S. Aiola's research while affiliated with National Institute for Subatomic Physics and other places

Publications (50)

Article
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The Large Hadron Collider beauty (LHCb) experiment at CERN is undergoing an upgrade in preparation for the Run 3 data collection period at the Large Hadron Collider (LHC). As part of this upgrade, the trigger is moving to a full software implementation operating at the LHC bunch crossing rate. We present an evaluation of a CPU-based and a GPU-based...
Article
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The first study of the angular distribution of μ+μ− pairs produced in the forward rapidity region via the Drell-Yan reaction pp→γ*/Z+X→ℓ+ℓ−+X is presented, using data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb−1. The coefficients of the five leading terms in the angular...
Article
A precision measurement of the Z boson production cross-section at s√ = 13 TeV in the forward region is presented, using pp collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb−1. The production cross-section is measured using Z → μ+μ− events within the fiducial region defined as pseudorapidity 2.0 < η...
Article
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A precision measurement of the Z boson production cross-section at s = 13 TeV in the forward region is presented, using pp collision data collected by the LHCb detector, corresponding to an integrated luminosity of 5.1 fb−1. The production cross-section is measured using Z → μ+μ− events within the fiducial region defined as pseudorapidity 2.0 < η <...
Article
A bstract Coherent production of J/ψ mesons is studied in ultraperipheral lead-lead collisions at a nucleon-nucleon centre-of-mass energy of 5 TeV, using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of about 10 μb ⁻¹ . The J/ψ mesons are reconstructed in the dimuon final state and are required to have tra...
Article
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A bstract A data sample collected with the LHCb detector corresponding to an integrated luminosity of 9 fb − 1 is used to measure eleven CP violation observables in B ± → Dh ± decays, where h is either a kaon or a pion. The neutral D meson decay is reconstructed in the three-body final states: K ± π ∓ π ⁰ ; π ⁺ π − π ⁰ ; K ⁺ K − π ⁰ and the suppres...
Article
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The first full angular analysis and an updated measurement of the decay-rate CP asymmetry of the D^{0}→π^{+}π^{-}μ^{+}μ^{-} and D^{0}→K^{+}K^{-}μ^{+}μ^{-} decays are reported. The analysis uses proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. The dataset corresponds to an integrated lumin...
Article
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Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a st...
Article
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Conventional, hadronic matter consists of baryons and mesons made of three quarks and a quark–antiquark pair, respectively1,2. Here, we report the observation of a hadronic state containing four quarks in the Large Hadron Collider beauty experiment. This so-called tetraquark contains two charm quarks, a u¯ and a d¯ quark. This exotic state has a ma...
Article
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The first observation of the semileptonic b-baryon decay Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ}, with a significance of 6.1σ, is reported using a data sample corresponding to 3 fb^{-1} of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The τ^{-} lepton is reconstructed in the hadronic dec...
Article
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Tests of lepton universality in B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using...
Article
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A bstract A search for the decay B ⁰ → ϕμ ⁺ μ − is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9 fb − 1 . No evidence for the B ⁰ → ϕμ ⁺ μ − decay is found and an upper limit on the branching fraction, excluding the ϕ and ch...
Article
The centrality of heavy-ion collisions is directly related to the created medium in these interactions. A procedure to determine the centrality of collisions with the LHCb detector is implemented for lead-lead collisions at √ s NN = 5 TeV and lead-neon fixed-target collisions at √ s NN = 69 GeV. The energy deposits in the electromagnetic calorimete...
Article
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A bstract The $$ {\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+} $$ Ξ cc + + → Ξ c ′ + π + decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 . 4 fb − 1. The $$ {\varXi}_{cc}^{++}\to {\varXi}_c^{\prime +}{\pi}^{+} $$ Ξ cc + + → Ξ...
Article
A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200 $$\text {\,GeV\!/}c^2$$ \,GeV\!/ c 2 is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass v...
Article
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Two narrow resonant states are observed in the Λ_{b}^{0}K^{-}π^{+} mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb^{-1}. The minimal quark content of the Λ_{b}^{0}K^{-}π^{+} system indicates that these are excit...
Article
The production of prompt charged particles in proton-lead collisions and in proton-proton collisions at the nucleon-nucleon center-of-mass energy sqrt[s_{NN}]=5 TeV is studied at LHCb as a function of pseudorapidity (η) and transverse momentum (p_{T}) with respect to the proton beam direction. The nuclear modification factor for charged particles i...
Article
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A bstract A study of B ⁺ → J / ψηK ⁺ decays, followed by J / ψ → μ ⁺ μ − and η → γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb − 1 . The J / ψη mass spectrum is investigated for contributions from charmoni...
Article
Full-text available
A search is performed for massive long-lived particles (LLPs) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like boson with mass from 30 to 200\,GeV\!/c2 is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10\,GeV\!/c2 up...
Article
Searches for rare B s 0 $$ {B}_s^0 $$ and B0 decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. Direct decays and decays via light scalar and J/ψ resonances are considered. No evidence for the six decays searched for is found and upper limits...
Preprint
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The first study of the angular distribution of $\mu^+ \mu^-$ pairs produced in the forward rapidity region via the Drell-Yan reaction $pp \rightarrow \gamma^{*}/Z +X \rightarrow l^+ l^- + X$ is presented, using data collected with the LHCb detector at a centre-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.1 $\rm{fb}^{-1}$....
Article
Full-text available
A bstract Searches for rare $$ {B}_s^0 $$ B s 0 and B ⁰ decays into four muons are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb − 1 . Direct decays and decays via light scalar and J/ψ resonances are considered. No evidence for the six decays searched for is found and...
Article
Full-text available
The multihadron decays $$ {\Lambda}_b^0 $$ Λ b 0 → D + pπ−π− and $$ {\Lambda}_b^0 $$ Λ b 0 → D * + pπ−π− are observed in data corresponding to an integrated luminosity of 3 fb − 1 , collected in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV by the LHCb detector. Using the decay $$ {\Lambda}_b^0 $$ Λ b 0 → $$ {\Lambda}_c^{+} $$...
Article
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Events containing a Z boson and a charm jet are studied for the first time in the forward region of proton-proton collisions. The data sample used corresponds to an integrated luminosity of 6 fb^{-1} collected at a center-of-mass energy of 13 TeV with the LHCb detector. In events with a Z boson and a jet, the fraction of charm jets is determined in...
Preprint
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A measurement of the ratios of the effective decay widths of $D^0 \to \pi^-\pi^+$ and $D^0 \to K^-K^+$ decays over that of $D^0 \to K^-\pi^+$ decays is performed with the LHCb experiment using proton-proton collisions at a centre-of-mass energy of $13 \, \mathrm{TeV}$, corresponding to an integrated luminosity of $6 \, \mathrm{fb^{-1}}$. These obse...
Article
An amplitude analysis of flavor-untagged B_{s}^{0}→J/ψpp[over ¯] decays is performed using a sample of 797±31 decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 fb^{-1}. Evidence for a new structure in the J/ψp and J/ψp[over ¯] systems with...
Preprint
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The $\it{\Xi_{cc}^{++}\to \Xi_{c}^{'+}\pi^{+}}$ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of $13\mathrm{\,Te\kern -0.1em V}$, corresponding to an integrated luminosity of $5.4\,\mathrm{fb}^{-1}$. The $\it{\Xi_{cc}^{++}\to \Xi_{c}^{'+}\pi^{+}}$ decay is reconstructed partially, where...
Preprint
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A study of $B^+ \rightarrow J/\psi \eta K^+$ decays, followed by $J/\psi \rightarrow \mu^+ \mu^-$ and $\eta \rightarrow \gamma \gamma$, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{-1}$. The $J/psi\eta$ mas...
Article
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The identification of charm jets is achieved at LHCb for data collected in 2015–2018 using a method based on the properties of displaced vertices reconstructed and matched with jets. The performance of this method is determined using a dijet calibration dataset recorded by the LHCb detector and selected such that the jets are unbiased in quantities...
Article
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A bstract The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a centre-of-mass energy of $$ \sqrt{s} $$ s = 13 TeV. The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of 5...
Article
Branching fraction and effective lifetime measurements of the rare decay B_{s}^{0}→μ^{+}μ^{-} and searches for the decays B^{0}→μ^{+}μ^{-} and B_{s}^{0}→μ^{+}μ^{-}γ are reported using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a luminosity of 9 fb^{-1}. The branchin...
Preprint
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A search for the decay $B^0\to\phi\mu^+\mu^-$ is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9 fb$^{-1}$. No evidence for the $B^0\to \phi \mu^+ \mu^-$ decay is found and an upper limit on the branching fraction of $4.4 \tim...
Article
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A bstract The production cross-section of the χ c 1 (3872) state relative to the ψ (2 S ) meson is measured using proton-proton collision data collected with the LHCb experiment at centre-of-mass energies of $$ \sqrt{s} $$ s = 8 and 13 TeV, corresponding to integrated luminosities of 2.0 and 5.4 fb − 1 , respectively. The two mesons are reconstruct...
Article
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A bstract The first search for the rare radiative decay $$ {\Xi}_b^{-} $$ Ξ b − → Ξ − γ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb − 1 . The $$ {\Xi}_b^{-} $$ Ξ b − → Ξ − J/ψ channel is used as normalization. No $$ {\X...
Article
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A bstract Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb − 1 collected with the LHCb detector, seven decay modes of the $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ B c + meson into a J / ψ or ψ(2S) meson and three charged hadrons, kaons or pions, are studied. The decays $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ B c + → (ψ(2...
Article
Using proton-proton collision data, corresponding to an integrated luminosity of 9 fb−1 collected with the LHCb detector, seven decay modes of the B c + $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ meson into a J/ψ or ψ(2S) meson and three charged hadrons, kaons or pions, are studied. The decays B c + $$ {\mathrm{B}}_{\mathrm{c}}^{+} $$ → (ψ(2S) → J/ψπ+π−)π...
Preprint
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The first observation of the semileptonic $b$-baryon decay $ \Lambda_b^0 \rightarrow \Lambda_c^+ \tau^-\overline{\nu}_{\tau}$, with a significance of $6.1\,\sigma$, is reported using a data sample corresponding to 3 fb$^{-1}$ of integrated luminosity, collected by the LHCb experiment at centre-of-mass energies of 7 and 8~TeV at the LHC. The $\tau^-...
Article
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A bstract The W boson mass is measured using proton-proton collision data at $$ \sqrt{s} $$ s = 13 TeV corresponding to an integrated luminosity of 1.7 fb − 1 recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon q/p T distribution of a sample of W → μν decays and the ϕ * distribution of a sample of Z → μμ decays the W bo...
Article
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Mesons comprising a beauty quark and strange quark can oscillate between particle ( $${B}_{\mathrm{s}}^{0}$$ B s 0 ) and antiparticle ( $${\overline{B}}_{\mathrm{s}}^{0}$$ B ¯ s 0 ) flavour eigenstates, with a frequency given by the mass difference between heavy and light mass eigenstates, Δ m s . Here we present a measurement of Δ m s using $${B}_...
Article
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A study of Λb0 baryon decays to the DpK− final state is presented based on a proton-proton collision data sample corresponding to an integrated luminosity of 9 fb−1 collected with the LHCb detector. Two Λb0 decays are considered, Λb0→DpK− with D→K−π+ and D→K+π−, where D represents a superposition of D0 and D¯0 states. The latter process is expected...
Article
The Large Hadron Collider beauty (LHCb) experiment at CERN is undergoing an upgrade in preparation for the Run 3 data collection period at the Large Hadron Collider (LHC). As part of this upgrade, the trigger is moving to a full software implementation operating at the LHC bunch crossing rate. We present an evaluation of a CPU-based and a GPU-based...
Preprint
Full-text available
The first observations of $B^0\rightarrow\overline{D}^{*}(2007)^{0}K^{+}\pi^{-}$ and $B_s^0\rightarrow\overline{D}^{*}(2007)^{0}K^{-}\pi^{+}$ decays are presented, and their branching fractions relative to that of the $B^0\rightarrow\overline{D}^{*}(2007)^{0}\pi^{+}\pi^{-}$ decay are reported. These modes can potentially be used to investigate the...
Article
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A bstract A combination of measurements sensitive to the CP violation angle γ of the Cabibbo-Kobayashi-Maskawa unitarity triangle and to the charm mixing parameters that describe oscillations between D ⁰ and $$ \overline{D} $$ D ¯ ⁰ mesons is performed. Results from the charm and beauty sectors, based on data collected with the LHCb detector at CER...

Citations

... For its Z-boson counterpart, these coefficients are known up to next-to-next-to-leading order (NNLO) QCD [10,11] and NLO EW [7] accuracy. On the experimental side, several measurements of the Z-boson angular coefficients have been performed [12][13][14][15]. In general, good agreement has been found with theoretical predictions in the Standard Model. ...
... The differential production cross-sections as a function of transverse momentum are also measured separately and shown in Fig. 4. We also compared the results between experimental measurements and theoretical predictions [6][7][8][9][10][11][12][13][14][15]. Also, there are two previous results of coherent J/ψ production in PbPb UPCs by the LHCb [16] and ALICE [17] experiments. Compared with above measurements, we see this new result is slightly larger than the previous LHCb result by around 2σ and more compatible with the ALICE measurement. ...
... • [4]. Final states with net strangeness, which are produced through Cabibbo-favoured (CF) and doubly Cabibbo-suppressed (DCS) amplitudes, are of particular interest [5,6], and the modes D → K ± π ∓ and D → K ± π ∓ π 0 make important contributions to the LHCb average [7][8][9][10][11]. The channels D → K ± π ∓ π ∓ π ± belong to the same category, and are experimentally attractive due to their high branching fractions and having only charged particles in the final state. ...
... The two muons are required to have p T > 20 GeV, 2.0 < η(µ) < 4.5, and their invariant mass within the range 60 < M µµ < 120 GeV, as applied in Ref. [23,39]. The muons must satisfy the trackreconstruction and muon-identification criteria applied in Ref. [40]. Jet reconstruction is performed offline using a particle-flow algorithm [39], where the neutral and charged candidates are clustered using the anti-k T algorithm [41] as implemented in the FastJet package [42] with a distance parameter R of 0.5. ...
... Particles with an alternative quark content, known as "exotic" states, have been actively discussed since the birth of the QCD parton model, with the discussion revived by a series of more recent observations of numerous tetraquark and pentaquark candidates (see Refs. [20,21] for a review). Due to the closeness of their masses to known particle-pair thresholds, many of these states are likely to be hadronic molecules, albeit an interpretation of exotic states as compact multiquark structures is also possible. ...
... Again, these states appear very close to a two-hadron threshold. Indeed, this applies not only to the pentaquarks but also to tetraquarks, well-known candidates for which are X(3872) and T cc (3875) [12,13]. ...
... Despite the SM rate being dominated by long-distance dynamics, the effective GIM cancellation and (approximate) symmetries of the charm system allow to define various null-test observables related to angular distributions and CP violation, which have high discovery potential in the near future [101]. First measurements of such observables in D 0 → K + K − µ + µ − and D 0 → π + π − µ + µ − decays have been recently performed at LHCb [102]. The experimental precision has already reached 0.1 − 0.01 and, for the D 0 → K + K − µ + µ − results, the overall agreement with the SM is at the level of 2.7σ. ...
... In the past, this assumption was sufficiently accurate given the measured precision ofΓ(D 0 → K + K − ). However, a recent measurement ofΓ(D 0 → K + K − ) by the LHCb Collaboration [3] has significantly greater precision than previous measurements [4] and thus requires more careful consideration of Γ(D 0 → K − π + ). In particular, the effective decay width deviates from Γ due to D 0 mesons that oscillate to D 0 and subsequently decay to K − π + via a doubly Cabibbo-suppressed amplitude. ...
... Very recently, the LHCb collaboration has reported a measurement of the R Λ c ¼ ΓðΛ b →Λ c τ −ν τ Þ ΓðΛ b →Λ c μ −ν μ Þ ratio [66] and the experimental value R Λ c ¼ 0.242 AE 0.026 AE 0.040 AE 0.059 turns out to be in agreement, within errors, with the SM prediction R SM Λ c ¼ 0.332 AE 0.007 AE 0.007 [67]. The τ − lepton was reconstructed using the hadronic τ − → π − π þ π − ðπ 0 Þν τ decay, with the same technique used by the LHCb experiment to obtain R D Ã ¼ 0.291 AE 0.019 AE 0.026 AE 0.013 [12], also in agreement with the SM prediction. ...
... This is relevant since the charmonium modes are enhanced by O (10 4 ) with respect to the purely rare mode! Similar tensions between data and theory, albeit smaller statistical significance, have been measured in the analogous quantities of * 0 [4], * + and [5]. The Belle measurement of * [6] takes on the same role as for . ...