decay is presented, using proton-proton collision data corresponding to an integrated luminosity of $6\text{ fb}^{-1}$, collected at a centre-of-mass energy of $13\text{ TeV}$ with the LHCb detector during Run 2. An abundant sample of $D^+ \to K_{\rm S}^0 π^+$ decays is employed to correct for asymmetries arising from the production of the charmed meson and from detection effects associated with the charged pion accompanying the $ϕ$ meson. Asymmetries induced by interference of multiple processes, such as neutral kaon mixing, regeneration of neutral kaons, and interference between the Cabibbo-favoured $D^+ \to \overline{K}^0 π^+$ and the doubly Cabibbo-suppressed $D^+ \to {K}^0 π^+$ decay, are subtracted. The direct $C\!P$ asymmetry in the $D^+ \to ϕπ^+$ decay is measured to be \begin{equation*} a_{C\!P}(D^+ \to ϕπ^+) = \left(0.1 \pm 4.9\text{ (stat)} \pm 2.4\text{ (syst)} \right)\times 10^{-4}. \end{equation*} For the first time at a hadron collider, the modulus of the ratio and the relative strong phase of the $D^+ \to {K}^0 π^+$ to $D^+ \to \overline{ K}^0 π^+$ decay amplitudes are also investigated. Two-dimensional confidence intervals are reported for these parameters.

hep-ex↗

arXiv2026

Operation and performance of ProtoDUNE Dual Phase liquid argon time projection chamber

ProtoDUNE-DP was the largest ever built Liquid Argon Time Projection Chamber (LArTPC) operating in Dual-Phase (DP) mode, with a liquid target and charge read-out placed in the gas. It had an active volume of $6\times6\times6$\,m$^3$ corresponding to an active mass of 300\,t (total LAr mass of 720\,t), constructed at the CERN Neutrino Platform and took data from 2019 to 2020 with cosmic muons. In ProtoDUNE-DP the electric drift field is oriented in the vertical direction, causing the electrons to drift vertically towards the anode at the top. The ionization charge is then extracted into the gaseous argon above the liquid surface, amplified by Townsend avalanches, and collected by the charge readout planes. The detector experienced significant technical problems affecting the long-term operation of the Charge Readout Planes, formed by the Large Electron Multipliers, but other critical segments demonstrated required performance including the delivery of -300 kV to the TPC cathode, verification of replaceable charge read-out electronics, and operation of the photon detection system. ProtoDUNE-DP experience resulted in improved designs of the Vertical Drift LArTPC.

physics.ins-det↗

arXiv2026

Observation of $CP$ violation in $B^{0}\!\to{J\mskip-3mu/\mskip-2muψ}ρ(770)^0$ decays

The time-dependent $CP$ asymmetry in $B^{0}\!\to{J\mskip-3mu/\mskip-2muψ}ρ(770)^0$ decays is measured using proton-proton collision data corresponding to an integrated luminosity of $6\,\text{fb}^{-1}$, collected with the LHCb detector at a center-of-mass energy of $13\,\text{TeV}$ during the years 2015-2018. The $CP$-violation parameters for this process are determined to be $2β^{\rm eff}_{c\bar{c}d} = 0.710 \pm 0.084 \pm 0.051\,\text{rad}$ and $|λ| = 1.019 \pm 0.034 \pm 0.024$, where the first uncertainty is statistical and the second systematic. This constitutes the first observation of time-dependent $CP$ violation in $B^{0}\!\to{J\mskip-3mu/\mskip-2muψ}ρ(770)^0$ decays. Assuming approximate SU(3) flavor symmetry, these results are combined with the previous consistent LHCb measurement to set the most stringent constraint on the penguin contribution, $Δϕ_{s}$, to the $CP$-violating phase $ϕ_{s}$ in $B^{0}_{s}\!\to{J\mskip-3mu/\mskip-2muψ}ϕ(1020)$ decays, yielding $Δϕ_{s} = 5.0 \pm 4.6\,\text{mrad}$.

hep-ex↗

arXiv2026

Search for the decays $B^+_{(c)} \to μ^+ ν_μγ$

A search for the radiative leptonic decays $B^+\toμ^+ν_μγ$ and $B^+_c\toμ^+ν_μγ$ is performed using proton-proton collision data collected with the LHCb experiment at a center-of-mass energy of $13~{\rm TeV}$, corresponding to an integrated luminosity of $5.4~{\rm fb}^{-1}$. No evidence for an excess of events over background is observed for either signal decay. Upper limits at 90% confidence level are set on the branching fractions: \begin{align} {\cal{B}}(B^+\toμ^+ν_μγ)_{E_γ^\ast > 1\,\rm{GeV}} &< 4.0 \times 10^{-6},\\ {\cal{B}}(B_c^+\toμ^+ν_μγ)_{E_γ^\ast > 1\,\rm{GeV}} &< 1.6 \times 10^{-3}, \end{align} where the photon energy in the $B$-meson rest frame, $E_γ^\ast$, is required to be greater than $1~{\rm GeV}$. This constitutes the first search for these decays at a hadron collider and the first experimental investigation of the $B_c^+\toμ^+ν_μγ$ decay to date.

hep-ex↗

arXiv2026

Study of the $B^0 \to Λ_c^+ \barΛ_c^- K_S^0$ decay

The decay $B^0 \to Λ_c^+ \barΛ_c^- K_S^0$ is studied at LHCb for the first time using proton-proton collision data recorded by the LHCb experiment at a center-of-mass energy of $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The branching ratio relative to the decay $B^+ \to Λ_c^+ \barΛ_c^- K^+$ is measured to be $$ \frac{{\cal B}(B^0 \to Λ_c^+ \barΛ_c^- K_S^0)}{{\cal B}(B^+ \to Λ_c^+ \barΛ_c^- K^+)} = 0.53 \pm 0.05 \pm 0.05, $$ where the first uncertainty is statistical and the second is systematic. Evidence is found for contributions from two resonant states, $Ξ_c(2923)^+$ and $Ξ_c(2939)^+$, in the $Λ_c^+ K_S^0$ system. The two states show a significance of $3.9σ$ relative to the nonresonant hypothesis. These two $Ξ_c^+$ states are consistent with being the isospin partners of the states observed in $Λ_c^+ K^-$ system.

hep-ex↗

arXiv2026

Observation of new excited $\itΣ_{c}^{0}$ states in the $B^-\rightarrow \itΛ^+_c\overline{p}π^{-}$ decay

An amplitude analysis of the $B^-\rightarrow \itΛ^+_c\overline{p}π^{-}$ decay is performed using proton-proton collision data, corresponding to an integrated luminosity of $9\text{ fb}^{-1}$, collected with the \mbox{LHCb} detector at center-of-mass energies of 7, 8, and 13$\text{ TeV}$. In the $\itΛ^+_cπ^{-}$ invariant-mass spectrum, the known $\itΣ_c(2455)^0$, $\itΣ_c(2520)^0$, $\itΣ_c(2800)^0$ baryons are observed, along with two new states: $\itΣ_c(2900)^0$ and $\itΣ_c(3200)^0$. The masses and widths of the three high-mass states, modeled with Breit--Wigner line shapes, are determined. This result expands the landscape of charm baryon spectroscopy and provides crucial data for understanding charm baryon structure and dynamics.

hep-ex↗

arXiv2026

Comprehensive analysis of the $B^0\to K^{*0}μ^+μ^-$ decay

An analysis of the $B^{0}\rightarrow K^{*0}(\to K^+ π^-)μ^{+}μ^{-}$ decay is presented using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 8.4 fb$^{-1}$. The full set of $CP$-averaged and $CP$-asymmetric angular observables is determined in bins of the invariant mass squared of the dimuon system, as well as the branching fraction relative to the $B^{0}\rightarrow J/ψ(\toμ^{+}μ^{-})K^+π^-$ decay. For the first time, the full set of observables pertaining to the $K^+π^-$ S-wave contribution to the final state are presented and consideration is given to effects arising from the mass of the muons. The measurements of the $CP$-averaged observables and the branching fractions continue to exhibit the pattern of tensions with the Standard Model predictions that have been seen in previous analyses that use part of the dataset considered in this Letter.

hep-ex↗

arXiv2026

Observation of the doubly charmed baryon $\itΞ_{cc}^+$ with the LHCb Run 3 detector

The first observation of the doubly charmed baryon $\itΞ_{cc}^+$ is reported through its decay to the $\itΛ_c^+ K^-π^+$ final state, with a statistical significance exceeding seven standard deviations. The observation is made using proton-proton collision data collected in 2024 with the LHCb Run 3 detector at a center-of-mass energy of 13.6 TeV, corresponding to a total integrated luminosity of $6.9\,\mathrm{fb}^{-1}$. The $\itΞ_{cc}^+$ mass is measured to be $3619.97 \pm 0.83 \pm 0.26 \,^{+1.90}_{-1.30}\,\mathrm{MeV}/c^2$, where the first uncertainty is statistical, the second is systematic, and the third is due to the unknown $\itΞ_{cc}^+$ lifetime, which is assumed to lie in the range 15-160 fs with a baseline value of 45 fs. The difference between the masses of the $\itΞ_{cc}^+$ and $\itΞ_{cc}^{++}$ baryons is determined to be $-1.77 \pm 0.84 \pm 0.15 \,^{+1.90}_{-1.30}\,\mathrm{MeV}/c^2$. This is the first observation of a new particle made with the LHCb Run 3 detector.

hep-ex↗

arXiv2026

First measurement of time-dependent $CP$ violation in the flavor-changing neutral-current decay $B^{0}\rightarrow K_{S}^{0}μ^{+}μ^{-}$

A flavor-tagged time-dependent analysis of $B^{0}\rightarrow K_{S}^{0}μ^{+}μ^{-}$ decays is performed across the full dimuon mass range excluding the $J/ψ$ and $ψ(2S)$ resonance regions. The analysis uses proton-proton collision data collected by the LHCb experiment in 2011--2018 at center-of-mass energies of 7, 8 and 13TeV, corresponding to an integrated luminosity of 9$fb^{-1}$. The CP violation parameters are determined to be $C=-0.13 \pm 0.32 \pm 0.04$ and $S= +0.82\pm 0.29 \pm 0.05$, where the first uncertainties are statistical and the second are systematic. The results are consistent with the Standard Model prediction. This is the first experimental study of time-dependent CP violation in $b\rightarrow sl^{+}l^{-}$ processes.

hep-ex↗

arXiv2026

Differential measurement of the branching fraction and $C\!P$ asymmetry of the decay $B^\pm\to π^\pmμ^+μ^-$

Differential measurements of the branching fraction and $C\!P$ asymmetry of the decay $B^\pm\to π^\pmμ^+μ^-$ are performed in intervals of the dimuon mass squared, $q^2$, using proton-proton collision data corresponding to an integrated luminosity of 9 fb$^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of 7 TeV, 8 TeV and 13 TeV. The ratios of the branching fractions of $B^\pm\to π^\pmμ^+μ^-$ and $B^\pm\to K^\pmμ^+μ^-$ decays are also reported in the same $q^2$ intervals. The measured branching fractions are compatible with the predictions of the Standard Model, with consistency varying between 1.4$σ$ and 3.8$σ$ depending on the model assumptions.

hep-ex↗

arXiv2026

Operation of a Modular 3D-Pixelated Liquid Argon Time-Projection Chamber in a Neutrino Beam

The 2x2 Demonstrator, a prototype for the Deep Underground Neutrino Experiment (DUNE) liquid argon (LAr) Near Detector, was exposed to the Neutrinos from the Main Injector (NuMI) neutrino beam at Fermi National Accelerator Laboratory (Fermilab). This detector prototypes a new modular design for a liquid argon time-projection chamber (LArTPC), comprised of a two-by-two array of four modules, each further segmented into two optically-isolated LArTPCs. The 2x2 Demonstrator features a number of pioneering technologies, including a low-profile resistive field shell to establish drift fields, native 3D ionization pixelated imaging, and a high-coverage dielectric light readout system. The 2.4 tonne active mass detector is flanked upstream and downstream by supplemental solid-scintillator tracking planes, repurposed from the MINERvA experiment, which track ionizing particles exiting the argon volume. The antineutrino beam data collected by the detector over a 4.5 day period in 2024 include over 30,000 neutrino interactions in the LAr active volume-the first neutrino interactions reported by a DUNE detector prototype. During its physics-quality run, the 2x2 Demonstrator operated at a nominal drift field of 500 V/cm and maintained good LAr purity, with a stable electron lifetime of approximately 1.25 ms. This paper describes the detector and supporting systems, summarizes the installation and commissioning, and presents the initial validation of collected NuMI beam and off-beam self-triggers. In addition, it highlights observed interactions in the detector volume, including candidate muon anti-neutrino events.

physics.ins-det↗

arXiv2026

$B$-jet fragmentation with $B^{\pm} \to J/ψK^{\pm}$ decays in $\sqrt{s} = 13$ TeV $pp$ collisions at LHCb

The collinear and transverse-momentum-dependent jet fragmentation function and the radial profile for $B^{\pm}$ mesons in jets are measured. The $B^{\pm}$ mesons are reconstructed through the $J/ψ(\to μ^{+} μ^{-}) K^{\pm}$ decay channel using proton-proton collision data collected during 2016-2018 with the LHCb detector at a center-of-mass energy of $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of $5.4$ fb$^{-1}$. The results complement recent measurements of jet fragmentation functions for heavy-flavor hadrons and suggest a growing contribution of gluon fragmentation to $B^{\pm}$ mesons as the jet transverse momentum increases.

hep-ex↗

arXiv2026

Differential decay rate of $B^+ \to J/ψK^+$ with the LHCb Upgrade I experiment

The normalised decay rate of $B^+ \to J/ψ(\to μ^+μ^-) K^+$ is measured as a function of the lepton helicity angle using a data sample corresponding to an integrated luminosity of $1.1 \text{fb}^{-1}$ collected during October 2024 with the upgraded (Upgrade I) LHCb detector. This angular distribution can be parameterised by two coefficients, the forward-backward asymmetry, $A_{FB}$, and the flatness parameter, $F_{H}$, whose values are constrained by conservation of angular momentum. These coefficients are measured both integrated and differentially across various kinematic and detector-response variables, and the results are found to be in good agreement with expectations. These measurements show that the detector response of the LHCb Upgrade I experiment is understood to the precision required to reliably extract the angular coefficients associated with rare $b \to s μ^+μ^-$ and $b \to d μ^+μ^-$ transitions, which are particularly sensitive to physics beyond the Standard Model.

hep-ex↗