Engineering topics

Ajaltouni, Z.

Publications and source records attributed to Ajaltouni, Z..

At least 37 records · Page 2

DOE OSTI2024

Search for the rare decay of charmed baryon Λ c + into the p μ + μ − final state

A search for the nonresonant Λ c + → p μ + μ − decay is performed using proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the LHCb experiment, corresponding to an integrated luminosity of 5.4 fb − 1 . No evidence for the decay is found in the dimuon invariant-mass regions where the expected contributions of resonances is subdominant. The upper limit on the branching fraction of the Λ c + → p μ + μ − decay is determined to be 2.9 ( 3.2 ) × 10 − 8 at 90 % ( 95 % ) confidence level. The branching fractions in the dimuon invariant-mass regions dominated by the η , ρ and ω resonances are also determined. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Transverse polarization measurement of Λ hyperons in pNe collisions at $\sqrt{{\textrm{s}}_{\textrm{NN}}}$ = 68.4 GeV with the LHCb detector

A measurement of the transverse polarization of the Λ and $\bar{Λ}$ hyperons in p Ne fixed-target collisions at $\sqrt{{\textrm{s}}_{\textrm{NN}}}$ = 68.4 GeV is presented using data collected by the LHCb detector. The polarization is studied using the decay Λ → p $π$ − together with its charge conjugated process, the integrated values measured are $P_Λ = 0.029 ± 0.019$ (stat) $±$ $0.012$ (syst), $P_{\bar{Λ}} = 0.003 ± 0.023$ (stat) $±$ $0.014$ (syst). Furthermore, the results are shown as a function of the Feynman x variable, transverse momentum, pseudorapidity and rapidity of the hyperons, and are compared with previous measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Search for Time-Dependent C P Violation in D 0 → π + π − π 0 Decays

A measurement of time-dependent C P violation in D 0 → π + π − π 0 decays using a p p collision data sample collected by the LHCb experiment in 2012 and from 2015 to 2018, corresponding to an integrated luminosity of 7.7 fb − 1 , is presented. The initial flavor of each D 0 candidate is determined from the charge of the pion produced in the D * ( 2010 ) + → D 0 π + decay. The decay D 0 → K − π + π 0 is used as a control channel to validate the measurement procedure. The gradient of the time-dependent C P asymmetry Δ Y in D 0 → π + π − π 0 decays is measured to be Δ Y = ( − 1.3 ± 6.3 ± 2.4 ) × 10 − 4 , where the first uncertainty is statistical and the second is systematic, which is compatible with C P conservation. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

First observation of Λ b 0 → Σ c ( * ) + + D ( * ) − K − decays

The four decays, Λ b 0 → Σ c ( * ) + + D ( * ) − K − , are observed for the first time using proton-proton collision data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 6 fb − 1 . By considering the Λ b 0 → Λ c + D ¯ 0 K − decay as reference channel, the following branching fraction ratios are measured to be B ( Λ b 0 → Σ c + + D − K − ) B ( Λ b 0 → Λ c + D ¯ 0 K − ) = 0.282 ± 0.016 ± 0.016 ± 0.005 , B ( Λ b 0 → Σ c * + + D − K − ) B ( Λ b 0 → Σ c + + D − K − ) = 0.460 ± 0.052 ± 0.028 , B ( Λ b 0 → Σ c + + D * − K − ) B ( Λ b 0 → Σ c + + D − K − ) = 2.261 ± 0.202 ± 0.129 ± 0.046 , B ( Λ b 0 → Σ c * + + D * − K − ) B ( Λ b 0 → Σ c + + D − K − ) = 0.896 ± 0.137 ± 0.066 ± 0.018 , where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more datasets to become available following the LHCb upgrade. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Observation of strangeness enhancement with charmed mesons in high-multiplicity p Pb collisions at s NN = 8.16 TeV

The production of prompt D s + and D + mesons is measured by the LHCb experiment in proton-lead ( p Pb ) collisions in both the forward ( 1.5 < y * < 4.0 ) and backward ( − 5.0 < y * < − 2.5 ) rapidity regions at a nucleon-nucleon center-of-mass energy of s NN = 8.16 TeV . The nuclear modification factors of both D s + and D + mesons are determined as a function of transverse momentum, p T , and rapidity. In addition, the D s + to D + cross section ratio is measured as a function of the primary charged particle multiplicity in the event. An enhanced D s + to D + production in high-multiplicity events is observed for the whole measured p T range, in particular at low p T and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity p Pb collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Search for prompt production of pentaquarks in charm hadron final states

A search for hidden-charm pentaquark states decaying to a range of Σ c D ¯ and Λ c + D ¯ final states, as well as doubly charmed pentaquark states to Σ c D and Λ c + D , is made using samples of proton-proton collision data corresponding to an integrated luminosity of 5.7 fb − 1 recorded by the LHCb detector at s = 13 TeV . Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the Λ c + baryon in the Λ c + → p K − π + 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

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Search for the $ {B}_s^0$ → μ + μ – $\gamma$ decay

A search for the fully reconstructed ${B}_s^0$ → μ + μ – γ decay is performed at the LHCb experiment using proton-proton collisions at $\sqrt{s}$ = 13 TeV corresponding to an integrated luminosity of 5.4 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 [2m μ , 1.70] GeV/c 2 dimuon mass region excluding the contribution from the intermediate Φ(1020) meson, and in the region combining all dimuon-mass intervals.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Modification of χ c 1 ( 3872 ) and ψ ( 2 S ) Production in p Pb Collisions at s NN = 8.16 TeV

The LHCb Collaboration measures production of the exotic hadron χ c 1 ( 3872 ) in proton-nucleus collisions for the first time. Comparison with the charmonium state ψ ( 2 S ) suggests that the exotic χ c 1 ( 3872 ) experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify χ c 1 ( 3872 ) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Measurement of forward charged hadron flow harmonics in peripheral PbPb collisions at s N N = 5.02 TeV with the LHCb detector

Flow harmonic coefficients, v n , which are the key to studying the hydrodynamics of the quark-gluon plasma (QGP) created in heavy-ion collisions, have been measured in various collision systems and kinematic regions and using various particle species. The study of flow harmonics in a wide pseudorapidity range is particularly valuable to understand the temperature dependence of the shear viscosity to entropy density ratio of the QGP. This paper presents the first LHCb results of the second- and the third-order flow harmonic coefficients of charged hadrons as a function of transverse momentum in the forward region, corresponding to pseudorapidities between 2.0 and 4.9, using the data collected from PbPb collisions in 2018 at a center-of-mass energy of 5.02 TeV . The coefficients measured using the two-particle angular correlation analysis method are smaller than the central-pseudorapidity measurements at ALICE and ATLAS from the same collision system but share similar features. ©2024 CERN, for the LHCb Collaboration 2024 CERN

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Measurements of the branching fraction ratio $$ \mathcal{B}\left(\phi \to {\mu}^{+}{\mu}^{-}\right)/\mathcal{B}\left(\phi \to {\textrm{e}}^{+}{\textrm{e}}^{-}\right) $$ with charm meson decays

Abstract Measurements of the branching fraction ratio$$ \mathcal{B}\left(\phi \to {\mu}^{+}{\mu}^{-}\right)/\mathcal{B}\left(\phi \to {e}^{+}{e}^{-}\right) $$ B ϕ → μ + μ − / B ϕ → e + e − with$$ {D}_s^{+}\to {\pi}^{+}\phi $$ D s + → π + ϕ andD + → π + ϕdecays, denoted$$ {R}_{\phi \pi}^s $$ R ϕπ s and$$ {R}_{\phi \pi}^d $$ R ϕπ d , are presented. The analysis is performed using a dataset corresponding to an integrated luminosity of 5.4 fb −1 ofppcollision data collected with the LHCb experiment. The branching fractions are normalised with respect to theB + →K + J/ψ(→e + e − ) andB + →K + J/ψ(→μ + μ − ) decay modes. The combination of the results yields$$ {R}_{\phi \pi}=1.022\pm 0.012\left(\textrm{stat}\right)\pm 0.048\left(\textrm{syst}\right). $$ R ϕπ = 1.022 ± 0.012 stat ± 0.048 syst . The result is compatible with previous measurements of theϕ→ℓ + ℓ − branching fractions and predictions based on the Standard Model.

Physics↗

DOE OSTI2024

Determination of short- and long-distance contributions in B 0 → K * 0 μ + μ − decays

An amplitude analysis of the B 0 → K * 0 μ + μ − decay is presented. The analysis is based on data collected by the LHCb experiment from proton-proton collisions at s = 7 , 8 and 13 TeV, corresponding to an integrated luminosity of 4.7 fb − 1 . For the first time, Wilson coefficients and nonlocal hadronic contributions are accessed directly from the unbinned data, where the latter are parametrized as a function of q 2 with a polynomial expansion. Wilson coefficients and nonlocal hadronic parameters are determined under two alternative hypotheses: the first relies on experimental information alone, while the second one includes information from theoretical predictions for the nonlocal contributions. Both models obtain similar results for the parameters of interest. The overall level of compatibility with the Standard Model is evaluated to be between 1.8 and 1.9 standard deviations when looking at the C 9 Wilson coefficient alone, and between 1.3 and 1.4 standard deviations when considering the full set of C 9 , C 10 , C 9 ′ and C 10 ′ Wilson coefficients. The ranges reflect the theoretical assumptions made in the analysis. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Amplitude Analysis of the B 0 → K * 0 μ + μ − Decay

An amplitude analysis of the B 0 → K * 0 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. For the first time, the coefficients associated to short-distance physics effects, sensitive to processes beyond the standard model, are extracted directly from the data through a q 2 -unbinned amplitude analysis, where q 2 is the μ + μ − invariant mass squared. Long-distance contributions, which originate from nonfactorizable QCD processes, are systematically investigated, and the most accurate assessment to date of their impact on the physical observables is obtained. The pattern of measured corrections to the short-distance couplings is found to be consistent with previous analyses of b - to s -quark transitions, with the largest discrepancy from the standard model predictions found to be at the level of 1.8 standard deviations. The global significance of the observed differences in the decay is 1.4 standard deviations. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Fraction of χ c Decays in Prompt J / ψ Production Measured in p Pb Collisions at s NN = 8.16 TeV

The fraction of χ c 1 and χ c 2 decays in the prompt J / ψ yield, F χ c → J / ψ = σ χ c → J / ψ / σ J / ψ , is measured by the LHCb detector in p Pb collisions at s NN = 8.16 TeV . The study covers the forward ( 1.5 < y * < 4.0 ) and backward ( − 5.0 < y * < − 2.5 ) rapidity regions, where y * is the J / ψ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6 ± 0.3 and 20.8 ± 0.5 nb − 1 , respectively. The result is presented as a function of the J / ψ transverse momentum p T , J / ψ in the range 1 < p T , J / ψ < 20 GeV / c . The F χ c → J / ψ fraction at forward rapidity is compatible with the LHCb measurement performed in p p collisions at s = 7 TeV , whereas the result at backward rapidity is 2.4 σ larger than in the forward region for 1 < p T , J / ψ < 3 GeV / c . The increase of F χ c → J / ψ at low p T , J / ψ at backward rapidity is compatible with the suppression of the ψ ( 2 S ) contribution to the prompt J / ψ yield. The lack of in-medium dissociation of χ c states observed in this study sets an upper limit of 180 MeV on the free energy available in these p Pb collisions to dissociate or inhibit charmonium state formation. © 2024 CERN, for the LHCb Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Measurement of the CKM angle $\gamma $ in the ${{{B} ^0} \rightarrow {D} {{K} ^{*0}}}$ channel using self-conjugate ${D} \rightarrow {{K} ^0_{\textrm{S}}} h^+ h^-$ decays

A model-independent study of $C\!P$ violation in ${{B} ^0} \rightarrow {D} {{K} ^{*0}}$ decays is presented using data corresponding to an integrated luminosity of 9 fb -1 collected by the LHCb experiment at centre-of-mass energies of $\sqrt{s}=7, \, 8$ and 13 TeV. The CKM angle $\gamma$ is determined by examining the distributions of signal decays in phase-space bins of the self-conjugate ${D} \rightarrow {{K} ^0_{\textrm{S}}} h^+ h^-$ decays, where $h = \pi , K$. Observables related to $C\!P$ violation are measured and the angle $\gamma$ is determined to be $\gamma =(49^{+ 22}_{-19})^\circ$. Measurements of the amplitude ratio and strong-phase difference between the favoured and suppressed ${B} ^0$ decays are also presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Observation of Cabibbo-Suppressed Two-Body Hadronic Decays and Precision Mass Measurement of the Ω c 0 Baryon

The first observation of the singly Cabibbo-suppressed Ω c 0 → Ω − K + and Ω c 0 → Ξ − π + decays is reported, using proton-proton collision data at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb − 1 , collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be B ( Ω c 0 → Ω − K + ) B ( Ω c 0 → Ω − π + ) = [ 6.08 ± 0.51 ( stat ) ± 0.40 ( syst ) ] % , B ( Ω c 0 → Ξ − π + ) B ( Ω c 0 → Ω − π + ) = [ 15.81 ± 0.87 ( stat ) ± 0.44 ( syst ) ± 0.16 ( ext ) ] % . In addition, using the Ω c 0 → Ω − π + decay channel, the Ω c 0 baryon mass is measured to be M ( Ω c 0 ) = 2695.28 ± 0.07 ( stat ) ± 0.27 ( syst ) ± 0.30 ( ext ) MeV , improving the precision of the previous world average by a factor of 4. © 2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗

DOE OSTI2024

Enhanced Production of Λ b 0 Baryons in High-Multiplicity p p Collisions at s = 13 TeV

The production rate of Λ b 0 baryons relative to B 0 mesons in p p collisions at a center-of-mass energy s = 13 TeV is measured by the LHCb experiment. The ratio of Λ b 0 to B 0 production cross sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity. At low multiplicity, the ratio measured at LHCb is consistent with the value measured in e + e − collisions, and increases by a factor of ∼ 2 with increasing multiplicity. At relatively low transverse momentum, the ratio of Λ b 0 to B 0 cross sections is higher than what is measured in e + e − collisions, but converges with the e + e − ratio as the momentum increases. These results imply that the evolution of heavy b quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed. © 2024 CERN, for the LHCb Collaboration 2024 CERN

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2024

Measurement of the Z boson production cross-section in pp collisions at $ \sqrt{s}$ = 5.02 TeV

The first measurement of the Z boson production cross-section at centre-of-mass energy $\sqrt{s}$ = 5.02 TeV in the forward region is reported, using pp collision data collected by the LHCb experiment in year 2017, corresponding to an integrated luminosity of 100 ± 2 pb –1 . The production cross-section is measured for final-state muons in the pseudorapidity range 2.0 < η < 4.5 with transverse momentum p T > 20 GeV/c. The integrated cross-section is determined to be ${\sigma}_{Z\to \mu +\mu -}=39.6\pm 0.7\left(\textrm{stat}\right)\pm 0.6\left(\textrm{syst}\right)\pm 0.8\left(\textrm{lumi}\right)\textrm{pb}$ for the di-muon invariant mass in the range 60 < M μμ < 120 GeV/c 2 . This result and the differential cross-section results are in good agreement with theoretical predictions at next-to-next-to-leading order in the strong coupling constant. Based on a previous LHCb measurement of the Z boson production cross-section in pPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, the nuclear modification factor RpPb is measured for the first time at this energy. The measured values are ${1.2}_{-0.3}^{+0.5}$ (stat) ± 0.1(syst) in the forward region (1.53 < ${y}_{\mu}^{\ast }$ < 4.03) and ${3.6}_{-0.9}^{+1.6}$ (stat) ± 0.2(syst) in the backward region (–4.97 < ${y}_{\mu}^{\ast }$ < –2.47), where ${y}_{\mu}^{\ast }$ represents the muon rapidity in the centre-of-mass frame.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2024

Production of η and η ′ mesons in p p and p Pb collisions

The production of η and η ′ mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of 5.02 and 13 TeV and proton-lead collisions are studied at a center-of-mass energy per nucleon of 8.16 TeV . The studies are performed in center-of-mass (c.m.) rapidity regions 2.5 < y c . m . < 3.5 (forward rapidity) and − 4.0 < y c . 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 < p T < 10 GeV and 3 < p T < 10 GeV , 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 / π 0 cross-section ratios, which show evidence of a deviation from the world average. These studies offer new constraints on mass-dependent nuclear effects in heavy-ion collisions, as well as η and η ′ meson fragmentation. ©2024 CERN, for the LHCb Collaboration 2024 CERN

Aaij, R. (ORCID:0000000305331952)↗