arXiv subjects

C. Adrover

Publications and source records attributed to C. Adrover.

At least 19 recordsLinked to original sources

arXiv2020

Measurement of psi(2S) meson production in pp collisions at sqrt(s)=7 TeV

The differential cross-section for the inclusive production of psi(2S) mesons in pp collisions at sqrt(s)=7 TeV has been measured with the LHCb detector. The data sample corresponds to an integrated luminosity of 36 pb-1. The psi(2S) mesons are reconstructed in the decay channels psi(2S) -> mu+ mu- and psi(2S) -> J/psi pi+ pi-, with the J/psi meson decaying into two muons. Results are presented both for promptly produced psi(2S) mesons and for those originating from b-hadron decays. In the kinematic range pT(psi(2S)) <= 16 GeV/c and 2 < y(psi(2S)) <= 4.5 we measure 1.44 +- 0.01 +- 0.12+0.2-0.4 mub for prompt psi(2S) production and 0.25 +- 0.01 +- 0.02 mub for psi(2S) from b-hadron decays, where the last uncertainty on the prompt cross-section is due to the unknown psi(2S) polarization. Recent QCD calculations are found to be in good agreement with our measurements. Combining the present result with the LHCb J/psi measurements we determine the inclusive branching fraction B(b -> psi(2S) X) = (2.73 +- 0.06 +- 0.16 +- 0.24) x 10^(-3), where the last uncertainty is due to the B(b -> J/psi X), B(J/psi -> mu+ mu-) and B(psi(2S) -> e+ e-) branching fraction uncertainties. All above results are corrected by an erratum included as an appendix.

hep-ex↗

arXiv2018

Measurement of the relative rate of prompt $χ_{c0}$, $χ_{c1}$ and $χ_{c2}$ production at $\sqrt{s}=7$TeV

Prompt production of charmonium $χ_{c0}$, $χ_{c1}$ and $χ_{c2}$ mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of $\sqrt{s}=7$TeV. The $χ_{c}$ mesons are identified through their decay to $J/ψγ$, with $J/ψ\toμ^+μ^-$ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of $1.0\mathrm{fb}^{-1}$ collected by the LHCb detector, is used to measure the relative prompt production rate of $χ_{c1}$ and $χ_{c2}$ in the rapidity range $2.0<y<4.5$ as a function of the $J/ψ$ transverse momentum from 3 to 20 GeV$/c$. First evidence for $χ_{c0}$ meson production at a high-energy hadron collider is also presented.

hep-ex↗

arXiv2015

Quantum numbers of the $X(3872)$ state and orbital angular momentum in its $ρ^0 Jψ$ decay

Angular correlations in $B^+\to X(3872) K^+$ decays, with $X(3872)\to ρ^0 J/ψ$, $ρ^0\toπ^+π^-$ and $J/ψ\toμ^+μ^-$, are used to measure orbital angular momentum contributions and to determine the $J^{PC}$ value of the $X(3872)$ meson. The data correspond to an integrated luminosity of 3.0 fb$^{-1}$ of proton-proton collisions collected with the LHCb detector. This determination, for the first time performed without assuming a value for the orbital angular momentum, confirms the quantum numbers to be $J^{PC}=1^{++}$. The $X(3872)$ is found to decay predominantly through S wave and an upper limit of $4\%$ at $95\%$ C.L. is set on the fraction of D wave.

hep-ex↗

arXiv2014

Measurement of D0-D0bar mixing parameters and search for CP violation using D0->K+pi- decays

Measurements of charm mixing parameters from the decay-time-dependent ratio of D0->K+pi- to D0->K-pi+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 fb^{-1} of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP) symmetry, the mixing parameters are determined to be x'^2=(5.5 +- 4.9)x10^{-5}, y'= (4.8 +- 1.0)x10^{-3}, and R_D=(3.568 +- 0.066)x10^{-3}. Allowing for CP violation, the mixing parameters are determined separately for D0 and D0bar mesons yielding A_D = (-0.7 +- 1.9)%, for the direct CP-violating asymmetry, and 0.75 < |q/p|< 1.24 at the 68.3% confidence level, where q and p are parameters that describe the mass eigenstates of the neutral charm mesons in terms of the flavor eigenstates. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.

hep-ex↗

arXiv2014

Measurements of $B_c^+$ production and mass with the $B_c^+ \to J/ψπ^+$ decay

Measurements of $B_c^+$ production and mass are performed with the decay mode $B_c^+ \to J/ψπ^+$ using 0.37 fb$^{-1}$ of data collected in $pp$ collisions at $\sqrt{s}=7$ TeV by the LHCb experiment. The ratio of the production cross-section times branching fraction between the $B_c^+ \to J/ψπ^+$ and the $B^+ \to J/ψK^+$ decays is measured to be $(0.68 \pm 0.10\,({\rm stat.}) \pm 0.03\,({\rm syst.}) \pm 0.05\,({\rm lifetime}))$% for $B_c^+$ and $B^+$ mesons with transverse momenta $p_{\rm T}>4 $GeV/$c$ and pseudorapidities $2.5<η<4.5$. The $B_c^+$ mass is directly measured to be $6273.7 \pm 1.3\,({\rm stat.}) \pm 1.6 \,({\rm syst.})$ MeV/$c^2$, and the measured mass difference with respect to the $B^+$ meson is $M(B_c^+)-M(B^+) = 994.6 \pm 1.3\,({\rm stat.}) \pm 0.6\,({\rm syst.})$ MeV/$c^2$.

hep-ex↗

arXiv2014

Study of $J/ψ$ production and cold nuclear matter effects in $p$Pb collisions at $\sqrt{s_{NN}}=5 \mathrm{TeV}$

The production of $J/ψ$ mesons with rapidity $1.5<y<4.0$ or $-5.0<y<-2.5$ and transverse momentum $p_\mathrm{T}<14 \mathrm{GeV}/c$ is studied with the LHCb detector in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{NN}}=5 \mathrm{TeV}$. The analysis is based on a data sample corresponding to an integrated luminosity of about $1.6 \mathrm{nb}^{-1}$. For the first time the nuclear modification factor and forward-backward production ratio are determined separately for prompt $J/ψ$ mesons and $J/ψ$ from $b$-hadron decays. Clear suppression of prompt $J/ψ$ production with respect to proton-proton collisions at large rapidity is observed, while the production of $J/ψ$ from $b$-hadron decays is less suppressed. These results show good agreement with available theoretical predictions. The measurement shows that cold nuclear matter effects are important for interpretations of the related quark-gluon plasma signatures in heavy-ion collisions.

nucl-ex↗

arXiv2014

Observation of double charm production involving open charm in pp collisions at $\sqrt{s}$=7 TeV

The production of $J/ψ$ mesons accompanied by open charm, and of pairs of open charm hadrons are observed in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of $355pb^{-1}$ collected with the LHCb detector. Model independent measurements of absolute cross-sections are given together with ratios to the measured $J/ψ$ and open charm cross-sections. The properties of these events are studied and compared to theoretical predictions.

hep-ex↗

arXiv2014

Searches for $B^{0}_{(s)} \rightarrow J/ψ p \overline{p}$ and $B^{+} \to J/ψ p \overline{p} π^{+}$ decays

The results of searches for $B^{0}_{(s)} \rightarrow J/ψ p \overline{p}$ and $B^{+} \to J/ψ p \overline{p} π^{+}$ decays are reported. The analysis is based on a data sample, corresponding to an integrated luminosity of 1.0 fb$^{-1}$ of $pp$ collisions, collected with the LHCb detector. An excess with 2.8$\,σ$ significance is seen for the decay $B^{0}_{s} \to J/ψ p \overline{p}$ and an upper limit on the branching fraction is set at the 90 % confidence level: ${\cal B}(B^{0}_{s} \to J/ψ p \overline{p}) < 4.8 \times 10^{-6}$, which is the first such limit. No significant signals are seen for $B^{0} \to J/ψ p \overline{p}$ and $B^{+} \to J/ψ p \overline{p} π^{+}$ decays, for which the corresponding limits are set: ${\cal{B}}(B^{0} \to J/ψ p \overline{p}) < 5.2 \times 10^{-7}$, which significantly improves the existing limit; and ${\cal{B}}(B^{+} \to J/ψ p \overline{p} π^{+}) < 5.0 \times 10^{-7}$, which is the first limit on this branching fraction.

hep-ex↗

arXiv2014

Measurements of indirect CP asymmetries in $D^0\to K^-K^+$ and $D^0\toπ^-π^+$ decays

A study of indirect CP violation in $D^0$ mesons through the determination of the parameter $A_Γ$ is presented using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected with the LHCb detector and recorded at the centre-of-mass energy of 7 TeV at the LHC. The parameter $A_Γ$ is the asymmetry of the effective lifetimes measured in decays of $D^0$ and $\bar{D}^0$ mesons to the CP eigenstates $K^-K^+$ and $π^-π^+$. Fits to the data sample yield $A_Γ(KK)=(-0.35\pm0.62\pm0.12)\times 10^{-3}$ and $A_Γ(ππ)=(0.33\pm1.06\pm0.14)\times 10^{-3}$, where the first uncertainties are statistical and the second systematic. The results represent the world's best measurements of these quantities. They show no difference in $A_Γ$ between the two final states and no indication of CP violation.

hep-ex↗

arXiv2014

Observation of B^0_(s) -> J/ψf_1(1285) decays and measurement of the f_1(1285) mixing angle

Decays of Bs and B0 mesons into J/ψπ+π-π+π- final states, produced in pp collisions at the LHC, are investigated using data corresponding to an integrated luminosity of 3/fb collected with the LHCb detector. B^0_(s) -> Jψf_1(1285) decays are seen for the first time, and the branching fractions are measured. Using these rates, the f_1(1285) mixing angle between strange and non-strange components of its wave function in the q-qbar structure model is determined to be \pm (24.0^{+3.1+0.6}_{-2.6-0.8}) degrees. Implications on the possible tetraquark nature of the f_1(1285) are discussed.

hep-ex↗

arXiv2014

Measurement of the flavour-specific CP-violating asymmetry $a_{\rm sl}^s$ in $B_s^0$ decays

The CP-violating asymmetry a_{sl}^s is studied using semileptonic decays of Bs and anti-Bs mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0/fb. The reconstructed final states are Ds^(+/-)μ^(-/+), with the Ds^(+/-) particle decaying in the ϕπ^(+/-) mode. The Ds^(+/-)μ^{-/+) yields are summed over Bs and anti-Bs initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain $a_{sl}^s$ = (-0.06 +/- 0.50 +/- 0.36)%, where the first uncertainty is statistical and the second systematic.

hep-ex↗

arXiv2014

Search for CP violation in the decay $D^+ \to π^-π^+π^+$

A search for CP violation in the phase space of the decay $D^+\toπ^-π^+π^+$ is reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The Dalitz plot distributions for $3.1\times 10^6$ $D^+$ and $D^-$ candidates are compared with binned and unbinned model-independent techniques. No evidence for CP violation is found.

hep-ex↗

arXiv2014

Search for the doubly charmed baryon Xi_cc^+

A search for the doubly charmed baryon Xi_cc^+ in the decay mode Xi_cc^+ -> Lambda_c^+ K^- pi^+ is performed with a data sample, corresponding to an integrated luminosity of 0.65/fb, of pp collisions recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300-3800 MeV/c^2. Upper limits at the 95% confidence level on the ratio of the Xi_cc^+ production cross-section times branching fraction to that of the Lambda_c^+, R, are given as a function of the Xi_cc^+ mass and lifetime. The largest upper limits range from R < 1.5 x 10^-2 for a lifetime of 100 fs to R < 3.9 x 10^-4 for a lifetime of 400 fs.

hep-ex↗

arXiv2013

Observation of the decay $B_s^0\to\bar{D}^0ϕ$

First observation of the decay Bs -> D0bar phi is reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb^-1, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The significance of the signal is 6.2 standard deviations. The branching fraction is measured relative to that of the decay Bs -> D0bar K*0bar to be 0.069 +/- 0.013 (stat) +/- 0.007 (syst). The first measurement of the ratio of branching fractions for the decays Bs -> D0bar K*0bar and Bd->D0bar K*0 is found to be 7.8 +/- 0.7 (stat) +/- 0.3 (syst) +/- 0.6 (f_s/f_d), where the last uncertainty is due to the ratio of the Bs and Bd fragmentation fractions.

hep-ex↗

arXiv2013

Search for the decay D0 to π+ π- μ+ μ-

A search for the D0 to π+ π- μ+ μ- decay, where the muon pair does not originate from a resonance, is performed using proton-proton collision data corresponding to an integrated luminosity of 1.0 fb-1 recorded by the LHCb experiment at a centre-of-mass energy of 7 TeV. No signal is observed and an upper limit on the relative branching fraction with respect to the resonant decay mode D0 to π+ π- ϕ(to μ+ μ-), under the assumption of a phase-space model, is found to be B(D0 to π+ π- mu+ mu-)/B(D0 to π+ π- ϕ(to μ+ μ-)) < 0.96 at the 90% confidence level. The upper limit on the absolute branching fraction is evaluated to be B(D0 to π+ π- μ+ μ-) < 5.5 x 10-7 at 90% confidence level. This is the most stringent to date.

hep-ex↗

arXiv2013

Measurement of the charge asymmetry in $B^{\pm}\rightarrow ϕK^{\pm}$ and search for $B^{\pm}\rightarrow ϕπ^{\pm}$ decays

The \CP-violating charge asymmetry in $B^{\pm}\rightarrow ϕK^{\pm}$ decays is measured in a sample of $pp$ collisions at 7 TeV centre-of-mass energy, corresponding to an integrated luminosity of 1.0 fb$^{-1}$ collected by the LHCb experiment. The result is $\mathcal{A}_{CP}(B^{\pm}\rightarrow ϕK^{\pm}) = \rm 0.022\pm 0.021 \pm 0.009$, where the first uncertainty is statistical and the second systematic. In addition, a search for the $B^{\pm}\rightarrow ϕπ^{\pm}$ decay mode is performed, using the $B^{\pm}\rightarrow ϕK^{\pm}$ decay rate for normalization. An upper limit on the branching fraction $\mathcal{B}(B^{\pm}\rightarrow ϕπ^{\pm})< 1.5\times 10^{-7}$ is set at 90% confidence level.

hep-ex↗

arXiv2013

Study of forward Z+jet production in pp collisions at $\sqrt{s} = 7$ TeV

A measurement of the $Z(\rightarrowμ^+μ^-)$+jet production cross-section in $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 7$ TeV is presented. The analysis is based on an integrated luminosity of $1.0\,\text{fb}^{-1}$ recorded by the LHCb experiment. Results are shown with two jet transverse momentum thresholds, 10 and 20 GeV, for both the overall cross-section within the fiducial volume, and for six differential cross-section measurements. The fiducial volume requires that both the jet and the muons from the Z boson decay are produced in the forward direction ($2.0<η<4.5$). The results show good agreement with theoretical predictions at the second-order expansion in the coupling of the strong interaction.

hep-ex↗

arXiv2013

Studies of beauty baryon decays to $D^0 p h^-$ and $Λ_c^+ h^-$ final states

Decays of beauty baryons to the $D^0 p h^-$ and $Λ_c^+ h^-$ final states (where $h$ indicates a pion or a kaon) are studied using a data sample of $pp$ collisions, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb detector. The Cabibbo-suppressed decays $Λ_b^0\to D^0 p K^-$ and $Λ_b^0\to Λ_c^+ K^-$ are observed and their branching fractions are measured with respect to the decays $Λ_b^0\to D^0 p π^-$ and $Λ_b^0\to Λ_c^+ π^-$. In addition, the first observation is reported of the decay of the neutral beauty-strange baryon $Ξ_b^0$ to the $D^0 p K^-$ final state, and a measurement of the $Ξ_b^0$ mass is performed. Evidence of the $Ξ_b^0\to Λ_c^+ K^-$ decay is also reported.

hep-ex↗