0000000000075064
AUTHOR
Giacomo Graziani
showing 38 related works from this author
Search for the exotic Θ+ resonance in the NOMAD experiment
2006
12 pages, 16 figures.-- PACS nrs.: 13.15.+g; 13.60.Le; 13.87.Fh; 14.40.Ev.-- ISI Article Identifier: 000243973100007.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ex/0612063.-- et al.
A more sensitive search for νμ→ντ oscillations in NOMAD
1999
With additional data and improved algorithms, we have enhanced the sensitivity of our appearance search for $\numunutau$ oscillations in the NOMAD detector in the CERN-SPS wide-band neutrino beam. The search uses kinematic criteria to identify $\nutau$ charged current interactions followed by decay of the $\tau^-$ to one of several decay modes. Our ``blind'' analyses of deep-inelastic scattering data taken in 1996 and 1997, combined with consistent reanalyses of previously reported 1995 data, yield no oscillation signal. For the two-family oscillation scenario, we present the contour outlining a 90\% C.L. confidence region in the $\sin^22\theta_{\mu \tau} - \Delta m^2$ plane. At large $\Del…
Model-Independent Evidence forJ/ψpContributions toΛb0→J/ψpK−Decays
2016
The data sample of Lambda(0)(b) -> J/psi pK(-) decays acquired with the LHCb detector from 7 and 8 TeV pp collisions, corresponding to an integrated luminosity of 3 fb(-1), is inspected for the presence of J/psi p or J/psi K- contributions with minimal assumptions about K(-)p contributions. It is demonstrated at more than nine standard deviations that Lambda(0)(b) -> J/psi pK(-) decays cannot be described with K- p contributions alone, and that J/psi K- contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for P-c(+)-> J/psi p charmonium-pentaquark states in the same data sample.
A new measurement of the branching ratio of K(S) → γ γ
2000
Abstract The decay rate of KS → γγ has been measured with the NA48 detector at the CERN SPS. A total of 149 KS → γγ events have been observed. The branching ratio is determined to be (2.58±0.36(stat)±0.22(sys))×10−6.
Search for νμ→νe oscillations in the NOMAD experiment
2003
We present the results of a search for vμ → v e oscillations in the NOMAD experiment at CERN. The experiment looked for the appearance of ve in a predominantly vμ wide-band neutrino beam at the CERN SPS. No evidence for oscillations was found. The 90% confidence limits obtained are Δm2 < 0.4 eV 2 for maximal mixing and sin2(2θ) < 1.4 × 10-3 for large Δm2. This result excludes the LSND allowed region of oscillation parameters with Δm2 ≳ 10 eV2. © 2003 Elsevier B.V. All rights reserved.
A Search for Single Photon Events in Neutrino Interactions
2011
We present a search for neutrino induced events containing a single, exclusive photon using data from the NOMAD experiment at the CERN SPS where the average energy of the neutrino flux is ≃25 GeV. The search is motivated by an excess of electron-like events in the 200-475 MeV energy region as reported by the MiniBooNE experiment. In NOMAD, photons are identified via their conversion to e + e - in an active target embedded in a magnetic field. The background to the single photon signal is dominated by the asymmetric decay of neutral pions produced either in a coherent neutrino-nucleus interaction, or in a neutrino-nucleon neutral current deep inelastic scattering, or in an interaction occurr…
Production properties of $K*(892)\pm$ vector mesons and their spin alignment as measured in the NOMAD experiment
2006
First measurements of K*(892) mesons production properties and their spin alignment in nu_mu charged current (CC) and neutral current (NC) interactions are presented. The analysis of the full data sample of the NOMAD experiment is performed in different kinematic regions. For K*+ and K*- mesons produced in nu_mu CC interactions and decaying into K0 pi+/- we have found the following yields per event: (2.6 +/- 0.2 (stat.) +/- 0.2 (syst.))% and (1.6 +/- 0.1 (stat.) +/- 0.1 (syst.))% respectively, while for the K*+ and K*- mesons produced in nu NC interactions the corresponding yields per event are: (2.5 +/- 0.3 (stat.) +/- 0.3 (syst.))% and (1.0 +/- 0.3 (stat.) +/- 0.2 (syst.))%. The results o…
Observation of the decay KS→π+π−e+e−
2000
Abstract We present the first observation of the decay KS→π+π−e+e− based upon the data collected in 1998 by the NA48 experiment at CERN. We have identified a clean sample of 56 events with negligible background contamination. Using KL→π+π−π0D decays as normalization sample, the branching ratio is measured to be BR(KS→π+π−e+e−)=[4.5±0.7(stat)±0.4(syst)]×10−5. This result is in good agreement with the theoretical expectations from the mechanism of inner bremsstrahlung.
Precision measurement of scaled momentum, charge multiplicity, and thrust in νμN and interactions
1999
By focusing on the notion of electronic document, we differentiate two evolutions which are useful to distinct titles: on the one hand are the documents, which have value of reference. Its administrator will take care to preserve its integrity and its context of production which is strongly significant. On the other hand are resources, evolutionary elements by nature, which the user must be able to appropriate and who must thus be placed at the disposal so that the production is erased, to focus on a logic of exploitation and service.
A study of strange particle production in nu(mu) charged current interactions in the NOMAD experiment
2001
A study of strange particle production in $\nu_\mu$ charged current interactions has been performed using the data from the NOMAD experiment. Yields of neutral strange particles ($K^0_s, \Lambda, \bar{\Lambda}$) have been measured. Mean multiplicities are reported as a function of the event kinematic variables $E_\nu$, $W^2$ and $Q^2$ as well as of the variables describing particle behaviour within a hadronic jet: $x_F$, $z$ and $p_T^2$. Decays of resonances and heavy hyperons with identified $K^0_s$ and $\Lambda$ in the final state have been analyzed. Clear signals corresponding to $\rm {K^\star}^\pm$ $\rm {\Sigma^\star}^\pm$, $\rm \Xi^-$ and $\rm \Sigma^0$ have been observed. A study of s…
First observation of the rareB+→D+K+π−decay
2016
The B+→D+K+π- decay is observed in a data sample corresponding to 3.0 fb-1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. The signal significance is 8σ and the branching fraction is measured to be B(B+→D+K+π-)=(5.31±0.90±0.48±0.35)×10-6, where the uncertainties are statistical, systematic and due to the normalization mode B+→D-K+π+, respectively. The Dalitz plot appears to be dominated by broad structures. Angular distributions are exploited to search for quasi-two-body contributions from B+→D2∗(2460)0K+ and B+→D+K∗(892)0 decays. No significant signals are observed and upper limits are set on their branching fractions.
First experimental study of photon polarization in radiative B0s decays.
2017
The polarization of photons produced in radiative $B^{0}_{s}$ decays is studied for the first time. The data are recorded by the LHCb experiment in $pp$ collisions corresponding to an integrated luminosity of 3fb$^{-1}$ at center-of-mass energies of $7$ and $8$TeV. A time-dependent analysis of the $B^{0}_{s} \to \phi \gamma$ decay rate is conducted to determine the parameter ${\mathcal{A}}^\Delta$, which is related to the ratio of right- over left-handed photon polarization amplitudes in $b \to s \gamma$ transitions. A value of ${\mathcal{A}}^\Delta=-0.98^{\,+0.46\,+0.23}_{\,-0.52\,-0.20}$ is measured. This result is consistent with the Standard Model prediction within two standard deviatio…
Measurement ofCPviolation parameters inB0→DK*0decays
2014
An analysis of B0→DK*0 decays is presented, where D represents an admixture of D0 and D¯0 mesons reconstructed in four separate final states: K−π+, π−K+, K+K− and π+π−. The data sample corresponds to 3.0 fb−1 of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including CP asymmetries. The most precise determination is presented of rB(DK*0), the magnitude of the ratio of the amplitudes of the decay B0→DK+π− with a b→u or a b→c transition, in a Kπ mass region of ±50 MeV/c2 around the K∗(892) mass and for an absolute value of the cosine of the K*0 helicity angle larger than 0.4.
Updated Results from the $\nu_{\tau}$ Appearance Search in NOMAD
2000
Updated results from the appearance searches for $\numunutau$ and $\nuenutau$ oscillations in the full NOMAD data sample are reported. The increased data and the use of more refined kinematic schemes for the $\nutau$ CC selection allow a significant improvement of the overall sensitivity. The ``blind analysis" of both the deep-inelastic and the low multiplicity samples yields no evidence for an oscillation signal. In the two-family oscillation scenario, this sets a 90\% C.L. region in the $\sin^22\theta_{\mu\tau} - \Delta m^2$ plane which includes $\sin^22\theta_{\mu\tau}\ <\ 4.4\times10^{-4}$ at large $\Delta m^2$ and $\Delta m^2 < 0.8$ eV$^2$/$c^4$ at $\sin^22\theta_{\mu \tau}=1$. The cor…
Limit on νe→ντ oscillations from the NOMAD experiment
2000
Abstract In the context of a two-flavour approximation we reinterpret the published NOMAD limit on ν μ → ν τ oscillations in terms of ν e → ν τ oscillations. At 90% C.L. we obtain sin 2 2θ eτ 5.2×10 −2 for large Δm 2 , while for sin 2 2 θ eτ =1 the confidence region includes Δm 2 2 / c 4 .
Studies of the resonance structure inD0→KS0K±π∓decays
2016
Amplitude models are constructed to describe the resonance structure of D0→ K-π+π+π- and D0→ K+π-π-π+ decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb experiment, corresponding to an integrated luminosity of 3.0 fb- 1. The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes D0→ a1(1260) +K- and D0→ K1(1270 / 1400) +π- being prominent in D0→ K-π+π+π- and D0→ K+π-π-π+, respectively. Precise measurements of the lineshape parameters and couplings of the a1(1260) +, K1(1270) - and K(1460) - resonances are made, and a quasi model-independent study of the K(1460) - resonance is performed. The coher…
New results on a search for a 33.9 MeV/c2 neutral particle from π+ decay in the NOMAD experiment
2002
We report on a direct search in NOMAD for a new 33.9 MeV/c^2 neutral particle (X) produced in pion decay in flight, pi-->mu_X followed by the decay X -->nu e^+e^-. Both decays are postulated to occur to explain the time anomaly observed by the KARMEN experiment. From the analysis of the data collected during the 1996?1998 runs with 4.1×10^19 protons on target, a single candidate event consistent with background expectations was found. The search is sensitive to a pion branching ratio BR(pi-->muX >3.7×10^-15, significantly smaller than previous experimental limits.
Measurement of the Ratio of Branching FractionsB(B¯0→D*+τ−ν¯τ)/B(B¯0→D*+μ−ν¯μ)
2015
The branching fraction ratio R(D-*) = B((B) over bar (0) -> D-*(+)tau(-)(nu) over bar (tau))/B((B) over bar (0) -> D-*(+)mu(-)(nu) over bar (mu)) is measured using a sample of proton-proton 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 tau(-) -> mu(-)(nu) over bar (mu)nu(tau). The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate (B) over bar (0) decays gives R(D-*) =…
Search for weakly decaying b -flavored pentaquarks
2018
Investigations of the existence of pentaquark states containing a single $b$ (anti)quark decaying weakly into four specific final states J/$\psi K^+\pi^- p$, J/$\psi K^- \pi^- p$, J/$\psi K^- \pi^+ p$, and $J/\psi \phi (1020) p$ are reported. The data sample corresponds to an integrated luminosity of 3.0/fb in 7 and 8 TeV pp collisions acquired with the LHCb detector. Signals are not observed and upper limits are set on the product of the production cross section times branching fraction with respect to that of the $\Lambda_b$.
Measurement of the polarization in νμ charged current interactions in the NOMAD experiment
2001
The Λ polarization in νμ charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed Λ 's) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the W -boson direction which is enhanced in the target fragmentation region: Px(xF 0)=−0.09±0.06(stat)±0.03(sys) . These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the Λ production plane) has been observed for the first time in…
Measurement of CP asymmetries in two-body B(s)0 -meson decays to charged pions and kaons
2018
The time-dependent CP asymmetries in B0→π+π− and B0s→K+K− decays are measured using a data sample of p p collisions corresponding to an integrated luminosity of 3.0 fb−1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated CP asymmetries in B0→K+π− and B0s→π+K− decays. The results are Cπ+π−=−0.34±0.06±0.01, Sπ+π−=−0.63±0.05±0.01, CK+K−=0.20±0.06±0.02, SK+K−=0.18±0.06±0.02, AΔΓK+K−=−0.79±0.07±0.10, AB0CP=−0.084±0.004±0.003, and AB0sCP=0.213±0.015±0.007, where the first uncertainties are statistical and the second systematic. Evidence for CP violation is found in the B0s→K+K− decay for the first time.
Study of D*+ production in nu_mu charged current interactions in the NOMAD experiment
2002
A search was made among $\nu_\mu$ charged current events collected in the NOMAD experiment for the reaction: $\nu_\mu + N \rightarrow \mu^- + D^{\star+} + hadrons \hookrightarrow D^0 + \pi^+ \hookrightarrow K^- + \pi^+ A $D^{\star+}$ sample composed of 47 events, with 90% purity, was extracted. The $D^{\star+}$ yield in $\nu_\mu$ charged current interactions was measured to be $T = (0.99 \pm 0.15(stat.) \pm 0.11(syst.))$%. The mean fraction of the hadronic jet energy taken by the $D^{\star+}$ is $0.67 \pm 0.02(stat) \pm 0.02(syst.)$. The distributions of the fragmentation variables $z$, ${P_{T}}^2$ and $x_F$ for $D^{\star+}$ are also presented.
Neutrino production of opposite sign dimuons in the NOMAD experiment
2000
The NOMAD Collaboration presents a study of opposite sign dimuon events in the framework of Leading Order QCD. A total of 2714 neutrino- and 115 antineutrino-induced opposite sign dimuon events with $E_{\mu 1}, E_{\mu 2} > 4.5$ GeV, $15 1\;(\mbox{GeV}/\mbox{c})^{2}$ are observed %in the data from the 1995 and 1996 runs. in the Front-Calorimeter of NOMAD during the 1995 and 1996 runs. The analysis yields a value for the charm quark mass of $m_{c} = 1.3^{+0.3\;+0.3}_{-0.3\;-0.3}\;\mbox{GeV}/\m box{c}^{2}$ and for the average semileptonic branching ratio of $B_{c} = 0.095^{+0.007\;+0.014}_{-0.007\;-0.013}$. The ratio of the strange to non-strange sea in the nucleon is measured to be $\kappa = …
Prediction of neutrino fluxes in the NOMAD experiment
2003
The method developed for the calculation of the flux and composition of the West Area Neutrino Beam used by NOMAD in its search for neutrino oscillations is described. The calculation is based on particle production rates computed using a recent version of FLUKA and modified to take into account the cross sections measured by the SPY and NA20 experiments. These particles are propagated through the beam line taking into account the material and magnetic fields they traverse. The neutrinos produced through their decays are tracked to the NOMAD detector. The fluxes of the four neutrino flavours at NOMAD are predicted with an uncertainty of about 8% for nu(mu) and nu(e), 10% for antinu(mu), and…
Measurement of the quadratic slope parameter in the K-L -> 3 pi(0) decay Dalitz plot
2001
A value of (-6.1 +- 0.9_{stat} +- 0.5_{syst})*10^{-3} is obtained for the quadratic slope parameter h in the K_L -> 3\pi^0 decay Dalitz plot at the NA48 experiment at the CERN SPS. The result is based on 14.7*10^6 fully reconstructed K_L -> 3\pi^0 -> 6\gamma decays. This is the most precise measurement of any of the Dalitz plot slope parameters in the charged and neutral kaon decays so far.
Bose-Einstein correlations in charged current muon-neutrino interactions in the NOMAD experiment at CERN
2004
Bose-Einstein Correlations in one and two dimensions have been studied, with high statistics, in charged current muon-neutrino interaction events collected with the NOMAD detector at CERN. In one dimension the Bose-Einstein effect has been analyzed with the Goldhaber and the Kopylov-Podgoretskii phenomenological parametrizations. The Goldhaber parametrization gives the radius of the pion emission region R_G = 1.01+/-0.05(stat)+0.09-0.06(sys) fm and for the chaoticity parameter the value lambda = 0.40+/-0.03(stat)+0.01-0.06(sys). Using the Kopylov-Podgoretskii parametrization yields R_KP = 2.07+/-0.04(stat)+0.01-0.14(sys) fm and lambda_KP = 0.29+/-0.06(stat)+0.01-0.04(sys). Different paramet…
Observation of the rare B(s)(0) + decay from the combined analysis of CMS and LHCb data.
2015
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported licence.-- et al.
Measurement of the decay rate and form factor parameter in the decay KL→e+e−γ
1999
Abstract The decay rate of the neutral K meson KL→e+e−γ has been measured with the NA48 detector at the CERN SPS. A total of 6864 events has been observed with an estimated background of 10 events. The branching ratio is Γ(KL→e+e−γ)/Γ(KL→all) = (1.06±0.02stat±0.02sys±0.04calc)×10−5. The parameter α K ∗ describing the relative strength of the two contributing amplitudes to this decay through intermediate pseudoscalar or vector mesons was measured to be α K ∗ =−0.36±0.06stat±0.02sys.
A precision measurement of charm dimuon production in neutrino interactions from the NOMAD experiment
2013
We present our new measurement of the cross-section for charm dimuon production in neutrino iron interactions based upon the full statistics collected by the NOMAD experiment. After background subtraction we observe 15 344 charm dimuon events, providing the largest sample currently available. The analysis exploits the large inclusive charged current sample - about 9 x 10(6) events after all analysis cuts - and the high resolution NOMAD detector to constrain the total systematic uncertainty on the ratio of charm dimuon to inclusive Charged Current (CC) cross-sections to similar to 2%. We also perform a fit to the NOMAD data to extract the charm production parameters and the strange quark sea…
Amplitude analysis ofB+→J/ψϕK+decays
2017
The first full amplitude analysis of B+→J/ψϕK+ with J/ψ→μ+μ−, ϕ→K+K− decays is performed with a data sample of 3 fb−1 of pp collision data collected at s√=7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ϕK+, and four J/ψϕ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest is best described as a D±sD∗∓s cusp, but a resonant interpretation is also possible with mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state. The mode…
Measurement of the Difference of Time-IntegratedCPAsymmetries inD0→K−K+andD0→π−π+Decays
2016
A search for CP violation in $D^0 \rightarrow K^{-} K^{+} $ and $D^0 \rightarrow \pi^{-} \pi^{+} $ decays is performed using $pp$ collision data, corresponding to an integrated luminosity of $3~fb^{-1}$, collected using the LHCb detector at centre-of-mass energies of 7 and $8~$TeV. The flavour of the charm meson is inferred from the charge of the pion in $D^{*+}\rightarrow D^0\pi^+$ and $D^{*-}\rightarrow \bar{D^0}\pi^{-}$ decays. The difference between the CP asymmetries in $D^0 \rightarrow K^{-} K^{+} $ and $D^0 \rightarrow \pi^{-} \pi^{+} $ decays, $\Delta A_{CP} \equiv A_{CP}(K^{-} K^{+}) - A_{CP}(\pi^{-} \pi^{+})$, is measured to be $\left( -0.10 \pm 0.08(stat) \pm 0.03(syst) \right) \…
Measurement of the W boson mass
1996
The W boson mass is measured using proton-proton collision data at root s = 13 TeV corresponding to an integrated luminosity of 1.7fb(-1) recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon q/p(T) distribution of a sample of W ->mu y decays and the phi* distribution of a sample of Z -> mu mu decays the W boson mass is determined to be
A precise measurement of the muon neutrino nucleon inclusive charged current cross section off an isoscalar target in the energy range 2.5
2008
Abstract We present a measurement of the muon neutrino–nucleon inclusive charged current cross section, off an isoscalar target, in the neutrino energy range 2.5 ⩽ E ν ⩽ 40 GeV . The significance of this measurement is its precision, ±4% in 2.5 ⩽ E ν ⩽ 10 GeV , and ±2.6% in 10 ⩽ E ν ⩽ 40 GeV regions, where significant uncertainties in previous experiments still exist, and its importance to the current and proposed long baseline neutrino oscillation experiments.
Amplitude analysis ofB−→D+π−π−decays
2016
The Dalitz plot analysis technique is used to study the resonant substructures of $B^{-} \to D^{+} \pi^{-} \pi^{-}$ decays in a data sample corresponding to 3.0 ${\rm fb}^{-1}$ of $pp$ collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high $D^{+}\pi^{-}$ mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the $D^{+}\pi^{-}$ S-wave together with virtual contributions from the $D^{*}(2007)^{0}$ and $B^{*0}$ states, and components corresponding to the $D^{*}_{2}(2460)^{0}$, $D^{*}_{1}(2680)^{0}$, $D^{*}_…
A study of strange particles produced in neutrino neutral current interactions in the NOMAD experiment
2004
Results of a detailed study of strange particle production in neutrino neutral current interactions are presented using the data from the NOMAD experiment. Integral yields of neutral strange particles (K0s, Lambda, Lambda-bar) have been measured. Decays of resonances and heavy hyperons with an identified K0s or Lambda in the final state have been analyzed. Clear signals corresponding to K* and Sigma(1385) have been observed. First results on the measurements of the Lambda polarization in neutral current interactions have been obtained.
A measurement of coherent neutral pion production in neutrino neutral current interactions in the NOMAD experiment
2009
We present a study of exclusive neutral pion production in neutrino-nucleus Neutral Current interactions using data from the NOMAD experiment at the CERN SPS. The data correspond to $1.44 \times 10^6$ muon-neutrino Charged Current interactions in the energy range $2.5 \leq E_{\nu} \leq 300$ GeV. Neutrino events with only one visible $\pi^0$ in the final state are expected to result from two Neutral Current processes: coherent $\pi^0$ production, {\boldmath $\nu + {\cal A} \to \nu + {\cal A} + \pi^0$} and single $\pi^0$ production in neutrino-nucleon scattering. The signature of coherent $\pi^0$ production is an emergent $\pi^0$ almost collinear with the incident neutrino while $\pi^0$'s pro…
Observation of Bc+→J/ψD(*)K(*) decays
2017
A search for the decays B + c → J / ψ D ( * ) 0 K + and B + c → J / ψ D ( * ) + K * 0 is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb − 1 . The decays B + c → J / ψ D 0 K + and B + c → J / ψ D * 0 K + are observed for the first time, while first evidence is reported for the B + c → J / ψ D * + K * 0 and B + c → J / ψ D + K * 0 decays. The branching fractions of these decays are determined relative to the B + c → J / ψ π + decay. The B + c mass is measured, using the J / ψ D 0 K + final state, to be 6274.28 ± 1.40 ( stat ) ± 0.32 ( syst ) MeV / c 2 . This is the most precise single measurement of the B + c mass to date.
Study of J/ψ Production in Jets
2017
The production of $J/\psi$ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the $J/\psi$ meson, $z \equiv p_{\rm T}(J/\psi)/p_{\rm T}({\rm jet})$, is measured using jets with $p_{\rm T}({\rm jet}) > 20$ GeV in the pseudorapidity range $2.5 < \eta({\rm jet}) < 4.0$. The observed $z$ distribution for $J/\psi$ mesons produced in $b$-hadron decays is consistent with expectations. However, the results for prompt $J/\psi$ production do not agree with predictions based on fixed-order non-relativistic QCD. This is the first measurement o…